Spisni study

[rossh]

Here we look into the Spinsi study, and explore the possible reasons to explain the unanswered question in the study - what caused the difference in bio-markers.

Spinsi.pdf

Further we will examine some of the existing explanations, and debunk some myths.

Above we explore the differences in time spent at various ppO2 levels.

The time involved with high ppO2 is doubled in the RDS profile.

The study tries to discount the difference in oxygen exposure, but it does not seem they took the extended time at 21m and 18m into consideration. We can see the RDS profile has double the time at ppO2 of 1.4 or higher.

The elevated ppO2 extra time at 21 and 18m, causes extra off gassing and lowering of stress mid dive, thanks to higher ppO2 pressures, but it comes at the cost of elevated inflammatory markers.


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Accepting that the study differences comes from this extended time at ppO2 1.6 / 21m, then it means RD2.0 will probably not be any better. RD2.0 still follows the same method of extended time in the middle.

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[rossh]

Here we see a comparison of supersaturation through the dive.

The initial ascent has 20% lower supersaturation in RD. That's the fast tissue area.

The supersaturation comes to a stop in the mid ascent phase, where the extended 21m stop time begins in the RD plan. The RD plan has much lower supersaturation here.

In the last stops, the two plans align with the about the same supersaturation levels.

The RD plan has less gas pressure (supersaturation) stress levels over the whole dive.

The surface supersaturation levels are nearly identical.


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The RD plan looks a bit messy, but actually plays on a trick, to reduce stress. The over stopping at 21m with 5+ mins of extra deco, is why the supersaturation pattern has the big dip in it.


The "slow tissue on gas", did not actually cause a problem, and is insignificant to the result (as is the case in most dives).

The surfacing off gas is near identical in both, and a 2 minute change to bottom time would be far more significant than the small differences seen above.


The idea that the tissue state is different and causes the test result difference, fails analysis... There is virtually no difference between the profile stress levels at the end of the dive. The difference in Spisni test bio-markers cannot be attributed to slow tissue on gas, or deep stops.

The most obvious cause of the test result, is the events in the 21m stop area (high ppO2 for extended periods).

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[Diver0001]

The RD plan looks a bit messy, but actually plays on a trick, to reduce stress. The over stopping at 21m with 5+ mins of extra deco, is why the supersaturation pattern has the big dip in it.

This is EXACTLY why it is not a scientifically valid study. If you want to compare the relative efficiency of different ascent strategies then you need to compare them on the same time scale. Every 1st year Bachelor student knows this.

What has happened here (in layman's terms) is that they have compared two different ascent approaches at different time scales and said, "SEE.... NOTHING WRONG HERE". This is (in a nut shell) also what you said in your first post (and as far as I know in EVERY post you make if you look at it in the big-picture).

This is like comparing a bicycle and a car. If you drive 100km in a car then you have a certain risk-profile of getting in an accident. If you drive 100km on a bicycle then you ALSO have a risk profile of getting in an accident. The car will get you there in... say... an hour. The bicycle takes 4 hours for the same route.... but if you drive 100km/h on a bicycle... well... then things change.....

What happened in this study... and the UTD POS study is that researchers then compare the risk profile for the car with teh risk profile for the bicycle then some people (like you) will think they are comparing risk profiles. But in reality they are comparing things that are so different that it's like comparing apples and oranges. There are similarities but mostly there are differences.

This is the fault in the logic you make in almost every post you make. I wish to God I could shake you hard enough for that coin to fall..... My experience, however, is that no amount of shaking is enough. You're a lost cause where this discussion is concerned.

You can make ANY ascent "safe" if you take long enough to do it. The issue that the entire internet is discussing isn't what's SAFE it's what is EFFICIENT. Those are two very VERY different concepts. If I take 2 years to ascend from a dive then it will certainly be safe... but if every dive I make takes 2 years then ... yeah... see what I'm saying?

