Slow tissue on gas from stops

[PfcAJ]

I was talking about my UTD years, when as a UTD student the use of a computer was forbidden. I assume that those rules are still in effect for UTD students, but I am happy to be corrected if wrong.

If you’re taking a class from someone, I’d presume it’s because you want to learn whatever it is that they’re teaching. If the instructor is teaching sans computer, you paid for that instruction.

What you do after the class is entirely up to you. No one can “allow” or “disallow” you to do anything. You’re an adult. Make adult decisions.

No one other than you is responsible for your decompression.

 

[Dan_P]

Second, you're the culprit who brought absolute terms into this discussion with your "not unsafe" argument. In prior discussions the statements would tend toward something like "UTD-RD is less safe than ..." or "profiles that use UTD-RD deep stops introduce less safety into the profile than those using the same run time that don't." And those types of statements are backed by all the current scientific evidence. So you can have your "not unsafe" placebo. I'll stand by "The current state of research would imply that UTD-RD is less safe than widely used and available alternatives."

Hogwash, sir, and playing to a blag that "not unsafe" is some devious twist on something wrongfully claimed to be "unsafe", as it has been in this thread, mind you, is - frankly - absurd given that the two are obviously quite opposite in nature. One being "unsafe" and the other "not unsafe". It's quite a great deal more than semantical nuances man.

If you simply say;

"The current state of research would imply that UTD-RD is less safe than widely used and available alternatives."

(possibly adding "some of the" before the "widely used"),
It would in fact be a different matter - I could then say, sure "less safe", probably, but that may well be by a very slim margin if the circumstances used in NEDU are any indication, or, fair do old sport, but seemingly not to a degree that means we can purely dismiss any practical advantages one might find in using a methodology that uses a higher deep stop emphasis, or, are we discussing Ratio Deco 1.0 or 2.0 here?

Third, since you seem to have taken particular offense at the label "defective", I'll just say this. It was a bit of sarcasm in response to another post (not yours) that was attempting to put the label "effective" on UTD-RD, or on deep stops in general. I argued that it would be difficult to attach that label to UTD-RD after seeing the results of the UTD-RD vs GF study. Unless, of course, you attach "effective" to UTD-RD's name so that it reads "UTD-RDefective". A bit of a poke I admit, but one I enjoyed very much.

Having said that, I don't think "defective" is entirely too strong anyway. A "strategy" that can take 40+% more decompression time and transform that time advantage into a profile that imposes MORE decompression stress on divers HAS to be considered defective in some regard. Trying to salvage the argument with "well it's not unsafe" seems a bit ridiculous to say the least.

The sarcasm, it would seem, continueth

Look, if you'd say with basis in Spisni that Ratio Deco 1.0 placed too great emphasis on deep stops and/or spent too much time in the water, that'd be one thing - but "UTD-RDefective" I'll say is quite a different ballgame.

 

[Dr Simon Mitchell]

Hi Dan,

Hence, my point remains.
When someone posts a statement to the effect of "RD is dangerous/unsafe/defective", they have no scientific support for that claim.

UWSojourner has taken the words out of my mouth. A lot of semantic wordplay going on here. There is certainly enough evidence to suggest UTD-RD is less efficient and therefore less safe than a GF approach with less emphasis on deep stops. Whether that = "unsafe" depends on your definition of "unsafe". I personally would not call it that because the absolute risk of DCS has not been measured for RD and something we might compare it to. But it is fair to say less safe. It could also be argued that the reduced efficiency constitutes a "defect". I would agree that "dangerous" is too emotive a term.

...and Dr. Brambilla, also in a video about the Spisni-study, sided by Dr. Longobardi and Prof. Spisni, said that using the 30/80 in that study was purely for safety reasons.

I'm not sure what you point is here. As indicated in the Georgitsis video, there was such a strong presumption of a positive effect for deep stops that the comparator profile for RD was constructed to contain fairly deep stops also (presumably for perceived ethical reasons). As I have said before there is reason to believe thaat UTD-RD would have looked worse in comparison to another GF profile with less emphasis on deep stops than 30/-.

Simon M

 

[Dan_P]

Hi Dan,

UWSojourner has taken the words out of my mouth. A lot of semantic wordplay going on here. There is certainly enough evidence to suggest UTD-RD is less efficient and therefore less safe than a GF approach with less emphasis on deep stops. Whether that = "unsafe" depends on your definition of "unsafe". I personally would not call it that because the absolute risk of DCS has not been measured for RD and something we might compare it to. But it is fair to say less safe. It could also be argued that the reduced efficiency constitutes a "defect". I would agree that "dangerous" is too emotive a term.

I'm not sure what you point is here. As indicated in the Georgitsis video, there was such a strong presumption of a positive effect for deep stops that the comparator profile for RD was constructed to contain fairly deep stops also (presumably for perceived ethical reasons). As I have said before there is reason to believe thaat UTD-RD would have looked worse in comparison to another GF profile with less emphasis on deep stops than 30/-.

