My DCS Hit

[Nitrogenius]

To defend and deflect, is your little posse of fanboys, trying to trick us all with psycho-babble.

and the absurdity continues..
again what you impose here that Simon is doing is in fact exactly what you are doing!
What was the definition of insanity again? Doing the same thing over and over and expecting a different result?

Its yet another distraction away from the reality that he was injured following a dive plan that uses your approved "new, more efficient" deco method..

Well as one of the "deflected fanboys" I have to state again that in my opinion the dive of Don is absolutely NOT following the "new, more efficient deco method" but is actually violating the suggested approach in mayn ways..
I have outlined the details of such violation and deviation before here and on RBW..
and lastly also mentioned several times.. same as you are the only one "campaigning" you are the only one that calls it "new, more efficient deco method!"
New? not so much just slightly (!!!! yes emphasis on slightly because that has been the recommendation to move cautiously!!) adjustement of existing (GF!) deco approaches..
more efficient? When did Simaon claim it was more efficient.. You were the only one stirring the pot about efficiency and actually claiming the opposite.. that this "new" method would be less efficient! while I can not pinpoint any comment on efficiency from Simon at ALL!

 

[Nitrogenius]

Is it just me, or is this thread taking a turn for the surreal?!! I find my self reading some of these posts and feeling like I'm about to be told the world is flat and NASA ESA etc are all out to fool us so the UN-run world wide theocracy can seize control with greater ease!

Great summary! and on point comparison!

 

[se2schul]

Is it just me, or is this thread taking a turn for the surreal?!!

It is not just you.

I'm seeing a scientist saying that he has seen evidence suggesting that deep stops might not be as beneficial as most of us have believed them to be, and I see him cautiously choosing his words to inform us of this evidence. I have never, ever, seen him raise the alarm and denounce deep stops and demand that everyone stop using them to avoid the impending death sentence that deep stops will surely lead to. He has said nothing but carefully measured words to inform us of this, and has suggested that if anyone wants to modify their deco accordingly, to cautiously back off deep stops slightly. That seems to me to be a very cautious, measured approach to relatively new data in this field.

From the other side of the fence, I only hear shouting about "fake news", "bad science", "flawed studies", how DSix's dive is "proof" that deep stops are needed, and that there are conspiracies in the scientific community around this study.

It is becoming insane.

It's almost as though Ross is hearing things that Simon is NOT saying.

 

[silent running]

Simon highlights my point perfectly.....

The lead scientist was Wayne Gerth, who presented his version at UHMS and DAN conferences in 2008. By that time, the test had served its purpose within the USN. The new USN dive manual version 6 (2008) was updated to a new set of model and tables, and it was all over.

Then 3 years later, David produced the 2011 re-formatted public report version, complete with his extras added, and more. I suspect you had been scheming for this since the whole thing was a non starter flop in front of your peers at the 2008 UHMS/DAN conferences, and failed to get any traction in the public. So you needed to do the "direct to public" approach, which is what you have been doing ever since.

In any case, you have interpreted and used the nedu test, way outside the consensus position of your peers in 2008.


Interesting.... you lot cannot defend your position in the nedu test and the false interpretations / claims you make: that it is has a link to tech diving, bubble models, or VPM.... You got nothing valid. All you got is more bluster and bully and authoritarian intimidation.... You don't have the science on your side for this one.

To defend and deflect, is your little posse of fanboys, trying to trick us all with psycho-babble.


*****

But what has any of this to do with Don's dive ??? Its yet another distraction away from the reality that he was injured following a dive plan that uses your approved "new, more efficient" deco method.

Yes it's one dive only, but it's a very big serious and significant test, and these really deep dives put a deco approach to the test and quickly find the faults. You better get used to this Simon and cross your fingers, because you pushed the world into this new direction based on your personal preference, and without a valid science reason behind it.

.

Simon's exact words from another forum:

"So, the existing human evidence collectively constitutes a clear signal that bubble models and other paradigms that promote deep stops have almost certainly over-emphasised them. That does not mean bubble models don’t work, or that you should not use them. Indeed, if you have been using a bubble model successfully, then maybe it is best if you stick with it. But if we seek the “truth in the universe” about optimal decompression, it is almost certain that bubble models prescribe deep stops that are too deep. I do not pretend to have a means of predicting optimal depth for first stops. That is why we have recommended divers attempting to de-emphasise deep stops do so in a cautious and measured way."

