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Thread: O2 convulsion

  1. #31
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    Thanks everyone for the info and thoughts!

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  2. #32
    Quote Originally Posted by saturation

    PN2 provides some protection against 02 convulsions. When this is replaced by He, the risk for oxtox increases. The risk in increasing order is ~ air > nitrox > trimix > heliox.

    Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup).
    Any references to studies or experiments which indicate the positive pN2 impact on oxtox ?

    Many Thanks
    Peter

  3. #33
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    Quote Originally Posted by smekke
    Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup).
    Any references to studies or experiments which indicate the positive pN2 impact on oxtox ?

    Many Thanks
    Peter
    What saturation is talkng about is studies and dives that have been acomplished on very high pn2 loads.

    N2 has the effect of slowing down the nervous system (retarding xmission fro the neurons), which is probably why this effect has been seen... while He allows the neuorons in the brain to communicate more easily...

    This also is probably the reason why someone switching to an oxygen rich deco mix, is much more likely to tox than someone diving air very deep...
    There have been air dives to over 450fsw with little problems other than SEVERE narcosis, but someone swicthing to oxygen at 60fsw is much more likely to tox at the same oxygen exposure..

    A helox based deco mix will also have ahigher risk of toxing than a nitrox deco mix..
    More helium isnt always better.. I have also discussed this matter many times with an HSE hyberaric chabmer trainer, and he told me that the incidence of tox effects is definately higher when they use heliox 50 for their schedules over the same exposures with oxygen only.
    Joe Radomski
    CCR Trimix Instructor Trainer
    ANDI Instructor Trainer Director #10

    All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.

  4. #34
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    Quote Originally Posted by smekke
    Didn't know that. I assumed adding He is good because it's more easy to breath (better ventilation, less chance for CO2 buildup).
    Any references to studies or experiments which indicate the positive pN2 impact on oxtox ?

    Many Thanks
    Peter
    Concur full with jradomski summary.

    Here are some links as references:

    'Prolonged latency' implies some 'resistance' to initiating seizures.

    http://www.ncbi.nlm.nih.gov/entrez/q...063&query_hl=3

    'Kindling' is an experimental attempt to 'mimic' seizures.

    http://thedecostop.com/forums/showpo...3&postcount=54


    http://www.scubaboard.com/showpost.p...2&postcount=18

  5. #35
    New Member Flying K is an unknown quantity at this point Flying K's Avatar
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    Re: O2 convulsion

    I am glad you are alive and well. I think the O2 hit was related to CO2.

    Thanks for posting your expeience

    Kenny Schneider

  6. #36
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    Re: O2 convulsion

    Perhaps it's so obvious and that's why nobody has asked, but what was the condition of the sofnolime, time elapsed on it pre-dive and total time on it to the time of the incident?

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    Re: O2 convulsion

    Your dive buddy rocks! And he is an OC weenie to boot! Pretty impressive how he knew exactly what to do and kept his cool....

  8. #38
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    Re: O2 convulsion

    Quote Originally Posted by Nick uk.
    Perhaps it's so obvious and that's why nobody has asked, but what was the condition of the sofnolime, time elapsed on it pre-dive and total time on it to the time of the incident?
    The lime was fresh for the dive and RT at the time of the accident was 75mins. I think it is unlikely that CO2 had anything to do with the seizure.

    JH

  9. #39
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    Re: O2 convulsion

    Quote Originally Posted by jhaaja  View Original Post
    Here comes a clarification about the calibration that I did before the dive. I use 99,5% pure oxygen and when I calibrated I input to the handset that O2 percentage is 98%. Hope this clears this issue.

    Thanks for the palpations explanation. Now I am even more sure that it was diaphgram contractions, because I can remember those quick inhale spikes during the contraction.
    That's the right way to calibrate Inpiration reb, as 98% is referred non to the tank's FO2 but the FO2 into the head after flushin' with oxygen.
    Apart the little differenc anyway.
    It may be interestin to understand more about scopolamine, as I've heard that saturation divers can't use else that a bit aspirine!
    Anyway Hyperoxia has very variable limits: when I was younger in '70 years, dove often with oxygen rebreathers deeper than 40' and did have no problems, also if the workload was at lower levels, it was a lot dangerous anyway!
    Just once I was workin' in the shallow waters of an harbour did see some flashes, I surfaced "as a rocket" with no conseguences.
    Now I'm terrible afraid about I did at that time and we must remenber that the lot of parameters involved to lead into cns convulsion cannot give absolutely safe limits.
    Fabio Bartolucci
    Last edited by Barfab; 20th September 2006 at 22:44.

  10. #40
    New Member B N Coleman is an unknown quantity at this point B N Coleman's Avatar
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    Re: O2 convulsion

    Hi guys I have been doing deep CCR dives on the YBOD, and decided some time ago, following some long stories, to reduce the PPo2 down to 1.1 for any dive deeper then 60msw and longer then 15min. Plus I have buddies take NO seasickness tablets/patches as tests show these do have an effect, although they can not be specific, with high O2 over prolonged exposure. So far So Good todate !

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