Nicely played, madbuck! That’s what I was seeking but couldn’t find with my own Google efforts.
I scaled off that first chart and it shows nominal SaO2 levels of ~93% at 10,000‘ and ~85% at 14,000‘ for a drop of about 8%. And since that’s roughly half of the 14.6% drop in atmospheric pressure between the two elevations -- and the chart is fairly linear -- it seems like “Change in O2% level = apprx. half change in atmospheric pressure”
might be a crude rule-of-thumb.
It also supports a value I ran across for Everest. After my first post, I recalled reading somewhere that O2 levels way up there have been found to be in the 60% range.
So I Googled that and did find references to that being the case. And, sure enough, the 8800 meter point on that chart lines up with about 63% on the SaO2 level. So that crosschecks well and the above “rule-of-thumb” still seems to be in the ballpark as the O2 percentage drop (from 10k’ to 29k’) is about 32% or around half of the 55% drop in atmospheric pressure between those same two elevations.
Again, thanks for the effort & info, madbuck.