Simon M

Hi Simon,

Semantics aside, and ignoring that RD1.0 and RD2.0 are being used wrongfully intertwined, the apparent logic then goes that any bubble model, RD and almost all GFs save one - and we don't know which one, mind you - are all "defective".
I disagree, and find that use of the word misleading, but anyone is free to call it semantics if they will.

"Less safe" I certainly have more trot with, but would add "though we have no idea how much or if it's even practically relevant compared to other factors", acknowledging of course it may be.

My point with Dr. Brambilla's remark (which I posted in response to a remark about Andrew Georgitsis' confidence in a video linked to previously), is that if experts in hyperbaric medicine would assume high emphasis on deep stops for safety - yes, presumably to accomodate the Declaration of Helsinki - and express this in a video; surely, it's fair game if a diver participating in the study also expresses confidence in deep stop emphasis in a video about the trial in question?

Is that not precisely heeding the words of scientists, as opposed to dismissing them?

On another note entirely, and I only mean this to be food for thought, I believe Spisni is only around a year or so since publication at this time, and Ratio Deco 2.0 has already been on the streets for quite a while. Doesn't exactly sound like the workings of an adamant zealot incapable of change...


Best Regards,

Dan

 

[Nirvana]

@Dan_P

I may have missed it being mentioned, but has there been any study designed to measure the success of RD 2.0 in preventing DCS, either in absolute terms (e.g. estimated incidence of DCS of x%) or in comparison with other algorithms?

If no study was done, or if a comparative study indicated a disadvantage of RD 2.0 in relation to another algorithm, on what grounds can it be claimed that using RD 2.0 for planning a decompression schedule is a reliable strategy?

 

[KevinNM]

I was talking about my UTD years, when as a UTD student the use of a computer was forbidden. I assume that those rules are still in effect for UTD students, but I am happy to be corrected if wrong.

I've seen a lot of Shearwaters with GUE students. I set mine up so it was in tech deco mode but with a stopwatch window and average depth window. No idea on UTD.

 

[boulderjohn]

I've seen a lot of Shearwaters with GUE students.

And with GUE veterans.

Last year I did a recreational dive in Florida, and as the people arrived at the shop in the predawn darkness, I saw a lot of GUE sweatshirts, sweatpants, caps, etc. When they set up their gear, I saw blue H's everywhere. I later chatted with some of them, and some turned out to be recognizable names from ScubaBoard--yep, the logos were not false advertising.

Every one of them had a Shearwater computer.

 

[PfcAJ]

Most Wkpp guys are using (well, at least wearing) shearwater or sea bear computers.

 

[Dan_P]

@Dan_P

I may have missed it being mentioned, but has there been any study designed to measure the success of RD 2.0 in preventing DCS, either in absolute terms (e.g. estimated incidence of DCS of x%) or in comparison with other algorithms?

If no study was done, or if a comparative study indicated a disadvantage of RD 2.0 in relation to another algorithm, on what grounds can it be claimed that using RD 2.0 for planning a decompression schedule is a reliable strategy?

To answer your first question, no.
Unfortunately, new comparative field studies are few and far between - and when we do get them, both the scope and scale of such trials would have to be, well, rather immense, to give us all the insights we're hoping for.

What we do have, is the Spisni trials, which UTD was heavily involved in. Again, the findings are no Rosetta Stone, but they did indicate strongly that RD1.0 had an overemphasis on deep stops.
RD 2.0 is a consolidation across on one hand the benefits of a standardized deco paradigm with the practical implications such a framework would have (diver development, gear limitations, systems interoperability, etc.), and on the other hand reducing the deep stop emphasis by several mechanisms including obviously the first stop depth, and particularly sacrificing emphasis on the O2-window to gain a reduced overall ambient pressure, and increased gradient.

Keep in mind it is a strategy as you say, and it comprises various elements, including the works of Bühlmann, and Pyle, and Wienke, and so on and so forth, but at the end of the day "what is a reliable strategy?" comes to mind - though, in fairness, there is definitely a larger body of knowledge available for certain specific profiles such as those of Bühlmann, no argument there.
Yet, conversely, we don't see very many divers who dive pure Bühlmann either.

 

[boulderjohn]

If you’re taking a class from someone, I’d presume it’s because you want to learn whatever it is that they’re teaching. If the instructor is teaching sans computer, you paid for that instruction.

That is true the overwhelming majority of the time, but not always.

There are cases, as was true in this case, when the students are employees of the shop that is offering the instruction, and that instruction is only offered through a specific agency. Any such employee choosing to get their instruction through a competing agency would be fired. When I decided to cross over to TDI after a couple years of UTD instruction, I did so knowing it would end my employment, and it did. (I was considering leaving for other reasons, which helped with my decision.)