The patients within a hospital are often deemed incapable of self preservation. This means that when they enter under the hospital’s care that the hospitals is responsible for protecting them in the event of an emergency such as a fire. Hospitals are broken down into smoke compartments to allow hospital staff move patients horizontally to an adjacent smoke compartment in the event of smoke/fire. If the fire continues to grow then the hospital staff will move vertically to a floor below the fire. Only as a final resort will hospital staff evacuate patients from the building.
For the official definition reference NFPA 99 Health Care Facilities Code (2012) 3.3.35 and the associated Annex A material.