Comparison of low and high inspiratory oxygen fraction added to lung- protective ventilation on postoperative pulmonary complications after abdominal surgery: A randomized controlled trial

Study objective: Intraoperative lung-protective ventilation strategy has been recommended to reduce postoperative pulmonary complications (PPCs). However, the role of inspiratory oxygen fraction (FiO(2)) in this protection remains highly uncertain. We aimed to evaluate the effect of intraoperative low (30%) versus high (80%) FiO(2) in the context of lung-protective ventilation strategy on PPCs in patients undergoing abdominal surgery. Design: Prospective, two-arm, randomized controlled trial. Setting: Tertiary university hospital in China. Patients: A total of ASA I-III 252 patients aged >= 18, who were scheduled for elective abdominal surgery under general anesthesia were included in the study. Intervention: Patients were randomly assigned to receive either 30% or 80% FiO(2) during the intraoperative period. All patients received volume-controlled mechanical ventilation with lung-protective ventilation approach, which included a tidal volume of 8 ml kg(-1) of predicted body weight, a positive end-expiratory pressure level of 6-8 cmH(2)O, and repeated recruitment maneuvers. Measurements: The primary outcome was a composite of postoperative pulmonary complications within the first 7 postoperative days, consisting of respiratory infection, respiratory failure, bronchospasm, atelectasis, pleural effusion, pneumothorax, and aspiration pneumonitis. The severity grade of PPCs was measured as a key secondary outcome. Main results: Two hundred and fifty-one patients completed the trial. PPCs occurred in 43 of 125 (34.4%) patients assigned to receive 30% FiO(2) compared with 59 of 126 (46.8%) patients receiving 80% FiO(2) (relative risk 0.74, 97.5% confidence interval, 0.51-1.02, p = 0.045, > 0.025). The severity of PPCs within the first 7 days following surgery was attenuated significantly in the low (30%) FiO(2) group (p = 0.001). Conclusions: Among patients undergoing abdominal surgery under general anesthesia, an intraoperative lung protective ventilation strategy with 30% FiO(2) compared with 80% FiO(2) did not reduce the incidence of PPCs. And the use of 30% FiO(2) resulted in less severe pulmonary complications.