Efficacy of prone position in acute respiratory distress syndrome patients: A pathophysiology-based review

Table 1 The Berlin definition of the acute respiratory distress syndrome

Timing	Within 1 wk of a known clinical insult or new or worsening respiratory symptoms
Chest imaging1	Bilateral opacities - not fully explained by effusions, lobar/lung collage, or nodules
Origin of edema	Respiratory failure not fully explained by cardiac failure of fluid overload. Need objective assessment (e.g., echocardiography) to exclude hydrostatic edema if no risk factor present
Oxygenation2
Mild	200 mmHg < PaO2/FiO2 ≤ 300 mmHg with PEEP or
	CPAP ≥ 5 cmH2O3
Moderate	100 mmHg < PaO2/FiO2 ≤ 200 mmHg with PEEP or
	CPAP ≥ 5 cmH2O
Severe	PaO2/FiO2 ≤ 100 mmHg with PEEP or CPAP ≥ 5 cmH2O

¹Chest radiograph or computed tomography scan;

²If attitude is higher than 1000 m, the correction factor should be calculated as follows: [PaO₂/FiO₂× (barometric pressure/760)].

³This may be delivered noninvasively in the mild acute respiratory distress syndrome group. CPAP: Continuous positive airway pressure; FiO₂: Fraction of inspired oxygen; PaO₂: Partial pressure of arterial oxygen; PEEP: Positive-end expiratory pressure.