Supplemental Oxygen and Acute Myocardial Infarction　- A Systematic Review and Meta-Analysis

In Japan, oxygen is commonly administered during the acute phase of myocardial infarction (MI) to patients without oxygen saturation monitoring. In this study we assessed the effects of supplemental oxygen therapy, compared with ambient air, on mortality and cardiac events by synthesizing evidence from randomized controlled trials (RCTs) of patients with suspected or confirmed acute MI. PubMed was systematically searched for full-text RCTs published in English before June 21, 2020. Two reviewers independently screened the search results and appraised the risk of bias. The estimates for each outcome were pooled using a random-effects model. In all, 2,086 studies retrieved from PubMed were screened. Finally, 7,322 patients from 9 studies derived from 4 RCTs were analyzed. In-hospital mortality in the oxygen and ambient air groups was 1.8% and 1.6%, respectively (risk ratio [RR] 0.90; 95% confidence interval [CI] 0.38-2.10]); 0.8% and 0.5% of patients, respectively, experienced recurrent MI (RR 0.44; 95% CI 0.12-1.54), 1.5% and 1.6% of patients, respectively, experienced cardiac shock (RR 1.10; 95% CI 0.77-1.59]), and 2.4% and 2.0% of patients, respectively, experienced cardiac arrest (RR 0.91; 95% CI 0.43-1.94). Routine supplemental oxygen administration may not be beneficial or harmful, and high-flow oxygen may be unnecessary in normoxic patients in the acute phase of MI.