UTD Ratio deco discussion

[mikeny9]

VGE is considered an indicator of deco stress. Deco stress is what you're trying to minimize.

We're in agreement there. What exactly are we disagreeing about?

 

[Patoux01]

Your claim dismissing the study (you most likely did not read) that reported high grades of VGE after a normally executed VPM dive.

Aka this "Right, there’s always bubbles present after any dive. It’s the size of the bubble that counts."

 

[PfcAJ]

Right, there’s always bubbles present after any dive. It’s the size of the bubble that counts. The deep stops added in RD 2.0 is meant to control the size of those bubbles, not accelerate deco time. O2-based decompression would certainly accelerate the ascent when compared to air.


Hmm, I've been listening all this time. I've asked you questions, and you're not answering them. What more can I do to listen @Diver0001? Just because I don't agree with you doesn't mean I'm not listening. Could you start with answering my questions?


AJ, nope. Like I wrote above, RD doesn’t aim to reduce any of the shallow stop time specifically by adding deep stops. I don’t think it ever did. The idea with the deep stops in RD 2.0 is simply to control the size of the bubble growth, not the presence of them. It in no way reduces your shallow stop time, as that time is necessary to treat the slow tissues.

RD 2.0 calls for adding 1 min deep stops when exceeding NDL by 15-29 minutes. Based off the NEDU deep stop study, then additional time should be added to the shallow stops to treat slow tissue super-saturation. I would certainly agree with that, but the study also doesn’t factor in oxygen-based decompression. UTD RD 2.0 doesn’t call for 66% stops until you’re 15-29 minutes over NDL, in which case the diver would certainly be using either 50/00 or 100% O2.

It certainly claims to affect the shallow stops. Some of the proposed oxygen times are downright nutty.

 

[mikeny9]

Your claim dismissing the study (you most likely did not read) that reported high grades of VGE after a normally executed VPM dive.

Aka this "Right, there’s always bubbles present after any dive. It’s the size of the bubble that counts."

I didn't claim that and never dismissed the study, but you jumped to that conclusion. I'm talking about micro-bubbles and subclinical DCS. UTD RD 2.0 doesn't follow VPM. The deep stop portion of the ascent, if anything is even added, is meant to control the size of the bubble, not reduce total ascent time.

It certainly claims to affect the shallow stops. Some of the proposed oxygen times are downright nutty.

Can you give an example?

 

[PfcAJ]

I didn't claim that and never dismissed the study, but you jumped to that conclusion. I'm talking about micro-bubbles and subclinical DCS. UTD RD 2.0 doesn't follow VPM. The deep stop portion of the ascent, if anything is even added, is meant to control the size of the bubble, not reduce total ascent time.


Can you give an example?

UTD VBlog: Complex Ratio Deco Questions · UTD Scuba Diving

Check out the slide behind him. Look at the 300ft oxygen time setpoint.

 

[boulderjohn]

Here is the problem. People have responded to you on a number of occasions, pointing out the issues, but you either ignore them completely or respond with statements that indicate that you are not on top of the theory. So, as long as you are in full lecture mode most of the time, no progress will be made. I was about to respond to [some of your statements, but the list got long. I quite. I will leave with just two tidbits.

You’re taking the deep stop study out of context. It involves using only air for decompression. I will agree with you that if we are using air only then adding deep stops adds more time, not less time, to the overall ascent.

If you read the threads on the deep stop study and understood anything about the scientific process, then you would understand why that is not an issue. For those who did not understand, the issue was explained ad nauseum in the thread.

So let’s go with the 9th time? UTD doesn’t officially teach anything about altitude diving.

Actually, you said at some points that UTD does have something to say about it somewhere. You said your instructor said that if you dive at altitude, you can't use RD without adjusting it. Another poster said a UTD instructor told him the same thing. So something is being taught. We do know that UTD divers dive at altitude. Heck, one of my friends from those UTD days died doing it, and his buddy couldn't walk for 3 months. So they are diving at altitude--we just don't know what they are doing for planning when they do.

BTW, as a member of PADI, if you asked me any question about PADI policy on any issue, I would have an official response from headquarters posted within a couple of days. I have done it probably a dozen times over the years.

 

[boulderjohn]

One more...

You claim there are are elements within RD that have been “debunked.” I’ve asked you three times now which elements, to which I’ve gotten no reply. Honestly, I don’t think you really understand much about RD and are relying upon incomplete or false information to draw conclusions about it.

