Is it possible to pass out while having sex? if so, has it ever happended to you?

Of course it's possible, and I've passed out several times. My gf is a dominatrix that is into marathon sessions with multiple partners, usually meaning that there is a bunch of guys that gang rape me for hours on end. Then my gf ties me up and we have intense BDSM sex until I just can't anymore. Sometimes I simply pass out from exhaustion and/or pain. She'll bring me to with ice water if she can and we continue. Sometimes, I just won't come to, though.