A blood choke cuts off blood flow to the brain and gradually puts the fighter to sleep, unlike an air choke such as the rear naked choke which causes a sensation of agony and breathlessness.
« it's not an air choke, it's a blood choke. You're blocking the blood supply and that's what causes you to eventually pass out. You pass out - it's the kind of choke where it's not like with rear naked chokes where you feel like you're in agony and can't breathe. With this one you just fall asleep. »