Computers and DCS -- Q to Dr. Deco

[DivingDoc]

I understand that Suunto computers are more conservative in their algorithyms than many other computers.

Does this translate to a lower incidence of the bends in Suunto users or not?=-)

 

[devjr]

Hi DD. If you have been visiting the computer room you probably are intrigued by the complexity of the issues and wonder if you'll ever get a non baffling answer. It's a good question, but after seeing the discussion and outright wrangling going on I personally doubt that there is any clear cut answer on theory, and a general lack of statistics for a particular computer program. Even if Suunto's insurance company has stats, I can't see how they could be normalized to a particular style of diving. I'll bet that's a toughie, even for Doc Deco.

 

[ScubaJorgen]

Perhaps DAN has statistics on correlaton between bends and computer brand.

If you have statistics on this correlation, you should compare it with the market share of each brand. If 60% of the people bent use Suunto computers and 80% of all divers use Suunto computers, than the Suunto computer is 'safer' than average.

Devjr, if you take into account sufficient number of people I do not think it is neccassery to normalize to a particular style when comparing numbers (percentages) of divers bent correlated to computer brand. However, one should only compare the same type of computers (for example computers used for recreational diving). I think for each computer the same distribution of styles apply. In this comparisson, you should not compare air computers to nitrox computers :nono:, since these are used in different dive styles.

It might be interesting to correlate percentages of diver getting bent to region: I think in Belgium they have fairly different diving habbits than here in the Netherlands. Belgians :weirdo: I've seen use to dive to 50m stay there a few minutes and go up again to tell the other belgians how deep they went. We dutchies try to stay as long as possible down there by diving shallower and tell each other what fish :deadfish: we've seen.

 

[Dr Deco]

Dear Diving Doc:

I whole question of decompression algorithms is a complicated topic. Here are some comments, not necessarily placed in any order of importance.

[sp][1.] It is difficult to say what might be better without taking into account the use to which it is put. Many devices with “bells and whistles” might be used by advanced divers who perform stressful dives. The deco device might perform in a manner expected for dives involving considerable musculoskeletal stress and high gas loads. Contrast this with a simple deco meter algorithm “used only by a little old lady on Sunday.” It is possible that the dives could be so simple that trivial gas loads are encountered and nothing untoward could ever be expected to occur.

[sp][2.] The general fact is that the device that allows the larger gas loads will produce more DCS in the long run - - all things being equal. (The corollary to this is that you cannot get DCS unless you are supersaturated.) The lower the gas loads (more conservative), the better off you will be in so far as gas loading is concerned. BUT one can always take a longer surface interval and come up sooner. You have the control of that. The dive table is a "road map" of the gas loads in your body. It tells you "where you are" but you are not compelled to take every road!:mean:

[sp][3.] There are more factors to DCS than only gas loads. It has been known for decdes that individuals vary in their susceptibility to DCS. The reason for this is not known, but genetics no doubt plays a role in the physiology. :baby: This is not in a computer algorithm.

[sp][4.] It is known that activity level will influence DCS susceptibility. Most divers do not consider the fact that the decompression is not over when you surface. The surfacing activity is not in a computer algorithm.:nono:

[sp][5.] Activity at depth will affect gas loads. Algorithms attempt to track this with many compartments. These compartments actually shift, but there are not any true “adaptive computers” in existence today. This is not in any computer algorithm.

These are only a few thoughts. If I knew it all, I'd be president by now..=-)

Dr Deco :doctor:

 

[ScubaJorgen]

Dr Deco,

With respect to point 5 : I've read something about an adaptive diving computer that takes into account work performed under water by measuring the air consumption. I think it takes temperature into account also. I'll look it up...

Stumble.. stubmle... stumble :book2:

Here it is: it is about Aladin computers. It's a internet article

I agree with you: I guess it is not a 'true adaptive algorithm' as you call it. It presumably puts a bit of conservatism here and there :bonk: according to the amount of work calculated and the temperares.

PS I do not have an Aladin. I do not have Uwatec shares...

 

[Dr Deco]

Dear ScubaJorgen:

These decompression devices are of interest in that they have made an attempt to incorporate the diver’s physiology into the algorithm. There are points where I could disagree with what was done, but this is true of any table algorithm.

Basically, the incidence if DCS in recreational diving is very, very low. It is quite difficult to determine the exact cause of DCS in these cases. We live in a world where microbes abound but most people do not contract a disease. Once in a while, someone does. Why? The answer does not always exist when probabilities are extremely low.

Dr Deco
:doctor: