NEDU Study

[rossh]

Here we go again...didn't we just have a thread about needing to fully disclose private interests that could be influencing what you are recommending to people.

Not to insult Ross but on the original thread there was a lot of concern for an ulterior motive.

Huh?? I include my commercial product link in almost every post. I'm actually the neutral one here.... I sell products that support both sides of this argument. Existing customers can transfer back and forth as desired, for free.


My contention in this argument, is against the irrelevant and phony science being presented, and the deliberate efforts of some in their fallacy position and attacks. Deco needs more science and less BS. This topic discussion has been overrun with latter by the anti VPM-B side.

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[rossh]

Dude, third grader science students can figure out that thermal stress was controlled for.

No, they can't.

The experiment design was deliberate - reduce profile stress (much lower than normal) across the board. [i.e extend all shallow times 2x normal]. Then substitute in increased thermal stress to try to elevate risk back into the profiles.

There is a science validation problem here.

1/ Thermal stress and profile stress work in opposing directions. Longer timed thermal stress is increasing risk, but longer timed shallow profile stress is reducing risk. These two stresses are not interchangeable or comparable in this situation.

2/ No validation of this substitution method shown or discussed. The only paper I know of that really tries to calibrate this thermal condition (TR 06-07), really highlights just how wild and unpredictable thermal stress can be.


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


Overall, tech divers need not care about this nedu test. No deeps stops, and no tech profiles and no tech models were tested. There is no provable valid connection from the test to current day diving practices.

Further more, the differences discussed in the nedu paper about gas loading, and generic formula it uses to validate its method - these same formula are inbuilt into every existing dive computer and every dive model we use today. The problem is already solved.

There is nothing new to be learned from this nedu test, or adjusted onto existing gas kinetic theory. Existing model theory as used in all existing computers and models today - correctly predicts or implies the relative outcome of the test.


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[UWSojourner]

Deco needs more science and less BS.

I'm not sure your claim to love science is credible, when you seem to hate everything scientists have to say.

The three most knowledgeable scientists on the topic that have participated in these discussions -- Drs Mitchell, Doolette and Pollock -- have all opposed your views regarding decompression and the interpretation and applicability of scientific research. I guess you love science so much that you're attempting to wrest it away from scientists!???

Here's a link to some of Dr. Pollock's comments regarding your views.

 

[RainPilot]

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[rossh]

Ross, these were symptoms of a developing acute inflammatory response (DCS) to surfacing tissue inert supersaturation over a duration of days of loading/unloading deco dive cycles. I think that's a more definitive etiology than your nebulous explanation above.


The short simple practical lesson learned is not to handicap yourself in multi-day deco diving from Day One "getting behind the eight ball", by using inefficient strategies like deep stops to further compound the problem. Compensate by extending out the shallow O2 stop profile after each consecutive day and take a day off after three or four days in a row.

Hi Kevin,

I am not going to defend your DIR practices... If you have been undercutting the the shallow time, then...well sorry to say, you got what you asked for. Those advanced DIR ascent theories and undercutting shallow time practices are the root of this problem and argument. The DIR classroom has been making up their own advanced and modified ascent rules and explanations for a long time. That is what this anti deep stop argument should be directed towards.... but its not.

Sadly, too many try to shift this argument onto innocent VPM-B and blame it for other peoples problems and bad practices. VPM-B doesn't suffer these issues.


Take a look at the hypocrisy around this whole argument. The recommended approach today is something like a GF 40/75, which can be seen below, is pretty much a VPM-B +3 or +4 plan.

.....then I would program my Petrel Computer from Day 1 thru 4 something like 40/80 for Day 1; 40/70 for Day 2; 40/65 for Day 3 and finally 40/60 for Day 4. On Day 5 take a break from diving, and then continue the same GF's for three or four consecutive dive days with one day-off schedule/pattern.

You might like to revise that a little... that 40/60 plan and direction is heading straight towards the failed Nedu A2 profile style.

 

[PfcAJ]

No, they can't.

The experiment design was deliberate - reduce profile stress (much lower than normal) across the board. [i.e extend all shallow times 2x normal]. Then substitute in increased thermal stress to try to elevate risk back into the profiles.

There is a science validation problem here.

