Ground-breaking Study: Too Much Oxygen Risks Patient Death

Ground-breaking Study Shows Too Much Oxygen Risks Patient Death

Oxygen … it’s routinely given to support acutely sick patients around the world every day. But a new study, co-authored by a New Zealand doctor and researcher, now shows that too much of it increases the risk of death for acutely unwell patients.

The study, published in the world’s most prestigious medical journal, The Lancet, found that compared to a conservative oxygen strategy, liberal administration of oxygen increased the risk of in-hospital patient death by 21%; an estimated 1 additional death for every 71 patients. What’s more, a further finding suggests that the more supplemental oxygen patients are given, the higher the risk of death.

Study co-author Dr Paul Young, a Wellington Hospital Intensive Care specialist and researcher at the Medical Research Institute of New Zealand (MRINZ), says the ground-breaking findings prove, for the first time, that there is such a thing as too much oxygen for acutely ill adults.

“Our findings are distinct from the pervasive view that liberal oxygen therapy for acute illnesses is at worst, harmless” says Dr Young. “They in fact show that administering too much oxygen is potentially harmful, even deadly”.

Dr Young and his co-researchers from Ontario’s McMaster University, analysed 25 randomised controlled trials worldwide, comparing liberal versus conservative oxygen therapy. The study involved more than 16,000 adult patients with sepsis, stroke, trauma, emergency surgery or cardiac arrest.

He believes the findings could have far-reaching implications for the treatment of acutely unwell patients worldwide.

“A simple change to current practice – being more moderate and cautious with how much oxygen is administered to acutely unwell patients – could save lives” he says. “If you are sick you may actually be better to have oxygen levels in the lower-normal range rather than the normal range”.

In New Zealand and many other countries, oxygen saturation levels which dip below 90% generally lead to the administration of supplementary oxygen. Normal healthy adults exhibit oxygen saturation levels in the mid-nineties range.

However, Dr Young says knowing what exact level of oxygen therapy is potentially dangerous is yet to be established.

“Although this study provides strong support that too much oxygen is harmful, it doesn’t provide definitive evidence about exactly how much is too much, or too little” he says. “

‘More research is now needed to help establish exactly what those safe levels are”

Auckland Hospital Intensive Care Specialist Dr Colin McArthur says the study is of a very high quality and its conclusions reliable.

“Many clinicians have an awareness from earlier studies that too much oxygen may be hazardous, but the hazard was not well recognised” says Dr McArthur.

“This new study now builds a very strong case for what was uncertain before and also confirms we need to be more cautious” he says.

Dr McArthur agrees it’s now vital further research takes place to establish exact safe levels of oxygen therapy and also define how boundary levels may vary among patients with different illnesses.

Dr Young hopes new Health Research Council-funded MRINZ research he is leading may help provide these answers. The study involves 1000 patients from 24 intensive care units in New Zealand and Australia, testing and comparing the results of normal amounts of oxygen supplementation with less.

Results from that study will be available from January next year.

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