"re-assessing deco profiles and deep stops", plus other bits..

[drew b]

Simon,

You commented that you use GF with settings to detune deep stops. Are you willing to share the settings that you use and provide some thoughts behind your choice. Have you been changing incrementally over a period of time to the value used currently based on feeling after the dive or via some other method.

Thanks for anything you may wish to share.
Drew

 

[Bruce Partridge]

So why did the navy label it deep, when there was none? Why did the navy spin the load of BS about the reasons for cancelling this test? I understand they had to save face and this this project from failure, but the spin is not justified, and neither are the papers conclusions.

Regards rossh

Ross,

I think you will have to find another reason to justify your proposed conspiracy.

Wayne Gerth was a senior researcher on that project. At the 2001 NAUI Conference in Key West at the Combat Divers School, Wayne was a strong supporter of Deep Stops. He went so far as to say that the Navy needed to update their decompression schedules (not an exact quote.) From his presentation, and I still have my notes, there is no doubt in my mind that he believed in Deep Stops.

At a DAN conference, I believe in 2008, Wayne made a point of presenting at the conference and admitting to a diving science audience that he was wrong. "I have lost my religion."

As I interpret this sequence of events, he had convinced the Navy to perform a study to justify adding deep stops to their profiles. He was expecting the study to confirm his beliefs.

It did not, and he publicly admitted it.

How this can be interpreted as "saving face" requires some imagination.

Bruce

 

[rossh]

Ross,

I think you will have to find another reason to justify your proposed conspiracy.

Wayne Gerth was a senior researcher on that project. At the 2001 NAUI Conference in Key West at the Combat Divers School, Wayne was a strong supporter of Deep Stops. He went so far as to say that the Navy needed to update their decompression schedules (not an exact quote.) From his presentation, and I still have my notes, there is no doubt in my mind that he believed in Deep Stops.

At a DAN conference, I believe in 2008, Wayne made a point of presenting at the conference and admitting to a diving science audience that he was wrong. "I have lost my religion."

As I interpret this sequence of events, he had convinced the Navy to perform a study to justify adding deep stops to their profiles. He was expecting the study to confirm his beliefs.

It did not, and he publicly admitted it.

How this can be interpreted as "saving face" requires some imagination.

Bruce

Sure, my original post was a bit harsh.

As I understand it, the test methods that were finally used, were not those that Wayne asked for. This strange test sequence turned out to be rather unrelated to anything in tech diving. Many people in industry can see this, and don't give this study much time. But a handful want to hang onto it because of its title and conclusion, just for the shock value and to push their one sided arguments. That's not right.

 

[emmbee]

Ljubkovic M, Marinovic J, Obad A, Breskovic T, Gaustad SE, Dujic Z. High incidence of venous and arterial gas emboli at rest after trimix diving without protocol violations. J Appl Physiol 2010;109:1670-4.

Great Thanks for that

The paper

arterialisation of these bubbles after 9 out of 21 dives and in 5 out of 7 subjects

?

!

I'm thinking this is maybe significant for models.

A fundamental assumption behind the multiple compartment with exponential on/offgasing model (as used by Buhlmann, GFs, VPM, ...) is that the compartments are independent and directly connected to an infinite gas volume.

This seems reasonable (to me) because a) of the double tree structure of the vascular system, with the tissues joining the leaves and the lungs joining the trunks (ignoring the heart), b) the circulation and breathing cycles are much faster than the fastest compartment, and c) the lung is a close to perfect gas exchanger, "resetting" the blood to inhaled pressures. [And here's me failing physiology 101 ]. So in effect it's "as if" each partition of tissues (i.e compartment) had its own lung.

When bubbles get past the lungs, assumption c) becomes invalid, and so possibly does the model.

That's the way I see it, anyway.

Not only would compartments offgas slower on their own, but slower compartments offgasing would be hindered by the offgasing off the faster ones. In fact you could even get faster compartments (partially) offgasing into the slower ones.

Note that if this happens in the water, it may provide some justification for GFs (or other "deeper" stops), either to stop it, or to compensate. But not what GFs And I note, coincidence, that the paper mentions they didn't see arterialisation in another study with air (I haven't read that one), something people have traditionally been doing with high, if any, GFs.

Of course it is very possible that this is all negligible.

And even more that I'm just Wrong

FWIW.

