That's a relatively short move, ambulance or ambulance van should work. There are very few "accessible" RVs, particularly if you are talking about litter patients, and ambulances have the litter handling capability and have life support systems you will find in no rental RV.
I've been through this 2011-2014 with the loss of five family members in three years, trying to make these last minute connections. When my wife was terminal, we chose not to move her, opening our home hospice to anyone who cared enough to visit. We did not try to move her around, because any movement was painful and shortened her life.
My brother was in a similar condition when he finally accepted that he was terminal, and he chose to try move from his Florida estate to go into hospice in Michigan, where his mother and three sisters could care for him, hiring air ambulance ($45,000) for the move. He did not survive the flight. We put a physician family member on the flight with him, that meant only he had someone in family to be with him when he died.
What you can try will depend on yor financial resources, but for a fragile terminal patient, I would not be looking for a RV, rather something more like med-evac.
For what it is worth, I am pretty sure there is no such thing on the market as a RV that meets ISO standards for medical evacuation.
