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Thread: O2 convulsion

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    JJ-CCR, Inspo Classic

    HH Inspo

    Quote Originally Posted by Sutty
    Hi, Glad it worked out OK - good advert for having a (competent) buddy.
    A few thoughts, you mentioned your symptom of diaphragm contractions - what did it feel like exactly, did it interfere with your breathing? If this wasn't diaphragm contraction but palpitations (can feel like fairly dramatic thuds in the chest too) then it could have been an abnormal heart rhythm, which could possibly be caused by the aerius (listed as a side effect), and may be made more likely by the scopolamine (also increases heart rate). The seizure would then be secondary to a lack of blood to the brain - we see this occasionally in hospital, when people lose their cardiac output they can have a secondary seizure.
    I am quite sure that it was diaphgram contractions. When the contraction came I could feel it in my breathing. Can you explain more what you mean here by palpations? I did not notice any abnormalities in my heart rhythm. Thanks for the ideas.

    Someone asked earlier what my cells were. All four are AP originals.

    JH
    Finland

  2. #22
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    Palpitations are defined as an "abnormal awareness of heartbeat", if you have pauses in heart rhythm, extra beats, or abnormal rhythms you can get a thumping, squirming, or fluttering feeling in your chest. It can feel quite dramatic and can be associated with feeling short of breath. An involuntary diaphragm contraction would produce a sharp breath in, superimposed on your normal breathing ( a hiccup is a brief diaphragm contraction).

    Hope that helps!

    Neil

  3. #23
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    Quote Originally Posted by Drmike
    Er nope, you are telling your controller that 100% is in fact only 98%.

    So it would in fact give you extra O2.
    He calibrated with 98% O2, saying that it is 100% O2 correct?
    So when his loop was 98% O2 at 1 ATA, the controller thinks the loop is at 100% O2. You inspire 98% O2 and the controller thinks you inspired 100% O2, giving you less O2.

    Regardless it is most likely an insignificant difference.
    1.568 PPO2 would read as 1.6 PPO2

  4. #24
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    Quote Originally Posted by E-man
    He calibrated with 98% O2, saying that it is 100% O2 correct?
    So when his loop was 98% O2 at 1 ATA, the controller thinks the loop is at 100% O2. You inspire 98% O2 and the controller thinks you inspired 100% O2, giving you less O2.

    Regardless it is most likely an insignificant difference.
    1.568 PPO2 would read as 1.6 PPO2
    Ah yes that would be true if thats what he did.

    I understood from his post that he entered 98% into his handset when he set calibration gas % (I used to enter 99% on my inspiration) but in fact flushed with 100%.

    Buy you would be correct of course if he was actually using an O2 source of 98%.

    I agree the difference is small but that combined with say a bad flush, changes in atmospheric pressure, etc can all add up.

    Cheers
    Mike

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    HH Inspo

    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.

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    I wonder if the fact that you couldn't go 10 mins in the chamber without toxing suggests more than anything else that maybe you are just one of those guys who are more susceptible to toxing? Did the hyperbaric docs suggest a reason - or is that regarded as normal during recompression treatment?

    You reported that you didn't have water in your lungs - yet you weren't breathing. I thought toxing doesn't stop one from breathing? My understanding was after the spasm ends the diver would begin breathing again? Perhaps some of the MDs here can advise.

    If you are unfortunate enough to be susceptible perhaps one of those KM48 masks like I use might be a good idea for you, at least it protects your airway from water in the event of a tox. (personally I really don't understand why these pod masks aren't standard issue for all divers)

    This is quite a story. Thanks again for sharing it.

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    I have been doing those 40-60m mix dives for 2,5 years now. First on OC and now on CCR. I have never earlier had any problems with quite high CNS% loads. I think something just made me more prone to toxing on that particular dive. I think the only explanation is that the previous days near 100% CNS did not count-down as it normally does (90mins halftime).

    The chamber doc was more or less out from the situation. I think I knew better and my dive partner also. They were really surprised when I jerked the mask off from my face the first time in the chamber. They asked what I am doing and I just stated that I don`t want to convulse alone here in the chamber, I am taking a break. The first onset in the chamber almoust got to the point that I would have lost consiousness, I could stop it by hyperventilating the chamber air and the diaphgram contractions stopped. The doc was really surprised. I have heard that convulsions in chamber treatment are really rare.

    I was lucky that I did not start to breathe on my own. That prevented me from drowning. I guess normally breathing reflex starts after the convulsion, but in my case it did not do that. My breathing started with mouth-to-mouth.

    I have also been thinking of getting a full face mask. Anyway you are not able to give your mouthpiece to your dive partner. Of course I need a good CC/OC switch also.

    JH
    Finland

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    Quote Originally Posted by jhaaja
    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.
    Ok, so DrMike was correct you were inspiring MORE O2 than your handset thought....
    1.6 PPO2 = 1.625 PPO2

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    Quote Originally Posted by Drmike
    I wonder if the fact that you couldn't go 10 mins in the chamber without toxing suggests more than anything else that maybe you are just one of those guys who are more susceptible to toxing? Did the hyperbaric docs suggest a reason - or is that regarded as normal during recompression treatment?

