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Bob,
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.
This supersedes NAVSEA 0994-LP-9010, REV 2, dated 15 December 1988.
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wrote regarding the ppO2 (low pressure) of 0.6 ata has been superseded by more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.
Reference: 3-8.2 Oxygen Toxicity
3-8.2.1 Pulmonary Oxygen Toxicity
3-8.2.2 Central Nervous System (CNS) Oxygen Toxicity
Reference: NOAA Diving Manual, October 1991
The following pages deal with oxygen toxicity: 3-22, 15-2, 15-3,
15-5, 15-12, 16-7, and 20-2.
I would also like to add, when reading these references in the NOAA manual, be
very careful of the ppO2 exposure durations relative to CNS O2 toxicity in
chapter 15 as these are way "too hot". I mean, smok'in!
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.
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.
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!
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 .......
-Joan-
You wrote:
>
>>Also I believe the US Navy diving manual documents the correlation
>>between pseudophrene (sp?) and CNS O2 toxicity.
>
>I checked out the Navy Dive Manual and must confess I haven't found a
>reference yet to O2 toxicity and use of Pseudoephedrine-sudafed(the NDM
>doesn't have the greatest index in the world though) but I did see
>something interesting which ties in with the recent discussions on this
>list on physical conditioning and diving.
>
>On pages 3-20 to 3-21 in the chapter on underwater physiology the NDM
>states that at PPO2's of 02. - 0.6 atm there are no toxic effects
>regardless of duration of exposure. From 0.6 to 1.6 atm exposures from
>"days to hours" lung toxicity may occur. At 1.6 atm and greater you get
>CNS symptoms before lung symptoms. But here's the clincher...
>
>"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
>
>
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