Slow tissue on gas from stops

[PfcAJ]

This whole thing is so typical of UTD deco discussions. Constant moving of the goalposts by the UTD guys.

Predictable.

 

[Dan_P]

What does this mean?

It means that if we arbitrarily add more time with a distribution pattern (particularly one that overemphasised deep stops), there should be some point when adding more time will do relatively less "positive effect", minute-for-minute, than the first minute did.
That's why we can't say that the last, arbitrary, minute added, would be as "effective" (by a given metric) as the first one.
We would rather assume qualitative alinearity.
That is, if we add more time arbitrarily with the same distribution pattern, it may be increasingly less effective.

A distribution pattern-style methodology is not designed to autonomously distribute time beyond what's integrated in the framework it represents.
That's forcing the logic of an algorithm on something that isn't one.
If one wants to arbitrarily add time, one has to do it oneself.

That's why I say that we can't arbitrarily add time to RD and directly carry over the results of that to a normative measure on how RD would perform. Hence, a universal "RD is 44% less effective than GF30/85" can't expectably be said to hold true, given what we have.

Same runtime as what? The 'Gold Standard UTD-RD' profile that should have been tested? Or the *UTD-RD* profile that was tested?

Same runtime as what it's being compared to. I'd imagine it'd be a reasonable wish, but only for the sake of good order.

I suppose you need to define what 'less effective' means. In the study the end point was markers of decompression stress. Clearly the tested *UTD-RD* profile was less effective (even though granted more time) than the GF30/85 profile based on the test criteria.

It's not about the measure of effectiveness, or about whether one was more effective than another (I should reiterate that I don't disagree with you about that part) - it's about adding arbitrary time to a framework, and then draw the conclusion that the result of that arbitrary time would automatically be identical within the original framework itself.

That would assume a qualitative linearity beyond a certain point, and whatever that point may be, we cannot say that this is a reasonable assumtion to make.

Also, can you share the 'Gold Standard UTD-RD' 1.0 and 2.0 profiles for the 50m 25 min dive with the gases used in the test? How different is it from what AG/BB seemed to think was UTD-RD?

Firstly, you're again endeavouring a very serious misrepresentation by implying that I'm in disagreement with Andrew or Ben because the trial designer called for more time on the RD-sample.

Secondly, do you seriously think that in setting up the dive parametres, Spisni et alia told the RD-samplists to spend as much time as they felt like, or would accept to give more deco time because someone would love to have it?

Thirdly, I don't know why there was more time, neither do you, but we can agree it's a design flaw. Assuming a position that it must be because that's what the guys wanted, is just your assumption - and my assumption is that's incorrect.

This is about RD1.0, and the details were shared above, #261 and #262.

This whole thing is so typical of UTD deco discussions. Constant moving of the goalposts by the UTD guys.

Predictable.

Nah mate, it's just I'm saying we can't state that RD is 44% less effective than GF30/85 with what we have, that's all. Nobody is arguing over whether or not RD1.0 emphasised deep stops too greatly.

 

[UWSojourner]

This is about RD1.0, and the details were shared above, #261 and #262.

Since I don't speak RD-ease, can your translate those into depth/departure time? And if possible put a RD 2.0 profile with it so we can compare what the "fix" did to the stops?

 

[Dan_P]

Since I don't speak RD-ease, can your translate those into depth/departure time? And if possible put a RD 2.0 profile with it so we can compare what the "fix" did to the stops?

RD1.0 you'd have 1 minute at 36m, 33m, 30m, 27m and 2 minutes at 24m.
You'd then have a total of 15 minutes distributed across the 21m-segment and 15 minutes across the 6m-segment.
With the S-curve in RD1.0, it'd be 4 minutes at 21m, 4 minutes at 18m, 2 minutes at 15m, 2 minutes at 12m and 3 minutes at 9m. Then 15 minutes between the 6m and 3m stops.

Please note:
I feel it's necessessary to once again reiterate this:
I'm not saying that running that ascend instead would have made a difference to the study's findings that RD1.0 overemphasised deep stops, but rather that the arbitrarily added time is likely to skew our perception of the impact that the extra time had, compared to the GF30/85
- that's all.
We agree that RD1.0 overemphasised deep stops.


