Table 5.

Risk factors for postoperative pulmonary complications only in ever-smokers without restrictive pattern (a subgroup analysis)

	Univariate	Multivariate (all variables entered)	Multivariate (stepwise elimination)
	OR (95% CI)	OR (95% CI)	OR (95% CI)
Age	1.01 (0.95–1.07)	1.06 (0.97–1.17)
Body mass index	0.91 (0.77–1.08)	0.91 (0.72–1.16)
Charlson comorbidity index	1.17 (0.92–1.48)	1.24 (0.89–1.73)
ASA physical status	2.14 (1.07–4.27)*	0.92 (0.26–3.22)
Hospitalization within 1 year due to respiratory illness	14.25 (3.42–73.03)***	28.21 (3.85–206.51)**	18.75 (3.47–101.25)**
BUN	1.03 (0.98–1.07)	0.97 (0.88–1.07)
Emergency surgery	5.11 (1.51–16.71)**	3.95 (0.73–21.43)	3.92 (0.89–17.26)
Anesthesia time	1.00 (1.00–1.01)**	1.00 (0.99–1.01)
Laparoscopic surgery	0.33 (0.07–1.04)	0.27 (0.05–1.68)
Upper abdominal surgery	1.02 (0.36–3.33)	1.67 (0.33–8.54)
RBCs for transfusion	1.14 (1.06–1.31)*	1.20 (0.95–1.53)	1.17 (1.02–1.34)*
Mild-to-moderate COPD	0.42 (0.13–1.34)	0.26 (0.05–1.39)	0.34 (0.08–1.50)
Severe-to-very-severe COPD	1.46 (0.43–4.91)	2.06 (0.35–12.01)	1.85 (0.42–8.24)

Notes: COPD grade is defined as follows: mild-to-moderate COPD, FEV₁ ≥50% predicted with FEV₁/FVC <0.7; severe-to-very-severe COPD, FEV₁ <50% predicted with FEV₁/FVC <0.7. Restrictive disease is defined as FVC <80% predicted with FEV₁/FVC ≥0.7.

^*P<0.05;

^**P<0.01;

^***P<0.001. The variable Gender (male) was omitted in this table, because the subgroup had only 2 female patients.

Abbreviations: ASA, American Society of Anesthesiologists; BUN, blood urea nitrogen; CI, confidence interval; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 s; FVC, forced vital capacity; OR, odds ratio; RBC, red blood cell.