• Welcome to ScubaBoard

  1. Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.

    Benefits of registering include

    • Ability to post and comment on topics and discussions.
    • A Free photo gallery to share your dive photos with the world.
    • You can make this box go away

    Joining is quick and easy. Login or Register now by clicking on the button

Is UTD still a "fringe" organization?

Discussion in 'Technical Diving' started by onepointfivethumbs, Mar 24, 2021.

  1. CAPTAIN SINBAD

    CAPTAIN SINBAD Divemaster Candidate

    # of Dives: 200 - 499
    Location: Woodbridge VA
    2,916
    1,078
    Exactly and that is why we classify bubbles as "silent bubbles" whose presence can be picked up by Doppler but they are not causing any reported symptoms and "symptomatic bubbles" where presence of bubbles in the blood can also be verified externally by symptoms. What that would mean is that if two dive profiles are tested and one generates more silent bubbles than another, then the diver is closer to having symptoms than the one which is producing less silent bubbles. Both divers will be symptom free but we know which one is safer. This is why Bubble Score Index is important.
     
  2. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: U.S. East Coast
    11,826
    9,755
    I'm sorry, this is not logical. For what you have said to be meaningful, you first have to show not only that bubbles cause DCS, but that more bubbles are more likely to cause DCS than fewer bubbles. You have not shown that....you just suppose it to be true. What if only a few bubbles cause DCS, but they are at exactly the wrong place at the wrong time? I'm afraid you are building a narrative based on an unproved assumption, and then trying to make all the data fit your narrative.
     
    ginti, VikingDives and PfcAJ like this.
  3. Wibble

    Wibble Contributor

    # of Dives: 500 - 999
    Location: UK
    1,005
    755
    And we're back to the beginning again. Decompression seems to be a voodoo science in that we still don't fully understand what's going on. All we know is that the decompression algorithms sort of work, but people still get "undeserved" bends for a variety of reasons.
     
    CAPTAIN SINBAD likes this.
  4. CAPTAIN SINBAD

    CAPTAIN SINBAD Divemaster Candidate

    # of Dives: 200 - 499
    Location: Woodbridge VA
    2,916
    1,078
    Nobody has ever shown that. Bubbles causing DCS is the underlying assumption behind most of the decompression research. Yet of all the assumptions it is the most logical one. Mark Powell explains it in the following words ...

    "If bubbles are formed well within our M-Value limit then what use are the M-Values? And if bubbles form, and yet there are no signs or symptoms of decompression sickness then how can we say that bubble formation causes decompression sickness? If it is not bubble formation that causes decompression sickness than what does cause it?"

    (Mark Powell in Deco for Divers, Page 110)

    I was chatting with Bob Sherwood from GUE over phone. He said, "I can teach you decompression theory in three words. Are you ready?"

    I said, "Ya."

    He says, "WE DONT KNOW!
     
  5. wetb4igetinthewater

    wetb4igetinthewater Instructor ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Seattle
    5,827
    4,147
    PADI, SSI, SDI, and IANTD all have solo diver courses. I think ANDI does too.

    What's wrong with a bit of fringe?
     
    decompression and Wibble like this.
  6. ginti

    ginti DIR Practitioner

    # of Dives: 200 - 499
    Location: Lyon, France
    741
    446
    I was genuinely interested in understanding what you wanted to say, no sarcasm, but apparently, you do not care (and that was not nice by you). Before leaving you to your ideas, just let me highlight a last point. This:

    is exactly the opposite of that thing called science.

    In science, you make a hypothesis, you test it, and ONLY if you can prove it, you accept it. Or, if you can disprove it, you reject it. What if you cannot prove it and neither disprove it? You continue to test it - and you strictly avoid reaching any conclusions based on it until you can definitively prove it or disprove it.

    What you are doing here is:
    - you have a (some) hypothesis about DCS ;
    - you cannot prove it (them) and neither disprove it (them);
    - anyway, you reach some conclusions based on what you think is most logical***
    Independently from the solution to the problem, your approach is scientifically wrong and dangerous. Good continuation :)

    *** By the way, I personally do not see any logic in "more bubbles -> more risks of DCS". If bubbles in the blood are (one of) the root cause(s) of DCS, it means that some parameters associated with the bubbles need to reach some critical values to start the mechanisms of DCS; for instance:
    1) bubbles reaching a certain size
    2) bubbles having a certain shape
    3) bubbles having a specific speed relative to the blood flow
    4) number of bubbles in the blood flow
    The fourth option is the one you consider the most logical. For me, given this small set, the most logical is a combination of 1 and 4. But what about other factors? What if bubbles in the blood flow do not have any relation with DCS? This can absolutely be possible, for instance, if the nitrogen in the tissues is primarily responsible for DCS (as it is my understanding), and the number of bubbles in the blood has nothing to do with that. In this case, bubbles in the blood are just a consequence of another phenomenon, and what is the parameter more related to this original phenomenon? Size? Distance between bubbles? Total number? And I can continue as long as I want... but it's just speculation, as I said, without any scientific value...
     
