High intra-operative fraction of inspired oxygen (FIO2) has been proposed to increase the tissue O2 tension during surgery with the aim to reduce surgical-wound infection.

However, an FIO2 of 0.60 to 0.90 does not reduce the relative risk (RR) of surgical site infection [RR 0.86 (95% confidence interval (CI) 0.63 to 1.1)] and all-cause mortality [RR 1.12 (95% CI 0.93 to 1.36)] more than an FIO2 of 0.40 or less.

Trial sequential analysis estimates a required study size of 10 736 patients to detect a risk increase of 20% in all-cause mortality The cumulative Z-curve does not reach the conventional boundary for significance and monitoring boundary for harm/benefit suggesting insufficient evidence with high FIO2.