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>> Yes, they in-gas slower, but in-gassing and out-gassing work on different >> gradients. > >Hrm, ok, what I guess I am driving at is this. At least as I understand >them, the simple Haldanean tables (Navy, PADI RDP) assume exponential >ingassing and offgassing with the same time constants(in/out), but it >is exponential, not linear, so maybe the gradients aren;t the *same* >but supposing that diver A offgasses more slowly, and he also ingassed >more slowly (so his tissue loadings were lower than would have been expected) Mike, My whole point is that I think we can prove diver A has an off-gassing rate not predictable by a simple percentage of his in-gassing rate...Lets say diver A just ingassed one liter of N2 on an hour dive. Diver B, the athlete, ingassed 3 liters of N2. If the present tables were safe for diver A, they would not be safe for diver B. If diver B was able to offgass sufficiently by a safety stop, also made by diver A, and they both make the surface with no DCS, then after an hour the amount of reduction of dissolved N2 in Diver B has decreased much faster than diver A--at some point passing him and becoming "cleaner" if a repetitive dive was planned. It does not matter that Diver A ingasses slower---ingassing takes much less time than offgassing. Differences in offgassing rates will therefore be exponentially more important as the exposure increases at technical depth and durations. If both A & B did 270 fsw for 25 minutes, both would be doing stops from 50 feet. When they begin, A may have less N2 saturation, but by the 20 or 30 foot stop this should have reversed, and by the 10 foot stop B should be much less saturated. And after a surface interval, B may be able to do another dive, whereas A should be sucking O2 still. VO2 max will be the critical measurement because it not only relates the rate of gas exchange, it does it in relation to the volume of the individual's body (and of course larger volumes hold more dissolved gas)...As VO2 max goes up, usually the volume or weight of the person is decreasing. Very large people have typically low VO2 max values even if they have a powerful heart, because there is so much volume for transfer to take place within. Dan >then might this be a double-negative situation that washes out? ie. for >whatever the reason, a section of tissue ingassed slowly, whereas the tables >would predict a group G, he might only be saturated to level F, so... >ok now I'm confusing myself ;-) but maybe I am still getting my >question across. > >Now eventually the slower offgassing might cause one to want to add a >slower compartment (like 720 or something) as this person wouldnt offgas >the slower compartments as fast as expected... > >> not keep pace with in-gassing, and in fact should be modified for an >> individual's gas exchange potential. > >Well of course then we should start looking at lung capacity, breath >rate, ammount of dissolved mgN2, etc. It'll be great when it >gets this precise (god knows when) but.... > > > >-- >Mike Zimmerman < zimmmt@au*.al*.co* > Alcatel Network Sytems, Ral, NC >*My opinions, not Alcatel's* [\] NC Diving: http://www.vnet.com/scuba/ >A is A. Man who say it cannot be done should not interrupt man doing it. > > Dan Volker SOUTH FLORIDA DIVE JOURNAL http://www.florida.net/scuba/dive 407-683-3592
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