UTD Ratio deco discussion

[leadduck]

Speaking of blurred lines, I'm not sure if that was a genuine question or an expression of a view that anyone in disagreement with you must effectively be a convolusive weasel.

Not in general; but in particular in this thread: yes, weasel tactics.

Unofficial materials have been shared by link in this very thread already.
If you want official materials, I'm sure you'll buy them.

From the information provided in this thread, I think it won't be worth the money.

 

[Dan_P]

As suspected.
Wishing you a good day.

 

[Dr Simon Mitchell]

Hello Dan,

By "almost certain CO2 retention", I referred to the 170ft portion and inferred a potential disadvantage to divers subsequently on deep stops, but be that as it may

Sure, CO2 retention would be much more likely during the working bottom phase of an air dive at 170'. But this would apply equally to both groups (deep and shallow stops) and my previous post articulates the reasons why it is unlikely the deep (70') or shallow (40') nature of the first stop would subsequently produce a related disadvantage in one group over the other. In addition, CO2 retention during the bottom phase of a dive is not exclusive to deeper air diving. A deep trimix dive could easily produce the same phenomenon, especially if the trimix is not compliant with current gas density recommendations, and in that regard the deep stops studies using air could be seen simply as replicating a real world phenomenon.

As you know, Ratio Deco was adjusted shallower by several mechanisms after the Spisni-study.

Yes, they are still fairly deep though.

The Spisni study is a lesson in how personality cults and associated blind faith have so much potential to lead to the wrong conclusions in relation to a topic like decompression. I presume you saw the video in which Andrew proclaimed his presumption of a positive outcome (for RD in that study) with extraordinary confidence and conviction. That was the same confidence and conviction he had brought to the topic for years in the absence of any data. A lot of people beleived it, and look what happened. It is a lesson for everyone.

I am most interested in the developments within the field, but simply am disappointed that the ensuing discussion generally has taken on form as though evidence concisely "debunks" gas mechanics in total (that is, a perception that m-values certainly being the only measure of importance, rather than some balance across concepts).

I essentially agree. There is too much definitive language on both sides of the debate. The most we can say at present is that the weight of evidence from human research suggests that if the goal is to achieve the most efficient decompression (least risk for the same decompression time) bubble models and RD over-emphasize the deepest stops.

Simon

 

[Dan_P]

Hi Simon,

I don't have a problem with the below, particularly given pre-Spisni levels (RD 1.0).

The most we can say at present is that the weight of evidence from human research suggests that if the goal is to achieve the most efficient decompression (least risk for the same decompression time) bubble models and RD over-emphasize the deepest stops.

I'm not too up in arms about what we have available to us at the moment in terms of definitive evidence, but I guess that's generally the name of the game in matters decompression.

There is too much definitive language on both sides of the debate.

Agreed.