Comparison 1. Pulmonary artery perfusion with blood versus no perfusion during cardiopulmonary bypass.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 All‐cause mortality (at maximum follow‐up)	4	210	Peto Odds Ratio (Peto, Fixed, 95% CI)	1.78 [0.43, 7.40]
1.1 Low risk of bias	1	60	Peto Odds Ratio (Peto, Fixed, 95% CI)	1.65 [0.27, 10.15]
1.2 High or uncertain risk of bias	3	150	Peto Odds Ratio (Peto, Fixed, 95% CI)	2.00 [0.20, 20.03]
2 Participants with 1 or more SAEs (at maximum follow‐up)	3	180	Risk Ratio (M‐H, Random, 95% CI)	1.12 [0.66, 1.89]
2.1 Low risk of bias	1	60	Risk Ratio (M‐H, Random, 95% CI)	0.95 [0.74, 1.20]
2.2 High or uncertain risk of bias	2	120	Risk Ratio (M‐H, Random, 95% CI)	1.56 [0.84, 2.93]
3 Participants with 1 or more SAEs stratified according to preoperative lung function	3	180	Risk Ratio (M‐H, Random, 95% CI)	1.12 [0.66, 1.89]
3.1 Patients with normal lung function	1	64	Risk Ratio (M‐H, Random, 95% CI)	0.33 [0.01, 7.89]
3.2 Patients with COPD	2	116	Risk Ratio (M‐H, Random, 95% CI)	1.18 [0.63, 2.23]
4 Participants with 1 or more SAEs stratified according to short‐ or long‐term follow‐up	3	180	Risk Ratio (M‐H, Random, 95% CI)	1.12 [0.66, 1.89]
4.1 Short‐term follow‐up (< 30 days)	1	64	Risk Ratio (M‐H, Random, 95% CI)	0.33 [0.01, 7.89]
4.2 Long‐term follow‐up (≧ 30 days)	2	116	Risk Ratio (M‐H, Random, 95% CI)	1.18 [0.63, 2.23]
5 Last measured PaO2 /FiO2 ratio (mmHg)	3	119	Mean Difference (IV, Random, 95% CI)	27.80 [5.67, 49.93]
5.1 Low risk of bias	1	59	Mean Difference (IV, Random, 95% CI)	39.67 [‐16.33, 95.67]
5.2 High or uncertain risk of bias	2	60	Mean Difference (IV, Random, 95% CI)	25.60 [1.51, 49.70]
6 Last measured PaO2 /FiO2 ratio (mmHg) stratified according to preoperative lung function	3	119	Mean Difference (IV, Random, 95% CI)	27.80 [5.67, 49.93]
6.1 Participants with normal lung function	2	60	Mean Difference (IV, Random, 95% CI)	25.60 [1.51, 49.70]
6.2 Participants with COPD	1	59	Mean Difference (IV, Random, 95% CI)	39.67 [‐16.33, 95.67]
7 Intubation time (hours) after primary surgery	4	176	Mean Difference (IV, Random, 95% CI)	‐0.35 [‐1.12, 0.42]
7.1 Low risk of bias	1	60	Mean Difference (IV, Random, 95% CI)	‐1.0 [‐2.24, 0.24]
7.2 High or uncertain risk of bias	3	116	Mean Difference (IV, Random, 95% CI)	‐0.02 [‐0.39, 0.35]
8 Intubation time (hours) stratified according to preoperative lung function	4	176	Mean Difference (IV, Random, 95% CI)	‐0.35 [‐1.12, 0.42]
8.1 Participants with normal lung function	2	60	Mean Difference (IV, Random, 95% CI)	‐0.61 [‐2.92, 1.71]
8.2 Participants with COPD	2	116	Mean Difference (IV, Random, 95% CI)	1.00 [‐2.24, 0.24]