When the capacity of a region's medical resources are exceeded during an incident, then it can be termed a disaster.


Categories of Casualties:

(1) dead and dead-on-arrival

(2) life threatening cases needing immediate attention

(3) non life-threatening cases requiring hospital treatment

(4) casualties not necessarily requiring hospitalization


Examples of events and the casualty mix expected:

(1) more killed than wounded: floods, volcanic eruptions

(2) category 1, 2 or 3 casualties exceed 50% of people exposed: fires, major railroad accidents, earthquakes, terrorist bombings, aircraft accidents

(3) majority of injured as category 4 casualties: civil disturbances


Severity of an incident in terms of injury (S):

(1) if many seriously wounded casualties are expected (categories 2 and 3), then the S value is 1.5

(2) if only many slightly injured persons are expected, then the S value is 0.5

(3) intermediate situations such as traffic accidents have an S value of 1.0


Hospital Treatment Capacity:

(1) The hourly treatment capacity is the number of category 2 and 3 casualties that can be treated according to normal medical standards in one hour.

(2) For general hospitals, this is estimated as 3% of the total number of beds.

(3) Since most hospitals can work efficiently for up to 8 hours, the total capacity is taken to be 8 times the hourly treatment capacity.


Medical Rescue Capacity:

(1) The rescue capacity depends on the number of trained medical professionals available at the disaster site.

(2) A trauma team with surgeon, anesthesiologist, nursing support and supplies can handle about 10 category 2 and 3 patients per hour.

(3) Under difficult conditions, the capacity to deliver care is reduced.

(4) The rescue capacity should equal the hourly hospital treatment capacity of the region.


Medical Transport Capacity:

(1) The transport capacity depends on the number of ambulances with drivers, and it is affected by the ease of evacuation, the distribution plan, and the size of the event.

(2) A typical ambulance crew can be expected to handle 2 patients per hour, but this may be reduced by poor conditions.

(3) The transport capacity should try to match the hourly hospital treatment capacity of the region.


medical severity index =

= (casualty load) * (severity of incident) / (total capacity of region)



• If the medical severity index is <= 1, then the local region can manage the event.

• If the medical severity index is > 1, then the incident can be termed a disaster, requiring outside assistance.


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