Lateral Positioning and Prone Positioning in ARDS Patients

Primary objective: assessment of the distribution of tidal volume after lateralization and according to the position (supine position SP, prone position, PP) by measuring global and regional changes (4 regions of interest from the retrosternal region to the prevertebral region) of pulmonary aeration assessed by electrical impedance tomography (EIT). The primary endpoint will be the change in pulmonary aeration after lateralization in SP (T2) and in PP (T5) estimated by the change in end-expiratory lung impedance (EELI) = [ΔEELI x (VT/ΔZ)] where VT is the tidal volume and ΔZ is the impedance change.

Main secondary objective: assessment of perfusion and gas exchange after each period of lateralization compared to the baseline period in supine position (baseline SP) and in ventral position (baseline PP) (endpoints: PaO2/FiO2 and PaCO2)

Other secondary objectives:

• Evaluation of the percentage of patients who, at the end of the period of lateralization in supine position (T2), have a PaO2/FiO2 ratio > 150
• Comparisons baseline SP with baseline PP, PP 6 hours, PP and lateral positioning (LP) 12 hours and return to supine position since 1 hour (End) for pulmonary aeration, gas exchange and ventilatory parameters (endpoints: PaO2/FiO2 and PaCO2, (EELI) = [ΔEELI x (VT/ΔZ)], plateau pressure, driving pressure).
• Baseline PP comparisons with PP 6 hours, PP and lateral positioning (LP) 12 hours and return to supine position since 1 hour (End) for pulmonary aeration, gas exchange and ventilatory parameters (endpoints: PaO2/FiO2 and PaCO2, (EELI) = [ΔEELI x (VT/ΔZ)], plateau pressure, driving pressure)
• LP comparisons in SP for 6 hours with LP in PP for 12 hours for pulmonary aeration, gas exchange and ventilatory parameters (endpoints: PaO2/FiO2 and PaCO2, (EELI) = [ΔEELI x (VT/ΔZ)], plateau pressure, driving pressure)
• LP comparisons in PP for 12 hours with return to supine position since 1 hour (End) for pulmonary aeration, gas exchange and ventilatory parameters (endpoints: PaO2/FiO2 and PaCO2, (EELI) = [ΔEELI x (VT/ΔZ)], plateau pressure, driving pressure) : PaO2/FiO2 and PaCO2, (EELI) = [ΔEELI x (VT/ΔZ)], plateau pressure, driving pressure)
• Evaluate the adverse effects related to the use of lateral positioning.

Inclusion criteria

• Age of at least 18 years
• ARDS evolving for less than 5 days with a PaO2/FiO2 ratio (P/F ratio) < 150 after optimization of PEEP (P/V curve, R/I ratio), curarization and without prior use of the PP since orotracheal intubation.
• Obtained written consent of the patient, one of his relatives or the previously designated trusted person. As soon as possible, the patient will be informed and his written consent will be obtained
• Beneficiary of health insurance coverage
• Possibility of participating in any other studies whose evaluation criteria do not interfere with those of the study

Non-inclusion criteria:

Patients with at least one of the following criteria will not be eligible:

• Refusal to participate
• Pregnant, parturient or breastfeeding women
• Intracranial pressure > 30 mm Hg or cerebral perfusion pressure < 60 mmHg
• Severe chronic respiratory disease with oxygen therapy or mechanical ventilation at home (except CPAP/BIPAP for obstructive sleep apnea)
• Chronic interstitial lung diseases
• Patients on ECMO
• Weight > 100 kg
• Severe liver disease Child-Pugh score 12-15
• Pneumothorax
• SAPS II score > 75 at inclusion
• Unstable spinal fracture
• Contraindications to EIT (pacemaker, implantable defibrillator, skin lesions between the 4th and 5th ribs).
• Withdrawal (except for ECMO) or witholding treatment decision
• Any other reason which, according to the investigator, could interfere with the evaluation of the study objectives
• Person under legal protection measure (guardianship, curatorship, etc.)
• Person deprived of liberty by a judiciary or administrative decision

Exclusion criteria

• Patients who will be unable to complete the 25-hour intervention due to worsening requiring ECMO, death or organizational problems will be excluded from the analysis.