The Federaul Bureau of Prisons has a process for compassionate medical release for inmates who are severely ill. If your friend is suffering from a variety of medical conditions, he may qualify. Here is the specific information about the procedure:
http://www.bop.gov/policy/progstat/5050_046.pdf
FBOP also has protective custody available if it is considered likely that your friend would suffer harm or abuse due to being frail or elderly. An objective evaulation would need to take place to determine if that classification is accurate in this case.