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At 5:29 PM -1000 8/8/96, Richard Pyle wrote: >Hi Robb, > >> Oxygen at depth through radical and other mechanisms not fully understood >> can (and does) have a toxic effect on the central nervous system (leading >> to convulsions and the like) but not a "narcotic" effect in the strict >> medical sense of the word (loss of alertness, dulling of the senses, loss >> of inhibitions and so forth). > >My best understanding of this issue (from discussions with Hamilton and >others, and from my own experiences) is that the jury is still out >regarding the narcotic potency of oxygen. The details are in the >archives (look up "O2 narcosis" and "oxygen narcosis"); let me know if you >want me to elaborate. I obviously missed the point a bit. I became so hung up on the lumping of O2 chemically under the mixed gases (which we all agree it's not) from the real question of to what degree there is a narcotic vs a convulsive effect from O2. I'm showing my true colors as a "lumper" tending to oversimplify. I went back last night and checked Mount and Gilliam's mixed gas book and indeed they don't include O2 with their ranking of inert gas narcotic effects (but that's not surprising since we all agree that O2 isn't an inert gas). The problem initially seems that the theories involving lipid solubilities are based on an inert gas model....and again O2 isn't an inert gas. The more chemically active electrons of O2 (especially O2 radicals) have effects on the lipid bilayer that an inert gas (by definition) will not. We know clinically that effect is profound or you wouldn't get convulsions. (we also know chemically that the radical form of O2 literally tears up the lipid bilayer) That doesn't mean there can't be a narcotic effect, just that there are additional chemical and physiologic factors to take into consideration when dealing with O2. I'm also lulling myself into the assumption that the narcotic effect of O2 is probably of such relatively small effect (when compared to the much greater volume of inert gas, be it N2 or other) and it's narcotic effect that it probably is getting swamped out. Now that's only my assumption. I'm sure Bill Hamilton's thinking and findings are based on far better experience and knowledge. What worries me is what do you do if O2 *IS* a significant narcotic at depth? There are alternatives to N2. But what do you choose instead of O2? ;-) Robb W ==================================== CDR Robert B. Wolov, MC, (FS), USNR Department of Orthopedic Pathology Armed Forces Institute of Pathology Washington, DC 20306-6000 wolov@hi*.co* (preferred) wolov@em*.af*.os*.mi*
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