At this point, though, it's not about whether Ratio Deco 1.0 overemphasised deep stops - it's way smaller than that.
It's only about whether arbitrarily added time outside of the standardized distribution pattern of a framework, in a trial, exactly matches the effectiveness - or lack thereof - of the initial framework time itself.
I don't believe we can assume that it does, but in either case, it's hardly anything controversial, really.

But yes, they probably would, but I don't understand why they should have to convert anyone.

 

[Diver0001]

RD1.0 you'd have 1 minute at 36m, 33m, 30m, 27m and 2 minutes at 24m.
You'd then have a total of 15 minutes distributed across the 21m-segment and 15 minutes across the 6m-segment.
With the S-curve in RD1.0, it'd be 4 minutes at 21m, 4 minutes at 18m, 2 minutes at 15m, 2 minutes at 12m and 3 minutes at 9m. Then 15 minutes between the 6m and 3m stops.

Please note:
I feel it's necessessary to once again reiterate this:
I'm not saying that running that ascend instead would have made a difference to the study's findings that RD1.0 overemphasised deep stops, but rather that the arbitrarily added time is likely to skew our perception of the impact that the extra time had, compared to the GF30/85
- that's all.
We agree that RD1.0 overemphasised deep stops.



Nobody's come out and said that anyone has to convert to anything, in fairness

At this point, though, it's not about whether Ratio Deco 1.0 overemphasised deep stops - it's way smaller than that.
It's only about whether arbitrarily added time outside of the standardized distribution pattern of a framework, in a trial, exactly matches the effectiveness - or lack thereof - of the initial framework time itself.
I don't believe we can assume that it does, but in either case, it's hardly anything controversial, really.

But yes, they probably would, but I don't understand why they should have to convert anyone.

Daniel are you willing to come out and suggest/state that RD should be retired at this point? You seem to have a nuanced view of its usefulness and I'm curious about your view as a UTD instructor about holding on to this clearly outdated practice.

R..

 

[tursiops]

The more I read these arguments in favor of RD, the more convinced I am that it has long outlived any usefulness it once may have had, and should be relegated to the category of Vintage Diving, along with red ribbons for depth, J-valves for gas management, Chlorox bottles and Fenzys for buoyancy, unbalanced double-hose regulators, and round high-volume face masks. Sure, it's fun, but serves no purpose other than amusement.

 

[Patoux01]

The more I read these arguments in favor of RD, the more convinced I am that it has long outlived any usefulness it once may have had

The only issue is that people are confusing RD with RD(tm). You can get a pretty good estimate of the dive plan with it without needing to rely everytime on a deco planner, for instance. It also lets you know what deco you should expect when diving (though I've only heard of one brand of computers that seemed to give strange deco times).

It has benefits, as long as you have been smart enough to "make" an RD that fits an algorithm that makes sense.

 

[victorzamora]

The only issue is that people are confusing RD with RD(tm).

I really, really like the paradigm of finding ratios and using them as a way to fit ascent curves generally to the computer-generated plan of your choice. You get all of the on-the-fly flexibility that UTD-RD(tm) has but without the rigidity of being locked into one method of setting the ascent curve/rate/etc.

I don't actually dive RD, I dive my computer....but using Ratio-Estimated Deco (the non-UTD-RD(tm) version) in a generic fashion, I can estimate gas volumes needed, how much deco I'm willing to put up with, etc. It's funny because I found a couple of the ratios that my GUE buddy was taught on my own. He then filled me in on how he was taught RD, and I stole some of those same concepts. The only difference is how we each distribute deco time....but that's just a matter of us running different GFs.

What I have an issue with is the UTD-RD(tm) version ignoring respected/tested algorithms and replacing computer-generated curves with whatever AG mandates. Having talked to UTD-RD(tm) trained folks, there's a right way of doing it and a wrong way. Having talked to GUE-RD trained folks, there's a generic way they're taught as "standard" but that's a baseline for divers to then adapt to their own preferences and needs.

 

[Dan_P]

The more I read these arguments in favor of RD, the more convinced I am that it has long outlived any usefulness it once may have had, and should be relegated to the category of Vintage Diving, along with red ribbons for depth, J-valves for gas management, Chlorox bottles and Fenzys for buoyancy, unbalanced double-hose regulators, and round high-volume face masks. Sure, it's fun, but serves no purpose other than amusement.