Are these the words of a crusading zealot? Sounds pretty measured and reasonable to me. Jesus Ross, crack a window and have one less nitecap. Thou certainly doth protest too much, the question is, why?

Have you asked Don why he chose his GF setting? Do you really think deep technical diving attracts trendy people looking for the latest fad?

And how about the guy Simon's treating who became symptomatic at 120m after ascending from a 150m dive, is that Simon's fault too?

You're a perfectly bright guy and certainly have something to contribute, can you find no middle ground to engage? How about refocusing this discussion on the knowledge base on VGE or discuss how perfusion and diffusion affect bubble growth or otherwise contribute to tissue injury during off gassing on ascent, and how you think bubble models take this into account? There's so much interesting stuff to discuss that there should be no time for name calling and innuendo. Deep technical diving shows that all models need improvement, so let's get to it...

 

[rossh]

It's almost as though Ross is hearing things that Simon is NOT saying.

Or I have read and been subject to more conversation on this topic, than you have read here. Simon's done all those things over the last 5 years... he still does not have the valid science he claims... its your assumption, and if you checked into the details, you see the validity of his arguments against deep stops are weak to n/a.

 

[silent running]

Or I have read and been subject to more conversation on this topic, than you have read here. Simon's done all those things over the last 5 years... he still does not have the valid science he claims... its your assumption, and if you checked into the details, you see the validity of his arguments against deep stops are weak to n/a.

Give one good reason anyone should trust your definition of what the valid science is or ought to be over Simon's, David's, Neil's, etc?

So put your money where your mouth is and ask Simon one valid question you think he can't answer based on the findings he has presented. Find one area of ambiguity and focus on it, if there are any structural flaws in the methodology they will be eventually found with this approach. Data are notoriously indifferent to name calling, but plenty vulnerable to a pointed question or two...

 

[rossh]

Give one good reason anyone should trust your definition of what the valid science is or ought to be over Simon's, David's, Neil's, etc?

So put your money where your mouth is and ask Simon one valid question you think he can't answer based on the findings he has presented. Find one area of ambiguity and focus on it, if there are any structural flaws in the methodology they will be eventually found with this approach. Data are notoriously indifferent to name calling, but plenty vulnerable to a pointed question or two...

I admire your pure intention, but why even try it? It will be the same as always... he makes some new claim of a reason or connection...I point out the error, mistake, lack of context, or what ever is not valid about it. My valid points are dismissed because Simon can't tolerate anyone having an opinion different to his own, and he has already taken a stance on the issue, and therefore cannot budge. Then the fanboys come along and stomp the conversation into the ground.

The nedu test explanation, his interpretation of it, and its non-connection to tech and lack of representation of deeper stops or VPM is a prime example. Look at all the BS that he and the fanboys have generated to create a cover story on that one.

.

 

[silent running]

I admire your pure intention, but why even try it? It will be the same as always... he makes some new claim of a reason or connection...I point out the error, mistake, lack of context, or what ever is not valid about it. My valid points are dismissed because Simon can't tolerate anyone having an opinion different to his own, and he has already taken a stance on the issue, and therefore cannot budge. Then the fanboys come along and stomp the conversation into the ground.

The nedu test explanation, his interpretation of it, and its non-connection to tech and lack of representation of deeper stops or VPM is a prime example. Look at all the BS that he and the fanboys have generated to create a cover story on that one.

.

Ok, then name a valid point you feel he has dismissed and stick with that issue, maybe someone else thinks the same thing has been overlooked and will chime in. Look for more data that supports your position and put it out there. Butting heads is certainly not productive and looks like a strategy of attrition, the gravity of this subject certainly deserves more than that...

 

[rossh]

Ok, then name a valid point you feel he has dismissed and stick with that issue, maybe someone else thinks the same thing has been overlooked and will chime in. Look for more data that supports your position and put it out there. Butting heads is certainly not productive and looks like a strategy of attrition, the gravity of this subject certainly deserves more than that...

