Low vs. High Inspiratory Oxygen Fraction During Mechanical Ventilation in Obese Patients: Impact on Postoperative Pulmonary Outcomes

Background Obese patients undergoing general anesthesia are at heightened risk for postoperative pulmonary complications (PPCs) due to impaired respiratory mechanics. While lung‐protective ventilation strategies are widely adopted, the role of intraoperative inspiratory oxygen fraction (FiO 2 ) in this population remains controversial. Methods We conducted a prospective, randomized controlled trial comparing low (FiO 2 40%) versus high (FiO 2 80%) intraoperative oxygen concentration in 113 obese patients undergoing elective laparoscopic bariatric surgery. All patients received standardized lung‐protective ventilation. The primary outcome was the incidence and severity of PPCs within 5 postoperative days. Secondary outcomes included hospital length of stay, mortality, postoperative nausea and vomiting (PONV), and surgical site infection (SSI). Results The incidence of PPCs was 70.7% in the high FiO 2 group and 55.5% in the low FiO 2 group ( p = 0.08). Grade ≥ 3 PPCs occurred only in the high FiO 2 group (3.4%). The average PPC severity score was lower in the low FiO 2 group (0.9 ± 0.9 vs. 1.2 ± 0.9, p = 0.08). No differences were observed in hospital stay, mortality, or SSI. PONV was more frequent in the low FiO 2 group (43.6% vs. 27.6%, p = 0.08). Conclusion Although the difference was not statistically significant, the observed lower incidence of PPCs in the low FiO 2 group may indicate a potential clinical effect. Larger, multicenter trials are warranted to confirm these results and optimize oxygen management in obese surgical patients. Trial Registration: Chinese Clinical Trial Registry: ChiCTR2300076656