Sure... deep stops are safe... if you COMPENSATE for that inefficiency with more shallow time. Even this VERY study said that. In their conclusions they say "The ratio deco strategy did not confer any benefit in terms of bubbles but showed the disadvantage of increased decompression-associated secretion of infammatory chemokines involved in the development of vascular damage."

Question: If you need to "compensate" for your ascent strategy, then why wouldn't you just use a more efficient ascent strategy? We've been on about that for years and yet some people, like you, are so paradigm locked that, to them, deep stops are sacred and need to be defended. It's like you have a financial investment in "deep stops" (oh.... actually... you DO.... how about that!)

People who do NOT have financial investment in deep stops and only care about the efficiency of the ascent are letting this paradigm go..... I understand that you make money on an algorithm that includes "deep stops" so just say it and get it over with. Everyone on this board could understand that you have this interest. What we cannot understand is this convoluted quasi logic that tries to frame deep stops in a positive light despite a mounting body of scientific evidence that the paradigm is wrong.

I challenge you to cite even ONE bonafide scientific paper since 2007 that corroborates your opinion. As far as I know, even Bruce Wienke, who is financially leveraged up to his testicles in "deep stops" isn't writing about it anymore..... But go ahead. I'd love to see your citation.

R..

 

[tridacna]

Dollars to donuts says that a new set of Rossh generated “justification graphs” are in production and will be published soon.

 

[Patoux01]

I'm confused. Did the oxygen window just make a comeback?

 

[Dan_P]

This is EXACTLY why it is not a scientifically valid study. If you want to compare the relative efficiency of different ascent strategies then you need to compare them on the same time scale. Every 1st year Bachelor student knows this.

What has happened here (in layman's terms) is that they have compared two different ascent approaches at different time scales and said, "SEE.... NOTHING WRONG HERE". This is (in a nut shell) also what you said in your first post (and as far as I know in EVERY post you make if you look at it in the big-picture).

This is like comparing a bicycle and a car. If you drive 100km in a car then you have a certain risk-profile of getting in an accident. If you drive 100km on a bicycle then you ALSO have a risk profile of getting in an accident. The car will get you there in... say... an hour. The bicycle takes 4 hours for the same route.... but if you drive 100km/h on a bicycle... well... then things change.....

What happened in this study... and the UTD POS study is that researchers then compare the risk profile for the car with teh risk profile for the bicycle then some people (like you) will think they are comparing risk profiles. But in reality they are comparing things that are so different that it's like comparing apples and oranges. There are similarities but mostly there are differences.

This is the fault in the logic you make in almost every post you make. I wish to God I could shake you hard enough for that coin to fall..... My experience, however, is that no amount of shaking is enough. You're a lost cause where this discussion is concerned.

You can make ANY ascent "safe" if you take long enough to do it. The issue that the entire internet is discussing isn't what's SAFE it's what is EFFICIENT. Those are two very VERY different concepts. If I take 2 years to ascend from a dive then it will certainly be safe... but if every dive I make takes 2 years then ... yeah... see what I'm saying?

Sure... deep stops are safe... if you COMPENSATE for that inefficiency with more shallow time. Even this VERY study said that. In their conclusions they say "The ratio deco strategy did not confer any benefit in terms of bubbles but showed the disadvantage of increased decompression-associated secretion of infammatory chemokines involved in the development of vascular damage."

Question: If you need to "compensate" for your ascent strategy, then why wouldn't you just use a more efficient ascent strategy? We've been on about that for years and yet some people, like you, are so paradigm locked that, to them, deep stops are sacred and need to be defended. It's like you have a financial investment in "deep stops" (oh.... actually... you DO.... how about that!)

People who do NOT have financial investment in deep stops and only care about the efficiency of the ascent are letting this paradigm go..... I understand that you make money on an algorithm that includes "deep stops" so just say it and get it over with. Everyone on this board could understand that you have this interest. What we cannot understand is this convoluted quasi logic that tries to frame deep stops in a positive light despite a mounting body of scientific evidence that the paradigm is wrong.

