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

[Patoux01]

Ah well, here we go again.

 

[UWSojourner]

For links and discussion of GF and VPM and their relative similarities to the dives performed in the NEDU study, see here.

In addition, this post and this post is helpful as well.

I know I've posted these before, but when the same snake oil keeps being sold, these links are appropriate to repost.

 

[rossh]

For links and discussion of GF and VPM and their relative similarities to the dives performed in the NEDU study, see here.

In addition, this post and this post is helpful as well.

And for those who would like to see the issue discussed, without all the trolls interference and their marketing fluff:

The back half of this thread.

 

[PfcAJ]

And for those who would like to see the issue discussed, without all the paid trolls interference and their marketing fluff:

The back half of this thread.

theres only one guy who has anything to market and that gets paid from successful marketing in these threads.

 

[Dr Simon Mitchell]

1/ If helium is no longer the culprit causing DCS, then what is causing us the DCS that is to be avoided ??? Are they now suggesting that DCS is no longer caused by excessive gas pressure stresses, but instead now its being caused by other (external) influences like cold, or physical activity stresses, or what?? Are they suggestion He now has non-linear kinetic rates with pressure changes?

When we pressed Simon and David on this issue, they respectfully declined to answer, or clarify this conundrum.

Who is the "we" in this Ross? I think you mean "I" don't you? If you want to know what causes DCS just go to the chapters I wrote on the subject in Bennett and Elliott's Physiology and Medicine of Diving or the latest edition of Diving and Subaquatic Medicine (you claim to have both books). Current understanding of the subject based on the best published data available (at the respective times of publishing) is clearly articulated those documents. Nothing I have said in any of the on-line debates we have been compelled to have in order to prevent you perpetuating your "anti-knowledge" agenda contradicts what I have said in those chapters .

And for those who would like to see the issue discussed, without all the paid trolls interference and their marketing fluff:

The back half of this thread.

The only difference between that thread and the most comprehensive one on Rebreather World is that no one ran a poll at the end of it to demonstrate the virtually universal rejection of your arguments amongst readers of the thread.

Simon M

 

[rossh]

1/ If helium is no longer the culprit causing DCS, then what is causing us the DCS that is to be avoided ??? Are they now suggesting that DCS is no longer caused by excessive gas pressure stresses, but instead now its being caused by other (external) influences like cold, or physical activity stresses, or what?? Are they suggestion He now has non-linear kinetic rates with pressure changes? When we pressed Simon and David on this issue, they respectfully declined to answer, or clarify this conundrum.

Who is the "we" in this Ross? I think you mean "I" don't you? If you want to know what causes DCS just go to the chapters I wrote on the subject in Bennett and Elliott's Physiology and Medicine of Diving or the latest edition of Diving and Subaquatic Medicine (you claim to have both books). Current understanding of the subject based on the best published data available (at the respective times of publishing) is clearly articulated those documents. Nothing I have said in any of the on-line debates we have been compelled to have in order to prevent you perpetuating your "anti-knowledge" agenda contradicts what I have said in those chapters . Simon M

Look at you - using semantics and avoiding the question... again. Oh and throw in a couple of insults while you're at it. Aren't you clever.



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



You and David's new concept is that helium kinetics are different to what has been known in the past. You say / imply that deco models may therefore be wrong with respect to helium. But when pressed to explain how that might be, you give us some double speak


"...both David and I have said that we may be doing the right amount of deco, just for the wrong reasons..."
"...We have been diving deep using helium and assuming a "helium penalty" which has lengthened the decompressions. It may be that the amount of decompression we have been doing is simply what is required for diving deep irrespective of the inert gas you use...."



Go ahead now Simon - please explain:

1/ If its not the helium gas pressure stress (as you imply) causing the DCS, then what is causing us DCS at these depths?

2/ How has 40+ years of decompression model testing and tables and theory, somehow been wrong all this time?

The only difference between that thread and the most comprehensive one on Rebreather World is that no one ran a poll at the end of it to demonstrate the virtually universal rejection of your arguments amongst readers of the thread. Simon M

Oh yes, you won the marketing and popularity contest. Congratulations.

That wasn't hard to do when many of your talking points where stretched out half truths, back by faked graphs and made up measures, and fabricated comparison points and junk science. You used two business marketing / advertising experts as trolls to push the message along. Interesting that you put more value on public "popularity" ahead of science.


Here are some facts you stomped on along the way: There are no deep stops in the nedu test (here). The VPM CR compare you presented was a stretched out exaggeration that is fake, the +7 is also totally faked up invention of the marketing troll, just like the mb-mins invention is junk science and has no deco validation or justification (and in reality, it works backwards). The heat graphs in that thread are meaningless advertising eye candy. Someone posted a stretched out faked up RGBM dive profile to compare to the nedu test as well. Marketing fluff, advertising methods, junk science and more... so you could win your popularity contest.......


Simon's claimed "plausible explanation" 3 key points were shown to be invalid or wrong here here here here here here.


