No, Wiggy, the partial pressure is the problem as well as less total oxygen.
Hi gums, like you having been through the joys of military aviation med training (British version), altitude chamber runs and (before my civvie days) used hoses attached to the likes of the F-4
through to the (mighty, noisy but unpressurised) Jet Provost Mk 3
I know that partial pressure of O2 becomes an issue, but I would certainly still take issue with the claim in the statement that kicked off this bit of the debate that the
“amount” of oxygen is unchanged at altitude...
Anyhow above all this is a distraction from the body of the thread and I need to add my chapeau” to the crew in the SWA flight.
Rgds
Wiggy