Emergency medical services (EMS) systems were developed in the early 1970s when federal resources were made available to provide for creation of the prehospital system infrastructure.¹ A few years following the development of the EMS systems, NHTSA with the assistance from NASEMSD (National Association of State EMS Directors) developed a two-tiered statewide communication plan which was adapted to satisfy communication needs within EMS systems while also providing for compatibility and interoperability with other EMS components.² Although the need for creating a communication infrastructure was recognized early and the system-level elements are well understood by the planning committee members, the various components of EMS communications are less understood by providers of emergency care systems. The common misconception related to emergency communication is that it is thought to involve exchange of information for medical control purposes when in fact, the actual process includes any exchange of the information between providers or between providers and the public or between emergency care providers and public safety agencies.

• 
  

  Describe the usual events involved in the dispatching of an EMS agency for an emergency call.

  
  
• 
  

  Describe modes of response related to dispatching.

  
  
• 
  

  Describe computer-assisted dispatching.

  
  
• 
  

  Describe the common types of radio communication and frequencies.

  
  
• 
  

  Describe common types of “radio speak,” including signals, codes, and plain speak.

  
  
• 
  

  Discuss why plain profession radio speak is considered superior to signals and codes.

  
  
• 
  

  Describe common terms used in radio communication to communicate the status of a unit.

  
  
• 
  

  Describe an emergency department base station and list types of ­individuals who may be answering the call.

  
  
• 
  

  Describe the types of “calls” that EMS providers make to the EMS base station.

  
  
• 
  

  Detail the essential components of base-station training.

  
  
• 
  

  Describe alternatives to radio for communications.

  
  
• 
  

  Discuss new technology, including the transmission of ECGs, real-time telemetry, and video streaming from the field.

Until fairly recently, there was no a comprehensive network of emergency communication centers, even in the United States. The evolution of the existence of “9-1-1” centers has led to a convenient and ­accessible way for the public to call for emergency assistance. There are a few ­components of the communication chain that illustrates how this system functions (Figure 15-1).

INITIAL CALL FROM PUBLIC, LANDLINE, CELL PHONE, VOIP

Emergency services are an important element of health care system and immediate, reliable, and easy access to this system is provided to the community through activation of 9-1-1 system. Common ways of accessing this system include the landline phones, mobile phones, ­vehicle-based access using automatic crash notification (ACN), and commercial voice-over-Internet protocol (VoIP) service, which refers to communication using the Internet rather than the public switched telephone network providers. ACN is a system that alerts EMS systems when a crash occurs and information obtained using this system helps determine severity and location of the collision as well as notify and create a communication link with EMS providers and the crash victim.³ Once emergency care systems are activated through any of these pathways, the system recognizes the need for the emergency service, leading to identification of the caller/communication device, dispatch to the site of event, and transport to an appropriate or closest emergency care facility.

ROLE OF PUBLIC SERVICE ANSWERING POINTS (FUNCTION OF ALI/ANI INFORMATION AND LOCATION VIA CELL TOWERS)

9-1-1 call centers or public service answering points (PSAPs) are the first line of contact for the public with the emergency care systems (Figure 15-2). PSAPs can be integrated with the dispatch center or be an autonomous agency established to receive calls. They are of four types and are designated as direct if the field teams are directly dispatched by the agency after the call is received and interrogated by the PSAP. The other types include centers which transfer the call to the agency to allow direct communication between the dispatching agency and the caller (secondary PSAP) or a relay model in which the information is collected by the PSAP and is given to the dispatching agency which does not directly communicate with the caller. Referral models are the least recommended approach in which the information is taken from the caller who is then given the appropriate number to call the emergency medical dispatcher: The next element in the communication chain is the emergency medical dispatch center. Emergency medical dispatchers are personnel with skill in basic telecommunications who serve as a link between the public and the field teams. They receive the information from the public, monitor the field teams, as well as direct and dispatch them to the scene. Enhanced features of the 9-1-1 system used to contact PSAPs/dispatch center are able to selectively route the call to the center based on the caller location and also display of the caller phone number (automatic number identification) and location (automatic location identification) in the dispatch screen.³ These features significantly improve the reliability of response even when the caller is unable to provide information on their location. The various modes of communication available for EMDs include one-way paging or “alert dispatching” which helps simultaneously communicate with many units or communicate with field providers and other public safety agencies (law, enforcement, fire) during mass casualty incidents, using radio systems. Other methods of communication may involve direct telephone communication with other public safety agencies and/or the medical facilities.

MEDICAL CONTROL COMMUNICATION

Another important component of the communication chain includes medical providers in the hospitals. The teams providing care on scene need to communicate with the receiving hospital for notification of the time of arrival, patient medical condition, and transmission of data such as ECG or telemetry.

