EMS System Design



The emergency medical services (EMS) system is a complex combination of various providers and facilities that provide three basic medical functions: stabilization, evacuation, and redistribution. Although organizational structures and resources vary worldwide, the fundamental components of any EMS system are essentially the same. This chapter will provide the EMS physician with a vital understanding of the organization of EMS systems and how such design considerations provide ­challenges and opportunities for patient-centered emergency medical care.



  • Define the EMS system in terms of the overall medical response to emergencies.

  • List the original 14 components of an EMS system.

  • List and describe the components of an EMS system as defined by NHTSA.

  • Describe the basic types of emergency medical service agencies.

  • Describe the main differences between urban and rural EMS systems.

  • Discuss how community groups, corporations/businesses, patient advocacy groups, and health care facilities affect EMS system design.

  • Define mutual aid and describe how it is employed in EMS system design.

  • Discuss state, regional, and local EMS councils and/or administrations.

  • Discuss state, regional, and local medical oversight committees.



The entry of a patient into the emergency health care system brings with it a complex cascade of events, with a number of possible outcomes. Figure 12-1 displays a simplified look at the emergency health care system from the time of entry to the time of exit. Most striking to this flow diagram is its serial nature, and therefore, input to one process is limited by its output. This input-throughput-output conceptual model of the emergency health system is essential to consider as one examines the design of EMS systems, as an output limitation such as unstaffed ambulances or hospital crowding will progressively limit the system’s ability to function and respond to the demands placed on it.1,2

FIGURE 12-1.

Patient flow within the emergency health care system.

The majority of patients who enter the emergency health care ­system do so by making a telephone call to the 9-1-1 system. The Medical Priority Dispatch System (MPDS) or the Association of Public-Safety Communications Officials (APCO) Emergency Medical Dispatch Program are specifically designed to abstract this caller information through a question-driven protocol and direct appropriate resources based on that information. Although a complete discussion of Emergency Medical Dispatch will be covered in Chapter 15, it is important to recognize that nearly all public safety answering points (PSAPs) are able to begin rendering care for the patient over the phone by using prescripted, postdispatch, and prearrival instructions.36 The instructions could include directing a bystander to perform CPR, assist with the delivery of a newborn, or direct self-care such as hemorrhage control or aspirin administration. Further, the prioritization of requests for EMS service through any call-taking program based on call severity is essential to the underlying mission of getting the right equipment to the right patient at the right time.


The standard response to a request for service includes sending an ambulance. There are limited circumstances in some systems whereby based on caller interrogation the requestor may be directed to alternative sources of care (eg, a poison control center for an accidental ingestion without any symptoms) or attended to by first responders without transport capability (eg, a request for lifting assistance). Depending on system design, the ambulance that is dispatched could be able to provide care at the BLS level, the ALS level, or in some systems may utilize a BLS ambulance with an ALS intercept (paramedic engine, paramedic “fly-car,” etc). In systems that do not send ALS resources on every request for service, the use of an EMD program often allows differentiating those requests for service that are most likely to require ALS from those most likely to require BLS, and therefore assign resources accordingly. Determining which types of calls get which types of resources is often the responsibility of the 9-1-1 center or the system’s medical director.

First responders are essential to the EMS system, particularly for cases of imminent life-threatening conditions such as choking, ­respiratory arrest, or cardiac arrest. Various systems employ a myriad of ­first-­response deployment models. This could include fire department or law enforcement, and be trained and able to provide care anywhere from the first responder to the paramedic level. Further, depending on the historical influences on system design, these first responders could be dispatched on everything from no EMS requests for service to all of them.

There should exist in the EMS system a careful balance of the type of ambulance response (ALS or BLS), rapidity of response (lights/sirens or not), and necessity of first response. The facilitation of such balance is often the job of the system’s medical director and is best determined based on patient outcome data from that system being weighed with the contractual obligations (if any) of the system and tempered by the inherent risks of over- and underresponse.


Once on scene, there are generally four possible outcomes. In most ­systems, anywhere between 20% and 30% of EMS calls result in no transport: Being cancelled on scene or prior to arrival; finding the patient dead on arrival or electing to terminate resuscitative efforts prior to transport; and having the patient refuse transport and/or treatment are the outcomes expected, resulting in no transport. For the majority of requests for service, however, the patient is transported to a destination to provide additional care. Most often, this destination is a local emergency department and that selection is often based on geography, patient preference, and continuity of care.7 In an ever-increasing number of circumstances, local protocol may dictate transport to a specialty care destination. Often emergency departments, these specialty care centers are able to provide advanced care in trauma, burn, stroke, pediatric, cardiac care, or other specialized disciplines. In some communities, the option exists to transport the patient to an alternative care site such as an urgent care center or community health clinic. Although an important destination for EMS during disasters, these alternative care sites are unique opportunities to create a parallel care track in the decidedly serial nature of the EMS system to move patients more efficiently through the health care system. There are challenges to this approach and a more detailed discussion can be found in Chapter 11.


