I have my slave in the latex vacuum cube with only his head exposed, but I have covered his head with a rubber rebreathing hood. This hood has a pocket inside for air and small holes to bring new air in. This means that the slave must breathe slowly or he will begin to suffocate. I make this difficult but teasing him with my feet, ass, and by pinching the holes shut so he must struggle for breath. Soon he is woozy and on the verge of passing out.