TABLE 1.

American–European Consensus Conference (AECC), Berlin and Kigali criteria for acute respiratory distress syndrome (ARDS)

	AECC definition	Berlin criteria	Kigali modification of Berlin criteria
Timing	Acute onset	Within 1 week of a known clinical insult or new or worsening respiratory symptoms	Within 1 week of a known clinical insult or new or worsening respiratory symptoms
Oxygenation	PaO2/FiO2 ≤200 mmHg (defined as acute lung injury if ≤300 mmHg)	Mild: PaO2/FiO2 >200 mmHg but ≤300 mmHg Moderate: PaO2/FiO2 >100 mmHg but ≤200 mmHg Severe: PaO2/FiO2 ≤100 mmHg	SpO2/FiO2 ≤315
PEEP requirement	None	Minimum 5 cmH2O PEEP required by invasive mechanical ventilation (noninvasive acceptable for mild ARDS)	No PEEP requirement, consistent with AECC definition
Chest imaging	Bilateral infiltrates seen on frontal chest radiograph	Bilateral opacities not fully explained by effusions, lobar/lung collapse or nodules by chest radiograph or CT	Bilateral opacities not fully explained by effusions, lobar/lung collapse or nodules by chest radiograph or ultrasound
Origin of oedema	Pulmonary artery wedge pressure <18 mmHg when measured or no evidence of left atrial hypertension	Respiratory failure not fully explained by cardiac failure or fluid overload (need objective assessment, such as echocardiography, to exclude hydrostatic oedema if no risk factor present)	Respiratory failure not fully explained by cardiac failure or fluid overload (need objective assessment, such as echocardiography, to exclude hydrostatic oedema if no risk factor present)

PEEP: positive end-expiratory pressure; P_aO2: arterial oxygen tension; F_iO2: inspiratory oxygen fraction; S_pO2: arterial oxygen saturation measured by pulse oximetry; CT: computed tomography.