Is oxygen therapy for myocardial infarction beneficial

The notion that increased oxygen delivery limits ischemic damage to the myocardium during myocardial infarction seems, on the face of it, highly plausible. Perhaps not surprising, then, that for the best part of a century administration of oxygen has been a routine component of medical care for many patients suffering myocardial infarction (MI). 

However, the evidence base for the beneficial effect of this time-honored therapeutic ritual is practically non-existent according to the authors of a recently published systematic review of the literature. More serious than the lack of evidence for benefit is the evidence highlighted by this study that oxygen therapy might actually be harmful in the context of MI. 

A systematic review of the literature revealed only two randomized clinical trials of oxygen therapy in myocardial infarction, involving a combined total of just 207 MI patients. The first of these, conducted in 1976, randomized 157 MI patients to receive either oxygen or compressed air. 

Results revealed that oxygen therapy was associated with a non-significant increased risk of death (risk ratio 2.9 %, CI 0.8-10.3, p = 0.08) and a significantly greater infarct size as measured by cardiac enzyme levels in blood. The only other relevant study involving just 43 MI patients provided no evidence for benefit or harm associated with oxygen therapy. 

Overall, the authors of this meta-analysis conclude that there is insufficient evidence to support the use of oxygen therapy in the treatment of uncomplicated MI, and the balance of the limited evidence available suggests that "the routine use of high-flow oxygen in uncomplicated MI may result in greater infarct size and possible increased risk of mortality".