tag:blogger.com,1999:blog-84763481768719834332024-02-20T23:14:17.370+01:00ventilab internationalBringing ventilab.it worldwideUnknownnoreply@blogger.comBlogger14125tag:blogger.com,1999:blog-8476348176871983433.post-5725671286131064572023-06-04T14:08:00.037+02:002023-06-22T15:05:02.599+02:00 Mean arterial pressure and shock<p><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 12.6px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 16px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">Original post written on 4th June 2023 by Giuseppe Natalini</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: blue; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; text-align: center;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhXW0DHGVQ54hVlq8ty6zO-eOIBVTO4qN4m_63zVIYTevp11axAVEqqVOOZiGgz7N6HXQ5Pwmo7WPDNcPQp66tTYDR07VZz5dlUfF0DGnD1unndjT60ld5QjNvA3oYXMa9MuZtQIq10dkj74D3l7bNRnXEY0QphQPUafxh8GkCKNovvjN1bRCv4LQmkOtI" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="178" data-original-width="320" height="178" src="https://blogger.googleusercontent.com/img/a/AVvXsEhXW0DHGVQ54hVlq8ty6zO-eOIBVTO4qN4m_63zVIYTevp11axAVEqqVOOZiGgz7N6HXQ5Pwmo7WPDNcPQp66tTYDR07VZz5dlUfF0DGnD1unndjT60ld5QjNvA3oYXMa9MuZtQIq10dkj74D3l7bNRnXEY0QphQPUafxh8GkCKNovvjN1bRCv4LQmkOtI" width="320" /></a></div><br /><br /><p></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">Mario and Pippo have an <b>infection</b> which also causes <b>hypotension</b>. After an initial <b>fluid</b> administration, they present as follows:</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">-Mario, <i>45 years old, no chronic disease</i>. Blood pressure: 78/48 mmHg (<b>mean arterial pressure 58 mmHg</b>).</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">-Pippo,<i> 75 years old, receiving treatment for arterial hypertension</i>. Blood pressure: 95/50 mmHg (<b>mean arterial pressure 67 mmHg</b>).</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">Based on this limited information, let's try to ask a couple of questions:</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">1) Are these data sufficient to decide whether to intervene to increase Mario and/or Pippo's blood pressure, and if so, by how much?</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">2) Do you think there are other data to consider in order to answer the question?</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Before attempting to answer these questions, let's consider both data from clinical studies on arterial pressure in septic shock and the </p><div class="separator" style="clear: both; text-align: center;"><br /></div><br />physiological basis of arterial pressure.<p></p>
<p style="background-color: white; color: #1e00fd; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>What do clinical studies say?</b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The latest edition of the Surviving Sepsis Campaign <b>guidelines</b> recommends that, in adults with <b>septic shock</b>, <b>mean arterial pressure </b>should initially be <b>targeted</b> to reach <b>65 mmHg</b> (compared to higher targets) (1).</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">However, when considering clinical studies in patients with septic shock as a whole, they do not support the idea that there is a threshold value of mean arterial pressure to be reached. </p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">It should be noted that the clinical and physiological impact of <b>mean arterial pressure values below 60-65 mmHg</b> <b>has not been studied</b>. Therefore, the value of 65 mmHg should be considered as the lowest of the values which were studied.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">When <b>65 mmHg of mean arterial pressure</b> is <b>compared </b>to <b>higher values</b> (mostly between 75 and 85 mmHg), the studies reach <b>conflicting conclusions</b>: in some cases, there are no differences in outcomes, in others, it may be more favorable to maintain lower values, and in others, higher levels of pressure seem to be more favorable (2-8).</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Considering these conflicting results as a whole, one should consider the idea that <b>mean arterial pressure </b>is probably a <b>not so important target</b> for cardiovascular support of patients with sepsis.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: #1e00fd; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>Arterial pressure, physiological aspects.</b></p>
<p style="background-color: white; color: #343434; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><i>Arterial pressure during the cardiac cycle.</i></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">A premise: in our reasoning, we will completely ignore the retrograde reflection of the pressure wave, which is a very important aspect in the formation of the arterial pressure wave. However, omitting it does not alter the meaning of the reasoning we will present.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><b>Arterial pressure</b> is the result of the <b>stretching </b>of the elastic fibers of the <b>arterial wall </b>caused<b> </b>by the <b>volume of blood </b>contained within<b>.</b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The <b>volume of blood </b>contained in an <b>artery </b>at any given instant is determined by the <b>dynamic equilibrium </b>between<b> two flows: </b>one coming from the<b> heart </b>and one going towards the<b> peripheral circulation.</b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">During <b>systole, </b>these two flows are present <b>simultaneously, </b>meaning that blood arrives from the heart and blood exits towards the peripheral circulation at the same time. <b>In the initial phase of systole</b> (red area in Fig. 1), <b>pressure increases </b>because the <b>volume of blood </b>in the artery <b>increases, </b>meaning that<b> incoming flow is greater than outgoing flow.</b></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><b><br /></b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 22px;"><b></b><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 22px;"><b></b></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgWZXyIfiLg4QpFpLqpp20xNPkRQhuBmDHSky4tJSsyUKlhAWg6xjnERfXtpO6RoC9YX_zkIiDMB09Pwow9fQVZplfVloZ-e8irDCJORDtJJ9ge2DJsHM0Llw8w4OMCH5gSlMU8xL__HbGsXh36PxL8JUODoKmHguTA0icOv-gWaTTtEhs53h-wkovS2HE" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="356" data-original-width="640" height="377" src="https://blogger.googleusercontent.com/img/a/AVvXsEgWZXyIfiLg4QpFpLqpp20xNPkRQhuBmDHSky4tJSsyUKlhAWg6xjnERfXtpO6RoC9YX_zkIiDMB09Pwow9fQVZplfVloZ-e8irDCJORDtJJ9ge2DJsHM0Llw8w4OMCH5gSlMU8xL__HbGsXh36PxL8JUODoKmHguTA0icOv-gWaTTtEhs53h-wkovS2HE=w677-h377" width="677" /></a></div><br /><p></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;">Figure 1 </p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">This increase in volume is accommodated by the systolic expansion of the artery, which reaches its maximum at the systolic peak (Figure 2).</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;"> </p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px; text-align: center;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEi_e1MIC5HFTjzV1ichJSVa6Fh_7uZ81O4Wisr7XZFP15mp-g-X2eavq1NqsBqOTFDPmpTfWIIkIuyRC78HEdCSn83R8QyGzT2n-qUktS4SDignRb8tcCfWtiggO0qjl0hDEjdFbJRwZrjB8pe5mludv6baQuGSmCx20Uz1Nr7xjhWISmOAasWiSw_jN60" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="326" data-original-width="628" height="293" src="https://blogger.googleusercontent.com/img/a/AVvXsEi_e1MIC5HFTjzV1ichJSVa6Fh_7uZ81O4Wisr7XZFP15mp-g-X2eavq1NqsBqOTFDPmpTfWIIkIuyRC78HEdCSn83R8QyGzT2n-qUktS4SDignRb8tcCfWtiggO0qjl0hDEjdFbJRwZrjB8pe5mludv6baQuGSmCx20Uz1Nr7xjhWISmOAasWiSw_jN60=w565-h293" width="565" /></a></div><br /><p></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px; text-align: center;">Figure 2</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">As systole progresses beyond the systolic peak, the <b>pressure decreases</b>, indicating that the <b>volume </b>of blood in the artery <b>decreases</b>. <b>The inflow continues, but now the outflow exceeds it</b> (gray area in Figure 1).</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">The <b>dicrotic notch</b> marks the transition from <b>systole to diastole</b> (lilac area in Figure 1): the <b>closing of the aortic valve stops the inflow to the artery</b>, and <b>only the outflow remains</b>. Therefore, <b>diastolic arterial pressure</b> expresses the <b>interaction between the arterial vessel and the peripheral circulation</b>, unlike systolic arterial pressure, which also includes coupling with the cardiac pump.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The<b> diastolic flow</b> from the artery to the peripheral circulation is <b>propelled by the elastic recoil </b>of the arterial wall against the volume of blood contained within it (Figure 3) and <b>hindered by downstream pressure</b>. </p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEg9ED8KrHHPht7iMIGpr8-KXSYIyGOsFVdgUwSSLAciEmFHewGahR71z2gxd-rFe9zlhkJQy_ZWdns8gRvp0iF2-G0KRy3xuoosxIidP9uyDQIjae44tH3LQ6wIp_zmO7WX339TAMEEjFT6Kz9vFmrcygn_eIWx_Ak0voh7blpnih1MzxWPkFNExy1hq4Y" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="326" data-original-width="614" height="297" src="https://blogger.googleusercontent.com/img/a/AVvXsEg9ED8KrHHPht7iMIGpr8-KXSYIyGOsFVdgUwSSLAciEmFHewGahR71z2gxd-rFe9zlhkJQy_ZWdns8gRvp0iF2-G0KRy3xuoosxIidP9uyDQIjae44tH3LQ6wIp_zmO7WX339TAMEEjFT6Kz9vFmrcygn_eIWx_Ak0voh7blpnih1MzxWPkFNExy1hq4Y=w559-h297" width="559" /></a></div><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;">Figure 3</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Let's now try to understand the meaning of this downstream pressure, which is also crucial for the correct interpretation of mean arterial pressure.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Usually, diastole lasts less than 1 second and is interrupted by the next systole. Let's imagine that we could extend diastole for several seconds, allowing the complete outflow of arterial blood towards the capillary circulation and achieving a complete cessation of arterial flow. How low do we think arterial pressure could drop during this hypothetical extended diastole? It has been theoretically and experimentally demonstrated that the <b>reduction in diastolic arterial pressure stops </b>at<b> pressure values </b>which are<b> significantly higher than</b> those of <b>venous pressures</b>, typically around <b>25-50 mmHg</b> (9-11). This is considered a <b>critical closing pressure</b>,<b> below which the flow ceases</b>, and consequently, tissue perfusion is halted.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">At this point, it becomes clear that the <b>entire portion of diastolic arterial pressure below the critical closing pressure should not be considered as perfusion pressure</b>.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Furthermore, <b>diastolic arterial pressure </b>is <b>dependent </b>on <b>peripheral vascular resistances</b>, primarily located at the pre-capillary arteriolar level. As a result, <b>diastolic arterial pressure</b> can decrease slowly (and therefore remain <b>elevated</b>) due to arteriolar <b>vasoconstriction</b>, which <b>hinders </b>blood outflow (and<b> tissue perfusion</b>). <b>Alternatively</b>, it can decrease rapidly (and therefore become immediately <b>low</b>) if there is <b>vasodilation</b>, <b>facilitating perfusion</b> and blood <b>flow </b>towards tissues.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">It is therefore evident that<b> only a portion of the diastolic arterial pressure</b> (that <b>above</b> the <b>critical closing pressure</b>) <b>generates flow</b>, and this <b>portion of diastolic arterial pressure can </b>even <b>have </b>an <b>inverse relationship with flow itself</b>.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Unlike diastolic pressure, <b>pulse pressure</b> (the systolic pressure increment) is directly <b>correlated</b> to <b>stroke volume</b> and, therefore, to cardiac output and perfusion. The extent of the correlation between pulse pressure and stroke volume depends, obviously, on arterial compliance. For example, the same stroke volume may generate a pulse pressure that increases in parallel with age.</p>
<p style="background-color: white; color: #343434; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><i>Mean arterial pressure</i></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;"><b></b><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">In Figure 4, a "normal" arterial pressure curve is depicted, with a systolic pressure (SBP) of 122 mmHg, and a diastolic pressure (DBP) of 80 mmHg. The pulse pressure (PP) is 42 mmHg.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEi0lsnu14ykpgnA3sS7nr2W13sRGVeMLD4Kb9UVy-tFSXpchqqpdwMcfm2Ump8kxg5K3J8Oxv160JjBBifOULbyBcnY8m-I9uIy5x_BXV1MTdVZtWdlIxGaOqZUmnr5QSlLo6I9oelW5tMI1Swx7igyTDX0uCdIaQ5YE9X5jACRgl_nBvrsuXDpsKvbvJY" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="360" data-original-width="639" height="364" src="https://blogger.googleusercontent.com/img/a/AVvXsEi0lsnu14ykpgnA3sS7nr2W13sRGVeMLD4Kb9UVy-tFSXpchqqpdwMcfm2Ump8kxg5K3J8Oxv160JjBBifOULbyBcnY8m-I9uIy5x_BXV1MTdVZtWdlIxGaOqZUmnr5QSlLo6I9oelW5tMI1Swx7igyTDX0uCdIaQ5YE9X5jACRgl_nBvrsuXDpsKvbvJY=w648-h364" width="648" /></a></div><p></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;">Figure 4</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>Mean arterial pressure </b>is the <b>average</b> pressure during a <b>complete cardiac cycle (systole and diastole</b>). It is calculated by dividing the area under the pressure curve during one cardiac cycle by the duration of the cycle (red area, equivalent to the gray area in Figure 4). When blood pressure measurements are taken frequently (e.g., during invasive blood pressure monitoring with at least 100 samples per second), mean arterial pressure can be approximated well by the arithmetic mean of all the measured pressure values throughout the cardiac cycle.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">Mean arterial pressure (MAP) can also be estimated (approximately) using the equation:</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Times; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 28.1px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; text-align: center;">MAP=SBP+1/3<span style="font-family: Symbol; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 28.1px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;">⋅</span>PP (eq. 1) </p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">In the example shown in Figure 1, the calculated MAP is 94 mmHg.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">As can be seen both from the graphical evaluation in Figure 4 and from Equation 1,<b> mean arterial pressure</b> is <b>primarily determined </b>by <b>diastolic arterial pressure</b> and to a lesser extent by pulse pressure. In our example, out of the 94 mmHg of mean pressure, 85% is due to diastolic pressure (80 mmHg) and only 15% to pulse pressure (the remaining 14 mmHg).</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><b>Mean arterial pressure combines diastolic and pulse pressure</b>, which, however, have <b>very different</b> physiological and hemodynamic <b>meanings</b>. Within MAP, the <b>diastolic component, </b>which is the part of arterial pressure that is <b>less correlated with tissue perfusion</b>,<b> carries more weight</b>.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Given these considerations, it is not surprising that clinical studies have not led to a clear target for mean arterial pressure in the treatment of patients with shock.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: #1e00fd; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>Let's get back to Mario and Pippo...</b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Now we can address the first of our two initial questions, which asks whether and how we should modify the blood pressure for Mario (a healthy forty-five-year-old with a mean arterial pressure of 58 mmHg) and/or Pippo (an hypertensive seventy-five-year-old with a mean arterial pressure of 67 mmHg). The answer is disappointingly simple: we don't have enough data to make a decision. <b>Blood pressure </b>is an <b>easily measurable</b> parameter but of <b>limited clinical utility </b>in a patient with <b>shock</b>. The blood pressure of both Mario and Pippo could be sufficient for organ and tissue perfusion, or it could be inadequate.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">We necessarily need additional information to decide whether and what actions should be taken. This would be the second question to answer, but this post has already become quite lengthy. It's worth taking a break and continuing in the next post.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b><i>Conclusions</i></b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 23.1px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 28px;"><b></b><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Let's summarize the main concepts discussed in today's post:</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-Achieving a <b>mean arterial pressure of 65 mmHg</b> is considered a treatment target for patients with hypotension secondary to infection, but the literature presents <b>conflicting conclusions</b> on this matter.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-<b>Pulse pressure</b> is also influenced by <b>stroke volume</b>, which forms the basis of <b>cardiac output</b> and is therefore an important factor in <b>peripheral perfusion</b>.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-<b>Diastolic blood pressure</b> is <b>dependent on peripheral vascular resistance</b> and the <b>critical closing pressure</b>, which<b> limit the flow towards tissues</b>.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-In calculating <b>mean arterial pressure</b>, the <b>weight of diastolic pressure</b> is <b>predominant</b> compared to pulse pressure. Since <b>perfusion </b>(cardiac output) is influenced by <b>pulse pressure</b> and not diastolic pressure, it is reasonable to consider <b>mean arterial pressure</b> as an <b>unreliable indicator of perfusion</b>. This understanding sheds light on the inconclusive results of clinical studies in search of the "right" mean arterial pressure.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-To assess <b>hemodynamic adequacy</b> in patients with shock, it is <b>essential </b>to consider <b>additional perfusion indices</b> alongside <b>blood pressure</b> measurements.</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">As always, warm regards and a smile to all of v<i>entilab</i>‘s friends<i>.</i></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 23.1px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 28px;"><b></b><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>References:</b></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">1) Evans L, Rhodes A, Alhazzani W, et al.: Surviving sepsis campaign: international guidelines for management of sepsis and septic shock 2021. Intensive Care Med 2021; 47:1181–1247</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">2) LeDoux D, Astiz ME, Carpati CM, et al.: Effects of perfusion pressure on tissue perfusion in septic shock: Crit Care Med 2000; 28:2729–2732</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">3) Bourgoin A, Leone M, Delmas A, et al.: Increasing mean arterial pressure in patients with septic shock: Effects on oxygen variables and renal function: Crit Care Med 2005; 33:780–786</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">4) Thooft A, Favory R, Salgado D, et al.: Effects of changes in arterial pressure on organ perfusion during septic shock. Crit Care 2011; 15:R222</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">5) Asfar P, Meziani F, Hamel J-F, et al.: High versus Low Blood-Pressure Target in Patients with Septic Shock. N Eng J Med 2014; 370:1583–1593</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">6) Lamontagne F, Meade MO, Hébert PC, et al.: Higher versus lower blood pressure targets for vasopressor therapy in shock: a multicentre pilot randomized controlled trial. Intensive Care Medicine 2016; 42:542–550</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">7) Lamontagne F, Richards-Belle A, Thomas K, et al.: Effect of reduced exposure to vasopressors on 90-day mortality in older critically ill patients with vasodilatory hypotension: a randomized clinical trial. JAMA 2020; 323:938</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">8) Maheshwari K, Nathanson BH, Munson SH, et al.: The relationship between ICU hypotension and in-hospital mortality and morbidity in septic patients. Intensive Care Med 2018; 44:857–867</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">9) Permutt S, Riley RL: Hemodynamics of collapsible vessels with tone: the vascular waterfall. J Appl Physiol 1963; 18:924–932</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">10) Kottenberg-Assenmacher E, Aleksic I, Eckholt M, et al.: Critical closing pressure as the arterial downstream pressure with the heart beating and during circulatory arrest: Anesthesiology 2009; 110:370–379</p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">11) Maas JJ, de Wilde RB, Aarts LP, et al.: Determination of vascular waterfall phenomenon by bedside measurement of mean systemic filling pressure and critical closing pressure in the intensive care unit: Anesth Analg 2012; 114:803–810</p><div><br /></div>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-20576458998177251172023-04-05T15:34:00.004+02:002023-06-15T17:37:23.815+02:00Flow Index: A Unique Tool for Optimizing Inspiratory Support<p> </p>
<p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">Original post written on 5th April 2023 by Giuseppe Natalini</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 12.6px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 16px;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEjVxyW4skEKSPGVCtR1nKOkU8uhjCvhBMbnXkM7NEi_1GtKnZMtFRFIkksag9cQtXr6fWQiXEvvtuei9HavP0chvlj_RbHuXVk7lMvKccl_T21CJwnNgiEU1YCi_Tea_AQtV_VkozWVL6pccSaTP_tSvvhl0ZEnbtexbJ58j91xabXYfo_m_inOaL1-" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="450" data-original-width="690" height="209" src="https://blogger.googleusercontent.com/img/a/AVvXsEjVxyW4skEKSPGVCtR1nKOkU8uhjCvhBMbnXkM7NEi_1GtKnZMtFRFIkksag9cQtXr6fWQiXEvvtuei9HavP0chvlj_RbHuXVk7lMvKccl_T21CJwnNgiEU1YCi_Tea_AQtV_VkozWVL6pccSaTP_tSvvhl0ZEnbtexbJ58j91xabXYfo_m_inOaL1-" width="320" /></a></div><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px;">During mechanical ventilation, <b>inspiratory support</b> should be <b>modulated </b>to maintain optimal<b> activity of the inspiratory muscles</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 16px;"><b>Respiratory muscle activity </b>can be measured as the <b>pressure </b>they develop during <b>inspiration </b>(<b>Pressure-time product</b>,<b> PTP</b>, see also this post from <span style="color: #0000e9; text-decoration: underline;"><a href="http://www.ventilab.it/2016/10/il-lavoro-respiratorio.html" target="_blank">30/10/2016</a></span>, English translation not yet available) (Figure 1), which is the <b>sum of:</b> a) the <b>pressure</b> generated by the respiratory muscles to <b>expand the lungs</b>, expressed by the reduction in esophageal pressure during inspiration (PTP<span style="font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 10px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><sub>L</sub></span>, hatched area); b) the <b>pressure</b> required to expand the<b> rib cage</b> (PTP<span style="font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 10px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><sub>CW</sub></span>, dotted area), which is calculated at each moment of inspiration as the product of rib cage elastance (calculated from esophageal pressure) and inspired volume.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEitGS-UwC7gGy8TNnOwytJmKjuqd-lRf9DPWEh3A9FFaTBHf16QIUO2GwEewkFpzRbSs-h-5sjHLuOTEbFA5SWF3ze3QwfTYVMTUFcu_kIBrdtnIDyTkbSzUf2bbd_dSBhMgG5RMY4TebfsRFVUhh3FhitBU729_UgCDroIP8He8Ou_y8GgB5igKXJU" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="697" data-original-width="718" height="400" src="https://blogger.googleusercontent.com/img/a/AVvXsEitGS-UwC7gGy8TNnOwytJmKjuqd-lRf9DPWEh3A9FFaTBHf16QIUO2GwEewkFpzRbSs-h-5sjHLuOTEbFA5SWF3ze3QwfTYVMTUFcu_kIBrdtnIDyTkbSzUf2bbd_dSBhMgG5RMY4TebfsRFVUhh3FhitBU729_UgCDroIP8He8Ou_y8GgB5igKXJU=w411-h400" width="411" /></a></div><br /><br /><div><div style="text-align: center;">Figure 1</div><p style="background-color: white; color: #2a3140; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 16px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 20px;"><br /></p><p style="background-color: white; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 16px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 20px;"><span style="color: #2a3140;">The sole function of </span><b style="color: #2a3140;">inspiratory support </b><span style="color: #2a3140;">is to </span><b style="color: #2a3140;">support the activity of the respiratory muscles</b><span style="color: #2a3140;">, which is </span><b style="color: #2a3140;">measured</b><span style="color: #2a3140;"> by </span><b style="color: #2a3140;">esophageal pressure</b><span style="color: #2a3140;">. With that being said, it would seem obvious that the most important pressure to measure in ventilated patients should be esophageal pressure... In </span><b style="color: #2a3140;">clinical practice</b><span style="color: #2a3140;">, esophageal pressure is rarely measured, and the </span><b style="color: #2a3140;">appropriateness</b><span style="color: #2a3140;"> of </span><b style="color: #2a3140;">inspiratory support</b><span style="color: #2a3140;"> is mainly determined by evaluating </span><b style="color: #2a3140;">respiratory rate and tidal volume</b><span style="color: #2a3140;">, as well as </span><b style="color: #2a3140;">indirect indicators of respiratory muscle activity </b><span style="color: #2a3140;">such as </span><b style="color: #2a3140;">P</b><span style="color: #2a3140; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 10px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><b><sub>0.1</sub></b></span><span style="color: #2a3140;"> (</span><a href="http://www.ventilab.net/2022/01/p01-respiratory-drive-and-inspiratory.html" style="color: #2a3140;"><span style="color: #520001;">post dated 27/06/21</span></a><span style="color: #2a3140;">), </span><b style="color: #2a3140;">PMI </b><span style="color: #2a3140;">(</span><span style="color: #520001;"><a href="http://www.ventilab.it/2016/05/pmi-pressure-muscindex-come-stimare.html">post dated 08/05/2016</a>, </span><span>English translation not yet available</span><span style="color: #2a3140;">), </span><b style="color: #2a3140;">dP</b><span style="color: #2a3140; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 10px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><b><sub>occ</sub></b></span><span style="color: #2a3140;"> (1), and </span><b style="color: #2a3140;">Flow Index</b><span style="color: #2a3140;">, the topic of this post.</span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 24px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>The Flow Index.</b></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 16px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The <b>Flow Index</b> is a dimensionless <b>number</b> that describes the <b>shape </b>of the <b>inspiratory flow curve</b> <b>from its peak to the point where cycling</b> <b>occurs </b>(2). If this portion of the <b>flow curve</b> has an<b> upward concavity</b>, the <b>Flow Index</b> assumes a value <b><1</b> (the smaller the value, the more pronounced the upward concavity), if it <b>decreases linearly</b>, the <b>Flow Index is 1</b>, and if the flow curve has a<b> downward concavity</b>, the Flow Index is<b> >1</b> (the greater the value, the more pronounced the downward concavity) (Figure 2).</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 16px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 16px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><br /></p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgZp0qQ2qCZEglN_S4ppeAExW9i1_eDotEvWtoPkmg3OCKL8m8bFMlbBA2bP3lk5s-128h8NUW8nA-B8KHv5nTxIMGEboLSb-bMjYg_SZgiDABGX4QJuvtSRJ46AoVrtuaaD7h4J3TO-p8X08vCHWkC6WeTNsqlsrEW2cAmRtbCCi6y_-bcEka7jzrp" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="500" data-original-width="1000" height="238" src="https://blogger.googleusercontent.com/img/a/AVvXsEgZp0qQ2qCZEglN_S4ppeAExW9i1_eDotEvWtoPkmg3OCKL8m8bFMlbBA2bP3lk5s-128h8NUW8nA-B8KHv5nTxIMGEboLSb-bMjYg_SZgiDABGX4QJuvtSRJ46AoVrtuaaD7h4J3TO-p8X08vCHWkC6WeTNsqlsrEW2cAmRtbCCi6y_-bcEka7jzrp=w476-h238" width="476" /></a></div><br /><span face="-webkit-standard" style="caret-color: rgb(0, 0, 0); color: black; font-size: medium; text-align: left;">Figure 2</span></div><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The Flow Index stems from the understanding that during <b>pressure-controlled ventilation, inspiratory flow decreases if the patient is passive</b>, while the <b>reduction in alveolar pressure</b> due to r<b>espiratory muscle activity </b>produces a <b>downward concavity</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">A picture is worth a thousand words: in Figure 3, we can see how the flow profile changes with increasing levels of pressure support (PS).</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEilJdQFwYPjTGA-zu4tYBQ0P6Kcg3JkDCliLhrouddbBubUalxx22tnfB-KO9P0BNJ-0NcmhtjbcLBU6jRvw6ZAzB_skCAwdQ9rpqHtoCbgdzUWShv76_JnXCFklGrjQakAWPXSEjlFfwUwgkRJAG-bmZmQ84CsoxQh6t1Mbn49UDuaPE3TH89AgjOe" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="564" data-original-width="887" height="313" src="https://blogger.googleusercontent.com/img/a/AVvXsEilJdQFwYPjTGA-zu4tYBQ0P6Kcg3JkDCliLhrouddbBubUalxx22tnfB-KO9P0BNJ-0NcmhtjbcLBU6jRvw6ZAzB_skCAwdQ9rpqHtoCbgdzUWShv76_JnXCFklGrjQakAWPXSEjlFfwUwgkRJAG-bmZmQ84CsoxQh6t1Mbn49UDuaPE3TH89AgjOe=w493-h313" width="493" /></a></div><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;"><span face="-webkit-standard" style="caret-color: rgb(0, 0, 0); color: black; font-size: medium; text-align: left;">Figure 3</span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">With a PS of 20, the patient, after the activation of the inspiratory trigger, becomes passive throughout inspiration, and the flow decreases. As inspiratory support is reduced (moving from right to left in Figure 3), inspiratory activity becomes progressively more intense, and concurrently, the flow curve assumes a morphology with an increasingly pronounced downward concavity. Consequently, <b>as respiratory muscle activity increases, the Flow Index becomes higher</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">This concept is not at all new for those who have participated in our ventilation courses or follow <i>ventilab</i>: evaluating respiratory muscle activity from the flow curve has already been proposed in our first mechanical ventilation course in 2007. It was the subject of one of the first posts I wrote on <i>ventilab</i> (dated <span style="color: #520001;"><a href="https://www.ventilab.it/2010/03/monitoraggio-grafico-della-ventilazione.html">25/03/2010</a>, </span>English translation not yet available), and it is an important part of the RESPIRE method (particularly its "I" letter), presented in its first version in the <span style="color: #520001;"><a href="http://www.ventilab.it/2017/08/monitoraggio-grafico-della-ventilazione.html">post dated 20/08/2017</a> (</span>English translation not yet available).</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The<b> Flow Index</b> has simply <b>transformed</b> the <b>subjective and qualitative evaluation</b> of the flow curve into an <b>objective and quantitative measurement</b>. Studies on the <b>Flow Index </b>(2-4) have demonstrated two important things:</p><ol>
<li style="color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><span style="background-color: white;">The <b>morphology of the inspiratory flow curve</b> during <b>pressure-controlled ventilation</b> is <b>effective</b> for a <b>non-invasive </b>and <b>continuous assessment of respiratory muscle activity</b>. Before the Flow Index, we had only the theoretical rationale for this approach (which was already significant), but now experimental evidence has also been added to it.</span></li>
<li style="color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><span style="background-color: white;"><b>Assessing respiratory rate and tidal volume </b>to gain an understanding of inspiratory effort <b>cannot replace</b> the information provided by the <b>Flow Index</b>; at most, it should complement the Flow Index. In fact, the strong association between the Flow Index and inspiratory effort remains even when adjusting for tidal volume and respiratory rate.</span></li>