Ok, Go with Don's dive here....

In post #33, I showed how he ascended 400ft, and experienced 3+ ATA supersaturation for the last part of the ascent, and continued to sustain this extreme level for the adjacent stops. i.e. up to 10 mins, up to and over 3 ATA. No human can tolerate this level of abuse - the physics of bubble growth can calculate how this affects us.

Huge profile abuse, and a big DCS to match, that became symptomatic even before the diver was half way done.

This profile planning failure is a consequence of ZHL being way beyond its useful range and 60/x being far too shallow to work at this depth. Only bubble models have the required math to be able to calculate safe ascents from these depths.

Deep stops are essential in this dive, because they lower the supersaturation stress to a tolerable amount.

This dive demonstrates a simple truth of decompression - ascend too far and no amount of follow on decompression time will save you.

We have clear records of these real deep dives done successfully, and they all involve much less ascent than shown here. i.e. deeper stops. In GF terms, the worst was a 40/x, but many are 30ish/x. (that little GF reduction removes 100+ft from the ascent distance).

This dive of Don's is unique in it ascent length (supersaturation) and elevated supersaturation duration. Given that these dimensions and pressures are the very basis of every decompression stress and DCS, it seems hard to overlook them as being anything but the primary issue here.


*******

What did Simon say? here

"Ross exhibits a profound level of ignorance of.... blah blah...blah".

Followed by several paragraphs of noise and personal attacks on my intelligence, and intentions.... he makes up fantasy opposing DCS issues, and tries to turn it into another anti-VPM argument. i.e. A smoke screen to avoid the obvious....

Simon might not know how to plan deep, but one thing is obvious in this dive... Humans will never be able to tolerate such profile abuse.

If Simon was honest, he would say / acknowledge / agree that there was a clear problem with the ascent length - too far, too long, too much supersaturation, and the corrective action is deeper stops. But then that would contradict his previous advise on dive planning.


*****

Some of the fanboys have tried to stomp all over this too, with less than realistic alternate suggestions.


****

Go ahead... tell me why that is wrong, and provide a plausible realistic alternate solution.

 

[Simon Mitchell]

Simon highlights my point perfectly.....

The lead scientist was Wayne Gerth, who presented his version at UHMS and DAN conferences in 2008. By that time, the test had served its purpose within the USN. The new USN dive manual version 6 (2008) was updated to a new set of model and tables, and it was all over.

Then 3 years later, David produced the 2011 re-formatted public report version....

Actually Ross, David, Wayne, and Keith Gault authored the 2011 report, which contains many things you don't like and which you are trying to denigrate and attribute primarily to David. Are you implying that these other authors allowed their name to go on an official US Navy scientific report that they did not fully agree with?

And do you not understand what NEDU TR11-06 means? It means this is the definitive US Navy Technical Report. Not a "re-formatted public report version" as you categorically and (yet again) incorrectly state. Indeed, somehow in your twisted logic you are suggesting that the paper appearing in the proceedings of a public conference is the official US Navy version, and the technical report published by NEDU is somehow the public version. Why do you continue to make yourself look stupid by categorically stating things that are so demonstrably wrong?

I suspect you had been scheming for this

More conspiracy theories. Do you see my name on the report? Are you accusing NEDU of being complicit in some Machiavellian attempt by a non-employee to spread misinformation about decompression practice into the wider diving community?

...since the whole thing was a non starter flop in front of your peers at the 2008 UHMS/DAN conferences, and failed to get any traction in the public.

You seem to have strong recollections of a conference that you did not even attend. The conference took place at the peak of obsessional belief in deep stops and bubble models, and was attended by a large number of divers and comparatively few of my "peers" as you put it. There was no voting paradigm employed that ensured that only scientists (my peers) voted on the issues discussed, and you are the only person on the planet who tries to characterise the proceedings as reflective of the views of a scientific peer group. Under the circumstances of the meeting, it was a miracle that any vaguely objective finding could be derived, but the consensus to the effect that there was uncertainty over the value of deep stops was a hugely radical departure from the received wisdom of the era. If the workshop was held again today after the emergence of further evidence, and confined to scientists, the result would be substantially more guarded on the use of bubble model style deep stops.

