Higher fraction of inspired oxygen during anesthesia increase the risk of postoperative pulmonary complications in patients undergoing non-cardiac surgery: A retrospective cohort study

Abstract Objective The ideal intraoperative inspired oxygen concentration remains controversial. We aimed to investigate the association between the level of intraoperative fraction of inspired oxygen (FiO2) and the incidence of postoperative pulmonary complications (PPCs) in patients undergoing non-cardiac surgery. Methods This was a retrospective cohort study of elderly patients with non-cardiac surgery between April 2020 and January 2022. According to the intraoperative FiO2, patients were divided into low (≤ 60%) and high (> 60%) FiO2 groups. The primary outcome was the incidence of a composite pulmonary complications (PPCs) within 7 days postoperatively. Propensity score matching (PSM) and inverse probability treatment weighting (IPTW) were used to adjust for differences in baseline characteristics between the two groups. The odds ratio (OR) of FiO2 and PPCs was calculated using multivariate logistic regression analysis. Results Of the 3515 patients included, with a median age of 70 years (interquartile range: 68, 74), 492 (14%) patients experienced PPCs within the first 7 postoperative days. Elevated FiO2 was associated with an increased risk of PPCs in all logistic regression models. The OR of FiO2 > 60% group was 1.252 (95%CI 1.015–1.551, P = 0.038) in the univariate analysis. The ORs for the FiO2 > 60% group were 1.259 (model 2), 1.314 (model 3) and 1.32 (model 4) in the multivariate logistic regression models. While a balanced covariate distribution between the two groups were created after using PSM or IPTW, the correlation between an elevated FiO2 and an increased risk of PPCs remained significantly, PSM analysis (OR: 1.393; 95% CI:1.077–1.804, P = 0.012), and IPTW analysis (OR: 1.266; 95% CI: 1.086–1.476; P = 0.003). Conclusions High intraoperative FiO2 (> 60%) was associated with the postoperative occurrence of pulmonary complication independently of predefined risk factors in elderly non-cardiothoracic surgery patients. The application of high intraoperative FiO2 should be cautious in surgical patients vulnerable to PPCs.