Emergency medical service agency definitions of response intervals

Ann Emerg Med. 1999 Oct;34(4 Pt 1):453-8. doi: 10.1016/s0196-0644(99)80046-8.


Study objective: There is a time continuum from emergency medical services (EMS) dispatch, response, scene, transport, and arrival at the hospital. Previous research has documented favorable patient outcome with short response intervals; however, these studies revealed the documentation of EMS time intervals is not always consistent. This study evaluates how agencies estimate these times and factors that may affect the length of response intervals.

Methods: The study used a mail questionnaire to assess factors related to response intervals and to determine how agencies define and record response intervals. All ground-based EMS agencies in a southwestern state were invited to participate in the survey. Univariate and stratified data analyses compared definitions of response intervals.

Results: Agencies varied as to how they defined the start and end of the response. Fifty-six percent stated that their response started when the responding unit was notified of the call. However, almost 23% defined response interval as starting when dispatch received the call, and 11% defined it as starting with the initial 911 call. A factor that affected response intervals was routing of the 911 call. Less than 6% of agencies had only 1-call routing.

Conclusion: Agencies use different time points as the start and end of their response interval, which makes comparison of results directly related to response intervals across agencies or regions difficult. To maintain an appropriate standard of prehospital emergency medical care throughout the state, the use of consistent standard terminology defining response intervals will help reach that goal.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Emergency Medical Services / statistics & numerical data*
  • Evaluation Studies as Topic
  • Humans
  • Time and Motion Studies*
  • United States