 The protocol has been approved by the Scientific Committees of Evaggelismos Hospital and of Larissa University Hospital. Informed consent will be requested from the next-of-kin of participation-eligible patients. Patients will be informed of the trial and their right to withdraw as soon as clinically feasible. Eligibility criteria are presented in the appropriate section of this report. In brief, the major inclusion criteria will comprise 1 early diagnosis established within the preceding 72 h ARDS according to the American-European Consensus Conference Definition 6; 2 severe oxygenation disturbances defined as PaO2FiO2 150 mm Hg, while ventilated with a positive end-expiratory pressure PEEP of 8 cm H2O criterion for severe ARDS; and 3 age 18-75 years and body weight 40 kg. Patient monitoring will include electrocardiographic lead II, hemodynamics continuous intraarterial and central-venous pressure, and cardiac outputindex by PICCO-plus Pulsion Medical Systems, Munich, Germany, and peripheral oxygen saturation SpO2. Deep sedation propofolmidazolam 8,9, analgesia fentanylremifentanil 9, and intermittent neuromuscular blockade cisatracurium 8,10 will be used. 