UTD Decompression profile study results published

[lv2dive]

I literally lol'ed at the post from yesterday morning and checked the date, then waited for this post

AHAHAHAAH APRIL FOOLS!!!!!!!!

I was beginning to think no one noticed or I'll have to be more subtle next year.

 

[scubadada]

I know that but what AG was saying is (1) bubbles lead to an immune reaction and (2) the immune reaction is actually what causes DCS.

Personally I don't buy it, I have a hard time accepting what the DIR heavy-weights say about deco theory in general and this just seems weird and obviously wrong to me.

R..

My take is that vascular inflammation may lead to platelet aggregation and thrombosis, contributing to the tissue ischemia caused by direct bubble occlusion. I would love to hear from others with more knowledge of the topic.

 

[Kevrumbo]

I know that but what AG was saying is (1) bubbles lead to an immune reaction and (2) the immune reaction is actually what causes DCS.

Personally I don't buy it, I have a hard time accepting what the DIR heavy-weights say about deco theory in general and this just seems weird and obviously wrong to me.

R..

My take is that vascular inflammation may lead to platelet aggregation and thrombosis, contributing to the tissue ischemia caused by direct bubble occlusion. I would love to hear from others with more knowledge of the topic.

My career dealt with inflammatory disorders, so I'm curious what these "inflammatory" or "immune" markers were in this study. Anyone know?

Circulating chemokines CCL2 and CCL5, I believe.

Old article from Immersed Magazine:
http://www.advanceddiverforum.com/pdf/Immersed - Rethinking the Hit.pdf

 

[Dan_P]

If I want the optimal gas for a given depth, I can use the optimal gas for that depth.
If I want the quickest way out, I can choose that.

If I want a framework of planning deco which works across all systems and throughout teams, across all levels, and can be adjusted if I cut my dive short, Ratio Deco does that. The strength of RD is not that it necessarily has the perfect gas for a given depth, or necessarily the fastest decompression schedule. The strength of it is that it it's a complete system that works and can be used and adapted in the field and throughout all my diving, whilst allowing easy in-water adjustments.

Yes, this deco project found some potential for improvement, and so UTD improved Ratio Deco.

The whole notion of strengths versus benefits is lost when the conversation revolves around which approach is best at a single given depth, gas and decompression, and the dive in question doesn't require adjustment of the decompression obligation. There are more layers to consider than that.

Sometimes RD will be more effective in terms of bubble formation and growth, sometimes other models will.
But I feel RD enables me to solve more diverse problems.
That's the strength of it, in my view.

 

[stuartv]

If I want a framework of planning deco which works across all systems and throughout teams, across all levels, and can be adjusted if I cut my dive short, Ratio Deco does that. The strength of RD is not that it necessarily has the perfect gas for a given depth, or necessarily the fastest decompression schedule. The strength of it is that it it's a complete system that works and can be used and adapted in the field and throughout all my diving, whilst allowing easy in-water adjustments.

Using computers that implement Buhlmann ZHL-16B/C and diving with 2 of them does ALL of those same things for me. And my dive computers don't ever make arithmetic mistakes. And they don't require me to dive suboptimal gases in order to work.

 

[huwporter]

Yes, this deco project found some potential for improvement, and so UTD improved Ratio Deco.

How did UTD identify which of their multiple alterations to the profile required improvement, since the study didn't shed any light on that (just that the sum result was inferior to the 11-minute shorter Buhlmann profile), and how do they know that the result - Ratio Deco(TM) 2.0 - is improved?

 

[Diver0001]

How did UTD identify which of their multiple alterations to the profile required improvement, since the study didn't shed any light on that (just that the sum result was inferior to the 11-minute shorter Buhlmann profile), and how do they know that the result - Ratio Deco (tm) 2.0 - is improved?

The question isn't even so much how they attempted to account for the devastating (for RD) results of the NEDU study. the question is how UTD scientifically verified their "improvements".

R..

 

[huwporter]

The question isn't even so much how they attempted to account for the devastating (for RD) results of the NEDU study. the question is how UTD scientifically verified their "improvements".

Yes, that was the question... thanks for spelling it out and revealing the trap.

(Because I'm betting that the answer is "AG made some changes and told us that it is more betterer now")

 

[Diver0001]

Yes, that was the question... thanks for spelling it out and revealing the trap.

(Because I'm betting that the answer is "AG made some changes and told us that it is more betterer now")

I'd put a very substantial amount of money on that bet.

R.

 

[Kevrumbo]

The question isn't even so much how they attempted to account for the devastating (for RD) results of the NEDU study. the question is how UTD scientifically verified their "improvements".

R..

Well in all objective fairness, there is no "scientific" verification as of yet either of @Dr Simon Mitchell 's recommendation of Buhlmann GF 50/80 as a baseline "improvement" on the implications of NEDU DeepStops Study, but is a reasonable conservative solution to start with.

How did UTD identify which of their multiple alterations to the profile required improvement, since the study didn't shed any light on that (just that the sum result was inferior to the 11-minute shorter Buhlmann profile), and how do they know that the result - Ratio Deco(TM) 2.0 - is improved?

Ah yes, that study. I think everyone is pretty much in agreement these days that strict VPM isn't so safe. From what I understand, the ratio deco approach maintains some deep stop theory to avoid too large of bubble sizes, much less than a strict VPM. For example, if you shape your O2 window from 70' to 30' and determine you need 1 min stops, but the deep stop table has you maintain 3 min stops, then you'd have to keep 3 min there to avoid too much bubble growth. That's where the "ascent strategy" comes from: they use deep stop theory to get to the O2 window and shallow/slow tissue zones. The approach aims to keep on-gassing of the slows to a minimum but also tries to control the bubble size to some extent.

The deep stops used to start at 75%, but now they are 66%. There is a 75% stop if you exceed NDL by 30 min, but haven't exceeded it by more than 45 min. However, those profiles are impractical for a Tech 1 student because you'd end up with too much deco time and would need a 50% and 100% O2 bottle. Also, when shaping the O2 window, ratio deco 2.0 prefers to add the "stolen" time from the middle to the shallowest (30') stop. So for example, a BT of 30 min at 150' using 50%, your ascent would look like:
Ascend to 100' at 30 FPM
100': 1 min (deep stop theory)
90': 1 min (deep stop theory)
80': 1 min (deep stop theory)
70': <switch 50 %> 3 min (O2 window)
60': 3 min (O2 window)
50': 2 min (O2 window)
40': 2 min (O2 window)
30': 5 min (dissolved gas theory)
20': 12 min (dissolved gas theory)
10': 3 min (dissolved gas theory) (or 20' 10 min 10' 5 min, etc)

I've compared a lot of profiles to my GUE friends and it's very similar to what they come up with in DecoPlanner that I wouldn't have a problem using their profile and everyone I'ved talked to (about 4 people so far) wouldn't have a problem doing the UTD profile either.

So in summary, it looks like 66% instead of 75% of max depth deepstop for the 1:1 schedule at the 45m depth RD Setpoint, and no more S-curve shaping on the intermediate Eanx50 deco stop.

For GUE Tech 1 RD at 45m Setpoint, I've "heard" that it's now just a straight 9m/min ascent rate to the 21m Eanx50 deco stop.