adywan said:
His lungs wouldn't have been affected. I'm going to be adding something that explains why he has to breath artificially when i get to ROTS:R

You shouldn't have to. Being in such close proximity to major volcanic activity would fry anyone's lungs. (Of course, if we're being realistic, both Obi-Wan and Vader should have been frying early on, but for all we know Vader was lying there for hours before Palpatine got to him.)

That said, I'll be interested to see what you have in mind.