Respiratory symptoms developed/aggravated within 1 week after clinically known damage
Hypoxemia
PaO2/FiO2 201–300 mmHg, PEEP or CPAP ≥5 cmH2O
PaO2/FiO2 101–200 mmHg, PEEP≥5 cmH2O
PaO2/FiO2 ≤ 100 mmHg, PEEP≥10 cmH2O
Causes of pulmonary edema
Respiratory failure cannot be completely explained by heart failure or fluid overload. Objective assessment (such as echocardiography) is needed to eliminate the possibility of hydrostatic pulmonary edema if other risk factor is absent.
Abnormality in imaging
Decreased transparence of two lungs cannot be completely explained by pleural effusion, atelectasis or nodules.