Table 2.

Mortality and ventilator-free days across severity categories

	P/F ratio				P/FP ratio
Outcomes	Severe (≤ 100) N = 640	MoNderate (101–200) N = 1,928	Mild (201–300) N = 839	P value for trend	Severe (≤ 100) N = 794	Moderate (101–200) N = 1,252	Mild (201–300) N = 640	P value for trend
Hospital mortality, N (%)	295 (46.1)	549 (28.5)	204 (24.3)	< 0.001	340 (42.8)	358 (28.6)	161 (25.1)	< 0.001
Ventilator-free days (IQR)	3 (0–17)	17 (0–22)	21 (1.25–24)	< 0.001	1.5 (0–17)	17 (0–22)	19 (0–23)	< 0.001

P values refer to comparisons of hospital mortality and ventilator-free days between patients classified as having severe, moderate, and mild ARDS.  IQR  interquartile range, P/F =ratio of the PaO₂ to FiO₂; P/FP = (PaO₂ * 10)/(FiO₂ * PEEP)