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  1. #1
    Established TDF Member MikeF's Avatar
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    comparative evaluation of compartmental versus ratio deco


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    I found this an interesting read, especially the use of inflammatory markers as an early warner for DCS. It does give an interesting idea of physiological stress caused by the gas loading, even with no clinical symptoms of DCS. This could be a good explanation for "unexpected" bends after multiple dives or other physiological stressor, even if within conservative limits.
    Rich

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    rEvo-lution iamyourgasman's Avatar
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    Quote Originally Posted by MikeF View Post
    Not so light reading, even for this semi-experienced clinical researcher. Very well done study, with interesting, hypothesis generating results. The answer (as many many times) is that we need more data! I hope the research team will be successful in obtaining more funding, so they can expand the knowledge base. It appears air dives and more deep stops stress the human immunology response more.

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    only skim read so far but a 30/85 GF profile compared against a Ratio profile? Apart from the elongated stop at switch depth on the Ratio aren't these 2 very similar in terms of deep stops?

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    rEvo-lution iamyourgasman's Avatar
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    Quote Originally Posted by JonG View Post
    only skim read so far but a 30/85 GF profile compared against a Ratio profile? Apart from the elongated stop at switch depth on the Ratio aren't these 2 very similar in terms of deep stops?
    Read it in detail, their methods section describes the profiles very well.

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    I know a bit about this study. It is included in an article I just co-authored with Simon Mitchell about the issue of deep stops. It will be published in the PADI Tech forum soon. The reference in the article to this study is brief, but there is a lot more that could have been said.

    The study was initiated by (and I believe financed by) UTD. UTD owner Andrew Georgitsis published a video before it started raving about how the study was going to show the superiority of the UTD ratio deco program to a common Bühlmann algorithm. (This is, of course, not the way you are supposed to approach an objective scientific study.) When the intention to do the study was first announced, several people criticised it, arguing that it was set up to make the UTD system look good. They were especially critical of the GF high of 85, which made for a different length of total deco, with the RD group getting more time to decompress in the shallow stops. This should have given the RD group an advantage.

    Since then, UTD changed to a new version of Ratio Deco, Ratio Deco 2.0. I am not totally familiar with it, but I believe it makes the first stop at 2/3 of average depth rather than 3/4, and I believe it also drops the S-curve from the middle ascent range.
    Last edited by JohnAdsit; 12-04-2019 at 06:37 PM.

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    There is some interesting and related stuff on the SB Re-Evaluating my GF thread which demonstrates that holding the gas switch stop can lessen ISS but think it was mainly applicable to air/nitrox dives not trimix.

    Still not sure a GF low of 30 was representative of a suitably dissimilar profile, but it does highlight the issue with deep stops.

  8. #8
    rEvo-lution iamyourgasman's Avatar
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    Quote Originally Posted by JonG View Post
    There is some interesting and related stuff on the SB Re-Evaluating my GF thread which demonstrates that holding the gas switch stop can lessen ISS but think it was mainly applicable to air/nitrox dives not trimix.

    Still not sure a GF low of 30 was representative of a suitably dissimilar profile, but it does highlight the issue with deep stops.
    The biomarker data they presented is convincing. It appears GF low of 30 puts you shallow enough to diminish the inflammatory response, compared to the deeper stops in RD. I’d be interested to see if a shallower profile like the GF low of 60 that I’m using would be similar (or perhaps worse!) than the 30/85.

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    Quote Originally Posted by iamyourgasman View Post
    The biomarker data they presented is convincing. It appears GF low of 30 puts you shallow enough to diminish the inflammatory response, compared to the deeper stops in RD. I’d be interested to see if a shallower profile like the GF low of 60 that I’m using would be similar (or perhaps worse!) than the 30/85.
    On a typical dive, 30/85 produces a much shallower first stop than UTD Ratio Deco's 75%. A 50/70 profile, now very popular among knowledgeable tech divers, has the first stop even shallower.

    The ultimate goal is to try to find the best possible ascent profile, which of course includes the most effective depth for the first stop. Finding that depth requires us to maintain an open mind and accept that because our understanding has not yet reached perfection, we must constantly seek and evaluate new information as it becomes available.

  10. #10
    Established TDF Member Barrygoss's Avatar
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    So how many ratio deco (not the UTD fucked us versions) compare with the profile investigated.

    Do either GUE or UTD do air to 50m.

    Should have done an ‘88 to this profile test.

    B
    Rebreathers are like women; they pretend to love you, whilst taking all your money and trying to kill you.


 
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