Is UTD still a "fringe" organization?

[Wibble]

When I was with UTD, I had several fairly heated arguments with both my instructor and Andrew Georgitsis about our reliance on ratio deco and its deep stop obsession, especially at the altitude (4,600 feet) our UTD group was diving. I was repeatedly told that no one had ever gotten bent using ratio deco, even at that altitude. I said I could name 8 instances in our group alone, incidents resolved using surface oxygen, in-water recompression, or a chamber ride following helicopter evacuation. I was told that those cases did not count because there was always another cause, usually a suspected PFO or other unknown cause. I asked Andrew how he knew that those other things, not ratio deco, had been the cause, and he replied that ratio deco could not have been the cause because no one had ever been bent using ratio deco.

I started a thread on ScubaBoard in which I mentioned how many people had gotten bent in our group, and I received an email from my instructor telling me that if I posted anything like that again, UTD would contact PADI to have me punished--possibly expelled--as an instructor for violating the member standards against disparaging another agency. That was when I left UTD.

What the contemporary political environment refers to as "woke"; believe in what we say or we'll 'cancel' you.

Quite a disgusting story at the root of that.

One of the things I like about diving is it's generally science lead. There's been so many discussions about deep stops being discredited that it's pretty much the consensus.

I say generally science lead as there's still some laggards that won't accept alternative opinions, just like all walks of science.

 

[Wibble]

We all accept that decompression science is not an exact science and that we use statistical models to move a dive "n" standard deviations away from being bent. This (correctly) implies that sometimes "undeserved" bends happen for no apparent reason.



Happened to a 'buddy' of mine last year. We dived a perfectly benign wreck at 33m/110' on rebreathers for about 65 mins on the bottom with 25mins deco; lovely dive, no hassle, peaceful; good ascent, kept the stops and extended them a bit, slow final ascent from 6m/20'. Just a plain lovely dive.

Alas he developed a skin rash and started to feel tired with a headache later on during the drive home. Following a shower the rash grew, so he called the dive doc and ended up doing 5 days of decompression chamber treatments. He is youngish, fit, healthy, relatively experienced diver and does lots of exercise. He's still fit and healthy afterwards, but the diving's had to take a pause.

Just one of those mystery bends.

 

[tursiops]

When I was with UTD, I had several fairly heated arguments with both my instructor and Andrew Georgitsis about our reliance on ratio deco and its deep stop obsession, especially at the altitude (4,600 feet) our UTD group was diving. I was repeatedly told that no one had ever gotten bent using ratio deco, even at that altitude. I said I could name 8 instances in our group alone, incidents resolved using surface oxygen, in-water recompression, or a chamber ride following helicopter evacuation. I was told that those cases did not count because there was always another cause, usually a suspected PFO or other unknown cause. I asked Andrew how he knew that those other things, not ratio deco, had been the cause, and he replied that ratio deco could not have been the cause because no one had ever been bent using ratio deco.

I started a thread on ScubaBoard in which I mentioned how many people had gotten bent in our group, and I received an email from my instructor telling me that if I posted anything like that again, UTD would contact PADI to have me punished--possibly expelled--as an instructor for violating the member standards against disparaging another agency. That was when I left UTD.

PFO's occur in about 25% of the general population, with people rarely knowing they have one unless some medical condition results in a check. In the world of diving, the percentage of people getting DCS is far below 1%, not the 25% you would expect if they were the big cause of DCS. In addition, many of the people who get bent do NOT have PFOs--I am an example of that.

Thus, only a tiny, tiny percentage of divers with PFOs get bent, yet some people will have you think that having one guarantees DCS.

Clearly, the risk of DCS if you have a PFO and a UTD cert is higher than just having either one alone.

 

[rjack321]

Clearly, the risk of DCS if you have a PFO and a UTD cert is higher than just having either one alone.

The original ratio deco was definitely more aggressive than 20/85. Deeper deep stops which were substituted for some of the shallow time. But at that time nobody knew that sliding everything deeper was worse and there were models like VPM and other published literature (like on Okinawa pearl divers) hyping this approach. That it turned out to be wrong is just a reflection of how recreational deco was and still is in many ways very much an unknown.

