Will http://www.ncbi.nlm.nih.gov/pubmed/25525213 change deco procedures?

[PfcAJ]

Circular logic works because circular logic works.

 

[Dr Simon Mitchell]

These extra points and information were added to the discussion after the RBW thread closed. They are only available in other threads. These points below really complete the picture.

Actually, all of this (including the "points below" which are just old ones illustrated more deceptively) was dealt with on the RBW thread. I reiterate, anyone who wants to understand this issue properly needs to read that thread.

The assumption to connect this shallow stop test to deep stops, lies in A\ the fallacy of the reports title, and B\ these 'plausable explanations' that Simon makes:

Note how Ross likes to portray this as an argument between him and me.

That suits his narrative but it is not the truth. The argument is actually between him (with no training in science let alone decompression physiology) and the only full time team of decompression scientists in the world (who work for the US Navy). I am only involved because I choose to defend the work that he tries to denigrate.

I do that because technical divers are my peer group and I consider the accurate dissemination of information with safety implications within that group as a priority, and with the exception of David Doolette, the scientists who actually did the work can't be bothered getting bogged down in these sorts of discussions. You need to be very clear about who the protagonists on either side of this argument are. Its not a simple case of Ross and me as he tries to portray it.

Note: Anyone can make these profiles and diagrams above in MultiDeco. Supersaturation tracking and graphing is part of the program.

Also a new feature, is that you can look at individual cell pressure that make up those graphs (right click, show cell #).

Please also note the gratuitous advertising.

....paid trolls....

Ross, since you are back, can I bring you back to your insinuation that someone "paid trolls" to involve themselves in the RBW thread. This is an allegation that I am taking seriously. Who were the trolls and who paid them? You said it. Now man-up and back it up. Or has it now become acceptable to post the most outrageous accusations and then pretend it didn't happen when the heat goes on?

Simon M

 

[Storker]

Ross, since you are back, can I bring you back to your insinuation that someone "paid trolls" to involve themselves in the RBW thread. This is an allegation that I am taking seriously. Who were the trolls and who paid them? You said it. Now man-up and back it up. Or has it now become acceptable to post the most outrageous accusations and then pretend it didn't happen when the heat goes on?

I'd really like to hear an answer to that question, too.

It's one thing to talk the talk. What about walking the walk?

 

[UWSojourner]

No. Deep stop profiles typically finish with about the same maximum supersaturation pressure as the shallow stop equivalent profiles.

One last point about how to read the deep stop thread and what you have to consider as you read it.

The quote above from Ross illustrates the issue. He focuses on "maximum supersaturation pressure". And I agree that if you look solely at the type of lines he shows in his charts you'll likely miss the importance of the NEDU study.

An analogy might help. Think of decompression as a drug. When you're determining if a drug is safe you can't focus solely on the purity of the drug. You have to consider the dosage. You could probably take pure heroin without any effect if you only consumed 1/10000th of a teaspoon. On the other hand, if you took enough diluted heroin, let's say 1/100th strength, you could die.

Ross's focus on "maximum supersaturation pressure (MSS)" is an appeal for you to focus solely on the purity of the drug. But what the NEDU study showed was that while the deep stop profile diluted the purity (lower early supersaturations), it did so at the cost of a higher dosage overall (you had to endure supersaturation longer). The net effect was a much higher DCS rate in the deeper stop profile.

So, as you're considering the ideas of the NEDU study, keep an eye on supersaturation-time. See Doolette's presentation here (you could start at about min 27:50)

See here and here for just a couple of the posts discussing this idea in the deep stop thread.