Cheers,

Matthieu

 

[Simon Mitchell]

Simon,

You commented that you use GF with settings to detune deep stops. Are you willing to share the settings that you use and provide some thoughts behind your choice. Have you been changing incrementally over a period of time to the value used currently based on feeling after the dive or via some other method.

Thanks for anything you may wish to share.
Drew

Hello Drew,

I knew someone would ask this and I most definitely do not want to be seen to be providing recommendations.

However, I am happy to share aspects of my personal story. I was like Wayne Gerth in the early 2000s (as beautifully articulated by Bruce Partridge in his post). Everyone got caught up in the theoretical attraction of deep stop approaches to decompression. I used VPM for a period of time, and then gradient factors configured to mimic the bubble model approach to decompression (GFs ~ 20-90). I did over 500 hours on rebreathers using these approaches, including quite a number of dives over 100m and suffered no problems other than two episodes of musculoskeletal "niggles". In recent years as the deep stop issue has become controversial and the evidence we have been debating has emerged, I have altered my gradient factor approach and now use 35 - 75 on a Shearwater, or settings on Kev Gurr's VGM that produce similar profiles depending on which rebreather I am wearing. These changes have not been driven by perceptions of how I feel, but I have had no problems over a further 300 - 400 hours. I don't know whether this is right, but it seems to me to be an appropriate response to the current state of the available evidence. My decompressions are quite conservative, but I am often the only physician in very remote locations!

Simon M

 

[rossh]

When bubbles get past the lungs, assumption c) becomes invalid, and so possibly does the model.

That's the way I see it, anyway.

Not only would compartments offgas slower on their own, but slower compartments offgasing would be hindered by the offgasing off the faster ones. In fact you could even get faster compartments (partially) offgasing into the slower ones.

Note that if this happens in the water, it may provide some justification for GFs (or other "deeper" stops), either to stop it, or to compensate. But not what GFs And I note, coincidence, that the paper mentions they didn't see arterialisation in another study with air (I haven't read that one), something people have traditionally been doing with high, if any, GFs.

Of course it is very possible that this is all negligible.

And even more that I'm just Wrong

FWIW.

Cheers,

Matthieu

Hi, Yes I agree. Once a critical(??) amount of recirculation of microbubbles begins, then the model is no longer representative of the conditions. However I don't think its an area that needs to modeled further. I think instead its represents a boundary that should not be crossed i.e. the beginning of DCS.

I think the diver here has reached the safe limit of deco. He may also have reached the limit of the lungs capacity to filter off microbubbles, and a small amount is now starting to seep through to the arterial side.

Makes an interesting question.. Is a DCS event too many bubbles in the tissue that expanded too fast? Or the lung gets overwhelmed and too much gas recirculates to the arterial side where it gets trapped there?

Remember the PFO problem, where its thought that too many microbubbles will recirculate to the arterial side. This test I think is supporting that idea.

As I said before, it a great calibration point. We have the divers on the edge of normal OK deco, without injury, and we can see what's happening here. There a lot of interesting variations on this test that would add to knowledge.

 

[Hens]

I certainly cannot tell if deep-stops are good or wrong, just follow the algorithm and come out "clean"
But what I miss in this discussion is the possibility that the "wrong" deep-stops are corrected with the shallower stops generated by the algorithm

just my 2 cents

best regards
Hens

 

[Igor P]

Hi, Yes I agree. Once a critical(??) amount of recirculation of microbubbles begins, then the model is no longer representative of the conditions. However I don't think its an area that needs to modeled further. I think instead its represents a boundary that should not be crossed i.e. the beginning of DCS.

I think the diver here has reached the safe limit of deco. He may also have reached the limit of the lungs capacity to filter off microbubbles, and a small amount is now starting to seep through to the arterial side.

Makes an interesting question.. Is a DCS event too many bubbles in the tissue that expanded too fast? Or the lung gets overwhelmed and too much gas recirculates to the arterial side where it gets trapped there?

Remember the PFO problem, where its thought that too many microbubbles will recirculate to the arterial side. This test I think is supporting that idea.

As I said before, it a great calibration point. We have the divers on the edge of normal OK deco, without injury, and we can see what's happening here. There a lot of interesting variations on this test that would add to knowledge.

I agree with this, seems reasonable conclusion.

 

[gianaameri]

We have the divers on the edge of normal OK deco, without injury, and we can see what's happening here.

