In the U.S. "critical illness" is used to indicate a condition serious enough to require advanced medical care to survive. Those patients are moved to Intensive Care Units or other specialized care units (Cardiac, Burn, etc) even if that means being moved to a different hospital with those capabilities. Without specialized care, thier chance of dying unacceptably high. However, once in a specialized unit, many (if not most) will survive.
That is where I work.
I hope everyone is OK!!