So you needed to do the "direct to public" approach, which is what you have been doing ever since.

Actually Ross, there was no "direct to the public approach until you started your misinformed attacks on the study on Rebreatherworld. In fact, it is your efforts that have made this into such a big issue. Your sustained and increasingly bizarre attacks on a growing body of scientific evidence, all to protect a commercial product, have necessitated a defence that makes the whole issue seem far more polarized than it really is.

In any case, you have interpreted and used the nedu test, way outside the consensus position of your peers in 2008.

I have been extremely careful never to interpret and use the NEDU study in any way that its authors would not agree with, which is why they have never disagreed with me.

You don't have the science on your side for this one.

Actually Ross, I have all the science on my side. That is why I take the positions I do. I simply follow the evidence. I have previously linked you to articles I wrote in the early 2000s extolling the virtues of deep stops at a time when we all believed in the logic - interestingly, similar to the logic you are applying in analysing Don's dive. Then proper human studies began to appear and all of them suggest the same thing. I am simply following the evidence. You accuse me of having an agenda, but my only agenda is to defend the evidence base of our field against poorly informed attacks by you.

You better get used to this Simon and cross your fingers, because you pushed the world into this new direction based on your personal preference, and without a valid science reason behind it.

How many times do others who have closely followed these discussions over the years have to tell you that I did not recommend what Don did, and the personal preferences I have cautiously articulated are not what Don did. I don't think you will get much sympathy from the diving community if you try to blame every episode of DCS that occurs in dives using non-bubble model approaches on me; any more than I would expect to gain traction by blaming all DCS occurring during use of VPM on you. It would be a ridiculous position.

This dive demonstrates a simple truth of decompression - ascend too far and no amount of follow on decompression time will save you.

Ah, at last something we can agree on. Of course this is true in principle. In a related vein....

If Simon was honest, he would say / acknowledge / agree that there was a clear problem with the ascent length - too far, too long, too much supersaturation, and the corrective action is deeper stops. But then that would contradict his previous advise on dive planning.

No it wouldn't. Don's plan was not based on my previous advice - which multiple commentators on this thread have quoted to you. But it seems that the truth is not going to stop you dishonestly trying to imply that Don was following a plan prescribed by me. I doubt you will win many intelligent followers by trying to do this.

Being honest as you request, deeper stops more confluent with my previous advice on this subject, may have prevented Don's event, but perhaps not. We have no way of knowing for sure. If you wanted to answer this question you would have to do a proper study with a large number of subjects, and as we have found in relation to deep stops these studies frequently produce surprising results.

Simon M

 

[DSix36]

Ok, Go with Don's dive here....

In post #33, I showed how he ascended 400ft, and experienced 3+ ATA supersaturation for the last part of the ascent, and continued to sustain this extreme level for the adjacent stops. i.e. up to 10 mins, up to and over 3 ATA. No human can tolerate this level of abuse - the physics of bubble growth can calculate how this affects us.

Huge profile abuse, and a big DCS to match, that became symptomatic even before the diver was half way done.

This profile planning failure is a consequence of ZHL being way beyond its useful range and 60/x being far too shallow to work at this depth. Only bubble models have the required math to be able to calculate safe ascents from these depths.

Deep stops are essential in this dive, because they lower the supersaturation stress to a tolerable amount.

This dive demonstrates a simple truth of decompression - ascend too far and no amount of follow on decompression time will save you.

We have clear records of these real deep dives done successfully, and they all involve much less ascent than shown here. i.e. deeper stops. In GF terms, the worst was a 40/x, but many are 30ish/x. (that little GF reduction removes 100+ft from the ascent distance).

This dive of Don's is unique in it ascent length (supersaturation) and elevated supersaturation duration. Given that these dimensions and pressures are the very basis of every decompression stress and DCS, it seems hard to overlook them as being anything but the primary issue here.


*******

What did Simon say? here

"Ross exhibits a profound level of ignorance of.... blah blah...blah".

