I am still trying to figure out why I don't have any acclimatization problems while going up to the summit of Mt Whitney, but nearly always get a nasty headache or two on the way down.
Takes time for bad stuff to happen. Some is fast, like pulmonary artery hypertension on exposure to lowered O2. But some of the metabolic effects, like brain swelling, take time to be manifested. It is bizarre _ I once hiked on first day up from mosquito Flats to Chickenfoot Lake, just 2 hrs. No problem getting there, but nasty headache on way back . Wife had it, too, although she is sensitive and it was expected for her as a slower acclimatizer. "Only" 10,000 ft
It is said that there is a continuum from simple AMS headache to HACE to death. The latter is rare at 14,000 but once you see this bad stuff happen in the Greater Ranges you will never forget it.
