Table 1.

The Berlin definition of acute respiratory distress syndrome

Timing	Within 1 week of a known clinical insult or new or worsening respiratory symptoms
Chest imaging	Bilateral opacities—not fully explained by effusions, lobar/lung collapse or nodules a
Origin of edema	Respiratory failure not fully explained by cardiac failure or fluid overload Need objective assessment (e.g., echocardiography) to exclude hydrostatic edema if no risk factor present
Oxygenation
Mild	200 mmHg < PaO2/FiO2 ≤ 300 mmHg with PEEP or CPAP ≥ 5 cm H2O b, c
Moderate	100 mmHg < PaO2/FiO2 ≤ 200 mmHg with PEEP ≥ 5 cm H2O
Severe	PaO2/FiO2 ≤ 100 mmHg with PEEP ≥ 5 cm H2O

Abbreviations: CPAP, continuous positive airway pressure; F_iO2, fraction of inspired oxygen; P_aO2, partial pressure of arterial oxygen; PEEP, positive end-expiratory pressure

^a Chest radiograph or computed tomography scan

^b If altitude is higher than 1000 m, the correction factor should be calculated as follows: [P_aO2/F_iO2 × (barometric pressure/760)]

^c This may be delivered noninvasively in the mild acute respiratory distress syndrome group