Enhanced Lung Protective Ventilation for ARDS Patients With PrismaLung

Acute Respiratory Distress Syndrome (ARDS) still remains associated with a mortality rate of 30 - 45 % despite improvement in mechanical ventilation. Driving pressure, defined as the difference between the end-inspiratory and the end-expiratory airway pressure, appears as an important factor contributing to mortality in patients with the ARDS. In patients already receiving a conventional tidal volume of 6 ml/kg predicted body weight (PBW), a driving pressure ≥ 14 cmH2O increases the risk of death in the hospital. One mean to lower the driving pressure is to decrease the tidal volume such that from 6 to 4 ml/kg predicted body weight. However, this strategy promotes hypercarbia by reducing the alveolar ventilation, providing the respiratory rate is constant. In this setting, implementing an extracorporeal CO2 removal (ECCO2R) therapy may offset the associated hypercarbia. The investigators have previously demonstrated that combining a membrane oxygenator within an hemofiltration circuit provides efficacious low flow ECCO2R on a renal replacement therapy monitor. In this study, we thought to investigate the efficacy of the PrismaLung stand-alone therapy. Using a PrismaFlex monitor and a HP-X circuit, a neonatal membrane oxygenator (PrismaLung) is used to provide decarboxylation without renal replacement therapy. The study will consist in three periods: * The first period will address the efficacy of the PrismaLung device at tidal volume of 6 and 4 ml/kg PBW using an off-on-off design. * The second part of the study will investigate the effect of varying the sweep gas flow and the mixture of the sweep gas on the CO2 removal rate (random order). * The third part will compare three ventilatory strategies applied in a cross-over design : 1. Minimal distension: Tidal volume 4 ml/kg PBW and positive end-expiratory pressure (PEEP) based on the ARDSNet PEEP/FiO2 table (ARMA). 2. Maximal recruitment: 4 ml/kg PBW and PEEP adjusted to maintain a plateau pressure between 23