For more knowledge on specific topic of "without injury" try: "Deeper into Diving" Lippmann, John.

Trying to help.

 

[rossh]

.
Getting back to the USN test. I have been listening to the DAN 2008 Technical Diving Conference. There is a transcript available, but be warned - its missing quite a lot of the actual conversations, and many important details were left out. Your will get more from listening to it. here with slides

What is unique about this presentation (and better than the UHMS version, also 2008) is that the DAN one has extra material included on the end, that goes onto describe different types of deep stops, that were not part of the test or mentioned in the paper. It then recommends and approves a certain type of deep stop (more on this in the next post).

I know this stuff is boring to many, but it does give you more insight as to why the USN test was done the way it was, and how it was destined to fail.

*********

From the DAN 2008 Presentation. Quotes from Wayne Gerth:

33:00 "The model is the BVM3 - a statistical model that is fitted to a large number of air and nitrox dives - published."

36:44 "We show VGE data, because everyone wants to see that, but in the end, VGE and DCS data don't relate very well."

38:00 "... if any profile exceeded 7%, we would stop (the test). Like wise, we did want to waste a whole lot of time testing two profiles that we grossly over estimated the risk for. So if they were close to zero, then we wanted to stop (the test) somewhere there, so we could rethink and start again. So we also wanted to reject low, if any of the profiles got to less than 3%."

39:30 "The VGE and the DCS that we saw, did not correlate well."

40:10 "The conclusion for this trial... Slower gas elimination, and/ or continued gas uptake offset any benefits of reduced bubble growth at deep stops."

Questions: Ron Murray

49:10 Q. "My concern with having apples to apples with 174 mins of decompression (for both profiles), that it was the optimal decompression for the VVAL18, but it was NOT the optimal decompression for the BVM3. and had you had a significantly shorter total decompression time for the BVM3, you would have had a lower risk of DCS for the BVM, and we potentially would have seen a different outcome. I'm just concerned that we maybe should not have compared apples to apples (profile times)."

A. "The actual thing that was tested .. in the end, it didn't matter what algorithm we used to calculate these profiles - one (profile) had a deep stop Skew, and the other did not. And the only difference between the two schedules was that (skew)."

50:20 Q. "When you were looking at which different profiles to test, had you used the BVM to calculate the risk, and assign the decompression for 170 for 30, it would not of assigned 174 minutes of decompression. And now you have a much lower risk with a shorter decompression?"

A. "That is correct. But... No, we have the same risk, for a shorter decompression. There were two ways in which we examined in the experimental design. One was to test algorithm vs algorithm with two different schedules, that had total decompression times, but the same decompression risk. The other, as we tested where the decompression times were the same, and the DCS risks were different. So the issue was, which is easier to demonstrate in an experiment. What takes a lesser n of dives, and we decided the cleanest most direct answer..... I should say either one of those two approaches is conceptually equivalent, we could have done it either way. The issue then became what is the number of man dives to do in order to prove there is no difference in risk."


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

Some points I'd like to make:

The BVM3 is a statistical model fitted to probabilistic data points. That data is navy shallow stop data. The BVM3 is not a deep stop model or a dual phase model like the VPM / RGBM.

The BVM3 profile used is "Skew" type profile (see next post). VPM-B does not use this type of profile.

The test would be stopped if either test profile exceeded the low or high limits.

The VGE and the DCS did not correlate well.

The two profiles had the same run time, but different risk levels. It was expected for profile A1 to give lower DCS than profile A2. But the results were not normalized to the same risk basis on the graphs. If the DCS rates had corrected for the difference in the profile risk rate (to get them on the same scale), then the two DCS lines would have been drawn much closer together. But because the data on the graphs was raw, the difference is exaggerated unnaturally, and the "shock" value is maximized. That is not good for public viewing.
.

 

[Simon Mitchell]

Ross,

.
VPM-B does not use this type of profile.

No, but it does share the propensity to reduce supersaturation of fast tissues at the expense of increasing it in slow tissues. There is evidence that this MAY not be a sound decompression strategy.

.
The test would be stopped if either test profile exceeded the low or high limits.

I don't know why you keep raising this. Stopping and analysing the difference between groups existing at that time does not invalidate the study as you have previously tried to claim.

.
The VGE and the DCS did not correlate well.

