UTD Decompression profile study results published

[Kevrumbo]

Except that the profile you've typed out above also bears no resemblance to the UTD profile in the video... You can't just hand wave away the additional deep stops, the wild s-curving, the entire 9m stop on backgas (!) and claim that they are comparable. That's like saying an elephant is the same as a petunia, if you ignore that one of them is an animal and one a plant, one is huge the other small etc etc...

Why not? Hypothetically, that's what the GUE version of RD did (substitute modified slowing ascent rates rather than "hard" deepstops), while UTD chose to retain the mandatory deepstops at 75% and 50% of max or average depth.

All I'm proposing is what if you consider eliminating the deepstops and the S-curve of UTD's RD and simply compare it with the 50% and 100% O2 times of GUE's version of RD -it is my contention that they will both evaluate to be similar profile shape and time schedules. The implication being in order to "fix" UTD's version of RD, it would have to be something like a modified slowing ascent rate like GUE's RD (and that's assuming if Ratio Deco as an applied bubble model decompression strategy is still viable at all vis-a-vis the NEDU Study).

 

[huwporter]

So what you are saying is; if you threw away all the lucky rabbits foot-ery of the UTD profile it would look totally different? Yeah, sure I can agree with that...

 

[Dr Simon Mitchell]

One more thing Doc. What exactly do we mean by the above? (The differences in inflammatory marker production were statistically significant, but the difference in the proportion of divers producing high bubble grades was not)

Hello,

As previously stated, there was a relatively small difference in the proportion of divers producing high bubble grades between the profiles (slightly more in the ratio deco decompression). However, the statistical testing showed that we cannot be sufficiently confident that this difference did not occur by chance to draw any firm conclusions. This does not mean that the difference is not real; just that we cannot be sufficiently confident that it is real to wave our hands about it. If the same difference was shown in a larger study (more subjects) then this would reduce the probability of the result having occurred by chance.

In contrast, the differences between profiles in inflammatory markers was large enough that even given the relatively small study there is a low probability that the result occurred by chance and we can have confidence that it is real. That is (loosely), the result meets the criteria for being considered "statistically significant". In a previous post I alluded to the fact that we are not certain of the true pathophysiological significance of higher levels of inflammatory markers, but it is reasonable to conclude that it is better to have lower levels than higher levels.

Simon M

 

[Remy B.]

The video is from 2014, were more test done in 2015 and 16 ?

 

[Dr Simon Mitchell]

The video is from 2014, were more test done in 2015 and 16 ?

Not that I am aware of Remy.

Simon

 

[decompression]

Not that I am aware of Remy.

Simon

Hey Simon, thanks for all your posts, always informative. The information that was acquired during the research in Italy and from feedback of other divers diving RD after that contributed to Ratio Deco 2.0, which was released last summer.

 

[CAPTAIN SINBAD]

Hey Simon, thanks for all your posts, always informative. The information that was acquired during the research in Italy and from feedback of other divers diving RD after that contributed to Ratio Deco 2.0, which was released last summer.

After this research, there are two ways that we can proceed. The first would be to acknowledge that Ratio Deco is not the optimal way of doing decompression and therefore has serious short comings. Computer generated profiles (either through Multi-deco / V planner or technical dive computers) are a more reasonable way to proceed.

The second is to acknowledge that Ratio Deco has its flaws so let us all develop Ratio Deco 2.0!!!

By the end of the day we have to think in terms of cost vs benefit and why we are doing what we are doing. I have a lot of respect for UTD but I would like to know how Ratio Deco version 7.0 would be more useful than Buhlmann profile with gradient factors?

 

[Diver0001]

By the end of the day we have to think in terms of cost vs benefit and why we are doing what we are doing. I have a lot of respect for UTD but I would like to know how Ratio Deco version 7.0 would be more useful than Buhlmann profile with gradient factors?

It probably wouldn't be. The use of ratio deco was never about the algorithm in DIR. It was a practicality.

When DIR became "a thing" there were literally no good computers for technical diving. Ratio deco became popular among DIR divers as a result. I think there has been a sense for a long time that it wasn't optimal but DIR is subject, due I believe in part to the highly aggressive manner in which it was first introduced, to a significant degree of "paradigm lock". Early on, any suggestion that DIR was not perfect was met with fierce, brazen and highly argumentative (to the point of being verbally violent) resistance. People were made to be afraid to rock the boat and it has lead to the system becoming static. People were badgered into learning the system by rote, not to question it.

Although these attitudes have softened a lot over the years, the paradigm lock is still a legacy issue, the way I see it.

Going back in time, the need for ratio deco seemed logical when it first emerged. Up until about 2004/2005 there weren't any decent computers for technical diving and even the tek computers being made at that time were of questionable quality. In the intervening time computers have become much better and our understanding of deco theory has taken some steps forward. You would think that DIR as a statement of "best practices" would develop along with that but due to the paradigm lock it does not appear to be keeping pace.

What I would expect to see happen now is that ratio deco will not develop further but will be defended in a similar kind of way that VPM-B has been defended by some people who are also stuck in a paradigm and unable to develop further.

R..

 

[atdotde]

Never having received any formal training in ratio deco (or deco on the fly or whatever you might want to call it), I am a bit surprised that there can be a difference between ratio deco and something you compute with your favorite model: I was under the impression that ratio deco is not thought to be a "model" in itself but rather a mnemonic to memorize plans you compute with another model (plus small variations in depth and/or bottom time). I.e. you first compute plans in your model and then come up with simple to memorize (and reproduce in your head) ways to reproduce that plan.

This, I would have thought, would work with any underlying model (be it VPM-B or your personal favorite choice of gradient factors): You plan your dive on a computer and then memorize the plan (plus what you have to change if you go 3m deeper or stay 3min longer). But apparently at least this is not what UTD do (they seem to have RD rules that do not directly refer to an underlying model).

Let me end this with a shameless self plug: In our Theoretical Diver blog, Rick has recently written a post comparing ratio deco to profiles computed using models: Ratio Deco – is it nonsense?

 

[cathal]

The information that was acquired during the research in Italy and from feedback of other divers diving RD after that contributed to Ratio Deco 2.0, which was released last summer.

Can I ask has formal testing of Ratio Deco 2.0 been conducted to establish its efficacy. If so has the testing shown it to be more effective or less effective than Buhlmans.

Rgds

Cathal