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Sea Kayaks Techniques Bulletin Board
Re: Cold water reactions
Posted By: Carl Tjerandsen In Response To: Cold water reactions (brad shepard)
Date: Friday, 24 May 2002, at 11:00 a.m.
: The gasp is actually
: bronchospasm produced by the mammalian diving reflex.Brad,
Perhaps the physiologists have enlarged our understanding of these phenomena, since I last looked into the literature, but I'm wondering if you are mixing the dive reflex into a situation where it doesn't belong. People with bronchospasm don't hyperventilate. They hypoventilate. The phenomenon Brian aptly describes is most likely due to the sudden shock and pain of abrupt cold immersion, a sympathomimetic response, which would tend to open the bronchioles. The hyperventilation reflex will greatly reduce your breath holding time (rolling time-by as much as 75%), produce reduced cerebral blood flow and dizziness, with some loss of muscle coordination during the 5 minutes or so it usually lasts. Maybe you are confusing vocal cord spasm (which can happen in dry drowning and I believe the dive reflex) with bronchospasm.
Please instruct me, if I've managed to get some part of this wrong.
Regards,
Carl Tjerandsen
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