The curtains are symbolic
This film seems to be senseless and pointless. But, it is much more. I hope someone has the time to examine everything in detail, as I am too lazy to write an entire post of explanation.
By the way, you should also realize that the patients were more normal than the lives of their physicians. And they made it simpler when the doctor says that it is easier to treat a patient than to examine one's own family.
Best unknown feature at IMDB.com
http://www.imdb.com/features/video/browse/