Once at the destination, most commonly an emergency department, there are generally three outcomes. In some cases, the patient may be transferred from that ED to another hospital for specialty care or because of bed availability. Both of these outcomes may affect the EMS system as transfers almost universally result in the use of EMS resources, and in some cases, specialized resources and/or teams. If admitted to the hospital and subsequently discharged, this may be to home, a rehabilitation facility, or a long-term care facility. The latter two may also impact the EMS system as these patients are often transported by EMS due to their continued health care needs and/or inability to safely ambulate or transfer.

EMS system design must take into consideration not only the emergency requests for service, but also the nonemergency and interfacility transport requests. Efficiently utilizing limited and often costly resources in a linear and flow-constricted system is the challenge of EMS system managers, and the role of the EMS physician to ensure the system meets its primary mission of patient care should not be underestimated.



Prior to 1973, the components of an EMS system were as varied as the EMS systems themselves and consisted of transportation, not necessarily treatment. When published in 1966, Accidental Death and Disability: The Neglected Disease of Modern Society began focusing on the inadequacies of emergency care in general, and prehospital care in particular.8 In great part prompted by Accidental Death and Disability, and a demonstration project by the newly established Robert Wood Johnson Program, in 1973 Congress passed and President Nixon signed the EMS Systems Act.9

The Act called for a lead agency under the Department of Health, Education, and Welfare and identified 15 components to assist planners with the design of EMS systems stimulated by federal funding from this Act to over 300 regions nationwide. The original 15 components of the EMS Systems Act are included in Table 12-1 and notably lack concepts such as medical direction, financing, performance expectations, or a legal framework within which to operate.9 Although established to promote regionalization, the Act set into motion dozens of differently structured EMS systems that facilitated isolation, without planting the important seed of establishing initiatives to continually fund EMS at the local, regional, or even federal level.

TABLE 12-1

EMS Systems Act Components of System Design9

The EMS Systems Act did not put the patient at the center of the ­system, nor did it promote the importance of clinical care as the primary driver of system design. In essence, the Act merely promulgated the pre-1973 concept that EMS systems were merely specialized transportation systems. By the early 1990s, greater interest in the clinical care of patients led to the 1996 National Highway Transportation Administration’s release of the EMS Agenda for the Future.5 This document made an important contribution by outlining the following 14 essential components that form the basis for current system design10:

Integration of health care service: As a component of the health care ­system, the care interaction with EMS should not occur in isolation and should be integrated with other community health resources within the health care system.

EMS research: Research is essential to improve care and allocate resources by determining the efficacy, effectiveness, and efficiency of prehospital care.

Legislation and regulation: Affecting EMS funding, system design, provider credentialing and scope of practice, enabling legislation and its associated regulations significantly affect how all aspects of prehospital care are provided.

System finance: In order to continuously provide essential public safety services, EMS systems, whether public or private, must be financially viable and built upon a strong financial foundation.

Human resources: The most valuable asset to EMS patients, the human resource, must be composed of a dedicated team with complementary skills and expertise that provide qualified, competent, and compassionate care.

Medical direction: Involving the delegation of authority and acceptance of responsibility, medical direction ensures the standards of medical practice are upheld to ensure optimal care for patients.

Education systems: To meet the evolving standard of care, EMS education systems must meet the cognitive, psychomotor, and technological needs of new and seasoned EMS professionals.

Public education: The EMS system has a responsibility to foster health promotion.

Prevention: The EMS system has a responsibility to promote prevention activities that reduce human morbidity and mortality.

Public access: Prompt and appropriate EMS care must be provided regardless of socioeconomic status, age, or special need.

Communications: Robust systems that allow accurate and timely transfer of information are essential to system success.

Clinical care: Mobility and immediate availability to the entire population distinguishes EMS in its ability to provide medical care to those with perceived need and provide transport to, from, and between health care facilities.

Information systems: Collecting, transmitting, and analyzing valid, reliable, and accurate data are essential to system improvement and integration within the health care system.

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Jan 22, 2019 | Posted by in EMERGENCY MEDICINE | Comments Off on EMS System Design

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