Open source decompression tables?

Mdemon

Let's face facts. People are getting undeserved hits on current decompression software. Divers are diving to depths and in a style outside that validated by any formal man/animal testing.

There seems no likelihood of any more data being made public. Yet there is a mass of research and any number of doctors who have looked into the subject, to say nothing of the experience of those who have been diving rebreathers for years.

I wonder....

In the same vein as the open source rebreather development, would it be possible to get some of these doctors together, along with some mathematicians, divers (and ex-Comex employees...) to work on decompression tables/algorythms suitable for the non-commercial deep rebreather divers, the like of whom frequent Rebreather World?

Could it happen? Should it happen?

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"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

lizardland

It's already been done, that's how VPM got out into the sweaty mitts of muppets like us.

The Decompression list (I think now defunct) began as the VPM list and started life as a way of developing the maths behind it. It had loads of big names on it in the hyperbaric medicine & deco modelling world, including David Yount, Bill Hamilton, Richard Vann, Bruce Wienke (whose rantings along with GI3 strangely coincided with the death of the list), Eric Baker, etc.

It was an excellent project in its day, as I remember quite a few of us on here were members and will remember it. I'm sure there must be an archive somewhere.

Cheers,

Stuart

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koputai

Hmm, that doesn't bode well, as VPM in the early days bent more divers than anything else in the history of deco.
I don't think it would happen again. Economically it's not worth it for the guys who REALLY know their stuff.

Jason M.

nigelh

Are they?
You're believing that stupid Comdex man.

Bühlmann's stuff was all published and although people argue his helium tables are a bit conservative that isn't so much of a bad thing.
The only 'undeserved hits' I've seen were squarely dehydration.

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nigelh

Drmike

VPM hasnt been man tested (at least not in any real meaningful sense)
Buhlman has and has a good record.

The USN man tested (Buhlman?) and commisioned/man tested their own CCR tables (Nitrox and Heliox) to a level they were happy with (IIRC it was 1%?)
edited:
http://www.stormingmedia.us/88/8863/A886383.html

Lots of other good stuff available here:-

http://www.stormingmedia.us/search.html?q=decompression

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Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

Mdemon

Nope. Discussed this with the doc at DDRC in Plymouth. A lot of the divers they see have nothing in their profiles to explain their symptoms (including myself). That's not to say dehydration/poor condition/technique isn't to blame for some of them, but I don't believe all

Thanks for the info on the VPM thing, I didn't know that. The fact that they have recently added the b/e stuff would suggest that people were getting bent on the longer/deeper stuff. If they weren't, then why would they be updating it?

So, is the conclusion that the current deco software available is now infallable and we should cease worrying about it? I'm not sure I feel that way myself...

__________________
www.southwestmafia.com

"small minds talk about people, Average Minds Talk About Events, GREAT MINDS TALK ABOUT IDEAS!"

The WRONG Attitude will get you killed.

"Once the agenda-monkeys and perfect-worlders have moved on, perhaps we can do some diving?"

JS1scuba

Validation of diving tables is a hard thing to do. It requires funding and controls. As best as we know the following have been validated.

USN (workman)
Buhlman (Navy EDU)
Rogers / Powell (PADI) but only no-stop
Hamilton DCAP (for swedish navy but applicable across board)
DCIEM (doppler tested)

Most tables in use today have empiracle testing. For example the Hamilton DCAP tables while validated by Swedish navy in the 80s actually got its best testing during the 1990s when we were using them under the "Key West Consortium" with thousands of mixed gas dives on them. Excellent results helped prove they work well, even though they were long. At TDL we incorporated DCAP and Hamiltons Bubble Model into NAUTILUS because it was such a good model and had a proven record.

The problem with some of the deco today is "deco on the fly" being done by folks that have little clues to what decompression is. Add to that deco on the fly for CCR or SCR and you have some interesting results.

I read a post today that showed a 90msw dive for 15 min with just 45 min of deco and the one of the three was bent hard. Every model i looked at required 60 min of deco ....... i shake my head.

FWIW and an plug -- NAUTILUS will run 5 models in both OC and CCR -
Hamilton - DCAP, Buhlman, Hamilton Bubble Model, Yount-Hoffman Bubble model and USN Workman ...... A lot of CCR folks are using it now.

All dive tables work until they dont!


Cheers

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Tech Diving Limited a Division of Scuba Training and Technology Inc.

http://www.nautilusdiveplanner.com
http://www.nobubblediving.com

Drmike

When I first started tech diving I was told (by a wise old man who taught Moses to dive) that:-
1) dive long enough and you will get bent
2) dive long enough and you will have friends who die diving
3) diving is expensive - if you cant afford the toys needed to do it safely dont do it.

Over the years his words have proven correct.


So my conclusion is....

dive long enough and you WILL get bent.

Its just a matter of when.

Every dive to some degree is a roll of the dice.

The models are just that - models. A model might not model you well on the day you get bent

You do the best you can with whats available (model wise) to you to mitigate the risks - but the risk will not fully go away even with a perfect model there will always be a risk that on that day on that dive you dont physically fit the model or your dive profile/actions/gases etc dont.


So what can you do?

Dive conservatively. Use a model that has the most validation. Cross check your deco schedule with other algos. Dont be in a rush to get out of the water. .... Or take up golf

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

Drmike

Can you PM me some details Id like to look into this NAUTILUS

Cheers
Mike

__________________
Cave diving is a sport
Wreck diving is a sport
Diving in general is a sport

'Rebreather diving' is not a sport
its the delusional obsession with a highly dangerous and often inappropriate piece of equipment

abowie

Not wanting to be rude at all, but I think that you're missing the point somewhat.

Deco algorithms are all MADE UP. They are theoretical models, no more than that. Most of them work most of the time but in a practical sense there's never going to be a better way short of measuring the diver's tissue PN2/PHe in real time. Divers who believe that one model is "proven" to be safer than another, or that "tweaking" their algorithm is making their diving safer are simlpy deluding themselves.

People getting bent are just running into the inevitability of the laws of statistics. That is not going to change.

The only to be sure of not getting bent is to never go diving. If you must go diving, then coming up slowly and doing longer deco hangs is likely to decrease your statistical likelyhood of getting bent by some degree.

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Andrew Bowie

Rebreather-friendly Buddy