when i was younger some friends and I use to do this really stupid thing where u take a huge breath through your mouth,hold it in,stand with your back against a wall,put your thumb in your mouth like a child does when sucking it,but dont suck blow your thumb instead making sure your mouths as air tight as possible, do that for 30 whilst someone is pushing on your chest and then you would pass out for like 5 seconds but you would feel like you'd been out for time anyway I STRONGLY suggest you DO NOT do anything like this to starve your brain from oxygen xx keep blazin' xx