Authors' objectives: Perioperative oxygen administration has been proposed as a strategy to reduce postoperative complications. However, uncertainty exists as to which strategies are the most clinically effective. To provide an overview on the effectiveness of perioperative oxygen therapy and formulate recommendations to inform clinical decision-making and research. More than 5 million patients undergo surgery in the UK in a typical year and are routinely given supplemental oxygen. Perioperative supplemental oxygen can prevent and treat hypoxaemia and potentially reduce complications, such as surgical site infections (SSIs), pulmonary complications and mortality. Although supplemental oxygen is routinely administered to almost all patients during surgery, the best practice for intraoperative oxygen administration and the effect of different levels of inspired oxygen [fraction of inspired oxygen (FiO2)] on postoperative clinical outcomes remains unknown. The World Health Organization (WHO) currently recommends that adults undergoing general anaesthesia for surgical procedures should receive high-concentration oxygen (80%) intraoperatively and postoperatively for 2–6 hours. This recommendation has been widely criticised for not considering thoroughly the potential adverse effects of a high perioperative FiO2. Hyperoxaemia has been shown to be harmful in certain conditions, such as myocardial infarction and acute respiratory distress syndrome (ARDS). Although the injurious mechanisms have not been fully elucidated, there is emerging consensus that normoxaemia should be the target for critically unwell patients. This is also reflected in clinical guidelines, which do not recommend supplemental oxygen in the absence of hypoxia. WHO’s recommendations in 2016 also appear to contradict consensus in other clinical contexts, such as emergency department or intensive care unit (ICU) where a high FiO2 is not recommended. The World Federation of Societies of Anaesthesiologists recommends 30–40% FiO2 for intubated patients. The dissonance between oxygen guidelines and evidence from clinical studies is reflected in prescribing practices among UK anaesthetists. A recent multicentre retrospective observational study conducted across 29 UK hospitals demonstrated that intraoperative oxygen administration by anaesthetists varied widely from 25% to 100% FiO2, with no obvious down-titration of oxygen in response to sustained supranormal blood oxygen levels. An intraoperative FiO2 of 50% currently represents standard intraoperative practice in the UK, with surgical patients often experiencing moderate levels of hyperoxaemia. This differs from both WHO’s recommendation of using 80% FiO2 intraoperatively, and the value most previous interventional oxygen therapy trials have used to represent standard care (typically 30% FiO2). This uncertainty has led to a lack of standardised approach in perioperative oxygen therapy, marked variability and potential unintended harm in the care of patients undergoing surgery. Adding to this uncertainty is the lack of clear guidance on the use of different oxygen delivery devices postoperatively and during surgery where patients are not intubated. Several systematic reviews have explored the use of different oxygen strategies in the perioperative setting. However, these reviews overlap to various degrees in their evidence coverage of different phases and timepoints in the surgical pathway, oxygenation strategies, oxygen delivery devices and clinical conditions, and reported varied findings and conclusions which may be partly attributable to their different scopes and the clinical and methodological diversity of underlying evidence. To address the uncertainty in evidence and practice, an overview of systematic reviews and meta-analyses was needed to map, appraise and synthesise the evidence from systematic reviews on the clinical effectiveness of different types of perioperative oxygen therapy strategies across all patient groups and surgical settings. Bringing together the available evidence in this overview of reviews will aid clinical decision-making and highlight the specific areas in which further high-quality research is required. This overview was designed and undertaken in response to a commissioned call by the UK National Institute for Health and Care Research (NIHR) Health Technology Assessment (HTA) Programme. The overview aimed to provide a comprehensive summary of available evidence on the effectiveness of perioperative oxygen therapy and formulate recommendations to inform clinical decision-making and future research.

