Medical Priority Dispatch System

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The Medical Priority Dispatch System (MPDS) is a unified system used to dispatch appropriate aid to medical emergencies including systematized caller interrogation and pre-arrival instructions. Priority Dispatch Corporation is licensed to design and publish MPDS and its various products.

MPDS was developed by Jeff Clawson from 1976 to 1979 when he worked as an Emergency Medical Technician and dispatcher prior to medical school. He designed a set of standardized protocols to triage patients via the telephone and thus improve the emergency response system. Cards were first alphabetized by chief complaint that included key questions to ask the caller, pre-arrival instructions, and dispatch priorities. After many revisions, these simple cards have evolved into MPDS.

MPDS today still starts with the dispatcher asking the caller key questions. 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. Some systems also use the determinant O which may be a referral to another service or obvious death. Another sub-category code is used to further categorize the patient. For instance, a suspected cardiac or respiratory arrest where the patient is not breathing is given the MPDS code 9-E-1, whereas a superficial animal bite has the code 3-A-3. The MPDS codes allow emergency medical systems to determine the appropriate response mode (i.e. routine or "lights and sirens") and resources to be assigned to the event.

The system is often used in the form of a software system called ProQA, which is also produced by Priority Dispatch.

Dispatch Determinants[edit]

Each dispatch determinant is made up of three pieces of information, which builds the determinant in a Number-Letter-Number format. The first component, a number from 1 to 36, indicates a broad category or specific "Card" from the MPDS: the selection of this card is based on the initial questions asked by the emergency dispatcher. The second component, a letter A through E (including the Greek character Ω), is the response determinant indicating the potential severity of injury or illness based on information provided by the caller. The third and final component, a number, is the sub-determinant and provides more specific information about the patient's specific condition.


Card Category Card Category
1 Abdominal Pain/Problems 20 Heat/Cold Exposure
2 Allergies (Reactions)/ Envenomations (Stings, Bites) 21 Hemorrhage/Lacerations
3 Animal Bites/Attacks 22 Inaccessible Incident/Entrapments
4 Assault/Sexual 23 Overdose/Poisoning (Ingestion)
5 Back Pain (Non-Traumatic/Non-Recent) 24 Pregnancy/Childbirth/Miscarriage
6 Breathing Problems 25 Psychiatric/Suicide Attempt
7 Burns (Scalds) /Explosions 26 Sick Person
8 Carbon Monoxide/Inhalation/HAZMAT/CBRN 27 Stab/Gunshot/Penetrating Trauma
9 Cardiac or Respiratory Arrest/Death 28 Stroke (CVA)/Transient Ischemic Attack (TIA)
10 Chest Pain 29 Traffic/Transportation Incidents
11 Choking 30 Traumatic Injuries
12 Convulsions/Seizures 31 Unconscious/Fainting(Near)
13 Diabetic Problems 32 Unknown Problem (Man Down)
14 Drowning/Diving/SCUBA Accident 33 Inter-Facility Transfer/Palliative Care
15 Electrocution/Lightning 34 Automatic Crash Notification (A.C.N.)
16 Eye Problems/Injuries 35 HCP (Health-Care Practitioner) Referral (United Kingdom only)
17 Falls 36 Flu-Like Symptoms (Possible H1N1)
18 Headache 37 Inter-Facility Transfer specific to medically trained callers
19 Heart Problems/A.I.C.D.

Card 36[edit]

This card was created to handle the influx of emergency calls during the H1N1 pandemic: it directed that Standard EMS Resources be delayed until patients could be assessed by a Flu Response Unit (FRU), a single provider that could attend a patient and determine what additional resources were required for patient care to reduce the risk of pandemic exposure to EMS Personnel.

Response Determinant[edit]

Type Capability Response Time
Alpha Basic Life Support Cold (single unit)
Bravo Basic Life Support Hot (multiple units)
Charlie Advanced Life Support Cold (single unit)
Delta Advanced Life Support Hot (multiple units)
Echo Advanced Life Support and special units Hot (Multiple units) plus nontraditional responders


Response Determinant NHS England Clinical Response Model[citation needed][edit]

Letter Severity Resources Response
RED 1 Immediately Life Threatening Emergency Community Responder, Community Defibrillation, Nearest & Quickest Advanced Life Support Emergency
RED 2 Possibly Life-Threatening Community Responder, Nearest & Quickest Advanced Life Support Emergency
Green 1 Serious but NOT Life-Threatening Face to Face Clinical Assessment within 20 minutes Emergency
Green 2 Serious but NOT Life-Threatening Face to Face Clinical Assessment within 30 minutes (Urgent) Emergency
Green 3 Planned Clinical Telephone Assessment Planned clinical telephone assessment call back within 10 minutes Non-Emergency
Green 4 Face to Face Clinical Assessment within 60 minutes Transport to Emergency Department within 60 minutes, Urgent Admission (HCP) within 1, 2 or 4 Hours Non-Emergency

Response Determinant NHS Wales Pilot Clinical Response Model[citation needed][edit]

Letter Severity Details Response
RED Immediately Life Threatening Multiple Vehicle Dispatch - Lights and Siren Emergency Response
AMBER 1 and 2 Life-Threatening / Serious Calls Lights and Siren Emergency Response
GREEN 2 and 3 All other calls Face-to-face response - Clinical telephone assessment Non-Emergency Response

See also[edit]


  1. ^ Clawson, Jeff. "excerpts from The Principles of Emergency Medical Dispatch" (PDF). National Academy of Emergency Medical Dispatch. Retrieved 18 September 2013.