Effects of supplemental oxygen therapy in patients with suspected acute myocardial infarction: a meta-analysis of randomised clinical trials

Background: Although oxygen therapy has been used for over a century in the management of patients with suspected acute myocardial infarction (AMI), recent studies have raised concerns around the efficacy and safety of supplemental oxygen in normoxaemic patients.

Objective: To synthesise the evidence from randomised controlled trials (RCTs) that investigated the effects of supplemental oxygen therapy compared with room air in patients with suspected or confirmed AMI.

Methods: For this aggregate data meta-analysis, multiple databases were searched from inception to 30 September 2017. RCTs with any length of follow-up and any outcome measure were included if they studied the use of supplemental O₂ therapy administered by any device at normal pressure compared with room air. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, an investigator assessed all the included studies and extracted the data. Outcomes of interests included mortality, troponin levels, infarct size, pain and hypoxaemia.

Results: Eight RCTs with a total of 7998 participants (3982 and 4002 patients in O₂ and air groups, respectively) were identified and pooled. In-hospital and 30-day death occurred in 135 and 149 patients, respectively. Oxygen therapy did not reduce the risk of in-hospital (OR, 1.11 (95% CI 0.69 to 1.77)) or 30-day mortality (OR, 1.09 (95% CI 0.80 to 1.50)) in patients with suspected AMI, and the results remained similar in the subgroup of patients with confirmed AMI. The infarct size (based on cardiac MRI) in a subgroup of patients was not different between groups with and without O₂ therapy. O₂ therapy reduced the risk of hypoxaemia (OR, 0.29 (95% CI 0.17 to 0.47)).

Conclusion: Although supplemental O₂ therapy is commonly used, it was not associated with important clinical benefits. These findings from eight RCTs support departing from the usual practice of administering oxygen in normoxaemic patients.