Son of Deep Stops *or* Waiting to be merged with the mother thread...

[lowviz]

I would presume that once a microbubble is formed in a liquid (blood) it is just like every other bubble that forms in that media with the sole exception of size.

I also take it that your model chooses to ignore VGE's and only considers (similarly sized) bubbles in tissues. A modeler is quite free to make any assumption that he or she wishes, so I'm fine with this concept and thus your approach.

However, the model needs to prove out in the real world. This is where I'm stressing a bit. I don't see any way to do that just yet.

 

[UWSojourner]

Thats what these VGE are venous microbubbles. .. But not tissue growth type 2 DCS forming microbubble - those are most likely different.

Here are links to Dr. N. Pollock's comments (and a few quotes with each):

Diving too carefully?

"Intravascular bubbles are not the perfect measure, but they provide insights that certainly are not discounted in the scientific community. Similarly, they should not be discounted in the diving community."

Diving too carefully?

"Unfortunately, Ross, I do not believe that our core positions are in agreement. The differences are much greater than simply semantic."

Diving too carefully?

"It is not valid to talk about microbubbles in the bloodsteam as different from microbubbles in any other tissue."

Diving too carefully?

"Everyone would like to find the holy grail, but the important thing is the process. Cogitate, hypothesize, test, revise as needed, repeat. If the research community had any reason to believe the genesis of bubbles was wildly different between blood and non-blood tissue, we would probably have some evidence at this point. We do not."

Diving too carefully?

"... a fundamental element that is common to all bubble models of decompression ...Not one of them measures bubbles. Not one. There is theorizing and hand waving, but no measures. Despite this, the near-religious fervor is often felt."

Diving too carefully?

"Bubbles are a clear indicator of decompression stress. Getting off the bottom (that is, skipping the deep stops) can reduce tissue loading in intermediate and slow tissues. No matter what is done at depth, prolonging shallow stop time is effective at reducing VGE in individuals predisposed to develop them. Other strategies might work, but I am most impressed by those based on credible evidence. I call prolonged shallow stops really cheap insurance."

Diving too carefully?

"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 ... As with all the protocols we developed and subsequently saw fail, it is time to respect the data over the hand-waving."

Diving too carefully?

"The story is advancing nicely. Simon [Mitchell] has provided a number of solid references that describe some of the relevant current understanding ... Read, learn, decide for yourselves."

 

[David Doolette]

Yes I saw you had an attempt to make the nedu test and cold water testing, result verified as a VGE surrogate dcs end point. The conclusion was, it was not achievable, and gave warnings about not using these to diagnose DCS, and must be interpreted cautiously.

All the tests, for years, end up with the same basic conclusions. VGE are extremely vague, indicative of almost nothing in any reliable sense, we don't know how, why or where they form. They cannot be used for an absolute measure (ie. deco models / predictions). etc..


But here you and Simon are again desperately trying to make some sense out of VGE. But why? It adds nothing to the predictive power of an existing model and its supersat / tissue value / microbubble load levels of predictions. Existing model tracking / predicting methods are the vastly superior and more reliable, than VGE can ever be. So why the rush to try to invent more value from VGE?? Oh yeah ... so one can pretend that some kinds of deco are worse than others, and then start on a whole new scare tactic.

.

Your misrepresentation of this paper and of the scientific consensus about VGE are covered in the other thread, post #1217 is a good place to start
Deep Stops Increases DCS

 

[David Doolette]

Well that's maybe an approach that's easier than arguing about VPM-B +7: Calculating with a factor 2x on bottom time to consider strong on-gassing by workload.

So let's have a look at VPM-B +0 (critical radius N2 = 0.55) for 60min bottom time at 170fsw, and compare the schedule to the NEDU schedules:

Yet another made up non existent profile? Because it cannot make any real connection to the nedu profiles? So it all has to be invented.... pathetic.

But I want to get back to Leadduck's interesting post, Ross. Which part do you think is "made up", the standard practice of jumping schedules (decompressing on a schedule for a longer bottom time) to reduce risk when working hard on the bottom or diving in cold water, or the VPM-B schedule for a 60 minute bottom time at 170 fsw?

 

[Dr Simon Mitchell]

There was a test just recently - rabbits - they skipped 4 hours real deco time (8 hours Mitchell deco time), and made a direct ascent. half made VGE and died, the other half had not much to none ,and were terminated anyway. Which demonstrated the predictive power of a grade 3 VGE is somewhere between harmless, and death with in 10 minutes. Kind of shows how useless VGE can be.

