Intraoperative PEEP Strategy and Postoperative Pulmonary Complications in Obese Patients: A Randomized Trial with Exploratory Analysis of Smoking Status

Background: Obesity increases the risk of postoperative pulmonary complications (PPCs), and active smoking may further amplify this risk. Whether smoking status identifies a subgroup of obese surgical patients with differential PPC risk or a different response to intraoperative Positive End-Expiratory Pressure (PEEP) strategy remains unclear. We evaluated whether smoking status influences PPCs and modifies the effect of intraoperative PEEP strategy in obese patients undergoing surgery. Methods: In this single-center randomized trial, 95 obese surgical patients were assigned to either a low-PEEP strategy (4 cmH2O without recruitment maneuvers) or a high-PEEP strategy (12 cmH2O with recruitment maneuvers). The primary endpoint was PPC incidence within 5 postoperative days in the overall randomized population. Smoking status was recorded at baseline, and pre-specified exploratory subgroup analyses assessed PPC incidence according to smoking status and the smoking-by-PEEP interaction. Results: The overall incidence of postoperative pulmonary complications (PPCs) was 8.9% in the low-PEEP group and 8.0% in the high-PEEP group (p > 0.05). Among smokers, complications occurred in 18.2% in the low-PEEP group and 11.8% in the high-PEEP group. For non-smokers, rates were 5.9% and 6.1%, respectively. No statistically significant differences were observed. Conclusions: Active smoking was associated with a numerically higher incidence of PPCs in obese patients; however, this finding was not statistically significant. The high-PEEP strategy with recruitment maneuvers did not reduce PPC incidence compared with the low-PEEP strategy. Trial Registration: Approval number 003208/2016.