"Patent Foramen Ovale Influences the Presentation of Decompression Illness in...+

[dreamdive]

On extreme deco dives? You sir are mistaken. If you are going to do a bubble study comparing the effectiveness of pure haldanian deco models VS the
effectiveness of Bubble models like VPM or RGBM, I'll even be your Guinea pig to prove you wrong. The term deep stop may be confusing you, but if you read above, I never put a rigid figure on where that stop should happen. It is well proven that starting deco earlier and deeper leads to an overall shorter deco obligation with fewer and smaller bubbles.
Dan Volker no doubt saw this in action when he was diving with GI3 on the regular basis. George was known for doing extremely short deco(relatively short considering his dive profiles). I don't believe he was diving a haldanian model...I was never a GI3 fan, but that doesn't mean I don't buy in on his conceptual beliefs. I was more of an opponent of his internet persona.

Actually it's "mam" not sir. But I am not mistaken - you can look up the heated discussion on RBW a few months ago on that subject. Incidentially, there is good evidence that deep stops actually worsen DCS - even on deep dives. What most forget is that during your ascend you not only off gas but still on gas, too. You off gas some tissues while you still on gas others. A reason why we set our GF the way we do (and I don't share my settings on a forum because.....). Now, that being said, on very deep and long dives where some tissues approach saturations (and which ones etc too long to discuss here), decompression modeling needs to be adjusted.

 

[boulderjohn]

However, anecdotally, many WKPP'S and several of us, did a great many very extreme exposures, with very short decos, and with no dcs. In all the extreme dives I did with George, with the very short decos we did, I always felt great afterward....point being, if it was "so flawed", why did it work so well" ? Maybe the flaw was that it was too individualized? I will have to ask Bill to chat with JJ about this sometime

Just because what you are doing is not ideal does not mean you are going to die every time you do it. The tables that John Haldane worked out after testing on goats more than 100 years ago will still work in most cases, but you don't find many people following them today, do you?

George's ascent process was based on a paper extolling the virtues of the oxygen window as described by the author. When I was introduced to it and required to use it by UTD, it made no sense to me. I read the paper, and the conclusion of the oxygen window is contained in one small section that seems to leap out of nowhere, with nothing supporting it prior to its conclusion. It seemed to violate Dalton's Law. I read around, and found that it made no sense to a lot of people, and a lot of other people were saying the same thing. Then Michael Powell published Deco for Divers, in which he said emphatically that the theory was wrong. I then took a class on Ratio Deco from Andrew Georgitsis of UTD, who knew I had been challenging the basis for the ascent profile. In the class, he said that the oxygen window theory on which it was based now appears to be wrong, but he came up with two other reasons to continue that I frankly don't remember. I then had a discussion about it with Jarrod Jablonski of GUE, who also said they now believe the paper to be flawed, but they were continuing to recommend the same ascent profile because it had worked in the past. I have since learned that they have discontinued using that ascent profile.

I am very glad that it worked so well for you. The reason I was so interested in it back then was the experiences of our own group using it. In the vast majority of the dives we did, our experiences were just fine, like yours. We had only 5 DCS cases that I know of, including one helicopter evacuation from the dive site. I did not want to be the next DCS case, so I was argumentative about it. I no longer dive with that group, but I understand most of them still believe in that profile, as you do, and still use it.

 

[danvolker]

To me, there was is a much greater evil in finding it necessary to bring dramatically more gas on a tech dive, due to the current theories and their very different ascent shape and much longer deco times--much greater gas use.

