water vapor pressure in lung alveoli

[moose_grunt]

Hello. I've been looking through source code for buhlmann decompression programs, to try to get a greater grasp of what is actually going on in the model. An inconsistency I've found is that some programs/discussions (diy deco) only talk about subtracting the water vapor constant from the lungs, while others (Baker's decompression lessons) subtract the water vapor constant AND a CO2 constant. Is this simply a matter of age, that the "old" way of thinking was to subtract only the water vapor, then someone "discovered" that you should also account for the co2 pressure in the lungs? Or is the difference so miniscule that it doesn't particularly matter, unless you are doing epic deco?

Thanks!

 

[Dr Deco]

Hi Moose Grunt:

The difference is not really important when one considers that, for example, a dive to 66 feet is 3 ATA (3 x 760 torr) and the CO₂ level is about 40 torr in the lungs. CO₂ is not a large fraction. The metabolic gases are really taken care of in the surfacing tissue tensions that are determined by experiment.

Whatis not considered in tables are the micronuclei. These can also play a very important role. They are not trivial by any means.

 

[moose_grunt]

Thanks for the reply! I kind of had that feeling, that some people include it to be precise, and some people save themselves the few lines of code since it wont make a huge difference.


I do plan to go the vpm/microbubble direction, but found it prudent to complete my knowledge of the buhlmann algorithm first....

thanks again!