DIR recreational deco?

[MikeFerrara]

Reverse profiles...

This is what Bruce Wienke had to say in this thread.

Folks,

Contary to what you might read/hear about RPs in general,
DATA suggests that RPs with decrements larger than 40 fsw are
not a good thing. Especially as you go deeper on both dives.
And SIs are within a few hrs. And profile times are in the
same ballpark. This came out of the Smithsonian RP Wkshp.

Deco RPs are a relative bad thing -- see my earlier posts and refs therein. On both rec and tec RPs within SIs of 1 - 3 hrs.

Bub mechanics contraindicates same as decrements and
depth both increase, and SIs are shorter than a few hours.
And profile times are the same scale

Shallow (no-deco) dives followed by much deeper extended
deco dives (RPs) within SIs of 3 hrs, and vice-versa, probably
fall into the forward and reverse yo-yo category, with the deep
deco dive the main concern and the shallower ones second order
so long as they are not too deep nor long. Maybe I can
quantify when I get back.

Bottom line overall is RPs, especially for deco regimes, are
not recommended. Data says same.

Odd ball cases (disproportionate bottom times) need some
further data and analysis.

Bruce Wienke
Program Manager Computational Physics
C & C Dive Team Ldr
__________________
BRW

Many dive magazines totally misrepresented the findings of the workshop and it was translated, in some publications, to say basically that it doesn't matter any more since we use computers rather than tables.

I haven't ever been able to figure out what GI is talking about half the time but in the above referenced thread I think a couple of people who know more than me took a stab at it.

What little science there is doesn't seem to support doing the deepest dive last.

 

[Whirling Girl]

Many dive magazines totally misrepresented the findings of the workshop and it was translated, in some publications, to say basically that it doesn't matter any more since we use computers rather than tables.

What little science there is doesn't seem to support doing the deepest dive first.

Sometimes Wienke needs to be translated, since he doesn't write in plain english.

So, George and Wienke reach opposite conclusions for reverse profile deco diving. In the context of decompression dives, though, I tend to side with George, simply because his reasoning makes more horse sense, as opposed to the thin and fizzy bubble science being tossed around.

I don't think that science has really caught up with the WKPP. But I think it's good that people who are actually doing these dives, and then getting Dopplered afterward, are showing that bubble theory doesn't have it all figured out yet.

However, it's dangerous for average joe recreational divers to apply anything that George and his former team have concluded to recreational dives without a thorough understanding of Wienke, RGBM, and all the other applicable theory first, and also without being insanely physically fit. Otherwise it's just theory, because recreational diving on air by most of us is a completely different ballgame in terms of gas transfer efficiency.

 

[MikeFerrara]

Sometimes Wienke needs to be translated, since he doesn't write in plain english.

So, George and Wienke reach opposite conclusions for reverse profile deco diving. In the context of decompression dives, though, I tend to side with George, simply because his reasoning makes more horse sense, as opposed to the thin and fizzy bubble science being tossed around.

I don't think that science has really caught up with the WKPP. But I think it's good that people who are actually doing these dives, and then getting Dopplered afterward, are showing that bubble theory doesn't have it all figured out yet.

However, it's dangerous for average joe recreational divers to apply anything that George and his former team have concluded to recreational dives without a thorough understanding of Wienke, RGBM, and all the other applicable theory first, and also without being insanely physically fit. Otherwise it's just theory, because recreational diving on air by most of us is a completely different ballgame in terms of gas transfer efficiency.

You make some good points.

My first intended point or course was that DAN never recommended reverse profiles over forward profiles as some one earlier suggested and niether did the RP workshop conclusions. They were flat out misrepresented in the press.

I agree that BW isn't always easy to understand. However I think he's one of the people who has seen doppler data from the WKPP. I'd also point out that BW does a little diving himself. I'd also point out his statements are based on data, some (,aybe all) of which can be reviwed in his books and technical papers.

The question I would have to ask here is...if the WKPP did any reverse profile controled experiments using doppler is anything written up? I've heard lots about them being dopplered but I haven't heard what's being done with the data, by who or what the implications are...aside from what GI has written of course.

No doubt science doesn't have it all figured out when it comes to decompression. Certainly the WKPP dives some pretty extreme profiles and they must be doing something right. However, when a finance guy tries to explain the physiological reasons why what they do works without data it's just only going to go so far. Anecdotal data can be very misleading. Homegrown non-scientific explainations for it can sound pretty good too but that doesn't make it true.

Why do you say that GI's reasons for reverse profiles make more sense than Wienke's reasons against?

 

[Doc Intrepid]

Reverse profiles...

What little science there is doesn't seem to support doing the deepest dive first.

Mike, its a Monday and before coffee. But didn't you mean this sentence to read that Weinke's conclusions suggested that reverse profiles in general were NOT recommended?

IOW, "what little science there is doesn't seem to support doing the deepest dive second"?

 

[MikeFerrara]

Mike, its a Monday and before coffee. But didn't you mean this sentence to read that Weinke's conclusions suggested that reverse profiles in general were NOT recommended?

IOW, "what little science there is doesn't seem to support doing the deepest dive second"?

Yes. I'll edit the original so it doesn't look like I'm argueing with me.

 

[lamont]

Why do you say that GI's reasons for reverse profiles make more sense than Wienke's reasons against?

What GI3 has going for him are the WKPPs experience with bounce diving, the plausibility of the dive-profile-induced-PFO explanation, the analogy with chamber diving and the easy-to-understand mechanism of crushing bubbles.

Not saying he's right, but he does make sense...

 

[MikeFerrara]

What GI3 has going for him are the WKPPs experience with bounce diving, the plausibility of the dive-profile-induced-PFO explanation, the analogy with chamber diving and the easy-to-understand mechanism of crushing bubbles.

Not saying he's right, but he does make sense...

Yes, I think GI's statement that was quoted was from an article titled something like "Why we don't do bounce dives in the WKPP". As far as I know repetitive bounce dives have always been thought to be a problem. Nothing new there.

I don't know how much sense it makes because there's more effecting bubble growth or shrinkage than just ambient pressure.

Let me toss something out here though. On one hand it's been written by GI that if you decompress right then you're ready for anything 30 minutes later (or he is). On the other hand he states there are requirements for the second dive. Conventional wisdom has it that there is a residual gas load from the first dive. Now days, we know that some of it is in the form of bubbles. Obviously we don't want them to grow. Doing another dive is going to add to the inert gas load. Right? Going deeper will get us more of an additional load than shallower dive of the same time right?

ok, that addresses how much but not in what form or where. Can bubbles get from the venus side to the arterial side through the lungs? I don't know but I've heard it both ways.
Is that what we're calling a profile induced PFO?

How much do they need to shrink for that to happen? Are we relying on abient pressure change alone to shrink them from whatever size they were to what ever size they need to be?

I'll admit that there's a lot about phisiology that I don't know but something doesn't sound right.

 

[jbd]

Mike & Lamont--can you each provide your definition of a bounce dive?

 

[novadiver]

Mike & Lamont--can you each provide your definition of a bounce dive?

But can they provide the definition of recreational deco?or should it have been tecreational deco. Now I'm confused!!

 

[MikeFerrara]

Mike & Lamont--can you each provide your definition of a bounce dive?

I suppose I could provide mine though it wasn't really the subject other than in reference to an article on the WKPP site.

I would consider a bounce dive as just what it sounds like...all up and down. Of course repetative bounce dives would be more than one of them.