1/ Thermal stress and profile stress work in opposing directions. Longer timed thermal stress is increasing risk, but longer timed shallow profile stress is reducing risk. These two stresses are not interchangeable or comparable in this situation.

2/ No validation of this substitution method shown or discussed. The only paper I know of that really tries to calibrate this thermal condition (TR 06-07), really highlights just how wild and unpredictable thermal stress can be.


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


Overall, tech divers need not care about this nedu test. No deeps stops, and no tech profiles and no tech models were tested. There is no provable valid connection from the test to current day diving practices.

Further more, the differences discussed in the nedu paper about gas loading, and generic formula it uses to validate its method - these same formula are inbuilt into every existing dive computer and every dive model we use today. The problem is already solved.

There is nothing new to be learned from this nedu test, or adjusted onto existing gas kinetic theory. Existing model theory as used in all existing computers and models today - correctly predicts or implies the relative outcome of the test.


...

Third graders understand controlled variables. You seem not to understand.

It's really just sad at this point. "The problem is already solved". No, not really.

 

[Dr Simon Mitchell]

Take a look at the hypocrisy around this whole argument. The recommended approach today is something like a GF 40/75, which can be seen below, is pretty much a VPM-B +3 or +4 plan.

No its not. Your own graph shows that VPM-B 3 or 4 keeps you deeper for longer and will load slow tissues substantially more during this period. Then VPM cuts approximately 10 minutes off the shallow decompression time which will result in even greater slow tissue supersaturation at that point. Since slow tissue supersaturation is what appears to account for the worse outcome in the deep stops profile in the NEDU study, it can be expected that the VPM profile would likely be associated with worse outcomes than the GF 40/75 profile if you could do a large enough study to demonstrate it. In addition, no one has ever claimed that 40/75 represents optimal decompression. It simply represents a "step in the right direction" that can rationally be deduced from the current evidence. It may be that 50/75 or 60/75 is better, and that would start to look even more different to VPM +3 or +4.

You might like to revise that a little... that 40/60 plan and direction is heading straight towards the failed Nedu A2 profile style.

I wonder what you are thinking when you look at your own diagrams. Again, it shows a large area between the curves that represents substantially less inert gas loading in slower tissues. And once again, no one is saying that 40 is the right GF-lo for optimal mitigation of the adverse effect of excessive deep stopping. It may be 50 or 60.

Simon M

 

[UWSojourner]

Take a look at the hypocrisy around this whole argument. The recommended approach today is something like a GF 40/75, which can be seen below, is pretty much a VPM-B +3 or +4 plan.

Of course your claim is complete nonsense as has been shown over and over again.

See this post. It shows that for a 240ft 20min dive VPM-B+3 incurs 30% more deco stress than GF60/75 (which has the same runtime).

See this post. It shows similar results for a 270ft 20min dive comparing VPM-B+4 to GF40/74 and GF66/66.

See this post from Dr. Pollock. In that post he says,

"The impact of deep stops is not that they target some different physical reality. It is actually quite simple; the extra time spent deep allows more inert gas uptake in the relatively undersaturated intermediate and slow tissues. This is simply a loading problem that subsequently produces a higher degree of decompression stress. If there is less uptake at depth, ascent to a relatively shallow stop has much less risk. The idea that deep stops controlled bubble growth is one of the armchair arguments that has not lived up to human testing. Reframing the argument does not improve the validity. As with all the the protocols we developed and subsequently saw fail, it is time to respect the data over the hand-waving."

That quote describes in words what the heat maps show visually. Staying too deep as recommended by bubble-model-style profiles delays effective off-gassing, allows more gas uptake, and causes more of the deco obligation to be settled on the surface. It is simply a loading problem. As I've said before, GF in almost any configuration does not suffer this problem to the same degree as VPM. And GF40/X or GF60/X, etc., is demonstrably better as is highlighted in the posts above.

 

[Kevrumbo]

Hi Kevin,

I am not going to defend your DIR practices... If you have been undercutting the the shallow time, then...well sorry to say, you got what you asked for. Those advanced DIR ascent theories and undercutting shallow time practices are the root of this problem and argument. The DIR classroom has been making up their own advanced and modified ascent rules and explanations for a long time. That is what this anti deep stop argument should be directed towards.... but its not.

