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RMV Spinoff from Accident & Incident Discussion - Northernone - aka Cameron Donaldson

Discussion in 'Marine Science and Physiology' started by johndiver999, Mar 20, 2019.

  1. Joneill

    Joneill Loggerhead Turtle

    # of Dives: 100 - 199
    Location: New Jersey, USA
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  2. BRT

    BRT Giant Squid

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    So long as that "pause" isn't "skip breathing" then I don't know anybody that "skip breathes". I used to take that pause to the the point that I would have a headache after the dive.
     
    Dan likes this.
  3. dmaziuk

    dmaziuk Orca

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    Presumably holding the pause by just the chest muscles and diaphragm, without closing off the airway -- just to be on the safe side?
     
    rsingler likes this.
  4. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
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    Exactly. It's an inspiratory pause, not a breath hold.
    Any headaches that might result are clearly CO2-related, and have crossed the line into skip breathing. Just not helpful to RMV, and risky as discussed above.
     
  5. Joneill

    Joneill Loggerhead Turtle

    # of Dives: 100 - 199
    Location: New Jersey, USA
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    That is certainly one reason dogs may pant - but not the only one...
     
  6. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

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    ..and where is the line? How long before a pause at the end of a breath turns into skip breathing?

    The people I know who skip breathe and will talk about it ("Hell, yes! I skip breathe!" one said) maintain that they know where that line is. They are well aware of the danger of CO2 buildup, and they are sure they can avoid going too far.
     
    markmud and rsingler like this.
  7. cerich

    cerich ScubaBoard Supporter ScubaBoard Supporter

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    before I have to learn a new term for what to me is intellectually dishonest, it's easier to state what I think and call it a day.
     
  8. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
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    An excellent question, John!
    You can't feel it anymore, after you become a chronic CO2 retainer. We can see a guy with emphysema from across the street, pursing his lips and forcing out his breath against back pressure to maintain gas exchange with his smoke-damaged lungs. But he can't feel his pCO2 of 55 any more, because his body has elevated bicarbonate to keep his pH normal.
    But a diver? My prejudice is that no matter how they pride themselves on their low RMV (and they should), they are also ignoring the subtle things that they just associate with diving, which are actually forced CO2 retention. A minor headache, the occasional big breaths back on land that they don't even notice any longer. They are the opposite of the relaxed Zen diver. They have developed a habit which they associate with their low RMV which is actually counterproductive, but they do not understand the physiology and have carried their altered pattern too far.
    But they are not chronic CO2 retainers. You can't voluntarily do that all the time. Your body will correct, absent a disease process that produces more CO2 or impairs ventilation. So they have habituated themselves to feelings which they ignore, or which no longer are as severe (headaches) as the body acclimatizes. But they are at significantly increased risk, for ten minutes extra dive time.

    I would say, listen to your body. Relax. Don't chase RMV. But perhaps just watch for wasted small breaths as you dive. Understand that your desire to "sip" just a little air from your tank actually made things worse, because you mostly exchanged dead space, and you'll be feeling the need to take a big breath soon when your body sees the rising CO2. Ignore that at your risk.
    Then be happily surprised as your RMV improves naturally, with experience and calm.
     
  9. BRT

    BRT Giant Squid

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    We dove for years with a dive shop owner in Mexico who didn't seem to use any air. We wanted so badly to extend our dives and we learned to wait between breaths, call it what you want. I often waited long enough between breaths to have a good headache at the end of a dive. Now, a friend who often dives with us is really frustrated because he uses more air than us. He hangs above and watches. He says " all you guys that don't use much air are skip breathing, I can see it!" Naw, we are just waiting between breaths. Now I have to watch myself because I automatically "wait between breaths" and have to make sure I stop doing that while exercising. This February in Mexico I got a short tank. I didn't want a short dive so I "waited a little more between breaths" until my tank pressure was in line with my dive time. It works, very simply because each breath has less oxygen and more CO2 when exhaled. Pushed too far a person can get really narced and or a headache.
     
  10. BRT

    BRT Giant Squid

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    Full disclosure, I close off the airway....I also know when I am going up or down.
     
    lermontov likes this.

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