I used to use Ratio Deco, and I stopped doing it based on my reading of research that debunked several items. I then went to VPM with V-Planner, and I used that for a while. I stopped doing that once again because my reading of the research indicated problems there as well. My decision to use Buhlmann with GFs of 50/80 is thus based on reading many studies over many years.

So if you want to know what elements of RD I see as being debunked, I will repeat them yet again. I have several times summarized the comparisons between the RD 2.0 profile that decompression posted and the profile I would have used instead on the same dive. Look at those summaries and you will the areas I believe have been debunked. I will repeat the comparison yet again, and I will summarize the problems.

Comparison of RD to Buhlmann at sea level:

1. RD first stop at 120 feet; Buhlmann at 90.
2. RD time on ascent between 180-80 = 9 minutes; Bulmann = 5
3. RD 70-60 time = 10 minutes (oxygen window theory); Buhlmann = 4
4. RD total ascent time to 50 feet = 19 minutes; Buhlmann = 9
5. RD total time at last two stops = 20 minutes; Buhlmann = 25
6. RD total Run time = 83 minutes; Buhlmann = 78

Comparison of RD to Buhlmann at 6000 feet:

1. RD first stop at 120 feet; Buhlmann at 90.
2. RD time on ascent between 180-80 = 9 minutes; Bulmann = 5
3. RD 70-60 time = 10 minutes (oxygen window theory); Buhlmann = 3
4. RD total ascent time to 50 feet = 19 minutes; Buhlmann = 8
5. RD total time at last two stops = 20 minutes; Buhlmann = 36
6. RD total Run time = 83 minutes; Buhlmann = 87

Debunked aspects of RD:

1. The first stops are too deep.
2. Too much time is spent on the deepest part of the ascent.
3. The S-curve provides no benefit and exacerbates the problem of too much time spent too deep. UTD is the only agency and its version of RD is the only algorithm that uses this. It is not so much that the science "debunked" it--it is more that science never accepted it. It was an outlier concept in an outlier publication.
4. It does not spend enough time in the shallow stops. This is especially problematic considering that the deep stops study said that if a diver spends more time doing deep stops, the the diver needs to spend even more time in the shallow stops to compensate. RD spends MORE time in the deep stops and LESS time in the shallow stops.
5. It cannot be used at altitude, so it leaves the altitude diver with no established way to do such a dive.

 

[CAPTAIN SINBAD]

There seems to be a fair amount of hard data out there that shows that deep stops as in 75% of depth and ultra low GF los are not as great as they were believed to be in the past. Both NEDU and UTDs own Italian study showed that so that point is well accepted. The question now is "since we have realized deep stops are not that great, how shallow should our first stop be?" Unfortunately there is no study that has answered that yet so while the motivation to move to a shallower stop is supported by studies, at what depth should people make that first stop is once again a matter of subjective preference. For Dr. Mitchell this personal preference is GF 50/80 and for UTD it is 66%. They are both operating on the premise, "science has convinced me that I need to move upwards but it has not shown me where to stop." They are both devoid of solid and conclusive reasoning as to why they have chosen their respective depths to make that stop. This is why pasting Buhlmann 50/80 next to Ratio Deco 2.0 does not "debunk" anything, at least at this point in the development of decompression algorithms. It only tells us that on a 150 ft dive, the acceptable area for making your "shallow stop" can begin from 99 feet depth and end at 50 feet and that is what I call "the 49 feet of arguable sanity."

 

[RayfromTX]

Hi John
When you say that these five things have been debunked can you show the documented evidence that you are referring to that shows them to be based on protocols that have been proven to be problematic? I think I know what you are referring to but the problem is that you are listing things that you don't like about RD without showing why you don't believe them to be safe or based on current studies.

For instance #1 The first stops are too deep.
I agree based on the NEDU studies from 2014 but if you just make the claim that this approach has been debunked without showing the evidence to back up your claim then you can hardly blame someone for demanding a reason for your claim.

I am in agreement with you but I'd like your position to be backed up by documented evidence instead of just repeating the claim. It seems both sides of this argument are doing the same thing. Making claims as if that is enough to convince the other side and then getting exasperated when it isn't and then just repeating the same claim without supporting evidence and accusing the other side of not listening to reason.