Its time you stopped flogging this one as well. We ALL KNOW that high bubble grades cannot be used as an predictor of DCS in an individual. They would therefore be useless as a diagnostic tool. But we (except you it would seem) also know that very high bubble grades are associated with a higher risk of DCS. Which brings me to this piece of self-serving logic...

.
As I said before, it a great calibration point. We have the divers on the edge of normal OK deco, without injury, and we can see what's happening here.

An alternative interpretation is that following this profile, which is allowed by your algorithm, consistently turns divers into ticking time bombs, and it was just luck and an inadequate number of subjects that resulted in no clinical problems being seen.

Ross, I reiterate that I am not anti-VPB or bubble models or deep stops, and I do not claim to have definitive proof that they are good or bad. What I cannot abide is your promotion of these methods as superior, and the baseless arguments you use to both support this view and discredit any evidence to the contrary.

Simon M

 

[tecdiverdude]

Simon, if Ross didn't believe in his theory.. Then he would be a hypocrite for trying to sell it.. Correct?
Many, many men of science over the years strongly fought for what they believed in... Even without strong evidence or the scientific communities support they stuck by their guns .. Some were right, some were wrong, some changed the world.
Don't hold the fact that someone strongly believes in something as a reason to discredit their opinion, until either theory is unconditionally discredited, both seem to have merit by means of actually working in the real world .

 

[Simon Mitchell]

Don't hold the fact that someone strongly believes in something as a reason to discredit their opinion,

If Ross made it clear that what he is saying was ONLY his opinion then I would have nothing to say. Ross repeatedly presents his opinion as fact, and tries to justify it with incorrect / poorly informed reasoning (bubbling is not related to risk, the NEDU trial was about to invalidate itself; we have a database with lots of dives on it so that proves deep stops are better etc etc). I would remind you that the main thrust of the "opinion" he is expressing here is at odds with the published consensus opinion of the scientific community. Would you rather I ignored that and not point it out? What do you want from a forum like this?

until either theory is unconditionally discredited, both seem to have merit by means of actually working in the real world .

This is essentially the position I have been at great pains to take throughout this thread. Look at my posts and note how many times I have admitted that we do not have an "unconditional" answer about relative efficacy. eg:

I wish to reiterate that I am neither pro- nor anti- deep stops. I am merely trying to be objective in appraising the relevant evidence on the matter, and at this stage it would be unwise to stipulate a certain view either way.

Finally, since these debates can give a false impression of total polarisation, I would like to restate my position that I am not saying that deep stop decompression methods are bad or that they don't work. What I am saying is that the best evidence currently available does not support Ross's contention that these methods are demonstrably superior.

I'm not saying deep stop algorithms don't work, and I'm not even saying they aren't superior (though recent evidence suggests not). Nobody knows for sure. Nor am I suggesting that people should change what they do.

I reiterate that I am not anti-VPB or bubble models or deep stops, and I do not claim to have definitive proof that they are good or bad. What I cannot abide is your promotion of these methods as superior, and the baseless arguments you use to both support this view and discredit any evidence to the contrary.

It is Ross who will not agree with this very neutral position, and wants to discredit virtually every piece of evidence that opposes his view of superiority. I have spent the majority of my time defending that evidence.

Simon M

 

[DSix36]

Simon, I thank you for taking the time to point out everything that you have. I am at the beginning phase of learning to understand all this stuff and appreciate that someone will stand up and point out that something is NOT a proven fact.

It is hard enough for me to get a grasp on this without invalid facts being thrown into the mix. Your posts have helped me sort out several things already.

 

[Igor P]

If Ross made it clear that what he is saying was ONLY his opinion then I would have nothing to say. Ross repeatedly presents his opinion as fact, and tries to justify it with incorrect / poorly informed reasoning (bubbling is not related to risk, the NEDU trial was about to invalidate itself; we have a database with lots of dives on it so that proves deep stops are better etc etc). I would remind you that the main thrust of the "opinion" he is expressing here is at odds with the published consensus opinion of the scientific community. Would you rather I ignored that and not point it out? What do you want from a forum like this?



This is essentially the position I have been at great pains to take throughout this thread. Look at my posts and note how many times I have admitted that we do not have an "unconditional" answer about relative efficacy. eg:









It is Ross who will not agree with this very neutral position, and wants to discredit virtually every piece of evidence that opposes his view of superiority. I have spent the majority of my time defending that evidence.