I challenge you to cite even ONE bonafide scientific paper since 2007 that corroborates your opinion. As far as I know, even Bruce Wienke, who is financially leveraged up to his testicles in "deep stops" isn't writing about it anymore..... But go ahead. I'd love to see your citation.

R..

I think the harshness of tone is unneccessary, but let's focus on the matter at hand;

The time spend in ascend/deco was different across the two ascend profiles compared in the Spisni-study, and I don't think that's good practice in a comparative study, obviously - but it wasn't a UTD-study, it was "just" supported by UTD with logistics, divers, etc. (I don't think it would be fair to underplay the effort, though).

It was in fact an independent, scientific study carried out by Prof. Spisni and others.

We can say that it's a weakness of that scientific study that the time spend in the ascends being compared, were different - and I would unequivocally agree, to be sure - but it was scientific nonetheless.

We can say the same for NEDU - it was a weakness that the divers were cold (a necessary weakness due to the nature of the questions being asked/tested) but that doesn't make it at all unscientific. Both studies were scientific, well documented and positive contributions to our collective understanding of the physiological decompression processes.

I interpret Ross' post as presentation of a hypothesis.
Without any referencing, I think that's only fair. To substantiate a claim for or against a hypothesis, would prompt referencing.

So, if I'm reading this correctly, the hypothesis presented is something to the effect of high ppO2 may cause an initial increase in off-gassing but also an increase in inflammation, which may in turn result in increased bubble-induced platelet aggregation by way of CCL5-activation, thus potentially offsetting the initial off-gassing by way of increased ppO2 (?)

If this is the working hypothesis (correct me if I'm wrong, Ross), then we can all work from here by providing references that serve to prove or disprove it, surely.

I'll be happy to be the first to report my economic interests in the matter:
Ziltch. I don't need any given deep stop emphasis to teach RD, and I don't need to teach RD in order to teach the classes I offer.

 

[Diver0001]

I'm confused. Did the oxygen window just make a comeback?

This is one of those paradigm locked ideas that Ross will certainly parade out at some point.

R..

 

[Diver0001]

I think the harshness of tone is unneccessary, but let's focus on the matter at hand;

The time spend in ascend/deco was different across the two ascend profiles compared in the Spisni-study, and I don't think that's good practice in a comparative study, obviously - but it wasn't a UTD-study, it was "just" supported by UTD with logistics, divers, etc. (I don't think it would be fair to underplay the effort, though).

It was in fact an independent, scientific study carried out by Doctor Spisni and others.

For crying out loud, Dan. did you not read the study? RD was thoroughly debunked by the very study that was intended to prove that it was superior.

In fact the entire idea that a "study" was done working backwards from a result to determine the approach is so against every scientific principle I know that I can't even describe how bad that is.

Even with the deck stacked, RD had a higher DCS incidence DESPITE a longer ascent profile. Even if you're not a scientist this should raise a red-flag for you....

Go back... read the literature. Seriously. Bite into the details and don't let go until you understand the details.

R..

 

[Dan_P]

For crying out loud, Dan. did you not read the study? RD was thoroughly debunked by the very study that was intended to prove that it was superior.

In fact the entire idea that a "study" was done working backwards from a result to determine the approach is so against every scientific principle I know that I can't even describe how bad that is.

Even with the deck stacked, RD had a higher DCS incidence DESPITE a longer ascent profile. Even if you're not a scientist this should raise a red-flag for you....

Go back... read the literature. Seriously. Bite into the details and don't let go until you understand the details.

R..

So because AG put out a vblog containing a joke based on his personal assumption that RD would dominate, Prof. Spisni and team's work was unscientific?

I think that's gibberish. The study wasn't carried out by UTD, it's just that UTD provided divers and logistics to the scientists who framed the study and wrote the report.

There's a reason we're not calling it the Georgitsis-study.

