There is no evidence that the common practice of giving patients oxygen to inhale during a heart attack is beneficial, according to a new Cochrane Systematic Review. Until further research is carried out, the researchers say the possibility that giving oxygen may actually increase a patient's risk of dying cannot be ruled out.
Globally, more than 30 million people have heart attacks every year, according to the World Health Organisation. Heart attacks occur when the flow of oxygenated blood to the heart is interrupted. Heart attack patients are often given oxygen to try to improve oxygenation of the heart tissue. However, there is little evidence that this intervention improves outcomes for heart patients and some evidence even suggests it may cause further damage.
The researchers included data from three trials in their studies. Patients were either given pure oxygen or air to inhale in the 24 hours following the onset of heart attack symptoms. Of the 387 patients involved in the studies only 14 died, but of these, almost three times as many had inhaled oxygen as opposed to air.
Although the results appear to suggest giving oxygen could do more harm than good, the researchers say there is not yet enough data to be certain. "This result does not necessarily mean that giving oxygen increases the risk of dying from a heart attack," said Dr Amanda Burls of the Department of Primary Health Care at the University of Oxford in Oxford, UK. "The numbers are so small that this may just have been due to chance."
However, said Prof Tom Quinn, another of the researchers based at the Faculty of Health and Medical Sciences at the University of Surrey in Guildford, UK, it is important to resolve the uncertainty. "Given the fact that this is such a widely used treatment, we think it is important that a large trial is conducted as soon as possible to make sure that giving oxygen is not causing any harm."
Another member of the team, Dr. Juan Cabello of the Alicante General University Hospital in Alicante, Spain, added, "It is truly amazing how we, as cardiologists, have been employing this treatment without solid evidence."
Cabello JB, Burls A, Emparanza JI, Bayliss S, Quinn T. Oxygen therapy for acute myocardial infarction. Cochrane Database of Systematic Reviews 2010, Issue 6. Art. No.: CD007160. DOI: 10.1002/14651858.CD007160.pub2