Most guidelines for the treatment of people who are having a heart attack recommend that the patient should be given oxygen to breathe. We looked for the evidence to support this practice by searching for randomised controlled trials that compared the outcomes in patients given oxygen to the outcomes for patients given normal air to breathe. We were primarily interested in seeing whether there was a difference in the number of people who died but we also looked at whether administering oxygen reduced pain.
We found three randomised controlled trials that compared one group given oxygen to another group given air. These trials involved a total of 387 patients of whom 14 died. Of those who died, nearly three times as many people known to have been given oxygen died compared to those known to have been given air. However, because the trials had few participants and few deaths this result does not necessarily mean that giving oxygen increases the risk of death. The difference in numbers may have occurred simply by chance. Nonetheless, since the evidence suggests that oxygen may in fact be harmful, we think it is important to evaluate this widely used treatment in a large trial, as soon as possible, to make sure that current practice is not causing harm to people who have had a heart attack.