Supplemental oxygen provides no beneficial effect on 1-year mortality
Routine use of supplemental oxygen does not appear to cut 1-year all-cause mortality in patients with suspected myocardial infarction (MI) but who do not have hypoxaemia, a study has shown.
A total of 6,629 patients with suspected MI and an oxygen saturation of ≥90 percent were randomized to receive either supplemental oxygen (6 litres/minute for 6 to 12 hours, delivered through an open face mask) or ambient air.
The primary outcome was death from any cause within 365 days after randomization. Secondary endpoints included death from any cause within 30 days after randomization, rehospitalization with MI, rehospitalization with heart failure, cardiovascular death, as well as composites of these endpoints, assessed at 30 and 365 days.
Median duration of oxygen therapy was 11.6 hours. At the end of the treatment period, median oxygen saturation was 99 percent in the oxygen therapy arm vs 97 percent in the ambient air arm (p<0.001). Hypoxaemia occurred with greater frequency among patients given ambient air than among those who received supplemental oxygen (62 vs 254 patients; p<0.001). The median of the highest troponin level observed during hospitalization was 946.5 ng/litre in the oxygen arm vs 983.0 ng/litre in the ambient-air arm.
In Cox proportional hazards model, the primary outcome of death from any cause within 1 year of randomization did not significantly differ between the oxygen and ambient-air arms (5.0 vs 5.1 percent, respectively; hazard ratio [HR], 0.97; 95 percent CI, 0.79 to 1.21; p=0.80).
Likewise, the number of patients who were rehospitalized for MI within 1 year was similar between the two treatment arms (3.8 vs 3.3 percent; HR, 1.13; 0.88 to 1.46; P=0.33). The results were consistent across all predefined subgroups, including infarction type, sex, age, smoking status and presence of diabetes, among others.