Tae Hoon Kim, Jae Seung Lee, Sei Won Lee, Yeon-Mok Oh Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea Abstract: Postoperative pulmonary complications (PPCs) are one of the most important causes of postoperative morbidity and mortality after abdominal surgery. Although chronic obstructive pulmonary disease (COPD) has been considered a risk factor for PPCs, it remains unclear whether mild-to-moderate COPD is a risk factor. This retrospective cohort study included 387 subjects who underwent abdominal surgery with general anesthesia in a tertiary referral hospital. PPCs included pneumonia, pulmonary edema, pulmonary thromboembolism, atelectasis, and acute exacerbation of COPD. Among the 387 subjects, PPCs developed in 14 (12.0%) of 117 patients with mild-to-moderate COPD and in 13 (15.1%) of 86 control patients. Multiple logistic regression analysis revealed that mild-to-moderate COPD was not a significant risk factor for PPCs (odds ratio [OR] =0.79; 95% confidence interval [CI] =0.31–2.03; P=0.628). However, previous hospitalization for respiratory problems (OR =4.20; 95% CI =1.52–11.59), emergency surgery (OR =3.93; 95% CI =1.75–8.82), increased amount of red blood cell (RBC) transfusion (OR =1.09; 95% CI =1.05–1.14 for one pack increase of RBC transfusion), and laparoscopic surgery (OR =0.41; 95% CI =0.18–0.93) were independent predictors of PPCs. These findings suggested that mild-to-moderate COPD may not be a significant risk factor for PPCs after abdominal surgery.Keywords: postoperative pulmonary complications, spirometry, risk factor, abdominal surgery, postoperative complications, postoperative care