UTD Ratio deco discussion

[CAPTAIN SINBAD]

The actual reason has something to do with an increase in carotenoids (sp?) in the divers following profiles with the old RD. I believe the results of the Italian study are still not published due to an embargo as Dr. Simon Mitchell mentioned in another thread.

I understand that part but after the Italian study as well as the NEDU study, recommended gradient factors were 50/80. This is what Dr. Simon Mitchell recommends too. Based on these GFs the first stop should be much shallower than 66%.

What exactly was in the Italian study that caused UTD's interpretation of it to be different than Dr. Mitchell's? If anyone has read the paper can you please comment?

 

[mikeny9]

Careful, I think he was very specific and mentioned that he uses 50/80 but that he can't recommend it scientifically.

 

[boulderjohn]

Which way? Generally RD tries to spend as much time at 1.6 PPO2 for the whole "oxygen window" thing while limiting on-gassing of the fast tissues, that's the goal anyway as I understand it.

Interesting. I didn't know anyone still believed that.

 

[Diver0001]

I understand that part but after the Italian study as well as the NEDU study, recommended gradient factors were 50/80. This is what Dr. Simon Mitchell recommends too.

Simon is quite careful to explain that 50/80 is what he uses but that he doesn't have enough scientific data upon which those GF's could be "recommended". The numbers he chose were a "best guess" based on his personal interpretation of the available information.

R..

 

[Diver0001]

Interesting. I didn't know anyone still believed that.

There is quite a bit here that's hard to believe.

If you look at this in the big picture then RD had a function when it was first developed because there were no decent (or affordable) technical computers in common use. People were cutting tables and the dives lacked flexibility. RD, for a time, offered the diver some flexibility.

With the advent of decent technical computers and the significant developments to our understanding of deco theory that have happened since 2007 and onward, RD has lost all relevance for diving. RD contains a number of elements that are based on debunked thinking and outdated paradigms. Why anyone would want to use it is beyond me and why anyone would recommend it in the face of much better options is completely incomprehensible.

When put in the context of safety and efficiency, computers do a much better job now than they did when RD was developed and they do a much better job of accurately representing the necessary deco than any version of RD does, or can.

Therefore, it seems illogical at best and irresponsible at worst for an agency regardless of the alphabet soup, to be "hanging on" to this. Furthermore, an agency that purports to represent the pinnacle of diving should have dropped it long before now and embraced the need to modernize it's thinking with respect to decompression theory.

To my way of thinking, the most important thing anyone can take away from this discussion is this. If you're making technical dives, you should ignore the smoke and mirrors and use a computer with an appropriate algorithm for technical diving, based on Buhlmann ZHL16c and having functionality for tweaking via gradient factors. There are a number of good ones on the market.

R..

 

[victorzamora]

I am curious to know why 66% of depths was chosen as the first-stop depth? It is still more logical than 75% stop depth but is there a particular gf lo that this stop is trying to replicate?

Sinbad: I think one thing you're missing here is that UTD's RD approach doesn't follow GFs or any particular algorithm that could potentially have GFs applied. UTDs RD doesn't use Buhlmann, VPM, RGBM, etc. It's a standalone, completely separate entity. It was never meant to follow any other profiles, just like VPM was never meant to follow Buhlmann....UTD teaches RD as a standalone replacement for the other algorithms.

GUE's RD implementation (I believe they're calling it "Pragmatic Deco" or something) is a series of rules/guides that per standards closely approximate a Buhlmann (20/85?) profile. However, it's up to the end user to decide the shape of the ascent based on their experience, current scientific understandings, and a software-based deco planner. A good buddy of mine has changed his RD approach to better suit 50/80 which is what his Petrel runs. GUE teaches taught RD (and teaches whatever it's called now) as a method of approximating known profiles of your choice. It makes sense when you can't get back to a computer for dive planning because a site is blown out or your plan runs different.

To try to match UTD's RD to something "known" like Buhlmann, you'd need to do take a profile that UTD's RD calculates (examples exist on this thread and elsewhere) and then just run a bunch of simulations in your deco planner and vary the GFs until you get something close. However, you'll never approximate the S-curve with Buhlmann...so the middle stops will always look goofy. What you can do is get the first stop depth to match as well as the overall deco time. That'll give you GFs that kinda-sorta approximate UTD's RD implementation.

 

[mikeny9]

RD contains a number of elements that are based on debunked thinking and outdated paradigms.

Which elements? Where are they debunked? Care to elaborate rather than just give your opinion?

Why anyone would want to use it is beyond me and why anyone would recommend it in the face of much better options is completely incomprehensible.

Have you taken the class? Have you dove it?

When put in the context of safety and efficiency, computers do a much better job now than they did when RD was developed and they do a much better job of accurately representing the necessary deco than any version of RD does, or can.

I disagree, I think a computer can get you into just as much trouble following it blindly without thinking than RD can if people do it incorrectly.

To my way of thinking, the most important thing anyone can take away from this discussion is this. If you're making technical dives, you should ignore the smoke and mirrors and use a computer with an appropriate algorithm for technical diving, based on Buhlmann ZHL16c and having functionality for tweaking via gradient factors. There are a number of good ones on the market.

Smoke and mirrors? There are people who dive RD every day without issues, myself included (well, almost weekly, not daily). It's easy to say, "use what I use, everything else sucks" but have you actually tried RD for long enough to compare?

 

[Diver0001]

Which elements? Where are they debunked? Care to elaborate rather than just give your opinion?

Mike, you haven't seemed prone to listening at all on this thread so I'm not going to spend any time on it. You're turn. Go do your home work. Read up about the studies done by NEDU since 2007, process that information, talk to Simon if you have any questions and then you'll be on the same information level as people who are not suffering from the paradigm lock.

I don't intend this to sound rude but you're really behind the curve and not aware of it. I hope this helps you realize that.

R..

 

[mikeny9]

So you're claiming that the NEDU study disproves the efficacy of the O2 window? I'm still unclear exactly what you're claiming. You seem to be hiding behind general big hand-waving ideas without being specific as to how they disprove anything. Again, could you please elaborate?

 

[Diver0001]

Read first. Then talk.

NEDU studied the efficiency of deep stop algorithms and made some interesting discoveries. Read up on that first. It's all on Rubicon and there are some very good presentations and videos in circulation that will help you interpret what you are reading. Seriously, mate. Go do that first.

R..