Sadly, too many try to shift this argument onto innocent VPM-B and blame it for other peoples problems and bad practices. VPM-B doesn't suffer these issues....

Ross, VPM-B nor any of your products has anything to do with my DCS injury. And I never asked you to "defend" my Ratio Deco practices, nor do I care for your flippant contempt above of "you get what you asked for". . .

So what do you tell those who actually get bent on VPM-B, Ross? Hypothermic Stress? Multi-day Fatigue? Some other "bad practice" oher than "innocent" VPM-B??? Who's being dishonest and hypocritical by "blaming the victim" here Ross?

It's already been demonstrated and understood that the Ratio Deco Method as originally implemented (what you call "DIR practices" Ross) had some of the deepest & longest stops of any decompression profile, in which the NEDU Deep Stop Study has shown to skew the surfacing inert gas loads of the Slow Tissues into peak AND long duration Supersaturation states, thus increasing the probability of DCS.

That all Bubble Models exhibit this similar pattern is the main implication of NEDU Study for us as sport tech divers, and primary experimental justification for the US Navy to not adopt bubble decompression models for their dive operations.

(Sorry Ross, but claiming "innocence" for VPM doesn't excuse it. . .)

 

[rossh]

Ross, VPM-B nor any of your products has anything to do with my DCS injury.

Thank you for your honesty. Please remind the others of the same message.

And I never asked you to "defend" my Ratio Deco practices, nor do I care your flippant contempt above of "you get what you asked for". . .

So what do you tell those who actually get bent on VPM-B, Ross? Hypothermic Stress? Multi-day Fatigue? Some other "bad practice" oher than "innocent" VPM-B??? Who's being dishonest and hypocritical by "blaming the victim" here Ross?

It's already been demonstrated and understood that the Ratio Deco Method as originally implemented (what you call "DIR practices" Ross) had some of the deepest & longest stops of any decompression profile, in which the NEDU Deep Stop Study has shown to skew the surfacing inert gas loads of the Slow Tissues into peak AND long duration Supersaturation states, thus increasing the probability of DCS.

Yes, agreed, the DIR or RatioDeco methods, in it various forms, is the problem. I have been critical of some of the RD modifications, for a very long time (here). Some of these RD techniques have deliberately undercut or reduced the shallow time. The basic issue (as you allude to), is these changes and alterations can override or ignore the underlying basic gas kinetic formula, and a deficiency can develop.


A finger should have been pointed directly at the problem above and to name where it comes from. These concerned scientists should be directing there attention on this RD and the source of these weak theories. But sadly, the current antagonists and friends have never once mentioned RD or DIR theory as the culprit. Instead the focus has been on innocent VPM-B and to use it as scape goat and to blame it for other peoples problems, and to tarnish VPM-B with other peoples model theories.


***********

Your issues above with RD, can be explained because of the departure from existing basic gas kinetics.


VPM-B (like ZHL) is a proper model, and it follows the proper formula for gas kinetics. These do not suffer the gas imbalance issues as the ad-hoc RD methods do. VPM-B, ZHL, follow the same basic gas kinetic formula as used in the successful nedu A1 profiles, and all these models are correctly orientated with the nedu test results.


Nothing matches the failed A2 profile. The A2 does not follow conventional gas kinetic limits. However, it does have some common traits with the ad-hoc RD methods, and you are correct to draw some conclusion about that.



The underlying message from the nedu test, was to keep following, the stick with the basic gas kinetic formula. ZHL and VPM-B already do this, and follow those same well tested and accepted formula. So... nothing is wrong, nothing to fix.

That all Bubble Models exhibit this similar pattern is the main implication of NEDU Study for us as sport tech divers, and primary experimental justification for the US Navy to not adopt bubble decompression models for their dive operations.

(Sorry Ross, but claiming "innocence" for VPM doesn't excuse it. . .)

Please do not get conned or further assist in this game of "guilt by word association" ... the words "bubble", "deep" are being used as a metaphor and substitution for actual science.


The nedu BVM(3) "bubble" model is a shallow stop design, a TDBM design. It has elongated shallow stops and includes a most irregular gas kinetic pattern, that are not present or representative of in any tech models.

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