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Thread: Involuntary Nasal Breathing & CO2?

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    Question Involuntary Nasal Breathing & CO2?

    So i've been told by several different well respected people in the rebreather community, in the past, that creeping hypercapnia will cause a person to involuntarily breath through their nasal airway and not realize it.

    The reason this matters is that we need to block our nose during pre-breath to prevent adding fresh air to the loop via this involuntary action; preventing us from ever finding out there is a CO2 issue until we are in the water.

    Does anyone happen to have any medical studies/ journal papers/ etc that show this?

    Thanks!

    -Tom
    Last edited by tmccar1; 24th December 2013 at 20:39. Reason: Grammar

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    Re: Involuntary Nasal Breathing & CO2?

    I have never heard of that myself and during diving there are a number of scenarios where there is mask gas exchange (for me, funky pressure dynamics with too much gas in the loop). It would be difficult to tell the difference between a pressure imbalance and involuntary nose breathing. Just another reason to use RMS or CO2 sensor.
    Last edited by DwayneJ; 24th December 2013 at 20:32.

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    Re: Involuntary Nasal Breathing & CO2?

    It's been a very accurate indicator of impending CO2 issues in my case. It took me awhile to figure it out, but the sensation of the mask getting sucked onto my face means trouble. I recreated it while snorkeling as well. It's a distinct and uncomfortable feeling.

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    Re: Involuntary Nasal Breathing & CO2?

    Quote Originally Posted by hound  View Original Post
    It's been a very accurate indicator of impending CO2 issues in my case. It took me awhile to figure it out, but the sensation of the mask getting sucked onto my face means trouble. I recreated it while snorkeling as well. It's a distinct and uncomfortable feeling.
    What you describe matches exactly what I have experienced but for me, it was just loop imbalance.

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    Re: Involuntary Nasal Breathing & CO2?

    I thought the same thing but with the lungs nicely inflated it simply wasn't possible. There was also no sensation in my mouth. The first few times I flushed enough and stopped moving for a bit, inadvertently warding off the retention from blowing up in my face. The day I ignored that sensation was the day I almost killed myself, allowing a nasty CO2 attack to set it hooks into me. Looking forward to any study someone digs up.

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    Re: Involuntary Nasal Breathing & CO2?

    Quote Originally Posted by DwayneJ  View Original Post
    I have never heard of that myself and during diving there are a number of scenarios where there is mask gas exchange (for me, funky pressure dynamics with too much gas in the loop). It would be difficult to tell the difference between a pressure imbalance and involuntary nose breathing. Just another reason to use RMS or CO2 sensor.
    RMS and CO2 sensors are nice tools, but not the end-all be-all. What if CO2 buildup were caused by a failed mushroom valve?

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