Bob, the point of our discussion is that things can go bad up there especially in winter. As you know, a good weather day can turn into storm in a hurry, and a moderately paced hike can turn into a fight for your life. So yes, I may have extrapolated your comments to a worse condition but that is exactly the problem. Hope for the best but prepare for the worst. We all agree that being inexperienced, ill-equipped, not acclimatized, unable to make the right decisions (experienced or not), and having no altitude experience other than sitting quietly in a plane (that the poster did not specify height), and a major change in conditions, will all aggravate the risk.
We all often blur the lines of "high" altitude. As for the technicalities, 8,000 -12,000 ft is the official definition of high altitude. Very high altitude is 12,000- 18,000, and over 18,000 is extreme altitude. A pressurized plane is only partially so. Therefore in the cabin at an equivalent of 8,000 ft the passengers are in the high altitude zone. For most healthy passengers this is not long enough to bother them in the sedentary state. But their status is not predictive of their performance with boots on. Take them directly to 8,000 ft, say in Mammoth, and many do notice the effects of that altitude when hiking. Study ALL of them on a treadmill, and the lower oxygen pressure will show reduced performance. Acclimatization will get them only part way back toward THEIR sea level performance. This is true for any altitude and any extent of acclimatization.
Furthermore, 8,000 ft is the medical threshold for the diagnosis of altitude illnesses AMS, HAPE and HACE. Cheyne Stokes-type breathing (now called periodic breathing) was REMOVED in 2018 from the Lake Louise Consensus Criteria for definition of Acute Mountain Sickness (AMS). Periodic breathing is a direct effect of increased altitude (lower pressure) that can occur with or without AMS, and it persists to varying degrees even with acclimatization, so that is why it was removed. It is still a problem (not just for climbers but high altitude residents) but is now just looked at a bit differently.
Much of this is not the thrust of the discussion for Mike. I wonder if he will chime back in and let us know, for curiosity sake, what altitudes he has flown at, and pressurized or not. Harvey
