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How long does it take to drown?

Discussion in 'Basic Scuba Discussions' started by CAPTAIN SINBAD, Jun 24, 2013.

  1. TSandM

    TSandM Missed and loved by many. Rest in Peace

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    It's a good question. You need about 16% O2 at the surface, or about 2.5 psi, to maintain consciousness. Once you stop exchanging gas, the oxygen content of the gas in your lungs will begin to drop -- but how fast it drops will depend on how cold you are and what you are doing. Obviously, trained free divers can spend several useful minutes underwater, just on the gas they took down from the surface in their lungs -- but part of how they do it is learning to be very efficient. In fact, CO2 probably limits the time you can be underwater and conscious as much as O2 does. CO2 is what will force you to inhale, long before you black out from hypoxia.

    A completely lack of oxygen delivery to the brain gives you about four minutes to significant brain damage, at normal body temperature; at lower core temperatures, that period is longer. But the brain has a lot of mechanisms to stay warm, so the cases where people have survived immersion in cold water are generally cases where they were IN the water for a long time before going UNDER the water -- long enough to allow core temperature to fall significantly. A person who falls off a boat into cold water and is knocked unconscious is going to have brain damage in about the four minute time.

    When we do intubations, though, we have the person breathe 100% O2 (1ATA) to preoxygenate -- and in that circumstance, we may have as much as 8 minutes before the oxygen level in the blood even falls significantly. 1 ATA is essentially the ppO2 of someone at 60 feet on 32% -- so someone deprived of breathing gas at that depth, who has been breathing that mix, has quite a long time before they'll desaturate enough to pass out, assuming they are not flailing.

    There are a lot of variables in this question.
     
  2. elmer fudd

    elmer fudd Solo Diver

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    Most free divers can learn to hold their breath for up to 4 minutes while at rest without blacking out and many can go longer than that. Dynamic apnea, (holding your breath while actually doing something), is much harder and the breath hold times are usually much shorter.

    Free diving and drowning are considerably different though. A free diver generally takes a few deep breaths first and then fills his lungs to their maximum capacity and then some. He's also aiming for some zen like state of relaxation. A drowning victim on the other hand likely starts with half empty lungs and in a state of full on panic. Still, I suspect that it must take at least a minute for a drowning victim to fully lose consciousness. One of the things I've practiced is holding my breath for 30 seconds at random points in my breathing cycle, (like if a regulator suddenly got ripped from my mouth and it took me a moment to get to my octo). When your lungs are empty, it's definitely much harder to hold your breath, but I've always managed to last 30 seconds.

    As to how much longer it would take after passing out to actually croak, that I don't know. If a diver or swimmer has only passed out for a few seconds though blowing air across his/her face will often restore their breathing.
     
  3. Tigerman

    Tigerman Solo Diver

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    DONT expect splashing/thrashing/flailing and/or screaming in a drowning victim - They are likely to to be too busy trying to breathe to do any of the above and fail bad enough to be unable to scream..
    Parents has been feet away from their drowning children for this exact reason! - "But, it didnt look like there was a problem"..

    Not that relevant to what youre asking, but VERY relevant to everyone that goes to a beach..
     
  4. DevonDiver

    DevonDiver N/A

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  5. Tigerman

    Tigerman Solo Diver

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    Thank you DevonDiver for the more in-depth explanation. The ones I have links for are in norwegian :p

    Sent from my GT-I9300 using Tapatalk 4 Beta
     
    divewench1 likes this.
  6. DCBC

    DCBC Banned

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    More often than not, a lifetime... :)
     
    Jill from Phoenix likes this.
  7. ianr33

    ianr33 Solo Diver

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    This is an interesting discussion. What I would like to know though is does it hurt? if it all went wrong on a dive one day, and I ended up breathing in water at depth, can I look forward to a peaceful end or an agonizing one?
     
  8. DCBC

    DCBC Banned

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    If you drown in freshwater drowning, the water filling the lungs is hypotonic to the blood (moves into the bloodstream) diluting the plasma and causing red blood cells to burst. This will lead to cardiac arrest in time. If you drown in saltwater, the opposite effect occurs. Saltwater is hypertonic and the plasma is conveyed into the lungs (you drown in your own fluids). Air exchange is prevented and cardiac arrest eventually occurs (Lunetta, P. & Modell, J.H. 2005: Macropathological and Laboratory Findings in Drowning Victims).

    I'm not sure about the pain involved. I've read a few reports of near drownings and the Victims usually report the most negative part of the experience was the panic and struggle that ensued and not any physical pain. In any case, unconsciousness occurs quickly.
     
  9. CAPTAIN SINBAD

    CAPTAIN SINBAD Divemaster Candidate

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    Seems like all this fear of drowning is actually a the fear of a few seconds of ... discomfort and panic.
     
  10. Doppler

    Doppler Dive Equipment Manufacturer

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    No, I think fear of drowning is fear of death...
     

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