Oxygen therapy and saturation levels

Only a few years ago, back when I was in medical school, I was taught that the goal of oxygen therapy should be to push saturation above 95%, and that anyone who comes in to hospital with a saturation below that should receive oxygen therapy (with the exception of people with chronic obstructive pulmonary disease, whose bodies have adjusted to lower oxygen levels). For those who aren’t used to the terminology, the definition of oxygen saturation is the proportion of haemoglobin molecules in the arteries that are “saturated” with oxygen. A normal level for a healthy person is usually 97% or higher. In the last few years, however, there’s been a bit of a shift in thinking. It started with the realization that people with heart attacks who were treated oxygen didn’t do any better than those who weren’t. This is a good example of a medical reversal – it seemed logical to give oxygen to people with heart attacks, because a heart attack is a blockage in one of the arteries that supply…