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Nitrox benefits for Cozumel diving

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

  1. ggunn

    ggunn ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Austin, TX, USA
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    D_B, nimoh and Skittl1321 like this.
  2. Lorenzoid

    Lorenzoid ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: I just don't log dives
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    I don't think these studies address what Skittles' instructor was talking about. These relate to fatigue caused by sub-clinical bubbles, not to the idea that taking a full-blown DCS hit can be made statistically less likely by diving Nitrox on air tables. If I understood correctly, her instructor believed that the statistical likelihood of taking a DCS hit on air is already so low that any reduction in the likelihood that might be achieved by diving Nitrox on air tables is statistically insignificant. My guess is that gathering data to study this in a controlled way would be exceedingly difficult. But I suggested posting over on the Diving Medicine branch to see if anyone from DAN or Duke Dive Medicine might weigh in.
     
    Last edited: Jul 24, 2013
    tracydr likes this.
  3. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    I agree with her instructor fully, and that statement is included in the training materials for at least some of the certifying agencies.

    Let's look at the statistics. The statistical likelihood of you getting bent on a recreational dive while breathing air is something like 0.001%. How much safer can you make that by using nitrox on an air profile? Even if you make it twice as safe, you are changing the likelihood of getting it by 0.0005%. Congratulations.
     
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  4. Peter69_56

    Peter69_56 Divemaster

    # of Dives: 500 - 999
    Location: Australia
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    If you are that person in the 0.0005% it becomes very important.

    For me it doesn't matter that much, for my wife, perhaps essential to allow her to continue to dive
     
    tracydr likes this.
  5. uncfnp

    uncfnp Solo Diver ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: North Carolina
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    Sorry Lorenzoid, I thought you meant studies showing any ​benefit.

    ---------- Post added July 23rd, 2013 at 07:48 PM ----------

    I have to agree with Peter69_56 on this. If you are one of the majority of divers with no known increased risk of DCS the reduced DCS with nitrox is not significant and if you are using it solely for that benefit it's probably overkill.

    But for those of us at known increased risk, I feel the statistics are skewed. The more relevant statistic would be a study with a subgroup of divers with known risk factors for DCS that compared nitrox vs air. I'm not aware of such a study but I am suspicious that it would indeed show a greater statistical significance.

    The fact that DAN recommends nitrox on air tables to such divers also leads me to believe that would be the case as well.
     
    Last edited: Jul 23, 2013
    tracydr and chillyinCanada like this.
  6. tracydr

    tracydr Divemaster

    # of Dives: 500 - 999
    Location: North Carolina, 3 miles from South Carolina
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    My husband and I will run into NDL easily when on a dive trip, especially on a live aboard or where we are shore diving if we dive air, which we sometimes are forced to do because of the lack of availability of nitrox in places like Catalina during the off season. ( or Channel Islands on our favorite charter)
    I hate being limited by NDL. We don't mind doing 5-10 minutes of deco and we have the computers/experience and air capacity available to do this but I would much prefer just diving nitrox and not making this an issue. Plus, we're not getting any younger and we do like to dive in that 80-110 foot range at times, where some nitrox is just perfect for extending our bottom times, if you have the right mix. I have never regretted learning nitrox. If nothing else, you will gain practice with tables, partial pressures, and more information about how nitrogen and oxygen effects the system, assuming you actually have somebody that teaches you and not a one hour resort class.
    Hopefully, most SB members see the value of education and won't do the 60 minute resort class just to get the card.

    ---------- Post added July 23rd, 2013 at 05:29 PM ----------

    Christi- Nitrox is readily available but may not aways be available in the mix desired. However, if more people insist in a certain blend, it will eventually be available. If people refuse to come back and let the operators know that they aren't coming back because of lack of nitrox, I bet nitrox will become readily available in a hurry in all sorts of blends. No reason it can't be.
    Just like if more people let the dive OP for the Channel Islands know that we won't be diving with them anymore because they don't provide nitrox ( and yes, I'm seriously considering this), they will eventually need to provide for their customers. It's just such a great place to dive that's its hard not to go to, even with the lack of nitrox.
    It's simple-if I don't go to Cozumel because nitrox isn't cheap,free or readily available and its included in the package at a competitor, and this becomes important to enough people that they choose not to dive Cozumel, Cozumel will either need to provide nitrox in their dive packages or lose money.
    Cozumel doesn't compete with Bonaire, its simply not the same type of diving. Its different and that's fine. I cut my teeth on Puget Sound so I'm spoiled on shore diving and cold water diving.
    For me, nitrox is important, because I hate being limited by the amount if bottom time I can have. For other people it simply doesn't matter. They will dive a couple of one hour dives, have some drinks and be happy. Different strokes for different folks. This is also why my husband and I love shore diving and or live aboards.
    Cozumel was one of my favorite places, when I lived in Southern OK and it was really convienant to get to. But, I really don't like to pay for the two tank boat dives. Now, in Phoenix, its not that easy to get to and it just gets dropped down the list. There are so many other great places in my list I want to see before I go. I still have the whole South Pacific, Red Sea, Australia, Truk,Palau,Indonesia, not to mention I haven't even begun to cave dive which is way up there number one on my bucket list!
    Plus, that's not even beginning to list the cold water areas and I do love cold water diving, too.

