Medical Priority Dispatch System

Protocols were first alphabetized by chief complaint that included key questions to ask the caller, pre-arrival instructions, and dispatch priorities.

These questions allow the dispatchers to categorize the call by chief complaint and set a determinant level ranging from A (minor) to E (immediately life-threatening) relating to the severity of the patient's condition.

The first component, a number from 1 to 36, indicates a complaint or specific protocol from the MPDS: the selection of this card is based on the initial questions asked by the emergency dispatcher.

The MPDS codes allow emergency medical service providers to determine the appropriate response mode (e.g. "routine" or "lights and sirens") and resources to be assigned to the event.

For example, in the United Kingdom, most, but not all front-line emergency ambulances have advanced life support trained crews, meaning that the ALS/BLS distinction becomes impossible to implement.

In an independent report into the emergency response to the Manchester Arena bombing, an Advanced Paramedic for the North West Ambulance Service stated it was "very much understood" that MPDS "vastly underemphasises the priority of traumatic calls.