Don't hyperventilate before swimming underwater
Mark Spahn
I think it was from you that I learned about the phenomenon whereby
hyperventilating before swimming-for-distance underwater interferes with
the mechanism by which the body recognizes when it is time to breathe
again, and can cause drowning even by fit athletes. There is a term for
this, and an interesting Wikipedia article about it, but I forgot the
term and can't find the article. Can you refresh my memory?
http://www.nbcnews.com/health/health-news/dont-hold-your-breath-cdc-reports-pool-accidents-n362786
mentions this phenomenon, and the fact that it is hard to notice a
person who is drowning in a crowded pool (which Steve Sailer has written
about). Why are drowning people so hard to notice? Because drownings
occur quietly. A drowning person does not have the energy to loudly
shout "Help!" while thereby depleting his lungs of air. (And
articulating the consonants LP makes "help" a poor word for summoning
assistance. What we need is an international "Mayday" cry to be adopted
by drowners. The optimum combination of consonants and vowels for this
"I'm drowning" message is a topic for research.)
-- Mark Spahn (West Seneca, NY)
Mark Spahn
Gerry, Thanks for finding this. So that's what it's called:
shallow water blackout (more correctly, shallow-water blackout;
it's the water that's shallow, not the blackout); i.e., underwater
fainting.
The relevant part from your essay:
==QUOTE==
It turns out, I now learn, that we were doing something very foolish. And I exacerbated that foolhardiness by often swimming those [underwater] laps alone in the pool. There is an effect associated with this kind of underwater swimming so important that it has been assigned a name, shallow water blackout. People die from it. Last summer, for example, Annapolis midshipman Kyle Hurdle passed out while doing so and lifeguards were unable to revive him.
Christian Swezey described this phenomenon in The Washington Post: "Normally, a person can hold his breath for about a minute before the respiratory center reacts to growing levels of carbon dioxide in the blood and demands a breath. In order to prolong the time between breaths, some athletes hyperventilate on purpose, meaning they breathe more than necessary before going underwater, trying to rid the blood of carbon dioxide. This fools the brain into thinking it doesn't need to breathe even when its oxygen stores are dangerously low."
With no carbon dioxide to trigger breathing, the swimmer experiences muscle cramps, tingling, dizziness and blurred vision. More important, the brain finally shuts down, the swimmer faints and his or her lungs involuntarily take in water.
It is important to understand that this is not just a concern for beginners. As Hurdle's accident indicates, it is even more a problem for intermediate or advanced swimmers who consider this kind of breathing part of their training.
The 1999 Navy Diving Manual includes instructions related to shallow water blackout. Navy divers take no more than two or three breaths before diving.
==UNQUOTE==
And here's the Wikipedia article on this phenomenon:
https://en.wikipedia.org/wiki/Shallow_water_blackout
(with photo and graphs).
This reminds me of another activity that is more dangerous than
it seems: tug-of-war, which if not done right can allow the force
of many people to be concentrated on one person's hand or wrist,
causing serious injury.
-- Mark Sp.
On 9/16/16 5:28 AM, Mark Spahn wrote:
I think it was from you that I learned about the phenomenon whereby hyperventilating before swimming-for-distance underwater interferes with the mechanism by which the body recognizes when it is time to breathe again, and can cause drowning even by fit athletes. There is a term for this, and an interesting Wikipedia article about it, but I forgot the term and can't find the article. Can you refresh my memory?
Shallow water blackout. I had to look it up in my article.
See http://www.acsu.buffalo.edu/~insrisg/nature/nw15/0301Underwater.htm