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Thread: Carbon Dioxide Problems

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    Carbon Dioxide Problems

    Hallo

    Iíve some questions about CO2 issues on rebreathers. Iím a newbie so please bear with me.

    On open circuit, if youíre working harder than you should and youíre out of breath, then youíre going to stop, relax, gain control of breathing and once everything is back to normal probably carry on with the dive.


    If things are worse, and maybe you have a bit of a headache, the sensible thing might be to just call it. But some people might carry on after a rest if the headache went away.

    If you have a massive headache, then obviously you are out of there, not much argument with that.

    As a RB newbie Iím trying to understand if there are similar degrees of response, or if the general feeling is that there is so much more risk associated with CO2 that now you would call it every time. Ie where do people draw the line on CO2 symptoms and thumb it.

    Thanks


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    Re: Carbon Dioxide Problems

    With a rbr it can be more insidious than "over-breathing" a reg. If the scrubber is exhausted, you may not be exerting a lot of effort, so resting to catch your breath won't help. The onset may be so slow that you may not notice an increase of breathing rate until your dissolved PCO2 is near critical and it then takes a very little to flip you over the edge. Just changing to OC can be a very very big challenge. That is why some think a BOV is mandatory equipment.

    Dale

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    Re: Carbon Dioxide Problems

    Quote Originally Posted by single tank numpty  View Original Post
    Hallo

    Iíve some questions about CO2 issues on rebreathers. Iím a newbie so please bear with me.

    On open circuit, if youíre working harder than you should and youíre out of breath, then youíre going to stop, relax, gain control of breathing and once everything is back to normal probably carry on with the dive.


    If things are worse, and maybe you have a bit of a headache, the sensible thing might be to just call it. But some people might carry on after a rest if the headache went away.

    If you have a massive headache, then obviously you are out of there, not much argument with that.

    As a Rebreather newbie Iím trying to understand if there are similar degrees of response, or if the general feeling is that there is so much more risk associated with CO2 that now you would call it every time. Ie where do people draw the line on CO2 symptoms and thumb it.

    Thanks

    CO2 hit is a big problem, however no point to go immediate panic mode.
    With elevated level of CO2 you more likely will start to feel short of breath before headache. If you were working hard than you stop or slow down, vent the loop with fresh dil (or take few sanitary breaths from OC), relax and regain control on your breathing. Carefully monitoring your feelings continue the dive. If symptoms repeat than immediately bail out and call the dive.

    Proper rebreather preparation before the dive, careful scrubber packing, using recommended CO2 absorbent and duration time will help to avoid accidental CO2 hit. Carbon Dioxide brake through as a result of diver s hard work is manageable.



    Dive safe,
    Nick

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    Re: Carbon Dioxide Problems

    Quote Originally Posted by single tank numpty  View Original Post
    As a Rebreather newbie Iím trying to understand if there are similar degrees of response, or if the general feeling is that there is so much more risk associated with CO2 that now you would call it every time. Ie where do people draw the line on CO2 symptoms and thumb it.
    Not meant to scare you, but CO2 is a real danger on CCR.

    Read up on some of the recent threads in the Accident-forum.

    Eventhough I've posted it before, it is the one list of CO2-hit symptoms that I use. It was originally posted by AD_Ward9, so credit goes to him:

    http://www.rebreatherworld.com/showthread.php?t=20066

    Read the whole thread.

    Regards
    Nicolai

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    Re: Carbon Dioxide Problems

    Quote Originally Posted by Hanssing  View Original Post
    It was originally posted by AD_Ward9, so credit goes to him:

    http://www.rebreatherworld.com/showthread.php?t=20066
    Thanks Nicolai, I already have the whole thrad in my reading library, with your post highlighted :D. I've done the reading on the board.

    What I want is an answer to my question please. ie do you assess things and make a decision as I would do on OC, or do you have much less tolerance because you are CCR.

    THanks

    Mike

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    Re: Carbon Dioxide Problems

    Mike,

    IMO, diving a Rebreather carries more risk than OC in the sense of issues creeping up on you faster and sometimes with little or no warning. CO2 hits are relatively rare in OC. I would say that because you have less time to react, and other actions are necessary (Getting off the loop, when it may be impossible to do without a BOV) that yes you have less tolerance.

    CO2 in particular has been discussed as the main area that, at present, can get you before you realize it's happened.

    We all think we can recognize and or prevent these problems from happening, until they do, at which point we, at times, unfortunately loose someone.

