 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 mlkg 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 mlkg 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: 