I've had sex with guy who was VERY into it. I would strangle him to the point he passed out. I was very inexperienced and it was more for his pleasure than mine. He passed out and came back too. It's t do with oxygen starvation heightening all senses, esp orgasm. I havent tried it since and it's of cusre very dangerous - cutting blood supply could lead to brain damage; you have to cut the air only.
A mild version is breath control - eg place your fingers over each others nose to block air, then start kissing and blowing/sucking air into each other - ie you blow, your partner sucks, then swap, but not allowing any fresh air. As you use up up oxygen and exhale depleted air so it gets ever more frantic as you naturally want more air but cant get it.
Who said romance was dead?