 

[CAPTAIN SINBAD]

When I was with UTD, I had several fairly heated arguments with both my instructor and Andrew Georgitsis about our reliance on ratio deco and its deep stop obsession, especially at the altitude (4,600 feet) our UTD group was diving. I was repeatedly told that no one had ever gotten bent using ratio deco, even at that altitude. I said I could name 8 instances in our group alone, incidents resolved using surface oxygen, in-water recompression, or a chamber ride following helicopter evacuation. I was told that those cases did not count because there was always another cause, usually a suspected PFO or other unknown cause. I asked Andrew how he knew that those other things, not ratio deco, had been the cause, and he replied that ratio deco could not have been the cause because no one had ever been bent using ratio deco.

I started a thread on ScubaBoard in which I mentioned how many people had gotten bent in our group, and I received an email from my instructor telling me that if I posted anything like that again, UTD would contact PADI to have me punished--possibly expelled--as an instructor for violating the member standards against disparaging another agency. That was when I left UTD.

I also had many similar discussions with my UTD instructor though in my case, they were more constructive instead of heated. Andrew is no longer with UTD and they have totally re-invented their decompression strategy so at least my earlier skepticism isn't valid anymore.

One thing I must mention is that a whole lot of people get bent well within the limits of dive computers. I do not recall the exact numbers but there was a DAN study that was quoted in my UTD class that gave that exact number. It was shocking! If your GPS device was showing that degree of an error then planning your trip without a GPS device or with some other back up would not be as irrational.

UTD's interpretation was that those hits within NDL recreational limits were due much less because of insufficient decompression time but more due to divers ascending too shallow, too fast for their safety stop. UTD had tried to rectify that by using half stops as their decompression strategy. This meant that after a 100 ft dive, a computer diver would take you to 20 feet and let you hang there for 3 - 5 minutes while a UTD diver would stop for one minute at 50 then 40, 30, 20 and 10. Deco time with Min-Deco limits was not much longer than most recreational computers but it would start deeper. This half-stop all the way up was not to be confused with deep stops that are still a matter of debate among technical diving community.

Skeptical of this decompression method, I reached out to Mark Powell and asked him if such half stops done outside of a computer generated algorithm would be beneficial in preventing hits that DAN is documenting among computer users. In his book he had quoted a DAN recommendation that recreational divers should begin their stops at a deeper depth (half depth) than where a typical computer would take them which is exactly what UTD was all about.

Here is the conversation I had with Mark:

Me: Greeting Mark, quick question. I understand your earlier version of Deco for Divers that doing half stop in recreational diving profiles (100 ft and shallower) can be beneficial. With Spisni study on deep stops and US Navy study, do you still regard it to be a good decompression practice? It would require a GF lo to be 5. Thanks.

Mark Powell: Those studies were not on no-stop dives so i wouldnt say they were relevant. I think the DAN study is still relevant for no stop dives so I would still do them on no stop dives.

And this was coming from a guy who is an authority on decompression and very high in TDI and not even remotely connected to UTD or GUE.

My take is that there is that algorithms in their pure form are old and there is a lot of newer data that is resulting in recommendations that a computer will never project at you. Helium Penalty is another perfect example. You computer on Buhlmann will still show that. Thus instead of training a diver to chase a computer whether it is Buhlmann or VPM or RGBM, UTD is teaching decompression models just like any other mainstream agency. But ... their final decompression schedule is also influenced by all these factors that are presently not inside any algorithm. You will have to reach out to DAN and Mark Powell and a whole lot of other to arrive to that conclusion.

 

[boulderjohn]

I also had many similar discussions with my UTD instructor though in my case, they were more constructive instead of heated. Andrew is no longer with UTD and they have totally re-invented their decompression strategy so at least my earlier skepticism isn't valid anymore.

