Fluid Responsiveness Prediction During Prone Position

Inclusion Criteria: * adult patient (including patient under protective measures/wardship) * with ARDS as defined by the Berlin criteria * in the prone position as per international guidelines * with a calibrated continuous cardiac output monitoring device * with a clinical indication for a fluid bolus as prescribed by the clinician in charge, and fulfilling at least 2 clinical criteria: mottles, tachycardia, hypotension, drop in cardiac output, oliguria, high arterial lactate concentration, or any other detailed criterion * with no respiratory efforts Exclusion Criteria: * acute cor pulmonale * patient treated with veno-venous extra-corporeal membrane oxygenation * hemorrhagic shock * Child-Pugh C cirrhosis * death expected to occur in less than 24h * decision to withhold or suspend active treatments * intracranial hypertension * lower limb amputation * obstruction of the inferior vena cava * acute abdominal syndrome * absence of consent to participate * pregnancy * patient previously enrolled in the same study * lack of affiliation to a social security regimen, as per French legislation * patient deprived of its liberty