0% stage 3

It's known that the brain turns off its O2
sensing ability (and maybe mechano-stretch sensing ability
w.r.t.chest and diaphragm rise and fall, and nose passages)
when entering sleep. Only the CO2 alarm remains to wake us
up out of sleep, if indeed something has happened to our
environment while we are in deep sleep that has cut off our
air supply.

Since Stage 3 (or 4) is
an even deeper version of "turning off all bodily alarms/
sensors", the brain might have evolved a heightened
sensitivity boost to be activated, upon entry to Stage 3.

Akin to Avram Gold's hypothesis that a severe stress like
being in the Gulf War, sensitizes the H.P.A.axis to become
easily tripped, perhaps a severe life stress can sensitize
one's general anxiety center, or specifically the CO2-related
part, apart from the _natural_ and proper elevation of
CO2 sensitivity that everyone has in deep sleep.

This compounded combination then would (pathologically)
prevent stage 3 from ever being allowable. The "threshold"
is instantly tripped, in other words.

(
http://www.nytimes.com/2016/01/24/opini ... -fear.html

"Curiously, that might help explain why some people have
panic attacks that wake them at night. These patients don't
panic during so-called REM sleep, when dreams occur, but
during non-REM sleep, when they are deeply relaxed, when
breathing slows, and the levels of carbon dioxide rise,
generating a false suffocation alarm.")

For those that aren't up to speed on the newly recognized sleep stages (they changed a few years ago), here's a graphic.



I can't comment on the post the OP made, that will require more research than I can do at the moment.

1041 wrote:It's known that the brain turns off its O2 sensing ability (and maybe mechano-stretch sensing ability w.r.t.chest and diaphragm rise and fall, and nose passages) when entering sleep. Only the CO2 alarm remains to wake usup out of sleep, if indeed something has happened to our environment while we are in deep sleep that has cut off our air supply.

I don't think you understand how any of that works. when you don't have enough oxygen, you get confused, faint, and die.
when you have too much co2, you start breathing madly to try and get rid of it.

there is no "O2 sensing ability" that gets turned off.... that would be evolutionary certain death.