Suspected MI: No Difference Between Supplemental Oxygen and Ambient Air Treatment

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Supplemental oxygen therapy for suspected MI did not reduce the risk for rehospitalization at 1 year.
Supplemental oxygen therapy for suspected MI did not reduce the risk for rehospitalization at 1 year.

Among patients with suspected myocardial infarction (MI), supplemental oxygen therapy does not decrease the risk for 1-year all-cause mortality, according to results from a registry-based randomized trial published in the New England Journal of Medicine and presented at the 2017 European Society of Cardiology Congress held August 26-30 in Barcelona, Spain.1,2

In DETO2X-AMI (An Efficacy and Outcome Study of Supplemental Oxygen Treatment in Patients With Suspected Myocardial Infarction; Clinicaltrials.gov identifier: NCT01787110), patients with a suspected MI and an oxygen saturation level of 90% or higher were randomly assigned to receive either supplemental oxygen or ambient air. Supplemental oxygen was administered through an open face mask for 6 to 12 hours at a rate of 6 L/min.

In the per-protocol analysis, patients were randomly assigned to either ambient air (n=3212) or to oxygen therapy (n=3014).  Mortality follow-up data from this trial were obtained from the Swedish National Population Registry.

Oxygen therapy was administered on site immediately following randomization. In the intention-to-treat population, the primary end point was all-cause mortality 1 year after randomization. At 1 year, no difference was found at 1 year between the rates of all-cause mortality in the oxygen therapy group and the ambient air group  (5.0% vs 5.1%, respectively; hazard ratio [HR], 0.97; 95% CI, 0.79-1.21; P =.80).

In addition, no significant difference was found between the rate of hospital readmission for MI in the oxygen therapy group and the ambient air group (3.8% vs. 3.3%, respectively; HR, 1.13; 95% CI, 0.88-1.46; P =.33). However, the incidence of hypoxemia during the trial was lower in the supplemental oxygen group than in the ambient air group (1.9% vs 7.7%, respectively; P <.001).

A potential limitation of this study was its open-label design; the researchers noted that a double-blind design would have been neither ethical nor feasible because “the available closed Hudson masks might have put patients at risk for carbon dioxide retention if they had been used as a sham comparator.”

There is no beneficial effect of oxygen therapy compared with ambient air in patients who have suspected MI, particularly as these therapies relate to the rates of all-cause mortality and rehospitalization at 1 year, the investigators concluded.

References

  1. Hofmann R, James SK, Jernberg T, et al. Oxygen therapy in suspected acute myocardial infarction. European Society of Cardiology Congress 2017; August 26-30, 2017; Barcelona, Spain.
  2. Hofmann R, James SK, Jernberg T, et al; for the DETO2X-SWEDEHEART Investigators. Oxygen therapy in suspected acute myocardial infarction [published online August 28, 2017]. N Engl J Med. doi:10.1056/NEJMoa1706222
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