I repeat, I agree with you. I have followed the threads here and elsewhere very carefully and unfortunately that gives us a basis for our beliefs that is not transferable to others that lack the same exposure to the same material. Even reading the same material doesn't necesarrily mean that everyone comes away with the same understanding as is obvious from the various reactions in those threads. It may be obvious to us but even the research scientists warn against taking away too much from their findings. There are a number of people that think that those studies prove things that they only elude to. Proof has a much higher burden than evidence that simply leads us to adjust our best guesses. I'll still go with the best guess of the experts that I trust but I will not convince myself that something has been proven when my favorite experts say that it has not.

 

[boulderjohn]

Hi John
When you say that these five things have been debunked can you show the documented evidence that you are referring to that shows them to be based on protocols that have been proven to be problematic? I think I know what you are referring to but the problem is that you are listing things that you don't like about RD without showing why you don't believe them to be safe or based on current studies.

For instance #1 The first stops are too deep.
I agree based on the NEDU studies from 2014 but if you just make the claim that this approach has been debunked without showing the evidence to back up your claim then you can hardly blame someone for demanding a reason for your claim.

I am in agreement with you but I'd like your position to be backed up by documented evidence instead of just repeating the claim. It seems both sides of this argument are doing the same thing. Making claims as if that is enough to convince the other side and then getting exasperated when it isn't and then just repeating the same claim without supporting evidence and accusing the other side of not listening to reason.

I repeat, I agree with you. I have followed the threads here and elsewhere very carefully and unfortunately that gives us a basis for our beliefs that is not transferable to others that lack the same exposure to the same material. Even reading the same material doesn't necesarrily mean that everyone comes away with the same understanding as is obvious from the various reactions in those threads. It may be obvious to us but even the research scientists warn against taking away too much from their findings. There are a number of people that think that those studies prove things that they only elude to. Proof has a much higher burden than evidence that simply leads us to adjust our best guesses. I'll still go with the best guess of the experts that I trust but I will not convince myself that something has been proven when my favorite experts say that it has not.

When I started tech diving, I read extensively through a lot of material because I did not feel comfortable with what I was being taught. It was TDI, but the instructor was dedicated to GUE. He had taken GUE courses from AG, and his TDI instructor trainer was and still is an employee of the owner of GUE.

When UTD was created, the TDI instructor crossed over to the new agency, and all his students had to cross over with him. There were immediate conflicts, because what I was reading in the course materials conflicted with what I had been reading previously. I contacted Gene Hobbes of Rubicon repeatedly, and he steered me to a number of studies on decompression. Gene and I had some interesting chats about the results.

Those conflicts continued, and I had a special problem with the study that was the basis for the S-curve, which I believed had a totally unfounded conclusion that violated gas laws. I was also concerned greatly about the belief that altitude did not matter, which has been well documented in this thread. Again, Gene and I consulted.

I crossed back to TDI, and I read a lot of other articles as I began to adjust to life using VPM.

Then began the deep stops debates on Rebreather World and on ScubaBoard. Holy Smokes! Reading through all of that made my head spin. You can read through all of that if you like to get an idea, but you won't get the whole picture as far as I am concerned. Throughout much of the Deep Stops debate on ScubaBoard, I had an extremely intense ongoing email discussion with Ross Hemingway, one of the key antagonists in the debate. When I say "intense," you can assume it was not always a pleasant exchange.

For a while on a dive trip I roomed near one of the foremost authorities on decompression in the world, a man who consults on decompression issues with NASA and the Pentagon. I learned a lot.

All of that over a decade brings me to where I am. I can't estimate the number of articles I have read during that time, and I can't estimate the number of people with whom I have talked. The one thing I can say for certain is that I know there are people whose understanding of all of this is so far beyond me that I am in awe of them. I can't touch their knowledge or understanding. So where am I? All of it leads me to plan my dives the way I describe here. It is what I think right now is what is best. But my mind is open. If some new Earth-shattering research is released tomorrow, I will pay it all due heed. I will not cling to past beliefs because of past beliefs. As Emerson said, "A foolish consistency is the hobgoblin of little minds."

So what you are asking me is to got through the last decade or so of my research, track down all the articles I have read, and provide an annotated bibliography. The theory is that this will change people's minds. It won't. Other research shows that when people become entrenched in a belief and are presented with solid contradictory evidence, they become even more thoroughly entrenched in their original belief. It would take me hundreds of hours to do what you ask, and it will not change a single mind.