ARDS according to the Berlin Definition is defined as &;Severe ARDS&; when PaO2/FiO2 is = 5cm H2O. The Berlin definition of ARDS: The Berlin definition of ARDS-2012 aims to replace the American-European consensus conference&;s definition of ARDS-1994. The major changes to the Berlin Definition are that The term "Acute Lung Injury" Or &;ALI&; has been eliminated The Pulmonary capillary wedge pressure criterion has been removed Minimal ventilator settings have been added ARDS Berlin definition of acute respiratory distress syndrome: Timing: Within 1 week of known clinical insult or new or worsening respiratory symptoms Chest imaging: Bilateral opacities- not fully explained by effusions, lobar/lung collapse, or nodules Origin of edema: Respiratory failure not fully explained by cardiac failure or fluid overload. Need objective assessment to exclude hydrostatic edema if no risk factor is present Oxygenation: Mild: 200mmHg < PaO2/FiO2 = 5cm H2O Moderate: 100mmHg < PaO2/FiO2 = 5cmH2O Severe: PaO2/FiO2= 5 cm H2O Ref: Harrisons 20th edition