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Thread: Two C02 hits - time to get fit?

  1. #41
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    Re: Two C02 hits - time to get fit?

    Quote Originally Posted by EBT  View Original Post

    Nowadays Im old and still remind myself to "let my breathing rate dictate my work rate, not the other way around".
    Love it! Simple and strong!


    Sent from my PAP4500DUO using Tapatalk 2

  2. #42
    RBW Member delta-v is an unknown quantity at this point delta-v's Avatar
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    Re: Two C02 hits - time to get fit?

    It's been several months since my original post. In that time I've completed MOD2 and executed many long and deep dives. Whenever conditions have been favourable - particularly at depth (i.e. the scrubber and gas density under significant ambient pressure load) - I have experimented with different breathing styles in an attempt to understand the problem better.


    PSotis and others whose replies ruled out over-loading the scrubber know what they're talking about after all. It's not that my intuitive reasoning was wrong, it's just that it takes a whole lot of gas flow to overwhelm the scrubber.


    Earlier I hypothesised that MLV (minimal loop volume) plus the fact that I hardly breathe underwater may be creating the conditions for CO2 build-up - not just in the loop, but also at the cellular level (thank you Larry0248 for that insight).


    This appears to be the case. I now avoid a strict MLV approach and keep the CLs partially inflated even on a deep inhale. This is not a bad idea anyway as it automatically helps if there's any condensate/water in the exhale CL.


    More importantly, I have set myself a minimum breathing rate regardless of whether I need it or not. It's a steady rhythm - not too deep because that's dangerous and can screw up BCY, but deep enough to cycle the lungs and CLs properly. Remembering to do it was tricky in the beginning but now it's fairly automated.


    I have carefully altered these dynamics (under the watchful eye of a competent buddy) to gently onset hypercapnia (it still takes about 10 minutes or so under mild effort) - which in my case is always indicated by a powerfully thudding heartbeat and a growing sense of unease. Never more than 10 seconds or so in this state - dyspnea at 8ATA is no fun. Restore the breathing rhythm and it all goes away - about a minute tops.


    As per the plan and as per replies here, I've added a bit of cardio to my week here and there. Haven't lost a ton of weight, but have shifted it around a bit - less fat, more muscle.


    Just wanted to post these observations here in case they help someone else who also has a low SAC rate/RMV and migrated to CC from deep OC. I'm lucky that my body gives me some hypercapnia warnings or at least 'something-isn't-right-here' warnings. They tell us many people don't get any warning at all.


    For me personally, at this stage, breathing like a robot is really working. And as a bonus, when I need to exert myself or fin a little harder, I'm starting in a clean, low CO2 state.

  3. #43
    RBW Member dreamdive has disabled reputation dreamdive's Avatar
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    Re: Two C02 hits - time to get fit?

    Quote Originally Posted by delta-v  View Original Post
    It's been several months since my original post. In that time I've completed MOD2 and executed many long and deep dives. Whenever conditions have been favourable - particularly at depth (i.e. the scrubber and gas density under significant ambient pressure load) - I have experimented with different breathing styles in an attempt to understand the problem better.


    PSotis and others whose replies ruled out over-loading the scrubber know what they're talking about after all. It's not that my intuitive reasoning was wrong, it's just that it takes a whole lot of gas flow to overwhelm the scrubber.


    Earlier I hypothesised that MLV (minimal loop volume) plus the fact that I hardly breathe underwater may be creating the conditions for CO2 build-up - not just in the loop, but also at the cellular level (thank you Larry0248 for that insight).


    This appears to be the case. I now avoid a strict MLV approach and keep the CLs partially inflated even on a deep inhale. This is not a bad idea anyway as it automatically helps if there's any condensate/water in the exhale CL.


    More importantly, I have set myself a minimum breathing rate regardless of whether I need it or not. It's a steady rhythm - not too deep because that's dangerous and can screw up BCY, but deep enough to cycle the lungs and CLs properly. Remembering to do it was tricky in the beginning but now it's fairly automated.


    I have carefully altered these dynamics (under the watchful eye of a competent buddy) to gently onset hypercapnia (it still takes about 10 minutes or so under mild effort) - which in my case is always indicated by a powerfully thudding heartbeat and a growing sense of unease. Never more than 10 seconds or so in this state - dyspnea at 8ATA is no fun. Restore the breathing rhythm and it all goes away - about a minute tops.


