Reverse profiles--pro's & con's

[rcohn]

Note -- I'm not saying that bouncing after a deep dive won't give you a hit, just that it appears bubbles slipping past the lung filter does not appear to be the reason why.

Ralph

 

[Uncle Pug]

Originally posted by rcohn
Note -- I'm not saying that bouncing after a deep dive won't give you a hit, just that it appears bubbles slipping past the lung filter does not appear to be the reason why.

Ralph

Any idea then how it could happen when PFO has been ruled out by trans-esophageal ECG?



Neither could the chamber docs hence it was declared an *underserved hit*.....

Non-definitive diagnostic terms are handy.

 

[rcohn]

Could simply be bad luck, apparently bubbles form after all dives, ocasionally they form in exactly the wrong place.

Small embolism? Dehydration?


Ralph

 

[Uncle Pug]

Originally posted by rcohn
Could simply be bad luck

Well then the diagnosis of *undeserved hit* was very accurate....
This guy was a very nice feller and certainly didn't deserve a hit of bad luck.

Come on Ralph.... first you complain about non-substantiated un-scientific pontifications and then when pressed you weigh in with the well tested and clinically proven *bad luck* ut:

 

[jetblast00]

I think it's a bit unfair to ask Ralph to make a diagnosis soley by reading internet posts that retell a story second hand. (I know, I know, you were just trying to make a point) But, I also think that Ralph has to realize that the "unsupported unproven theories as if they are established documented scientific fact" are most of what we have to go on. The actual scientific tests are far and few between from what I understand. What we do have is the empirical tests of divers who have gone diving and the medical communities theories as to these empirical results.

So one of the benifets of reverse profiles would be that we're not bringing medium post-dive bubbles back down to a moderate depth where they won't fully crush and can still act as 'bubble seeds'. This is bad because they will probably be accumulating gas much quicker than the normal nuclei present in the blood because of their bigger size?
Any bubbles on a shallow-first dive then brought to a greater depth would certainly crush. Am I following you UP?

Assuming no PFO in an individual and no embolism, how much gas in bubble form can really travel from the venous side to the arterial side? Sorry, if it's a dumb question, I fix computer networks, not inside people networks...

 

[Uncle Pug]

Originally posted by jetblast00
I think it's a bit unfair to ask Ralph
********
But, I also think that Ralph has to realize

Boy... if that isn't buttering your bread on both sides!

Am I following you UP?

I don't know.... I can't tell.... I haven't got it figured out myself yet.

Key elements (ably refuted by Ralph) seem to include the notion of bubbles crushing and passing the *lung filter* ~ coupled with the notion that the longer deco of the second (and deeper) dive will take care of that ~ coupled with the notion that the gas load of the first dive is only a small part of the total gas load incurred during the second dive (instead of the other way around) and so can be dealt with effectively instead of trying to deal with a substantial gas load without appropriate deco stops.

Or something like that....
Totally unsupported and unproven of course not to mention that I have probably muffed the explaination and omitted the most important components.

Assuming no PFO in an individual and no embolism, how much gas in bubble form can really travel from the venous side to the arterial side?

I don't know. According to Ralph's doppler, none. I am not so sure about that but I don't have a doppler or anyone willing to do the dives to find out even if I did. Common wisdom is to do the deepest first because they say so... so I guess that is what you should do.

 

[rcohn]

Bad luck is scientific. There is a certain probability, let's say as a completely off-the-wall guess 1 in 100000 (0.00001), that a bubble can randomly form in/on a nerve and cause paralysis. Most divers will obviously never experience this. However, if it happens to you, that is "bad luck." In more scientific terms, just random outcome.

Originally posted by jetblast00
I think it's a bit unfair to ask Ralph to make a diagnosis soley by reading internet posts that retell a story second hand. (I know, I know, you were just trying to make a point) But, I also think that Ralph has to realize that the "unsupported unproven theories as if they are established documented scientific fact" are most of what we have to go on. The actual scientific tests are far and few between from what I understand. What we do have is the empirical tests of divers who have gone diving and the medical communities theories as to these empirical results.

While we may often have only unsupported unproven theories to explain phenomena, they are presented as such, that's fine. The problem is created when these theories are presented not as theories, but as if they are established documented scientific fact. I've heard "experts" present concepts based on such thin unsubstantiated evidence that they don't deserve to be called theories, as if they were factual and serious concerns for all divers. This leads to confusion and possibly the wrong conclusions. For example, it is a fact that increased inert gas loads acquired under pressure will lead to DCS. Studies and empirical experience over nearly 100 years (or more?) has established this fact. No one knows exactly what the mechanism(s) behind the hits is and there are a number of theories that have been floated to attempt to explain them. None has yet been proven to my knowledge.

Originally posted by jetblast00
So one of the benifets of reverse profiles would be that we're not bringing medium post-dive bubbles back down to a moderate depth where they won't fully crush and can still act as 'bubble seeds'. This is bad because they will probably be accumulating gas much quicker than the normal nuclei present in the blood because of their bigger size?
Any bubbles on a shallow-first dive then brought to a greater depth would certainly crush. Am I following you UP?

This discussion is the first time I've heard anyone suggest that reverse profiles are actually safer. Bubbles on a shallow first dive grow in size and will not crush on the deeper dive, they will grow a bit more. You have plenty of bubble seeds in general and bubble size is most likely not the rate determining mechanism on bubble growth, I think diffusion and perfusion rates are much more important.

I'm an engineer not a physiologist, when Dr. Deco returns he can provide much better answers, though many of these question have come up before and can be found in the board archives.

Ralph

 

[rcohn]

A reference

http://www.scubaboard.com/showthread.php?s=&postid=36957&highlight=lung+and+bubble#post36957

 

[100days-a-year]

Ralph,did you miss the thread on horizontal deco? It was even more fun than this one.You're right of course that little research is conclusive in support of reverse profiles but I wonder if Mike has some links to Weinkes views on'em.Anecdotal evidence is usually not accepted as proof in most circles but diving seems to be full of wives tales and witch-doctory.My views are more nuetral ,but I love to watch.

 

[rcohn]

The Suunto RGBM implementation penalizes reverse profiles and the new NAUI RGBM no-stop tables completely prohibit reverse profiles. I think that summarizes Dr. Wienke’s views. Remember he is a theoretician and his views seem to be based on theoretical considerations. Dr. Wienke’s books are by far the best source describing his views but the following link will lead to his online papers.

http://www.scubadiving.com/talk/read.php?f=1&i=146599&t=146471

Ralph