A ground-breaking study by New Zealand researchers has found that administering too much oxygen can kill seriously ill patients.
It's long been thought that administering oxygen can't harm these patients and the researchers say their findings could save thousands of lives around the world.
The New Zealand study, published in the prestigious Lancet medical journal shows administering excessive oxygen increases the risk of death for seriously ill patients by 21 per cent, amounting to around one extra death for every 71 patients.
"There are millions of people around the world who receive oxygen for acute illness every day. So that gives you an idea of the potential global health importance of the study findings," said Paul Young, researcher.
He, along with Canadian researchers, analysed the results of oxygen therapy for more than 16,000 patients.
In New Zealand and around the world, patients are generally given oxygen if levels drop below 90 per cent.
Intensive care specialist Colin McArthur says they knew they needed to give enough oxygen to keep the levels at a point that was considered safe, "but we didn't pay much attention to how high they went".
But the findings suggest a slightly lower oxygen level could be better for the patient than being topped up with too much.
"Human beings have adapted to breathe 21 per cent oxygen in the air around us. Anything more than that represents a physiological stress," Paul Young said.
Oxygen can be a lifesaver in many cases, but exactly what level of oxygen is dangerous is not yet known and more research is underway.
But these findings alone will change international guidelines, says Richard Beasley of the New Zealand Medical Research Institute.
"The strength of evidence is now strong enough that this will now mandate changes in clinical practice not only in New Zealand but also around the world," he said.
A study looking at 1,000 intensive care patients in New Zealand and Australia is being completed, with results expected early next year.