    You reported that you didn't have water in your lungs - yet you weren't breathing. I thought toxing doesn't stop one from breathing? My understanding was after the spasm ends the diver would begin breathing again? Perhaps some of the MDs here can advise.

    If you are unfortunate enough to be susceptible perhaps one of those KM48 masks like I use might be a good idea for you, at least it protects your airway from water in the event of a tox. (personally I really don't understand why these pod masks aren't standard issue for all divers)
    In my short diving career, I have met more and more people who claim that they are susceptible to toxing. Most times, I thought these folks were either being extemely paranoid, or were too thick-headed to believe that nitrox was superior, or didn't want to change their habits, or pay extra for something other than air....don't you love run-on sentances? I know a cave diver who still only dives air, and decos on air! I still think that may be a little extreme, but after reading this and thinking more about the topic, I'll change my point of view of these people who I used to think were just weirdos. So, if I was forced to bet money on the topic I would say you are just one of those guys more susceptible to toxing. The little things do add up, and do so quickly. Let us also remember susceptibility to toxing is different, depending on what day of the week it is (insert your preferred factor(s) here). For some reason, these last two sentances make me think about the diver saying he had an uneasy feeling throughout the dive due to poor vis....I hate uneasiness (and I'm especially screwed, because after reading an article about type D personalities in Newsweek, I'm convinced I am one of them). Thanks for sharing.

    And for the record, I wanted to post just so I could have a reason to post some of these cool spaceships

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    There are rare reports of tech diver 02 convulsions at P02 => 1.3. As far as the early 1990s, its been suggested that tech divers maintain <= 1.2, as no recorded convulsions have occurred here. Many studies with low P02 convulsions have occur on USN rebreathers trials rather than open circuit.

    http://64.233.161.104/search?q=cache...ient=firefox-a

    The above is a cached link as the original server is down at this time.

    Nevertheless, the rare but anecodatal reports of convulsions and the small difference in P02 have always led me to recommend planning not exceed p02 of 1.2, but strictly when on trimix.

    In addition, the risk of 02 convulsions appears [ no true controlled studies] higher:

    Among RB versus OC divers for the same P02
    trimix versus nitrox versus air for the same P02
    certain classes of divers

    In OC, the P02 is maximum only at the planned maximum bottom depth. For RB divers, it can be sustained throughout the dive. The changes in p02 with depth in OC simulates 'air' breaks depending on depth, and the variability in P02 seems to provide increase tolerance to 02 convulsions.

    The amount of c02 buildup that can trigger 02 convulsions is unknown, except that its a strong culprit in initiating convulsions and the dose can be very small. In dry chambers, convulsions are rare even during the peak exposures of 2.8. Ivan Montoya in Miami commented that when divers are told to remain absolutely still, no reading talking or any activity, during this phase, he has reduced dry chamber convulsions to near 0% [personal communication.]

    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.

    Without formal testing, its not possible to determine if a diver is oxtox prone, but USN trials suggests there were such folks. It was largely abandoned when studies suggested that tox was not dose related, as suggested by CNS clock, but more consistently related to the maximum p02 inhaled. Convulsions can occur anytime. The CNS% clock has little value.

    Although the risk of tox remains low at the PO2 1.3 level, the consequences of tox, as in this report, are very harsh.

    The above is not 'new' information and can be found in Bennett and Elliott's Physiology and Medicine of Diving. You can find further discussions linked to my pen name at The Deco Stop and Scubaboard.com.

    There are no known relationships between scopolamine and convulsions, when other factors [such as those mentioned here] are considered.

    Dive Safe.



    Quote Originally Posted by jhaaja
    I have been doing those 40-60m mix dives for 2,5 years now. First on OC and now on CCR. I have never earlier had any problems with quite high CNS% loads. I think something just made me more prone to toxing on that particular dive. I think the only explanation is that the previous days near 100% CNS did not count-down as it normally does (90mins halftime).

    The chamber doc was more or less out from the situation. I think I knew better and my dive partner also. They were really surprised when I jerked the mask off from my face the first time in the chamber. They asked what I am doing and I just stated that I don`t want to convulse alone here in the chamber, I am taking a break. The first onset in the chamber almoust got to the point that I would have lost consiousness, I could stop it by hyperventilating the chamber air and the diaphgram contractions stopped. The doc was really surprised. I have heard that convulsions in chamber treatment are really rare.

    I was lucky that I did not start to breathe on my own. That prevented me from drowning. I guess normally breathing reflex starts after the convulsion, but in my case it did not do that. My breathing started with mouth-to-mouth.

    I have also been thinking of getting a full face mask. Anyway you are not able to give your mouthpiece to your dive partner. Of course I need a good CC/OC switch also.

    JH
    Finland

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