Table 2

Recommended criteria for definition of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Modified from Bernard et al⁴²

	Timing	Oxygenation	Chest radiograph	Pulmonary artery wedge pressure
ALI	Acute onset	Pao₂/Fio₂ ⩽40 kPa (regardless of PEEP level)	Bilateral infiltrates on frontal chest radiograph	⩽18 mm Hg or no clinical evidence of left atrial hypertension
ARDS	Acute onset	Pao₂/Fio₂ ⩽26.7 kPa (regardless of PEEP level)	Bilateral infiltrates on frontal chest radiograph	⩽18 mm Hg or no clinical evidence of left atrial hypertension