Predictors of 30-Day Pulmonary Complications after Outpatient Surgery: Relative Importance of Body Mass Index Weight Classifications in Risk Assessment.

BACKGROUND: Current literature is controversial regarding the importance of obese BMI classifications as a risk factor for pulmonary complications after outpatient surgery. The objective of the current investigation was to evaluate predictors of pulmonary outcomes after outpatient surgery and to assess the importance of BMI weight classifications in risk assessment. STUDY DESIGN: Patients with "outpatient" recorded as their inpatient/outpatient status in the 2012 to 2013 NSQIP database were included. The primary outcome of interest was the occurrence of a new pulmonary complication (eg pneumonia, pulmonary embolism, unplanned intubation, or ventilator-assisted respiration for greater than 48 hours) within 30 days of surgery. RESULTS: There were 444,532 cases included in the final analysis. There were 996 (0.22%; 99% CI 0.21% to 0.24%) all-cause pulmonary complications. Binary logistic regression identified BMI as an independent predictor of a pulmonary complication, unadjusted odds ratio 1.091 (99.75% CI 1.026 to 1.160) per 5 kg/m2 change in BMI, p < 0.001. Adjusted odds of a pulmonary complication with a BMI of 35 to 39.99 kg/m2 was 1.44 (99.75% CI 1.01 to 2.06; p = 0.002) and with a BMI of 40 to 49.99 kg/m2 was 1.68 (99.75% CI 1.13 to 2.50; p < 0.001) compared with a BMI of 18.5 to 24.99 kg/m2. CONCLUSIONS: Obese classes II and III were associated with an independent risk of a pulmonary complication. The risk associated with obesity was low compared with the risk associated with advanced age, prolonged surgical duration, and the risk of comorbidities including congestive heart failure, COPD, and renal failure.