One thing I must mention is that a whole lot of people get bent well within the limits of dive computers. I do not recall the exact numbers but there was a DAN study that was quoted in my UTD class that gave that exact number. It was shocking! If your GPS device was showing that degree of an error then planning your trip without a GPS device or with some other back up would not be as irrational.

UTD's interpretation was that those hits within NDL recreational limits were due much less because of insufficient decompression time but more due to divers ascending too shallow, too fast for their safety stop. UTD had tried to rectify that by using half stops as their decompression strategy. This meant that after a 100 ft dive, a computer diver would take you to 20 feet and let you hang there for 3 - 5 minutes while a UTD diver would stop for one minute at 50 then 40, 30, 20 and 10. Deco time with Min-Deco limits was not much longer than most recreational computers but it would start deeper. This half-stop all the way up was not to be confused with deep stops that are still a matter of debate among technical diving community.

Skeptical of this decompression method, I reached out to Mark Powell and asked him if such half stops done outside of a computer generated algorithm would be beneficial in preventing hits that DAN is documenting among computer users. In his book he had quoted a DAN recommendation that recreational divers should begin their stops at a deeper depth (half depth) than where a typical computer would take them which is exactly what UTD was all about.

Here is the conversation I had with Mark:

Me: Greeting Mark, quick question. I understand your earlier version of Deco for Divers that doing half stop in recreational diving profiles (100 ft and shallower) can be beneficial. With Spisni study on deep stops and US Navy study, do you still regard it to be a good decompression practice? It would require a GF lo to be 5. Thanks.

Mark Powell: Those studies were not on no-stop dives so i wouldnt say they were relevant. I think the DAN study is still relevant for no stop dives so I would still do them on no stop dives.

And this was coming from a guy who is an authority on decompression and very high in TDI and not even remotely connected to UTD or GUE.

My take is that there is that algorithms in their pure form are old and there is a lot of newer data that is resulting in recommendations that a computer will never project at you. Helium Penalty is another perfect example. You computer on Buhlmann will still show that. Thus instead of training a diver to chase a computer whether it is Buhlmann or VPM or RGBM, UTD is teaching decompression models just like any other mainstream agency. But ... their final decompression schedule is also influenced by all these factors that are presently not inside any algorithm. You will have to reach out to DAN and Mark Powell and a whole lot of other to arrive to that conclusion.

After I published my study of (then) current thinking on deep stops in decompression diving, I tried to do a similar study on deep stops in recreational diving. Dr. Simon Mitchell had helped me tremendously on the first article, but he refused to help on the second article because he said there was not enough evidence to draw any conclusion. After completing my research, I decided there was not enough evidence to draw any conclusion, and I did not attempt to publish anything. The few studies that supported deep stops in recreational diving had methodological flaws that made it difficult to draw conclusions.

Mark Powell was an extremely strong proponent of deep stops in decompression diving, and he only published an article saying some stops might have been too deep literally months before my work on the article I published. You will see his statement quoted in that article. He remains a bit skeptical to this day and, to his credit, he has been doing some research of his own. What he has found so far does not support the use of deep stops.

You can't just say that DAN thinks this or that, because there are two DAN's with decidedly different points of view. DAN America does NOT support the use of deep stops in recreational diving, but DAN Europe does. DAN Europe used to cite a discredited study from about 15 years ago as its reason, but the last time I looked (and I didn't refresh before this), their article did not cite supporting research.

There really is a very big difference between recreational, no stop diving and decompression diving in terms of the ascent. The evidence in decompression diving is clearly looking now to oppose delaying ascents and calling for longer shallow decompression times when descents are delayed. The evidence for recreational diving is just not there. Diver A may get to within 3 minutes of NDL at depth, ascend directly to a safety stop, and then surface. Diver B may get to within 3 minutes of NDL at depth, ascend to an intermediate strop, proceed to a safety stop, and then surface. Diver C may get to within 3 minutes of NDL at depth, 30 feet and stay there for 15 minutes, staying within NDL, ascend another 20 feet and stay there 10 minutes, ascend to a safety stop, and then surface. There is just no good, researched evidence of any superiority of any of those 3 profiles.

