Prehospital Oxygen Titration Strategies in Acute Myocardial Infarction: A Systematic Review of Mortality and Reinfarction

Abstract

Background: Supplemental oxygen is commonly used during prehospital care for acute myocardial infarction (AMI), but routine oxygen may offer no benefit to normoxemic patients and could cause harm through hyperoxia.

Objective: To evaluate whether prehospital oxygen titration, compared with routine oxygen, affects mortality and reinfarction in adults with suspected or confirmed AMI.

Methods: Following PRISMA 2020, MEDLINE, Embase, CENTRAL, CINAHL, and Web of Science were searched without date limits. Randomised and non-randomised intervention studies of adults receiving prehospital care for AMI were eligible. The primary outcomes were all-cause mortality and reinfarction. Risk ratios (RRs) with 95% confidence intervals (CIs) were pooled; evidence certainty was assessed using GRADE.

Results: Twelve studies were included: four randomised trials and eight non-randomised studies. Titrated or conservative oxygen was not associated with a detectable difference in all-cause mortality compared with routine oxygen (RR 0.99, 95% CI 0.81–1.21; I² = 0%; moderate-certainty evidence). Reinfarction showed a non-significant trend toward greater risk with routine oxygen (RR 1.19, 95% CI 0.95–1.48; I² = 0%; low-certainty evidence). Findings were consistent in sensitivity analyses. Evidence on harms was limited by inconsistent reporting.

Conclusion: Available evidence does not show a mortality benefit from routine oxygen in predominantly normoxemic patients with AMI. Prehospital care should use oxygen selectively for hypoxemia and titrate it to avoid both inadequate oxygenation and hyperoxia. The evidence remains limited, particularly for reinfarction and patients with baseline SpO₂ of 90–94%; adequately powered prehospital trials are needed.