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--- PVanscoik@ao*.co* wrote: > Dr. Black, > > sorry to disagree. > > one can develop tolerance to alcohol (induction of enzymes to breakdown ETOH) > one can develop tolerance to many drugs (morphine, etc) requiring greater > dosages > one can affect neurotransmitters with SSRI drugs > BUT all these effects take weeks to develop[and most involve the liver]. > > just how would the nervous system adapt to absorption of N2 in the myelin > sheath? can it alter the action potential? open more ion channels? can it > alter the number of vessicles of ACH released at the synapse? what nitrogen > metabolic pathways exist? Tolerance, adaptation, acclimatization are common among medications, and clinically I see it often. Physical agents including anesthetics and inert gases under pressure are less likely to induce tolerance, but it still happens clinically. You can disagree, but the evidence exists that adaptation to nitrogen narcosis is real, although to a small extent depending on which study you read. There is some very conclusive evidence among saturation divers, as Billy W correctly noted. Having reread all of my references, including Bassett, Lippmann, Bennett, Edmonds, and the many references cited by them, the concept of developing tolerance to nitrogen narcosis is real. It is also consistent with what can be expected clinically. Just how much tolerance you develop remains questionable, and I would guess that for most sport divers it is negligible at best. It certainly cannot be justification to safely recommend deep diving on air. > > compare the deep air diver with a functional drunk. > both can perform routine tasks. > both are compromised with regard to reaction times, judgement, and complex > tasks & fine motor skills. > a novice drunk may fall down walking, an experienced drunk may walk to his > car & drive home. [God help those on the road.] > > i would love to see some real data - repeat hyperbaric chamber dives on the > same cohort & test scores. are we debating facts or opinions? > > peteV > saintpetersburgFL > > I would like to mention once more that these Diving Medicine courses are open to instructors, divemasters, and others, not just medical people. Consider enrolling, as they usually are located at a tropical destination and diving is included in the package. Check out Bruce Bassett's website: http://www.doctorfish.com, Helen Davis' website: http://www.medsem.com, or call DAN for info about their course (next one is 4/29-5/6,2000 in St. Lucia). Mike Black _________________________________________________________ Do You Yahoo!? Get your free @yahoo.com address at http://mail.yahoo.com -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
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