    As per the plan and as per replies here, I've added a bit of cardio to my week here and there. Haven't lost a ton of weight, but have shifted it around a bit - less fat, more muscle.


    Just wanted to post these observations here in case they help someone else who also has a low SAC rate/RMV and migrated to CC from deep OC. I'm lucky that my body gives me some hypercapnia warnings or at least 'something-isn't-right-here' warnings. They tell us many people don't get any warning at all.


    For me personally, at this stage, breathing like a robot is really working. And as a bonus, when I need to exert myself or fin a little harder, I'm starting in a clean, low CO2 state.
    Hey Delta-V, thanks for sharing your progress!

    "I'm lucky that my body gives me some hypercapnia warnings or at least 'something-isn't-right-here' warnings. They tell us many people don't get any warning at all.
    That is true, either people pay attention to it very/too late or they don't have any symptoms.

    The notion of "overbreathing" a scrubber is so prevalent that people forget to ask themselves why they get a CO2 hit on OC! Increased work-loads, depth/gas densities are something to be watched. Since, at a certain point, breathing in it-of-itself will become too much work and a generator of CO2 that cannot be handled by the body (not the scrubber).

    Thank you for your original post and safe diving.

    Claudia Roussos MD

  4. #44
    RBW Member Mr.Dave is an unknown quantity at this point Mr.Dave's Avatar
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    Re: Two C02 hits - time to get fit?

    Second dive i ever did on my Meg while under instruction at 6m and being task loaded hard I found myself shallow breathing with MLV and the onset of an uncomfortably high breathing rate. I felt what I assumed to be C02 / hyperventilation and so increased the lung volume (TOS lungs), after a minute or two my breathing returned to normal and I learned a lesson... sod MLV!

  5. #45
    RBW Member rjack will become famous soon enough rjack will become famous soon enough rjack will become famous soon enough rjack's Avatar
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    Re: Two C02 hits - time to get fit?

    Good thread. Glad to see you are getting your issues sorted out.

    The only thing I would add is more than 15% helium for a 50m CCR dive. A lot more. Helium is so cheap on CCR that I would use a dil with 35 to 55% helium (depending on what I had at the time) for a 50m dive in strong currents. 35% would be a minimum though.

  6. #46
    RBW Member delta-v is an unknown quantity at this point delta-v's Avatar
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    Re: Two C02 hits - time to get fit?

    Quote Originally Posted by rjack  View Original Post
    Good thread. Glad to see you are getting your issues sorted out.

    The only thing I would add is more than 15% helium for a 50m CCR dive. A lot more. Helium is so cheap on CCR that I would use a dil with 35 to 55% helium (depending on what I had at the time) for a 50m dive in strong currents. 35% would be a minimum though.


    Sorry, but why bring helium into this discussion when it has no bearing on hypercapnia other than a tangential impact on gas density... or have I missed something?

    In my group we never dive an END (both gases narcotic) greater than 30m on a CCR, reducing to 24m beyond 70msw - but that's for narcosis management, not hypercapnia avoidance. Bailout mixes are planned accordingly - while keeping a wary and distrustful eye on our old nemesis ICD.
    Last edited by delta-v; 4th June 2015 at 08:57.

  7. #47
    RBW Member dreamdive has disabled reputation dreamdive's Avatar
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    Re: Two C02 hits - time to get fit?

    Actually Helium does have bearing on CO2 avoidance. When considering that we might encounter higher work-loads at depth, we increase our Helium concentration to decrease work of breathing.

  8. #48
    RBW Member Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P's Avatar
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    Re: Two C02 hits - time to get fit?

    Thanks for excelent thread.

    Thanks Claudia and OP that put some very valuable info and hints for avoiding/preventing CO2 buildup.

    - breath normal deep breaths with normal breathing rate,
    - dont skip breath (lower breathing rate under normal)
    - helium is your friend on CCR too (even more than OC)
    - have some cardiovascular workout
    - do not exagerate in MLV, but keep it usable non restricting,
    - listen to your body

    Igor P

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