The tech dives I care about, are in South Florida, where high rates of Gulf Stream intrusion create amazing current speeds even at the bottom around 300 feet deep. In some places, the bottom looks like scenes from some apocalyptic epic, where there are huge dunes and huge blowouts in the bottom terrain, which appears to be the result of severe, almost hurricane like storms blasting and terraforming the bottom. And where we find the greatest interests, and richest marine life concentrations in these high current areas, one of our greatest enemies is the high drag from too many stages and tanks and wings that are too large to allow the diver to be slick....even with a scooter, the diver needs to be slick, if they want to have full exploration range whereever the interests point them. I can get into a lot of very cool places and see some amazing things, with dual 80's jacked, and a 40 with pure O2 --this is relatively very low in drag profile, and even running up current can be relatively easy, compared to the "pack mule" configuration of many "long deep stop" and lots of gas players

For what we do here, George has a better system--for my buddies and I at least. And it does go to showing that everything out there is "just a theory", a model, with almost as much "art" to it as science

---------- Post added August 23rd, 2014 at 11:26 AM ----------

George's ascent process was based on a paper extolling the virtues of the oxygen window as described by the author. When I was introduced to it and required to use it by UTD, it made no sense to me..

While the paper may have caused George to TRY a different kind of profile, most of what George developed was from a massive number of his dives where he experimented on himself, and when or if he felt he was getting pain or inflammation or whatever triggers he felt indicated his last ascent move was too agressive, he would then note this for the future, and go back down 10 or 20 feet and re-do the last stop(s). George did this for years, constantly discussing results with Bill Mee and Dr Bill Hamilton, and THIS is how he arrived at his own individualized tables---and the ones that I used with him on all my tech dives.At the time, Bill Mee, Dr Bill, and George and I all agreed that VO2 Max was the best tool we had to take Georges tables and project/individualize for other team members....the assumption being that cardiovascular potential was the most important trait in a small population of fit divers doing extreme profiles--most important for use in evolving George tables for any of the others....as even among fit divers, there is a huge difference in VO2 Max between each one ( Oxygen processing ability per Kg of body weight) .

 

[dreamdive]

Just because what you are doing is not ideal does not mean you are going to die every time you do it. The tables that John Haldane worked out after testing on goats more than 100 years ago will still work in most cases, but you don't find many people following them today, do you?

George's ascent process was based on a paper extolling the virtues of the oxygen window as described by the author. When I was introduced to it and required to use it by UTD, it made no sense to me. I read the paper, and the conclusion of the oxygen window is contained in one small section that seems to leap out of nowhere, with nothing supporting it prior to its conclusion. It seemed to violate Dalton's Law. I read around, and found that it made no sense to a lot of people, and a lot of other people were saying the same thing. Then Michael Powell published Deco for Divers, in which he said emphatically that the theory was wrong. I then took a class on Ratio Deco from Andrew Georgitsis of UTD, who knew I had been challenging the basis for the ascent profile. In the class, he said that the oxygen window theory on which it was based now appears to be wrong, but he came up with two other reasons to continue that I frankly don't remember. I then had a discussion about it with Jarrod Jablonski of GUE, who also said they now believe the paper to be flawed, but they were continuing to recommend the same ascent profile because it had worked in the past. I have since learned that they have discontinued using that ascent profile.

I am very glad that it worked so well for you. The reason I was so interested in it back then was the experiences of our own group using it. In the vast majority of the dives we did, our experiences were just fine, like yours. We had only 5 DCS cases that I know of, including one helicopter evacuation from the dive site. I did not want to be the next DCS case, so I was argumentative about it. I no longer dive with that group, but I understand most of them still believe in that profile, as you do, and still use it.

John, I am sorry! I do not mean to tell you how to dive and if you found something that works for you that is great and you should stick with it.
I found what works for me and I am sticking with it. There is not just one way to "skin a cat" (hate that expression), even though some theorist want us to believe so. As the debate on deep stops on RBW showed, this topic is one that cannot be reconciled easily. It certainly is not a topic that can be discussed adequately on a forum (my opinion). So no offense, I only wanted to state that there is more than one answer to this. After all, it is all theory we are applying and one day, there may be a "scientific revolution" in decompression understanding just like with all the other sciences.

