Deep Stops Increases DCS

[tomfcrist]

I personally wont use ratio deco. Too much mental math, too many opportunities for error.

That being said, Deep stops for the right amount of time, combined with the right amount of deco on the shallow end is very effective. Over staying any of those stops can really **** up your overall deco efficiency.

I cut RGBM tables, which do absolutely start deco earlier than either Buhlmann or VPM on the profiles I dive. I don't get bent.

The premise that deep stops are invalid based on a study that 1) Had significantly overstayed deco stops(these folks started ongassing at most of them) 2)Didn't utilize best practices of current decompression diving( ie: O2 deco) is ridiculous.

This study only proved that folks get bent more often on experimental dive profiles on AIR.

 

[LiteHedded]

i think you all could benefit from reading all of dr. doolette's responses to questions like these about the methodology in that big thread on rebreather world.
he was good enough to spend a lot of time explaining the study there.

 

[flots am]

No HANNIBAL!!! --C'mon!

The same thing -Rato Deco Method- that has been working well for the past five years, even with Deep Air --but now coming down with four type I Right Upper Arm/Shoulder episodes in the past year. . .!

Just have to extend my O2 6m stop profiles from now on, and I hope that's the answer.

Seriously? Four hits and you're still using it?

Whatever magic made RD work for you before doesn't work now.

I'd be changing to something more predictable and controllable (and adjustable).

flots.

 

[Divetech99]

i think you all could benefit from reading all of dr. doolette's responses to questions like these about the methodology in that big thread on rebreather world.
he was good enough to spend a lot of time explaining the study there.

Is this the thread:

http://www.rebreatherworld.com/showthread.php?t=48083

I did a search for Doolette and several popped out.

 

[LiteHedded]

Is this the thread:

Deep Stops (rebreather dive charts) - Rebreather World

I did a search for Doolette and several popped out.

i believe it's this one: Deep stops debate (split from ascent rate thread) - Rebreather World

 

[tomfcrist]

I think it would be more worth while for a study that not only doesn't deliberately overshoot deco times, but also uses accelerated deco. Do the same study using 50% and O2 for deco and lets look at the numbers. The only thing that the NEDU study concluded was: "The practical conclusion of this study is that controlling bubble formation in fast compartments with deep stops is unwarranted for air decompression dives."

If you really think the study was conducted via any valid model that any of us actually use, look at the DCS incidence rate for the shallow stops dive....its 1.5%. How many of us on here with lets say at least 500 deco dives have been bent 7 or 8 times?.....I didn't think so.

 

[PfcAJ]

Read the stuff from Doolette and Mitchell. It's clear you haven't done that.

 

[tomfcrist]

Read the stuff from Doolette and Mitchell. It's clear you haven't done that.

I have read it. And I have read the findings of the study.

What you fail to realize is that the algorithm or tables or whatever it is that you use to do your deco....is most likely a "deep stop" model.

 

[PfcAJ]

I've been moving my low gradient factors higher and higher, and totally moved away from VPM based on personal recommendations from some decompression scientist friends of mine.

 

[Diver0001]

Kevrumbo, thank you for sharing the article in post #36. Quite interesting and compelling. The link does not mention the date it was written. Do you know if this article was written before or after the NEDU study?

Before. And before most hard-core technical divers started backing away from RGBM based on a series of nearly fatal accidents. Accidents that Wienke blamed on computer programmers in order to limit his personal liability and protect his cash cow.

What is generally accepted as fact now in technical circles is that as the dive gets more extreme there seems to be a major problem with the assumption that deep stops save time shallow. Obviously, and intuitively, controlling bubbles is good. Like wise, obviously, and intuitively gas wash out is good. I don't know how many other people actually took the time to read the article but let me summarize this article in one sentence for you.

In the competing priorities of gas wash out vs. bubble control. Gas wash out wins when deco times are kept the same.

If you do *both*, however... well... they didn't test that.

R..