Background: Clinical guidelines recommend supplemental oxygen in patients with suspected acute myocardial infarction but data to support its use in patients without hypoxemia are limited.
Study design: Open-label, registry based randomized clinical trial.
Setting: Thirty-five hospitals in Sweden with acute cardiac care facilities.
Synopsis: Authors included 6,629 patients aged 30 and older who presented with symptoms suggestive of myocardial infarction. Patients with oxygen saturations 90% or greater were enrolled in the study and randomly assigned to either 6 liters per minute of face mask oxygen for 6-12 hours or ambient air. Median oxygen saturation was 99% in the treatment group and 97% in the ambient air group (P less than .0001). In an intention-to-treat model, 1 year after randomization there was no significant difference in all-cause mortality between the oxygen (5.0%) and ambient air (5.1%) groups (P = .80). There was no difference in the rate of rehospitalization with myocardial infarction or the composite endpoint of all-cause mortality and rehospitalizations for myocardial infarction at 30 days and 1 year. Limitations of this study include lower power than anticipated since calculations were based on a higher mortality rate than observed in this study, and the open-label protocol.
Bottom line: In patients who present with a suspected myocardial infarction without hypoxemia, oxygen therapy is not associated with improved all-cause mortality or decreased rehospitalizations for myocardial infarction.
Citation: Hofmann R, Jernberg T, Erlinge D, et al. Oxygen therapy in suspected acute myocardial infarction. N Engl J Med. 2017;377:1240-9.
Dr. Gala is a hospitalist, Beth Israel Deaconess Medical Center, and instructor in medicine, Harvard Medical School, Boston.