Followed by several paragraphs of noise and personal attacks on my intelligence, and intentions.... he makes up fantasy opposing DCS issues, and tries to turn it into another anti-VPM argument. i.e. A smoke screen to avoid the obvious....

Simon might not know how to plan deep, but one thing is obvious in this dive... Humans will never be able to tolerate such profile abuse.

If Simon was honest, he would say / acknowledge / agree that there was a clear problem with the ascent length - too far, too long, too much supersaturation, and the corrective action is deeper stops. But then that would contradict his previous advise on dive planning.


*****

Some of the fanboys have tried to stomp all over this too, with less than realistic alternate suggestions.


****

Go ahead... tell me why that is wrong, and provide a plausible realistic alternate solution.

Why can't you just say a deeper first stop? If I were to run something like 30/70 for the profile my first stop would be around 300' and that would put my deep stop at 450'. There is no way that I want to linger at 450' and continue to on gas

 

[Jeff Pack]

You ongas, but lessen the saturation level by ascending slower. Its a double edged sword.

 

[rossh]

Why can't you just say a deeper first stop? If I were to run something like 30/70 for the profile my first stop would be around 300' and that would put my deep stop at 450'. There is no way that I want to linger at 450' and continue to on gas

Instead of saying "first stop depth", which locks us into some hard dimension, I'm describing this as the distance ascended up to the first stop. That gives up a direct relation to the supersaturation experienced.

For these deep dives, a 60/x plan is about 400ft of ascent, a 40/x has about 350ft of ascent, a 25/x has 320ft, 15/x is about 290ft. The further one ascends, the longer the time frame at high supersaturation, and the longer the high levels persist during the subsequent stops.

So while the ascent difference in a 60/x vs a 30/x is 70 ft, it increases SS pressure by up to 1 ATA (3.2 vs 2.2), for a further 6 mins (1 min extra ascent, 5 mins of initial stops).


You can't have your cake, and eat it too. If you want to avoid seeding an immediate excess supersaturation injury (DCS), then you have to stop ascent and wait, and accept its creating further on-gas to be dealt with later on. This is generic problem in every dive we do (all models, all deco types, all depths). It gets exaggerated here with really deep dives.

.

 

[rossh]

Actually Ross, David, Wayne, and Keith Gault authored the 2011 report, which contains many things you don't like and which you are trying to denigrate and attribute primarily to David. Are you implying that these other authors allowed their name to go on an official US Navy scientific report that they did not fully agree with?

And do you not understand what NEDU TR11-06 means? It means this is the definitive US Navy Technical Report. Not a "re-formatted public report version" as you categorically and (yet again) incorrectly state. Indeed, somehow in your twisted logic you are suggesting that the paper appearing in the proceedings of a public conference is the official US Navy version, and the technical report published by NEDU is somehow the public version. Why do you continue to make yourself look stupid by categorically stating things that are so demonstrably wrong?



More conspiracy theories. Do you see my name on the report? Are you accusing NEDU of being complicit in some Machiavellian attempt by a non-employee to spread misinformation about decompression practice into the wider diving community?



You seem to have strong recollections of a conference that you did not even attend. The conference took place at the peak of obsessional belief in deep stops and bubble models, and was attended by a large number of divers and comparatively few of my "peers" as you put it. There was no voting paradigm employed that ensured that only scientists (my peers) voted on the issues discussed, and you are the only person on the planet who tries to characterise the proceedings as reflective of the views of a scientific peer group. Under the circumstances of the meeting, it was a miracle that any vaguely objective finding could be derived, but the consensus to the effect that there was uncertainty over the value of deep stops was a hugely radical departure from the received wisdom of the era. If the workshop was held again today after the emergence of further evidence, and confined to scientists, the result would be substantially more guarded on the use of bubble model style deep stops.



Actually Ross, there was no "direct to the public approach until you started your misinformed attacks on the study on Rebreatherworld. In fact, it is your efforts that have made this into such a big issue. Your sustained and increasingly bizarre attacks on a growing body of scientific evidence, all to protect a commercial product, have necessitated a defence that makes the whole issue seem far more polarized than it really is.



I have been extremely careful never to interpret and use the NEDU study in any way that its authors would not agree with, which is why they have never disagreed with me.



