No, Wiggy, the partial pressure is the problem as well as less total oxygen.
At my mountain cabin the pressure is about 75% of sea level and the total amount of "air" is also about 75%. Since I have COPD, I am intimately familiar with these things. Also wore a nose hose in jets for 20 years, so have been thru explosive decomp and flying unpressurized as high as 40,000 feet on positive pressure, pure oxygen.
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The ATC transcript illustrates an outstanding degree of professionalism. Can't wait to see the CVR.
On my serious structural damage approach I was not as adamant about the serious part and both approach and tower didn't really give me the priority they gave SW1380. Lesson learned, and you don't have to scream at them, heh heh. On my profile and the linked interview/bio, you can see the damage of my plane and might be able to see/hear the video of the approach.
Gums...