patient and caller from potential hazards, and to protect the patient from well-meaning bystanders who could provide assistance that might do more harm than good (Hauert, 1990). The level of prearrival assistance from the dispatcher can vary from simple advice, such as “call a doctor,” to instructions for performing CPR. Instructions are typically available to the dispatcher on flip cards.
A survey of EMS systems conducted in 2003 by NASEMSD and HRSA’s Office of Rural Health Policy indicated that there were 15,691 credentialed EMS systems in the United States (Mears, 2004). However, the survey also indicated that the definition of an EMS system varies from state to state, making accurate tabulations nearly impossible. Among the systems identified by the survey, 45 percent were fire department–based, 6.5 percent were hospital-based, and 48.5 percent were labeled as neither (see Figure 2-4). The total number of ALS and BLS transport vehicles reported was 24,570. More recent data from the American Ambulance Association (AAA) indicate that there are 12,254 ambulance services operating in the United States (a figure that includes private for-profit and not-for-profit, hospital-based, volunteer, and fire department–based services), and a total of 23,575 ground ambulance vehicles (AAA, 2006).
While no statistics are available to provide greater detail about EMS system types nationwide, the Journal of Emergency Medical Services conducts an annual survey of the 200 largest metropolitan areas in the United