Table 3.

Outcomes within the first 7 days after surgery of unmatched patients and matched patients after propensity scoring

	Unmatched patients				Matched patients
	Low PEEP (n=1032)	High PEEP (n=873)	Relative risk (95% CI)	P value	Low PEEP (n=643)	High PEEP (n=643)	Relative risk (95% CI)	P value
Primary outcomes
All PPCs	176 (17.1%)	138 (15.8%)	0.913 (0.716 to 1.165)	0.465	116 (18.0%)	88 (13.7%)	0.720 (0.533 to 0.974)	0.033
Respiratory failure	45 (4.4%)	39 (4.5%)	1.026 (0.661 to 1.590)	0.910	23 (3.6%)	29 (4.5%)	1.273 (0.728 to 2.226)	0.396
Pulmonary infection	99 (9.6%)	83 (9.5%)	0.990 (0.729 to 1.346)	0.950	73 (11.4%)	50 (7.8%)	0.658 (0.451 to 0.961)	0.029
Pleural effusion	7 (0.7%)	5 (0.6%)	0.843 (0.267 to 2.667)	0.711*	3 (0.5%)	4 (0.6%)	1.335 (0.298 to 5.991)	0.704*
Atelectasis	37 (3.6%)	20 (2.3%)	0.631 (0.363 to 1.095)	0.099	24 (3.7%)	11 (1.7%)	0.449 (0.218 to 0.924)	0.026
Pneumothorax	0	0			0	0
Bronchospasm	4 (0.4%)	3 (0.3%)	0.886 (0.198 to 3.970)	1.000*	4 (0.6%)	0	0.994 (0.988 to 1.000)	0.124 *
Aspiration pneumonitis	0	0			0	0
Secondary outcomes
Reintubation	19 (1.8%)	11 (1.3%)	0.680 (0.322 to 1.438)	0.310	16 (2.5%)	8 (1.2%)	0.494 (0.210 to 1.162)	0.099
Unplanned ICU admission	35 (3.4%)	24 (2.7%)	0.805 (0.475 to 1.365)	0.420	24 (3.7%)	16 (2.5%)	0.658 (0.346 to 1.251)	0.199
Hospital stays (days)	12 (10–15)	12 (10–14)		0.180	12 (10–15)	12 (10–14)		0.058

*Fisher's exact test.

ICU, intensive care unit; PEEP, positive end-expiratory pressure; PPCs, postoperative pulmonary complications.