    ---------- Post added July 23rd, 2013 at 06:12 PM ----------

    That's too bad that an instructor says something like that.The longer I'm in diving, the more I've been around people who've experience DCS. Maybe its just because I'm meeting more serious divers but, I'm beginning to think that my earlier thinking was far too cavalier. Because, I thought like your instructor-DCS is really rare so it will never happen to me. Guess what, DCS has happened to lots of my friends and I think it may have happened to myself and I don't even know it.
    yes, it's rare, per dive. But, dive a lot and its not so rare.
    For me, any margin of extra safety has become more important. So,longer safety stops, richer mixes, different GFs.
     
    Last edited: Jul 23, 2013
    Peter69_56 and Augustus like this.
  7. Peter69_56

    Peter69_56 Divemaster

    # of Dives: 500 - 999
    Location: Australia
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    My wife took a small hit while in PNG. She thought it was just a rash, and I argued it was DCS. She wouldn't have it. I managed to talk her into using Nx if she was going to continue diving and she did have a half day break during the period too. She showed no indications of another hit during that period. that on its own is not conclusive.

    We then went to Brunei and did deco diving over 10 days, after day 4 she took a hit, but once again it was not obvious that it clearly was a hit. Day 6 saw a clear and obvious hit with associated pain. Looking back, it became clearly obvious that 2 days previous it was DCS and in PNG as well (same skin symptoms just larger area). I believe the PNG incident was caused due to continual diving and nitrogen build up with no break days. The half day break and Nx usage allowed her body to clear the nitrogen loading and thus no additional hit at that time.

    Our strategy now will be to do the next rec dive very conservatively and don't get near NDL, if possible use Nx on every occasion creating a large margin. Also have a break day rather than say 2-3 dives a day for 6 days, maybe have 2 days diving then a break day.

    If this works then we may do short deco dives with a dive day then break day. All deco dives being timed shorter dives rather than being gas limited. The critical thing being to keep the daily body nitrogen loading down (generally speaking, not scientifically). From a layman's point of view this seems to work in her situation given the evidence to date.

    SO in saying all of the above, I agree that the figures above, while may be statistically correct are skewed on the basis of sampling non DCS vs DCS. Application of things like body fat, health, known susceptibility to DCS all should be considered to give a more worthwhile statistics. An example would be; if people with a BMI of X vs Y have a 75% chance of DCS and those same people if subjected to using Nx then see a fall of DCS to 20% clearly Nx is worth it for those people.

    And I would make the point again, I did similar profiles as her as well as dived every day without Nx and sometimes more aggressively and yet I was not affected at all. Clearly I am affected differently, the risk is there but much much less. Why? because we are individuals.
     
    gopbroek and tracydr like this.
  8. Christi

    Christi PADI MSDT/Dive op owner ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
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    This is actually pretty text book! And so many people dismiss the "skin bends" the fact is that skin bends often become more serious in nature with neurological symptoms presenting hours or even days later!
     
  9. Peter69_56

    Peter69_56 Divemaster

    # of Dives: 500 - 999
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    I agree totally, the mind says this isn't happening to me, so denial kicks in. As much as I wanted it to go away, I wanted to face reality. It was the size of 2 thumb nails but clearly a skin bend. No reason for it.

    The next time it was a small rash under her breast area, once again no pain and easily deniable. The last time there was severe pain and clearly a skin bend and more.

    The sad part was that in accepting it had happened the medical system let us down. Saw a doctor who should have referred us to the Navy dive centre but wouldn't and also would not put her on O2. No argument I ran would get him to authorise the access. Very frustrating in a country you don't live in or understand all the customs.
     
    Christi likes this.
  10. Christi

    Christi PADI MSDT/Dive op owner ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: Cozumel, MX
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    As I mentioned in an earlier post - we had a very interesting presentation/open house at the Hyperbaric Chamber here last week (actually every Tuesday and Thursday in July). As much as I thought I knew about DCS (having suffered two "undeserved" Type II hits in the past 10 years) - I learned a lot and refreshed myself on several things. "Skin bends" was discussed at length and I will never ever take them lightly in anyone again! My last hit started as what I thought were "just the skin beds" - 8 - 9 hours later I was suffering full blown severe neurological symptoms. I now understand that my symptoms and the onset of the symptoms was classic! And yes, denial is the first symptom! :)

    I encourage anyone on the island through next week to attend the chamber open house - Tuesday and Thursday evenings at 7pm - no charge and all are welcome. The presentation is in English with enough interest, so I am trying to organize an English presentation for Tuesday evening! Calle 5 1/2 block off the waterfront!

    EDIT: Just got confirmation that this Thursday will also be an English presentation! So if you are on the island please join us! I will be attending AGAIN!
     
    Last edited: Jul 23, 2013
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