Postoperative Pulmonary Complications in the Morbidly Obese: The Role of Tidal Volume and Type of Abdominal Surgery

BACKGROUND: The patient who is morbidly obese is not adequately represented in the evidence recommending intraoperative low tidal volume (V_T) ventilation. We aimed to explore the association between V_T adjusted for ideal body weight (IBW) and the occurrence of postoperative pulmonary complications in subjects who were morbidly obese and undergoing abdominal surgery, as well as its implications on intraoperative ventilatory variables.

METHODS: We included 734 subjects with a body mass index of at least 40 kg/m², undergoing open or laparoscopic abdominal surgery that lasted for at least 120 min. Clinical variables were obtained to estimate the preoperative pulmonary risk as well as intraoperative ventilator data to perform associations. Outcomes were defined by medical billing code diagnoses and oxygen use. All data were collected electronically by using Structured Query Language.

RESULTS: The subjects received a mean V_T/IBW of 9.41 mL/kg IBW, and postoperative pulmonary complications occurred in 7.5% of the subjects. The occurrence of complications was correlated with the presence of several preoperative risk factors for postoperative pulmonary complications. V_T/IBW was not associated with postoperative pulmonary complications. This finding remained present after separating different levels of V_T/IBW. In a multivariate analysis, only laparoscopic surgery was an independent protective factor against postoperative pulmonary complications (odds ratio 0.07, 95% CI 0.01–0.55).

CONCLUSIONS: V_T/IBW was not associated with the occurrence of postoperative pulmonary complications in subjects who were morbidly obese and undergoing prolonged abdominal surgery. Future prospective studies are indicated to guide the optimum ventilation strategy for patients who are morbidly obese.