 

[boulderjohn]

The original ratio deco was definitely more aggressive than 20/85.

IIRC, the original strategy called for rounding off whole ATA's for determining starting depth and first stop depth. (I may be misremembering.) There are depths where that rounding put your first stop pretty much where you are now.

 

[boulderjohn]

One thing I must mention is that a whole lot of people get bent well within the limits of dive computers. I do not recall the exact numbers but there was a DAN study that was quoted in my UTD class that gave that exact number. It was shocking!

Recent data from Europe indicates that a very large majority of DCS cases with NDL dives happened with divers diving within NDLs. That should be as shocking as saying the overwhelming majority of people who die in Germany are Germans and concluding that Germans are in particular danger in that country. As that study concluded, almost everyone who does NDL diving does so within established limits, so what is actually shocking is that the percentage is not much higher.

The percentage of dives resulting in DCS, regardless of the algorithm, is extremely low. It is impossible to calculate with any precision, but most estimates put it at about 0.02%. That indicates that existing algorithms are pretty darn safe, which is why I believe nearly no one is studying this.

This meant that after a 100 ft dive, a computer diver would take you to 20 feet and let you hang there for 3 - 5 minutes while a UTD diver would stop for one minute at 50 then 40, 30, 20 and 10. Deco time with Min-Deco limits was not much longer than most recreational computers but it would start deeper. This half-stop all the way up was not to be confused with deep stops that are still a matter of debate among technical diving community.

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.

When I reached to to UTD for their explanation, they declined to respond.

My take is that there is that algorithms in their pure form are old and there is a lot of newer data that is resulting in recommendations that a computer will never project at you. Helium Penalty is another perfect example. Their final decompression schedule is also influenced by all these factors that are presently not inside any algorithm.

What are those factors? The helium penalty only relates to deeper dives using helium. Do you know any of the "newer data" for NDL dives upon which the UTF practice is based? I don't know of anything. What kind of factors would they be using that are presently not inside any algorithm? Where did they find them?

When I asked Andrew how he knew there was no need to factor altitude into an ascent profile, he told me he knew this because he dived at Lake Tahoe without making an adjustment, and he was fine. Is that the kind of "factor" you are talking about? (I am aware that UTD has recently said that they never claimed that altitude was not a factor that needed to be considered; that sure conflicts with my memory.)

 

[Wibble]

Recent data from Europe indicates that a very large majority of DCS cases with NDL dives happened with divers diving within NDLs.

It's not that surprising as decompression algorithms and the gradient factor adjustments are NOT an exact science, but are based upon statistical probabilities that people don't get DCS if they follow X GF (other algorithms are available, all the same principle). Thus there's a statistical curve where people don't get bent.

Bottom line; given the number of recreational divers, it's hardly surprising many of them get DCS.

 

[rjack321]

IIRC, the original strategy called for rounding off whole ATA's for determining starting depth and first stop depth. (I may be misremembering.) There are depths where that rounding put your first stop pretty much where you are now.

The original RD rules started stops at 75% of depth which was actually pretty reasonable for a 20min 90m dive. It completely falls apart on a 70min 35m dive.

I mean in my actual T1 course (which predated UTD in 2004ish but we were using Andrew's RD) our first stop from a 20min 150ft dive was at 110ft (wtf?). There was 10mins of deco between 70 and 30 which went something like 3,3,1,1,2, then 10mins at 20ft, then about 6mins to the surface.

110-1
100-1
90-1
80-1
70-3
60-3
50-1
40-1
30-2
20-10
shallow up 6
total = 26 minutes but there's 4 extra minutes before you even get to the 50% switch (that's 20% more "BT")

On the same 21/35 and 50%, 20/85 would be:
90- 0.5
80-1
70-1
60-1
50-1
40-3
30-4
20-7
10-14
total = 32mins but there's is 50% more shallow time

Something like 50/75 would have the same basic stops around the switch but be about 4 mins longer due to a lengthier shallow stop.

The original RD and even some of the minor changes over the years is just nuts in retrospect and definitely anything but best science now.