Mailing List Archive

Mailing List: techdiver

Message Display

>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

sorry, but this would not work at all.  At a inspired PO2 of 0.2 bar, 
haemoglobin (Hb) is about 97% saturated, it does not take much of an 
increase in inspired PO2 (less than double, I don't want to work it out )to 
fully saturate the Hb.  It is not saturation of Hb with O2 that produces CNS 
O2 toxicity as the PO2 required for CNS toxicity is far above that needed to 
fully saturate Hb.  It is the dissolved O2 that must produce toxicity.  Try 
a xanax.

regards,

David Doolette
ddoolett@me*.ad*.ed*.au*

Navigate by Author: [Previous] [Next] [Author Search Index]
Navigate by Subject: [Previous] [Next] [Subject Search Index]

[Send Reply] [Send Message with New Topic]

[Search Selection] [Mailing List Home] [Home]