this is a very good technical question. . .ok, a sleeper hold, though still technically a choke, is applied to the neck to cut off blood flow in the carotid artery so that the brain doesn't receive any oxygen. . when properly applied, you should not feel much pressure on the wind pipe. . a rear naked choke is just that, an arm around the neck, which can be locked in in a few different ways to cause your opponent pain and choking, this is generally against the windpipe. . and BTW damage to the windpipe is permanent. . please be careful when you play or fight!