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Old 09-07-2005, 08:10 AM
Join Date: Aug 2005
Location: Perth, WA
Posts: 2,397
Why is it easy to hold your breath after hyperventilating?

I remember reading in the newspaper a rather sad article about a teenager who drowed while having a breath-holding contest with some buddies. The article warned that it was easy to pass out without warning if you hold your breath after hyperventilating. Hmm, I thought, and like a good little scientist decided to try this myself to see *why* it was easy. So, a few days later, I sneak outside during a boring dinner party and start hyperventilating. I go at it for about two minutes, then hold my breath for another two without feeling the need to take a breath at all. Hey, this is neat, I think, I've been holding my breath for two minutes now and I -


Next thing I remember is hitting the lawn. Get up and glance around surreptitiously. Nobody seems to have seen me. Good. I return to the boring dinner party slighty worse for wear.

So... I seem to have confirmed that it is indeed very easy to pass out after hyperventilating, because your body does not register your need for oxygen as well and doesn't try to force you to start breathing again. But does anyone know why this is so?
Old 09-07-2005, 08:15 AM
Join Date: Aug 1999
Location: A Brit in 'Stralia
Posts: 1,964
Your body determines that you need to breathe mainly by monitoring the amount of CO2 dissolved in your blood, rather than the amount of oxygen. If you hyperventilate, you flush out a lot of CO2 and artificially lower the level in your blood. If you then hold your breath, your oxygen level can drop low enough to make you pass out before the CO2 level has risen high enough to force you to breathe.
Old 09-07-2005, 08:23 AM
Join Date: Oct 2003
Location: #7
Posts: 1,030
isn't that how the kids are getting cheap highs these days? Maybe backwards, they seem to suffocate first and then hyperventilate. link

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