A heart attack is caused by blockage of one of the arteries that supplies oxygen to the heart muscle. When this happens some of the heart muscle dies quickly and, as with stroke, this area of necrosis is surrounded by a penumbra where the heart muscle cells are damaged but not dead. Oxygen administered through a face-mask results in an increase in the amount of oxygen dissolved in the blood. Surely then, oxygen makes sense in people who are having a heart attack? Such therapy has been standard since my days as a medical student.
Well, it turns out that while oxygen therapy does no harm in heart attack victims, it also does no good whatsoever. This is the result of a randomised trial of over 6600 patients. Death rates, a test for heart cell damage, and re-hospitalisation rates were almost identical across the two groups. The null result was consistent across all pre-specified subgroups of patients.
A picture is starting to emerge: oxygen therapy does not limit tissue loss in patients with acute ischemic injury.
It is quite difficult to improve on the bodies evolutionary adaptations to injury as the following report will further reinforce.
— Richard Lilford, CLAHRC WM Director
- Hoffman R, James SK, Jernberg T, et al. Oxygen Therapy in Suspected Acute Myocardial Infarction. New Engl J Med. 2017; 337: 1240-9.