"Roger" wrote in message ...
snip

"My Guess" which is all I can do from here, is there may have been
some traces of something other than N2 there. BUT as has been
mentioned, loss of consciousness is quite rapid in a pure N2
atmosphere. It's not usually instantaneous but quick. More like 5
to10 seconds which is about the time it takes for the process of
"removing" O2 from the blood in the lungs and the oxygen depleted
blood reaching the brain. However from my training (which was a long
time ago) the convulsions appear very soon, or almost as soon as the
loss of consciousness.
snip

Our lungs work based on the "partial pressure" of O2 in the air. When
the partial pressure of O2 in the air is normal the lungs pass O2 into
the blood where the red blood cells bind the molecules of Oxygen and
carry it to where it is needed. Just about the first location being
the brain.
When the partial pressure drops below a given value (I've forgotten
the actual value) the lungs cease to pass the O2 into the blood
stream. Only a slight decrease from that point will cause the process
to reverse. Two things will cause this. remove the O2 from the
atmosphere and/or reduce the atmospheric pressure. This is the reason
why breathing pure O2 at high altitudes using a canula doesn't work.
You need the pressure of a mask.

OTOH blood that has had the O2 removed has an effect on the brain that
is quite different than Oxygen starved blood. It really messes with
the brain and does so quickly which accounts for the rapid onset of
convulsions. It's my understanding that the onset of brain damage is
also much faster as the blood is actually scavenging Oxygen from those
cells. The whole system has been thrown into reverse. The drop in O2
in the brain causes the neurons to start firing randomly which of
course results in convulsions.

That makes getting not just fresh air, but pure O2, to the patient as
quickly as possible, *essential* as you only have a small fraction of
the time normally available that you would have in the case of
asphyxiation. Even when pure O2 is applied you not only have to get
the amount of O2 in the blood up to normal, but it has to re oxygenate
areas that have less than normal amounts of O2, maybe way less. That
means the lungs themselves are going to be using up the O2 for a short
time before there is enough to supply the brain and the lungs are
going to be dealing with Oxygen starved blood for some time.

The brain is supposed to be capable of lasting up to 3 minutes or
possibly more without fresh air, the time available in this case may
be less than a minute. So, it is possible that this was a case of
inhaling pure N2 which would have given him just about time enough to
put the mask back in place before going down. The convulsions would
have probably started about the time he hit the floor.

Again, though, I stress it has been a long time since I had to deal
with this stuff on a day-to-day basis and I have not kept up with it
since then. "I think" which means I don't really know for sure, but
the treatment is pure O2 as quickly as possible and then like CO
poisoning, you keep the patient still as movement can make the
situation worse if done before the blood has been completely re
oxygenate.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Thanks Roger. I believe this "disagreement" turned into a relevant discussion and good learning experience, (at
least for me). I wish all newsgroup threads would follow this example. The ERT did try and start high flow oxygen
on the victim as the first priority, however he was so combative that he kept knocking the nasal canula/mask, off.
(I can't remember which was used, perhaps both. This incident happened circa 1999). He was physically restrained and
tied down in a stokes basket on a back board while one guy held the mask in place as best he could.

From what I've gleaned from the discussion I still wouldn't consider nitrogen poisoning a true "poisoning". I can't
really say I'd consider it suffocation either, at least as I previously viewed suffocation. And if you type
"definition of toxic" in Google and peruse what comes up you can argue all day long whether nitrogen is toxic and
both sides could be considered correct. There is much more to this oxygen, carbon dioxide exchange than I was aware
of. And it amazes me that the exchange works fine when breathing in air that contains 78% nitrogen and 21% oxygen...
but in atmospheres containing less than 19% O2 we start starving for oxygen and at some point the exchange actually
reverses and O2 is stripped from the body? The older I get the less I know! And how in the heck we went from medal
winners: ATC tapes to this!

I'm headed to the airport. It's pretty outside!

Joe Schneider
8437R




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