And what was the outcome of all that... GF 40/70.... which is still a deep (deeper) stop approach and often the same or similar to a VPM-B profile. What a bunch of hypocrites you lot are.


**********

A better discussion of this was round 2, in the back half of this thread - no paid trolls in this one.

 

[ajduplessis]

theres only one guy who has anything to market and that gets paid from successful marketing in these threads.

So whats wrong with that? Pretty obvouis the half truths are not going to make any $$$ soon.

 

[Dr Simon Mitchell]

You and David's new concept...

Can I be clear that the original animal and human research into helium vs nitrogen kinetics that has sparked the various threads was done by David Doolette (and his colleagues), not me. I would love to have my name attached to this work, but it is not mine. However, as a scientist with a strong interest in the field I find myself in the position of defending these rare examples of well designed original research in our field from misguided and poorly informed attack by someone with a probable financial motive to discredit the results.

You say / imply that deco models may therefore be wrong with respect to helium. But when pressed to explain how that might be, you give us some double speak

"...both David and I have said that we may be doing the right amount of deco, just for the wrong reasons..."
"...We have been diving deep using helium and assuming a "helium penalty" which has lengthened the decompressions. It may be that the amount of decompression we have been doing is simply what is required for diving deep irrespective of the inert gas you use...."

Go ahead now Simon - please explain:

1/ If its not the helium gas pressure stress (as you imply) causing the DCS, then what is causing us DCS at these depths?

Which parts of the "double speak" answers above imply that helium "gas pressure stress" does not cause DCS when diving deep and breathing helium? That interpretation of the message is bordering on bizarre.

Let me try to lay it out for you. David's animal work suggests there is little or no difference in helium and nitrogen kinetics in tissues whose gas exchange properties are likely to be of significance to causation of DCS in decompression from deep bounce dives . His recent study in humans corroborates this finding. A natural question divers are now asking is "if helium and nitrogen kinetics are not different, does it matter what inert gas I tell my computer that I am breathing? In particular, based on assumptions about helium kinetics my decompression algorithm penalises me for using more helium. I should now (based on this work) be able to tell it that I am breathing only nitrogen and therefore have less decompression but still be safe".

We are saying no, don't do that, because although the assumptions about helium kinetics are probably wrong, it may be that the penalty imposed for using helium has serendipitously resulted in adequate decompressions from deep dives where helium is typically used. Put another way, setting aside obvious issues with narcosis and density, even if you really did use nitrogen for a deep dive, it may be that you really should be using the decompression procedure prescribed for a helium dive with its assumed penalty. Put yet another way, deep dives may require more decompression irrespective of the inert gas used, and the "helium penalty" has serendipitously resulted in us performing about the right amount of decompression in most cases. As you know, David presented evidence supporting such a scenario on the CCRX thread.

How has 40+ years of decompression model testing and tables and theory, somehow been wrong all this time?

It is very disingenuous to post this here given that it has been explained to you multiple times on the other thread. Effectively no decompression model testing set out to answer the question we are debating here by doing what David did; a head to head comparison of dive outcomes when helium and nitrogen were dived on identical time and depth profiles. Yes, some deep helium deep bounce diving profiles have been tested and empirically adjusted over the years, and yes divers have used deep helium profiles with acceptable success rates. But this proves nothing about relative helium and nitrogen kinetics, or whether a "helium penalty" is necessary because of different inert gas kinetics.

That wasn't hard to do when many of the talking points where stretched out half truths, back by faked graphs and made up measures, and fabricated comparison points and junk science.

It must have been quite a burden being the only reader of a thread visited 95,000 times who was smart enough to figure all this out.

...no paid trolls in this one.

Just for the record, can you please tell us who these trolls were, and who "paid" them?

Simon M

 

[rossh]

Can I be clear that the original animal and human research into helium vs nitrogen kinetics that has sparked the various threads was done by David Doolette (and his colleagues), not me. I would love to have my name attached to this work, but it is not mine. However, as a scientist with a strong interest in the field I find myself in the position of defending these rare examples of well designed original research in our field from misguided and poorly informed attack by someone with a probable financial motive to discredit the results.



Let me try to lay it out for you. David's animal work suggests there is little or no difference in helium and nitrogen kinetics in tissues whose gas exchange properties are likely to be of significance to causation of DCS in decompression from deep bounce dives . His recent study in humans corroborates this finding. A natural question divers are now asking is "if helium and nitrogen kinetics are not different, does it matter what inert gas I tell my computer that I am breathing? In particular, based on assumptions about helium kinetics my decompression algorithm penalises me for using more helium. I should now (based on this work) be able to tell it that I am breathing only nitrogen and therefore have less decompression but still be safe".

We are saying no, don't do that, because although the assumptions about helium kinetics are probably wrong, it may be that the penalty imposed for using helium has serendipitously resulted in adequate decompressions from deep dives where helium is typically used. Put another way, setting aside obvious issues with narcosis and density, even if you really did use nitrogen for a deep dive, it may be that you really should be using the decompression procedure prescribed for a helium dive with its assumed penalty. Put yet another way, deep dives may require more decompression irrespective of the inert gas used, and the "helium penalty" has serendipitously resulted in us performing about the right amount of decompression in most cases. As you know, David presented evidence supporting such a scenario on the CCRX thread.