Actually Ross, I have all the science on my side. That is why I take the positions I do. I simply follow the evidence. I have previously linked you to articles I wrote in the early 2000s extolling the virtues of deep stops at a time when we all believed in the logic - interestingly, similar to the logic you are applying in analysing Don's dive. Then proper human studies began to appear and all of them suggest the same thing. I am simply following the evidence. You accuse me of having an agenda, but my only agenda is to defend the evidence base of our field against poorly informed attacks by you.


How many times do others who have closely followed these discussions over the years have to tell you that I did not recommend what Don did, and the personal preferences I have cautiously articulated are not what Don did. I don't think you will get much sympathy from the diving community if you try to blame every episode of DCS that occurs in dives using non-bubble model approaches on me; any more than I would expect to gain traction by blaming all DCS occurring during use of VPM on you. It would be a ridiculous position.



Ah, at last something we can agree on. Of course this is true in principle. In a related vein....



No it wouldn't. Don's plan was not based on my previous advice - which multiple commentators on this thread have quoted to you. But it seems that the truth is not going to stop you dishonestly trying to imply that Don was following a plan prescribed by me. I doubt you will win many intelligent followers by trying to do this.

Being honest as you request, deeper stops more confluent with my previous advice on this subject, may have prevented Don's event, but perhaps not. We have no way of knowing for sure. If you wanted to answer this question you would have to do a proper study with a large number of subjects, and as we have found in relation to deep stops these studies frequently produce surprising results.

Simon M

You have to stop this assumption of yours, that you have this body of evidence. None of your peers have agreed to the same... Most of those studies, do not support your position. You are playing word games on the public to create a false impression. I went through your list and debunked it over here.


You won't accept the value of the physics, on such an extreme dive, without a controlled test? Instead you want to re-confirm the basic components of every DCS?

And yes, there is data on these dives done successfully, and a quick review reveals why Don's dive is the exception.

If someone arrived at the chamber and said... "I blew through half my stops, and now I can't walk straight..." what would be the diagnosis, and what might be the most logical initiating cause?

.

 

[silent running]

You ongas, but lessen the saturation level by ascending slower. Its a double edged sword.

Yes, but the question is how sharp is the sword?

I remember when using lift bags to speed up ascent was a legitimate practice. Somewhere between that and my Naui bubble model trimix class, ascent rates were slowed significantly to the point of zen practice. My suspicion is that accent rates should be fast to the first deepish stop, then slower to the next longer stop, etc. Sounds like a compromise between bubble models and Buhlman, what a surprise. But what do I or any of us know for sure? Not enough..!

 

[Simon Mitchell]

You have to stop this assumption of yours, that you have this body of evidence. None of your peers have agreed to the same

That's an odd thing to say when the only body of published human evidence that exists on this subject (see below) was written by my peers (not me) and all of it supports my fundamental position. Furthermore, it was my peers who decided that the US Navy would not routinely adopt bubble models. Sounds like agreement to me. ​

Blatteau JE, Hugon M, Gardette B, Sainty J-M, Galland F-M. Bubble incidence after staged decompression from 50 or 60 msw: effect of adding deep stops. Aviat Space Environ Med 2005;76:490–2.

Doolette DJ. Gerth WA, Gault KA. Redistribution of decompression stop time from shallow to deep stops increases incidence of decompression sickness in air decompression dives. NEDU TR 11-06. 2011.

Enzo Spisni, Claudio Marabotti, Luigia De Fazio, Maria Chiara Valerii, Elena Cavazza, Stefano Brambilla,
Klarida Hoxha, Antonio L’Abbate and Pasquale Longobardi. A comparative evaluation of two decompression procedures for technical diving using inflammatory responses: compartmental vs ratio deco. Diving Hyperbaric Med 2017;47(1):9-16.

I went through your list and debunked it over here.

You have not debunked anything no matter what you think.

You won't accept the value of the physics, on such an extreme dive, without a controlled test? Instead you want to re-confirm the basic components of every DCS?

