I went to a dude ranch in CO at a higher altitude (9000 ft) and had altitude sickness. A doctor staying there said it would probably pass. It didn’t. I was easily exhausted and head-achey the whole time.
A former company would try to have meetings places like Breckenridge Co and half the attendees from the east would leave and drive back to Denver the first night.We stop having national meetings at 9000 after a few fiascos .