 

[rossh]

This, Ross, is the root of my issues with your posts. I know my opinion means nothing to anybody but myself, but I can't be alone here. You state things as fact because MultiDeco spits out some charts based on an algorithm to theoretically track loadings based on a theory that has been proven to be incomplete (at best). MultiDeco is a great program, and I applaud your efforts in bringing the features you do to the table. VPM is an algorithm that has returned many divers safely to the surface. What neither of them can do is claim to actually track supersaturation (and other factors) of divers doing dives. It can calculate projected, theoretical values based on a large series of assumptions. Deco studies, like this one and the NEDU deep stops one and many other ones can be used to test algorithms and assumptions those algorithms are based on. What you can't do is use the algorithm to self-validate itself.

Yes and no. Supersaturation tracking is NOT model dependent. No self validation here. The formula used here is generic - it can be used to cross compare different models. It's the same gas tracking half time formula used in everyday science, and all throughout deco research for decades. Its also shown in the nedu (no)deep stop test reports. Divers do not normally see this information because its internal, and hard to project.

Explained here: Quoted here from Intro of Nedu TR 11-06 and David Doolette: Σptisj − Pamb > 0, for j=1, …, n





So forget all about the idea it's model or MultiDeco dependent here - its not. I think that addresses most of what you said above.

Now you are most welcome to fully replace the Haldane half time gas tracking with something else. But you still likely have a time based tracking system. And, if it makes the same kind / shape profiles, it too will look like these charts above. You can't get away from these basic formula.

This study has a lot of very interesting implications if true, many of which would invalidate (word choice is probably poor) many algorithms and assumptions we use today. For practical purposes, I think little has changed. I'll still continue to dive the algorithm and conservatism that gets me out of the water feeling good. However, long-term consequences are yet to be seen and this could be a huge step forwards. If this study is true, it seems the "Helium penalty" might need to be reduced to nothing in Buhlmann and the "Depth penalty" (my term) needs to be increased. This might mean a new algorithm can emerge, which is exciting, even if it's only a refined variant of what we know and dive today.

If we can cook up a new model, I'll be happy to add it in to MultiDeco. But it has to be full proper design.


But I really wonder why we need a new one? Do we have an epidemic of injury? No. Are people looking for ways to go faster? Is anyone pushing the envelope? No. The opposite infact - looking for any reason to go slower and longer. So are we just making reasons to justify going slower??


Today we can dive just about any model or settings on the market and get away with just fine. The reported DCS rate is pretty low. If we go really deep, then other physiological factors take over the risk from the basic gas pressure stress, so the model doesn't matter so much here.

So all we are really doing now is fine tuning for precision, that is probably unattainable. But here is the kicker - if we can develop more accurate ways of predicting and measuring, then it will inevitably say "go faster, do less". Is the diving population ready to accept that? I don't think so.

 

[PfcAJ]

But I really wonder why we need a new one? Do we have an epidemic of injury? No. Are people looking for ways to go faster? Is anyone pushing the envelope? No. The opposite infact - looking for any reason to go slower and longer. So are we just making reasons to justify going slower??


Today we can dive just about any model or settings on the market and get away with just fine. The reported DCS rate is pretty low. If we go really deep, then other physiological factors take over the risk from the basic gas pressure stress, so the model doesn't matter so much here.

So all we are really doing now is fine tuning for precision, that is probably unattainable. But here is the kicker - if we can develop more accurate ways of predicting and measuring, then it will inevitably say "go faster, do less". Is the diving population ready to accept that? I don't think so.

You must live in some sort of weird bubble. There ARE people pushing the envelope, that want to get out of the water faster, that are having DCI issues (or some combo of those 3 items). Thats the entire point of these discussions.

Personally, I'm interested in a) decompressing from long exposures (the current models don't do well with that), b) maintaining an even risk of DCS regardless of the type of dive I do (again current models don't do that) and c) shaping the ascent to get out of the water efficiently (fastest ascent while maintaining item b).

All these studies and ideas we're discussing are attempts to unravel the mystery. You really seem against the furthering of knowledge in this field. Its strange.