Also, the Spisni-study didn't have one single DCS-incidence, nor did it even work towards that metric.
I read the report multiple times. I have to ask - did you?

 

[rossh]

This is EXACTLY why it is not a scientifically valid study. If you want to compare the relative efficiency of different ascent strategies then you need to compare them on the same time scale. Every 1st year Bachelor student knows this.

R..

Yes, good experiment design wants two equal time profiles, but you can't have it when comparing two independent diving models. You need to come up with a better experiment design.


One simply cannot take two different decompression models with two naturally different run times for the same dive, and then force one of those profiles shorter or longer. In doing so, you have corrupted one of the test samples...even before you start. That's the same screwed up mess the Nedu test got so badly wrong, when they distorted the A2 profile so badly, in the end it represented nothing.


i.e. to compare model A to model B, don't try to manipulate one of them to fit it into the other ones space.



To use your car analogy... your asking to compare a Ferrari and a VW on a road test, but at the same speed. However a VW is unsafe at Ferrari speeds, and a Ferrari is no fun at VW speeds, so you get a junk comparison.. Hence to be relevant the road test needs to be done at different speeds.

You can make ANY ascent "safe" if you take long enough to do it.

R..

Yes you can.... providing other stresses ( like thermal stress) do not accumulate too much and offset that gain. And by doing the longer ascent, you are lowering your supersaturation levels... just like BOTH Spisni CDM and RDS plans did.


The GF does too - lowers supersaturation by some percentage.


The Spisni RDS plan also very much lowered stress, across the whole ascent in varying amounts (shown above).

Sure... deep stops are safe... if you COMPENSATE for that inefficiency with more shallow time.

R..

Yes, and existing models like VPM-B, ZHL, RGBM, etc, all do that correctly now, because they have a math model at its center, tracking all on/off gassing at every place in the dive and ascent, and dictating how much extra deco to add accordingly.


Every diving day you see this in action on your dive computer.... it tracks what every you do and builds an ascent plan as you go, including multilevel, deep stops and anything else you do.


This obsession you have to add extra time amounts manually, beyond what the model says, is not justified by any model math. What you asking for is extra time on top of extra safety on top of extra margin. This has turned into a compounding error.


By all means, feel free to add all the unnecessary extra you want, but please stop trying to justify this with false reasons.

Question: If you need to "compensate" for your ascent strategy, then why wouldn't you just use a more efficient ascent strategy? R..

The math and models we all use today, already correctly compensate for any amount of extra on gassing, anywhere in the dive... It doesn't need anybody patching more on top of more.


By all means, feel free to add all the unnecessary extra you want, but please stop trying to justify this with false reasons.

I understand that you make money on an algorithm that includes "deep stops" so just say it and get it over with.

R..

I sell software for BOTH sides of this argument...and I make the same amount of money either way. That makes me neutral. While people like you are clearly on one side of it.

a mounting body of scientific evidence that the paradigm is wrong.

R..

There is no valid evidence for your cause.... this Spisni test has no support for your argument. The nedu test has no scientific connection to deep stops. All the nedu really showed us is that proper models that follow real math still work (ZHL, VPM-B, etc), and that hand made junk profiles do not work.



The very basic math formula of supersaturation stresses is all we have for a stress measure... which I have shown above. These formula are intrinsic to most research, studies, modelling, graphing and comparing, for most of diving history.




David Doolette August 2016, here on SB:


"The "obsession" with supersaturation versus bubble mechanics is well founded. The putative cause of DCS is injury as a result of bubble formation. Supersaturation is a required condition for bubble formation and growth. There is broad (universal?) agreement that modelling tissue gas uptake with a range of exchange rates - as we do for instance with a collection of compartments with mono-exponential gas exchange - captures the essential processes, at least crudely. ...."

I challenge you to cite even ONE bonafide scientific paper since 2007 that corroborates your opinion.

R..

Opinion of what? I'm not interested in your made up straw man arguments.


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