What are the requirements for a an emergency medical visa?

My husband is in india with his father right now, he received a kidney transplant and it went seriously wrong, enough oxygen did not get to his brain in time. He received the operation on the 18th. He is now in a vegetative state with a score of 4. Anything below an 8 is very serious and critical. He has a feeding tube and on a ventilator. He is responding but it seems involuntary. The doctors say there is no hope and there is no facilities to care for him. My father in law has no where to go with his condition. If he goes home he will die without the feeding tube and ventilator. My husband wants to bring him to the states with him so we can put him in the facilities that can help him. My husband is a united states citizen. What are the requirments?