 

[rossh]

Ross, since you are back, can I bring you back to your insinuation that someone "paid trolls" to involve themselves in the RBW thread. This is an allegation that I am taking seriously. Who were the trolls and who paid them? You said it. Now man-up and back it up. Or has it now become acceptable to post the most outrageous accusations and then pretend it didn't happen when the heat goes on?

Simon M

This is what I said:

RossH: "A better discussion of this (nedu no-deep stop test) was round 2, in the back half of this thread - no paid trolls in this one."


The rest of the above is all YOUR vivid imagination.

---------- Post added December 22nd, 2015 at 02:46 PM ----------

You must live in some sort of weird bubble. There ARE people pushing the envelope, that want to get out of the water faster, that are having DCI issues (or some combo of those 3 items). Thats the entire point of these discussions.

Personally, I'm interested in a) decompressing from long exposures (the current models don't do well with that), b) maintaining an even risk of DCS regardless of the type of dive I do (again current models don't do that) and c) shaping the ascent to get out of the water efficiently (fastest ascent while maintaining item b).

All these studies and ideas we're discussing are attempts to unravel the mystery. You really seem against the furthering of knowledge in this field. Its strange.

Live in a weird (micro)bubble - yes of course - you don't think I'm normal do you?

OK, so yes some people, younger people, adventurous, some tech folk, are looking for faster, but they are the minority I think, particularly in the CCR demographic. There is plenty of old navy tables to do that with and get the bubbles growing.

 

[tomfcrist]

I would still like to see a legit comparison study where the deep stop model isn't calling for ridiculously extended stops in the "deep" end of the ascent. Limit those stops to 1-3 minutes dependent on depth(deepest stops being shorter) and keep the same times on the shallow zone stops. That would do two things...get out of the water faster than the shallow stop schedule, and limit the additional on gassing of the slower tissues during those deeper stops. I'd be willing to bet there would be a significant change in the NEDU studies findings.

 

[rossh]

One last point about how to read the deep stop thread and what you have to consider as you read it.

The quote above from Ross illustrates the issue. He focuses on "maximum supersaturation pressure". And I agree that if you look solely at the type of lines he shows in his charts you'll likely miss the importance of the NEDU study.

You can also look at intermediate supersaturation pressures in MultiDeco - where they rise / fall into significance ( the cell # view ). You can also view the post dive effects of supersaturation and its duration.



Every dive is different, but for this discussion the major differences that Simon and the RBW thread claim, simply do not exist in real dives. There are subtle changes, but none are remarkable. The models are capable of handling the intermediate changes, because that is the basis of the gas tracking design.

 

[Dr Simon Mitchell]

What is amazing here is your lack of morals.

When you thought the trolls in the RBW thread worked for free, you used them to create havoc, post advertising style pictures and campaigns, actively insult and attack me and others, they posted lies, fabrications, fake data, junk science. etc etc. They stomped all other the truth and left huge trail of rubbish.

You are still actively promoting that same thread of marketing rubbish and fakery.

But now that you think that the trolls were paid, you now object ??

You approve and actively encouraged the trolls to prop up your failing arguments, with a "no holds barred" attitude, but only if they do it for free. What a poor set of morals you have.

Rubbish. No one is going to get tricked by your fake sincerity.

This is what I said:

RossH: "A better discussion of this (nedu no-deep stop test) was round 2, in the back half of this thread - no paid trolls in this one."

The rest of the above is all YOUR vivid imagination... and the little voices in your head, inventing negative comments to throw at me.

No way Simon - go play your stupid game somewhere else!

and:

No. Simon made up the accusation all by himself and hung it on himself. He can explain why. He only has himself to blame for this one.

You post a clear insinuation that I (or someone related to my side of the debate) paid trolls to participate in the RBW thread.

I challenged you to back up that accusation, and your response was to claim:

1. That I agree there were trolls posting lies, fabrication etc; and,

2. That I have accused myself of paying them.

People can judge your rationality for themselves, but basically I rest my case.

Simon M