Ok, so I'm sitting here holding my breath--think for a minute and you'll guess why--and I'm just about at that point where I can't hold it any longer. I'm just about to exhale, but then I have to yawn. Usually, when I'm just about to exhale, I get just a tiny little panic feeling, which I assume is due to the buildup of CO2 in my brain. But just now when I yawned, I held my breath for a good 5-7 seconds longer (due to the yawn itself), and felt no panicky feeling at all. I've heard a hypothesis or two about how yawns have something to do with CO2 levels in the brain. I wonder if this lack of panic feeling in spite of going several seconds longer than seemed possible is a clue at all. If it's nonsense, then just have a laugh at it. I've lost count of how many times I've held my breath tonight.