My Journey into UTD Ratio Deco

[Kevrumbo]

There is divergence at the edges of the tech1 limits as well. Not huge but it begins to get less conservative than the tables before you over run their max deco times.

Comparing Bühlmann GF 30/85 and RD 2.0 for a 25min BT at 48msw/160fsw with 18/45 bottom gas and one 11L/AL80 deco cylinder of Eanx50 (max depth UTD Tech 1 limits), a "divergence" I potentially see is a more conservative five minutes of deepstops with RD 2.0 starting at 33msw/110fsw (1,1,1,2 =>total deepstop time 5min) before the deco gas switch at 21msw/70fsw to Eanx50, versus a one minute deepstop at 24msw/80fsw for GF 30/85.

Another slight difference is the Eanx50 deco profile times: From 21msw switch depth to 9msw, RD 2.0 looks something like 2,2,3,4,4 =>total segment time 15min; while GF 30/85 is 1,1,1,3,4 => total segment time 10min. From 6msw, RD 2.0 shows 15min plus a slow 1mpm ascent to surface for a total segment time of 21min, while GF 30/85 has 6min at 6msw and finally 14min at 3msw for a total segment time of 20min.

Total Deco Time: RD 2.0=>41min; Bühlmann GF 30/85=>31min;
Total Run Time: RD 2.0=>68min; Bühlmann GF 30/85=>60min.

RD 2.0 is actually more conservative than Bühlmann GF 30/85 because of those deeper/longer deepstops, but may be also a less efficient deco profile with respect to the slow/intermediate tissues -especially if you choose to implement it over a series of consecutive days of multiple mandatory staged deco-dives-per-day. . .

 

[PfcAJ]

RD 2.0 is actually more conservative than Bühlmann GF 30/85 because of those deeper/longer deepstops, but may be also a less efficient deco profile with respect to the slow/intermediate tissues -especially if you choose to implement it over a series of consecutive days of multiple mandatory staged deco-dives-per-day. . .

You’re kidding right?

 

[Kevrumbo]

You’re kidding right?

Ratio Deco is about protecting the fast tissues as well with deepstops, so compared to a Bühlmann GF 30/85 which RD originally claimed "similarity" to, in this instance Ratio Deco is more conservative.

I didn't say it was necessarily more efficient . . . (y'all savvy?)

 

[PfcAJ]

Ratio Deco is about protecting the fast tissues as well with deepstops, so compared to a Bühlmann GF 30/85 which RD originally claimed "similarity" to, in this instance Ratio Deco is more conservative.

I didn't say it was necessarily more efficient . . . (y'all savvy?)

Yup. Not joking.

Wow.

 

[JohnnyC]

The Spisni study just flat out proved that "time in water" does not mean "more conservative."

That's literally exactly what that study proved (among other things).

 

[Kevrumbo]

The Spisni study just flat out proved that "time in water" does not mean "more conservative."

That's literally exactly what that study proved (among other things).

No @JohnnyC , the above is an entirely conflating qualitative misinterpretation.

Ratio Deco attempts to protect and limit supersaturation and potential bubble formation in the fast tissues early in the deco profile with deeper/longer deepstops; in contrast Bühlmann dissolved gas model aggressively approaches these fast tissue M value tensions or optionally moderates them with Gradient Factors, but still not as radically deep or as long as a RD Deepstop(s).

However with regards to later slow/intermediate tissue surfacing supersaturation, in my opinion/experience, RD users have to practically extend their shallower O2 stops by some greater amount in order to effectively clear those tissues -which therefore makes RD more conservative and a much longer total deco runtime compared to a Bühlmann GF profile... (i.e. If you believe in protecting the fast tissues as well as effectively washing out the slow tissues later in the decompression profile, then you are taking a qualitative "conservative" approach with "more deco time" in the water per RD).

Objectively with regards to the Spisni Study:

. . .Despite having a longer decompression the ratio deco profile was associated with greater production of inflammatory markers after the dive. The ratio deco profile produced grade 3 or 4 bubbles in 4/28 (14.3%) divers and the GF profile produced grade 3 or 4 bubbles in 2/23 (8.7%) divers. The differences in inflammatory marker production were statistically significant, but the difference in the proportion of divers producing high bubble grades was not.

The ratio decompression profile puts greater emphasis on deep stops in comparison to the GF profile, and the results constitute further evidence that the "love affair" we had with deep stops in the early 2000s has resulted in over-emphasis of the strategy by some algorithms. For clarity, and to avoid misinterpretation, the study does not establish GF 30:85 as optimal decompression. It simply indicates an advantage for that algorithm over one which places more emphasis on deep stops.

Simon M

Again, with regards to the NEDU Deepstops Study, it is apparent that Ratio Deco as implemented with deepstops is not as efficient a deco algorithm compared to one such as a Bühlmann GF dissolved gas model for the same total amount of decompression time. . .

 

[JohnnyC]

Except that even with RD's arbitrary extended shallow stops, the participants in the study showed more decompression stress, which blows the idea out of the water that UTD's version of ratio deco is A) more efficient, and B) more conservative.

You sound like Ross arguing what the word efficient means. If the RD users in the study exited the water with less decompression stress, you could make an argument that it is more conservative, although they still tomfooleried their plans so you can't actually argue that comparison anway. Yet even with that "I'ma pull this profile outta my ass" extra time in the water, they STILL had more decompression stress. That is not "more conservative" in any way whatsoever. Extrapolating, I could extend shallow stops by the same amount as the UTD profiles on a Buhlmann profile and exit the water with less decompression stress than the UTD profile. Which would again demonstrate that RD is not as conservative.

 

[Kevrumbo]

Except that even with RD's arbitrary extended shallow stops, the participants in the study showed more decompression stress, which blows the idea out of the water that UTD's version of ratio deco is A) more efficient, and B) more conservative.

No @JohnnyC , the Spisni Study blew AG's own expectations "out of the water" and implied to an extent that A) & B) above are actually mutually exclusive.

You sound like Ross arguing what the word efficient means. If the RD users in the study exited the water with less decompression stress, you could make an argument that it is more conservative, although they still tomfooleried their plans so you can't actually argue that comparison anway. Yet even with that "I'ma pull this profile outta my ass" extra time in the water, they STILL had more decompression stress. That is not "more conservative" in any way whatsoever. Extrapolating, I could extend shallow stops by the same amount as the UTD profiles on a Buhlmann profile and exit the water with less decompression stress than the UTD profile. Which would again demonstrate that RD is not as conservative.

The point is again if you believe in "conservatively" protecting your Fast Tissues with deepstops as per RD (or ostensibly by choice with a low value GFLo like 20 or 30 in Bühlmann Gradient Factors) WITHOUT compensating "conservatively" enough in the profile to account for the resultant Slow Tissue on-gassing and later surfacing supersaturation, then you might have a "Robbing Peter to Pay Paul" dilemma with potential significant VGE and/or inflammatory marker deco stress evolving from the Slow Tissues (reference this dialogue a few years ago at Deep Stops Increases DCS ).

Extrapolating it out even further, given a 11L/AL80 O2 cylinder supply, you can eventually do as much shallow Oxygen decompression as needed to clear slow tissues of surfacing inert gas supersaturating tensions such that it doesn't matter what amount of RD Deepstops or GFLo value you did earlier to load those tissues -this understandably is the ultimate in "conservatism" and "efficacy", but obviously not in "efficiency".

 

[Dan_P]

Okay guys, let me just start by saying that this is - obviously - a string about Ratio Deco.

When it starts becoming about Andrew Georgitsis, Z-System, MX/MX-Z Rebreather Configuration or whichever other unrelated topic that has zero relevance other than the underlaying correlation that it has to do with UTD, that reduces the conversational value.

I don't mean to say that if the conversational value is respected by all participants regardless of opinion, we'll all agree to use Ratio Deco - rather, I mean to say that we'll all be better equipped to understand why those who use it, choose to do so, and better equipped to understand why those who do not, choose not to.

If the exchange of ideas is not the aim of participating in a conversation, then there is no aim of said participation.

That said, I could sit here and argue all day long about whether a vBlog expressing expectations in the heat of a moment, is a good basis for deciding that anyone who uses Ratio Deco must be a personal-cultist or dismissive of science.
Or I could argue that the discussion in general would benefit from much less ultimative language and discipline in the perception across the use and meaning of scientific phrasing.
Or that if one states with certainty a matter to be fact, one would do well to actually be certain.

I'll rather just say instead I'm personally a content user of Ratio Deco, and also a relatively frequent defender against unreasonable attacks against it, but I don't mind asking questions. Nor give credit where it's due.

You'll see me discussing with some passion (by Scandinavian measure) the degree to which we can attribute confidence in various studies' results, or how their relevance may be applied, to better understand utility of a scientific discovery, with leading experts in related scientific fields (fortunately some such make themselves available to such discussions) - I mean in particular @Dr Simon Mitchell - and in the next breath make reference to work they've published in a different discussion, applauding their contribution.

Let's try to argue the point on this one, and choose to establish or maintain a tradition of refined debate to better understand matters that will very likely require a collective effort to explore further, anyway.

 

[kensuf]

if this isn't DIR, then what is? AG is the biggest voice of DIR right now. UTD and ISE are the only ones actually calling their diving DIR. Now, I do understand your WKPP argument, and I also understand why JJ stopped using the term, but if UTD and ISE are promoting ratio deco, and promoting DIR, then that is to me more "DIR" than anything that GUE is doing right now. Unfortunate, but annoyingly true.

I'm late to the party. The contraption that's the UTD Z-Manifold is the exact opposite of DIR. It adds complexity and failure points to sidemount that do not need to be there.

Anyone that thinks a group that endorses the Z manifold as a "DIR solution to a fundamental skills problem" don't really understand what DIR is all about.