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I have been following with interest the discussion between John Crea and Scot 
Anderson about the effects of carbon monoxide at elevated pressures.  It has, 
however, been somewhat difficult because John has evidently been sending his 
replies to Scot only, while Scot has been sending his to the entire group.  I 
therefore ask John to include the rest of us in similar discussions in the 
future.  

I would like to add to the discussion a paraphrase of what John has already 
said -- or at least implied:  The thermodynamics are still valid even, if the 
equilibrium constants differ by a couple of orders of magnitude.  The effects 
of most toxic gasses increase with depth (in proportion to the partial 
pressure of the gas), but carbon monoxide is a special case because the 
partial pressure of oxygen also increases.  I would also like to point out to 
Donald Ward that the available number of CO molecules is proportional to the 
partial pressure of the gas.  

All of this brings up another possibility which I shall advance, obviously (I 
hope) tongue-in-cheek.  It should be possible to reduce (or eliminate) the 
possibility of CNS oxygen toxicity by adding a little carbon monoxide to the 
breathing mixture.  At about 10 atmospheres the amount of dissolved oxygen 
becomes comparable to the amount normally carried by the hemoglobin, and it 
should be possible to go several times that depth before encountering CNS 
symptoms.  Someone was asking about drugs to prevent CNS oxygen toxicity.  
Isnt this much better?  It would be amusing for someone to calculate the 
amount of CO required as a function of depth and the number of hours of 
decompression required (here the kinetics of the dissociation reaction would 
also have to be considered) to get rid of the carbon monoxide before returning 
to the surface!  

Bruce Gerhard

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