The use of supplemental oxygen does not improve outcomes in patients with myocardial infarction without hypoxaemia, according to results of the registry-based DETO2X-SWEDEHEART trial. A total of 6,629 patients with suspected myocardial infarction and oxygen saturation ≥90% were randomly allocated to supplemental oxygen (6 l/min for 6–12 h, delivered through an open face mask) or ambient air. Hypoxaemia developed in 1.9% of the oxygen group compared with 7.7% of the ambient-air group. No significant differences were observed in the 1-year rate of all-cause death (5.0% vs 5.1%) or rehospitalization with myocardial infarction (3.8% vs 3.3%). “Supplemental oxygen provides no benefit to patients with acute coronary syndromes who do not have hypoxaemia,” summarizes Joseph Loscalzo in an editorial. “It is clearly time for clinical practice to change to reflect this definitive evidence.”