On Friday, December 11, 2020 at 5:54:28 AM UTC-8, wrote:

Uli, I remeber being there with you. One thing that sticks with me was the change in vision when the O2 was restored. COLORS came back.
For the low price of oximeters these days, we should all carry one an monitor our personal response to altitude.
FWIW

... was the change in vision when the O2 was restored. COLORS came back.
Yes John, you are right! It felt like staring into a bright light after being in the dark.
In a nutshell: the CPU between your ears starts slowing down and provide faulty results! Use O2 early and plenty.

Uli
'AS'