Critical care
A landmark trial found that children given conservative oxygen levels were 6% more likely to survive or spend less time on machines than those receiving standard levels.
cardiac arrest, found a similar incidence of death and severe disability between conservative and liberal oxygen groups – yet, Semler notes, the estimates did favour the lower target.
Semler hopes that the ongoing international trial, Mega-ROX, should be able to provide some more definitive answers. With 40,000 total participants, the trial will compare the impacts of conservative versus liberal oxygen therapy on people with sepsis, brain injury, and following cardiac arrest. “It’ll be the biggest trial ever on oxygen targets,” he says. Yet the question of who may benefit most from receiving less oxygen also raises another: who might be better off getting more of it? “Patients with severe infection, patients with sepsis or septic shock, and many of whom have acute respiratory distress syndrome. Those are the patients for whom there might be reasons why more oxygen would be better,” says Semler.
There are a few possible explanations why. One is that these patients, particularly in the case of sepsis, may not be getting enough oxygen in their cells – so they simply may benefit from having their levels topped up. Another could be that because oxygen is toxic to bacteria, it may help to slow or prevent an infection, Semler explains.
Some research has investigated oxygen targets for sepsis, but as with studies on other critical care populations there’s no conclusive answer as to which levels are best. Here, the Mega-ROX trial results may provide some insight.
Setting the right target Randomised trials can help us uncover the treatment effect for patients within a group, but clinicians on the ground need to figure out which
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treatment is best for the patient in front of them. Someone’s age, sex, blood pressure, and more may all play a role here. Ideally, this means setting personalised oxygen targets. We aren’t quite there yet, but Semler hopes that we’ll soon see large trials that consider a wide range of patient characteristics to help move the needle. This data could be used to create estimates for which type of oxygen target might be better for a given patient, he says.
“Oxygen is a horribly reactive thing that pulls electrons out of other molecules. If you’re exposed to a lot of supplemental oxygen for a long time, that may contribute to the severity of the biological injury you’re suffering.” Mark Peters
Until then, it’s down to clinicians to consider the available evidence in deciding how they’ll administer oxygen. Conservative oxygen therapy is an existing treatment, so it can already be applied at a doctor’s discretion. “Most of my colleagues have already made the change to a lower target in critically ill kids who meet the criteria,” says Peters. While the idea that we should use lower oxygen targets is gaining legs, the next hurdle is implementation: having this as a standard consideration in critical care decisions. “How to close that gap is a major challenge for health systems, even once we have very strong evidence,” says Semler. “It requires effort now, it requires personnel, and it requires focus and emphasis.”
6,000
The number of days spent in ICU beds saved if conservative oxygen was rolled out across the NHS.
The Lancet 51
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