Decompression Sickness

[boulderjohn]

Acclimation to high elevation was a key factor in their reports

The need for this varies by elevation. That seems obvious, since a lake at 500 feet of altitude is a lot different from Lake Titicaca. The difference is not linear, though, and the need for acclimation grows significantly greater when you get to the really high elevations. It is one of the problems I have with George Irvine's famous proclamation that divers don't need to pay any attention to altitude in their dive planning. The only factor he considered was acclimation, and he said that by the time you get to the site, get set up, etc., you are acclimated. That is true for the altitude dives most of us do, but when you get up higher, it is absolutely false. That is why the US Navy diving manual's section on altitude diving includes a paragraph in bright red, bold print saying that no diving should be done above 10,000 feet without prior clearance. I am convinced that the failure to acclimate is the reason one of my friends was paralyzed and the other died on a very high altitude dive.

(That is not the only thing wrong with Irvine's statement, BTW.)

 

[shurite7]

The need for this varies by elevation. That seems obvious, since a lake at 500 feet of altitude is a lot different from Lake Titicaca. The difference is not linear, though, and the need for acclimation grows significantly greater when you get to the really high elevations.

Indeed it is. The term acclimation is somewhat problematic. At what point is someone acclimated? In some of the reports I've read acclimation took only a few hours. At higher elevations it took at least a week. In my view it takes longer. A person who lives at a high elevation is much more acclimated than one who has been there for several hours or several days. A non-diving example, I learned about in my physical anthropology class, is women living in the Andes above 10,000 feet are far less likely to have issues giving birth than women who are not acclimated (one who hasn't lived in such high elevations, yet gives birth when traveling to such high elevations). What I mean by acclimation is one who lives at the higher elevations. I very much agree that acclimation is quite important.

It is one of the problems I have with George Irvine's famous proclamation that divers don't need to pay any attention to altitude in their dive planning.

A lot of people have issues with George. Back when I took tech his name was always thrown/bashed around when it came to controversy.

That is why the US Navy diving manual's section on altitude diving includes a paragraph in bright red, bold print saying that no diving should be done above 10,000 feet without prior clearance.

One has to keep in mind high elevation lakes are not the primary domain of the navy. The Navy conducted its tests and moved on. High elevation diving can be done. Like you said, acclimation is important. Extremely slow ascent rates, in my view, are also very important. Using the appropriate gas mix is also important; something the Bolivian military pointed out.

 

[boulderjohn]

The term acclimation is somewhat problematic. At what point is someone acclimated? In some of the reports I've read acclimation took only a few hours.

When working with the PADI tables at reasonable elevations, you are supposed to pretend your first dive is your second, and assume two pressure groups for every 1,000 feet of elevation gain it took for you to get there. I have no idea how they came up with that. That strategy is not to be used when the elevation gets serious. We can use it on a table-based dive at say 6,000 feet, but don't try it above 10,000 feet. I have only dived above 10,000 feet a handful of times, and those dives were very shallow enough that I did not need to be concerned. If I had to do a more serious dive at such an elevation, I would give it a lot of thought and more research before setting out.

 

[deepseamurse]

Just gave my presentation yesterday to the ER staff. They were all really impressed. Thank you all for helping me out with this assignment!

 

[KevinNM]

A lot of people have issues with George. Back when I took tech his name was always thrown/bashed around when it came to controversy.

The actual quote was something like ‘I have no idea, I don’t dive there. But in theory...’. Which amounts to ‘I’m being polite and answering the question because you asking even though I know I shouldn’t”.

 

[shurite7]

When working with the PADI tables at reasonable elevations, you are supposed to pretend your first dive is your second, and assume two pressure groups for every 1,000 feet of elevation gain it took for you to get there. I have no idea how they came up with that.

Very true. I too have no idea how this was determined. Nonetheless, this does not mean a person is acclimated, which in my view, based off of research and experience is important or at least significant to the physiology of the diver.

That strategy is not to be used when the elevation gets serious. We can use it on a table-based dive at say 6,000 feet, but don't try it above 10,000 feet.

Agreed. Besides, most tables state they are not to be used above 10,000 feet. This leads to another question - why 10,000 feet; why not 8000 or 12,000 feet? My dive computer adjusts for dives up to 12,000. I've tried (although I haven't emailed Bruce Weinke who may know) to find where the 10,000 feet came from.

I have only dived above 10,000 feet a handful of times, and those dives were very shallow enough that I did not need to be concerned. If I had to do a more serious dive at such an elevation, I would give it a lot of thought and more research before setting out.

Same here. I also agree about needing more research, including driving over a pass after diving. The material that I read regarding diving above 10,000 feet stated the dives were shallow and the divers used high concentrations of O2, in one case they used nothing but O2.

 

[boulderjohn]

Agreed. Besides, most tables state they are not to be used above 10,000 feet. This leads to another question - why 10,000 feet; why not 8000 or 12,000 feet? My dive computer adjusts for dives up to 12,000. I've tried (although I haven't emailed Bruce Weinke who may know) to find where the 10,000 feet came from.

Just a little more---

When a group of Swiss divers got bent on a high (not seriously so) dive using the Bühlmann algorithm, Bühlmann did further studies and came up with adjustments based upon altitude. His high altitude adjustments were tested at Lake Tegucigalpa, at about 12,000 feet, and no one got bent. IIRC, that was his ZHL-16C version. At least that algorithm has had that much adjustment for altitude.

If you use V-Planner or Multi-deco to plan dives and input something like 16,0000 feet for a decompression dive, you will get a plan that is not all that different from a plan at much lower elevations. Since no one to my knowledge has done a decompression dive at that elevation, I would not have a lot of confidence in that plan. I talked about that with a tech diver who is also a decompression consultant for NASA and the Pentagon (U-2 flights), and he said that only about 5-6 people in the world have the knowledge needed to plan such a dive. He believed he was one of them. He took a wild guess off the top of his head and estimated a total decompression time for a 20 minute, 200-foot dive that was hours longer than what you will get from one of those decompression software programs.

 

[shurite7]

Just a little more---

When a group of Swiss divers got bent on a high (not seriously so) dive using the Bühlmann algorithm, Bühlmann did further studies and came up with adjustments based upon altitude. His high altitude adjustments were tested at Lake Tegucigalpa, at about 12,000 feet, and no one got bent. IIRC, that was his ZHL-16C version. At least that algorithm has had that much adjustment for altitude.

Do you have a copy of this report or know where it can be obtained? I haven't come across this one.

 

[boulderjohn]

Do you have a copy of this report or know where it can be obtained? I haven't come across this one.

Beleive it or not, you can find it on Wikipedia.
Albert A. Bühlmann - Wikipedia

 

[shurite7]

Beleive it or not, you can find it on Wikipedia.
Albert A. Bühlmann - Wikipedia

Imagine that, Wiki. Thanks John.