[klyrs]

> And people also hyperventilate on their own, but mostly preparatory to diving or holding their breath for some other reason.

It's common for people to hyperventilate in the midst of a panic attack, and the common advice I've seen is to encourage a panicked person to take deep breaths. Strange to see it as a consideration for beneficial effects. As a kid I'd hyperventilate to feel dizzy because it was fun (oops was I getting high?)