The initial results of the SUPPORT trial examining the effects of different oxygen limits stopped a lot of us in our tracks. We started these trials because most of us thought that aiming for lower oxygen saturation targets would reduce eye disease, would reduce chronic lung disease and would be safe. We were uncertain enough however to put together randomized trials to scientifically compare the effects of choosing 2 different oxygen targets, to make sure that what we thought we were seeing from observational studies was in fact true.
We confirmed that less oxygen meant less retinal disease, including more retinal disease severe enough to need surgery, there wasn’t really any effect on chronic lung disease (a probably chance reduction from 39.7 to 37%) but there was an increase in mortality. More babies died in the lower oxygen group than the higher group.
The newly published results (Vaucher YE, Peralta-Carcelen M, Finer NN, Carlo WA, Gantz MG, Walsh MC, Laptook AR, Yoder BA, Faix RG, Das A et al: Neurodevelopmental outcomes in the early cpap and pulse oximetry trial. The New England journal of medicine 2012, 367(26):2495-2504) from the 20 month follow up confirm that the difference in survival persists, and now shows that all the actual outcomes on visual function were not different, neither blindness, severe visual impairments nor squint. Even though there were twice as many infants who had eye surgery in the high saturation group as the low sat group.
In addition the neurological and developmental outcomes (at least as measured by the Bayley score) were not different. Significant cerebral palsy was 5% in each group, and a Bayley score less than 70 was about 7.5% in each group.
With the interim analysis that stopped the BOOST2 trials in the UK and Australia also showing an increased mortality, it certainly looks like we should avoid the lower saturation range of 85 to 89% that was targeted in each of the low groups of the oxygen trials. This evidence is also enough I think to encourage us to do further trials examining other targets, as well as looking for other ways of avoiding hyperoxia. If we are to target 90 to 95% saturation, then the risk of episodic hyperoxia will be increased, maybe automated FiO2 controllers, adaptive alarms and other interventions can help us make the higher limits safer to the eyes.