Dive well

 

[boulderjohn]

John, I am sorry! I do not mean to tell you how to dive and if you found something that works for you that is great and you should stick with it.
I found what works for me and I am sticking with it. There is not just one way to "skin a cat" (hate that expression), even though some theorist want us to believe so. As the debate on deep stops on RBW showed, this topic is one that cannot be reconciled easily. It certainly is not a topic that can be discussed adequately on a forum (my opinion). So no offense, I only wanted to state that there is more than one answer to this. After all, it is all theory we are applying and one day, there may be a "scientific revolution" in decompression understanding just like with all the other sciences.

Dive well

I was actually not responding to you at all. If you read my earlier post, you will see I have a "jury is out" attitude toward most ascent profile theories. My own thinking is probably closer to yours than you appear to have surmised in my poorly written posts.

---------- Post added August 23rd, 2014 at 10:30 AM ----------

To me, there was is a much greater evil in finding it necessary to bring dramatically more gas on a tech dive, due to the current theories and their very different ascent shape and much longer deco times--much greater gas use.

Why do you assume that newer theories that differ with those of the past necessarily mean longer ascent times and more gas?[/QUOTE]

 

[danvolker]

I was actually not responding to you at all. If you read my earlier post, you will see I have a "jury is out" attitude toward most ascent profile theories. My own thinking is probably closer to yours than you appear to have surmised in my poorly written posts.

---------- Post added August 23rd, 2014 at 10:30 AM ----------

Why do you assume that newer theories that differ with those of the past necessarily mean longer ascent times and more gas?

[/QUOTE]

Because I dive with GUE's with their ascent profiles---and am clear on Rock Bottom ideas/gas needs.....and this is quite different in how it causes planning for a 285 foot dive in ocean--on gas brought, and on ascent profiles ......I am most definitely NOT saying the GUE's are wrong....they have put huge thought and resources into their current system. If I was trying to create a system for thousands of divers--actually, even for hundreds, I would probably be preaching exactly what they do. But, I am just concerning myself with my tiny group of buddies

 

[TSandM]

It was interesting that, when Dr. Deco (Michael Powell) came and spoke to our dive club about the research they did when they were developing the RDP, he told us that they did Doppler studies on a lot of divers. Some divers just about wouldn't bubble, no matter what stupid profile you made them do; others seemed to bubble no matter how conservative the profile.

I would not be surprised to learn that the divers doing the very aggressive profiles in the WKPP all fell into the former category. And you simply cannot know this about yourself, until or unless you are repeatedly studied doing multiple profiles, to see what your own personal tendencies are.

 

[Taliena]

when I did my full trimix course me was told that if I wanted to do a lot of deep decodives, the only way to learn the best deco-modell for yourself is to try different schemas. And write down if you feel something strange after a dive. I happely never had dcs (or I don't know). But if I use in the 55-60m region with a 20-25 minute bottomtime on oc and a gas with 18/45 as backgas and a 50% as decogas that I feel better with an 20/30 (or 18/35) and a 50%. Or I take another decogas with me (80-100%). On ccr I just follow my computer (buhlmann 30/85 or vpm-b+3/80 from shearwater, both are ok for me). I now want to try some dives on 50/90.
If I dive on air to 40-50m and I can do deco on backgas (max. 20 minutes of total decotime, that is my personal limit without decogas), I feel really better if I take the last 5-10 minutes a 50% nitrox. So I prefer to have a decogas with me, even if I don't need it then.
In the 100m and more region I have done some dives, but a 20 in total (oc and ccr) is not enough to say what is best for me. But I don't do a lot of deepstops, only 1 or 2. First real stop depends on bottomtime. On my longest deco (around 160 minutes decotime, max depth 106m, but a long time on 88m too), I had my first stop on 60m for 1 minute and did no deeper stops as deepstop. in the 80m region, I don't do deepstops, but slow down my ascent speed a little bit, but not to 3m/minute, a 7-8m/min.
My profiles are not agressive, I try to stay healthy. But in the past I missed one time 13 minutes deco on a 50m dive with 20 minutes bottomtime and nothing happened (that was in my beginning of techdiving, I did not know a lot, so I trusted my buddy that forgot his decoschema)