Assessment of Preload Responsiveness in ARDS Patients During Prone Position

Study Overview
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Brief Summary
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Evaluation of preload responsiveness in ARDS patients during prone position is difficult and only one study showed Trendelenburg manoeuvre can be used in this group of patients. This study aims to investigate whether end-expiratory occlusion test, tidal volume challenge (using the changes in PPV) can be used to evaluate preload responsiveness in patients with ARDS ventilated with a low tidal volume and who underwent a PP session.

Detailed Description
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Acute respiratory distress syndrome (ARDS) which is a major cause of morbidity and mortality in the intensive care unit, is characterized by decreased lung volume, decreased lung compliance, increased pulmonary vascular resistance and pulmonary hypertension, which ultimately lead to right ventricular dysfunction. Moreover, through biventricular interdependence and inter-ventricular septum shift, the left ventricular filling is limited, which eventually results in a decrease in stroke volume. Due to the high risk of ventilation-induced lung injury, protective lung ventilation is recommended, mainly through a reduction in tidal volume. However, due to the profound hypoxemia inherent to this mode of ventilation, lung recruitment strategies are recommended. When the application of a recruitive positive end-expiratory pressure fails to correct hypoxemia, prone positioning (PP) is recommended. A randomized controlled trial (PROSEVA) reported that early application of prolonged PP sessions in patients with severe ARDS significantly decreased 28- and 90-day mortality. In addition to its respiratory effects (improvement in arterial oxygenation and lung recruitment), PP exerts different cardiovascular effects. By increasing oxygenation and recruiting lung regions, PP can reduce the right ventricular afterload. By increasing the intraabdominal pressure (IAP), PP can increase the venous return and the cardiac preload. This effect might depend on the level of IAP, because a high IAP might collapse the inferior vena cava, especially in the case of hypovolemia. If cardiac preload increases, the resultant effect on cardiac output might depend on the degree of preload responsiveness. Finally, by increasing the IAP, PP can increase the left ventricular afterload. In a recent clinical study, our group showed that PP increases right and left ventricular preload and decreased right ventricular afterload. However, PP increased cardiac output only in patients with preload responsiveness. In this study preload responsiveness was detected by an increase in cardiac output > 10% during a passive leg raising (PLR) test. Since PP sessions are recommended to last between 16 to 18 hours per day and since patients with ARDS often have an associated sepsis, hemodynamically instability may occur during PP sessions. The therapeutic decision is very tricky since the administration of fluid (the main therapeutic option in case of hemodynamic instability) is risky due to alteration of lung capillary membrane permeability. Thus, it is important to predict the benefits of fluid administration by using indices of preload responsiveness. The recommended indices of preload responsiveness are pulse pressure variation (PPV), stroke volume variation (SVV) and PLR. However, PPV and SVV cannot be used reliably during low tidal volume ventilation. Moreover, conventional PLR cannot be performed during PP. It is thus important to develop other preload responsiveness tests doable during PP. Our group proposed to perform an end-expiratory occlusion (EEO) test to predict fluid responsiveness in the supine position and more recently to perform a tidal volume challenge (TVC) by transiently increasing tidal volume from 6 to 8 mL/kg and observing the changes in PPV.

Official Title
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Evaluation of Tidal Volume Challenge to Detect Preload-responsiveness in Patients With Acute Respiratory Distress Syndrome (ARDS) During Prone Position

Conditions
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Acute Respiratory Distress Syndrome, Septic Shock, Hemodynamic Instability

Intervention / Treatment
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* Other: Tidal volume challenge
* Other: End-expiratory occlusion test
* Other: Trendelenburg maneuver


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: ARDS patient Prone position Monitored by transpulmonary thermodilution and pulse contour analysis Exclusion Criteria: Age below 18 No social security Refuse to participate in the study

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Intervention/Treatment |
| --- |
|Other: Tidal volume challenge|Increasing tidal volume from 6 to 8 mL/kg during 1 min|
|Other: End-expiratory occlusion test|Interrupting the ventilator at end-expiration for 15-30 s and assessing the resulting changes in cardiac output|
|Other: Trendelenburg maneuver|Patients remained in prone position with a 13° upward bed angulation throughout the study and then be positioned in a declining position at -12 ° for 1 minute|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Area under ROC curve of the change in pulse pressure variation during tidal volume challenge to detect preload responsiveness |  | 1 minute after increasing tidal volume from 6 to 8mL/kg | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Area under ROC curve of the pulse pressure variation in tidal volume of 8ml/kg in continuous cardiac output during end-expiratory occlusion to detect preload dependence |  | 1 minute after tidal volume increase to 8 ml/kg | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Hemodynamic monitoring, preload responsiveness, ARDS, Fluid therapy