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Nitrox benefits for Cozumel diving

Discussion in 'Cozumel' started by tracydr, Jul 23, 2013.

  1. Christi

    Christi PADI MSDT/Dive op owner ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: Cozumel, MX
    7,235
    4,704
    I agree with you in theory - but my point is that Tracy's information is misleading and inaccurate in the way she stated and appears to understand it (I could be wrong of course - just basing it on how I interpreted her post). On nitrox, if exceeding the air limits, you are still absorbing more nitrogen even if not reaching the nitrox NDL limits - but reaching nitrox NDL limits is certainly no different than air on air limits. The point is that while it can decrease nitrogen loading, it s not necessarily true - and often NOT true depending on the diver and the profile. In her example of using 28% on a deeper dive to extend the bottom time, a diver with good air management could in fact reach and exceed the nitrox NDL limits.
     
  2. AggieDiver

    AggieDiver Contributor

    # of Dives: 200 - 499
    Location: Houston, Texas
    1,109
    683
    The way I have always tried to explain it in general terms is that you can dive nitrox to be safer, or dive nitrox to get more bottom time...but not both. Yes there is a middle ground in there where you can get a slightly longer bottom time and some small measure of extra protection...but in general, if you are diving nitrox to expand your bottom time, you are not likely to be measurably safer than diving on air. On the other hand, if you dive the exact same profile using nitrox that you would on air, you are probably measurably safer from DCS, notwithstanding experiences like Christi's, which point out the unpredictability of DCS.
     
    tracydr and Christi like this.
  3. Skittl1321

    Skittl1321 Contributor

    # of Dives: 25 - 49
    Location:
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    I don't know how much he actually knows about this, but when I asked my OW instructor (whose full time job is chemical engineer, so he's science-y) about Nitrox on air tables he said it wasn't actually worth it, because the risk of DCS is so very small, that adding safety to it doesn't actually add significantly to the safety factor. (I think his exact words are 'both are very small numbers that round to zero, and margin of error in any study would be too great to show a significant increase in safety").
     
    D_B, awap and Dave Dillehay like this.
  4. Lorenzoid

    Lorenzoid ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: I just don't log dives
    Location: Atlanta, USA
    10,371
    7,237
    Whether there have been studies of the benefits of diving Nitrox on air tables would be a good question to post over in the Diving Medicine branch. It's sound logic that there would be benefits, but whether the difference has actually been found to be statistically significant in a study is a good question.
     
  5. ronski101

    ronski101 Contributor

    # of Dives: 500 - 999
    Location: redondo beach, calif
    472
    35
    It would be very interesting to see some DAN statistics on the number of divers who got DCS using nitrox vs those using air. My guess is it would be similar to the statistics on people who got in accidents in snow country driving their 4WD vs 2WD. Thinking they are safer in the 4WD they drive like their is no snow on the ground and consequently crash while those in the 2WD drive more conservatively and avoid the accident they otherwise would have been in had they been in the "SAFER" 4WD.
     
  6. Karibelle

    Karibelle Contributor

    1,216
    460
    We forgot to add this to the "dead horse" thread.
     
  7. AggieDiver

    AggieDiver Contributor

    # of Dives: 200 - 499
    Location: Houston, Texas
    1,109
    683
    I doubt it has been studied in any controlled form. The population of divers diving nitrox to air profiles is likely to be simply too small to get any real world statistical value since DCS hits are pretty rare to begin with. What I am referring to by using the term "measurable" is simply the quantity of nitrogen you will absorb into your tissues. If you dive nitrox to the nitrox NDLs, you will have roughly the same nitrogen saturation in your body as you would diving air to the air NDLs. If you dive nitrox to the air NDLs, you will likely have measurably less nitrogen absorbed into your body. Whether that actually leads to a lower risk of a DCS hit, maybe one of the dive docs can chime in, but my own personal philosophy is that it can't hurt, and I do believe I feel better after a dive with nitrox than a dive with air. So maybe I am just old or something...
     
    Christi likes this.
  8. robint

    robint Contributor

    # of Dives: 500 - 999
    Location: Albuquerque, NM
    6,540
    1,150
    The ONLY reason to dive Nitrox is to reduce nitrogen load.
    Your nitrogen load increases throughout your vacation, regardless of what your computer says, you will still have some residual nitrogen in your tissues for days after you are home.

    The older you are, or the more out of shape you are, or the more medications you are taking = your body's efficiency to get rid of this nitrogen effectively.

    This does not mean that diving Nitrox will prevent DCS. I still believe than dehydration, alcohol consumption, erratic dive profiles, and general health are biggest causes of DCS... MY OPINION. But, all said, I still use Nitrox whenever it is available for most of my dives on a trip.

    robin
     
    tracydr, Christi and judydivescoz like this.
  9. uncfnp

    uncfnp Solo Diver ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: North Carolina
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    5,649
    Here is one study
    Evaluation of critical flicker fusion freq... [Diving Hyperb Med. 2010] - PubMed - NCBI

    This thread discusses this and another study if anyone is interested
    http://www.scubaboard.com/forums/diving-medicine/460403-silent-bubbles-fatigue-tiredness.html
     
    tracydr likes this.
  10. Peter69_56

    Peter69_56 Scuba Instructor

    # of Dives: 500 - 999
    Location: Australia
    1,541
    639
    I would have to disagree with him to a degree on the basis that DCS is very unpredictable in particular on the basis of personal physiology and it depends on the person if DCS risk is small or higher. My wife for instance is more susceptible to DCS than I, and Nx does mitigate it. She has managed to continue rec diving based on using Nx over air by virtue of the fact with rec diving her safety margin is greater.

    With deco diving her pooch is very much screwed as it doesn't help at all to any degree. We used 50% Nx for deco and used air deco tables as well as longer times at 3 m and she is still affected.

    I think in her case her risk is continual nitrogen loading over days. In the case of deco this is more pronounced. I have done virtually the same profile or even more exposure on more dives but never been affected.

    If you were to take 10 people similar to me (god help the world) and used and not used Nx it would make little difference, but 10 of my wife would show a clear contrast.

    Perhaps he is right theoretically but not in a practical sense as we are not all (as humans) the same theoretical model.
     
    tracydr likes this.

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