Hello Ross,
In recent on-line discussions with me you have on many occasions quoted the standard equations used to track gas uptake and elimination from tissues. I presume, therefore, that you know what the symbol "Q" represents because that is your answer right there.
To the OP,
Breathing more than you need to makes very little change to the alveolar inert gas composition, and would not of itself be expected to materially change gas uptake or the risk of DCS.
In contrast, since it is the blood that carries dissolved gas to the tissues, anything that increases tissue blood flow (perfusion) during the process of gas uptake will result in faster uptake of inert gas into tissues. Thus, if the increase in breathing was precipitated by exercise (which increases cardiac output and tissue perfusion) then it will be associated with faster inert gas uptake and (all other factors like ascent rate etc being equal) greater decompression stress.
The same principle applies during decompression - improved tissue perfusion will accelerate inert gas washout whereas merely hyperventilating would not make any difference. That is why gentle exercise is sometimes recommended during decompression. It is also why the prebreathe protocols for de-nitrogenation prior to space walks incorporate exercise. The astronauts wash the inert gas out more quickly.
Hope this helps,
Simon M
You are adopting the "perfusion limited" concept of on /off gas levels. So by using that explanation and interpretation of human tissue gas kinetics, we should see clear trends within in the DCS history and case reports. It would show that dives that involve more exercise, but use the same levels of deco time, would have more prevalent injury rates. Is that the real world case? Probably not. So what does that say about "perfusion limited" on / off gas levels concepts?
Astronauts are not a good example for diving or normal circulation. They float around with no effort or motion of the extremities for hours and days. Their circulation issues are unique to the environment. NASA - Your Body in Space: Use It or Lose It
For divers, a big potion of the problem is warding off the (proven) effects of cold, and our most common method is motion and exercise in water to restore/improve circulation of heat. But that situation cannot be confused / substituted with the perfusion limited on gassing concept.
Above I asked DDM to show some definitive testing or results to back up this concept of "perfusion limited" levels of on/off gas levels in diving. Same goes for you Simon. But none has been provided yet.
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