It is a comotose state, drug induced by doctors. It is usually taken as an option when the patient needs to be sedated in order to aid recovery (e.g. when they have had a stroke, or undergone brain or other major surgery). In these cases the patient's physical and mental activities need to be surpressed until they are fit enough for them to be allowed to resume.
This may be inreference to Arial Charon, who is in such a condition - although today his doctors plan to withdraw the drugs maintaining his coma state, so they can assess any brain damage caused by his recent stroke.
I thought a coma was medically induced to reduce brain activity. Situations where this would be applied are bruised brains due to the result of accidents or surgery. An inactive brain apparantly heals better, and reduces the swelling.