A systematic review of the effectiveness of oxygen in reducing acute myocardial ischaemia

Patients with acute cardiac chest pain receive oxygen as part of their treatment. Oxygen is given in the belief it will help to correct the oxygen demand - supply imbalance of acute myocardial ischaemia.

The aim was to review the evidence base for the use of oxygen to treat acute myocardial ischaemia and the objective was to include all evidence of sufficient quality.

A systematic review was carried out to provide a thorough, transparent and replicable review process.

The review included randomized and non-randomized clinical trials; patients with acute coronary syndrome (unstable angina or acute myocardial infarction); and any outcome measurements of myocardial ischaemia.

Nine trials were found, of which two were randomized controlled trials and seven non-randomized clinical trials. There were quality assessment concerns over the methodology, size and analysis within the trials. The effectiveness of oxygen in reducing myocardial ischaemia was unclear from the review, as the trials contained data that suggested oxygen reduced myocardial ischaemia, but also data that suggested it increased myocardial ischaemia.

No definite conclusions could be drawn as to whether oxygen reduced, increased or had no effect on acute myocardial ischaemia. The papers were divided as to recommending oxygen use for all patients with acute myocardial ischaemia or not - although all agreed that patients with systemic hypoxaemia should have this corrected by oxygen administration. The key finding of the review was that there was insufficient evidence.

As oxygen is routinely administered to treat acute myocardial ischaemia, the lack of a clear supporting evidence base must be a source of concern. This is especially so as some of the evidence suggested oxygen may increase myocardial ischaemia. There is a need for experimental-design clinical research to test the effectiveness of oxygen in reducing myocardial ischaemia.