JJS jschneider@remove socks cebridge.net wrote:

"Drew Dalgleish" wrote in message ...
snip
N2 doesn't do anything except displace O2 Lack of O2 normally causes
the victim to just pass out almost instantly followed by convulsions
then the cessation of respiration. ( quoted directly from the ontario
mine rescue handbook)

Drew, Can you point me to a link. A very quick google search didn't turn up much from Ontario. I'd like to verify
the "lack of O2 normally causes the victim to pass out almost instantly". Ever see someone in a choke lose
consciousness instantly or go into convulsions after they pass out. I've seen them go unconscious but it took
minutes not seconds and I've never witnessed follow up convulsions.

Totally different situations.

In one, you've got lungs full of stale air.
There is a reasonable amount of O2 in it, even after you pass out
(IIRC).

Hemeoglobin is very clever, but it's not magic.
It releases the molecule it's bound to (O2 or CO2) when it reaches somewhere
there isn't much of that gas.

Normally this is a good thing, but when the lungs are full of N2, not
only do you get the normal release of CO2, but the lungs now actively
strip oxygen from the blood, something which normally never happens.

And, any further breaths simply make this worse, as they get rid of any
oxygen that may have been in the lungs as a remenant, or stripped from
the blood flowing through them.

Much the same thing (though slightly more severe, with the additional
possible complication of burst lungs) happens when you breath vacuum.