  7. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: U.S. East Coast
    11,826
    9,755
    For all the grief some of us are giving you, I feel like I ought to cut you a little slack, and also tighten the line a little bit.
    The slack: you are trying to justify UTDs methodology. That is not your job. If they can't justify it, you surely can't! Your job is to see if their methodology works for you. If it does, good, use it. If it doesn't, then use something else.
    More slack: there is likely a middle ground between we know everything about deco, and we know nothing. You do not buttress your arguments by saying we really don't know anything. That is grade-school logic
    Tightening: Quoting Mark Powell is not very convincing...he is a good writer and has done us all a service in make some of the less transparent material a bit more accessible, but he is not the deco expert. Quote someone like Dr. Simon Mitchell.
     
    arthurng311 and grantctobin like this.
  8. ELCAM

    ELCAM Contributor

    # of Dives: 100 - 199
    Location: Mooresville, NC
    94
    41
    The RD 3.0 is very close to GF 40/70.



    listen to the talk with Dr Simon Mitchell starting at minute 34. Dr Mitchell states that he personally dives a GF 50/70...so UTD isn’t that far off...

    I personally run a computer as a gauge and another set in GF... my UTD instructors didn’t seem to care that I did that.
     
    CAPTAIN SINBAD likes this.
  9. ELCAM

    ELCAM Contributor

    # of Dives: 100 - 199
    Location: Mooresville, NC
    94
    41
    For what it’s worth AG is gone and Ben Bos as the new training director is doing an awesome job..they aren’t trying to sell/push gear anymore...you will even see Ben wearing Halycon gear in his videos..couldn’t imagine that would have flown when AG was still there.

    I really do believe Ben Bos and Jeff Seckendorf are trying to make it a training first agency so I’d expect a lot of evolution in the future as science evolves.
     
    JustinLoos1985 and RayfromTX like this.
  10. CAPTAIN SINBAD

    CAPTAIN SINBAD Divemaster Candidate

    # of Dives: 200 - 499
    Location: Woodbridge VA
    2,916
    1,078
    Sorry ginti. I didn't mean to ignore. I had my first vaccination shot and it is knocking me out so I had intended to respond when I was a little better. Hopefully, the following will address a lot of confusion that some of this earlier conversation has created.

    During the early days of decompression, (1907, Scott Haldane era) it was believed that the human body has a limit to how much nitrogen it can hold in a dissolved gas state. Just like a sponge has a fixed limit of liquid it can hold when saturated, human body was also believed to have such a limit. When nitrogen exceeded that limit, the rest of it would form bubbles. These bubbles will travel through the veins and arteries and each vein and artery splits into two smaller ones and each of those into two further smaller ones. Bubbles would travel through this network and soon find a vein not wide enough to pass through. Then you will have a blockage. Soon more bubbles will collect at that blockage much like a traffic jam and, depending on where in the body this traffic jam is happening and how big is it, you will have symptoms.

    This perception gave birth to the "dissolved gas" model. It is called "dissolved gas" because it attempts to calculate how much nitrogen can be kept in a dissolved form as that harmless. It attempts to avoid nitrogen build up beyond that, as bubble formation is attributed to whatever nitrogen you accumulate beyond that point. In essence, as long as you are surfacing with all the nitrogen in dissolved state you are safe and the reason why people bend is because nitrogen accumulated beyond that limit has resulted in bubbles in the blood. Earliest calculations on this assumption began with some basic notes by Haldane, shown below.

    Haldane%27s_Decompression_table-I_in_ft_and_psi.jpg

    When these limits were implement in diving, decompression hits dropped and we became more and more convinced that good nitrogen is dissolved and bad nitrogen is the one exceeding maximum saturation and generating bubbles. These models were repeatedly tested and calculations were updated and dive tables with fixed limits were born. US Navy tables, Workman tables and Buhlmann algorithm are all calculations based on the assumption that the body can store a certain amount of nitrogen in a dissolved gas state. Haldane called it "critical limit" which in theory is a state of no bubbles and no symptoms.