    If you don't acknowledge that risk from the beginning, then stay on OC.

    Richie
    Last edited by diverreb; 24th July 2008 at 15:11.

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    Re: Carbon Dioxide Problems

    Quote Originally Posted by single tank numpty  View Original Post
    What I want is an answer to my question please. ie do you assess things and make a decision as I would do on OC, or do you have much less tolerance because you are CCR.
    Definetly less, on paper....
    TheCCR has some tricky ways of putting your lights out, so if something does not feel right, get off the loop (sanity-breaths) and figure it out.

    I've had three times, where I afterwards kicked my self for not just bailing out, to be on the sure side:
    1+2) I sometimes get vertigo when ascending even just a few meters due to innner-ears not equalising together. It goes away quickly, and I've been monitoring the PPO each time, but it could have been frozen displays or whatnot. Better safe than sorry.

    3) I had one dive where I was *not* in the zone. Didnt feel confident and completely in controll, lost a cell completely, and had bouyancy all over the place. It was a shallow wreck (25msw), and I did do frequent Dil-flush to check PPO. I have a small suspicion that I had a very minor hit due to the rEvo being hammered while standing up in a hard alu-rib for 1Ĺ hours. I just did the dive for an hour, and wrote it off as beginner-nerves (solo, less than 15hrs on a CCR, defect cell, rushed entry), but in retro spect perhaps the sorb had settled in both cannisters? The serial rEvo scrubber-design saved my bacon - or it really was just nerves. Anyway suffice to say I should have binned the dive. I actually did almost every thing you not supposed to do on that one But I was very alert..... Suffice to say I'm not proud of that one, and consider it user-error.
    BTW: It was not until I later read AD_Wards list that I drew the conclusion about a stage-1 hit.

    ---

    Now the question that you're really asking - have I bailed in anger, even just to be safe?
    Cant say I have, never had the need to - I'll argue that you should have less tolerance, and not just slow down as on OC, but I have not needed to yet. I've been a bit winded while dragging a long chain and weight around a wreck in zero-viz trying to tie in before the boat ties into the shotline. But I was aware of it, and just restet until breathing was normal, and continued.

    Apparently I hsould do as I say, and not as I do

    Nicolai

  8. #8
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    Re: Carbon Dioxide Problems

    Quote Originally Posted by single tank numpty  View Original Post
    Hallo
    As a Rebreather newbie I’m trying to understand if there are similar degrees of response, or if the general feeling is that there is so much more risk associated with CO2 that now you would call it every time. Ie where do people draw the line on CO2 symptoms and thumb it.

    Thanks
    Hello,

    There are quite a few threads discussing CO2 because it is such a critical issue.

    There is a major difference in degrees of response in OC overwork and over breathing a rebreather. On rebreathers the resulting CO2 hit impairs your ability to reason and a strong indication that your life support unit is failing to do what is required to support life . On the rebreatheres, in a critical situation where you need to think most clearly, your very thought process becomes suspect. That is the reason most instructors teach you switch to OC first -- to clear your mind.

    There are really three overall approachs: Bailout and get-out, bailout/flush and contine on the loop, and use OC in heavy excertion to avoid the problem to begin with. Which is used is an interesting analysis in a diver's approach to risk management, forethought, and diving strategy.

    I was taught to bailout and get out on any CO2 hit. I think that is the safest approach for any CO2 hit. This is particularly important, IMHO, as the ability to reason the cause of the failure is in question... not to mention that you can't absolutely KNOW what caused it.

    Many here would argue that they will work to continue the dive on the loop. They can reasonably deduce that the CO2 hit was from overbreathing and will bailout, troublshoot, fix (reduce workload, flush), and return to the loop... or flush, troubleshoot, fix, and stay on the loop.

    Others might avoid the issue and switch to OC when they begin to excert heavily and then return on the loop after things settle down. They'll continue the dive if they still retain enough bailout reserves. This the thinking diver's solution -- avoid the risk upfront.

    Sincerely,

    -p







    Thumbing the dive is a more difficult decision. First you are going to bailout to OC to get your head straight.
    Last edited by PaulTG2; 24th July 2008 at 20:16.
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    Re: Carbon Dioxide Problems

    Numpty - when in doubt bailout - you can then make a sensible decision.


    See you in a few days

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    Re: Carbon Dioxide Problems

    Check the Rebreather World Library. You will find this discussed in my article, "Carbon Dioxide and the Rebreather Diver."

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