</ol><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>How to calculate the Flow Index</b></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">A brief technical note. The <b>Flow Index</b> examines the <b>portion of flow following the peak and preceding cycling (Figure 4) </b>and applies the same equation used on airway pressure to calculate the stress index: </p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 22px; text-align: center;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; text-align: center;">flow=a+b<span style="font-family: "Apple Symbols"; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;">⋅</span>time<span style="font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 12px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><sup>c</sup></span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The parameter c, the exponent of time, is the Flow Index. Here are two examples:</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEiLfl-OFkelYcqHrUiDOoajm7VXiNnvvpqwCwSzzAMw5vvnSBXEQ0ucByMxqP9o5q1Jo0vuJTXhKrdzK4-vCO5YufJ_ZFfDoxg_48UKBhYX6-WdRNSE8_KW8Rga0ECBll3CMW0xP7cUyf8bMbXyt_YU3ZuEayckol7kumBC5TkZ1e92BsTHGj4gkz8I" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="494" data-original-width="745" height="350" src="https://blogger.googleusercontent.com/img/a/AVvXsEiLfl-OFkelYcqHrUiDOoajm7VXiNnvvpqwCwSzzAMw5vvnSBXEQ0ucByMxqP9o5q1Jo0vuJTXhKrdzK4-vCO5YufJ_ZFfDoxg_48UKBhYX6-WdRNSE8_KW8Rga0ECBll3CMW0xP7cUyf8bMbXyt_YU3ZuEayckol7kumBC5TkZ1e92BsTHGj4gkz8I=w528-h350" width="528" /></a></div><br /><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;"><span face="-webkit-standard" style="caret-color: rgb(0, 0, 0); color: black; font-size: medium; text-align: left;">Figure 4</span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Currently, the Flow Index can only be calculated through a mathematical analysis procedure of flow data. However, in the future, it could easily be automatically calculated by mechanical ventilators if further validations are added to the existing studies confirming its ability to identify over-assisted or under-assisted patients (3,4). In the meantime, the <b>qualitative analysis of the flow curve remains highly applicable in clinical practice</b>, <b>allowing for the easy visual identification of patients with high or reduced inspiratory activity</b>, i.e., <b>with or without a downward concavity in the flow curve</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 24px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;"><b>The uniqueness of the Flow Index compared to other estimates of respiratory muscle activity.</b></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px; min-height: 19px;"><b></b><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">As mentioned earlier, in addition to the Flow Index, there are other indicators of inspiratory muscle activity. However, there is an important difference between the Flow Index and other indices of respiratory muscle activity. <b>P</b><span style="font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 10px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><b><sub>0.1</sub></b></span><b>, PMI and dP</b><span style="font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 10px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><b><sub>occ</sub></b></span> are influenced by <b>both pre-trigger and post-trigger inspiratory activity</b>, whereas the <b>Flow Index is influenced solely by post-trigger inspiratory activity</b>. The clinical implication of this difference is crucial: let's try to understand why. Figure 5 presents the PTP, which we previously saw in Figure 1, in a slightly more complex form. </p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><br /></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEhOcMfkVZwkcej8Pj9zyvO_HyPkFkOqAe_IGk4_q5DuMFx5A95ycrIp18FZXxkmC50cbGFU4vTEf7oMNzboLAL-kphektL54zM48UZsxE5SRb5UfLJVfZrmDIKACmxzf41LjFH2Axy-5sj_cGdTVh-7uxpGFjQ7uu9UnlUp_C5rFpSFuBrYTTomMgn9" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="748" data-original-width="340" height="716" src="https://blogger.googleusercontent.com/img/a/AVvXsEhOcMfkVZwkcej8Pj9zyvO_HyPkFkOqAe_IGk4_q5DuMFx5A95ycrIp18FZXxkmC50cbGFU4vTEf7oMNzboLAL-kphektL54zM48UZsxE5SRb5UfLJVfZrmDIKACmxzf41LjFH2Axy-5sj_cGdTVh-7uxpGFjQ7uu9UnlUp_C5rFpSFuBrYTTomMgn9=w325-h716" width="325" /></a></div><br /><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; text-align: center;"><span face="-webkit-standard" style="caret-color: rgb(0, 0, 0); color: black; font-size: medium; text-align: left;">Figure 5</span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Inspiratory activity begins at line "A" (as can be seen from the onset of esophageal pressure reduction), but inspiratory flow starts only at line "C". The <b>pre-trigger inspiratory activity</b>, <b>occurring before line "C" in the PTP</b>, is due to both <b>autoPEEP </b>(PTPpeepi) and <b>trigger activation</b> (PTPtr) <b>thresholds</b>. The <b>portion of PTP</b> <b>beyond line "C" </b>(PTPpost) represents<b> post-trigger inspiratory activity</b>, occurring exclusively <b>after the onset of inspiratory support</b> (i.e., the increase in airway pressure, Paw), and <b>coinciding with the portion of flow analyzed by the Flow Index</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Therefore, the <b>Flow Index </b>is sensitive <b>only</b> to the part of <b>inspiratory effort </b>that originates <b>during inspiratory support</b>. In other words, the <b>Flow Index</b> is a <b>specific indicator of post-trigger inspiratory activity </b>and among the ventilator parameters, it is i<b>nfluenced</b> by the only parameter acting post-trigger, namely <b>inspiratory support</b>.</p><p style="color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><span style="background-color: white;">On the contrary,</span> <span style="background-color: white;"><b>P</b></span><span style="background-color: white; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 12px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><b><sub>0.1</sub></b></span><span style="background-color: white;"><b>, PMI and dP</b></span><span style="background-color: white; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 12px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal;"><b><sub>occ</sub></b></span><span style="background-color: white;"> are influenced by <b>both pre- and post-trigger effort</b>, and thus, both <b>pre-trigger</b> ventilator <b>settings </b>(<b>inspiratory trigger and PEEP</b> in relation to autoPEEP) and <b>post-trigger settings (inspiratory support</b>) have an impact on them.</span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">The clinical implication is that in a <b>patient with signs and symptoms of excessive respiratory muscle activity, a Flow Index > 1 </b>(flow with downward concavity) suggests, as a first step, <b>increasing inspiratory support</b>. Conversely, a <b>Flow Index ≤ 1</b> (flow that decreases <b>linearly or with upward concavity</b>) should indicate that post-trigger effort is already reduced and that it would be more effective to <b>reduce pre-trigger effort</b> by adjusting <b>PEEP</b> or the <b>trigger,</b> or by<b> reducing autoPEEP</b> with bronchodilator therapy and/or sitting position and/or diuretic therapy. Figure 6 provides an example of a patient with these characteristics.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEghch4-zJhtasTQ1UGLQtfNqHmSRzQPs-Yb59Kvm60p6-b23bQ7Y4UMt3g7LTNaxuA8UrUltF9kpJrcbjzyD9b10JYjYBy6ePNH4lqDHeAJVTWbraIyNQxDaj1JiIocjgQA1wJj6OZWz65sMP3Fvex7p_qD4TnjtJBXAd-ODbxk5BcL-NzILjJcXaWb" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="723" data-original-width="302" height="533" src="https://blogger.googleusercontent.com/img/a/AVvXsEghch4-zJhtasTQ1UGLQtfNqHmSRzQPs-Yb59Kvm60p6-b23bQ7Y4UMt3g7LTNaxuA8UrUltF9kpJrcbjzyD9b10JYjYBy6ePNH4lqDHeAJVTWbraIyNQxDaj1JiIocjgQA1wJj6OZWz65sMP3Fvex7p_qD4TnjtJBXAd-ODbxk5BcL-NzILjJcXaWb=w222-h533" width="222" /></a></div><br /><br /><p></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 15.4px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px; min-height: 19px; text-align: center;"><span face="-webkit-standard" style="caret-color: rgb(0, 0, 0); color: black; font-size: medium; text-align: left;">Figure 6</span></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Respiratory muscle activity begins at the white dashed vertical line, and flow initiation occurs at the red dashed vertical line. The entire decrease in esophageal pressure (Pes) occurs between these two lines. After the onset of flow, esophageal pressure does not further decrease, indicating minimal or no inspiratory muscle activity during this phase.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">A <b>significant weakness of the respiratory muscles</b> (as evidenced by a very low maximum inspiratory pressure, see <a href="http://www.ventilab.net/2013/06/mipnif-in-weaning-from-mechanical.html"><span style="color: #520001;">post dated 28/06/2013</span></a>) may be the only <b>exception</b> to this approach. In this case, <b>post-trigger inspiratory activity </b>is <b>low at any level of inspiratory suppor</b>t because the respiratory muscles are unable to generate higher pressure. In this condition, tidal volume solely depends on inspiratory support, and it is the only clinical condition where, in an active patient, pressure support needs to be primarily adjusted to achieve the desired tidal volume.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><b>Conclusions</b></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">Here is a brief summary of the main points from today's post:</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-<b>Inspiratory variation</b> in <b>esophageal pressure</b> is the<b> true objective</b> of <b>inspiratory support</b>. Therefore, esophageal pressure should be measured in patients under assisted ventilation, at least in those with prolonged weaning.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-The <b>Flow Index</b> is a numerical measurement of the concavity of the inspiratory flow and <b>indirectly estimates post-trigger respiratory muscle activity</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-A <b>Flow Index ≤ 1</b> (<b>upward concavity or linear decay</b> of inspiratory flow) indicates <b>respiratory muscle passivity during inspiratory support</b> (<b>post-trigger)</b>.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-A <b>Flow Index > 1</b> (<b>downward concavity</b>) indicates <b>inspiratory activity during inspiratory support</b> (<b>post-trigger</b>): the higher the Flow Index (i.e., the greater the downward concavity of the flow), the greater the inspiratory activity.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">-In patients with signs of <b>excessive inspiratory activity</b>, it is advisable to i<b>ncrease pressure support if the Flow Index is > 1</b> (<b>downward concavity</b>), while<b> optimizing PEEP and trigger or reducing autoPEEP is preferred if the Flow Index is ≤ 1 (upward concavity or linear decay</b>). This approach may not be appropriate for patients with low maximum inspiratory pressure.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;">A smile and happy Easter to all of <i>ventilab’s</i> friends.</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px 0px 15.4px;"><b>References</b></p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">1. Bertoni M, Telias I, Urner M, et al.: A novel non-invasive method to detect excessively high respiratory effort and dynamic transpulmonary driving pressure during mechanical ventilation. Crit Care 2019; 23:346</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">2. Albani F, Pisani L, Ciabatti G, et al.: Flow Index: a novel, non-invasive, continuous, quantitative method to evaluate patient inspiratory effort during pressure support ventilation. Crit Care 2021; 25:196</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">3. Albani F, Fusina F, Ciabatti G, et al.: Flow Index accurately identifies breaths with low or high inspiratory effort during pressure support ventilation. Crit Care 2021; 25:427</p><p style="background-color: white; color: #28384b; font-family: Helvetica; font-feature-settings: normal; font-kerning: auto; font-optical-sizing: auto; font-size-adjust: none; font-size: 18px; font-stretch: normal; font-style: normal; font-variant-alternates: normal; font-variant-caps: normal; font-variant-east-asian: normal; font-variant-ligatures: normal; font-variant-numeric: normal; font-variant-position: normal; font-variation-settings: normal; line-height: normal; margin: 0px;">4. Miao M-Y, Chen W, Zhou Y-M, et al.: Validation of the flow index to detect low inspiratory effort during pressure support ventilation. Ann Intensive Care 2022; 12:89</p></div>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-58297978558090283632022-06-04T22:39:00.001+02:002022-06-04T22:49:30.993+02:00Pneumothorax and mechanical ventilation can get along (even without a chest drain)<p> <a href="http://www.ventilab.it/2022/05/pneumotorace-e-ventilazione-meccanica.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Original post</span></a><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> written on 28</span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">th</span></span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> May 2022 by Giuseppe Natalini</span></p><span id="docs-internal-guid-6ce4701c-7fff-f81b-7064-53cc7b53d8df"><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-align: center;"><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid #f2f2f2; display: inline-block; height: 286px; overflow: hidden; width: 479px;"><img height="286" src="https://lh6.googleusercontent.com/a0ooGVT7kUrA9Iz5YGcEahauoFjpn-ufbCffd3l5W6uPAujRQg26BhS1mrj366kKRfI0Fe257hv7TxrbuXxXTczUN4R-wDVeqJKKyRB_x9Ogms-p0PqfwZr9YnnGlZhkHOrywQASIXBzXSou2w" style="margin-left: 0px; margin-top: 0px;" width="479" /></span></span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Some time ago we had Sonia, a young woman who had a car accident, </span><span style="font-family: Arial; font-size: 18.6667px; white-space: pre-wrap;">among our patients</span><span style="font-family: Arial; font-size: 14pt; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As soon as she arrived to the hospital, Sonia underwent a CT scan which documented a liver laceration with hemoperitoneum, multiple rib fractures with a left pneumothorax and multiple hip bone fractures. In addition to these injuries, Sonia suffered bilateral femoral fractures and a broken forearm.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Immediately after the CT scan, Sonia was taken to the operating room for a laparotomy which had become urgent since, in the meantime, she manifested signs of hemorrhagic shock.</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now Sonia had to start </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">positive pressure mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in presence of a left </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">anterior pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which extended from the apex to the base of the lung, with a thickness of up to 3 cm (Figure 1).</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 200.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 248px; overflow: hidden; width: 624px;"><img height="248" src="https://lh3.googleusercontent.com/eS71KeXdtwMHedK2rCF_6b-lBO8EDRU-uzrwH71gb__fRnb2C04nEyTab0LzVRIX5pT1u4UjpRtl4CJ_4NE44KKzAcMtbKKX5l99yc267wDq9KiZLnPV-YZTsh1ycr3VQ3CRkLRvXtDzpextJA" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 20.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There’s the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">widespread opinion</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that the beginning of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">positive pressure ventilation </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">can </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">aggravate </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">a pre-existing </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and that therefore, in these conditions, a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">chest drain </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">should be put in place </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">before </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the pneumothorax evolves into a</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> tension pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (which is a possible event in presence of a one-way valve mechanism).</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The belief that mechanical ventilation can be, by itself, more dangerous than spontaneous breathing for the development or worsening of a pneumothorax is, in my opinion, a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">prejudice</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">without any physiological basis</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">not in agreement</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> with</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">data from</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> medical literature</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Let’s try to delve into the topic.</span></p><br /><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Spontaneous breathing, mechanical ventilation and transpulmonary pressure. </span></h2><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">The main difference between spontaneous breathing and positive pressure mechanical ventilation is the pressure in the lungs during inspiration: during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;"> the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressure inside the lungs </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">higher</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;"> than the one detected during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">spontaneous breathing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">.</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s hypothesize that a patient is ventilated without PEEP, with a tidal volume (V</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">T</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) of 0.5 L and that his respiratory system’s elastance (E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">rs</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) is 24 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O/L (which corresponds to a compliance of 42 mL/cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O). In Figure 2 we outline the</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> intrapulmonary pressures </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">at the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">end of expiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and at the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">end of inspiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in this subject, wheter he is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">breathing spontaneously</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or wheter he is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanically ventilated</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 405.25pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 476px; overflow: hidden; width: 610px;"><img height="476" src="https://lh4.googleusercontent.com/0YxQ4FKU2FmXcYftcbHw11vgDh7bzj_LU8zgHj6dMFsxmGVUiGlgnx7N8jmkuGNf2eavcqdkIPVvzFxJ_Qan6608vQ1p4vhLso6cvILt5aMwqYS-45emIGfQQHHd1xGoKYSIF5RPWsIIKSpoSA" style="margin-left: 0px; margin-top: 0px;" width="610" /></span></span></p></td></tr><tr style="height: 20.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In case of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous breathing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, intrapulmonary pressure at the end of inspiration is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">0 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">distension of the chest wall </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">by the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory muscles</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> brings the pressure in the lungs, </span><span style="font-family: Arial; font-size: 18.6667px; white-space: pre-wrap;">after having introduced the whole tidal volume, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">at the same level as atmospheric pressure. If the same tidal volume is brought in the lungs by </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, the pressure in the lungs at the end of inspiration is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">12</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This number can be obtained with the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">equation of motion of the respiratory system</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which lets us calculate the pressure that must be applied to the respiratory system during ventilation (see also the </span><a href="https://www.ventilab.it/2011/06/ards-e-volume-corrente-la-risposta.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">post written on 24/06/2011</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">available only in Italian at the moment</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">):</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">appl</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">el</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> + P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">res</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> + P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0</span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">where P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">appl</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the pressure that must be applied, P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">el</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the elastic pressure, P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">res</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the resistive pressure and P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the pressure at the beginning of inspiration.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If PEEP is not used, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">appl</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> = P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">el </span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">in the instant in which inspiration ends, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">because in this moment resistive pressure (which is the product of flow and resistance) becomes 0 since flow falls to zero after the whole tidal volume has been inhaled. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lungs</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> at </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the end of inspiration </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is therefore</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">elastic pressure, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">i.e. the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">product </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">elastance</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tidal volume</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">appl </span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">= P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">el</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">rs</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">٠V</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">T</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = 24 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O/L ٠0.5 L = 12 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If we stop </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">with our analysis </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">at </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">this level</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, the opinion that mechanical ventilation has a greater risk to aggravate a pneumothorax than spontaneous breathing could be reasonable: the </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressure inside the lungs is actually higher during mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and could apparently favor the leakage of air from the lungs. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">But this is obviously only an illusion. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">The pressure that indeed distends the lungs </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(and which can favor the leakage of air from a pleural lesion) is not the pressure inside the lungs but the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">difference between the pressure inside and the one outside the lungs, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">i.e. </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">transpulmonary pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 3 repeats the outline shown in Figure 2, with the addition of the calculated pleural pressure values (that is, the pressure outside the lungs):</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 399.25pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 476px; overflow: hidden; width: 610px;"><img height="476" src="https://lh6.googleusercontent.com/c0fJyz1c2q4ADLaXP919MDYi5gZ_vWlgv1hmyIfCaQBPadVt3Xsw2u_NJlnUfSjjfRG8ELrXEMRGqa4Ha2VcjMvOzKZjVa8nLUSgTx0P2yiAPr3O_3VUHbp3TBsxe3oLXozkvKSAugLK5R-cQA" style="margin-left: 0px; margin-top: 0px;" width="610" /></span></span></p></td></tr><tr style="height: 20.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 3</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s see how we can calculate pleural pressures in different conditions. We have, for simplicity’s sake, hypothesized that pleural pressure before the beginning of inspiration is 0 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 18pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now let’s calculate </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pleural pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> at </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the end</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. To do this, we</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> must </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">know </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lung elastance</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">chest wall elastance </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">The elastance of the respiratory system is the sum of E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> and E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">rs</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> + E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s hypothesize that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">⅔</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">rs</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (therefore 16 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O) and that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">⅓</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">rs</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (therefore 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O), as can be obtained, on average, from physiological studies on the partition of respiratory mechanics between lung and chest wall. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">This implicates</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that ⅔</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the pressure applied to the respiratory system (the one measured in the ventilator) is the pressure that distends the lungs at the end of inspiration (E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">٠V</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">T</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). The "</span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressure that distends the lungs”</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">difference</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> between </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the pressure inside </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">outside the lungs</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e. the pressure in the </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pleural space</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Similarly, we can calculate that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">⅓</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure delivered by the ventilator </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is necessary to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">distend</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">chest wall</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">٠V</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">T</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). The "</span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressure that distends the chest wall</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">" is the </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">difference</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> between the </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> inside the chest wall (that is, pressure in the</span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> pleural space</span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">)</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and the one </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">outside the chest wall</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which is </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">atmospheric pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Since atmospheric pressure is 0 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, the "</span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure that distends the chest wall</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">" is equal to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pleural pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In our example, the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that distends the chest wall (P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) at the end of inspiration during mechanical ventilation is therefore:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">٠V</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">T</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">= 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O/L ٠ 0.5 L = 4 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This is also the value of pleural pressure that you find in Figure 3 for mechanical ventilation. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The pressure that distends the lung at the end of inspiration in this simulation is 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O and not 12 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, as appeared by looking at Figure 1, which showed only intrapulmonary pressures. Transpulmonary pressure (P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) at the end of inspiration (8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O), which we have calculated as the difference between pressure inside and outside the lungs, can also be directly calculated, in analogy with previous elastic pressures, as:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">L</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">٠V</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">T</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = 16 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O/L ٠ 0.5 L = 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This formula makes it absolutely clear that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">transpulmonary pressure at the end of inspiration depends </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">only </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">on </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">tidal volume</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">lung elastance</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Since these </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">rules</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> are </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">valid for</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">both</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous breathing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure that distends the lungs at the end of inspiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> will be </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the same in both conditions </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">if </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lung elastance</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tidal volume </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">are</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> the same.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The only difference between mechanical ventilation and spontaneous breathing is the pump which generates tidal volume: in mechanical ventilation </span><span style="font-family: Arial; font-size: 18.6667px; white-space: pre-wrap;">pressure in the lungs </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is increased by an external machine, during spontaneous breathing pressure outside the lungs is decreased by the</span><span style="font-family: Arial; font-size: 18.6667px; white-space: pre-wrap;"> respiratory muscles</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In this last instance, in order to have a transpulmonary pressure </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">at the end of inspiration,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> we must have a pleural pressure of - 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O. Pleural pressure in the active patient can be calculated from the equation of motion (and in our example it would actually be - 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O), but I am going to spare you the calculations. If someone is interested, we can talk about it in the comments section below the post (or in another post). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This is why it is an illusion to think that spontaneous breathing is more protective than mechanical ventilation for the evolution of a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pneumothorax.</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> Rather, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">paradoxically,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">might be preferable in case</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneously breathing </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">patient generates a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">high tidal volume</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: indeed, with </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">controlled ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> we can decide to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduce</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tidal volume</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and, consequently, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">transpulmonary pressure.</span></p><br /><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">What happens when we apply PEEP.</span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s hypothesize that we are applying a PEEP of 12 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O to our hypothetical patient, both during spontaneous breathing and during mechanical ventilation. The situation can be summarized in Figure 4:</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 400pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 476px; overflow: hidden; width: 610px;"><img height="476" src="https://lh6.googleusercontent.com/LBUIVExK_xrySFuv3Bhqiv1bEjP_AKMr-M2BxDh0M-n236RGUk4Vnor69j77bQI19Kye7Sg5iZkPXkxKHl4GIn6Ed58adWSaLLxGWzN6m5vYV9PTusV_GaQkzDjMDKShAqhCkS1EnTQ5rID_iA" style="margin-left: 0px; margin-top: 0px;" width="610" /></span></span></p></td></tr><tr style="height: 20.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 4</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The increase in pleural pressure as a consequence of the increase in airway pressure occurs with the same basis for both the delivery of the tidal volume and the application of PEEP. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Since in our example with assumed that E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">cw</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">/E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">rs</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = ⅓, the increase in pleural pressure at the end of expiration after the application of PEEP is ⅓ of the applied PEEP. This leads to a transpulmonary pressure, </span><span style="font-family: Arial; font-size: 18.6667px; white-space: pre-wrap;">at the end of expiration, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of 8 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O in both spontaneous breathing and mechanical ventilation: at the end of expiration there is already a high transpulmonary pressure that favors the emission of air from the lungs.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Repeating the calculations we have already seen for inspiration, we reach a transpulmonary pressure of 16 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O at the end of inspiration, independently for the ventilation modality. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This means that the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">application of</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can effectively </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">contribute to increasing the pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, but this happens </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">in the same way for spontaneous breathing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (for example with </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">CPAP</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during non invasive ventilation) and for </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Pneumothorax and mechanical ventilation: what does medical literature say?</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In light of what we have said before, it is not surprising that the frequency of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and its recurrences (conditions in which no positive pressure ventilation is implied) is especially high for </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tall and skinny subjects</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (1,2). During spontaneous breathing, a tall and skinny subject will have the same intra lung pressure as a short and overweight subject, but will reasonably have a lower pleural pressure. The fact that this physical constitution favors spontaneous pneumothorax can be seen as a confirmation that it's not the pressure inside the lungs, but the difference between the pressure inside the lungs and the pleural pressure which favors the development of pneumothorax.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There are several studies on the effects of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in patients with </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occult pneumothorax,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that is, those forms of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">anterior pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which are </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">clearly visible on CT scan</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> but </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">not evident on chest X-rays </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(as was the case for Sonia). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Medical literature confirms, with both observational studies and randomized and controlled trials, that the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">clinical evolution of</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> occult </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pneumothorax </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">independent </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the presence of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous breathing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">positive pressure ventilation,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and that the</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> frequency </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory distress</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is similar in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patients who have a chest drain put in as soon as the occult pneumothorax is diagnosed </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">those</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in whom </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pleural drainage</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">is reserved for the onset of signs of tension pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, more frequent in patients receiving long-lasting mechanical ventilation (for more than 5-7 days) (3-7).</span></p><br /><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">What happened to Sonia.</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Sonia underwent mechanical ventilation with protective ventilation, without placing a chest drain.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Sonia’s clinical history was very complex, but after about a month in the intensive care unit all issues were satisfactorily resolved and she is now home. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During her stay she had various complications, both pulmonary and extrapulmonary, but the pneumothorax never became a tension pneumothorax and it reabsorbed completely without any medical intervention. In Figure 5 you can see her chest CT scan (with scans similar to the ones seen in Figure 1) after about ten days on mechanical ventilation: you can see an ARDS, but there is no air left outside the lungs.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 240.25pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 267px; overflow: hidden; width: 624px;"><img height="267" src="https://lh6.googleusercontent.com/c6z6fY4sjS2PI18_4ZQCnsQORXhZK1yKqB4wQwBPyGLe0ocT7gj8rQ__6rmAqGGwBoS2m9zeI3aD7Z7NUzoUBJtYLp0Xev50mxlSNoMJxaVN1Ypnq8EnkK2ryfwSlKuFvhX6f5MwqisJGGZM6A" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 20.