Simon M

Simon, if you would read the links I posted, you would see that it is not just Ross position that NEDU deep stop study was not relevant to our diving, but Bruce Wienke and Marv's too. The profiles (BVM3 and VVAL18) were out of proportion for sport diving.

 

[emmbee]

Simon, if Ross didn't believe in his theory.. Then he would be a hypocrite for trying to sell it.. Correct?
Many, many men of science over the years strongly fought for what they believed in... Even without strong evidence or the scientific communities support they stuck by their guns .. Some were right, some were wrong, some changed the world.
Don't hold the fact that someone strongly believes in something as a reason to discredit their opinion, until either theory is unconditionally discredited, both seem to have merit by means of actually working in the real world .

I'd object to your use of the word "theory" in this context, but more importantly I'd like to point out that while the idea of the lone(ish) genius being right against scientific consensus has a certain appeal, mostly they've been just wrong. The most recent case I can think of when this has happened is with Wegener and plate tectonics, and it's worth mentioning that first, his hypothesis was full of holes, and second, geology at the time was more akin to stamp collection than science. This does not mean one should fold as soon as a study or paper or experiment suggests he's wrong, otherwise science wouldn't move forward.

Anyway.

There is an element of form in this discussion. I'm sure Ross is aware that his posts include opinions and interpretations, and trusts the reader to make the difference. In some contexts it's normal to do without "I think", "in my opinion" and so on. Just maybe not on a web forum, where people are liable to just read a few posts and, not reading an objection, take it as fact.

My 2c.

Many thanks to Simon Mitchell, Ross Hemingway, and everybody else. This is very interesting (to me, anyway) and hopefully will remain so.

Cheers,

Matthieu

 

[rossh]

It is Ross who will not agree with this very neutral position, and wants to discredit virtually every piece of evidence that opposes his view of superiority. I have spent the majority of my time defending that evidence.

Simon M

There is your problem. The evidence that you put forward Simon, when examined more closely turns out to be, not as relevant to the deep stops as you initially thought. If you took a hard look at the navy test, you would see that too. But you continue to use that test as the center piece of your presentations and arguments.

I'm not the only one in disagreement here. This whole discussion was done the first time around in 2008, by many people with all the right credentials. Sadly many of those have moved on, which leaves just me to hold the fort.

*****

A great deal of the "published consensus opinion" is written around destructive testing, where they drive the subjects off the edge and into complete failure with DCS. However, for today's diver, we need to solve a different problem. Were interested in comparing two kinds of success. Every different deco concept schedule in use today works well. The difference between them is one of divers perception of post dive feelings. How do you measure that? Is destructive testing the best method here?

****

Yes Simon, everything I write is my opinion, or comes from published studies or facts, or is my speculation, or from other peoples opinions and ideas re-thought. Happy now Simon?

This is not a medical forum, so go easy on the laymans use of terminology please. The audience here is mostly divers anyway. All too often its left to people like me to stand up and put forward an opinion on these medical matters in these internet discussions. You qualified medical guys seem to go hide under a rock some where.

Only a few of us here and silly enough to be writing about these tough and controversial topics and challenging you medical guys and the published papers. Yes - some of the opinions I write are too strongly worded - that's how I am IRL.

****

Simon, please make yourself useful - you have all the research papers on tap. Please find something that measures a ZHL, or a similar Haldane profile, that is a calibration sequence report, and with VGE data. It would be a nice addition to see what's happening inside a shallow model at its baseline calibration.

Thanks.

 

[rossh]

Hi, Yes I agree. Once a critical(??) amount of recirculation of microbubbles begins, then the model is no longer representative of the conditions. However I don't think its an area that needs to modeled further. I think instead its represents a boundary that should not be crossed i.e. the beginning of DCS.

I think the diver here has reached the safe limit of deco. He may also have reached the limit of the lungs capacity to filter off microbubbles, and a small amount is now starting to seep through to the arterial side.

Makes an interesting question.. Is a DCS event too many bubbles in the tissue that expanded too fast? Or the lung gets overwhelmed and too much gas recirculates to the arterial side where it gets trapped there?

Remember the PFO problem, where its thought that too many microbubbles will recirculate to the arterial side. This test I think is supporting that idea.

As I said before, it a great calibration point. We have the divers on the edge of normal OK deco, without injury, and we can see what's happening here. There a lot of interesting variations on this test that would add to knowledge.

Adding to this, after some more thought.

