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

TL;DR

This study compares low and high oxygen levels during surgery in obese patients and finds that lower oxygen may reduce postoperative lung issues.

Contribution

The study investigates the impact of inspiratory oxygen fraction on postoperative pulmonary outcomes in obese patients, a novel focus in this population.

Findings

Lower FiO2 (40%) was associated with a trend toward fewer postoperative pulmonary complications compared to higher FiO2 (80%).

Grade ≥ 3 complications occurred only in the high FiO2 group.

No significant differences were found in hospital stay, mortality, or surgical site infections.

Abstract

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.

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).

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).

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

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