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Yes: more CO2=less brains

davef at cc.usu.edu davef at cc.usu.edu
Mon Feb 17 09:24:01 EST 1997

I second the post quoted below.  Both the original poser of the question AND
several repliers should look in a freakin physiology textbook (or better yet,
several) where the whole O2/CO2 thing is most likley laid out nicely.  I highly
recommend Ganong's 'Review of Medical Physiology' (updated every couple years, an
excellent reference).  From Ganong (17th ed, copyright 1995):

"When the PCO2 of the inspired gas is close to the alveolar PCO2, elimination
of CO2 becomes difficult.  When the CO2 content of the inspired gas is more
than 7%, the alveolar and arterial PCO2 begin to rise abruptly in spite of
hyperventilation.  The resultant accumulation of CO2 in the body (hypercapnia)
depresses the central nervous system, including the respiritory center, and
produces headache, confusion, and eventually coma (CO2 narcosis)."

Less relevent to a crowded classroom situation, but relevent to the dude saying
we can suck C02 levels of several thousand percent without effect:
Some psychiatrist in the 50s wondered about increased brain CO2 levels and had
a bunch of people breathe normal O2/high CO2 concentrations.  The result was
anxiety, hallucinations, convulsions, and eventually unconciousness.  I saw
this ref in, of all places, a book on near-death experiences (the high CO2
hallucinations were very similar to typical NDEs), but I also looked up and
read the original papers.  Can anyone help me come up with the citation?  I
have no idea if further work of this type has been done.  Frankly, it sounded
pretty hazardous for the volunteers.  But then (flame bait follows), 
psychiatry has traditionally been hazardous for its 'volunteers' ;)

> This is my xx-th posting in this thread in 45 minutes. A lot of the *facts* 
> ;) irritate me because they conflict with my physiology books. Just now I see 
> this is a thread cross-posted on comp.ai,sci.cognitive. Explains a lot. I refer 
> for further information on CO2 pbp to any physiological handbook. 
> A man conducting a gee-whizz science show with fifty thousand dollars' worth of
> Frankenstein equipment is not doing anything scientific if he knows beforehand
> what the results of his efforts are going to be. A motorcycle mechanic, on the
> other hand, who honks the horn to see if the battery works is informally
> conducting a true scientific experiment.

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