Table 3.

Subgroup analyses

Outcome	No studies (no of patients)	Summary estimate (95% CI)	P value (summary estimate)	P value (heterogeneity)	I2 (%)
Reintubation	9 (1107)	0.38* (0.23 to 0.61)	0.0001	0.64	0
Cardiac surgery	3 (585)	0.43* (0.05 to 3.72)	0.44	0.14	49
Thoracic surgery	5 (338)	0.36* (0.20 to 0.64)	0.0005	0.73	0
RCT	6 (745)	0.39* (0.17 to 0.87)	0.02	0.41	1
Non-RCT	3 (362)	0.37* (0.20 to 0.69)	0.002	0.60	0
Min target SPO2(90%–93%)	3 (476)	0.41* (0.09 to 1.92)	0.26	0.11	55
Min target SPO2 (95%)	4 (399)	0.31* (0.09 to 1.01)	0.05	0.72	0
Prophylactic	7 (1143)	0.46* (0.21 to 1.03)	0.06	0.53	0
Therapy	3 (184)	0.34* (0.18 to 0.62)	0.0005	0.45	0
High risk of reintubation	7 (879)	0.35* (0.20 to 0.60)	0.0002	0.48	0
Escalation rate of respiratory support	10 (1327)	0.43* (0.26 to 0.73)	0.002	0.02	54
Cardiac surgery	3 (585)	0.45* (0.25 to 0.81)	0.008	0.51	0
Thoracic surgery	5 (338)	0.31* (0.18 to 0.53)	0.0001	0.47	0
RCT	7 (965)	0.46* (0.22 to 0.93)	0.03	0.01	64
Non-RCT	3 (362)	0.37* (0.20 to 0.69)	0.002	0.60	0
Min target SPO2(90%–93%)	3 (476)	0.39* (0.23 to 0.67)	0.0005	0.34	8
Min target SPO2 (95%)	5 (619)	0.46* (0.15 to 1.44)	0.18	0.01	70
Prophylactic	7 (1143)	0.50* (0.25 to 1.00)	0.05	0.02	59
Therapy	3 (184)	0.34* (0.19 to 0.60)	0.0002	0.45	0
High risk of reintubation	7 (879)	0.33* (0.22 to 0.49)	0.00001	0.5	0
PPCs	5 (606)	0.87* (0.70 to 1.08)	0.21	0.92	0
RCT	4 (422)	0.86* (0.69 to 1.086)	0.20	0.83	0
Prophylactic	4 (558)	0.86* (0.68 to 1.08)	0.20	0.87	0
Mortality	5 (942)	0.45* (0.16 to 1.29)	0.14	0.79	0
Cardiac surgery	1 (340)	1.01* (0.06 to 16.05)	0.99	–	–
Thoracic surgery	2 (198)	0.26* (0.03 to 2.25)	0.22	–	–
RCT	3 (670)	0.77* (0.17 to 3.41)	0.73	0.82	0
Non-RCT	2 (272)	0.27* (0.06 to 1.18)	0.08	0.98	0
Min target SPO2(90%–93%)	2 (428)	0.41* (0.08 to 2.09)	0.29	0.45	0
Min target SPO2 (95%)	2 (330)	0.69* (0.12 to 4.06)	0.68	–	–
High risk of reintubation	3 (538)	0.41* (0.08 to 2.09)	0.29	0.45	0

*Relative risk.

PPCs, postoperative pulmonary complications; RCT, randomised controlled trial.