Table 4.

Intraoperative events

Variable	All patients	Low risk of PPCs	Increased risk of PPCs	Relative Risk (95% CI)	P
Any de-saturation	3.9 (387/9844)	3.3 (219/6736)	5.6 (150/2658)	1.78 (1.44 to 2.20)	<0.001
Unplanned recruitment manoeuvre	3.4 (332/9837)	2.5 (171/6731)	5.6 (148/2657)	2.26 (1.81 to 2.83)	<0.001
Ventilatory pressure reduction	2.9 (282/9830)	2.2 (147/6730)	4.6 (122/1651)	2.16 (1.69 to 2.76)	<0.001
Expiratory flow limitation	0.5 (52/9786)	0.4 (25/6703)	0.9 (24/2635)	2.45 (1.40 to 4.31)	0.001
Hypotension	26.6 (2617/9845)	23.7 (1594/6737)	35.3 (939/2659)	1.76 (1.60 to 1.94)	<0.001
Vasoactive drugs	22.4 (2208/9845)	18.5 (1246/6737)	33.7 (897/2659)	2.24 (2.03 to 2.48)	<0.001
New arrhythmias	0.6 (60/9838)	0.4 (24/6732)	1.2 (32/2657)	3.41 (2.00 to 5.79)	<0.001

Low versus increased risk of PPCs, according to the Assess Respiratory Risk in Surgical Patients in Catalonia risk (ARISCAT) score (<26 versus ≥26, respectively).

Data are presented as % (n/N). Comparison of differences within a subgroup is performed by using the t-test for continuous variables and χ² for categorical variables.

CI, confidence interval; n, number with characteristic; PPC, postoperative pulmonary complication; N, number in group or subgroup.

Definitions of intraoperative events: Any de-saturation, defined as the occurrence of SpO₂ <92%; unplanned recruitment manoeuvre, ventilation strategies aimed at restoring lung aeration; ventilation pressure reduction, ventilation strategies aimed at lowering peak and/or plateau pressures; expiratory flow limitation, defined as expiratory flow higher than zero at end-expiration as suggested by visual analysis of the expiratory gas flow curve; hypotension, defined as systolic arterial pressure <90 mmHg for 3 min or longer; need for vasoactive drugs, defined as any vasoactive drug given to correct hypotension; new-onset arrhythmias, defined as new onset of atrial fibrillation, sustained ventricular tachycardia, supraventricular tachycardia, or ventricular fibrillation.