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Is UTD still a "fringe" organization?

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

  1. decompression

    decompression Instructor...seriously...

    # of Dives: 5,000 - ∞
    Location: Victoria, BC, Canada
    4,208
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    I only know of 2 agencies of the 400+ that recognize solo diving.....could be more but that’s a lot of fringe.
     
    rjack321 and AfterDark like this.
  2. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
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    This was argued to exhaustion in the various deep stop threads in various forums, including ScubaBoard. The only person arguing this side of the point, though, was Ross Hemingway.

    No one says that venous gas emboli (VGE) is causative of DCS. What has been demonstrated clearly is that higher VGE loads are associated with DCS. The NEDU study that famously saw the disadvantage between deep stops and shallower stops based their conclusions on actual DCS. No study will be approved today with that determiner--too dangerous. VGE are the best indicators because of their association, imperfect as that may be.

    Mark Powell's recent research on this (we are FaceBook friends) was very much centered on VGE, and he performed a test that to my knowledge had not been done before which had remarkable results. He tested divers for VGE after their dives, and he did not find a big difference between deep stop divers and shallower stop divers, but then he tested again over time, and the difference was significant. WIth the shallower stop divers, the VGE dropped off rapidly. With the deep stop divers, though, the load stayed high for a long time. It has been a while since I saw the figures, but as I recall, in some cases, VGE initially increased with time.
     
    Nirvana, Wibble and OTF like this.
  3. CAPTAIN SINBAD

    CAPTAIN SINBAD Contributor

    # of Dives: 200 - 499
    Location: Woodbridge VA
    2,920
    1,080
    Correct. Just to be clear, deep-stops in context to technical diving have been addressed quite extensively and we are no longer talking about those. UTD does not propagate those and I do not believe Mark Powell would either. Half-stops in recreational diving on the other hand are a totally different phenomenon and Powell believes that DAN study is more relevant to address those than the US Navy study so he recommends doing those to additional stops to address post-dive fatigue.

    DAN study used Doppler testing to check Bubble score index among divers in three categories.

    1. Who were skipping stops and making a straight ascent.
    2. Who were adding a traditional computer generated safety stop of 5minutes at 6meters. This is what a typical diver following his or her computer would do.
    3. Who were combining a 15meter stop to the traditional 5 minutes @ 6 meters. This is similar to the approach that UTD has.

    What I found interesting was that the difference between the first two in terms of BSI was quite minimal frankly. Like BSI of 8.78 in category 1 would drop to 8.10 when you added your computer generated stop. But when you supplemented your computer generated stop by adding a deeper stop @ 15m then the BSI would come down to 3.50!!! That was a huge safety margin that was being created by adding that stop. Now this stop, which would bring down the BSI from a whopping 8.78 to 3.50, was happening outside of computer generated algorithms so if you wanted your computer to generate it for you then you would have to know enough about gradient factors to play around with them quite a bit.

    This is what Mark Powell wrote:

    "The inclusion of additional safety stop on recreational dives is likely to be more widely adopted in the future in an attempt to provide an additional safety margin and as a way of reducing post dive fatigue." (Mark Powell, Deco for Divers Page 113)

    In my personal correspondence with him recently, he insisted that recreational divers should look at this study instead of NEDU study as this is more in line with their dive profiles. UTD presently favors this approach in their recreational profiles and in my own dive circle, I know a few people who report much less fatigue when they add half stops.

    I plan on doing more dives with this method so that I may have more of a first hand experience with this method that makes you do more deco starting from deeper depth. Presently my own views are based on the above and what certain individuals who have confessed some very positive results without even being aware that there is a bubble score study by DAN that confirms their own reduction in post dive fatigue.


     
  4. ginti

    ginti Contributor

    # of Dives: 200 - 499
    Location: Lyon, France
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    Now I do not even understand what you mean by "being bent". As @boulderjohn already mentioned, VGE is not necessarily causative of DCS (although it can).

    So now I have three questions:
    1 - what did you mean when you said "significant" in your previous post?
    2 - what do you mean by "being bent"?
    3 - can you link the article you cited?

    Any help is appreciated, many thanks
     
    grantctobin likes this.
  5. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
    27,950
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    Is this the 2002 study you are talking about? You do realize that is generally not held in high regard by the scientific community because of methodological flaws?
     
    grantctobin likes this.
  6. CAPTAIN SINBAD

    CAPTAIN SINBAD Contributor

    # of Dives: 200 - 499
    Location: Woodbridge VA
    2,920
    1,080
    I am unsure about the date but yes there is a flaw in that study at least in my own observation. We do not know whether the reduction of bubble scores in group 3 was due to the additional decompression they did on top of their 5mins @ 6meters or if it was because that additional time started deeper. In other words, can we have exactly the same reduced bubble score if we add that additional deco time, not to any deep stop, but to to their standard stop at 5 mins @ 6 meters?

    We do not know. That study unfortunately never had a fourth group that was distributing the exact deco time in the shallow stop to give us a comparative reply. Until that happens, this study is all you and I have, to make our decisions right? Based on this, the guy who follows the computer and the guy who adds additional deco time deeper, the latter clearly wins so out of those two, who would you rather be? Unfortunately those were the only categories tested so you have to pick one out of the two until more testing gives us a clear answer.
     
  7. tursiops

    tursiops Marine Scientist and Master Instructor ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: U.S. East Coast
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  8. KevinNM

    KevinNM Contributor

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    Everyone having bubbles and no good correlation to actual DCS suggests that bubbles are currently not a very useful indicator. There is something missing that is much more important. No idea what this is
     
  9. CAPTAIN SINBAD

    CAPTAIN SINBAD Contributor

    # of Dives: 200 - 499
    Location: Woodbridge VA
    2,920
    1,080
    Based on that logic, Spisny study should be rejected too. UTD test divers who did 75% stops did not show any external DCS symptoms. Why was it seen as such a nail in the coffin for deep stop argument? Because bubble index showed that deep stops were generating more non-symptomatic bubbles in relation to those test subjects that had followed shallower gradient factors. No one got symptomatically bent in that study.
     
  10. Ayisha

    Ayisha Contributor

    # of Dives: 500 - 999
    Location: Toronto, Canada
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    I saw a presentation by Dr Bruce Cameron, from our Defense Research and Development Canada (DRDC) at our Scuba Swap a few years ago, and he played Doppler audio of bubbling in the blood of people at rest and active - without diving. He pointed out the loud crackling and pops that the bubbles made when someone even just bent their knee, for example.

    He also played the audio of bubbling at various points after diving, and how much faster and louder the crackling and popping was, and how it dissipated over time.

    He showed that bubbling in the blood occurred with or without diving, while the body is at rest or active, so bubbling alone is not an indicator of DCS. It is more connected to the frequency and size of bubbles.

    I think Dr Cameron was working on developing some kind of blood test to detect DCS.
    A quick google search came up with this paper he wrote, "Effects of Hyperbaric and Decompression Stress on Blood":
    https://journals.sagepub.com/doi/full/10.1177/1076029614568712
     
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