A low perioperative fraction of inspired oxygen reduces the incidence of postoperative atelectasis in patients undergoing abdominal surgery under general anesthesia: A systematic review and meta-analysis.

ObjectiveTo determine the relative risk of atelectasis after abdominal surgery associated with perioperative fraction of inspired oxygen.MethodsOur meta-analysis was registered with the International Prospective Register of Systematic Reviews (PROSPERO; registration number: CRD 42021270703). The PubMed, Cochrane Library, EMBASE, and Web of Science databases were searched for randomized controlled trials reporting the influence of perioperative fraction of inspired oxygen on the incidence of postoperative atelectasis in patients who had undergone abdominal surgery under general anesthesia. We used a random-effect model to calculate the relative risk of postoperative atelectasis. Subgroup analyses were performed according to age, ventilation strategy, surgical incision site, and surgery duration.ResultsFinally, we included 10 randomized controlled trials involving 3471 participants. Compared with the high fraction of inspired oxygen group (60%-100%), a reduced atelectasis incidence after abdominal surgery was observed in the low fraction of inspired oxygen group (20%-40%). Patients with an average age ≥60 years benefited more from a low fraction of inspired oxygen in terms of prevention of postoperative atelectasis compared with those with an average age <60 years (risk ratio: 1.47; 95% confidence interval: 1.14-1.90). Patients undergoing lower abdominal surgery benefited from a low perioperative fraction of inspired oxygen (risk ratio: 1.43; 95% confidence interval: 1.14-1.80).ConclusionsA low perioperative fraction of inspired oxygen may decrease the risk of atelectasis after lower abdominal surgery performed under general anesthesia, especially in patients with an average age <60 years.