You continue to misinterpret or misrepresent this study as supporting your views when it quite obviously does the opposite. In the hope that actually replicating the relevant text will help, here is what they say:

Can you not understand this relatively simple prose Ross? It clearly says that high bubble grades invariably caused death. Animals with lower bubble grades survived (until euthanized at 1 hour). That is a clear correlation between bubble grade and severity of disease.

Simon M

 

[rossh]

You continue to misinterpret or misrepresent this study as supporting your views when it quite obviously does the opposite. In the hope that actually replicating the relevant text will help, here is what they say:

Can you not understand this relatively simple prose Ross? It clearly says that high bubble grades invariably caused death. Animals with lower bubble grades survived (until euthanized at 1 hour). That is a clear correlation between bubble grade and severity of disease.

Simon M

Yes I understand it. Half the rabbits were lucky to survive a little bit, but why did they not all make the same levels of VGE?


I can also see the manipulation being played at here. 3 is bad , 2 is good.... . Who cares. This test added zero to the knowledge base. Its no more clever than blowing up your kid sisters dolls, when you were younger. Look Ma, I blew up the rabbits.

But why the difference in VGE?? That's the important question....

• They all had the same absorbed level of gas load,
  
• They all had the same volume of gas to be removed...
  
• They performed life threatening direct ascents.
  
• Why did half convert some dissolved gas into a gaseous (microbubble) state, and half kept it in mostly dissolved state?

Of course this is all pulmonary DCS at work here . NOT regular harmless VGE that we see in ordinary dives. Are the two the same thing? No one knows.

That's what is important to discover.... because if you can work out the different reasons for different VGE levels, you will then have a good idea what VGE actually means, and if its important or not.

But right now - VGE are a mystery with no known meaning or value..

.

 

[rossh]

But I want to get back to Leadduck's interesting post, Ross. Which part do you think is "made up", the standard practice of jumping schedules (decompressing on a schedule for a longer bottom time) to reduce risk when working hard on the bottom or diving in cold water, or the VPM-B schedule for a 60 minute bottom time at 170 fsw?

I think I read it wrong initially... sorry. disregard

 

[rossh]

You lot can quote VGE papers and the vague and subtle meaning they try to distill from VGE, all you want. The reality its none of them can explain the origins of everyday ordinary VGE in its harmless state in ordinary dives...


It about time, after 45 years of nothing new.... that we came to realize that all we have now is a big fat zero.

For 99.95% of VGE amount to nothing. Until one can up come with a real positive meaning to VGE, like I asked above, all the guess work on the value of VGE amounts to zero. And that is what VGE are worth right now - zero.


.

 

[UWSojourner]

Until you can up with a real positive meaning to VGE, like I asked above, all the guess work on the value of VGE amounts to zero. And that is what VGE are worth right now - zero.

But right now - VGE are a mystery with no known meaning or value.

This establishes correlation (a real positive meaning):

From Tech Diving Conference Proceedings page 120.




These quotes from Dr. N. Pollock are interesting in the VGE discussion:

#294
"Intravascular bubbles are not the perfect measure, but they provide insights that certainly are not discounted in the scientific community. Similarly, they should not be discounted in the diving community."

#305
"Unfortunately, Ross, I do not believe that our core positions are in agreement. The differences are much greater than simply semantic."

#313
"It is not valid to talk about microbubbles in the bloodsteam as different from microbubbles in any other tissue."

#318
"Everyone would like to find the holy grail, but the important thing is the process. Cogitate, hypothesize, test, revise as needed, repeat. If the research community had any reason to believe the genesis of bubbles was wildly different between blood and non-blood tissue, we would probably have some evidence at this point. We do not."

#333
"... a fundamental element that is common to all bubble models of decompression ...Not one of them measures bubbles. Not one. There is theorizing and hand waving, but no measures. Despite this, the near-religious fervor is often felt."

#356
"Bubbles are a clear indicator of decompression stress. Getting off the bottom (that is, skipping the deep stops) can reduce tissue loading in intermediate and slow tissues. No matter what is done at depth, prolonging shallow stop time is effective at reducing VGE in individuals predisposed to develop them. Other strategies might work, but I am most impressed by those based on credible evidence. I call prolonged shallow stops really cheap insurance."

#375
"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 ... As with all the protocols we developed and subsequently saw fail, it is time to respect the data over the hand-waving."

#390
"The story is advancing nicely. Simon [Mitchell] has provided a number of solid references that describe some of the relevant current understanding ... Read, learn, decide for yourselves."

 

[Jack Hammer]

Ross, what little credibility you "had" left went away when you started citing and arguing with the guy who wrote the paper telling him he doesn't understand what it means...