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Thread: Are Rebreathers Safer for DCI prone divers than OC

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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Unfortunately, due to a lot of factors, denial is practically one of the symptoms. It is certainly part and parcel of the experience in most cases.

  2. #32
    New Member Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell has a reputation beyond repute Simon Mitchell's Avatar
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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Hello,

    Great thread and interesting discussion. A few issues have been raised that I would like to comment on.

    First, Mike was right to question whether Cameron's events were due to decompression sickness or not. Having read Cameron's more detailed descriptions, I am inclined to believe that they were. The deep seated severe pain described is typical. Moreover, if Mike Bennett thought it was, then that's good enough for me.

    Second, accepting that these events were due to DCS, I also agree with those who have questioned whether their occurrence justifies a tag of "bends prone". This is a difficult one. I doubt if we would designate Cameron an accident prone driver if he had two minor fender benders in a couple of weeks on a background of a long period of otherwise safe driving. This is largely because in the context of driving we all intuitively understand the concepts of statistical risk and bad luck . However, we struggle to think in the same way about DCS in diving even though there are many similarities. I have no answer to this. Over a career of some 6000 dives I personally have suffered two minor pain only events in relation to decompression dives during which nothing went wrong. I certainly don't consider myself bends prone, and I would not consider for one picosecond having a transoesophageal echo probe rammed down my gullet (I'll return to this in a sec). The only possible conclusions that we can draw here are diametrically opposed. One is that this could all be a statistical aberration, and that Cameron has no predisposition (except to bad luck). The other is that there is some unidentified risk factor.

    Third, the issue of PFO (Oh God... not again). I'll keep this brief. Heather raised an important point in suggesting that the second event seemed more than just "pain-only". From your story, it seems that you had arm weakness, although severe multifocal pain in DCS can cause reluctance to move that the patient might interpret as weakness. This is an important distinction because I would not refer a patient for PFO testing after two episodes of "unexpected" pain-only DCS. DCS causing only musculoskeletal pain has not been causatively linked to PFO. But perform an echo and you have a roughly 25% chance of finding one (because about that proportion of the general population have one)... and then what are you going to do??!! You've found a lesion that has no causative link to the condition you suffered, and the only thing you can do about it is ignore it (in which case why subject yourself to the test?), give up diving (yeah right), or undergo a repair procedure that is expensive, carries significant risks, and may have no benefit. Having said all that, I WOULD refer a diver for PFO testing if they suffered "unexpected" spinal or cerebral DCS. If your arm was truly weak on objective testing, then the test is probably justified (I would be interested in Mike Bennetts opinion of your arm). So, if the arm was weak, by all means investigate it fully. If it wasn't then I wouldn't.

    Finally, on the issue of buying a rebreather to improve your safety. As a mad keen passionate rebreather diver it pains me to say it, but I think JP Jones made a very good point which I would illustrate with this analogy: buying a rebreather to improve your diving safety is a bit like buying a rabid Rottweiller to scare off other dogs that might bite you. The other posters have made all the relevant points. Rebreather diving certainly provides you with opportunities to reduce your decompression stress relatively easily. Whether this translates into a reduced incidence of decompression events will depend entirely on how you manage those opportunities, and to what extent you allow yourself to be seduced the the rebreather's greater depth and duration capabilities. Moreover, as alluded to in my dog analogy, I seriously doubt that owning a rebreather improves the overall safety of your diving when all possible adverse events are considered.

    Warm regards,

    Simon M
    Last edited by Simon Mitchell; 10th January 2006 at 06:37.

  3. #33
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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Thanks for the detailed responce Simon...

    As you can expect my mind is running around 100 miles a second, trying to learn all this YBOD stuff, get more info on DCI and PFM and WTF and PSM all seem to affect is (not my psm mind you..)

    But one question to your dog / breather issue.. alot of my diving already is limited by the bottom of the ocean floor, so depth is not an issue, but I guess the length of dives can go up.... I see if I go for a boat dive with a depth max of say 35m (sydney diving) I can only see it as being safer due to the increased o2... more time aside even if I did add 5-10 minutes to my dive due to the YBOD wouldnt I still be loading my body with less of the evils and off gass quicker when I do finally accent ?

    I can see where you are going if we are talking about 60-90m dives ,... but my typical dives are not those, and not the ones that I have had incidents in.

    Thanks for your input and please correct, guide and as I am a bit thick and slow ;) ..

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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Quote Originally Posted by hchoat
    I would suggest to you that 2 minor "hits" in 500 plus dives for a very active diver is not unreasonable.
    Hi Heather, i do not agree at all...
    I have been diving for almost 19 years and i have had two hits and both of them last winter and close to each other, mainly because i was diving 7days a week, twise a day over a period of 4 months as a commercial diver. Both minor, type I, skin and joints bends.

    A very active diver may do almost 500 dives a year, that would leave him/her with an average of two hits a year.

    /Jonny

  5. #35
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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Quote Originally Posted by Def
    I do not consider myself a dangerous diver, or really push the limits, it comes down to the shear number of dives I do... is 1 in a 1000 an average, seeing most divers do not get close to this in there life time, should I feel 2 in 2000 just a bad average ?

    I understand RB's are just the reeper trying to get you, and I am happy to spend the time to learn to control, harness and dive with the reeper.... but its trying to kill me in different ways...

    I have dived with sharks, muppet divers, strong currents and cold water and I see them all as risks I look at before strapping on my tanks and jumping in..... I see a CCR just another one... but at least its one I can directly control ... not like these bubbles.
    If you want to learn and get a better way to dive then CCR is for you. But with the number of dives you make a year you still stand a good chance of taking a hit just due to the exposure. It's just one of the risks we take to enjoy our sport. I had both of my hits in the first 2000 dives now I have gone for over 2000 without one. Mine were caused by too tight of wrist seals on a new dry suit and the second time by too much exercise right after the dive. So the only suggestion I can make is if you get hit try to go over what you did that day that might have left you open to more risk.

    Have fun learning your new skills and welcome to the silent world.

  6. #36
    Banned Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del is a name known to all Andy Del's Avatar
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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Quote Originally Posted by Def
    ...my easy dives are taken as serious as a deep one.. deco time be it 5 @ 5 is usually increased due to me filming students (not mine) or schools of fish at that depth, or just relaxing in the 3d enviroment...
    Cameron!
    This may be just continuing to , but have you considered what you are doing during your safety stop/deco? If you are moving a large, heavy (on land) video or still setup about, it may be that extra bit of work / exercise that it better not undertaken. While your photography gear is light underwater, it still has inertia to overcome.

    But, welcome to looking at the darkside! Are you still in Sydney?

    cheers

    Andy

  7. #37
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    Re: Are Rebreathers Safer for DCI prone divers than OC

    Gday Andy,

    Yeap back again based in Sydney at the moment, chasing the camera around the world though so here there and everywhere really!

    I was thinking about the whole holding the phenom at for 2-3 hours as a increasing risk, but I usually hold it in the right, and its only neg with the lights on it, but after the Hit, I started stretching / moving more on deco, and tieing off the camera or using a lenyard more.... but a good point.

    I think with the lights its 2-4pd neg, so definatly a stress over 2-3 hours!

    So when are we going to go diving Andy ?

    Cam,

    Quote Originally Posted by Andy Del
    This may be just continuing to , but have you considered what you are doing during your safety stop/deco? If you are moving a large, heavy (on land) video or still setup about, it may be that extra bit of work / exercise that it better not undertaken. While your photography gear is light underwater, it still has inertia to overcome.

    But, welcome to looking at the darkside! Are you still in Sydney?

    cheers

    Andy

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