Basic lack of O2

This picture looks so benign but the reality was that we were at 18,000 feet which is almost 4000 feet higher than any mountain in the continental US. We had to be continually on guard against AMS (acute mountain sickness). A splitting headache was the first sign.

Sometimes we talked about getting a headache, sometimes we imagined that we were getting a headache and sometimes, when we pushed too hard, we got a headache.