DEFINITION:
A state of unconsciousness, with no reaction to external stimuli or response to internal needs, continuing for at least 4 days. Life support systems must be required throughout the period of unconsciousness.

INTERPRETATION:
Comas are caused by brain damage arising most commonly from head injury, stroke, diabetes, internal bleeding or oxygen starvation. This definition requires the coma to persist for at least 4 days and life support systems to be necessary during that period.