Emergency medical service agency definitions of response intervals

Study objective: There is a time continuum from emergency medical services (EMS) dispatch, response, scene, transport, and arrival at the hospital. Pr evious research has documented favorable patient outcome with short respons e intervals; however, these studies revealed the documentation of EMS time intervals is not always consistent. This study evaluates how agencies estim ate these times and factors that may affect the length of response interval s. Methods: The study used a mail questionnaire to assess factors related to r esponse intervals and to determine how agencies define and record response intervals. All ground-based EMS agencies in a southwestern state were invit ed to participate in the survey. Univariate and stratified data analyses co mpared definitions of response intervals. Results: Agencies varied as to how they defined the start and end of the re sponse. Fifty-six percent stated that their response started when the respo nding unit was notified of the call. However, almost 23% defined response i nterval as starting when dispatch received the call, and 11% defined it as starting with the initial 911 call. A factor that affected response interva ls was routing of the 911 call. Less than 6% of agencies had only 1-call ro uting. Conclusion: Agencies use different time points as the start and end of thei r response interval, which makes comparison of results directly related to response intervals across agencies or regions difficult. To maintain an app ropriate standard of prehospital emergency medical care throughout the stat e, the use of consistent standard terminology defining response intervals w ill help reach that goal.