I am not defending the decompression Don did. As has been pointed out to you multiple times, it is not what I have indicated as the optimal response to the available data. However, my point about the "controlled test" is that you cannot confidently draw inference about optimal decompression practice from the outcome of one dive. You are essentially trying to claim that Don's outcome vindicates your position on deep stops across the board which, in the context of our available evidence is almost certainly nonsense. You can't even confidently claim that his decompression would be wrong for a wider group of divers doing the same dive. It might be, but to establish that you would have to do a study.

You forget that it was exactly the sort of arguments you are making here that led us down the deep stops path years ago. Divers would get bent, Doppler studies showed that divers were forming bubbles, and it seemed immutably logical that performing deeper stops would control bubbles and reduce the incidence of DCS. Everyone started doing it. Then there was formal testing of the effect of distributing stops deeper on standardised dives of equal length and, unexpectedly, there were more bubbles and more DCS in the deeper stop dives. The verdict of the diving medicine community (which I have not seen challenged anywhere to date) is that this is explained by greater slower tissue supersaturation later in the ascent after deep stops. There is an unmistakable signal in the literature that we should be backing off deep stops as prescribed by bubble models. As I have said many many times, the problem is I can't tell you how far we should back off, and therefore we should do it cautiously. I have always been scrupulously honest about this. Maybe Don backed off too far, but the conclusion you want to draw about the implications for the wider debate about deep stops is simply not supported.

You keep ignoring the fact that plenty of divers have been seriously injured during your favoured deep stop decompressions from very deep dives. How do you explain that? Do you think if I put one of Ellyat's case histories up here that would constitute proof that deep stops are bad? I have never aggressively sold that line because I know it would be bad science.

If someone arrived at the chamber and said... "I blew through half my stops, and now I can't walk straight..." what would be the diagnosis, and what might be the most logical initiating cause

If they blew through half their stops when using a validated algorithm for the depth they were diving at then it would certainly increase suspicion of DCS and omitted decompression would be a likely cause. But Don was neither using a validated algorithm nor did he blow through half his stops. I would not know how to interpret his decompression but since DCS is a clinical diagnosis and he was exhibiting classical signs after a decompression dive, I would have got the diagnosis right!

Simon M

 

[rossh]

That's an odd thing to say when the only body of published human evidence that exists on this subject (see below) was written by my peers (not me) and all of it supports my fundamental position. Furthermore, it was my peers who decided that the US Navy would not routinely adopt bubble models. Sounds like agreement to me. ​

Blatteau JE, Hugon M, Gardette B, Sainty J-M, Galland F-M. Bubble incidence after staged decompression from 50 or 60 msw: effect of adding deep stops. Aviat Space Environ Med 2005;76:490–2.

Doolette DJ. Gerth WA, Gault KA. Redistribution of decompression stop time from shallow to deep stops increases incidence of decompression sickness in air decompression dives. NEDU TR 11-06. 2011.

Enzo Spisni, Claudio Marabotti, Luigia De Fazio, Maria Chiara Valerii, Elena Cavazza, Stefano Brambilla,
Klarida Hoxha, Antonio L’Abbate and Pasquale Longobardi. A comparative evaluation of two decompression procedures for technical diving using inflammatory responses: compartmental vs ratio deco. Diving Hyperbaric Med 2017;47(1):9-16.



You have not debunked anything no matter what you think.



I am not defending the decompression Don did. As has been pointed out to you multiple times, it is not what I have indicated as the optimal response to the available data. However, my point about the "controlled test" is that you cannot confidently draw inference about optimal decompression practice from the outcome of one dive. You are essentially trying to claim that Don's outcome vindicates your position on deep stops across the board which, in the context of our available evidence is almost certainly nonsense. You can't even confidently claim that his decompression would be wrong for a wider group of divers doing the same dive. It might be, but to establish that you would have to do a study.

