The other big problem with measuring oxygen saturation is that it reinforces the mis-conception that acclimatization and athletic performance at altitude is all about Oxygen.
Ignores Carbon Dioxide, which is physiologically very important for human symptoms and performance.
. . . (also ignores Nitrogen, but that's _not_ so relevant to human physiology at altitude -- but very important for certain plants).
Note that if acclimatization were simply only about Oxygen, then one-week holidays from London to the Alps would not work -- because it requires two weeks to significantly increase red blood cells and hematocrit.
Ken
Post edited at 17:23