Differences Between UTD and GUE

[Dave1981]

This was our third day of diving similar profiles. On the previous days, we did some very shallow dives (like 30-50 feet afterwards), and on the last day we only did the one dive.

2 Days of 'in-water recompression' followed by the 3rd day where you actually increased altitude after the dive.

Just a thought.

 

[rjack321]

John, can you provide a source for the "proof" or "explaination" or whatever you are referring to that "tell what is wrong with Bulmann and why a Buhlmann profile is not followed"? Is this someones opinion, or is it backed up by scientific assumptions and testing and backed by peer consensus? I've read a bit on deco models, and what they are trying to model (and that is the key-they are only models, not exact estimators of the human body), and have seen how some take certain things other don't as more important, but never seen a proof that any one model was "wrong".

Buhlmann never considered bubbles, its a dissolved phase model only. They exist on every dive but he chose to ignore them because he couldn't figure out how to model them. Hence he's "wrong", the model is known not to match physiology, as just about any diver exiting from just about any profile has some at least minimal doppler bubble score (which is coarsely related to DCS symptoms itself).

The addition of gradient factors to Buhlmann is a mathematical kludge intended to compensate for inevitable bubbling. But these are just guesstimates, GFs themselves do not represent bubbles in any way.

However despite the mismatch between being a pure dissolved phase model and being "wrong" about the reality of bubbles, Buhlmann (with or without GFs) is still a reasonably good predictor of lots of other things. All models are "wrong" although most have some utility anyway - depending on whatever question you're asking of the model of course.

 

[Waterskier1]

Richard,

Thank you for this explanation. I knew that Buhlmann didn't consider bubbles, but I was incorrect in thinking that was because his model strives to reduce them to zero. That is, that if you followed his model correctly, you would never get bubbles. I did not know that he didn't discuss the bubbles because he had no way of modeling them. I do understand that all of these are only models - that there is no "formula" that explains it scientifically.

My concern (and I have not taken a GUE or UTD class yet) is that UTD seems to base their model on how divers "feel" after exiting (or possibly while still decompressing in) the water. But, I don't see a formal, closed-loop system of obtaining this information. Maybe some of the instructors or other major players might contribute, but I would think that every experience should be included in the population for ongoing study.

From what I understand, UTD's ration deco attempts to have you exit the water "clean". If this is truly the case, then maybe altitude in not a factor. I wonder if it really is "clean" enough to drive up over 1000-ft in less than 30 minutes, and over 5000-ft in a few hours. This is in addition to the dive being conducted at altitude.

 

[LiteHedded]

it's all voodoo and witchcraft.

 

[Blackwood]

... UTD seems to base their model on how divers "feel" after exiting

Heh. What version of the ratio deco docs do you have? Mine are based on decoplanner.

 

[Waterskier1]

Heh. What version of the ratio deco docs do you have? Mine are based on decoplanner.

I have 2005 version I downloaded from 5thd-x.com before they moved their stuff to unifiedteamdiving.com. I'm not sure if it's the most current version, but my comment was really addressing comments in this forum. I am not an expert on ratio-deco, or any of the software packages. Maybe I am wrong?

 

[TSandM]

Well, our own Rick Murchison has a wonderful way of putting it: Every staged decompression dive you do is really an experiment you are doing using your own body; take careful notes.

NONE of the models actually models what's happening in the human body. ALL models try to predict what is "safe", with some frequency of DCS being considered acceptable. (No model can exclude it completely.) One of the things Andrew stresses is that you begin with what the model gives you, but you must adjust according to the feedback you get from your body. If diving what a given model lays out means you feel like you have the flu by evening, you probably need to do more deco.

NO decompression strategy is going to get you out of the water "clean", if by "clean", you mean having no more nitrogen in your tissues than you had before you dove. We just don't stay in the water long enough to do that. But spending time on high oxygen mixes underwater can definitely make significant inroads on the tissue loading. If I remember correctly, the studies DAN did on flying after diving showed that technical divers could fly quite a bit earlier than recreational divers could, without developing DCS symptoms, and I suspect this is due to accelerated decompression, and that is what both GUE and UTD teach.

 

[ucfdiver]

is that UTD seems to base their model on how divers "feel" after exiting

I would hope that ANY decompression strategy involves analyzing your body's physical feedback. There's a line between "too long", where you unnecessarily increase deco and add to rock bottom as well as your hard ascent ceiling, as well as "too short" where you're bent. Padding deco is one way to stay safe, but nothing is as good as knowing what works for you, especially if an emergency happens and you need to get out of the water as quickly as (safely) possible.

UTD materials seem to focus on identifying sub clinical DCS symptoms more than other materials I've seen, if that's what you meant.

 

[lamont]

From what I understand, UTD's ration deco attempts to have you exit the water "clean". If this is truly the case, then maybe altitude in not a factor. I wonder if it really is "clean" enough to drive up over 1000-ft in less than 30 minutes, and over 5000-ft in a few hours. This is in addition to the dive being conducted at altitude.

Buhlmann models are "wrong" in the sense that they don't model bubbles, but that doesn't mean that the dissolved phase model is wrong. In fact, all of the existing "bubble models" are really dual-phase models with a bubble model sitting on top of a dissolved phase model which looks quite a bit like what Buhlmann was using.

Ignoring the dissolved phase component of altitude diving, entirely, is kind of like claiming that Einstein proved Newtonian gravity to be "wrong" and jumping off the top of your house thinking you can fly...

 

[rjack321]

I have 2005 version I downloaded from 5thd-x.com before they moved their stuff to unifiedteamdiving.com. I'm not sure if it's the most current version, but my comment was really addressing comments in this forum. I am not an expert on ratio-deco, or any of the software packages. Maybe I am wrong?

Biggest changes:
the 2:1 setpoint moved from 220ft up to 200ft (more conservative)

deco with 25/25 & O2 in the 100-130ft range now can use the "time over MDL" method with a backgas fibonacci sequence and then a time credit for the O2 OR the 1:1 150ft setpoint. Half the time on O2 and half the time shaped exponential below 20ft. They end up being pretty much the same profile. UTD Tech1 teaches 1:1 in the 100-130ft range while Tech2 extends this to the 160ft range

deco for <100ft dives still needs to use the "time over MDL" method as its too far away from the 1:1 setpoint.

Starting at roughly the 3:1 range there's now such a thing called "cascade deco" where you're BT establishes the O2 time (via a ratio) and then all the deco gases below that are proportional to the O2 time.