4 Minute Population Coverage

The Importance of the 4-minute Response In the Delivery of EMS:

Of the many types of medical emergencies firefighters respond to, the Mansfield Fire Department’s response to cardiovascular accidents (stroke) and myocardial infarctions (heart attacks) are the most time critical.  A stroke is a sudden loss of brain function.  It is caused by the interruption of the flow of blood to the brain or the rupture of blood vessels in the brain.  The interruption of the blood flow or the rupture of blood vessels causes brain cells in the affected area to die.  A heart attack occurs when the blood supply to part of the heart muscle itself is severely reduced or stopped.  This happens when one of the arteries supplying blood to the heart muscle is blocked.  If the blood supply to the heart muscle is cut off for longer than several minutes, muscle cells in the affected area suffer irreversible injury and die.


The American Heart Association notes that, “Nearly 2,600 Americans die of cardiovascular disease each day, an average of 1 death every 34 seconds.  Cardiovascular disease claims more lives each year than the next 5 leading causes of death combined, which are cancer, chronic lower respiratory diseases, accidents, diabetes mellitus, and influenza and pneumonia.”[1]  According to the Occupational Safety & Health Administration, there are 300,000 – 400,000 deaths per year in the United States from cardiac arrest,[2] making it one of the leading causes of death in the nation.  Most cardiac arrest deaths occur outside the hospital, resulting in survival rates ranging between 1% and 5%. 


[1] American Heart Association, “Heart Disease and Stroke Statistics – 2004 Update;” AHA website

[2] U.S. Occupational Safety and Health Administration, Technical Information Bulletin: Cardiac Arrest and Automated External Defibrillators (AEDs), < http://www.osha.gov/dts/tib/tib_data/tib20011217.html >


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The Chain of Survival

In spite of these statistics, cardiac arrest remains one of the most time-critical medical emergencies that can be treated in the field. The four-part “chain of survival” concept, as illustrated in the following figure, is essential to ensuring positive patient outcomes. 


The “Chain of Survival” consists of:

Early Access:
Quickly calling the Emergency Medical Services (9-1-1) syste
Early CPR:
Promptly giving cardiopulmonary resuscitation when needed
Early Defibrillation:
Having proper equipment and being trained to use it when indicated
Early Advanced Cardiovascular Care:
Initiating advanced airway management and I.V. and drug therapy

GIS Web-Mapping

The following map represents the GIS analysis demonstrating the total population count within the 4 minute response area. Population data were compiled using Geoprocessing, rather than network coverage to show the total count as well as percent of the total population for each fire district. EMS services are solely a humanistic field and therefore coverage of where the population is actually located is the best determinant of system efficiency.


Download the map in a printable PDF format.

Interpretting the Results

Under current conditions, the fire department is capable of responding to 64% of the total population within 4 minutes, assuming all units were staffed and available to respond immediately upon dispatch. The following output table indicate the 4 minute coverage breakdown by each Engine company district:


Table 1: 4 Minute – Population Coverage – Current Organization and Deployment

Fire District

Total District Population

Total Population Serviced within 4 Minutes

% of Population Serviced within 4 Minutes


























The Importance of Early Defibrillation within 4 Minutes

The use of an automated external defibrillator (AED) by trained personnel is integral to the treatment and survival of cardiac arrest.  Abnormal heart rhythms, with ventricular fibrillation (VF) being the most common, cause cardiac arrest.  Defibrillation within 2 minutes can produce cardiac arrest survival rates as high as 90%.  However, “if defibrillation is delayed more than 10 minutes, survival rates drop to less than 5%.”[1]


“Cardiac Arrest Survival Rate”


While patient survivability from cardiac arrest depends upon a series of critical interventions, such as are provided by firefighters cross-trained as EMTs and Paramedics, “rapid defibrillation is the most important single factor in determining survival.”[2]  The highest hospital discharge rates have been achieved in cardiac arrest patients in whom CPR was initiated within 4 minutes of arrest and ACLS within 8 minutes.  A rapid emergency medical response is therefore essential in improving survival rates.[3]


So effective is the use of an AED in increasing survivability of cardiac arrest patients, the International Association of Fire Chiefs has endorsed equipping every fire suppression unit in the United States with an automated external defibrillator.[4]  Mirroring this recommendation, NFPA 1710 states, “the fire department… shall ensure [that] emergency medical response capability includes personnel, equipment, and resources to deploy at the first responder level with automatic external defibrillator (AED) or higher treatment level.”[5]  In accordance with NFPA Standard 1710, Section 4.3.2, the Mansfield Fire Department equips all of its apparatus with AEDs and ensures all firefighters are trained in their proper and effective operation. [6] 

[1] American Heart Association, Sudden Deaths from Cardiac Arrest Statistical Fact Sheet (2003)

[2] Emergency Cardiac Care Committee and Subcommittees of the American Heart Association, “Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiac Care,” Journal of the American Medical Association (October 28, 1992): 2289

[3] Ibid, 2184.

[4] American Heart Association, Sudden Deaths from Cardiac Arrest Statistical Fact Sheet (2003).

[5] NFPA 1710, § 4.3.2 - “The fire department… shall ensure [that] emergency medical response capability includes personnel, equipment, and resources to deploy at the first responder level with automatic external defibrillator (AED) or higher treatment level.”

[6] NFPA 1710, §