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

Abstract

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 (FiO₂) in this population remains controversial.

Methods: We conducted a prospective, randomized controlled trial comparing low (FiO₂ 40%) versus high (FiO₂ 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 FiO₂ group and 55.5% in the low FiO₂ group (p=0.08). Grade ≥ 3 PPCs occurred only in the high FiO₂ group (3.4%). The average PPC severity score was lower in the low FiO₂ 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 FiO₂ 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 FiO₂ 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.