INTERAGENCY COMMUNICATION

This involves communication using radio equipment with other ­public safety agencies. This link involves local coordination using mobile and portable radios with multiple mutual aid responding units and/or regional coordination in disaster situations that require large-scale coordination between EMS resources as well as communication with public safety agencies as determined by on-scene needs of the responding unit.

BACK-UP COMMUNICATION

This involves a mechanism for communication between medical control, dispatch, and interagency coordination in the event of outages of primary dispatch, base hospital or during disaster scenarios.⁴

Communication Equipment

The exchange of information between the different components of the communication network is facilitated using a basic unit consisting of transmitter and receiver units. The radio communication equipment which is used in one-way communication such as paging or alerts involve a receiver and transmitter unit tuned to the same frequency within the radio range of each other. For two-way communication, a receiver and transmitter is usually placed at both sites. A simplex communication involves one frequency channel for communication and involves transfer of information both ways by provider taking turns on a single frequency channel (Figure 15-3). By using two different frequencies it is possible for the providers to interrupt each other during a communication in a duplex system. A duplex communication system can also be modified to have a duplex setup at one end and a simplex at the other end. This provides for the physician to interrupt the field provider communication during patient care to provide medical direction whereas a field provider would not be able to break a physician communication. A duplex system designed to automatically retransmit what is relayed is called a mobile relay system, for example, an incoming information on frequency 1 from a mobile unit is automatically connected and relayed to another mobile unit or ambulance on frequency 2.⁵

EMERGENCY MEDICAL RADIO SERVICE FREQUENCIES FOR PROVIDER COMMUNICATION

In 1993, Under the Federal Communication Commission (FCC) established the emergency medical radio service (EMRS). This public safety radio service (PSRS) was created to improve the reliability of communications in an emergency setting by providing specific frequencies to life support–related communication. Advanced and basic life support providers were eligible to use these channels of communication when providing basic or advanced life support services.⁶

EMRS frequencies available for EMS communications are in the VHF “high band” (150-173 MHz), the UHF “ultrahigh frequency” band (453-465 MHz), the 220-MHz band, and the 800-MHz band (Table 15-1). Also, while no 800-MHz band frequencies are allocated to EMS, all EMRS eligible entities are allowed to license 800-MHz frequencies allocated for public safety agencies and also use SERS (specialized emergency radio service) channels for essential nonemergency communication with other entities.

800-MHz PUBLIC SAFETY SPECTRUM

Radio systems used by public safety officers, that is, police, firefighters, and emergency medical technicians operate in multiple sections of the 800-MHz band which consists of spectrum at 806 to 824 MHz paired with spectrum at 851-869 MHz.⁶ Under guidelines provided by the National Public Safety Planning Advisory Committee (NPSPAC), a 6-MHz spectrum in this band has been provided for exclusive use of public safety agencies. However, since the 800-MHz band is also used by commercial wireless carriers and private radio systems, FCC reconfigured the band plan in 2004 to separate the commercial users from the public safety agencies using cellular architecture. However, some of the problems faced by providers and agencies include the lack of compatibility between service areas due to differences in architecture of the communication equipment, not being able to use vehicle repeaters limiting communication within closed settings like homes and limited frequency range limiting communication particularly in rural regions.⁷

VHF RADIO SYSTEMS

Rural and suburban agencies use the VHF radio systems due to the properties of the radio waves that are suited for the flat terrain of the rural areas. VHF systems are simplex and have a range of 15 miles without repeaters, for communication. Repeaters receive signals on one frequency and retransmit on the other frequency and can overcome problems with range limitations and distance but are not permitted for use by EMS systems in the low frequency range, by FCC.⁸

UHF RADIO SYSTEMS

Urban systems use the UHF radio systems that have the properties for use in heavily population regions. Unlike the VHF systems, UHF ­systems are usually duplex systems and have 10 channels dedicated by FCC for use by the EMS agencies. When using UHF radio systems, EMS agencies can also use special features such as squelch which limit the communication from being shared by other agencies.

OTHER METHODS OF COMMUNICATION

Trunking

Trunking technology creates a dedicated communication line between two sites and uses a small number of trunks for a large number of users. This method of communication is based on the probability that not all users will simultaneously use the trunk lines. The major advantage of this system includes the availability of open channels, secure connection, and lack of interference while some of the problems related to this technology include the cost of the infrastructure, dependence on the computer infrastructure, and automated call switching.⁹

Microwave Relays

Microwave relays work by converting radio frequencies into telephone/microwave frequencies and back to radio ­frequencies on the receiving end and extend the range of communication manyfold. Microwave systems can accommodate state and local emergency services radio systems and also systems used by nonemergency responders such as highway maintenance crews.⁸

2.4- to 5.9-GHz Systems and Fiberoptic Connections