You forget that it was exactly the sort of arguments you are making here that led us down the deep stops path years ago. Divers would get bent, Doppler studies showed that divers were forming bubbles, and it seemed immutably logical that performing deeper stops would control bubbles and reduce the incidence of DCS. Everyone started doing it. Then there was formal testing of the effect of distributing stops deeper on standardised dives of equal length and, unexpectedly, there were more bubbles and more DCS in the deeper stop dives. The verdict of the diving medicine community (which I have not seen challenged anywhere to date) is that this is explained by greater slower tissue supersaturation later in the ascent after deep stops. There is an unmistakable signal in the literature that we should be backing off deep stops as prescribed by bubble models. As I have said many many times, the problem is I can't tell you how far we should back off, and therefore we should do it cautiously. I have always been scrupulously honest about this. Maybe Don backed off too far, but the conclusion you want to draw about the implications for the wider debate about deep stops is simply not supported.

You keep ignoring the fact that plenty of divers have been seriously injured during your favoured deep stop decompressions from very deep dives. How do you explain that? Do you think if I put one of Ellyat's case histories up here that would constitute proof that deep stops are bad? I have never aggressively sold that line because I know it would be bad science.


If they blew through half their stops when using a validated algorithm for the depth they were diving at then it would certainly increase suspicion of DCS and omitted decompression would be a likely cause. But Don was neither using a validated algorithm nor did he blow through half his stops. I would not know how to interpret his decompression but since DCS is a clinical diagnosis and he was exhibiting classical signs after a decompression dive, I would have got the diagnosis right!

Simon M

None of those papers confirm or support your position. You deliberately quote them out of context, and then you assume they support you. You do this without review or peer support. But, using valid science, you have been shown many times where your mistakes are, and why the papers don't support you. But you ignore all that, because it interferes with your agenda. You are a bully on a campaign.


You are still trying to bullshit us with misquoting VGE and DCS risk out of context, by mixing up intravascular and extravascular micro-bubble growth. The mere fact that you - a medical doctor, keep making this mistake, demonstrates that the deceptions and lies in your position and points, are intentional.


VPM-B is the most successful decompression strategy we have seen. Since its introduction in 2003, the DCS injury rates / numbers / have been in decline for over a decade. Its also still the most accurate stand alone model we have to date.


*************

My claim on Don's dive, is it tests and demonstrates a complete failure of your "new, more efficient" deco methods. The omission of deeper stops caused the injury.

You have been endorsing that new approach, and pushing people away from the deeper stops. You are partially at fault here, and will be partially responsible for more to come.... You have set people on this new course, so face up to the results.

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[se2schul]

You have been endorsing that new approach, and pushing people away from the deeper stops. You are partially at fault here, and will be partially responsible for more to come.... You have set people on this new course, so face up to the results.

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Unreal. Just unreal. Since when have people not been 100% responsible for their own choices - especially for a high-risk activity and when every known decompression model has a certain incidence of DCS associated with it? And especially when doing what can only be described as an extremely deep dive that pushes the limits of sport (tech) diving.

It's one thing to debate ideas, question studies, even question one's ulterior motives, but blaming anyone other than Don for his injuries is just insane. Should you take blame for every diver injured after using a VPM profile? I sure hope not, and suggesting that you are to blame for something like that is short sighted and just absolutely classless.

 

[rossh]

Unreal. Just unreal. Since when have people not been 100% responsible for their own choices - especially for a high-risk activity and when every known decompression model has a certain incidence of DCS associated with it? And especially when doing what can only be described as an extremely deep dive that pushes the limits of sport (tech) diving.

It's one thing to debate ideas, question studies, even question one's ulterior motives, but blaming anyone other than Don for his injuries is just insane. Should you take blame for every diver injured after using a VPM profile? I sure hope not, and suggesting that you are to blame for something like that is short sighted and just absolutely classless.

Simon has been advocating that deeper stops are not necessary. In a few post's he even called them a fad..... Oops... looks like he was wrong. He has been using his influence and professional and privileged position to push that "new, more efficient" deco approach onto many people who just take it all at face value.

But is it your suggestion that we should ignore him then? Sounds fine to me.

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[cathal]

At what point does a forum moderator step in to put us all out of our misery with this. No matter what evidence is presented, no matter who presents it or how much of it is presented Ross is never going to accept that his view goes against modern medicine. The only benefit we as a community get out of these debates is the very public corrections to his view clearly and patiently set out by scientists in this area such as Simon. Otherwise all I see is a devaluing of the integrity of this forum.