To Dr. Deco: Pelagic vs. Suunto algorithms?

[leadweight]

So far as I know, the only dive computers that takes into account activity levels are the Aladin air integrated series. NDL's are reduced when the computer detects heavy gas consumption. I have absolutely no idea as to what parameters they use, or whether this meter can tell the difference between a 110 pound female at peak exertion and a 240 pound male who is an air hog working a bit more than usual. Anyway, breathing rate is something the meter manufacturers can measure. Once on the surface taking measurements of activity would require a different approach.

Perhaps we will soon see a warning in our dive computer manuals about exercise in addition to the pages of warnings that the authors of those manuals currently paper us with at the request of legal counsel.

 

[Dr Deco]

Hi Leadweight:

Thanks for that piece of info on the Aladdin. That would indeed be a good plan to reduce the NDLs because of exertion. If the gas usage is a result of excitement of nervousness, that would have little effect on tissue blood flow. It would err on the side of conservatism, though.

Dr Deco :doctor:

 

[QKRTHNU]

You could combine gas comsumption with a pedometer to monitor movement, and even a pulse monitor.

Now, if you produce this and make it big remember who gave you the idea.

 

[Charlie99]

QKRTHNU once bubbled...
You could combine gas comsumption with a pedometer to monitor movement, and even a pulse monitor.

Now, if you produce this and make it big remember who gave you the idea.

Gas consumption doesn't necessarily track with isolated strenuous exertions, such as lifting heavy gear or pulling up an anchor. Strong exertions apparently promote formation of micronuclei. Weight lifting -- bad.

On the other hand, low impact, low stress activity such as bicyling or walking might not be bad --- things that fit under his category of "mild activity and gas washout". Mild aerobics ---- good, bad or indifferent ????

Lowest air consumption, movement, and pulse rate would be while sleeping, as Dr Deco noted -- sleeping during SI is bad.

Hmmmm. It looks like we are back to using common sense and moderation.

Charlie

 

[Dr Deco]

Dear Readers:

Activity Levels

It is true that mild activity is good and strenuous is bad. Strenuous would probably not make a big “blip” on the oxygen consumption meter, however, as pointed out by Charlie99 above.

Mild aerobics is probably not too bad. As you say, common sense should tell. The problem is you cannot sell common sense – in fact, you cannot give it away!

Dr Deco :doctor:

 

[DivingDoc]

Leadweight gave a link to an article in Divers' Magazine in which the writer compared 3 dive computers -- including the Oceanic Versa Pro (which he claimed used an algorithm based on our own Dr. Deco's research along with another person), and the Suunto Vytec.

Here's the link:

http://www.divernet.com/equipment/0...tests.htm#versa

He found astounding differences in what each computer would allow you to do.

The real question, however, is:

Does the more conservative Suunto RGBM model computer really protect divers better from DCS or not??? It's hard do believe that no one -- not even Rodales or DAN -- has looked at differences between the presence of microbubbles, vague achiness, etc. or actual incidence of obvious DCS using the RGBM -based computers vs. the Haldane-based ones.

Maybe we should do a poll and ask people who use the different computers feel more or less achy after a dive depending on which computer they use? Not scientific, but more info than there actually is out there.

 

[Charlie99]

DivingDoc once bubbled...
Does the more conservative Suunto RGBM model computer really protect divers better from DCS or not???
....(has anybody)... looked at differences between the presence of microbubbles, vague achiness, etc. or actual incidence of obvious DCS using the RGBM -based computers vs. the Haldane-based ones.

What counts is the profile you dive. Few divers dive right up to the limits.

It doesn't even appear that anybody has done good studies on the exact mechanism of how bubbles cause DCI, much less compared the different computers. DAN doesn't even see much correlation between DCI rates and whether a computer, tables, or "follow the DM" is the method of dive planning. Fortunately, DCI rates are low enough that we don't have much data.

My problem with Suunto computer is that I find it difficult to use the consumed-bottom-time bargraph to devise a good profile --- the display clears to "all green" or even "no bars" when you get much below 30'.

I much prefer the Oceanic display with the bargraph display of the current M-value in the leading tissue. The yellow zone starts at 80 or 85% of M0 --- the same point that has been found by Dan Europe to be associated with higher grades of doppler bubbles. While doing stops in the 30/20/15/10' range, the bargraph continues to give you an indication of overall N2 loading.

As I noted elsewhere, the ideal would probably be a true RGBM computer, with the leading tissue N2 M value bargraph of Oceanic.

 

[leadweight]

Just being dry makes me ache.

Diving makes me feel better.

I think that the bar graph on the Oceanic/Aeris computers is a great idea because it allows the diver to assess his situation in a meaningful way.

My only reservation is that (at least according to the tests in some German magazine) the Pelagic computers seem to go very conservative once the diver goes past the no stop limits.

Charlie's wish is nice, but there are two problems.

1. Patents.
2. It wasn't invented here.

I really like the feature set on Suunto computers, but i have a gut feeling that they are way too conservative on typical recreational dive profiles. OTOH, the Vytec has RGBM 50 which mitigates the conservatism, but even without the wireless pressure sender there is a real premiun in price for the Vytec, and a not so readable display. Perhaps I need 2 computers. An Atmos 2 for most of the time, and my old Aladin Pro Nitrox for days when I want to go past the NDL's.

Meanwhile, Charlie, it looks like you have been reading up on deco & it looks like you know something.

 

[Dr Deco]

Dear Readers:

Conservative Computer Algorithms

Do conservative protect you better from DCS. Not really. Why? Because the incidence of DCS is so low as to make analysis impossible. You can make determination when virtually every result is “No DCS.” The way things of this nature are tested is to perform laboratory tests under controlled conditions. These tests are expensive, and virtually no one – DAN included – performs them. One way around this is to use field data, but most of that is also “No DCS” and does not really tell you much about limits.

RGBM computers will not really show much difference if one performs only recreational diving. The microbubble question plays little role in this case. A little difference appears and is why divers say that they are conservative. Possibly, they are too conservative. DCS is not cause solely by gas loading but also by micronuclei generated by physical activity.

Taking a poll will most like yield little because few divers have problems and few divers will respond to a poll. You would need thousands of responses.

Pain of DCS

It is widely debated. I hold to the studies performed in the 1940s that indicated that bubbles caused pressure in tendons and ligaments and pain resulted.

To that has been added a considerable amount of research on “biochemical mechanisms” of DCS. Among these is the famous “complement.” I do not hold to that mechanism in the case of simple pain-only DCS that comes on within an hour and immediately remits with pressure.

What Else?

The remainder begins to get complicated. It is time once again to mention my “Decompression Physiology” class held at the USC Marine Sciences Laboratory on Catalina. [Some day when I retire from NASA, I will have time to present this in additional places.]

This is the web address:

http://wrigley.usc.edu/hyperbaric/advdeco.htm

Dr Deco :doctor:

 

[DivingDoc]

I should think that at least part of the pain is definitely pressure on nerve endings -- otherwise why would numbness and paralysis come into the picture in definite DCS?

Mild DCS?

How often do you think that mild generalized achiness and fatigue that a lot of divers experience after diving -- especially repetitive dives over a number of days -- represents a mild form of DCS.

I know that I am definitely less achy and fatigued after using Nitrox than after diving the same profile with air.

ET