I should probably insert a disclaimer here: I have no plans to do this in real life.
But:
In my real life, i'm an alternative therapist. Though i wouldn't do it myself, many people like me offer colonic irrigation. Personally, it seems unhealthy and dangerous to me, but the point is, there's an appeal there. Now the thing is, if people are prepared to let strangers do that to them, the tantalising possibility exists that if someone did set up a clinic offering to inflate people's insides with air, there would probably be some takers with the right kind of approach.