Comparison 1. Mortality.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Hospital or 30‐day mortality	8	1779	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.72, 1.16]
2 Hospital or 30‐day mortality (Bollen 2005 and Mentzelopoulos 2012 participants lost to follow‐up censored)	8	1775	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.73, 1.16]
3 Hospital or 30‐day mortality (Shah 2004 post‐randomization withdrawals included)	8	1784	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.73, 1.16]
4 Hospital or 30‐day mortality: adult versus paediatric trials	8	1779	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.72, 1.16]
4.1 Adult trials	6	1705	Risk Ratio (M‐H, Random, 95% CI)	0.93 [0.71, 1.21]
4.2 Paediatric trials	2	74	Risk Ratio (M‐H, Random, 95% CI)	0.80 [0.44, 1.43]
5 Hospital or 30‐day mortality: lung‐protective ventilation mandatory vs non‐mandatory	8	1779	Risk Ratio (M‐H, Random, 95% CI)	0.92 [0.72, 1.16]
5.1 Lung‐protective ventilation not mandatory	4	1062	Risk Ratio (M‐H, Random, 95% CI)	0.94 [0.77, 1.15]
5.2 Lung‐protective ventilation mandatory	4	717	Risk Ratio (M‐H, Random, 95% CI)	0.85 [0.47, 1.53]
6 Hospital or 30‐day mortality (trials with low risk of bias)	3	959	Risk Ratio (M‐H, Random, 95% CI)	0.89 [0.68, 1.18]