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt 5pt 5pt 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 5</span></p></td></tr></tbody></table></div><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Conclusions</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We can summarize the main messages of this post below:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">1) In case of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occult and/or clinically not significant pneumothorax,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">positive pressure mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can be safely started </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">without </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the placement of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">a preventive chest tube</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">; clearly, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pleural drainage</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> becomes a necessity (sometimes an urgent one) when signs of a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tension pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> develop (especially in case of severe hypoxemia and hypotension);</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2) If a patient with </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pneumothorax </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">undergoes </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tidal volume reduction </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> intense inspiratory effort abolition </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">make up a protective strategy which reduces the risk of aggravating the pneumothorax compared to a ventilation with high tidal volume/high inspiratory effort (during both spontaneous breathing and mechanical ventilation);</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">3) In presence of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> should be kept to the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">minimum necessary value</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which is compatible with an appropriate mechanical ventilation. Indeed, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">promote </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">an </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pneumothorax</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">regardless</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous breathing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As always, greetings and a smile for all </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab’s </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">friends.</span></p><br /><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">References</span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">1.Nakamura, H. et al. Physical constitution and smoking habits of patients with idiopathic spontaneous pneumothorax. Jpn J Med 22, 2–8 (1983).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2.Sadikot, R. T., Greene, T., Meadows, K. & Arnold, A. G. Recurrence of primary spontaneous pneumothorax. Thorax 52, 805–809 (1997).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">3.Barrios, C. et al. Successful Management of Occult Pneumothorax without Tube Thoracostomy despite Positive Pressure Ventilation. Am Surg 74, 958–961 (2008).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">4.Wilson, H., Ellsmere, J., Tallon, J. & Kirkpatrick, A. Occult pneumothorax in the blunt trauma patient: Tube thoracostomy or observation? Injury 40, 928–931 (2009).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">5.Kirkpatrick, A. W. et al. Occult pneumothoraces in critical care: A prospective multicenter randomized controlled trial of pleural drainage for mechanically ventilated trauma patients with occult pneumothoraces. J Traum Acute Care Surg 74, 747–755 (2013).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">6.Zhang, M., Teo, L. T., Goh, M. H., Leow, J. & Go, K. T. S. Occult pneumothorax in blunt trauma: is there a need for tube thoracostomy? Eur J Trauma Emerg Surg 42, 785–790 (2016).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">7.Clements, T. W. et al. OPTICC: A multicentre trial of Occult Pneumothoraces subjected to mechanical ventilation: The final report. Am J Surg 221, 1252–1258 (2021).</span></p><p dir="ltr" style="background-color: #fcfcfc; line-height: 1.92; margin-bottom: 0pt; margin-left: -1pt; margin-right: -1pt; margin-top: 20pt;"> </p><br /></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-29179510031557845412022-03-30T17:59:00.004+02:002022-06-04T22:50:39.098+02:00HME filters on the ventilator circuit’s expiratory branch: problem or solution?<p> </p><span id="docs-internal-guid-f8eea77d-7fff-397b-6793-8a7e4c64b8dd"><p dir="ltr" style="line-height: 1.92; margin-bottom: 17pt; margin-top: 0pt;"><a href="http://www.ventilab.it/2022/03/i-filtri-hme-sulla-branca-espiratoria.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Original post</span></a><span style="color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> written by Giuseppe Natalini on 30th March 2022</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-align: center;"><span style="color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 144px; overflow: hidden; width: 119px;"><img height="144" src="https://lh6.googleusercontent.com/CNxJKX6bsO8nfDqLAnuC_yGlxeJ_p1HkYd1ZfF7V4fpwDZf11URaUz-O8CPqr7-rFwaENIQz8wsI3RU1K7zxxnCXe_0aNXGs95K9W-84r9QLARWDmd0_erxwQRxR6EF8A5tqhHAihLstFkngPg" style="margin-left: 0px; margin-top: 0px;" width="119" /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-align: center;"><span style="color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 144px; overflow: hidden; width: 119px;"><br /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In previous posts (see the ones written on </span><a href="https://www.ventilab.it/2022/01/modalita-di-ventilazione-e-monitoraggio.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">08/01/2022</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and on </span><a href="https://www.ventilab.it/2022/01/oscillazioni-cardiogeniche-ed-attivita.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">21/01/2022</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) we have discussed the aspects of the image you can see in Figure 1 which have attracted </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> readers’ attention. Today we are going to discuss the points that attracted </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">my</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> attention as I was walking in front of the patient’s monitor, and that made me stop to analyze and solve an obvious issue. We are therefore going to try and systematically analyze the problem, which has also been detected by some readers.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 220pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 273px; overflow: hidden; width: 624px;"><img height="273" src="https://lh4.googleusercontent.com/eGQ1CC-PnkltWdCC7nSPRPe8LkYBxrX9Q5Ttr-AodYIaFejjmEhI5KXdPPDEX1bN17bTqubU5JlEwUVfs1RcGG4C_8TAjCevZ21lzfNwIMaVLnvnNv1Bi8num4KCFYOHEKxanaU73kroi_xekg" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As you can see in Figure 2, </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the inspiratory flow peak</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (0.97 l/s) is </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">more than twice as big as the expiratory flow peak </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(0.42 l/s). </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 217.75pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 271px; overflow: hidden; width: 624px;"><img height="271" src="https://lh6.googleusercontent.com/SCi2VENFj_OZt7wwuBDQjfN0F3wAIF7CjgWs1oNnknr89jZB8tIJC2FpGhmQtTj_Aq7UTrco3aWhkJDd19CkwA0ycdqdbEDb6DoN7MfKTHbDUW9BV4T5GuqhhtGb9sIorZIsYQ2NTpHRM42xNg" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Tidal volume inspiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (which coincides with the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">presence of inspiratory flow</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during the inspiratory time) </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">is completed very fast</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, using only the first 0.44 seconds of the 1.2 seconds which make up the inspiratory time. On the contrary, the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">whole expiratory time</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (1.2 seconds, the same as inspiration), is </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">not sufficient to zero the expiratory flow</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In other words, during</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> inspiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> we can sense the presence of a really</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> low time constant</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">“fast inspiration”</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) while during </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> we can sense the presence of a really </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">high time constant</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">“slow expiration”</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). (you can find previous posts on the time constant here -</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">available only in Italian, at the moment </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">-: </span><a href="https://www.ventilab.it/2016/06/costante-di-tempo-dell-respiratorio.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">30/06/2016</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><a href="https://www.ventilab.it/2016/07/costante-di-tempo-e-ventilazione.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">17/07/2016</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><a href="https://www.ventilab.it/2014/02/costante-di-tempo-e-ventilazione.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">05/02/2014</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This is a truly </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">abnormal behavior</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, since we would expect </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the inspiratory and expiratory flow peaks</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to have a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">similar amplitude </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(or the expiratory flow peak to be higher than the inspiratory one in case of autoPEEP), and a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">similar</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">shape of the inspiratory and expiratory flow curves</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (in absence of flow limitation). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">coexistence</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">“fast” inspiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">“slow” expiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can be explained either by a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">big difference between inspiratory and expiratory resistance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">or</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> by the presence of </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">flow limitation </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(you can see the post on flow limitation written on </span><a href="https://www.ventilab.it/2012/06/flow-limitation-diagnosi-ed.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">04-06-2012</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, -</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">available only in Italian, at the moment </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">-). In this case, we can reasonably </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">exclude </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the presence of</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> flow limitation </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">since the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory flow </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">has a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">normal exponential decay</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">only possible explanation</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">significant difference between inspiratory and expiratory resistances</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. These resistances include both the patient's</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> airway resistance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory circuit’s resistance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In Figure 2 we saw that the expiratory flow peak is less than half as big as the inspiratory flow peak: since </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">flow</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is i</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">nversely proportional to resistance, expiratory resistance is more than twice as big as inspiratory resistance, </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and it would make little sense to attribute this condition to the airways.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We therefore can deduce that there must be </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">an additional expiratory resistance which does not belong to the patient.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">And this is true in our case: as sometimes (or often, depending on habit) happens is Intensive Care Units, an</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> antibacterial HME </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(Heat and Moisture Exchanger) </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> was positioned </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">at the end of the expiratory branch </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">on the respiratory circuit in order to protect the expiratory valve from possible contaminants present in the exhaled air.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The problem is that </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">HME </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">filters are made specifically to absorb humidity, and they can be </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">useful</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in this sense if they are </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">placed on the circuit’s Y</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">they accumulate expired humidity</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and give it back to the patient immediately during inspiration. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">When an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">HME filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is placed on the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory branch</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, it </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">absorbs</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> any eventual excess </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">humidity </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(it’s its job!), and, by “getting soaked in water”, it becomes an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">additional resistance between the patient and the ventilator’s expiratory valve</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. A </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">resistance which is entirely expiratory</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s try to better understand this mechanism by looking at Figure 3, which shows the ventilator’s circuit: the INSP branch brings the flow of gas from the ventilator to the patient and the ESP branch brings expiratory flow on the outside, by making it pass through the ventilator’s expiratory valve (shown in red).</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="413"></col></colgroup><tbody><tr style="height: 305.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-right: 12pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 395px; overflow: hidden; width: 400px;"><img height="395" src="https://lh5.googleusercontent.com/p1LmqjQYZjoijEhH1o37r0vz3X8ckDtcCPe7Zt97jb1Sn_lph04VOZ5DmA60BShcIIyP3urqGA3MiPBR3CUaKRQ_lyhRaLG1ydSjwEwvNonDSxu_hKoUCAdmejmgJbLvhqQXau1sxsF8fK1VPw" style="margin-left: 0px; margin-top: 0px;" width="400" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-right: 12pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 3</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The HME filter put on the expiratory branch in order to protect it from possible contaminants is shown in green. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During expiration, the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory valve</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> continuously </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">regulates</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> its </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">opening</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> against flow in order </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">to maintain, </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">at its entrance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, the same </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> as set </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">If the HME filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> at the end of the expiratory branch </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">becomes a significant resistance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, the</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> pressure above the HME filter </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(towards the patient) will be significantly </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">higher than the one below</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the filter (towards the expiratory valve).</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In this condition, the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory valve</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> continues to </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">modulate pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in the section between </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">itself and the HME filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, but it is </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">insensitive to pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">above the HME filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (between the HME filter and the patient), which therefore is </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">determined by HME filter’s resistance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and not by the expiratory valve. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The patient will have an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory pressure much higher than set PEEP, </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">which will become an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">obstacle to expiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In Figure 4 you can see the difference between PEEP, set at 6 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (horizontal gray line) and the real pressure during expiration, which, even at the end of expiration, does not reach the set value and stops at a PEEP of 8 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (horizontal red line). The dashed yellow line show the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ideal pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that should have been present </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">during expiration</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">. an immediate transition from inspiratory pressure to PEEP</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: we can hypothesize that, in the portion of circuit between HME and the expiratory valve, pressure was very similar to the own shown by this line.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 215.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 268px; overflow: hidden; width: 624px;"><img height="268" src="https://lh5.googleusercontent.com/Ky9x1TCHICzWK9h8MMa6UMp-RJ-GwW0DqiV_JfAhIrfUWmzLisQdcpkpTVAfYwo0Yw5gdmzjiDErkQCBfMWYVGp2r2jZCO8TZgAaw9VW9K0lR_uIYcShhbwLWH7MZDrYpDpygCMS3sU0deGJUA" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 4</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Proof that, in our case, this was the correct interpretation of what was happening was given by </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">eliminating the HME filter from the expiratory branch.</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> The immediate result can be seen in Figure 5. </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 221.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 276px; overflow: hidden; width: 624px;"><img height="276" src="https://lh5.googleusercontent.com/UYCPxPZKW1_VGczpFvsRLILm7MJVJeg6bL00UfTgmk2MvrtaDaLB68PHat6OwQVorift5vVqjiEa30pK0tU5P2HAPH6yGygA8z9SFhQBRgchXUL39VJI04zcLrx2cPTIB44rqAURAuuAc5eiGw" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 5</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">At a glance, it is completely different from the image in Figure 1: </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the crude differences between inspiration and expiration have disappeared</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. We can confirm this by measuring inspiratory and expiratory flow peaks and duration of flow during inspiration (Figure 6). </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 227.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 284px; overflow: hidden; width: 624px;"><img height="284" src="https://lh3.googleusercontent.com/Tye9r7-uZX3fEm4baYURz9VR7NFkgMs5ANabV6WSKjDwdFyu_zbameRIVQWXh1bBeUTB3v_taAa2bmlj7albd7S1xnemrqkJQW3bPDm5eD1oF3bz79Scjsz4iINBHGybM787_lQDTlEZA3yxcw" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 6</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There are still some small differences left, which are hard to find without measurement, and which are absolutely compatible with normality. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The problem we have described can have </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">unfavorable implications for patients</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In our case, it did not cause any problems, giving only an autoPEEP of 3 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (measured with an end expiratory occlusion) in a sedated and paralyzed restrictive patient.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">But let’s think about an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">obstructive patient</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">assisted ventilation</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The obstacle to expiration and the resulting </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">worsening </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dynamic hyperinflation </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">would produce an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase in the work of breathing </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">associated with a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lesser diaphragm efficiency</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> due to the flattening of the muscle caused by an increased end expiratory lung volume. In other words it could iatrogenically perpetuate the dependency from mechanical ventilation in patients with the potential to be weaned from it.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Considering the risks we have seen</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">, is it the right thing to put a HME filter on the expiratory branch? Do benefits outweigh risks?</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In my opinion,</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> no filter is needed</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> if </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inhaled gas humidification</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">administered inhalation therapies</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> are</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> carried out correctly</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. During</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> administration of inhalation drugs,</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> it could be better to use a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure trigger</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in order to limit the effect of </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">continuous flow with a flow trigger</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (see the post written on </span><a href="https://www.ventilab.it/2011/05/trigger-inspiratorio-e-trigger.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">22/05/2011</span></a><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> -</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">available only in Italian, at the moment </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">-), which could favor the passage of the drug from the delivery point to the expiratory valve.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If humidification and drug administration are not carried out correctly, the solution is to improve the way they are performed, not to use a filter. In case of inappropriate humidification, applying a filter to protect the ventilator perpetuates the problem of excessive humidification. If drugs end up in the expiratory branch, using a filter perpetuates the fact that part of the drug which should reach the patient would be “wasted” in the filter: the only real solution is a correct administration of the drug. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">I realize that, sometimes, a filter on the expiratory branch is the lesser evil, or that the filter can have the theoretical role of avoiding environmental contamination with pathogens: in these case, it might be better to use a non-HME filter, keeping an eye on flow and pressure curve monitoring in order to recognize immediately the moment when the filter needs to be changed.</span></p><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s check the numbers…</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In this section we are going to quantitatively analyze what we have just described, making a small exercise in respiratory mechanics. Don’t worry if you are not interested in this discussion (with calculations and formulae): you can jump directly to the conclusions. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In Figure 7 you can see the curves with a series of values recorded during inspiratory and expiratory flow peaks.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 329.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 416px; overflow: hidden; width: 624px;"><img height="416" src="https://lh3.googleusercontent.com/lwf7Czn00bubKbPnVPAfh0l5xPv7W3dOIxyF4BURNcAk1bXVFCTrp4x5hIIE7cPiksRiflMvkoioggH0olspazuzQCstKncHiS1C_opUoBTiuKG95mTViwXSO-Zl2HFuoPDQT2Cv1TgFIPUPiw" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 7</span></p></td></tr></tbody></table></div><br /><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Compliance.</span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">First of all, we can calculate </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Compliance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (C), thanks to the fact that a constant i</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">nspiratory pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is associated with a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">period of no airflow</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during more than half of the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory time</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: this is, to all effects, a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">plateau pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (Pplat). The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">total PEEP </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(PEEPtot) was measured during an </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">end expiratory occlusion: </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">I have recorded its value (9 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O ) on Figure 7. The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">difference between Pplat </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(25 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O ) and </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEPtot </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">elastic pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (Pel): 16 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">C</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ompliance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e. the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ratio</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> between <b>tidal v</b></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><b>o</b></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lume corrente</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (225 ml) and </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Pel</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, is 14 ml/cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O .</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">compliance value</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> will let us </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">estimate </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Pel </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">at different</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lung volumes</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, since </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Pel </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is always the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ratio </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">between</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> volume (V) </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> compliance (V/C)</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">alveolar pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (Palv) is always the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">sum </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Pel </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEPtot</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><br /><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Resistive pressure and resistance during the inspiratory flow peak. </span></h3><br /><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Flow </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">is alway </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">generated </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">by a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressure difference</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">, also called </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">resistive pressure</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;"> (Pres).</span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Pres </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">that generates </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory flow peak</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (PIF) is the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">difference </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">between </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(Paw) when there is the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PIF </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(25 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, in this case equal to Pplat) and </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Palv at the same time</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During the PIF, the lungs contain 116 ml of volume (above the end expiratory lung volume), which determines, in that instant, a Pel of 8 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (V/C). Adding Pel to PEEPtot, we can estimate a Palv of 17 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">PIF’s Pres is the difference between Paw and Palv: 25 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O - 17 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O = 8 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O . </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Resistance </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is calculated as the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ratio </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">between </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Pres </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">flow</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> it generates. Resistance during PIF is therefore: 8 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O / 0.97 l/s = 8 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s.</span></p><br /><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Resistive pressure and resistance during the expiratory flow peak.</span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Repeating the same calculations for the </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory flow peak</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEF</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">), we can estimate a Pel during PEF of 14 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, generated by 190 ml of volume which are still in the lungs at that time. Adding it to PEEPtot we obtain a Palv during PEF of 23 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">PEF’s Pres is 3 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, i.e. the difference between 23 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (Palv) and Paw during PEF (20 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, Figure 7). Resistance during PEF is therefore: 3 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O/ 0.42 l/s = 7 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The fact that </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory and expiratory resistance </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(calculated during the respective flow peaks) are </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">similar </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(8 and 7 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s, respectively) confirms that the difference between expiratory and inspiratory resistance is not due to the patient. In fact we have made our </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">calculations </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">using a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of 20 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O during PEF</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">which the ventilator obviously measures </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">before </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(above)</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> the HME filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Figure 8 can help to better understand this explanation: inside the light blue circles you can read the pressure found in different point at the time of the PEF, in the gray squares on the right the pressure differences between the different points. </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="413"></col></colgroup><tbody><tr style="height: 283.75pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 365px; overflow: hidden; width: 400px;"><img height="365" src="https://lh3.googleusercontent.com/freV9slalhSSd8R--EZ0yuZaGohflVBfNJaM-H8HRn4Nsec3BJxlx_8VjOf0IePkJw9eZ9IGhcxfnoS9L175W1cCOcouDADeMPftt3kZr8tIcRQ7Jr4cpLWlABKyN4SkeUgOihIM4VQq-qY9kg" style="margin-left: 0px; margin-top: 0px;" width="400" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; border-bottom: solid #f2f2f2 0.75pt; border-left: solid #f2f2f2 0.75pt; border-right: solid #f2f2f2 0.75pt; border-top: solid #f2f2f2 0.75pt; border: 0.75pt solid rgb(242, 242, 242); overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 8</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">HME filter</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> creates a </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">resistance</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to flow which can be measured if </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure difference above and below </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the filter itself is known. Above the filter, during PEF, we have a measured pressure of 20 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, below the filter we can estimate we have a pressure equal to the set PEEP (6 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O), which the expiratory valve should maintain throughout the entire expiration.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The filter’s Pres during PEF is therefore 14 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, which, with a flow of 0.42 l/s, let’s us calculate a resistance of 33 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During expiration, the patient must overcome both his own resistance (7 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s) and the filter’s resistance (33 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s), which equals, in total, 40 cmH</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O·l</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">-1</span></span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">·s: an enormous resistance, mostly (83%) due to the HME. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">For this reason the presence of the filter is the root of the problem, and its removal is the solution. </span></p><h1 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Conclusions.</span></h1><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s try to summarize the main points illustrated in this post: </span></p><ol style="margin-bottom: 0px; margin-top: 0px; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 12pt;"><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Graphical waveform monitoring detects problems </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(even severe ones) </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">which are not detected by ventilator alarms:</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> only the analysis of pressure and flow curves let us make the correct diagnosis and solve the problem immediately;</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">need </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">to use </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">filers </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">on </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilator circuit’s </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory branch</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is conditioned by an </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inadequate airway humidification</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and/or </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inefficient administration of inhalation drugs</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In these cases the primary solution should be the optimization of humidification and drug delivery, instead of placing a filter to protect the expiratory valve;</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In case the placement of </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">a filter at the end of the expiratory branch</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> deemed necessary</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, it might be better to chose an antibacterial/antiviral non-HME filter and to</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> keep an eye on pressure and flow curves </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ensuring that:</span></p></li></ol><ul style="margin-bottom: 0px; margin-top: 0px; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory pressure rapidly</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> returns to the set </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP value at the start of expiration</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 15pt; margin-top: 0pt;"><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, the </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">shape </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory flow are similar in passive patients without flow limitation</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p></li></ul><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As always, a smile for all the friends of </span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><br /></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-20746586481978135812022-01-22T11:26:00.010+01:002022-06-04T22:51:53.274+02:00 Welcome to the world of ventilab <p>This blog is born from the desire to make <i><a href="http://www.ventilab.it" target="_blank">ventilab</a></i>'s contents available worldwide.</p><p>It contains my translations of posts from the <a href="http://www.ventilab.it" target="_blank">original <i>ventilab </i>blog</a>. As you might now, the posts in Italian are over 200: I will keep on adding content (both new posts as they are published and old ones) as time goes on, hopefully managing to make all posts available in time.</p><p>If you have interest in a specific post, please let me know via email (ventilabinternational@gmail.com).</p><p>Comments to posts are deeply welcome: I hope interesting discussions on mechanical ventilation can be born here also, as is the case for the Italian blog.</p><p>Translations have not been reviewed by the authors of the original posts, and any mistakes are solely my responsibility.</p><p>Happy reading :)</p><p><br /></p><p>Federica</p>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-5581645235159816422022-01-21T20:12:00.000+01:002022-01-27T09:17:53.466+01:00Cardiogenic oscillations and respiratory activity<p><a href="http://www.ventilab.it/2022/01/oscillazioni-cardiogeniche-ed-attivita.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Original post</span></a><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> written on </span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">21</span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">st</span></span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 13.5pt; white-space: pre-wrap;">January 2022 by Giuseppe Natalini</span></p><span id="docs-internal-guid-3e32818f-7fff-ea3a-adf1-fd93b9e5b4b7"><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-align: center;"><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 245px; overflow: hidden; width: 300px;"><img height="245" src="https://lh4.googleusercontent.com/AdhBeSUTFWKxzZYhCMq9Ia457Fe2ttsR_-wjwPAIL3a7feJvFRQ7w7zqF7CHyqnV3sKntL2xTqiLSzda-NCACCw2BV_LARzhvUvYTSM_Gy75QH5LMHlcEC2NBa9F8dRc7Il23Wml" style="margin-left: 0px; margin-top: 0px;" width="300" /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s continue the analysis of the case presented and discussed in previous posts (</span><a href="http://www.ventilab.net/2022/01/mechanical-ventilations-graphical.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">here</span></a> <span style="font-family: Arial; font-size: 18.6667px; white-space: pre-wrap;">and </span><a href="http://www.ventilab.net/2022/01/ventilation-modalities-and-graphical.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">here</span></a><span style="font-family: Arial; font-size: 14pt; white-space: pre-wrap;">). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Many readers have lingered on the oscillations which can be seen on the pressure trace (and, to a smaller extent, on the flow trace). Two interpretations were given: 1) they are a sign of the patient’s</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, not in sync with the ventilator; 2) they are </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cardiac artefacts</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In order to understand which interpretation is correct (or if both are) let’s analyze the traces (see Figure 1) systematically using the RESPIRE method (see </span><a href="https://www.ventilab.it/2017/09/sforzo-inefficace.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">this</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><a href="https://www.ventilab.it/2019/04/sforzo-inefficace-doppio-trigger.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">this</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post in Italian -to be translated in English soon).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The steps </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">R</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Recognizing </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">important curves) and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">E</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Exhalation </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- ventilator) have already been proposed in Figure 1 and 2 on </span><a href="http://www.ventilab.net/2022/01/ventilation-modalities-and-graphical.htmltilazione-e-monitoraggio.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">this post</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 214pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 265px; overflow: hidden; width: 624px;"><img height="265" src="https://lh4.googleusercontent.com/jMtIUJKh7jgdvQ-oKHW_9YXcqDcEaYPvXTpQv_fRURZISIOLAWsOLRm1IzLSm_HkhJsAZu6ARmyInvXxOlOJQ543lZ0i1jYRT_V6dML24UHFuAm-cp8PcDHeciOrZjApw9yJnTjN" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now lets process with the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">S</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Suppose </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the patient is passive). With </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> we expect to see a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">constant inspiratory pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">decreasing flow</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Expiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">any ventilation modality</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, should have a</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> constant pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (at </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP level) </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">decreasing flow</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The white dashed line in Figure 2 shows how the curves could be if the patient did not have any respiratory activity. </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 220pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 273px; overflow: hidden; width: 624px;"><img height="273" src="https://lh3.googleusercontent.com/QTZVklDkvW6obpuwDKEGWBEkt70-J8PFtBBFUvez1ZLJB15QoF3E0tzJrTtV3SK17ZNeh6ut9aRtfpGRo-WXneScZrswiGUzyHzjaQO3Kr_oVJT7MoM2vfJhpkuyrGpLuKLUTmQU" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now let's see where to place the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">): in the middle between </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the pressure trace (above)</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">flow trace (below) </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(Figure 3),</span></p><br /><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 260.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 327px; overflow: hidden; width: 624px;"><img height="327" src="https://lh6.googleusercontent.com/jfbr1DmiMgyEGFBSs8ug253uJmpaF0HJ4136nMWW_9iay0X7ln04tgwXiFFLVg-2tQb32vVs8j30cJZ7Hc5HjEY7rvNg5cowgCVJhM9N_K58W_kGkQRiQ_wjHPkIdh-FoA8BZqkF" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 3</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and let's start to think about how the patient's possibile </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">I</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) might modify the curves (Figure 4).</span></p><br /><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 257.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 323px; overflow: hidden; width: 624px;"><img height="323" src="https://lh3.googleusercontent.com/hjwVCdYpXEiUZjQH_AZNYaSKQfBE5Q55EJ2napbYHy-M3kbMdTgqWkvumrWFvfgZNm0p2VkQQCMjvVw39_vQfS88HYBdMXm86ykMjk1tJX0QDasVicVFqW-YtBHyR7vDQtM6Oq0k" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 4</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">With the RESPIRE method (which has a physiological basis which we are not going to discuss here for the sake of simplicity), the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient’s inspiratory activity “attracts” the curves</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> towards his position: it </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">“raises” the flow trace </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">“lowers” the pressure trace </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">compared to what we would expect.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In case of patient’s activity, the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">variations in flow and pressure </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">must both </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">agree with each other</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, meaning that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">both</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> traces have to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">“move towards”</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">“move away”</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> from the patient. Patient’s activity could be evident on </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">one of the two curves only</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: only on the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">flow</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> trace during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ventilator’s expiratory time</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">on flow or pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (depending on the mechanical ventilator in use) during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ventilator’s inspiratory time</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. If the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">variations of flow and pressure are not in agreement</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, meaning that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">one curve “moves towards” while the other “moves away” </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">from the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, this can </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">never be attributed to the patient's activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Looking at </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory flow</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">area shown in Figure 4</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (“insp”), we can see a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">little flow increment </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">compared to what we would expect (the curve moves towards the patient). If this was due to patient activity, the airway </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">should decrease</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (move towards the patient) or </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">stay unchanged</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In this case we can see that, in the highlighted area, airway </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure is slightly higher</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> than what we can see in other parts of inspiration (it moves away from the patient) and, using RESPIRE, we attribute this condition to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">When flow and pressure suggest antithetical respiratory activities</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (inspiration on the flow trace, expiration on the pressure trace) we can </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">exclude</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that this can be attributed to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient's activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: we can therefore conclude that, on these images, there is no patient’s inspiratory activity.</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The next step is to search for the moments when </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure remains constant </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">flow is absent</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">R</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: release/relaxation): this is the only condition during which the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> measured by the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ventilator </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">becomes </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the same</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> as the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure in the lungs</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 257.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 323px; overflow: hidden; width: 624px;"><img height="323" src="https://lh5.googleusercontent.com/9owJFIKE7MksSQWksrh_b_45UVHLMpmibEydiXQcYS9NZSit8TXmYXeB3KngNAZb1UTGmOSRBCTrNbVn4PPgsOe6cOHU7swxiYFRQmcfC6bJowPf8DeEnmnOPPfhOl5Ynu54RsuG" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 5</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The phase without flow at a constant (although there are small oscillations) pressure can be seen at the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">end of inspiratory flow.</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> The pressure value in the mechanical ventilator is 23 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (Figure 5), which is the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure in the patient’s lungs at the end of inspiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> if it is</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> obtained in the absence of any patient’s expiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (we have already excluded the presence of any inspiratory activity in the previous step).</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We are going to end this analysis by trying to find the patient’s </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory activity (E).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In Figure 6 and 7 we can see two </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">short, minimal but obvious drops in flow</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, one during inspiration and one during expiration.</span></p><br /><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 257.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 323px; overflow: hidden; width: 624px;"><img height="323" src="https://lh4.googleusercontent.com/JaOJKLMl_19rtK7qo0xtG0Xud7VccNgmVnTS4yFI0nKuhUMxGjXUXUDHTAN-hWRLDfjlX5loFX2kigk2i5LXciGHVHin7M_R8S2ja5vzJz4KYvIdD1BALzGAfagQk_V07rKXdLyz" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 6</span></p></td></tr></tbody></table></div><br /><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 257.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-left: 24pt; margin-right: 24pt; margin-top: 0pt; margin: 0pt 24pt 6pt; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgQ7Hjfm8MQBxSW-aXAuYEO1I-_yV_4DkUr0nHitsEHlNJiJjqZRw8Adpr1kLepRqL7v3D6vaVDPkozKKAhus8FEcyTIKspWPlnh4oFW4ZiOOtjpFHQJALDxwA6avbyEVtTTRSEbw8Jvg3wzgfHdJ7BwQckZRB1ZmeRrD9URtCud1oNvsSDalmk-YDQPQ=s1642" style="text-decoration-line: none;"><span style="background-color: transparent; color: #660000; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 323px; overflow: hidden; width: 624px;"><img height="323" src="https://lh6.googleusercontent.com/UonNwhMf0vrjq_Re3QAgNfMPeXFlILJ04AbFKydRLPqaKIz7geKn7z--6MJbHm16qn4axODZywPJgfr3JIjqbwZhJHl1PNzAJUR9CB6aGMKAFw6AAV0rOZqCKwz7ecoOM1KieDfp" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></a></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-left: 24pt; margin-right: 24pt; margin-top: 0pt; margin: 0pt 24pt 6pt; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEgQ7Hjfm8MQBxSW-aXAuYEO1I-_yV_4DkUr0nHitsEHlNJiJjqZRw8Adpr1kLepRqL7v3D6vaVDPkozKKAhus8FEcyTIKspWPlnh4oFW4ZiOOtjpFHQJALDxwA6avbyEVtTTRSEbw8Jvg3wzgfHdJ7BwQckZRB1ZmeRrD9URtCud1oNvsSDalmk-YDQPQ=s1642" style="text-decoration-line: none;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure </span></a>7</p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In both cases, we can see at the same time a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">rise in pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. They appear therefore to be signs of the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient’s expiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The oscillations in airway pressure are frequent and regular: we can see 13 of them in the 7 seconds of recording (Figure 8), corresponding to about 110 oscillations per minute. </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 218.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 7pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 272px; overflow: hidden; width: 624px;"><img height="272" src="https://lh4.googleusercontent.com/LYgM9wMRZU4zWnu21mP1hHYQs5JJu6dinQ4nXMQ1HZgDchSFHRl7zmmobqHxIN4bIkVxY7OWlo0KXe6rBP3l_ieLxSVzE0xkQenU2WGufLjzI7ubzOyPrshx3WIjwn3Qpsr51QD6" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 7pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 8</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This was very similar to the patient’s heart rate. We have to conclude that the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure variations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (and minimal flow variations) are </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cardiogenic oscillations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, meaning that they are induced by the patient’s heart beat. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This gives rise to two interesting considerations: </span></p><ol style="margin-bottom: 0px; margin-top: 0px; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Cardiogenic oscillations </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">are expression, to all effects, of the </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient’s respiratory activity</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which </span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">originates from the patient’s heart beat instead of originating from the activity of the patient’s respiratory muscles</span><span style="font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p></li></ol><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Cardiogenic oscillations </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">induce</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> the variations of pressure in the lung, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">which are</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> behind pressure and flow variations.</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> This is just like the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory muscles</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which generate alveolar </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure variations </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(although of much greater entity) in order to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">originate airway flow.</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> For this reason, RESPIRE identifies cardiogenic oscillations as patient’s respiratory activity, and don’t make a distinction between the heart or respiratory origin since they have, from the mechanical point of view, the same impact.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2) The mechanism behind cardiogenic oscillations is far from trivial. If we observe them in Figure 8, the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">positive peaks</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> generated by </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cardiogenic oscillations on the airway pressure trace </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(where you can see the dashed white lines) </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">remind us</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of vascular pressure peaks during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">systole</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Beyond their </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">morphology</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, their </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">duration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is more in agreement with the lesser duration of systole compared to diastole.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If we think carefully, matching the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">peaks due to cardiogenic oscillations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> with </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">systole</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">contradiction </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">with the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">variation in heart volume</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: in fact, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">during systole</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the heart volume decreases</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, therefore its imprint on the lungs should decrease, generating a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">small pulmonary expansion</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and a subsequent </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction in intrapulmonary pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: just the opposite of what we have observed in our case.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Nonetheless, during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">systole</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">intrathoracic vascular volume increases</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and the p</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ulsatile wave of the pulmonary artery is transmitted</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to gas contained in the airways.</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> Both these mechanisms </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">increase the vascular imprint on aerated spaces and therefore<b> i</b></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ncrease the intrapulmonary pressure during systole</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Cardiac contractions</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pulmonary artery pulse</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> induce</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> volume and pressure variations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">of opposite sign </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">on the alveoli.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The direct effect of the heartbeat manifests itself clearly on the iuxta-cardiac lung areas (especially on the lower left lobe), while in other areas of the lung the variations have an opposite direction compared to the inferior left lobe (1, 2). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This data can be consistently interpreted as follows: in the lower left lobe, the prevailing mechanism is that of the direct compression-decompression of the heart on the lungs, i.e. the heart volume reduces in systole and the lung parenchyma expands in systole while the opposite happens in diastole. In the other areas of the lung the direct transmission of the heartbeat is not relevant, but the systolic increase in intrapulmonary blood volume and the direct transmission of the arterial pulmonary blood vessels’ pulsatile wave becomes significant, with an increase of compression of lung aerated spaces in systole and their decompression in diastole. The total net effect sees the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">prevalence of the impact of pulmonary artery pulse on heart contraction</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, as we can perceive from our case-study by observing a systolic peak on airway pressure.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This interpretation is confirmed by the observation that the cardiogenic oscillations persist with an open chest cavity, when the heart is not in direct contact with the lungs and that they are eliminated by clamping the pulmonary artery while the heart is still beating (3).</span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s finish our analysis of expiratory activity by focusing our attention on the last very evident difference between the hypothetical curves obtained with a passive patient and the ones effectively recorded. During the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory phase, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">we can see that the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> stays well</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> above the applied PEEP level </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">for a long time, and that PEEP level is reached only at the end of expiration (Figure 9). </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 257.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 323px; overflow: hidden; width: 624px;"><img height="323" src="https://lh5.googleusercontent.com/rdH4Mvr-uyhqmh3lXP26K0K2HU1O18X7rE-LiACoAc8M4-X3ovbvcz7upFyINTA1586HeLDjf8s1dJKejCZqhqfyGDcb7WDRhQmHQffUh4K3buhm_zb9MUG3Tcqp-ANeSFB-ij_t" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 23.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 9</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This behaviour is definitely abnormal, and it could be due to the</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> expiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of the patient </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">only if </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">it were associated with an </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase in expiratory flow</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which we do not see. The</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> flow decreased exponentially during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the entire </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiration, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">as usually happens for passive patients. Moreover, we can see that the absolute value of the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory flow’s peak</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is significantly </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lower </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">than the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory flow’s peak. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This confirms the fact that it is unlikely that this could be due to the patient’s expiratory activity, since it would eventually increase the expiratory flow’s peak.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">In absence of any expiratory activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we must conclude that an </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiratory airway pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">higher than expected </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is due to a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">problem in the ventilator. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We will discuss this extensively in a future post. </span></p><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In conclusion, our analysis of patient-ventilator interaction shows that </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">any respiratory muscles’ activity is absent for the entire duration of the respiratory cycle</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is completely </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">passive</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There is a</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> patient’s activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which can be seen on the graphical monitoring, and which is due to the heartbeat (the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cardiogenic oscillations)</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cardiogenic oscillations are indistinguishable</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, when using </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">RESPIRE</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, from </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient’s activity </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">because they are</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory movements generated by intrathoracic pressure variations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: only their </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">small impact</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> on flow and airway pressure, which is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">frequent</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">regular</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> present in all the phases of the respiratory cycle,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> lets us </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">discriminate cardiogenic oscillations from respiratory muscles’ activity</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">While waiting to discuss what really got my attention while examining this case, I send a smile to all of </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">’s friends, as always. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">References</span></p><ol style="margin-bottom: 0px; margin-top: 0px; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 12pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Collier GJ, Marshall H, Rao M, Stewart NJ, Capener D, Wild JM. Observation of cardiogenic flow oscillations in healthy subjects with hyperpolarized 3He MRI. J Appl Physiol 2015; 119:1007-1014</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Dubsky S, Thurgood J, Fouras A, R Thompson B, Sheard GJ. Cardiogenic airflow in the lung revealed using synchrotron-based dynamic lung imaging. Sci Rep 2018; 8:4930</span></p></li><li aria-level="1" dir="ltr" style="font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.38; margin-bottom: 15pt; margin-top: 0pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Suarez-Sipmann F, Santos A, Peces-Barba G, Bohm SH, Gracia JL, Calderón P, Tusman G. Pulmonary artery pulsatility is the main cause of cardiogenic oscillations. J Clin Monit Comput 2013; 27:47-53</span></p></li></ol><p dir="ltr" style="background-color: #fcfcfc; line-height: 1.92; margin-bottom: 0pt; margin-left: -1pt; margin-right: -1pt; margin-top: 20pt; margin: 20pt -1pt 0pt;"> </p><br /></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-30063275123221131552022-01-08T20:15:00.000+01:002022-01-27T09:17:36.257+01:00Ventilation modalities and graphical monitoring<p><a href="https://www.ventilab.it/2022/01/modalita-di-ventilazione-e-monitoraggio.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Original post</span></a><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> published on 8</span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">th</span></span><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> January 2022 by Giuseppe Natalini</span></p><span id="docs-internal-guid-eeb829dd-7fff-d5d0-661d-4a77087277ab"><p dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-align: center;"><span style="font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 239px; overflow: hidden; width: 320px;"><img height="239" src="https://lh6.googleusercontent.com/kUR8JtBowrz2BiTl4PPqajnyM0-ziNCI4W_Zdx_Pb7CmugnzTtwJToegE9TF5AFFTmGZUTWSmqQV2r0nmKEDJDE83J4bWQhOAp27yvSF5pACmPuVmjafr_-wjm7SFKXa0Aeh5vVa" style="margin-left: 0px; margin-top: 0px;" width="320" /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Last week I published a</span><a href="Mechanical ventilation's graphical monitoring analysis" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">7 second long strip </span><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">showing </span><span style="color: #1155cc; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">pressure and flow curves</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">from a mechanically ventilated patient, asking you to anonymously suggest an interpretation. This week about a thousand people have read the post, and fifty people have given their own interpretations on the traces.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">I read with great attention all the answers, and I noticed one thing: almost all of ventilab’s readers have focused their attention on aspects which were different from the one I had planned to discuss. It’s amazing how many things only 7 seconds of pressure and flow curves monitoring can tell us! I am really happy to have let you express yourselves on the matter before I did. Listening before talking lets me offer different levels of interpretation for this short strip, making the discussion more exhaustive.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">I have decided to publish a series of close up posts in which we will evaluate all the considerations that ventilab’s readers have written on the form from </span><a href="https://www.ventilab.it/2021/12/analisi-del-monitoraggio-della.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">29/12/2021</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">’s post. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">I will leave the post explaining why this monitoring has attracted my attention and how this permitted me to find and solve the problem for last.