Yeah, my freinds (funny) strangled me by accident, i think. Im sure this is probably similar to the effects of what youre talking about now.

The guy (Leon) held me (strongly) for a few seconds and slowly slowly i started to drop, sounds around me where echoing really really quickly, and i was slowly dropping to the ground. It was kind of like watching the world through your eyes whilst detaching from it.

At the same time Leon was slapping me making me come out of it, it was as though his slaps were far off. Woke up after about 10 secs, strange really strange.

NB: Its also quite dangerous, after doing this it was popular in the school to do it for a while after that. One guy was held for a bit too long and fell backwards onto london's concrete (lucky he didn't knock his head), LOL funny as hell though.