Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: DoctorBeaver on 12/08/2007 20:33:22

Title: Schoolyard fainting trick
Post by: DoctorBeaver on 12/08/2007 20:33:22

I remember when I was at primary school (yes, they DID have them back then!) we used to do this thing where we'd hyperventilate for a minute or so then someone would squeeze us in a bearhug causing us to faint.

Why did that happen and was it dangerous?

Title: Schoolyard fainting trick
Post by: another_someone on 13/08/2007 20:23:31

The human body does not breath in response to a lack of oxygen, but rather to an excess of CO₂ (i.e. it regards expelling CO₂ as more critical than absorbing O₂).

If you hyperventilate, it is quite possible that the can expel so much CO₂ that it stops breathing, even when it is is need of more O₂.  This can cause the brain to become starved of oxygen (causing the fainting) without the breathing reflex kicking in.  It can theoretically cause death (which is why when I tell people that I used to regularly hyperventilate and then spend around 4 minutes underwater, they tell me that I was being stupid - and I certainly did panic one of my teachers who thought I was on the verge of drowning).

The bear hug may have simply be an additional way of restricting the ability to breath (and because there was no overload of CO₂, it would not cause a panic reaction that might cause you to fight yourself free to gain more breath).

Title: Schoolyard fainting trick
Post by: DoctorBeaver on 13/08/2007 22:06:52

Ian - that sounds feasible. I've been wondering about this for years but only just thought to ask.