    In the 60s, Doppler technology was used for the very first time to check divers bodies for bubbles. We thought that by testing divers who had DCS symptoms we will find bubbles and by testing divers without symptoms we will find no bubbles but that was not the case. To every ones surprise, all divers regardless of whether they were bent or not, had bubbles! This gave birth to the notion that we are all bent after every single dive or the more modern slogan, "Every dive is a decompression dive!"

    You could argue that Haldane's work and the Neo-Haldanean calculations had become scientifically useless. Since terms like "Critical limit" had become unscientific, scientific community struggled to find suitable language. New terminology was invented. Bubbles that were in the bodies of divers who did not have symptoms were called "silent bubbles" or "non-symptomatic bubbles" and those that were in the bodies of divers with symptoms were called "symptomatic bubbles."

    "... discovery of silent bubbles threw quite a large spanner into the theoretical basis of traditional (dissolved gas) decompression theory. Two alternate views developed on how to deal with the spanner. The first view was that dissolved gas model has served us well for many, many years and many millions of dives have been conducted with an acceptable level of safety. As a result there is no need to completely reject the dissolved gas model. Instead a number of modifications can be made to the model to take into account the existence of silent bubbles.(Mark Powell, Deco for Divers, Page 111)

    The Buhlmann decompression model which you will see in a lot of technical diving computers is based on the above premise.

    "The alternative view was that the discovery of silent bubbles highlighted such a fundamental flaw in the dissolved gas model that a mere tweak was not sufficient to solve the problem. Nothing less than a new theory which attempted to explain the formation of silent bubbles as well as the cause of decompression sickness was the only way forward."(Mark Powell, Deco for Divers Page 111)

    This school of thought would give birth to the introduction of a totally different scientific discipline called "Bubble Mechanics." This would have been an interesting time to be a diver because on one hand you had dissolved gas models with a history of demonstrating "acceptable level of safety" but they were scientifically wrong. On the other hand you had a totally different set of calculations happening in bubble formation and growth which were more in acknowledgment with the findings of Doppler but had no test history with real humans. Instead of dive data, bubbles were being injected in Jello like substance and Jello was being subjected to pressure to see how bubble works!!! Yup imagine a science being backed by millions of dive and another with gelatin test. Modern Science and traditional common sense were on a collision course.

    Tables generated by bubble control were calling for deeper stops to be made as these stops were not happening at the same depth as the stops generated by dissolved gas models or its most modern form until that time, The Buhlmann Algorithm. Thus dissolved gas models and bubble mechanics were blended together to create "Dual Phase" models.
    VPM- (Varying Permeability Model) and RGBM (Reduced Gradient Bubble Model) were what came out of this merger. These models would cause you to stop deep first in order to control or shrink the size and quantity of bubbles picked up by Doppler technology. As you ascended, these models would change their motivation and start to behave like a dissolved gas model.

    Since advances in bubble mechanics were now looking to be the way forward, US Navy that had developed one of the earliest dissolved gas models now considered adopting this, more modern approach. In order to test these, they conducted the famous NEDU study. Since bubble mechanics and the deep stops it generated did not have as much of real diving behind it, Navy was to take human volunteers and subject them to actual decompression risk with deep stops. Outside the military such an experiment would have been considered unethical. The results showed that with all the impression of modernity behind them these bubble models failed to generate the same safety levels that were displayed by tried and tested dissolved gas models, which as Doppler testing had shown, were based on a totally wrong premise.

    Sooo where do we stand today?

    Bubbles have not gone anywhere. They are still inside us on every dive regardless of where we stand in relation to NDL. The problem is that bubble is not a balloon and bubble mechanics is an extremely messy science. At this point, this science is so unreliable that any attempt to use it, even in a dual-phase algorithm compromises the safety of a traditional model which is based on a false assumption. All great minds, including Mark Powell, Dr. Simon Mitchell and present UTD leadership are accepting of the fact that bubbles are present inside us in every dive, no body knows where to add the deep stop to prevent them from over-expansion. In fact none of them even know how to calculate it.

    "There is a clear acknowledgment by me and by David Doolete and by all the scientists involved in decompression research that you have to have a deepest stop in a dive and my message these days to try to get around all this controversy is that the question should not be 'do deep stops work? The question should be how deep should our deep stop be?" (Dr. Simon Mitchell in conversation with UTD's training director Ben Boss and CEO Jeff Seckendorf, TIME CODE 12:06)



    As a technical diver, you are supposed to know that you are diving in an area where a lot of science is untested. When you look at science and ask "What am I supposed to do?" Science is looking back at you and saying, "You are my test rat. I will make up my mind based on what happens to you!"
     

Share This Page