How to Get Better Sleep Post Heart Surgery?

Actually my grandfather had a minor heart attack some years ago and he's also having an open heart surgery done (peacemaker). Now he's getting suffocated and takes help of oxygen. Sometimes his condition gets very bad and we loose the hope. The main problem is that he can't sleep at night. Not even a single minute. We did everything to make him sleep but he can't sleep and because of this lack of sleep‚he's not in his senses. Why? Can anything be done to make him sleep at night so he can get rest and will feel better. Please share your opinion and tell me some cures