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Deep Stops Increases DCS

Discussion in 'Technical Diving Specialties' started by Divetech99, Dec 8, 2014.

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  1. Divetech99

    Divetech99 Solo Diver

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    DENLASCUBA and Omisson like this.
  2. Kevrumbo

    Kevrumbo Banned

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    Look at the Bottom Mix Gas used in the NEDU Study link above (essentially Deep Air):
    This is the simple main practical point IMO/IME, to take away from the study:

    Of course you're going to have significant residual inert Nitrogen and potentially on-gas N2 at your deep stop & perhaps even possibly at intermediate deco stops on Eanx50 which may encroach on critical slow tissue M-values as well --if you were using a working bottom mix with a high fractional N2 content to begin with like Air. Plan accordingly, use a computer to track your inert tissue loading (i.g. Shearwater Petrel) and be prepared to extend your 6m depth 100% Oxygen deco profile along with a stand-by IWR contingency protocol.
     
    Last edited: Dec 9, 2014
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  3. tomfcrist

    tomfcrist NAUI Instructor

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    The profile was rediculous. 170/30minutes would give me 74 minutes of deco without deco gasses. That's 104 minutes vice 174. What the hell were they doing for the other 70 minutes?
     
  4. LiteHedded

    LiteHedded Great White

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    Read the thread on this on rebreather world. Dr Doolette answers a lot of these types of questions there
     
  5. Divetech99

    Divetech99 Solo Diver

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    Yes, you're right. looks like their deco time was longer than normal deco time. Why? What model were they following or testing?
     
  6. rjack321

    rjack321 Captain

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    Two Navy models. Basically the conclusion was for any given deco time you cannot substitute time at say 50ft in lieu of time at 30ft without increasing your DCS risk. Assuming backgas (air) deco. No great surprise there.

    They did not test the effect of for instance doing more time at 70ft after switching to EAN50 and then doing less time at 30ft on EAN50 before switching to O2.

    Its only so so relevant to how OC divers do deco with gas switches. Read the long winded RBW thread and Simon Mitchell's and Dr. Doublette's Q&A if you want more info on what they tested and why.
     
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  7. LiteHedded

    LiteHedded Great White

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    Gue has changed some of what they're teaching based on studies like these. David was just down speaking at the gue conference. Would have been a good time to ask him about their study
     
  8. Divetech99

    Divetech99 Solo Diver

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    It would be interesting to know how GUE and UTD will change (or not change) their Ratio Deco and Min Deco procedures. Can we get David to share?

    ---------- Post added December 10th, 2014 at 11:44 AM ----------

    A separate question. Dive computers have the feature to turn on the Deep Stop mode and set it for 1 or 2 minutes. I assume that these are not arbitrary deep stops but built into their decompression algorithm. Given this, what is the group's recommendation? Turn on deep stop in the dive computer or turn it off?
     
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  9. Kevrumbo

    Kevrumbo Banned

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    Again:

    Look at the Bottom Mix Gas used in the NEDU Study (essentially Deep Air):
    Why do you think this will affect Deep Stops in Ratio Deco? Correct application requires the use of standard Helium mixes with Eanx50 & O2 deco for this particular depth: IOW, the study's parameters and conclusion above does not apply. . .
     
    Last edited: Dec 10, 2014
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  10. Divetech99

    Divetech99 Solo Diver

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    Min Deco uses Air and is part of GUE standards for Rec.
     
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