UTD Decompression profile study results published

[boulderjohn]

I took AG's statements about being a "tweaked" Buhlmann to mean Gradient Factors. I.e. when he talked about "pure Buhlmann" he was talking about Buhlmann with no GF used at all.

That's not what it meant when I was with UTD. I had no idea what gradient factors were then. As I understood it, the original Ratio Deco started as a tweak to DecoPlanner, a Buhlmann based software. Before UTD was created, I was in a TDI program with a GUE-influenced/trained instructor. We started with a DecoPlanner schedule and then modified it according to parameters, some of which I do not recall. One of them I do recall was adding what was called the S-curve, meaning that the first deeper stops after a gas switch were longer than the subsequent shallower stops until you got much shallower and lengthened them again. This is the opposite of what most profiles do. It was done to receive the supposed benefits of the "oxygen window," a theory found in a long-since debunked paper on decompression theory.

When UTD was created, my TDI instructor immediately crossed over, and all the TDI students became UTD students. We immediately dropped all the DecoPlanner tweaking and went with the UTD version of Ratio Deco exclusively for dive planning. The first deep stops were to be at 75% of our average depths, which is much deeper than most algorithms. We did the S-curve. We did not adjust for altitude because UTD does not believe altitude matters. Asked about the basis for this profile many times, Andrew answered that it is based on the way he feels after a dive. In one online session, someone asked how they could know it worked, and he said "You have to have faith!" "Faith in you?" the person asked. "Yes," he responded.

I left UTD shortly after taking part in a Ratio Deco class with Andrew. In it he admitted that the theory upon which the S-curve part of the profile was no longer considered valid, but he came up with two other reasons for keeping the S-curve. I thought both were bogus and don't remember either. At the time I left, GUE was also admitting that the theory was flawed, but as Jarrod Jablonski explained it to me, they were still keeping it because it had been successful in the past. They have since dropped it. UTD is still using it. If you look carefully at the UTD profile in post #12, you will see it starting at 21 meters.

 

[abnfrog]

thank you Simon as always ,thought provoking ....and of course I agree with you .....imho

 

[victorzamora]

That's not what it meant when I was with UTD.

John, I think Stuart was responding to me misinterpreting AG's statements in the video about "tweaked Buhlmann." I thought he meant he took ZHL-16C with GF30/80 and added more deep stops. It seems like his statements regarding "tweaked Buhlmann" were indicating that the GF30/80 was the tweak that was added. AG talking about tweaked Buhlmann is in reference to the other profile they were comparing the Ratio Deco 1:2 to.

Also, if you look at the PDF I added to my last post, you'll see the S-curve of RD very clearly.

 

[stuartv]

The report and the longer video KevRumbo posted make it clear to me that he's simply talking about GFs, but has little respect for them.

My point remains, though, about wanting to see how 50/70 would've done compared to RD and 30/80, as well as VPM-B+2.5 (as VPM+2 is slightly shorter and VPM+3 is slightly longer, or something like 50/75 compared to VPM-B+2).

When you say "the report", what are you talking about? Got a link? Or are you just referring to what Dr. Mitchell posted in the OP?

I also watched the longer video and my takeaway was that AG doesn't believe in "science" and "numbers" and "formulas". He believes in what makes him feel better. Crack addicts feel really good when they're on crack, too.

I also like how AG and the other UTD guy kept talking about how RD is not a formula. It's a strategy. You can adapt it. Well, uhhh, I can change the GF on my Shearwater during a dive, too. It really seemed like his only point was to hedge his bets in case the study showed that GF30/80 was better. So he could say "well, working out a hard plan in advance isn't really Ratio Deco, so you can't really say from this study that GF 30/80 is safer than RD."

I would like to see how GF50/80 would compare to what they did (GF 30/80). I'm really curious if using a lower number for GF Lo actually helps at all.

 

[lv2dive]

In both of my tech classes with GUE (tech 1 and 2) Ratio Deco was an additional tool used after one planned the dive using dive planning software. The advantages and limitations of RD were discussed; it was in no way represented as a panacea.

Also, I have no affiliation with GUE other than having taken training/being certified, but one of the things that I learned in my classes was that GUE has moved from any current affiliation with "DIR" (just a "for the record")

 

[stuartv]

John, I think Stuart was responding to me misinterpreting AG's statements in the video about "tweaked Buhlmann." I thought he meant he took ZHL-16C with GF30/80 and added more deep stops. It seems like his statements regarding "tweaked Buhlmann" were indicating that the GF30/80 was the tweak that was added. AG talking about tweaked Buhlmann is in reference to the other profile they were comparing the Ratio Deco 1:2 to.

Also, if you look at the PDF I added to my last post, you'll see the S-curve of RD very clearly.

Exactly.

After watching the video Dr. Mitchell posted, I also wondered briefly if AG meant that they were comparing RD to Buhlmann w/GF30/80 and then additional tweaks applied. But, I had concluded that what AG meant is that they were comparing RD against Buhlmann and he regarded the use of GF at all as "tweaks, intended to push the initial stops down deeper, to be more like RD."

 

[boulderjohn]

In both of my tech classes with GUE (tech 1 and 2) Ratio Deco was an additional tool used after one planned the dive using dive planning software. The advantages and limitations of RD were discussed; it was in no way represented as a panacea.

This is quite the opposite of the Ratio Deco class I took from Andrew. When we worked out a deco profile using ratio Deco, another UTD instructor in the room would do the same profile using one of several different commercial deco software programs. They never matched. According to Andrew, that showed why you should never use a commercial deco software program. Since RD is perfect, the fact that it never matched a commercial program showed that all those programs were defective.

 

[stuartv]

In both of my tech classes with GUE (tech 1 and 2) Ratio Deco was an additional tool used after one planned the dive using dive planning software. The advantages and limitations of RD were discussed; it was in no way represented as a panacea.

Since (apparently) GUE has changed their stance on this over the years, posts like this would probably be a little more helpful if they stated when they did the GUE training they are talking about.

 

[boulderjohn]

Exactly.

After watching the video Dr. Mitchell posted, I also wondered briefly if AG meant that they were comparing RD to Buhlmann w/GF30/80 and then additional tweaks applied. But, I had concluded that what AG meant is that they were comparing RD against Buhlmann and he regarded the use of GF at all as "tweaks, intended to push the initial stops down deeper, to be more like RD."

There is some truth in that, but the trend is now going the other way. Many people, myself included, believe the deepest stops in the GF 30/80 profile are too deep.

 

[stuartv]

There is some truth in that, but the trend is now going the other way. Many people, myself included, believe the deepest stops in the GF 30/80 profile are too deep.

Understood. The only issue here was Victor's (and my) initial impression that AG was comparing against GF plus more tweaks, versus our current understanding that when AG said "Buhlmann w/tweaks" he was referring to GF itself as the "tweaks". There were no twearks applied to "Buhlmann w/GF".