The objective of this study was to investigate the hemodynamic effects of two alveolar recruitment maneuver strategies in critical care patients with acute respiratory distress syndrome.

Critical care patients are at risk of significant variations in blood volume due to long intervention times, major bleeding or serious pathological conditions, requiring invasive hemodynamic monitoring in routine practice, in order to optimize blood volume and ensure adequate perfusion of the organs, throughout their care.

The installation of an arterial catheter allows continuous monitoring of blood pressure and the realization of blood tests if necessary.

The installation of a central venous line allows the administration of anesthetic drugs and vasopressors as well as an accurate hemodynamic evaluation by transpulmonary thermodilution, which is the most commonly used monitoring in these situations.

After hemodynamic optimization following the monitoring data, the patient will be randomized to one of the two Alveolar Recruitment Maneuver (ARM) order strategies. Mechanical ventilation will be standardized according to current international recommendations (tidal volume between 6 mL.kg-1 and 8 mL.kg-1 of theoretical ideal weight (TIP) for patients with Acute Respiratory Distress Syndrome (ARDS); PEEP equal to 6 cmH2O). Hemodynamic and ventilatory data will be collected (baseline).

The successive realization of the two ARM will then be carried out with collection of the hemodynamic and ventilatory data during the last 10 seconds of each ARM. Between each ARM, conventional ventilation will be resumed for 10 minutes in order to observe a wash-out period, and to allow a return to the baseline state. Data will also be collected as before.

After these measurements have been taken, all management will be left to the discretion of the practitioner caring for the patient.

Inclusion Criteria:

• Patient over 18 years old
• Patient under general anesthesia
• Intubated patient under controlled invasive mechanical ventilation
• Patient with invasive hemodynamic monitoring allowing monitoring of cardiac output and stroke volume
• Patient sufficiently sedated (BIS between 40 and 60) and/or curarized (TOF < 2/4 at the orbicularis) to avoid inspiratory effort
• Patient optimized on the hemodynamic level, in particular with regard to blood volume, following the data from hemodynamic monitoring and the recommendations of the French Society of Anesthesia and Resuscitation (RFE SFAR 2013 - Perioperative Vascular Filling Strategy)
• Patient covered by a Social Security plan
• Consent of close relatives or trusted person (if present)
• Patient admitted in polyvalent resuscitation within the Peri-Operative Medicine Unit of Clermont-Ferrand hospital suffering from respiratory distress syndrome for less than 24 hours

Exclusion Criteria:

• Contraindication to the use of cardiac output measurement by transpulmonary thermodilution
• Cardiac arrhythmia
• Severe valvulopathy
• Contraindication to the use of the Analysis of pulmonary aeration will be performed using the non-invasive technique of electrical impedance tomography with the placement of an electrode belt on the patient's chest. Values will be recorded with this belt :

technique

• Left ventricular ejection fraction (LVEF) < 45% and/or right ventricular failure
• History of pulmonary lobectomy and/or pneumectomy and/or known emphysema
• Patient with restrictive or obstructive lung disease
• Body mass index (BMI) < 16.5 or > 30 kg.m-2
• Pregnancy
• Major under legal protection (guardianship, curators, safeguard of justice)