The babies with the higher levels of oxygen saturation developed retinopathy of prematurity more frequently than those with lower (13.5 percent versus 10.6 percent), but nowadays the condition is treatable and does not usually lead to blindness.
By contrast, the other trial did not find any difference in the mortality rates of infants treated at higher and lower levels of oxygen saturation of the blood. The authors followed up the infants for longer — 18 months — and used a broader measure of outcome, namely a combination of death, gross motor disability, cognitive or language delay, severe hearing loss or bilateral blindness at the end of that period. Here, I confess, I found the results horrifying: in the high oxygen saturation group, 15.3 percent had died, while in the lower 16.6 percent had done so (a difference in rate so small that it was not statistically significant, that is to say it could have arisen by chance), while 34.4 percent of the higher and 35 percent of the lower saturation level babies suffered from at least one of the other conditions, namely gross motor disability, cognitive or language delay, severe hearing loss or bilateral blindness. Survival is thus often bought at a considerable cost: forty percent of survivors were handicapped or severely handicapped.
Naturally further research is required: it always is. The trials tested only two ranges of oxygen saturation, 85 to 89 percent and 91 to 95 percent. Other ranges were not investigated, as in theory they could be. Furthermore, a more prolonged follow-up of the infants might reveal differences between the groups that developed later in their lives.
What, then, is the neonatologist to conclude from these inconsistent results? He cannot, like Tybalt, just exclaim, “A curse on both your houses!” He has to make a choice.
One trial found no difference between the outcomes and the other a better outcome with a higher level of oxygen saturation. It seems to me, therefore, that he should choose the latter, because it might do good and has not been shown to do irreversible harm. But still one would prefer to have no inconsistency in the scientific results. However, in medicine inconsistency is the norm.
ASK DR. DALRYMPLE…
Do you have a question about health and medicine you’d like to see addressed? Click below to contact PJ Lifestyle.