In persons without chronic respiratory disease, in healthcare settings
we aim to keep oxygen saturations above 90-90%.

The oxygen content of the blood drops sharply below sat's of about 90%,
so the difference between 90% and 88% is greater than 92% and 90%.

You would be best off to use oxygen for flights in that area.

Dave

Paul kgyy wrote:

I acquired a Nonin O2 monitor a while back and Saturday took it out for
a test ride. I'm 68, mild heart disease, annual special issue medical,
exercise regularly.

With regular deep breathing, I was able to retain 90% or more O2 level
as indicated by the monitor up to 13,500, and felt fine. Given that
one of the early symptoms of hypoxia is euphoria, however, I'd
appreciate if any of you who have tested this stuff would share what
you know about where hypoxia begins for most people?