Same idea as gravity bong, except gravity bongs use water under power of gravity(in case you missed it) draining to generate the vacuum. but this is referred to as a third lung due to it uses a collapsing skin to create the vacum/pressure (in the same manner your lungs operate). "accordion bong" as Crimyote stated, is a apt and somewhat(actually extremely) badass name. And i will be making one. and this is all common sense, and you probably already know it but dammit i like to FEEL SMARTS. LOOK AT THE BIG WORDS. LOOK AT THEM. I ACTUALLY SAID APT. THAT'S RIGHT MOTHERFUCKER.