One of the standard treatments for heart attack patients is oxygen. It is so routine, in fact, that it is rarely questioned. However, new research suggests it may be doing more harm than good.
Blood does many important things in the body, but the most urgent is to distribute oxygen. So when the heart stops beating properly, it is an intuitive step to increase the intake of oxygen to the lungs. If there is more oxygen in the system, the chances of some getting through seem higher.
Ambulance Victoria paramedic Ziad Nehme says doctors thought that if oxygen reached the damaged heart tissue quickly, it would reduce the scale of future attacks. "Most people were taught, as they were going through their medical training, that oxygen would do some people a lot of good, but for everybody it would do no harm,” Nehme told the ABC.
However, concerns were raised in 2011 and an international group of researchers and clinicians decided a scientific study was needed. Using MRI machines six months after the attack, they examined 441 patients who had suffered myocardial infarctions, but had not suffered lack of oxygen (hypoxia). Half of those examined had been treated with oxygen. They not only found no benefit but also an increased rate of heart attacks among those given oxygen and almost 50% larger areas of damaged heart tissue.
"Oxygen narrows coronary arteries and reduces the blood flow to the heart and may accelerate the amount of inflammation and stress caused to heart tissue," said Nehme, one of the study's authors. However, it is not yet clear if this is the explanation for the observed effect.
Further research will examine if there is a difference in life expectancy between those who are given oxygen and those who are not.
The work was presented at the conference of the American Heart Association.