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Chris,
>I have been contacted by a member of a UK expedition that wiil be
>diving to recover artifacts from Lake Titicaca. Everything is in place, but
>they are still gathering factual information on previous experiences of
>diving at this altitude (3800 metres above sea level). They are particularly
>concerned about any proposed IWR Protocol at this altitude.This is due to
>'local' problems in getting a firm commitment from the Bolivian Navy to treat
>any DCI cases. Anybody got any info? - Factual, documented or otherwise?.
For details on IWR, have a look at the Edmonds protocol (Edmonds et al.,
"Diving and Subaquatic Medicine", 3rd Ed.).
Altitude correction for 100% O2 is interesting. The depth limit for 100% O2
is based on physiological tolerance to high PPO2. Due to the lowered atmospheric
pressure, the depth limit for IWR would be increased from 9m to 12.8m (at
3800m):
PPO2 at 12.8m = 1.28 atm (water pressure) + 0.62 atm (air pressure)
= 1.9 ata
I believe that the IWR protocol would work as written (with PPO2=1.52 at 9m),
but you would have the option of going down to 12m (PPO2=1.82). This would give
you a higher pressure ratio (nearly a factor of 3) for driving bubbles back
into solution. So IN THEORY, IWR should work better at altitude!
Whether there would be any alteration to the body's tolerance to oxygen due to
altitude acclimatization (increased haematocrit, etc.) is probably unknown.
The above is all just SPECULATION based on basic physics. If anyone has any
experience of this, jump right in! (I wonder - has this ever been done before ?)
The main problem with IWR in a high altitude lake would likely be the cold. The
protocol can need up to 3 hours in the water in a stationary position. Make
sure you have some sort of heating system as an additional piece of
equipment. You will also need significant amounts of oxygen.
One thing to consider as an alternative "treatment" for a MILD bend would be to
simply return the victim to sea level as soon as possible on 100% O2. This
would be equivalent to a standard recompression therapy (sea level) of about 6m.
While not as effective as recompression to 18m in a chamber, it is only 3m
shallower than a standard (non-altitude) IWR treatment. The improvement would
likely be significant. This would also be a lot safer than IWR in a
cold lake!
3800m is at the upper limit of the safe range for extrapolation of
sea level dive tables. See "Basic Diving Physics" by Bruce Wienke. You may
want to consult with a tables expert for suitable tables (e.g Hamilton).
Hope this is helpful,
David.
______________________________________________________________________________
David Giddy, Voice: +61 3 9253 6388
Telstra Research Laboratories, Fax: +61 3 9253 6144
P.O. Box 249, Rosebank MDC, 3169, AUSTRALIA Email: d.giddy@tr*.te*.co*.au*
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