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Today we will see what these </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">7 seconds</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can tell us on the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">modality of ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and on the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ventilator's settings</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">What is the ventilation modality and what are the ventilator settings? </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Recognizing</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> ventilation modality </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ventilator settings </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">from graphical monitoring (that is to say, from </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">simple pressure and flow traces) </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">means to have </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">truly understood mechanical ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It is an exercise that I suggest to ALWAYS do: it's the only way to</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">reach an understanding of the real way mechanical ventilation works, overcoming the blanket of smoky clouds that often is an obstacle to correct interpretation.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-align: center; vertical-align: baseline; white-space: pre-wrap;">Figure 1 shows the original image:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-align: center; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 265px; overflow: hidden; width: 624px;"><img height="265" src="https://lh3.googleusercontent.com/oiUNg_rQxvQtx1wYQ2qpLkWBZHA6VUgTWF7RdV7UCS8SLo8_nf8AUChDFyMETFFvIOmB5iyynQwyW0MYufoSVgQ5nVwOhYHma98rAioEV73ZdfiYWi1IIORTilZeN2W4UYL4euJp" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt; text-align: center;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Ventilator settings have been estimated as an </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> approximately between </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">25 and 28 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP between 5 and 7 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: reasonable answers, since from the images it was not possible to be more accurate. In reality, applied pressure was 24 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O and PEEP was 6 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It was noted that the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">duration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">expiration</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">similar</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, therefore </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">I:E ratio is 1:1 </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory rate</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is around</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 25 breaths/minute. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Calculation of respiratory rate is simple: in about 7 seconds we see almost 3 breaths (only the last part of the expiration is missing from the last breath). Dividing 7 seconds by 3 I obtain the d</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">uration of a single breath </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(2.33”) rounded down, I then round it up to </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">2.4”</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. If a breath lasts about 2.4”, respiratory rate is about 25 breaths/min, with an </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory time of 1.2” </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and an expiratory time lasting the same. Having said that tidal volume was 230 ml, minute ventilation was</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 5.75 l/min.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">proposed ventilation modalities</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> were: </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation, pressure-controlled ventilation, volume-targeted pressure-controlled ventilation, assisted-controlled pressometric ventilation, APRV.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">All</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> these answers </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">might be right</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, but only one </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">is certainly correct</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: the set ventilation is generically a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and there are no elements that permit answering more precisely. Pressometric ventilation is characterized by </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">constant inspiratory pressure and decreasing inspiratory flow, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and both of these features are present, as you can see in the “insp” portion of Figure 2:</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 220pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 273px; overflow: hidden; width: 624px;"><img height="273" src="https://lh6.googleusercontent.com/uD2OqlYxebBMrUheeDTfRlFkiW2UjhyGx6l18wZyQ6M49GtVdHPD-1s5g5sHmrJuJb19tee1gFyzd1waJhAFKiwXqeQr8M7Ne4dXgSTzOlx6Vg5hlF0kxWleergR7HHCK2ZxEmKw" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 26.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">These characteristics are common for all the pressometric ventilations. Since </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">all ventilation modalities except volume-controlled, NAVA and PAV are pressometric</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we haven’t taken such a big step forward.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Another consideration arises from this one:</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> if almost all ventilation modalities are pressometric</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> does the modality of ventilation really matter? </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As those of you who have followed some of our courses well know, I believe that the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">modality has little importance</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, but its </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">correct setting</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">prime importance</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In other words, a patient can be managed indifferently well with different ventilation modalities if for each one of them the ventilation parameters are set well. At the same time, a patient can be inadequately ventilated using each ventilation modality if its settings are not appropriate.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">To say that a patient is ventilating with pressure support ventilation (or any other modality) is an information that has little value unless we specify how much support is applied, how much tidal volume and respiratory rate are generated, what does the flow profile look like, if any asynchronies are present and eventually which ones, how is the thoraco-abdominal coordination, if accessory inspiratory muscles are being used.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Going back to our clinical case, we can say that this ventilation is pressometric. </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">In the family of pressometric ventilations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we can exclude one with certainty: </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure support </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilation. This is because </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">during </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> inspiratory time</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> we can see a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pause</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">can NEVER exist during pressure support </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilation because flow cycling makes sure that inspiration ALWAYS stops when there is still inspiratory flow (see </span><a href="https://www.ventilab.it/2017/12/il-vero-significato-del-trigger.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">27/12/2017</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">From the images we cannot tell </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">if it is a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure-controlled</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">volume-targeted pressure-controlled ventilation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (called PCV-VG, PRVC, IPPV with autoflow, APV, PC-target vent, volume adaptive BiLevel, et cetera in different ventilators): in case of a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">passive patient,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the two ventilations are </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">indistinguishable</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> using graphical monitoring since they are </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">both pressure-controlled ventilations</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">difference </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">can be seen only by looking at the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">settings panel</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure-controlled </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilation you </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">set the applied pressure</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (and the tidal volume is variable), while in </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">volume-targeted pressure-controlled ventilation </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">you set</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> desired tidal volume</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and the ventilator does a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">variable pressure-controlled v</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">entilation, changing constantly the applied pressure in order to obtain the desired volume. In our example, it was a volume-targeted pressure-controlled ventilation, that is the desired tidal volume was 230 ml.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Assisted-controlled </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation is a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">controlled </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">pressometric ventilation in which the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">trigger is activated</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">by the patient</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Can you see trigger activation in Figure 1? If so, it is an assisted-controlled ventilation, if not it is a controlled ventilation. Patient-ventilator interaction will be discussed in the next post. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Finally </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">APRV (Airway Pressure Release Ventilation) </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">was suggested as a possible set ventilation modality (for more information see the </span><a href="https://www.ventilab.it/2015/02/airway-pressure-release-ventilation.html" style="text-decoration-line: none;"><span style="color: #660000; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">11/02/2015</span></a><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post). </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">APRV is a BIPAP,</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> meaning that it alternates between </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">two pressure levels</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that let the patient spontaneously breathe in any phase. In other words, it is the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">alternation</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">two CPAPs</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Differently from BIPAP (which is defined as a partially asynchronous ventilation), </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">APRV</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> should be completely </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">asynchronous, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">not taking into account the patient’s spontaneous breathing activity in the </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">rythmic alternance </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">between a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">higher pressure (P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">high</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">) </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and a </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lower pressure (P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">low</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">). </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The rationale behind this approach is interesting (synchronicity is not always good), and we can discuss it in comments if you find it interesting.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Typically, </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">APRV should</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> be set with a significantly </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">longer time at</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">high </span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">than at </span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">low</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. If the ventilation shown in Figure 1 was an APRV, P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">high</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (which would coincide with “insp” in Figure 2) would be 25-28 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O and P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">low </span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(which would coincide with “esp” in Figure 2) would be 5-7 cmH</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O, and both would last 1.2”: a possible choice, even if not typical for APRV. The ripples seen on the pressure curve at P</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">high</span></span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> would have to be interpreted as signs of the patient's spontaneous respiratory activity. As we have said before, the set ventilation was a volume-targeted pressure-controlled ventilation, but from the shown image it was reasonable to think it was an APRV.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Here we end our exercise involving reading mechanical ventilation from flow and pressure curves. We will go on next week by discussing the many comments you made on patient-ventilator interaction.</span></p><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As always, a smile for all of </span><span style="font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">’s friends.</span></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-18445400355734084942021-12-29T20:26:00.000+01:002022-01-27T09:17:17.351+01:00Mechanical ventilation's graphical monitoring analysis<a href="https://www.ventilab.it/2021/12/analisi-del-monitoraggio-della.html" target="_blank">Original post</a> published on 29<span id="docs-internal-guid-44aebb8b-7fff-2d6b-e516-a347e603a847"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">th</span></span></span> December 2021 by Giuseppe Natalini <div><br /></div><div><br /></div><div><br /></div><div> You can see the image in the form below. Please comment (answers are anonymous) and click “Submit” to send your answers.
I will use your answers to decide how to present my comment on this image, which I will publish in about ten days.
In the meantime, I wish a happy New Year to all of <i>ventilab</i>’s friends. A smile to everyone.</div><div><br /></div><div>
<iframe frameborder="0" height="855" marginheight="0" marginwidth="0" src="https://docs.google.com/forms/d/e/1FAIpQLSdQgQolapn1PGsJQp8EE-eBDaCNY6Hi6K2_1t6GnbMN1_ki4Q/viewform?embedded=true" width="640">Loading…</iframe> </div><div><br /></div><div><br /></div><div> Form questions:</div><div> 1) Which information can you obtain from the analysis of these traces? (the trace is about 7 7 seconds long and the tidal volume is around 230 ml)</div><div> 2) Do you think there is a problem? If so, which one?
</div>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-46719306488331407992021-07-31T16:44:00.000+02:002022-01-27T09:16:57.666+01:00Respiratory alkalosis and respiratory acidosis in mechanically ventilated patients: when to treat them and when to accept them.<span id="docs-internal-guid-06b79b09-7fff-5126-6fa1-d865d9cec88f"><h1 dir="ltr" style="background-color: white; line-height: 1.38; margin-bottom: 0pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt; padding: -2pt 0pt 19pt 0pt;"><span style="font-size: small;"><span style="background-color: transparent; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline;"><span><a href="http://www.ventilab.it/2021/07/alcalosi-respiratoria-e-acidosi.html" target="_blank">Original post</a> published on </span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">31</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;"><span style="vertical-align: super;">st</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;"> July 2021 by Giuseppe Natalini</span></span></h1><div><span style="font-size: small;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;"><br /></span></span></div><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt; padding: 0pt 0pt 19pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 224px; overflow: hidden; width: 400px;"><img height="224" src="https://lh3.googleusercontent.com/9sWsLI6zMfaPAQFtgN7JOI1NUySquoEPHPflldnmQafHy-6xLO9a1OQVmok8S1KeGIaX08xCVsurzFN4MGYDgABneCpkhm-1XyNiDz0MgLgtH5N8dIlFTgeDNRU7_qPMf8RTL6Gu" style="margin-left: 0px; margin-top: 0px;" width="400" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt; padding: 0pt 0pt 19pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Should </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">avoid respiratory acidosis or respiratory alkalosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">? </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt; padding: 0pt 0pt 19pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As is often true in medicine (and in life…) the answer to this question cannot be a simple “yes” or “no”, but requires a more articulate approach. The answer is in fact different in case of acidosis or alkalosis and if the mode of mechanical ventilation is controlled or assisted. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 19pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt 19pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">I am going to anticipate the conclusions in Figure 1, which I will then try to justify. </span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 145pt;"><td style="overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 25pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt 25pt; text-align: center;"></p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><br /></div></div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/a/AVvXsEjfjQXvxd8l4l4JBjq0KYMORwZ2Xpn1ZEjy94GLb-YzM3H9kZjVm5cUUSgVJaamMYszlJkBjOMzKG1opSj5jPo9whbAKAur_L8K2EhrCK2dlk2eJATd_NLNCnTBNblcxgg7mRvTfqgob8dMLO_SFEmmQ_Oi4PKb-16Y4YmV2F9MBj3ud1Lqi6DptsJP=s441" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="216" data-original-width="441" height="258" src="https://blogger.googleusercontent.com/img/a/AVvXsEjfjQXvxd8l4l4JBjq0KYMORwZ2Xpn1ZEjy94GLb-YzM3H9kZjVm5cUUSgVJaamMYszlJkBjOMzKG1opSj5jPo9whbAKAur_L8K2EhrCK2dlk2eJATd_NLNCnTBNblcxgg7mRvTfqgob8dMLO_SFEmmQ_Oi4PKb-16Y4YmV2F9MBj3ud1Lqi6DptsJP=w526-h258" width="526" /></a></div></div><p></p></td></tr><tr style="height: 20.5pt;"><td style="overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 25pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt 25pt; text-align: center;"><span style="color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p></td></tr></tbody></table></div><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 12pt; padding: 0pt 0pt 31pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In this post, when we say acidosis and alkalosis we mean uncompensated disorders of acid base equilibrium, i.e. conditions with pH < 7.35 (acidemia) or pH > 7.45 (alkalemia).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s be reminded that </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mechanical ventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is called </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">controlled </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">when the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient does not contribute in any way to ventilation:</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the detected respiratory rate is the same as the set respiratory rate, there are no signs of inspiratory trigger nor of inspiratory activity during inspiration. Ventilation is called </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">assisted</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> when </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the respiratory rate, at least, depends on the patient</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: in this instance, inspiratory trigger activation can be seen and the detected respiratory rate is higher than one set on the ventilator.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let's start to examine the four cases summarized in the table in Figure 1. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: 0pt 0pt 19pt;"><span style="background-color: transparent; color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">RESPIRATORY ALKALOSIS DURING CONTROLLED VENTILATION </span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 31pt; margin-right: 11pt; margin-top: 0pt; padding: -7pt 0pt 0pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This case is the simplest to understand and solve. </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Hypocapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which is at the basis of respiratory alkalosis, is a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">consequence of mechanical ventilation only, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and the patient suffers passively its </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">deleterious effects</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which are </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">vasoconstriction </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">systemic</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> circulation and a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">oxygen release to tissues</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> due to the leftward shift in the haemoglobin dissociation curve (Figure 2).</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 386.5pt;"><td style="overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 25pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt 25pt; text-align: center;"><span style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 491px; overflow: hidden; width: 624px;"><img height="491" src="https://lh5.googleusercontent.com/I3DHNqluQyULmjrvQXSrMYfQZvXuOWV0D1t-SCShLiftR2gGWU4BYk1wQ-Efajpx8u-xQIAxO5K0mFqJOoenKP6f8E3uPnPqU8GoLpbkbdotwK-hwYpZh1vD63OAidmk4-xoeKt1" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 20.5pt;"><td style="overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.38; margin-bottom: 25pt; margin-left: 11pt; margin-right: 11pt; margin-top: 0pt; margin: 0pt 11pt 25pt; text-align: center;"><span style="color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span></p></td></tr></tbody></table></div><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 12pt; padding: 0pt 0pt 31pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The consequences can be </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tissue ischemia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> hypoxia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which are especially fearsome for the brain and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">myocardium</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This respiratory alkalosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> must be avoided</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and this is easy to do: it is sufficient to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">limit tidal volume </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">to 6-8 ml/kg of ideal body weight and, in case of persisting hypocapnia, to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduce respiratory rate</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> as much as is needed to reach and acceptable range of pH and PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (for example PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> > 30 mmHg and pH < 7.5).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: 0pt 0pt 19pt;"><span style="background-color: transparent; color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">RESPIRATORY ALKALOSIS DURING ASSISTED VENTILATION </span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -7pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In this condition, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypocapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">consequence</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of an increased </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">activity of the respiratory centers</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (Figure 3).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="border: none; display: inline-block; height: 349px; overflow: hidden; width: 246px;"><img height="349" src="https://lh3.googleusercontent.com/04TP-QFyZ0v4nnJ_bky3LMTAtyr5NCwYTVs9V6GQwkdRQtyCoWKZ-z5pnK31qeqHPrX-4qEXB4opey7OEGX4zobltz4sKsjME2ckd1knoOMiP2T76QBnWyG_jpJyoDS9E0qsZn1r" style="margin-left: 0px; margin-top: 0px;" width="246" /></span> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><br /></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 3</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 9pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Any modification in mechanical ventilation settings cannot solve the problem: a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction of inspiratory support</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (or, even worse, a reduction of the inspiratory trigger sensitivity) will only cause an</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> increase in the inspiratory effort </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">that the patient has to generate in order to maintain the level of ventilation that the respiratory centers command. If a reduction of inspiratory assistance were to decrease </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, it would be a sign that </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory muscles are fatigued </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and have</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> surrendered,</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> since they are not adequately assisted anymore</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">. </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In other words, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">is going to increase</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> only when the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">exhausted</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> from the effort to breathe.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The only reasonable weapon we have to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in a patient with </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory alkalosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">assited ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pharmacological reduction </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> activity </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory centers, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">using </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">sedation. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Is it worth it? Often it is not, and we’ll try to understand the reasons.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">One of the most </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">fearsome effects</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypocapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> cerebral vasoconstriction</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">should not be a problem</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> assisted ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">acidity of cerebrospinal fluid (CSF) pH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the main </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">stimulus </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">for </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">breathing centers</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, therefore it is the main cause of</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> hyperventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypocapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There are also other breathing centers stimulants (cortical and peripheral), but usually their importance is secondary compared to the importance of H</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">+ </span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">concentration in CSF. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We can reasonably think that a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypocapnic</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> subject in </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">assisted ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> has CSF acidosis (a high concentration of H</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">+</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) which stimulates breathing centers, and that</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> arterial blood hypocapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">consequence</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hyperventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The presence of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">CSF acidosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is an excellent </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">antidote</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> against </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cerebral vasoconstriction</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">induced by</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the opposite condition, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">CSF alkalosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (a low concentration of H</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">+</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in the CSF).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">CSF acidosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">frequent </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inflammatory, hemorrhagic and ischemic brain conditions</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which are the conditions in which, during assisted ventilation, respiratory alkalosis is usually observed.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The absence of cerebral vasoconstriction can be confirmed by a neurological examination: presence of good </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">vigilance</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or of</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> unimpaired mental status</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> should exclude a significant brain hypoperfusion. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We have to be aware of the fact that</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory alkalosis in the arterial blood</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, even if it is without deleterious effects on the brain, maintains its </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">systemic extracerebral side effects</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, independently from CSF pH. It could be an </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">unfavourable condition</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patients</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> at risk of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">coronary hypoperfusion</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or in presence of signs of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tissue hypoxia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. We can therefore </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tolerate hypocapnia and respiratory alkalosis </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in patients undergoing </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">assisted ventilation if the risk</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">myocardial</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (or other </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">organs </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">or </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tissues</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypoperfusion is absent.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: 0pt 0pt 19pt;"><span style="background-color: transparent; color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">RESPIRATORY ALKALOSIS DURING CONTROLLED VENTILATION</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -7pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In case of r</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">espiratory acidosis during controlled ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we can </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase minute ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> if it does </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">not expose</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the patient </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">to</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">risk of ventilator induced lung injury</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, for example by keeping driving pressure below 15 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O and stress index around 1 (see </span><a href="https://www.ventilab.it/2015/02/peep-fio2-pao2-e-compliance-nella-ards.html" style="text-decoration-line: none;"><span style="background-color: transparent; color: blue; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">28/02/2015</span></a><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">If </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">this is</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> not possible</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we can </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tolerate hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which has many favourable physiological effects, such as the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase in cardiac output</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, in oxygen delivery and in the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">transfer of oxygen to tissues </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(shifting to the right the haemoglobin dissociation curve).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Due to these effects, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory acidosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is generally well </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tolerated </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">from the physiopathological point of view (surely </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">much more than hypocapnia)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: 0pt 0pt 19pt;"><span style="background-color: transparent; color: #2b00fe; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">RESPIRATORY ACIDOSIS DURING ASSISTED VENTILATION</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -7pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Respiratory acidosis during assisted ventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">should </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">always be avoided</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, because it is a sign of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">insufficient inspiratory support</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> for </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">weak or fatigued respiratory muscles.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This is true even if there is a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">physiological PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(around 40 mmHg) in presence of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">acidosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: it's not normal to have a normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> when there is acidosis, therefore this condition should also be seen as a sign of fatigue or weakness of the respiratory muscles.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In these cases the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> solution is simple</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increasing inspiratory support </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and, if this does not resolve respiratory acidosis, starting </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">controlled ventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">to</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> let respiratory muscles rest </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">temporarily.