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>>Also I believe the US Navy diving manual documents the correlation >>between pseudophrene (sp?) and CNS O2 toxicity. _snip > >"The susceptability to CNS oxygen poisoning varies from person to person >and that a major contributing factor is the presence of a high pCO2 from >either "a contaminated gas supply or as a consequence of heavy exertion >or in adequate ventilation". > >Might this mean that the aerobically conditioned diver is *less* >susceptable to the effects of O2 toxicity? Sounds like it. Do we have any >pulmonary physiologists in the audience to help me on this one? DAN? >Robb Wolov Rob, I'm not a pulmonary physiologist, but I have been using the science to maintain a competitive advantage in cycling events over the last ten years---and at 40 I can still beat 18 year olds who would be faster for farther, if not for my use of this "tool". I don't think a definitive answer exists yet as to why some individuals with elite level VO2 max, will have ultra high tolereance to O2 (e.g. a genetic freak like George who can breathe pure O2 at 90 feet), while another with similar VO2 max will be just normal in O2 tolereance. But as to "elite level aerobic" versus "non-athletic aerobic systems" , major differences exist in gas exchange capabilities between the two----aside from superior vascularization in primary muscle mass areas with the elite athlete (which provides the muscles with better gas and nutrient exchange), the volume of blood pumped by the heart of an elite athlete under a work load can be as high as 40 liters per minute, versus less than half as much for the non-athlete. This relates to both gradients and gas exchange capabilities. Clearly, the elite athlete will rid himself/herself of CO2 far more quickly than the non-athlete, therefore decreasing the risk of O2 tox induced by high CO2 buildups. Additionally, a given workload (swimming speed and task) for the ultra-fit diver, mirrored by the sedentary diver, will cause far more stress in the sedentary diver, even in CO2 outpuut ranges which are not abnormally high----anecdotal evidence would suggest that the more relaxed and calm we are, the less effect of O2 Tox... Regards, Dan Dan Volker SOUTH FLORIDA DIVE JOURNAL "The Internet magazine for Underwater Photography and mpeg Video" http://www.florida.net/scuba/dive 407-683-3592
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