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Hi Rich:

As far as I understand what you were saying, it goes like this:

In a supersaturation model (like all commercially available tables, 
programs, etc), OUTGASSING (good!) rate is governed by the gradient of 
tension between tissues and arterial blood:

Rate ~ (Ptissue - Parterial)

Ptissue is set by dive history using conventional parallel compartments.

Parterial decreases with depth, so the largest elimination 
gradient for disolved gas occurs by reducing pressure as much as possible 
(within limits of M values). This is why traditional supersaturation 
models emphasize long, shallow stops.

Now, in the radial diffusion equation describing bubble growth, you find 
that the rate of GROWTH (bad!) depends on the gradient between tissue 
tension and bubble pressure:

Rate ~ (Ptissue - Pbubble)

Pbubble increases with depth (possibly causing the growth rate to be 
negative = shrink rate), so this is why bubble models emphasize deep stops.

Of course, some gas remains dissolved while some forms bubbles, so there 
needs to be a trade off between deep and shallow in setting allowable 
gradients for calculating stops. This is where the modeling (guess work) 
begins.

Regards, EM

_____________________________________________________________
Eric Maiken                    email: ebmaiken@ea*.oa*.uc*.ed*              
Dept. of Physics                   o: 714 824-6621   
U. of California                 fax: 714 824-2174
Irvine, CA 92715-4575

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