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Conclusion.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Respiratory acidosis and respiratory alkalosis can be tolerable or not, depending on the fact that they manifest during assisted or controlled ventilation. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">controlled ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, r</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">espiratory alkalosis is not acceptable</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, while during </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">assisted ventilation respiratory acidosis is not acceptable. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 31pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">On the contrary, hypocapnia during assisted ventilation and hypercapnia during controlled ventilation can be acceptable after evaluating their impact on other organs and parenchymas.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 31pt; margin-right: 11pt; margin-top: 0pt; padding: -19pt 0pt 0pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">A smile for all of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 14pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">’s friends, and happy holidays!</span></p><p dir="ltr" style="background-color: #fcfcfc; line-height: 1.92; margin-bottom: 19pt; margin-right: 10pt; margin-top: 20pt;"><br /></p><div><br /></div></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-35018949514248597682021-06-27T15:06:00.000+02:002022-01-27T09:16:27.217+01:00P0.1, respiratory drive and inspiratory effort<p><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><a href="http://www.ventilab.it/2021/06/p-01-drive-respiratorio-e-sforzo.html" target="_blank">Original post </a>written on 27</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">th</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> June 2021 by Giuseppe Natalini</span></p><span id="docs-internal-guid-5543f604-7fff-1300-c722-0a65d1bf86c1"><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-right: 12pt; margin-top: 0pt; text-align: center;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 320px; overflow: hidden; width: 240px;"><img height="320" src="https://lh4.googleusercontent.com/flyd6-PWBTwbiEjy_J_yEFaSzjuCvyznlcXYEAI86TJT6qxa_7AaUFP2SLkYaYuxUlYrKua7JSo5e3zpKCXGWPLEvejNWdw5VuCidhquUFgSLmtvyjzpdgT-dFsB6oJIWIeEbuw1" style="margin-left: 0px; margin-top: 0px;" width="240" /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Many mechanical ventilators show us, among measured values, a variable called P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (to be read as P-zero-one)*: </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">what is P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">?</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> What is its </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">physiological significance</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">? What is its </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">clinical use</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">? Today we will try to reach a clear answer to these questions, which are far from simple.</span></p><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Respiratory drive and inspiratory effort</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">intensity </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> activity </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory centers </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">located in the brain stem. In other words, it's the intensity of the stimulus to breathe, generated in the central nervous system (1).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increased </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">with </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">rising</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, in presence of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">severe hypoxia</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (PaO</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> lower than 50-60 mmHg, at least), with</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> pulmonary parenchyma</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inflammation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and/or </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">congestion</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, or with stimuli originating from the brain (</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pain, delirium, fear, anxiety</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). On the contrary, respiratory drive can be decreased with hypocapnia, drugs, and cerebral lesions.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Since it’s </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">impossible</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">measure </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the level of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">activity </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory center neurons </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">directly</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">, respiratory drive </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is quantified by analyzing the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">physiological signals that depend directly from it.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">An i</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ncrease in respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> translates in a more </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">intense contraction of inspiratory muscles</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and thus in a </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">greater pleural pressure fall</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. This is why the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory reduction of esophageal pressure is also a measure of respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. This is true in the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">absence of neuro-muscular alterations</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or of chest wall lesions which could damp the effect of respiratory drive on pleural pressure.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The use of i</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">nspiratory effort to measure respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> requires </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure monitoring</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Is there a way to have i</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">nformation on inspiratory effort</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (and therefore on </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) using </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> only? </span></p><br /><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> was born in 1975 precisely to estimate </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">drive </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">from </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (2). Joseph Milic-Emili, one of the most important respiratory physiologists of the twentieth century -who became a star in the world of respiratory intensive care at the end of the past century (3)-, is among the “parents” of P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">During </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous inspiration,</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> has an</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> inspiratory variation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which is clearly </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">smaller than </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the simultaneous reduction in </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, as you can see in Figure 1 (the inspiratory variation is identified by the distance between the dashed red lines).</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="517"></col></colgroup><tbody><tr style="height: 490pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 639px; overflow: hidden; width: 503px;"><img height="639" src="https://lh6.googleusercontent.com/ITSXnPUQgwPB-cBbjr2PEGgC6BG2p5oluSokI8T5ZtOb6E93oXDWHHPjUe44Uv9cGNudg1FHL-cSl7tJgeLlh_oxz96Vq8q9ki20Qrds4kbgNkYQf2LGzT0AR6KyvNhYpZF9tPAw" style="margin-left: 0px; margin-top: 0px;" width="503" /></span></span></p></td></tr><tr style="height: 31pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 17pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This happens if the air enters the lungs during inspiration. In case of an </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiration </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">against</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> occluded airways </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(with an end expiratory occlusion in ventilated patients or by closing nose and mouth of non ventilated patients), the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure variation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">same as</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the simultaneous </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">fall in pleural pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 17pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> you can see a</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> first inspiration</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> with open airways and a </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">second one</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> against </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occluded airways</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The airway pressure variation is indicated by dashed red lines.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 148pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 180px; overflow: hidden; width: 624px;"><img height="180" src="https://lh5.googleusercontent.com/Qzw1hkF06cfRWXlDrN5XxEWOKwVlIltktxb5MOn5KvOMsBaS7-mVzLvS-xglzGlyRVW_sSI_tFB0v2K7QLTCfR9FvfwTC_IcGd-TNr2hZJBpJ9-WMZWFIv6FBWaQNtrtTPre2cp3" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 31pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 2</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction in airway pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occlusion </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">becomes</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> the same </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">as the simultaneous </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction in pleural pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and therefore permits to use the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">drop of pressure in occluded airways </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">as a </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">measure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory effort </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and hence of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory drive.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">When </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airways</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> are</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> occluded</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory effort </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">stays </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the same as </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">the one of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">non occluded breaths</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">as long as</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the patient doesn't </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">perceive the occlusion</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and only at that point inspiratory effort starts to increase.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occluded airways pressure reduction</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can be therefore used </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">to have information on respiratory drive and inspiratory effort </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of non occluded breaths, </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">up to the moment in which the patient perceives the occlusion</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It has been shown that the pressure reduction of occluded airways is linear and constant for the first 250 milliseconds (i.e. 0.25 seconds) from the start of inspiration, while after this time the pressure variations become chaotic (Figure 3). It has been therefore hypothesized that respiratory drive in the first 0.25 seconds of an occluded breath is similar to that of non occluded breaths.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 332.5pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 420px; overflow: hidden; width: 624px;"><img height="420" src="https://lh6.googleusercontent.com/UxV-Ty5fdl6GYBE11EXeM8MgA-J1TjeDh-iSBx1QB2ZEjRMafz8SU5EUuvJA1gLvPlT5yye88MY-LdvZ4VwgMtkBQjbbcFmfQ3WETbbUBPJ1OQaYKAvc_Yj3d1CUJqVoxz77vgDz" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 31pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 3</span></p></td></tr></tbody></table></div><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Prudentially, a time of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">0.1</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">seconds </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">has been proposed as a safe</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> limit</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">in which the occlusion is not perceived by the patient</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, therefore the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure reduction</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occluded airways</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">first 0.1 seconds of inspiration</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is considered as an estimate of i</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">nspiratory effort</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (and therefore of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). This has been called </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or </span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway occlusion pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">To support this hypothesis, P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> at different PaCO</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2 </span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">levels was measured in healthy volunteers, by making them breath gas mixtures enriched with CO</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In all subjects,</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> increased with increasing PaCO</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, as is expected for respiratory drive (Figure 4).</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="477"></col></colgroup><tbody><tr style="height: 490pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 640px; overflow: hidden; width: 464px;"><img height="640" src="https://lh3.googleusercontent.com/OyUYDFGHujmU9oEuxUt6zsgtG1gmQzQiRAjZ0OQOi1uySMouQzBAwWiKgugQqZ-ZpSOV7wrRtcm5bIubSdrrGP3qEe0AsT3UkYOLFFd3gNEAOH3_-mRGKIWEYj70B6U1x7EWU59I" style="margin-left: 0px; margin-top: 0px;" width="464" /></span></span></p></td></tr><tr style="height: 31pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 4</span></p></td></tr></tbody></table></div><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Based on this data, </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> became a measure of</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In-depth analysis (optional). </span><span style="color: #444444; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="color: #444444; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="color: #444444; font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: differences and similarities with </span><span style="color: #444444; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="color: #444444; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">A small in depth analysis for those of you who managed to follow all the reasoning up to now (those of you who had difficulties can jump to the next chapter, </span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">“P</span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in practice”</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Recently, it has been proposed that </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">the whole</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> difference in airway pressure during occlusion </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(and not only that of the first 0.1 seconds), defined as </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, is an estimate of the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory reduction of pleural pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (4): airways are occluded at the end of exhalation and the entity of the inspiratory fall in pressure of the occluded breath is measured (Figure 5, black two-pointed arrow).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">You can see that the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> during the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occluded breath </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> greater </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">than the one during the previous </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">non occluded breath</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (red two-pointed arrow), while </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">similar</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to the simultaneous </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">fall in</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (as it should be). It has been calculated that an approximately constant </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">relationship </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">exists between </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ </span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(which, we repeat, is the same as the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure reduction</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">in the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">occluded breath</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) and the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure inspiratory variation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">non occluded breaths</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">reduction during non occluded inhalation is </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">66%</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (i.e two thirds) of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now we can understand how </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> estimate the entity of the fall in pleural pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> using, in both cases, airway occlusion.</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> The</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> only difference</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> between </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> e </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the way in which the problem caused by the fact that the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">occluded breath </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(which we use to get to know pleural pressure variations) is </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">deeper than non occluded breaths (of which we want to estimate inspiratory effort and respiratory drive)</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is solved.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> solves the problem </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">by analyzing </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">only the initial part of the occluded inhalation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, because it is only with the progress of the occluded inhalation that this becomes greater than the non occluded one. In Figure 5, I have drawn dashed blue lines on the slope of the initial section of the inspiratory pressure reduction of the occluded breath. I have put lines parallel to them also on non occluded breaths, both on airway pressure and on esophageal pressure: you can see that the slope doesn’t change between occluded and non occluded breaths, further supporting the fact that P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of occluded breaths follows the same variations of pressure in the first 0.1 seconds of non occluded breaths. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Instead, </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ΔP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">occ</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> finds the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">solution by resizing occluded inspiratory effort </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">to </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">two thirds of the value measured on occluded airways</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, because this is the magnitude of the increase in esophageal pressure variation induced by the occlusion.</span></p><div align="left" dir="ltr" style="margin-left: 0pt;"><table style="border-collapse: collapse; border: none;"><colgroup><col width="624"></col></colgroup><tbody><tr style="height: 259pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 324px; overflow: hidden; width: 624px;"><img height="324" src="https://lh4.googleusercontent.com/pZkbsa0jQxn6E85g2ucenb2vBO8eQSEKQv_yYIozArKKj7y4KS8inmDvIOj_R-VyQTM--HX-1oJMtnRIap8DI5eY5vORTyv7MQIdIOfkABPjYS2VffYW136Z2QL5C8cQjqYzHYSz" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span></p></td></tr><tr style="height: 31pt;"><td style="background-color: white; overflow-wrap: break-word; overflow: hidden; padding: 5pt; vertical-align: top;"><p dir="ltr" style="line-height: 1.92; margin-bottom: 6pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #222222; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figura 5</span></p></td></tr></tbody></table></div><br /><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in pratice</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">How can P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> be used in the care of subjects undergoing mechanical ventilation?</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, since its origin, has been tested mainly with two objectives: during </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">weaning from mechanical ventilation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and to estimate the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory workload</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory muscles </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">during mechanical ventilation.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> has shown to be </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">of little utility</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (5,6) as a predictor of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">weaning </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">from mechanical ventilation, after an initial enthusiasm. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">On the contrary, P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> has repeatedly shown to be related to inspiratory workload </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">during mechanical ventilation and to its variations due to the variations of inspiratory assistance and PEEP</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(7-11). </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In particular, it has shown a good ability in identifying patients whose</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory muscles are maintained at excessive rest during assisted ventilation </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(when </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> is less than 1 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O) or </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">patients in which the</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> workload is excessive </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (when </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> is greater</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> than</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 3-5 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) (7).</span></p><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Limits of P</span><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can be used in concert with the other evaluations used to set inspiratory assistance, but it cannot be followed acritically because it has some important limitations.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">First of all, the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> which is measured automatically by mechanical ventilators</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> really imprecise</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> when compared to the effective value (about </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">± 2 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) (7,12). This approximation is anything but negligible, since the diagnosis of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inappropriate respiratory muscle activity</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is made on a really small difference in </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Moreover, in subjects with respiratory muscle weakness we could have a </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">low</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(≤ 1 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O) in presence of insufficient</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> inspiratory support</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. We would make the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">wrong choice</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> if, in this case, we </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lowered the inspiratory support </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">because of a low P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Lastly, we should consider that the</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> threshold to identify an excessive inspiratory effort </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(between </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">3 ed i 5 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">) is really </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">wide</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> compared to the accuracy of the measurement and </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">does not permit us to identify this condition with certainty. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="color: #2b00fe; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Conclusions</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">At the end of this post we can summarize the main concepts:</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory effort</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is an</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> expression </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and can be therefore used to </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">estimate it</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, measured on </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">airway pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">is an estimation</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> the entity of the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">first part</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory reduction</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which is </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">proportional</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the pressure developed by the respiratory muscles</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. For this reason, </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1 </span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is an indicator of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory effort</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">values </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">equal or less than 1 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can suggest that the </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">activity of respiratory muscles</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">a lot reduced,</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and therefore that a </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction in inspiratory support</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can be considered. This should not be taken into consideration if the patients seems to have respiratory muscle weakness or fatigue. </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> - a </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> greater than about 3-4 cmH</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> could be a sign of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">excessive respiratory muscle workload</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, inducing us to evaluate the possibility of </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increasing</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiratory support </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">or pharmacologically </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reducing respiratory drive</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is not particularly accurate, and as such always </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">needs</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to be </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">integrated</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> with other available data in order to evaluate the appropriateness of respiratory muscle workload (</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory rate, tidal volume, dyspnea, use of accessory muscles, shape of the inspiratory flow</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, ...).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">And to end, as always, a smile for all of </span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab’s </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">friends.</span></p><h3 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Note:</span></h3><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">* I think that it can be useful to state, for those who are less expert on the subjects, how to read P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. I have had this habit since the Nineties when, during an important congress, the moderator of a session on mechanical ventilation presented a speech on P</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">0.1</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> by reading it as P-O (as the alphabet letter)-one, as if it were similar to PO</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">... <b>(TRANSLATOR'S NOTE: this is not so relevant in American English, where zero can be pronounced O, as the letter of the alphabet)</b></span></p><h2 dir="ltr" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">References</span></h2><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">1) Jonkman AH, de Vries HJ, Heunks LMA: Physiology of the respiratory drive in ICU patients: implications for diagnosis and treatment. Crit Care 2020; 24:104</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2) Whitelaw WA, Derenne J-P, Milic-Emili J: Occlusion pressure as a measure of respiratory center output cm conscious man. Respir Physiol 1975; 23:181–199</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">3) Milic-Emili J: A Respiratory Physiologist by Hook or by Crook. Am J Respir Crit Care Med 2003; 167:1167–1168</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">4) Bertoni M, Telias I, Urner M, et al.: A novel non-invasive method to detect excessively high respiratory effort and dynamic transpulmonary driving pressure during mechanical ventilation. Crit Care 2019; 23:346</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">5) Sassoon CSH, Mahutte CK: Airway occlusion pressure and breathing pattern as predictors of weaning outcome. Am Rev Respir Dis 1993; 148:860–866</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">6) Fernandez R, Raurich JM, Mut T, et al.: Extubation failure: diagnostic value of occlusion pressure (P0.1) and P0.1-derived parameters. Intensive Care Med 2004; 30:234–240</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">7) Telias I, Junhasavasdikul D, Rittayamai N, et al.: Airway occlusion pressure as an estimate of respiratory drive and inspiratory effort during assisted ventilation. Am J Respir Crit Care Med 2020; 201:1086–1098</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">8) Alberti A, Gallo F, Fongaro A, et al.: P0.1 is a useful parameter in setting the level of pressure support ventilation. Intensive Care Med 1995; 21:547–553</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">9) Rittayamai N, Beloncle F, Goligher EC, et al.: Effect of inspiratory synchronization during pressure-controlled ventilation on lung distension and inspiratory effort. Ann Intensive Care 2017; 7:100</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">10) Perrigault P-FO, Pouzeratte YH, Jaber S, et al.: Changes in occlusion pressure (P0.1) and breathing pattern during pressure support ventilation. Thorax 1999; 54:119–123</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">11) Mancebo J, Albaladejo P, Touchard D, et al.: Airway occlusion pressure to titrate Positive End-expiratory Pressure in patients with dynamic hyperinflation. Anesthesiology 2000; 93:81–90</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 12pt; margin-top: 12pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">12) Beloncle F, Piquilloud L, Olivier P-Y, et al.: Accuracy of P0.1 measurements performed by ICU ventilators: a bench study. Ann Intensive Care 2019; 9:104</span></p><p dir="ltr" style="background-color: #fcfcfc; line-height: 1.92; margin-bottom: 0pt; margin-left: -1pt; margin-right: -1pt; margin-top: 0pt; margin: 0pt -1pt; padding: 20pt 0pt 0pt;"> </p><br /><br /><br /></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-56169254744346098422021-03-31T14:37:00.000+02:002022-01-27T09:14:58.285+01:00Dead space, Corrected Minute Ventilation and Ventilatory Ratio<p> <span face="Roboto, sans-serif" style="font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><a href="http://www.ventilab.it/2021/03/spazio-morto-ventilazione-minuto.html" target="_blank">Original post </a>written on 31</span><span face="Roboto, sans-serif" style="font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">st</span></span><span face="Roboto, sans-serif" style="font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> March 2021 by Giuseppe Natalini</span></p><span id="docs-internal-guid-3b3018b8-7fff-4d7c-54bb-bd86527da7ab"><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: -5pt 0pt 12pt 0pt;"><span face="Roboto, sans-serif" style="background-color: transparent; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 355px; overflow: hidden; width: 474px;"><img alt="Zorro: the serie" height="328" src="https://lh4.googleusercontent.com/SBPUAARE7BLV9PzXydKgS2fXv3abb_pp_13CrxIAl0-m-qjuFZbLTd9zQ-ORTpt5bFUArADNnblpOBYvp0a8aUgF6vuURMIraXKskSlwkLQgbcz6DZgR7bEnoNtHt6Jfm0XWOF21=w438-h328" style="margin-left: 0px; margin-top: 0px;" width="438" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">An</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> increase </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> dead space reduces alveolar ventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in absence of an adequate increase in minute ventilation. When this happens, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2 </span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> increases. </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Nonetheless, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is not only caused by an increase in dead space, but it can </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">also</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> be secondary to a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduction</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> minute ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (see </span><a href="http://www.ventilab.it/2018/02/ipercapnia-e-ards-cambia-qualcosa-parte.html" style="text-decoration-line: none;"><span style="background-color: transparent; color: blue; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">17/02/2018</span></a><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Today’s post focuses on this complex</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> relationship between dead space, hypoventilation and hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and offers two simple dead space surrogates (</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">corrected minute ventilation and Ventilatory Ratio).