Table 1.

The characteristics of the patients included in the analysis. The ratio of arterial oxygen partial pressure to fraction of inspired oxygen ( $P{\mathrm{a}}_{{\mathrm{O}}_2}\text{:}F{\mathrm{I}}_{{\mathrm{O}}_2}$) was recorded at randomization. APACHE II, Acute Physiology and Chronic Health Evaluation score II, a unitless measure of overall illness severity at intensive care unit admission

Trial	Sites (n)	Patients (n)	Age [yr; mean (range)]	Males [n (%)]	APACHE II score [mean (sd)]	$P{\mathrm{a}}_{{\mathrm{O}}_2}\text{:}F{\mathrm{I}}_{{\mathrm{O}}_2}$ ratio [kPa; mean (sd)]
OSCAR		398	54.9 (16.2–90.1)	256 (64.3)	21.8 (6.0)	15.0 (4.9)
(intervention)
OSCAR		397	55.9 (18.8–88.3)	239 (60.2)	21.7 (6.1)	15.0 (5.1)
(control)
OSCAR	30	795	55.4 (16.2–90.1)	495 (62.3)	21.8 (6.1)	15.1 (5.1)
(overall)
HARP-2	40	539	53.9 (16.2–90.3)	307 (57.0)	18.9 (6.6)	17.1 (7.4)
(overall)
BALTI-2	46	326	55.5 (17.2–93.2)	212 (65.0)	19.2 (6.5)	13.8 (4.9)
(overall)
All studies		1660	54.9 (16.2–90.3)	1014 (60.1)	19.9 (6.4)	15.3 (5.75)