Authors' results and conclusions: We identified 59 systematic reviews and selected 5 anchoring reviews. A high fraction of inspired oxygen may result in a slight reduction in surgical site infection compared with a low fraction of inspired oxygen (risk ratio 0.91, 95% confidence interval 0.78 to 1.05; risk difference 1.2% lower, 2.9% lower to 0.7% higher, low-certainty evidence). This effect may be modified by type of surgery, oxygen delivery method or study quality. The evidence suggests that a high fraction of inspired oxygen results in a large increase in the incidence of atelectasis (risk ratio 1.47, 95% confidence interval 1.20 to 1.79; risk difference 6.5% higher, 2.8% higher to 10.9% higher, low-certainty evidence) and may increase postoperative pulmonary complications slightly (risk ratio 1.06, 0.77 to 1.46; risk difference 1.1% higher, 4.1% lower to 8.2% higher) but the evidence is very uncertain. A high fraction of inspired oxygen may result in little to no difference in mortality, nausea and vomiting, and length of hospital stay. Postoperative high-flow nasal oxygen may reduce the need to escalate respiratory support compared with conventional oxygen therapy (risk ratio 0.61, 0.41 to 0.91; risk difference 7.8% lower, 11.7% lower to 1.8% lower) but the evidence is very uncertain. High-flow nasal oxygen may result in little to no difference in mortality and reintubation rate. Compared with conventional oxygen therapy, postoperative non-invasive ventilation may decrease postoperative pulmonary complications (risk ratio 0.62, 0.44 to 0.87; risk difference 12.2% lower, 18% lower to 4.2% lower) and probably results in a slight reduction in the incidence of acute respiratory distress syndrome (risk ratio 0.70, 0.53 to 0.93; risk difference 1.2% lower, 1.9% lower to 0.3% lower). Non-invasive ventilation results in little to no difference in mortality, pneumonia or reintubation rate. Grading of recommendations assessment, development and evaluation certainty in evidence was low for most outcomes. Trial sequential analysis revealed further studies are required to provide conclusive evidence on the effectiveness of perioperative oxygen therapy. There is no clear evidence that either a high or a low fraction of inspired oxygen improves outcomes in surgical patients. Existing evidence is insufficient for recommending routine use of non-invasive ventilation or high-flow nasal oxygen. Search results and mapping of included reviews and RCTs Searches for systematic reviews identified 4072 results after deduplication. Following abstract and full-text screening, 59 reviews were selected. Following mapping of included reviews, we selected five anchoring reviews that provided the most comprehensive and up-to-date evidence on the effectiveness of perioperative oxygen therapy. Searches for additional RCTs identified 3279 records after deduplication. Following abstract screening 120 texts were retrieved. Thirteen new RCTs that fulfilled the inclusion criteria of the relevant anchoring reviews were selected and included in the updated meta-analyses that we carried out. There is no clear evidence that either high or low FiO2 improves outcomes in surgical patients. High perioperative FiO2 increases atelectasis and may result in a slight reduction in SSI, but the characteristics of the patients and surgeries for which the potential effect could be realised remain to be elucidated. Existing evidence suggests potential benefits of postoperative use of HFNO or NIV in reducing PPCs, but the evidence is insufficient for recommending their routine use and requires validation by large confirmatory trials.

Authors' methods: We followed the Preferred Reporting Items for Overviews of Reviews guidelines. We searched key databases for systematic reviews (from inception to September 2021) and randomised controlled trials (from April 2018 to March 2022) comparing perioperative oxygen strategies. Reviews with the most comprehensive coverage of literature were chosen as anchoring reviews. We assessed risk of bias for each anchoring review using the Risk of Bias in Systematic Reviews tool. We updated meta-analyses from anchoring reviews with data from recent randomised controlled trials and conducted subgroup analyses and meta-regression. We assessed the certainty of evidence using grading of recommendations assessment, development and evaluation framework and conducted trial sequential analysis. We used grading of recommendations assessment, development and evaluation informative statements to communicate our findings. Our advisory panel reviewed mapping of studies and interpretation of evidence. Patient, public and professional involvement We worked with our advisory panel consisting of patients and a multidisciplinary group (doctors, nurses, advanced practitioners, physiotherapy) with expertise across the clinical areas of anaesthesia, respiratory medicine, critical care, and surgery. Experts reviewed mapping of studies, synthesis strategy and interpretation of evidence to guide the production of clinically relevant recommendations and review conclusions. In addition, a patient representative (MT) worked closely with the research team throughout the project, including drafting of the study proposal, review protocol and interpretation of results. We followed the Preferred Reporting Items for Overviews of Reviews (PRIOR) guidelines. We searched MEDLINE (via Ovid), Embase (Ovid), the Cochrane Database of Systematic Reviews (Wiley), Epistemonikos, PROSPERO [Centre for Reviews and Dissemination (CRD), University of York), the International Network of Agencies for Health Technology Assessment International Health Technology Assessment Database, and the Database of Abstracts of Reviews of Effects archives (via CRD) and ECRI Guidelines Trust databases for systematic reviews comparing perioperative oxygen strategies. These databases were searched from inception to September 2021. We also searched for recently published or ongoing/planned randomised controlled trials (RCTs) in the Cochrane Central Register of Controlled Trials database. This search was undertaken in March 2022 and limited to records added in 2018 or later.

Project Status: Completed

URL for project: https://www.journalslibrary.nihr.ac.uk/programmes/hta/NIHR132987

Year Published: 2025

URL for published report: https://www.journalslibrary.nihr.ac.uk/hta/TNTC4360

URL for additional information: English

English language abstract: An English language summary is available

Publication Type: Full HTA

Country: England, United Kingdom

DOI: 10.3310/TNTC4360

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk