Is UTD still a "fringe" organization?

[rjack321]

When did AG leave UTD, and why?

He has frequently sold his share of companies he started. None of them are publicly traded to my knowledge but after a decade or so he usually gets out.
Sold his share in DiveXtras
Sold his share in Red Sea Explorer
Sold his share in UTD

He's a starter not a finisher. Moving on from UTD is not a shock to me

 

[StefinSB]

Statistics. A curve where you plot the instances of DCS against time (for that profile) then select the point where it is 'n' standard deviations from the norm.

Rjack answered. You obviously have nothing to add.

 

[boulderjohn]

Is there any hard scientific evidence that such stops offer a superior decompression in general than a computer generated, 3 minutes @ 20 feet? Not at this point but, in the absence of any hard scientific study certain scenarios may be more likely than the others. Adopting them does does not make you less scientific or more scientific. It just shows that you are making decisions in a territory where science has not reached yet. This is why we use the term decompression "theory."

Decompression theory for NDL dives has been studied for over 100 years, and countless divers were tested in coming up with the standard NDL dive profiles used today.That approach is enormously successful--only about 0.02% of dives end in DCS. So it makes sense to you to try a "what the hell, let's do something different and see if we like it" approach? You call it a "thoughtful" approach to throw out all that research and do something instead that has never been tested.

By the way, this debate is really about a hundred years old. Haldane liked the staged ascent approach; others liked a continuous ascent approach? While the UTD approach is technically staged, it is closer to continuous.

 

[helodriver87]

This is one of the reasons UTD is still fairly fringe. Ratio deco is very much a ballpark guess best suited for the backup to your backup plan. GUE still teaches a version of it, but it's secondary to tables (and realistically, tertiary with the general acceptance of computers across the community). The ascent technique taught in fundies is geared more towards building proficiency for T1 than actual deco efficiency, even though its roots may still be based on outdated deco research. Relying on ratio deco is like choosing to navigate by the stars. You can manage ok if you really know what you're doing, but there are better, easier, more accurate ways.

 

[ginti]

GUE does pretty much the same. When I reached out to GUE headquarters and asked for an explanation, the person responding said that this is because of their belief that divers should ascend more slowly when getting closer to the surface. They chose 50% because it is easy to compute, and they chose the intervals because they are consistent with practice on decompression dives.

I never discussed this point with anyone, but it's my personal opinion that it has to do with the pressure gradient. The shallower you are, the higher the pressure gradient relative to a fixed change of depth. For example, if you move at 10m/min (30ft/min) from 40m (130ft) to 30m (100ft), you are reducing the pressure from 50bar to 40bar in 1minute, which is a reduction of 20%. Do that from 15m (45ft) to 5m (15ft) and the pressure is reducing from 2.5bar to 1.5bar in the same amount of time, which is a reduction of 40%!

Being the pressure gradient one of the key factors in decompression strategies, it makes sense to plan the ascent so as to never surpass some critical levels - which is why I think GUE breaks the ascent into two different phases (it's just the easiest way to do it)

I guess most of you already knew these simple facts, but it is worth underlining it I guess, especially for newer divers

No, not at all. According to the data I remember seeing, out of total number of decompression hits, the ones that happened inside NDL were significant. I do not recall the exact number of these hits but it was quite high.

I am really surprised to hear this, and I'd like to understand more - so I have two questions:
1) What does "significant" mean for you?
2) I couldn't find any study online concluding that the percentage of divers getting DCS is relevant, but maybe I am just not as good as I want to believe in internet research Could you send us a link to this study?

When we are diving here in North Carolina the wrecks are often deeper than 100'. More than half the boat always crashes and falls asleep on the way back. Energy levels on a North Carolina deep charter are drastically different than on a Florida Keys dive charter where we dive a 30 ft reef. Bottom times for the Florida dives are always twice or thrice as long as the 20 minutes on U-352 but collective energy levels on the boat are always different. Why? Because in NC, people get bent. They do not know that they are bent because their computers are showing them clean but they cant walk straight. They attribute their fatigue to exertion they never did and their loss of balance to sea conditions that could be flat as a pool.
....

Being tired is a symptom of DCS. But being tired does not mean having DCS...

 

[KevinNM]

The GUE non-stop ascent is actually 3 phases. Fast to 50%, then 10 feet per minute to 10 feet, then as slow as practical to the surface from 10 feet.

 

[Wibble]

Rjack answered. You obviously have nothing to add.

I answered in reading order to your specific question.
Your replies do seem rather aggressive

 

[AfterDark]

IMO it is fringe because they don't allow for solo diving but that's just me.

 

[kensuf]

We can't completely discount the fact that the NC wreck divers probably awoke before dawn, drove some distance to the dive shop, brought and loaded their own tanks, and had a 3-hour ride out to the wrecks, while in the Florida Keys the divers woke up, had a nice breakfast at the diner, hopped aboard the boat and sat down next to their rental tanks. It's hard to attribute drowsiness on the 3-hour ride back from the NC wrecks entirely to so-called subclinical DCS. I wouldn't doubt that it's a factor, though.

Add mild hypothermia with the subsequent caloric expenditure and dehydration from diving (breathing compressed air dries you out), plus sun on the boat and I'm ready to take a nap just thinking about it.

 

[CAPTAIN SINBAD]

Decompression theory for NDL dives has been studied for over 100 years, and countless divers were tested in coming up with the standard NDL dive profiles used today. That approach is enormously successful--only about 0.02% of dives end in DCS. So it makes sense to you to try a "what the hell, let's do something different and see if we like it" approach? You call it a "thoughtful" approach to throw out all that research and do something instead that has never been tested.

By the way, this debate is really about a hundred years old. Haldane liked the staged ascent approach; others liked a continuous ascent approach? While the UTD approach is technically staged, it is closer to continuous.

To reiterate my earlier point, Doppler technology found bubbles running inside in each and every one of us. The most important statistic to start with is that 100% of people who dive are bent. If there is anything that we can say with Doppler certainty it is the fact that everyone is bent.

"This (discovery of bubbles in divers within NDL) provides a significant challenge to the traditional view of decompression theory. If bubbles are formed well within our M-Value limit then what use are M-Values? And if bubbles form, and yet there are no signs or symptoms of decompression sickness then how can we say that bubble formation causes decompression sickness?" (Mark Powell, Deco for Divers page 110)

How do you determine where the NDL is when bubbles have started to form so much earlier than established NDL limits and the point at which silent bubbles become symptomatic varies so much for person to person? For reference purposes, here are NDL limits for a 100ft dive on various dive tables ...

Buhlmann ZHL-16 B (PSAI) - 16 mins
US Navy Table (SSI) - 20 mins
RGBM (NAUI) - 22 mins
NOAA - 25 mins

We can see the dilemma that a decompression modeler has. All of the above tables have been used quite extensively with safety levels that are still acceptable today. The guy who is diving on NOAA table may get bent 23 minutes into the dive, have severe headache that knocks him out and, on his table it is an "undeserved hit" but you could pull out the Buhlmann table and say, "No you were 7 minutes into decompression according to Buhlmann so you deserved it." This is why DAN writes the following:

"Many divers are also unaware of the fact that dive computers make use of many different mathematical models, or versions of different models; there is no universal standard. A single manufacturer may use more than one model, possibly in a single type of computer. This makes it extremely difficult to assess the nuances of every system." (Dan.org > Decompression Sickness, Chapter 2: Effective Use of Dive Computers)

UTD trains divers to treat every dive as a decompression dive. As for the half stops, I have also found details of the study that DAN did to come up with their deeper stop recommendations for recreational diving. I will try to post it later during the weekend. It gives some validity to UTD's approach.

Had my vaccine so I have my own symptoms right now that are not that different from DCS.