Second Opinion

Treating acutely ill patients with too much oxygen can be life threatening, Canadian study finds

Oxygen is given to millions of patients around the world every day, but too much of it can be harmful and life-threatening, according to a new Canadian scientific paper that in one expert's view "is a very significant landmark study."

One cardiologist says the research will change how he administers oxygen in his own coronary care unit

McMaster University's Derek Chu, left, and Waleed Alhazzani tested the widely held belief that traditional oxygen therapy is harmless. Their study found for every 71 patients treated with excessive oxygen, an additional death occurs in hospital.

This is an excerpt from Second Opinion, a weekly roundup of eclectic and under-the-radar health and medical science news emailed to subscribers every Saturday morning. 

If you haven't subscribed yet, you can do that by clicking here.


Oxygen is given to millions of patients around the world every day, but too much of it can be harmful and life-threatening, according to a new Canadian scientific paper that in one expert's view "is a very significant landmark study."

McMaster University researchers were interested in testing the widely held belief that traditional oxygen therapy is harmless.

Their study, published this week in The Lancet medical journal, shows supplemental oxygen, when given liberally to acutely ill patients, increases the risk of death in people with sepsis, stroke, cardiac arrest, as well as those with trauma or requiring emergency surgery.

In their meta-analysis, the researchers systematically reviewed 25 randomized controlled trials of more than 16,000 adult patients that compared the use of liberal (supplemental oxygen) and conservative oxygen (room air) therapies. They concluded that for every 71 patients treated with excessive oxygen, an additional death occurs in hospital.

"What this is suggesting is that we need to move away from being too liberal with oxygen," said the study's lead author Dr. Derek Chu, who is a clinical fellow at McMaster University. "Maybe we need to be a bit more modest, frequently recheck if we can decrease how much oxygen a patient is requiring. And that's a simple intervention that could save a number of lives."

The study also found that supplemental use of oxygen:

  • Didn't decrease any infections.
  • Didn't improve a patient's length of hospital stay.
  • Didn't improve the level of disability for stroke patients or those with brain injuries.

The researchers say the results have immediate and important implications for health-care providers, policy-makers and researchers.

The study's findings challenge the widely held belief that giving patients oxygen therapy is harmless. (Shutterstock)

"We need clear guidelines and updated guidelines on how to use oxygen and when to use oxygen," Chu told CBC News. "There's no clear consensus in North America or around the world on how to use oxygen.

"I think we need to be a bit more uniform and have updated guidelines with this evidence included to change practice and improve patient lives."

'A practice-changing study'

Cardiologist John William McEvoy believes the results will likely lead to a reconsideration of guideline recommendations around supplemental oxygen.

McEvoy — an assistant professor at Johns Hopkins University's medical school, who wrote a commentary about the study for The Lancet — said the new research will change how he administers oxygen in his own coronary care unit.

"This is definitely a practice-changing study," he told CBC News. "I read very many papers and meta-analyses and this is one of the few that I think truly should change how we think about oxygen. And in my view it is a very significant landmark study."

Oxygen is often administered because it's widely believed to be safe and not considered a harmful substance, he said. The most common reasons to give extra oxygen is for patients who are short of breath, who have lung conditions or who are oxygen deficient, he said.

McEvoy said in his own practice, "it's just common practice —  traditional practice — that we give them some excess oxygen because they're in the ICU, they're intubated and we don't think it's harmful. But these data would suggest that we ought to be getting them on room air even if they're still intubated and that's a big change."    


To read the entire Second Opinion newsletter every Saturday morning, subscribe by clicking here.