High intraoperative inspiratory oxygen fraction and risk of major respiratory complications

Background High inspiratory oxygen fraction ( F I O 2 ) may improve tissue oxygenation but also impair pulmonary function. We aimed to assess whether the use of high intraoperative F I O 2 increases the risk of major respiratory complications. Methods We studied patients undergoing non-cardiothoracic surgery involving mechanical ventilation in this hospital-based registry study. The cases were divided into five groups based on the median F I O 2 between intubation and extubation. The primary outcome was a composite of major respiratory complications (re-intubation, respiratory failure, pulmonary oedema, and pneumonia) developed within 7 days after surgery. Secondary outcomes included 30-day mortality. Several predefined covariates were included in a multivariate logistic regression model. Results The primary analysis included 73 922 cases, of whom 3035 (4.1%) developed a major respiratory complication within 7 days of surgery. For patients in the high- and low-oxygen groups, the median F I O 2 was 0.79 [range 0.64–1.00] and 0.31 [0.16–0.34], respectively. Multivariate logistic regression analysis revealed that the median F I O 2 was associated in a dose-dependent manner with increased risk of respiratory complications (adjusted odds ratio for high vs low F I O 2 1.99, 95% confidence interval [1.72–2.31], P -value for trend