And that's correct. Mea culpa as I incorrectly placed Leadville at 12,000 feet.

I think the argument has morphed into: Can people actually be "usefully conscious" at altitudes above 12,000 feet? Clearly, they can.

My BF and I drove up Trail Ridge Road in RMNP. He's acclimated to Boston; I'm acclimated to Denver. At the top, he bounded out of the car and wanted to climb the hill to the tippy top - another hundred or two hundred feet of elevation. I plodded along; he anteloped. Then, at the very top, he said "headache out of nowhere" and we descended back to the car much more slowly. My only symptoms were being a bit out of breath - I commented that it was like being on the elliptical. He had increasing headache pain concentrated around the back of his head and became miserable. I knew the only cure was water and lower altitude. 20 minutes later, we were below 9,000 feet, and it was as if it had never happened to him. I really didn't feel much different at all.

Neither of us lost any kind of "useful consciousness." But I know this isn't the same as being at effectively 8,000 feet and moving to 35,000 feet in a matter of minutes or seconds (but with supplemental oxygen immediately available).