If he is not in the hospital, I think they will expect him to be wheeled there. Once there, you can fill out most of the stuff, and he signs. I hopped on down on a walker with a broken leg with my gf. Her and an immigration officer did all the work. I was told to "sit here and take care of my leg". Also note that applying for a medical extension is very hard to do. I was told by the officer that after this extension she just did for me, it would be easier to fly out and back in if I was ANY WAY MOBILE than try to get a medical extension.