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>What issue of the US Navy Diving manual are you reading from? I have what I >believe to be the current issue which is: > >U.S. Navy Diving Manual, Volume 1 (Air Diving), REV 3, 15 FEB 1993. Nope! Rev 2 (that'll learn me) Keep in mind that AFIP is a pathology ref lab, I was happy to get *any* copy of the NDM. But no excuses...your info is more up to date! >The reason that I am bringing this to your attention is that the >information you wrote regarding the ppO2 (low pressure) of 0.6 ata has been superseded by >more current information on pulminary or 'whole body' oxygen toxicity in volume >1, revision 3 of the NDM. All the more reason to pay a visit to the GPO to get my own personal (latest) copy! > >O2 toxicity is BOTH pressure and time dependent and the general consensus >among a considerable number of experienced divers is to keep it at or below 1.4 >ata ata @ a maximum bottom time of 50 minutes (US Navy); 1.3 ata is even 'more >bettah' to provide a wider zone to avoid a CNS hit. At least that hasn't changed. ;-) > >According to the U.S. Navy you can do 1.3 ata ppO2 indefinetly -- well, >with in >reason of course because this is somewhat also affected by the type of >delivery >system too. Did I misinterpret this? Even in Rev 2 I thought that only up to 0.6 atm was "indefinite" duration. The 0.6 to 1.6 atm levels gave lung damage (I assume alveolar damage from oxygen free radicals) >The Navy went to this 1.3 ata value apparently because hyperoxic gas >mixtures tend to increase arterial CO2 levels, which, when coupled with higher than >normal (sea level) partial pressures of oxygen over a defined (finite) >period of time, exacerbates the onset of CNS O2 toxicity. Whamo! That was the conclusion I came to from the less detailed statements of Rev 2. Seems like Nature's joke on divers. > >This doesn't mean that they don't dive higher ppO2s and longer exposure >durations but it does mean that they get to convince the Chief of Naval Operations and >others for approval to do it. And let me tell you, getting your mothers permission is a >whole lot easier ....... Hey, It's an old Navy tradition..."It's easier to ask forgiveness than permission!" Thanks though for the more up to date data! My apologies to the List for any confusion I might have caused. Robb Wolov
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