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Minute ventilation, alveolar ventilation, dead space and PaCO</span><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We are used to measuring a patient’s ventilation as </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">minute ventilation (VE),</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> that is to say the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">product of</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tidal volume (VT)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory rate (RR)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which quantifies how many liters of air come in and out of the airways in 1 minute. A healthy subject, as it is taught by physiology, inhales 0.5 L of VT, about 12 times per minute. This means that his\her VE is 6 L/min.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">depends</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> on the quote of VE that we call </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">alveolar ventilation (VA)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> ventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">(VD)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the difference between VE and VA, that is to say the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">quote of VE that does not take part in gas exchange</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In physiology, dead space is identified only by the volume of air that stays in the airways (anatomic dead space), which is about 150 mL.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 351px; overflow: hidden; width: 624px;"><img height="351" src="https://lh6.googleusercontent.com/3-Y11BUmOiwoJOYYbSoSJ8YLvui9LhMhsaVcmD356eP3zRER11FtLvru6BPQZ_kt-hH5KHcdYmWilYdTn3gsttXxvshGAy915QR5ypqZicrsc_iKD8r0CiOCpbwHn9sd27eRfGRN" style="margin-left: 0px; margin-top: 0px;" width="624" /></span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">VA is therefore calculated as:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">VA = (VT - VD) ∙ RR</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In a healthy male subject, which we are going to call -in an original way- Mario Rossi, we can calculate the VA using the above mentioned data:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">VA = (0.5 L - 0.15 L) ∙ 12/min = 4,2 L/min.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inversely proportional to VA</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> ~ 1/VA</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and Mario Rossi has a normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of 40 mmHg with a VA of 4,2 L/min, which corresponds to a VE of 6 L/min.</span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Hypoventilation.</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The previous formulas tell us that, if Mario Rossi’s respiratory frequency is halved (from 12 to 6 breaths/min), </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">VA</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> becomes </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">half of the previous one</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and therefore </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">doubles</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to 80 mmHg.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It’s an easily handled situation: to go back to a PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of 40 mmHg, it is enough to start mechanical ventilation, setting a respiratory rate of 12 breaths/min and a tidal volume of 500 mL, which is what all anesthesiologists do when they induce general anesthesia. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Hypoventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">is the least important problem</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> for those who know how to handle mechanical ventilation, unless intubation fails or unless airway obstruction is present...</span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Dead space</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s say that Mario Rossi is affected by </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ARDS</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and that he is ventilated with a tidal volume of 430 ml and a respiratory rate of 28 breaths/min. With these settings, the VE is 12 L/min (two times the norm) and, if dead space had remained 150 ml, VA would be 7.8 L/min (almost two times the norm) and therefore PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> would be almost half the norm (a little over 20 mmHg).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">But we all know very well that reality is different from this: if Mario Rossi has </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ARDS</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, he can have </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">despite the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase in VA and VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In ARDS, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">alveolar dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (which is negligible in physiology) </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increases</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, representing the air volume that does not take part in gas exchange even if it is contained into the alveoli. Alveolar dead space is generated if there are </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">alveolar surfaces that do not receive pulmonary capillary perfusion </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">or if the lungs are characterized by an </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase and heterogeneity in ventilation/perfusion ratio.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In ARDS, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">physiologic dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">the sum of alveolar and anatomic dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, can reach 80% of tidal volume. With this dead space value, it is possible to calculate that Mario Rossi has a PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of 70 mmHg, despite hyperventilation.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Differently from the one caused by hypoventilation, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> due to an </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increase</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dead space </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is particularly difficult to fix, because a great increase in VE, obtained by increasing tidal volume and respiratory rate, would be required. These are choices that can assist in generating </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Ventilator-Induced Lung Injury</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: a solution much worse than the (presumed) problem we want to solve.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In this case it is better to accept </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which is more of a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">marker</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">severity than a problem</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and wait for it to resolve after the patient gets better.</span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Dead Space Surrogates</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the variable most associated with </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mortality</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ARDS</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> patients. Its knowledge can have a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">prognostic value</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, it can help correctly </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">understand hyperventilation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> hypercapnia, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and can be useful in the evaluation of the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> evolution of ARDS </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">when both VE and PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> vary. Dead space, in the evaluation of ARDS patients, should at least be placed side-by-side to the well known PaO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">/FIO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which as we know has many limitations (see </span><a href="https://www.ventilab.it/2017/01/rapporto-pao2fio2-mito-o-realta.html" style="text-decoration-line: none;"><span style="background-color: transparent; color: blue; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">29/01/2017</span></a><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post)</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">However, dead space calculation requires the measurement of mean CO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> partial pressure in expired gas, which is not often available since it requires appropriate instruments such as volumetric capnography or indirect calorimetry.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Nonetheless we have the possibility to use two </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">surrogates</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of measured </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">corrected</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">VE (VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Although both of these indexes have the limit of using VE as an indicator of VA (we have seen it is not the same thing), they have been found to be associated with prognosis in ARDS patients, similarly to dead space. They can therefore be useful surrogates of dead space in clinical practice.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Corrected minute ventilation (VE</span><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">)</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> shows how much VE should be in order to have normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It is easy to calculate:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = VE ∙ PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">/(physiological PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">),</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">where physiological PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is estimated as 40 mmHg.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If a subject has a normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, VE e VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> are the same.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now let’s calculate Mario Rossi’s VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> when he hypoventilates and when he has ARDS, as described in the two previous examples.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">When Mario Rossi hypoventilates:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = 3 L/min ∙ 80 mmHg/40 mmHg = 6 L/min</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In this example </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is the same as the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> "in </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">physiology</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> books”, and we can conclude that </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">absent</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Good news for the patient (a low dead space is associated with a lower probability of death) and an easily corrected condition.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In ARDS patients, VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is associated with an increased mortality when it is higher than 13 L/min. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s calculate VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in Mario Rossi with ARDS:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> = 12 L/min ∙ 70 mmHg/40 mmHg = 21 L/min</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This means that Mario Rossi should have a VE of 21 L/min in order to have a PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of 40 mmHg: a really high value, which indicates a severe increase in dead space. This is bad news for Mario Rossi and a condition that should induce us to tolerate hypercapnia as the lesser evil compared to an escalation in ventilation.</span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio indicates how many VE should be increased, compared to the ideal value, in order to reach normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">.</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> Differently from VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, Ventilatory Ratio is an </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> adimensional number</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which considers also the level of ideal VE, which in turn depends on the patient's height. Ideal VE is thought to be 0.1 L/min per kg of ideal body weight. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">A small person, with an ideal body weight of 48 Kg, has an ideal VE of 4.8 L/min, much different from the 8 L/min which represent the ideal VE ideale of a person 185 cm tall and with an ideal body weight of 80 kg.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio is calculated as:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio = VE/(ideal VE) ∙ PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">/(ideal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As we have said above, the ideal VEis calculated as 0.1 L/min per kg of ideal body weight, and ideal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is estimated as 37.5 mmHg.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In the case of Mario Rossi, who has an ideal body weight of 70 kg, Ventilatory Ratio when he hypoventilates is calculated as:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio = 3 L/min / 7 L/min ∙ 80 mmHg/ 37.5 mmHg = 0.9.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">That means that Mario Rossi needs a VE equal to 0.9 the ideal VE ideale to keep a PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of 37.5 mmHg. </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio values close to 1 indicate the absence or little relevance of dead space</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: “ideal” VE is enough to keep normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> values, as in physiology.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">When Mario has ARDS, Ventilatory ratio becomes:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio = 12 L/min / 7 L/min ∙ 70 mmHg/37.5 mmHg = 3.2.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In other words, in this condition Mario Rossi needs </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">more than three times the ideal VE to maintain a normal PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, a sign of a severe increase in dead space.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">A Ventilatory Ratio higher than 2 is associated with an increased risk of death in ARDS patients.</span></p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #351c75; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Conclusions</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 12pt; margin-top: 0pt; padding: 12pt 0pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Let’s summarize this post’s key point:</span></p><ul style="margin-bottom: 0px; margin-top: 0px; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 12pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Hypercapnia’s </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">clinical </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">meaning </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">different</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> whether it is secondary to </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">minute ventilation reduction</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or to </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">an increase in dead space</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If hypercapnia is secondary to minute volume reduction, it is easily fixed with mechanical ventilation;</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> fixing hypercapnia secondary to a dead space increase </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">might be </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dangerous</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> for the patient, because it can lead to </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">non-protective ventilation</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">; </span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">evaluation</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dead space</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">clinically and prognostically useful</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> for ARDS patients;</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: disc; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 15pt; margin-top: 0pt;"><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In clinical practice, </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">corrected minute ventilation</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Ventilatory Ratio </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">are appropriate </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dead space</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">surrogates,</span><span style="font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> which can be obtained in any ICU.</span></p></li></ul><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> As always, a smile for all of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab’s </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">friends.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><h2 dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">References:</span></h2><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><u>Dead space physiology</u></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Robertson HT. Dead space: the physiology of wasted ventilation. Eur Respir J 2015;45:1704–1716.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Association between dead space and mortality in ARDS</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Nuckton TJ, Pittet J-F, Kallet R, Daniel BM, Pittet J-F, Eisner M, Matthay MA. Pulmonary Dead-Space Fraction as a Risk Factor for Death in the Acute Respiratory Distress Syndrome. N Engl J Med 2002;346:1281–1286.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Cepkova M, Kapur V, Ren X, Quinn T, Zhuo H, Foster E, Liu KD, Matthay MA. Pulmonary Dead Space Fraction and Pulmonary Artery Systolic Pressure as Early Predictors of Clinical Outcome in Acute Lung Injury. Chest 2007;132:836–842.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Kallet RH, Zhuo H, Liu KD, Calfee CS, Matthay MA, on behalf of the National Heart Lung and Blood Institute ARDS Network Investigators. The Association Between Physiologic Dead-Space Fraction and Mortality in Subjects With ARDS Enrolled in a Prospective Multi-Center Clinical Trial. Respiratory Care 2014;59:1611–1618.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"> <u><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Association between VE</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">corr</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">/Ventilatory ratio and mortality in ARDS</span></u></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Sinha P, Singh S, Hardman JG, Bersten AD, Soni N. Evaluation of the physiological properties of ventilatory ratio in a computational cardiopulmonary model and its clinical application in an acute respiratory distress syndrome population. Br J Anaesth 2014;112:96–101.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Sinha P, Calfee CS, Beitler JR, Soni N, Ho K, Matthay MA, Kallet RH. Physiologic Analysis and Clinical Performance of the Ventilatory Ratio in Acute Respiratory Distress Syndrome. Am J Respir Crit Care Med 2019;199:333–341.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Fusina F, Albani F, Bertelli M, Cavallo E, Crisci S, Caserta R, Nguyen M, Grazioli M, Schivalocchi V, Rosano A, Natalini G. Corrected Minute Ventilation Is Associated With Mortality in ARDS Caused by COVID-19. Respir Care 2021;66:619–625.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"> <u style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-weight: 700; white-space: pre-wrap;">Dead space in COVID-19 ARDS and ARDS due to other diseases</u></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">-</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Bertelli M, Fusina F, Prezioso C, Cavallo E, Nencini N, Crisci S, Tansini F, Mazzuca Mari L, Hoxha L, Lombardi F, Natalini G. COVID-19 ARDS is characterized by increased dead space ventilation compared with ARDS from other diseases. A cohort study.</span><span face=""system-ui", -apple-system, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif" style="color: #212121; font-size: 16px;"> Respir Care. 2021 Sep;66(9):1406-1415. doi: 10.4187/respcare.08786.</span><span face=""system-ui", -apple-system, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, "Fira Sans", "Droid Sans", "Helvetica Neue", sans-serif" style="color: #212121; font-size: 16px;"> </span></p><br /><br /></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-76876076648092658772020-07-27T15:02:00.000+02:002022-01-27T09:15:48.860+01:00Corticosteroids: a cure for COVID-19 or a cure for ARDS?<p><a href="https://www.ventilab.it/2020/07/cortisone-cura-per-la-covid-19-o-per.html" target="_blank">Original post </a>written on <span style="font-family: Arial; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">27</span><span style="font-family: Arial; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="vertical-align: super;">th</span></span> July 2020 by Giuseppe Natalini</p><p><br /><span id="docs-internal-guid-45bab95b-7fff-63d3-5975-9daec30a567e"></span></p><p><img height="288" src="https://lh3.googleusercontent.com/maXWxJzOwr1tyfniz3e2S8JmxIhdOmfBR5kcEFxJkZfXNgPQ7GkGlvA6Phv4wlkUAgvTWx-aUzLwM8jLR1RZWk09QGxCH7eVyg5jo6bb1DgSEuPBlijhy3i-88GYwGcVqkPuqBI" style="font-family: Arial; font-size: 9pt; margin-left: 0px; margin-top: 0px; white-space: pre-wrap;" width="391" /></p><span id="docs-internal-guid-e90c4ce0-7fff-bd7e-c13b-77665fa046f2"><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Recently, a randomized clinical trial (RCT) known as RECOVERY, on the use of corticosteroid therapy in SARS-CoV-2 disease (COVID-19), was published. The abstract’s conclusions affirm that dexamethasone therapy reduces 28 day mortality in patients </span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">“receiving either invasive mechanical ventilation or oxygen alone at randomization but not among those receiving no respiratory support.” </span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(1)</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It’s important to maintain the critical approach typical of a scientific attitude even when facing an important RCT like this one, and to integrate the RCT’s results with the knowledge already available to us.</span></p><br /><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="color: navy; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">RCT limitations</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There is no demonstration that a positive RCT result can give a definite proof of the efficacy of a certain therapy in a specific disease, in spite of the fideistic faith that evidence based medicine has in RCTs.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Recent history teaches us that the results of numerous RCTS on the care of critically ill patients (even those published on the most prestigious medical journals) can be denied after a few years. This has happened, for example, for glycemic control in ICU (2), early-goal directed therapy in septic shock to maintain an ScVO2 >70% (3), human activated C reactive protein in septic shock (4) which was later withdrawn from the market, cisatracurium infusion in initial phases of ARDS (5). Maybe some other examples will cross your mind, too.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">There is nothing strange in an RCT being denied. First of all, the so-called evidence based medicine is, in truth, a probability based medicine. This means, to simplify, that every RCT has 1 probability every 20 to show as effective a therapy that, in truth, is not effective. There is an even higher probability that a negative RCT will show as ineffective a treatment that is effective: this happens 1 every 5 times. These errors, inherent to statistical methods, are called “type I error” (alpha errors) and “type II errors” (beta errors).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Moreover, RCTs results are typically characterized by little external validity, meaning that they may not be applied to real life situations, and cannot be considered as necessarily valid for patients with different characteristics, treated in different contexts and in different times than the ones in which the RCT was developed. (6) </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This doesn’t mean that RCTs are worthless studies. We have to remember that RCT results are important, but cannot be accepted, with an act of faith, as definitive answers on a clinical query. They must be integrated with knowledge we gain from other types of studies. No perfect studies exist, and RCTs make no exception.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: navy; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Corticosteroid therapy in COVID-19: data from RCTs</span></p><h6 dir="ltr" style="line-height: 1.38; margin-bottom: 3pt; margin-top: 4pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">Let's go back to the results from the RECOVERY RCT, which was conducted in 176 hospitals in Great Britain. The study included patients with suspected or confirmed SARS-CoV-2 infection. In the end, 15% of the randomized patients did not have a confirmed diagnosis of SARS-CoV-2 infection, which, in presence of non cardiogenic respiratory failure with pulmonary infiltrates or ground glass appearance on chest X-ray (compatible with any type of pneumonia), was only suspected. In these cases, the diagnosis remained “</span><span style="font-family: Arial; font-size: 12pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">a clinical one based on the opinion of the managing doctor</span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">”.</span></h6><h6 dir="ltr" style="line-height: 1.38; margin-bottom: 3pt; margin-top: 4pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 400; vertical-align: baseline; white-space: pre-wrap;">After the exclusion of 2000 patients (the majority of them because they were “not considered suitable for randomization to dexamethasone”), almost 6500 patients were randomized to receive either 6 mg of dexamethasone (oral or intravenous) for up to 10 days or “usual care”, which means they received the treatment normally used in those 176 United Kingdom hospitals.</span></h6><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The study was NOT blinded, so the treating physicians knew who was receiving dexamethasone and who was not: this is an important limitation for any RCT.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Dexamethasone therapy could be started at any time during hospital admission, and in any clinical condition: at randomization, 16% of patients were intubated, 60% were receiving oxygen therapy or non invasive ventilation (these two possibilities were considered as the same thing), and 24% were receiving no respiratory support (not even oxygen).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The global result was a 2,8% reduction in 28 day mortality in patients receiving dexamethasone (22,9% in those receiving dexamethasone versus 25,7% in those not receiving it, Figure 1, red square).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The main reduction in mortality was observed in patients who were receiving invasive mechanical ventilation: in this group, mortality for patients receiving dexamethasone was 29% versus 41% in the “usual care” group.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The efficacy of dexamethasone was a lot less (or absent) in patients with oxygen therapy/non invasive ventilation and in those with no respiratory support: there was no significative difference in mortality when they were taken together (21.7% with dexamethasone versus 22.7% with “usual care”, Figure 1, blue square) .</span></p><p dir="ltr" style="line-height: 1.38; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 320px; overflow: hidden; width: 602px;"><img height="320" src="https://lh6.googleusercontent.com/IYDVaS2SLb9stEx1Xs4QYXwkfsRVpLuS84oiiyrkulprzvdJtmVhLhtCSc0MxT25wvuZHUrhPHRVa37w5mCLS4MqyLTzxo_jPNZn354LamrOHPKtdvP_zmEbyNxvck8KulAojvY" style="margin-left: 0px; margin-top: 0px;" width="602" /></span></span><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: navy; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Control group: “usual care”</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">A question arises after reading this RCT: dexamethasone was more effective than what other treatment, exactly, in patients receiving invasive mechanical ventilation? The answer is that dexamethasone was more effective than “usual care”. Still, we have to ask: what was considered as “usual care” for the 1007 invasively mechanically ventilated patients in the 176 U.K. hospitals that participated in the RECOVERY trail (5-6 patients per hospital)? What were the criteria for intubation? Which ventilatory settings (tidal volume, driving pressure, PEEP, Plateau pressure) were applied? How often was prone positioning used? Did patients receive muscle relaxants? And so on.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It is well known that, even in the era of protective ventilation, 35% of ARDS patients receive an excessive tidal volume (> 8 m/kg ideal body weight) and 80% receive a tidal volume greater than 6 ml/kg ideal body weight (7). We also know that a high tidal volume, inappropriate PEEP levels or a stress index >1 cause an increase in inflammatory cytokines. (8,9) Could corticosteroid therapy be effective on this possible source of inflammation?</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We know that prone positioning, which is protective for pulmonary stress (10–12), is often not used in patients with severe ARDS (13). How often was it used in RECOVERY patients?</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As we saw at the beginning of our post, RCTs results are highly dependent on “usual care”. This means that they depend on the clinical context in which the results were obtained, and by the combination with other treatments. The possibility to generalize any RCT findings to our clinical practice depends on these elements . If we do not know how RECOVERY patients were ventilated, we cannot know how much the results can be valid for us.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: navy; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Are corticosteroids effective in COVID-19 or in ARDS? </span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">If corticosteroid therapy had really been effective in COVID-19, it should have reduced mortality in all patients groups,</span><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and not only in invasively mechanically ventilated patients. Why did it work well only in intubated patients and not so well in the others?</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Those of us who have seen COVID-19 patients who need invasive mechanical ventilation know well that, at this stage, these patients have a bilateral pneumonia. That is to say, they have an ARDS (see </span><a href="http://www.ventilab.org/2012/06/24/definizione-e-diagnosi-di-ards-acute-respiratory-distress-syndrome-scopri-le-novita/" style="text-decoration-line: none;"><span style="color: #2585b2; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">24/06/2012</span></a><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> post for ARDS diagnosis).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It seems logic to infer that RECOVERY results support the efficacy of corticosteroid therapy in ARDS. The result is not groundbreaking, since corticosteroid therapy was already recommended by the European Society of Intensive Care Medicine and the Society of Critical Care Medicine 2017 joint guidelines (14) and confirmed by a recent RCT in ARDS patients (15)</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The value of RECOVERY is to dissolve any uncertainty of the use of steroids in COVID-19 patients when they develop ARDS. Corticosteroid therapy was initially discouraged in COVID-19 for fear of a reduced viral clearance (16). RECOVERY results confirm this fear in patients without a severe respiratory failure (15-20% mortality), but show that, when ARDS develops, benefits outweigh risks. Steroid use is therefore justified in ARDS secondary to COVID-19.</span></p><h6 dir="ltr" style="line-height: 1.38; margin-bottom: 3pt; margin-top: 4pt;"><span style="color: navy; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Conclusions</span></h6><br /><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The results of the RECOVERY RCT show that steroid therapy is not effective in COVID-19 (if it was, it would have reduced mortality for every disease severity).</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">This study confirms that corticosteroid therapy is effective in ARDS, even when due to COVID-19.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The efficacy of dexamethasone is COVID-19 ARDS is valid when patients are treated according to RECOVERY’S “usual care”(intubation indications, ventilatory volumes and pressures, associated drugs…), which are not available to us (at least for now). These results might not be reproduced in hospitals with a “usual Care” from the participating UK hospitals.</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As usual, a smile for all ventilab friends, and happy holidays! This year, we really deserve them</span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: none; display: inline-block; height: 72px; overflow: hidden; width: 72px;"><img alt="🙂" height="72" src="https://lh5.googleusercontent.com/1TAe8HQWmPFl3k7rahGCQjpMMcXRSSuQ9mNmdNHZBRXvD9ZrjZLxz4yFOAKXwewTjXmQbL1qs8YGpiyCEOUeGKpFTRi5BuGjXBTj1he6DnjIRAEsvP20-KBeVDhd6hU7TEUZfEk" style="margin-left: 0px; margin-top: 0px;" width="72" /></span></span></p><p dir="ltr" style="line-height: 1.68; margin-bottom: 11pt; margin-top: 0pt;"><span style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">References</span></p><ol style="margin-bottom: 0px; margin-top: 0px; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">The RECOVERY Collaborative Group. Dexamethasone in Hospitalized Patients with Covid-19 — Preliminary Report. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">N Engl J Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2020;NEJMoa2021436.doi:10.1056/NEJMoa2021436.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">van den Berghe, G, Wouters P, Weekers F, Verwaest C, Bruyninckx F, Schetz M, Vlasselaers D, Ferdinande P, Lauwers P, Bouillon R. 110801 Intensive Insulin Therapy in Critically Ill Patients. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">N Engl J Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2001;345:1359–1367.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Rivers E, Nguyen B, Havstad S, Ressler J, Muzzin A, Knoblich B, Peterson E, Tomlanovich M. Early Goal-Directed Therapy in the Treatment of Severe Sepsis and Septic Shock. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">N Engl J Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2001;345:1368–1377.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Bernard GR, Dhainaut J-F, Helterbrand JD. Efficacy and Safety of Recombinant Human Activated Protein C for Severe Sepsis. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">N Engl J Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2001;344:699–709.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Papazian L, Forel J, Gacouin A, Penot-Ragon C, Gilles P, Loundou A, Jaber S, Arnal J, Perez D, Seghboyan J, Constantin J, Courant P, Lefrant J, Claude G, Prat G, Morange S, Roch A. 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Evidence for Health Decision Making — Beyond Randomized, Controlled Trials. In: Drazen JM, Harrington DP, McMurray JJV, Ware JH, Woodcock J, editors. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">N Engl J Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2017;377:465–475.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Bellani G, Laffey JG, Pham T, Fan E, Brochard L, Esteban A, Gattinoni L, van Haren F, Larsson A, McAuley DF, Ranieri M, Rubenfeld G, Thompson BT, Wrigge H, Slutsky AS, Pesenti A, for the LUNG SAFE Investigators and the ESICM Trials Group. 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Accuracy of Plateau Pressure and Stress Index to Identify Injurious Ventilation in Patients with Acute Respiratory Distress Syndrome: </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Anesthesiology</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2013;119:880–889.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Mentzelopoulos SD. Prone position reduces lung stress and strain in severe acute respiratory distress syndrome. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Eur Respir J</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2005;25:534–544.