It is very disingenuous to post this here given that it has been explained to you multiple times on the other thread. Effectively no decompression model testing set out to answer the question we are debating here by doing what David did; a head to head comparison of dive outcomes when helium and nitrogen were dived on identical time and depth profiles. Yes, some deep helium deep bounce diving profiles have been tested and empirically adjusted over the years, and yes divers have used deep helium profiles with acceptable success rates. But this proves nothing about relative helium and nitrogen kinetics, or whether a "helium penalty" is necessary because of different inert gas kinetics.

Simon M

Well thank you for the answer and clarifying your position. That wasn't so hard after all.

David didn't talk much about things connected to tech diving (or explain the above). In fact he shied away from the question. But he did stomp all over the DCIEM tables. I think if the original DCIEM people were still around, David might have a harder time of getting away with such negativity.

I find myself in the position of defending these rare examples of well designed original research in our field from misguided and poorly informed attack by someone with a probable financial motive to discredit the results.

Simon M

I haven't done any of that Simon. It's your vivid imagination and wishful thinking at play - trying to invent an argument with me out of nothing - again.


***********

I will make this promise - if science can come up new real data, backed up with some full rounded theory, peer reviewed new decompression model design, then I will put it in MultiDeco for everyone to enjoy. Get to it.

 

[David Doolette]

But he did stomp all over the DCIEM tables. I think if the original DCIEM people were still around, David might have a harder time of getting away with such negativity.

I see you moved almost immediately to posting lies and pretence. Here is a direct quote of mine from CCRexplorers: "Continuing to use the DCIEM tables as an example, because these are well-tested and relatively modern, if you compare the air with in-water oxygen and heliox with in-water oxygen decompression tables, you will see, as has been noted in this thread, that the heliox schedules are about 50% longer than the corresponding air schedules." I went on to explain that this difference is totally appropriate, but not because helium and nitrogen have different decompression requirements. As to the "original DCIEM people", like much else you write, you have no idea what you are talking about. Ron Nishi, the lead scientist who developed the DCIEM tables, and I just finished writing a paper together.

I will make this promise - if science can come up new real data, backed up with some full rounded theory, peer reviewed new decompression model design, then I will put it in MultiDeco for everyone to enjoy. Get to it.

The implication that there are not already well-validated alternatives to the algorithms in Multideco is absurd.


---------- Post added December 19th, 2015 at 12:19 PM ----------

It's a question for Doolette and Mitchell to answer (which they have avoided doing). They have proposed that helium is not what its seems, have said some vague things about why existing deco times might be incorrect in certain ways, but correct in others ways for different reasons, but have not explained the reasons behind that. All too vague I think. When pressed they skipped the answers.

...and misinformation. Rather than evading your questions, as you are trying to imply, I have already answered them. Some direct quotes of specific explanations I wrote on CCRexplorers:

“I have been using "helium penalty" to mean the prescription of more decompression the more helium is in the breathing mixture, not necessarily to mean a penalty in the sense of prescribing an overly conservative decompression.”

“The prescription of a ‘helium penalty” by many decompression algorithms results from assumption of faster uptake of helium than nitrogen into fast half-time compartments, and therefore prescription of deeper first stops, and consequently longer decompressions, the more helium relative to nitrogen that is in the breathing mix.”

“I think a more appropriate structure is to have the half-times for nitrogen and helium the same in fast-compartments and nitrogen slower than helium in slow compartments. This is not revolutionary, I think DCAP has the half-times for nitrogen and helium the same for compartments with a 25-minute half-time and faster, and has them different in slower compartments. I am not sure if 25 minutes is the best break-point, but it could be. However, as has been cautioned before, decompression algorithms with a "helium penalty" might be prescribing the right amount of decompression for deeper dives, where more helium is used, but for the wrong reason (i.e. you might need that extra decompression whether you are breathing heliox, trimix, or nitrox).”

“deterministic decompression algorithms, such as ZH-L16, VPM, and the DCIEM decompression model do not explicitly control [probability of DCS] PDCS. Furthermore, different schedules prescribed by any such algorithm do not all have the same PDCS – longer or deeper dives have higher PDCS such that the PDCS increases in proportion with the amount of prescribed decompression. For instance, a dive to 40 msw for 40 minutes BT with decompression prescribed by any such algorithm has lower PDCS than a dive to 70 msw for 40 minutes BT with decompression prescribed by the same algorithm.”

“For relatively shallow dives, what I haven calling a "helium penalty" might indeed result in prescribing overly conservative decompression, but for relatively deep dives, what I have been calling a "helium penalty" might result in prescribing an appropriate amount of decompression”

There is a lot more supporting information over on that thread for those interested.

David Doolette