The only issue is that people are confusing RD with RD(tm). You can get a pretty good estimate of the dive plan with it without needing to rely everytime on a deco planner, for instance. It also lets you know what deco you should expect when diving (though I've only heard of one brand of computers that seemed to give strange deco times).

It has benefits, as long as you have been smart enough to "make" an RD that fits an algorithm that makes sense.

Daniel are you willing to come out and suggest/state that RD should be retired at this point? You seem to have a nuanced view of its usefulness and I'm curious about your view as a UTD instructor about holding on to this clearly outdated practice.

R..

@Diver0001 thanks for asking!

In principle, I personally think that using relations across depth and time is something that - if done - should be done to make diving more easy/practical in some fashion, or bring about a benefit of some sort, to the diver.
I think if proceeding on that view, it's important to stress that's an implicitly subjective matter.

I believe any "standard deco"-paradigm will always be physiologically suboptimal compared to an "optimal deco"-paradigm, to borrow terms from the standard/optimal gases.
That doesn't mean that the principle of using a "standard deco"-paradigm is defective.
Rather, it means that the user has opted to sacrifice physiologically optimal in favor of some subjective practicality.
I believe that sums up my thoughts on the general idea of using a tool such as Ratio Deco.


As for which practicalities one wishes to have included in the paradigm, I can but offer you a pragmatic's opinion.
From a training- and developing perspective, it is my personal opinion that using a consistant such framework is a truly awesome tool to test and develop student awareness in-water.
On the deck, I know that having such a tool that is consistant across all the diving means a diver can quickly glance at what's available, know what's possible to do with it, and have a full dive plan in place, in seconds.

I personally also wish to encompass an interoperability across O/C and CCR.
That is, all that separates a CCR-diver from an O/C-diver, is the turn of a knob. This has some implications to what the average ppO2 would need to be during ascend, but I'd find it hugely beneficial regardless, in practical terms.
Do I believe that these factors necessarily align with physiological optimization?
Definitely not.

So, to answer your question:
Do I think retirement of "standard deco"-paradigms and Ratio Deco is due?

I think it's extremely important for divers to understand "why" they're doing things they're doing, so they can personally make the choices they need to make, whichever direction they choose. But I don't think a retirement of the Ratio Deco-option is anywhere near due.

As an addendum, I will say that I was initially tech trained by another organization, and also that my personal experience with UTD has in no way resembled anything to the effect of a "cult". I have experienced full disclosure on pro's and con's of things - and I have UTDs standards and procedures fully freeing me to dive and teach by the choices that I make; that is, regardless if I opt for computer or Ratio Deco (2.0).

Finally, to try and consolidate practicality and gradual relative approximation to physiologically optimal, there is going to be a dependency upon scientific input, and, well, time.
As understanding and knowledge advances, gradually, adjustments can be made - I have previously made comparisons with more protocol-related examples, such as buddy breathing.

I personally think that Ratio Deco 2.0 shows adaptation - while one may or may not be impatient with the process, and may or may not like the confidence of individuals in the previous (or current) version, I would assume that more adaptations will present themselves as science delivers increasingly accurate indications as to what constitutes optimal levels.

As for diving organizations adapting to change, I am happy that it didn't take UTD as long to adapt to RD2.0 as it did the mainstream organizations to adapt away from buddy-breathing.

I remain curious about which advances in our collective knowledge are to come, and continue to browse through reference lists for reading material.

 

[Diver0001]

I don't think a retirement of the Ratio Deco-option is anywhere near due.

I see. Personally I think retiring RD is long overdue for similar reasons. Where we strongly agree is that students need to have a keen understanding of deco theory. Where we disagree is in the proposition that RD is the mechanism by which to teach that.

IN addition, teaching RD suggests to the student that they should (or could) USE it, which is highly inadvisable in any context. I personally believe that we should teach students skills in a course that they can apply after that course, not skills that they should avoid applying because they constitute a risk to their safety.

This is why I asked you if you would step back from RD. It is (a) a poor practice by any modern measure (b) inefficient at best and dangerous at worst if applied and (c) far FAR from being a best practice, which we (I believe) would agree should be the focus of training.

So why on earth should we be holding on to that?

R..