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>To those physiology gurus out there, > >I have been pondering this question for a while now. Please consider this >scenario: > >You're on a deep dive in cold water. You're wearing your drysuit with >normal drysuit underwear. When you have incurred a significant >decompression obligation, you accidently rip your suit on a jagged piece >of metal, and it floods. You immediately abort the dive, but still must >do your decompression. On the deco line you start to become very cold, >and due to the cold, your off-gassing efficiency is significantly reduced. > >Now the question. How can you tell the point at which off-gassing >efficiency on the deco line falls below the off-gassing efficiency >that would exist if you were in the dry, warm cabin on the boat breathing >100% O2? Can you tell? Is there a mathematical temperature model >that would tie into whatever deco algorithm you're using that you >could use to determine this (or the optimal deco profile under >your circumstances)? I suppose that this is a highly individualistic >thing, but perhaps generalizations could be made? > >Christina >-- Christina: Where do you come up with these questions?? <G> During the course of the last couple of weeks we have been busy at builing in workload and thermal modifiers to our ongasing & offgassing routines. We now have a way to add the required bias for cold/warm/hot dives and hot/warm/cold decos Your scenario is a warm dive with a cold deco. Your bias is +1 Ongassing, -2 Offgassing. This is NOT good. Optimal is -1 Ongassing, +2 Offgassing. Now your question is whether it is better to chance a missed deco and go for surface deco on 100% O2, or sit in the water and freeze. I would say that this is going to be Highly dependant on the deco stop that you are aborting from. Obvisouly, the deeper you are upon aborting, and the longer you have been down, the greater the overpressure differential upon surfacing is going to be, and your chance of getting DCS. If it was more than 3 stops from the surface (30ft/10m) I would strongly consider surfacing, re-suiting, and inwater recompression. If you are 2 stops (20ft.6m) it gets muddy. If you are 1 stop (10ft/3m) you could probably get away with it. Last week we spent quite a bit of time working out a surface decompression routine for Abyss to be used by commercial divers. The gist of it is that a diver can ascend from 40ft, regardless of deco obligation, to the surface. We allow him 5 minutes (MAX, 3 min is much better) to get out of his gear, and get into a surface recompression chamber. We then blow him back down to his last depth + a factor, and then decompress him back to the surface as though he were making an altitude dive (suface pressure < 14.7psi). Did this help at all, or did I just add more confusion?? /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\ Christopher M. Parrett, President, Abysmal Diving Inc. 6595 Odell Place, Suite G. Boulder Colorado, USA 80301 Ph.303-530-7248, fx 303-530-2808 Makers of ABYSS, Advanced Dive Planning Software. Available in English, French, German, Italian, Portuguese and Swedish. Abyss, Mixed Gas, Technical Nitrox, Recreational Air. Abyss, Technical Logbooks featuring 22 integrated databases.
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