The hemoglobin in the blood adjusts to compensate for various O2 levels. I’m not sure what the transition adjustment time is but the body is functioning O2 deficient after it adjusts for the higher levels in the chamber.
I observed a woman get a bleeding capillary in her eye due to the excessive vascular growth caused by the vasco endothelial growth factor (VEGF) which is a mRNA. VEGF increased in the bloodstream when their is O2 deficiency.
It would seem that there is a way to cope with changes in oxygen levels. I’m getting older and live at over 9,000 feet with some physical difficulties but no mood problems at all.