The recirculation problem is probably not as bad as it sounds. The people with a PFO as an example, have been recirculating some gas constantly, so its seems we can get away with this recirculation condition in some amount. But how?

Consider the conditions in decompression. We get the microbubble in deco, because of the supersaturation. The microbubble gas content will comprise of the bottom gas mixtures. In the later part of deco, we usually breath high EAN or straight O2. On the surface its Air.

Now if the microbubble is comprised of helium, there will be a strong off gas gradient between the arterial blood partial pressures and the microbubble. We are inspiring nitrogen only and not helium at the surface, so the microbubble will want to quickly diffuse its gas and back to a dissolved state. Therefore the bubble could be eliminated in the arterial side, before they can accumulate and cause damage. The dissolved gas will continue on in the usual manner and be absorbed or exhaled per normal, but with a slight increase in over all tissue pressures.

May be we do need to model a recirculation component. I'd think that it would apply only when microbubbles are flooding the lung at its peak. And it would apply to all models.

Maybe also this is why humans seems to able to tolerate only a Grade 1 or 2 nitrogen microbubbles, but are able to tolerate Grade 3 or 4 or more in helium dives. The helium microbubble will eliminate faster than the nitrogen microbubble on the surface.

Thoughts anyone?

The "Simon Mitchell" disclaimer - this is all my idea, and I thought it up all by myself, and you can't have any of it. So there. blah. :wiggle:

 

[rossh]

Ross,

VPM-B does not use this type of profile.

No, but it does share the propensity to reduce supersaturation of fast tissues at the expense of increasing it in slow tissues. There is evidence that this MAY not be a sound decompression strategy.

If you looked into modelling a little, you would see this in all parallel tissue models. Your GF and ZHL (even 100/100 profiles) most certainly does this. Its all a question of proportion and dynamic conditions. Its why models lay over flat when the deco gets big enough.

If you watched the DAN presentation, you will see the humble pie that is coming your way on this topic.

The test would be stopped if either test profile exceeded the low or high limits.

I don't know why you keep raising this. Stopping and analysing the difference between groups existing at that time does not invalidate the study as you have previously tried to claim.

Yes - its a semantic argument I agree - the results were in at the 3/4 mark, so why not just stop there. But the argument presented by your road show, and others was something else. "Look how terrible it was.. we have to stop this now". Its very misleading interpretation. And of course, because of the biased way in which the profiles were created with planned DCS risk, and the result it made, that then feeds into the fear mongering and FUD around this test.

Its time you stopped flogging this one as well. We ALL KNOW that high bubble grades cannot be used as an predictor of DCS in an individual. They would therefore be useless as a diagnostic tool. But we (except you it would seem) also know that very high bubble grades are associated with a higher risk of DCS. Which brings me to this piece of self-serving logic...

It might be a small distinction, but its an important one. High bubbles grades are associated with higher decompression STRESS. Not to be confused with DCS.

You can have high decompression stress, in a stabilized condition, without the occurrence of DCS. For this to progress into DCS, takes some additional conditions (which no one really knows what).

An alternative interpretation is that following this profile, which is allowed by your algorithm, consistently turns divers into ticking time bombs, and it was just luck and an inadequate number of subjects that resulted in no clinical problems being seen.

Is that not true of all algorithms? The base line nominal settings are located at the edge of deco. Thats whay models have conservatism, so we can adda safety margin. It most certainly is true for your favorite ZHL 16. That's why GF was invented - to back away from the edge and give a safety margin to ZHL. No one dives real ZHL 16. That would be 100/100. No thanks.

You can't have your cake and eat it too Simon. That GF that is so popular is a fix for ZHL. Now your trying to compare the nominal of one model, with the added safety margin of another. NO. If you want to make direct comparison, then its ZHL 100/100 only please.


The demographic of this forum and many a CCR diver is an older one, who needs something longer and safer in their planning. but for every one of us here, there is a new twenty something diver who wants and can dive a fast schedule. Do you want to deprive them of this, because your in the older diver club?

Basic scuba training tells us that as we age, we need more deco. Basic training warns use to be cautious and consider the consequences of too much fast deco. I think the situation is covered already.
.

 

[gianaameri]

Thoughts anyone?

Is it only with VPM that we end-up with bubbles in the arterial side (laving aside the venous ones for one moment), or this happens with other models as well, with the same or similar or any other frequency?

It is an open question for anybody who has access to data information.