- Patients must have acute onset of ARDS, as defined by the American-European Consensus Conference (AECC) criteria for ARDS: (i) having an initiating clinical condition (pneumonia, aspiration, inhalation injury, sepsis, trauma, acute pancreatitis, etc.; (ii) bilateral infiltrates on frontal chest radiograph; (iii) absence of left atrial hypertension, a pulmonary capillary wedge pressure (PCWP) less than 18 mm Hg, or no clinical signs of left heart failure; (iv) severe hypoxemia (a PaO2/FIO2 <200 mm Hg, regardless of FIO2 or positive end-expiratory pressure (PEEP)