Ooooh, interesting thread which I am going to follow.
I seem to remember trying to learn about "the oxygen desaturation" curve from many moons ago. All I can remember was it was very complicated and "fickle." Different people reacted very differently to similar situations.
Watched that series on ferry pilots recently, couldn't help noticing some pilots were using fingertip pulse oximeters.
Would be interesting to see how useful they are in predicting hypoxia/hypercapnoea issues.