<prompt> A criterion for diagnosis of acute respiratory distress syndrome is?PaO2FiO2 400 mm HgSlow onset dyspneaPaO2FiO2 _200 mm HgPCWPl8 mm Hg  <response>: ARDS is a clinical syndrome of severe dyspnoea of rapid onset,hypoxaemia,and diffuse pulmonary infiltrates leading to respiratory failure.The most definitive characteristic of ARDS is the aerial Po2 in mmHgFIo2inspiratory O2 fraction 200 mmHg,while a Pao2FIo2 between 200 and 300 identifies patients with acute lung injury who are likely to benefit from aggressive therapy. Reference:Harrisons Medicine-20th edition,page no:2032 