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Cornejo RA, Díaz JC, Tobar EA, Bruhn AR, Ramos CA, González RA, Repetto CA, Romero CM, Gálvez LR, Llanos O, Arellano DH, Neira WR, Díaz GA, Zamorano AJ, Pereira GL. Effects of Prone Positioning on Lung Protection in Patients with Acute Respiratory Distress Syndrome. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Am J Respir Crit Care Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2013;188:440–448.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Galiatsou E, Kostanti E, Svarna E, Kitsakos A, Koulouras V, Efremidis SC, Nakos G. Prone Position Augments Recruitment and Prevents Alveolar Overinflation in Acute Lung Injury. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Am J Respir Crit Care Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2006;174:187–197.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Guérin C, Gurjar M, Bellani G, Garcia-Olivares P, Roca O, Meertens JH, Maia PA, Becher T, Peterson J, Larsson A, Gurjar M, Hajjej Z, Kovari F, Assiri AH, Mainas E, Hasan MS, Morocho-Tutillo DR, Baboi L, Chrétien JM, François G, Ayzac L, Chen L, Brochard L, Mercat A, for the investigators of the APRONET Study Group, the REVA Network, the Réseau recherche de la Société Française d’Anesthésie-Réanimation (SFAR-recherche) and the ESICM Trials Group. A prospective international observational prevalence study on prone positioning of ARDS patients: the APRONET (ARDS Prone Position Network) study. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Intensive Care Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2018;44:22–37.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Annane D, Pastores SM, Rochwerg B, Arlt W, Balk RA, Beishuizen A, Briegel J, Carcillo J, Christ-Crain M, Cooper MS, Marik PE, Meduri GU, Olsen KM, Rodgers SC, Russell JA. Guidelines for the Diagnosis and Management of Critical Illness-Related Corticosteroid Insufficiency (CIRCI) in Critically Ill Patients (Part I): Society of Critical Care Medicine (SCCM) and European Society of Intensive Care Medicine (ESICM) 2017. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Crit Care Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 2017;45:11.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Villar J, Ferrando C, Martínez D, Ambrós A, Muñoz T, Soler JA, Aguilar G, Alba F, González-Higueras E, Conesa LA, Martín-Rodríguez C, Díaz-Domínguez FJ, Serna-Grande P, Rivas R, Ferreres J, Belda J, Capilla L, Tallet A, Añón JM, Fernández RL, González-Martín JM, Aguilar G, Alba F, Álvarez J, Ambrós A, Añón JM, Asensio MJ, Belda J, Blanco J, </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">et al.</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> Dexamethasone treatment for the acute respiratory distress syndrome: a multicentre, randomised controlled trial. </span><span style="font-size: 10.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Lancet Respir Med</span><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2020;S2213260019304175.doi:10.1016/S2213-2600(19)30417-5.</span></p></li><li aria-level="1" dir="ltr" style="color: #444444; font-family: Arial; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; margin-left: 18pt; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="line-height: 1.68; margin-bottom: 18pt; margin-top: 0pt;"><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">World Health Organization. Clinical management of severe acute respiratory infection (SARI) when COVID-19 disease is suspected. Interim guidance 13 March 2020. 2020;at <</span><a href="https://www.who.int/docs/default-source/coronaviruse/clinical-management-of-novel-cov.pd&gt" style="text-decoration-line: none;"><span style="color: #2585b2; font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">https://www.who.int/docs/default-source/coronaviruse/clinical-management-of-novel-cov.pd&gt</span></a><span style="font-size: 10.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;.</span></p></li></ol></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-47367721053174412872013-06-28T17:31:00.001+02:002022-03-08T17:34:09.265+01:00MIP/NIF in weaning from mechanical ventilation: strength and load<p><a href="http://www.ventilab.it/2013/06/mipnif-nello-svezzamento-weaning-dalla.html" style="text-decoration-line: none;"><span style="color: #1155cc; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;">Original post</span></a><span style="color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> written by Giuseppe Natalini on 28</span><span style="color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">th</span></span><span style="color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> June 2013</span></p><span id="docs-internal-guid-7e405184-7fff-466d-dc25-988b008141f2"><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid #f2f2f2; display: inline-block; height: 295px; overflow: hidden; width: 419px;"><img height="295" src="https://lh3.googleusercontent.com/Jfq_DUPn2ANDSm8jYALhBJZUjJrbO0mjfgxLficKGUKdeSgKL9I1epUpr4-m1Gog-yOISGDdUPfZdGmlGb1PdUZsWHD2wkJpejcu_w47BINWfWjwUOGCCYr7IyXzYFrSJJTlOgSx" style="margin-left: 0px; margin-top: 0px;" title="Amor" width="419" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">As promised to some of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">’s friends, here is the post on </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Maximum Inspiratory Pressure (MIP)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (also called </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Negative Inspiratory Force, NIF</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). What is it? What's its usefulness? </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 10pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In order to answer these questions, let’s analyze Piero's case together.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Piero is a 78 year old man who has been admitted to the ICU for a postoperative COPD exacerbation. He has a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tracheostomy, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">weaning from mechanical ventilation has been difficult </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">for him. Just a few hours after we disconnect him from the mechanical ventilator, he becomes</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> dyspneic</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and his </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">breathing becomes rapid and shallow</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. This is something that happens relatively often in our patients. Why can’t Piero be weaned from mechanical ventilation?</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We know that </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">dependency from mechanical ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> can be due, mainly, to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">two reasons</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: a high load or a reduction in the strength of the respiratory muscles.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid #f2f2f2; display: inline-block; height: 408px; overflow: hidden; width: 451px;"><img height="408" src="https://lh6.googleusercontent.com/sULfFLpQyHzTjoPUBZ1DxXdDsEJirw-pODcj2TRLY36tMYQ7RG3dEqx9-wdrHjwvza-6-BVr6zvOE0pBhY7bjByt0hDTc7DzoVXIFiaxKBHeT0Mmf7eB_0dqGwolfGUe4x42rVc8" style="margin-left: 0px; margin-top: 0px;" title="balance_load_neuromuscular_competence" width="451" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If we can understand which one of these is Piero’s main problem, we can direct our efforts towards its real solution. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In order to examine the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">strength of the respiratory muscles</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we can measure </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">MIP</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">MIP </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is the measurement of the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> variation in pressure generated by the respiratory muscles during a maximal inspiration against a closed airway</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In intubated or tracheostomized patients (like Piero), we must occlude the airway at the end of expiration and ask the patient to inhale as deeply as possible. The </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">variation in airway pressure</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is our </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">MIP</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Some mechanical ventilators have the option to measure it automatically, otherwise it is possible to occlude the airways an instant before the start of maximum inspiration, freeze the airway pressure trace during the maneuver and analyze it. We must</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> explain to the patient what he has to do</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and while he performs the maneuver he must be guided and encouraged to do it well. Repeating the maneuver 3-5 times and using the greatest variation in pressure as the MIP value is recommended. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patients who are not compliant, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">it has been suggested to</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> occlude the airways</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (with a unidirectional valve) </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">for 20-25 consecutive seconds</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and to detect the maximum airway pressure variation.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><br /></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We measured Piero’s MIP, as we often do in patients for whom weaning from mechanical ventilation is especially challenging. We explained the maneuver to him and we asked him to repeat it 3 times. We put Piero in CPAP with 0 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (i.e. we left him connected to the ventilator without any applied positive pressure) and we occluded the airways at the end of expiration. At the same time, we recorded airway pressure. Here is the result: </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid #f2f2f2; display: inline-block; height: 88px; overflow: hidden; width: 576px;"><img height="88" src="https://lh4.googleusercontent.com/vWB3idGD_gKJq6bVpgrhCVM-eBb__50HwH6zBjGlx0kI7tDTadwN1YaCIdqIeuIGz_8IMVNt5V0Okfo_pEM4-NtQS1G1E6wKs-36hSOI-9onUNCyyb_jTKHyw-lK1RRW4BVbIy_I" style="margin-left: 0px; margin-top: 0px;" title="piero_mip_paw" width="576" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Piero was able to reduce his airway pressure to a maximum of 30 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O during airway occlusion. What does a MIP of 30 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O mean? Piero seems to be a relatively weak patient, but this does not appear to be the only cause of his unsuccessful weaning. Indeed, Piero’s “normal” MIP should be much greater (between 50 and 95 cmH2O, see note at the end of the post), but usually </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">muscle weakness </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">in itself</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">becomes the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> cause of weaning failure </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">when </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">MIP</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is below </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">20 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Therefore, MIP gave us some useful information which is nonetheless not enough to fully understand the problem. Now we must understand how much is the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> load for his respiratory muscles</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, in other words how much it “costs” him to take a breath. Hence we have measured </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">esophageal pressure</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and you can see the answer below:</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid #f2f2f2; display: inline-block; height: 87px; overflow: hidden; width: 593px;"><img height="87" src="https://lh4.googleusercontent.com/9myQ2NYpHBVzF2RMiR9W41VH8lYoCny-YVw7iYQAnDLBQHJgJGrMPmXxwir-J4at1bNGphX8HIlmQkHhdMX4wx1UYLkaTMzwSULxoWDT9wXYo2QWoYw8gJUjUaKxNUhQ_4Rp2nkP" style="margin-left: 0px; margin-top: 0px;" title="piero_dpes" width="593" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">During a normal respiratory cycle esophageal pressure decreases, on average, 16 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> for each </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">inspiration</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. In the image above we can see the esophageal pressure trace for three consecutive inspirations: each reduction in pressure corresponds to the pressure generated by the respiratory muscles during normal respiratory activity. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Now we know both of the factors at play</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: Piero’s </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">respiratory muscles’ load</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">strength</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">load</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is around </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">16 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">strength </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is around </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">30 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> During each inspiration</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, Piero must use </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">more than half of the maximum force </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">he can develop: </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">an unsustainable effort</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. Indeed it is believed that </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous breathing cannot be maintained for long</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> when the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> ratio between load </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(=esophageal pressure variation during normal respiration) </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">and strength</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (=MIP) is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">greater than 0.2</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e. when more than 20% of the maximum force is used for each breath. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We can therefore say that Piero, even if he is not extremely weak (MIP>20 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O), must sustain a work which is too much for his own strength. We measured Piero’s </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">intrinsic PEEP</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and found it is </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">8 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: for each breath, half of his effort is used to overcome intrinsic PEEP.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Now we have all the elements we need to consciously guide our efforts in order to wean Piero from mechanical ventilation. First, we must try to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduce the intrinsic PEEP </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">that is generated during </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">spontaneous respiration </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(in this case we are not interested in fighting PEEPi during mechanical ventilation): </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">1) we must maximize </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">bronchodilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2) we must reduce spontaneous respiratory rate and minute ventilation: in order to do so we must </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduce CO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> production</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (with a</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> correct nutritional intake</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">control of hyperthermia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">), eventually occasionally using opioids during phases of tachypnea which do not resolve rapidly</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 3) </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduce flow limitation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">by keeping the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">patient sitting up</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">It is also important to</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> increase the strength </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">of Piero’s</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> respiratory muscles</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The most important factor in doing so is, in my opinion, the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">correct modulation of ventilatory assistance</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, with the objective of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">avoiding</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> both </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">constant fatigue </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">and the </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">reduced use of respiratory muscles</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (excessive assistance and, worse, autocycling). Other factors are a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">correct nutritional intake</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">calories, proteins, calcium, phosphate</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">), and probability</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> daily breathing exercises</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> against a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">threshold load.</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> Additionally, the maintenance of a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">sitting position</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: the diaphragm needs footholds, too.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We certainly haven’t resolved Piero’s problems yet, but surely we know so much more than the simple observation of his failed weaning, and we have created a personalized treatment plan.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 12pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In conclusion:</span></p><ol style="margin-bottom: 0; margin-top: 0; padding-inline-start: 48px;"><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 12pt;"><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">MIP/NIF </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">can be useful in clinical practice in case of </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">difficult weaning</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">;</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If we find a</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> MIP<20 cmH</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O, the main problem is respiratory muscles weakness: </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">we must act mainly to solve this problem (as much as possible);</span></p></li><li aria-level="1" dir="ltr" style="color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; list-style-type: decimal; vertical-align: baseline; white-space: pre;"><p dir="ltr" role="presentation" style="background-color: white; line-height: 1.68; margin-bottom: 12pt; margin-top: 0pt;"><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">If </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">MIP</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is, as often happens, between</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 20 and 50 cmH</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, it is useful to </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">evaluate the load</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e. the </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">variation of esophageal pressure during normal ventilation</span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. A </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ratio between normal esophageal pressure variation) and MIP >0.2 </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">means that the </span><span style="background-color: transparent; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">load is too high for the patient’s abilities.</span></p></li></ol><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">A smile for all of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ventilab</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">’s friends (hoping good weather returns…)</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Note</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-style: italic; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The normal range for MIP can be calculated as follows: for males 126 - 1.028*age + 0.343*body weight in kg+ 22.4; in females 171 - 0.694*age+ 0.861*body weight in kg- 0.743*height in cm + 18.5</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; padding: 12pt 0pt 12pt 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">References</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- ATS/ERS Statement on Respiratory Muscle Testing. Am J Respir Crit Care Med 2002; 166: 518-624</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Cader SA et al. Inspiratory muscle training improves maximal inspiratory pressure and may assist weaning in older intubated patients: a randomised trial. J Physiother 2010; 56:171-7</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Harik-Khan RI et al. Determinants of maximal inspiratory pressure: the Baltimore Longitudinal Study of Aging. Am J Respir Crit Care Med 1998; 158:1459-64</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Martin AD et al. Inspiratory muscle strength training improves weaning outcome in failure to wean patients: a randomized trial. Crit Care 2011; 15:R84</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Moxham J et al. Assessment of respiratory muscle strength in the Intensive Care Unit. Eur Respir J 1994; 7: 2057-61</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- Truwit JD at al. Validation of a technique to assess maximal inspiratory pressure in poorly cooperative patients. Chest 1992; 102;1216-9</span></p><div><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 11.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></div></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0tag:blogger.com,1999:blog-8476348176871983433.post-8603262297196152422011-09-24T11:13:00.052+02:002022-02-24T11:27:00.527+01:00ARDS, permissive hypercapnia and respiratory acidosis<p><br /></p><span id="docs-internal-guid-b4b18cd5-7fff-9de8-0cec-ba82a816b0bb"><p dir="ltr" style="background-color: white; line-height: 1.92; margin-bottom: 0pt; margin-top: 0pt; padding: 0pt 0pt 17pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><a href="http://www.ventilab.it/2011/09/ards-ipercapnia-permissiva-e-acidosi.html" target="_blank">Original post</a> written by Giuseppe Natalini on 24</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: super;">th</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> September 2011</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 485px; overflow: hidden; width: 259px;"><img height="485" src="https://lh5.googleusercontent.com/ekk_zsLSaL3bZt_Dq8Ccg2mLyCJEfDKSVaR92lnuAhdDcuuptfaqlfgTcMQKeFeFEw59V7uZAtQXEsteGboNwHZcPsCNvKjAquiiGqk1jSPVg6L8XCtlhd8B04em9blCUVRLvYRq" style="margin-left: 0px; margin-top: 0px;" title="sarah_tc" width="259" /></span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">About ten days ago we admitted Sarah, a 45 year old woman, to ICU with </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ARDS</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> secondary to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Legionnaires' disease</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 13.5pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (you can see the CT scan images above)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We decided to use </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">protective ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. The ventilator was set with a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">tidal volume</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">280 ml</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">breath rate</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">32 breaths/minute</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> and an external </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PEEP</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">16 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (which was the PEEP level associated with the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> smallest driving pressure</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, i.e. associated with the <b>l</b></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><b>o</b></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">west elastance</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">). FIO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> was modified in order to maintain SaO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> > 90%.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Sarah is 163 cm tall and weighs 60 kg. We have to remember that</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> tidal volume</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> relates to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ideal body weight*</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, which, in Sarah’s case, is 55 kg. We were therefore ventilating her with</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 5 ml/kg of tidal volume</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. With this ventilation, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">plateau pressure </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">wa</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">s about </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">30-31 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, with a</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> transpulmonary pressure</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">14-15 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. All this while using sedation, muscle paralysis and steroid therapy.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">And what about her </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">arterial blood gas results</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">? Here they are: </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pH 7.11, PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 82 mmHg</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">PaO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> 67</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mmHg</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> with FIO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> 0.9. We also tried nitric oxide, pronation and lateral position (damage to the right lung was prevalent), with no improvement on ABG values or respiratory mechanics. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">In summary</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">: Sarah was receiving </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">protective ventilation</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, and with these settings we had an </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">oxygenation </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">which was more than </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">sufficient</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. How to behave with the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> severe respiratory acidosis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">? Should we have accepted it or not?</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">When we want to </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">decrease PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">, we have to options: </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-indent: 36pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">increasing ventilation</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-indent: 36pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">- using </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ECMO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> or other</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> extracorporeal </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">CO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> removal </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">techniques </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-indent: 36pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Increasing ventilation, in this case, meant abandoning protective ventilation: we had already reached the upper limit with plateau pressure (for both airway and transpulmonary pressure). We have decided not to use this option. </span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">ECMO would, in this case, have been indicated only to treat the respiratory acidosis: PaO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> was, in fact, still sufficient.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">But is respiratory acidosis really an enemy </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">we have to fight at all costs?</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="border: 0pt solid rgb(242, 242, 242); display: inline-block; height: 416px; overflow: hidden; width: 169px;"><img height="416" src="https://lh3.googleusercontent.com/Ijh_Z9JrMmIhIBNn7cLUxGxmmYHmGXRzg98KXrF4XJfBkkr9VJvWst2_It5nTZ4xqtu7vPmxPMeQvRyp-nF3VhPSdgPqbuy7rXbLj5dzWPaWZOoRFqOIE_57DpSic-k4fB5iuQEU" style="margin-left: 0px; margin-top: 0px;" title="paco2_hickling" width="169" /></span></span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt; text-align: center;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Figure 1</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">When I started to treat my first ARDS patients, twenty years ago, we all believed the right thing to do was to strive to obtain a PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> of 40 mmHg and a pH of 7.40. With terrible results.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">In </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">1990,</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> a</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> revolutionary message</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> arrived from New Zealand (1). Dr. Keith Hickling said that, for a few years, he had been ventilating patients by reducing airway </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">pressure</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> below </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">30 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">O</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (!), accepting </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">low tidal volumes</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> down to 5 ml/kg (!!) and </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">not doing anything</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> to treat </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">moderate hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> up to 70 mmHg). For higher PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> values he raised peak pressure up to maximum 40 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O (something similar to our plateau pressure of 30 cmH</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">O). The result: his patients had a </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mortality of 16%</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (the mortality predicted with APACHE II score would have been 40%)!. And his patients had “insane” PaCO</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><span style="font-size: 0.6em; vertical-align: sub;">2</span></span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> values (up to 129 mmHg!) (see Figure 1). </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Permissive hypercapnia</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in ARDS was born.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">We all know how this story ended: this strange philosophy for mechanical ventilation (which cares about lungs and not about ABG) became the standard, with a less casual attitude today towards very low pH values.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">Respiratory acidosis </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">has physiological </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">positive and negative effects </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(2). In </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ARDS </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">patients, it seems to have </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">mainly a protective effect </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">(3)</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">,</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> as well as being </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">protective</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> in the</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;"> early phases of sepsis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> (4).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Sarah does not have ARDS anymore. We are not claiming victory yet because, even if she has greatly improved, she still hasn’t won her fight for survival. The </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">message</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is nonetheless clear: </span><span style="background-color: transparent; color: red; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">lung protection</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> is </span><span style="background-color: transparent; color: red; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">much more important </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">than </span><span style="background-color: transparent; color: red; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">arterial blood gas analysis</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">. And </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">hypercapnia </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">is not necessarily an enemy: in fact,</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; text-decoration-line: underline; text-decoration-skip-ink: none; vertical-align: baseline; white-space: pre-wrap;"> sometimes</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> it can become an </span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; font-weight: 700; vertical-align: baseline; white-space: pre-wrap;">ally</span><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"> on which to count on.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">Greetings to all.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">*Let’s remember that the ideal body weight for females is calculated as: 45.5+0.91(height in centimeters-152.4). For males the formula is the same, but we have to substitute 50 to 45.5 (5).</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">References.</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">1) Hickling KG et al. Low mortality associated with low volume pressure limited ventilation with permissive hypercapnia in severe adult respiratory distress syndrome. Intensive Care Med 1990; 16:372-7</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">2) Ijland MM et al. Hypercapnic acidosis in lung injury - from ‘permissive’ to ‘therapeutic’. Crit Care 2010; 14:237</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">3) Kregenow DA et al. Hypercapnic acidosis and mortality in acute lung injury. Crit Care Med 2006; 34:1-7</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">4) Curley G et al. Can ‘permissive’ hypercapnia modulate the severity of sepsis-induced ALI/ARDS? Crit Care 2011; 15:212</span></p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"> </p><p dir="ltr" style="background-color: white; line-height: 1.68; margin-bottom: 0pt; margin-top: 0pt;"><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;">5) ARDS Network. Ventilation with lower tidal volumes as compared with traditional for acute lung injury and the acute respiratory distress sindrome. N Engl J Med 2000, 342:1301-8</span></p><div><span style="background-color: transparent; color: #34495e; font-family: Arial; font-size: 12pt; font-variant-east-asian: normal; font-variant-numeric: normal; vertical-align: baseline; white-space: pre-wrap;"><br /></span></div></span>Federica Fusinahttp://www.blogger.com/profile/01655652031107954599noreply@blogger.com0