Pronation During Veno-venous Extra Corporeal Membrane Oxygenation

The Acute Respiratory Distress Syndrome (ARDS) is defined by a recent (within 1 week) respiratory failure, not fully explained by cardiac failure or fluid overload. ARDS is also characterized by bilateral opacities at the chest imaging, with an alteration of the oxygenation while positive end-expiratory pressure equal or greater than 5 cmH2O is applied. Severe ARDS is characterized by a high mortality. In the most severe ARDS patients, venovenous extracorporeal membrane oxygenation (vv-ECMO) is increasingly accepted as a mean to support vital function, although not free from complications. In patients with severe ARDS, prone position has been used for many years to improve oxygenation. In these patients, early application of prolonged (16 hours) prone-positioning sessions significantly decreased 28-day and 90-day mortality. More recently, prone position and ECMO have been coupled as concurrent treatment. Indeed, the addition of prone positioning therapy concurrently with ECMO can aid in optimizing alveolar recruitment, and reducing ventilator-induced lung injury. Nowadays, few data exist on respiratory mechanics modifications before and after the application of prone position in patients with severe ARDS receiving vv-ECMO. The investigators have therefore designed this observational study to assess the modifications of mechanical properties of the respiratory system, ventilation and aeration distribution, and hemodynamics occurring during ECMO before and after prone position in patients with severe ARDS.