Standard answer ;-) : You never want to on-gas more. You want to keep fast tissues from bubbling too much, in order to avoid an early in-water DCS hit. His specific problem is that due to high work load in a short bottom time, his medium-fast tissues may be more saturated than usual compared to a relaxed dive of the same depth and bottom time. Of course it's a trade-off with slow tissues on-gassing, and GFlow=50 is already a lot more conservative than standard Bühlmann "GF100".
Can you do too much deco?
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Standard answer ;-) : You never want to on-gas more. You want to keep fast tissues from bubbling too much, in order to avoid an early in-water DCS hit. His specific problem is that due to high work load in a short bottom time, his medium-fast tissues may be more saturated than usual compared to a relaxed dive of the same depth and bottom time. Of course it's a trade-off with slow tissues on-gassing, and GFlow=50 is already a lot more conservative than standard Bühlmann "GF100".
One thing about strenuous activity tests is that they usually are focused on lower body exertion in a lab setting, such as peddling. Makes sense because exertion in scuba diving is often related to swimming. But from what I've read, upper body exertion is more likely to create a shunt and that definitely comes into play when commercial diving or possibly doing recovery work. I wonder if deep stops might provide a better cushion to get rid of problematic bubbles in such a case.
Edit: I should add once out of the water, such as climbing a ladder, lower body exertion is more likely to create a shunt.
Edit: I should add once out of the water, such as climbing a ladder, lower body exertion is more likely to create a shunt.
That's an interesting take, but is that a factor when the exertion is at depth (i.e., no bubbles)?
My thought was that exertion during ascent could form more bubbles during an ascent. Maybe a SEAL team swimming hard at depth would benefit more from a dissolved gas model if their ascent wasn't exertive vs. a commercial spearfisherman who might be struggling with a large fish on the way up to the boat? If researchers recreated profiles from the source of deep stops, Dr. Richard Pyle, would they discover similar profiles and workloads would be more advantageous using a bubble model? Maybe his ascents were more exertive than his bottom portion?
Basically, if we are working harder at different points of the ascent such as what would be considered purely bubble phase vs. an overlap between the bubble and dissolved gas phases vs. dissolved gas phase (as we segmented portions of ascents in GUE training for ease of understanding) could it be that deep stops might be a better way to go at one point vs. another?
Richard Pyle does advocate for some exercise during the ascent so that increased perfusion aids in offgassing. Neal Pollock's video presentation here includes a video of members of Pyle's team doing something near the edge of calisthenics.
There is no question that exercise during the deepest portion of the dive increases perfusion and on-gassing. If you go with Michael Powell's (unproven) thinking on the bubbling they found when researching the PADI RDP, that exercise may even stimulate bubble formation. It would indeed be wise to compensate for that during decompression, but there is no reason to do it while very deep and still on-gassing. Pyle's team does it during final stops.
BTW, Pyle did not invent the deep stops concept, although many people credit him with it. He never pretended he did. In the famous "fish nerd" article that became of the deep stops Bible, he credits the work of Yount (VPM model) and Wienke (RGBM model) for the theoretical basis for deep stops.
It might be worth stressing that the people who oppose "deep stops" pretty much all use stops deeper than called for by Buhlmann themselves; they just don't go to the deep stop extremes popular a decade ago.
There is no question that exercise during the deepest portion of the dive increases perfusion and on-gassing. If you go with Michael Powell's (unproven) thinking on the bubbling they found when researching the PADI RDP, that exercise may even stimulate bubble formation. It would indeed be wise to compensate for that during decompression, but there is no reason to do it while very deep and still on-gassing. Pyle's team does it during final stops.
BTW, Pyle did not invent the deep stops concept, although many people credit him with it. He never pretended he did. In the famous "fish nerd" article that became of the deep stops Bible, he credits the work of Yount (VPM model) and Wienke (RGBM model) for the theoretical basis for deep stops.
It might be worth stressing that the people who oppose "deep stops" pretty much all use stops deeper than called for by Buhlmann themselves; they just don't go to the deep stop extremes popular a decade ago.
Workload has no bearing on an individual divers decompression obligation once that person is physically fit enough to do the work. If you're out of shape and puffing and blowing on the bottom that's another story altogether and you're on the wrong job. Your going to get bent.
PfcAJ
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