Study investigates EMS response times and mortality rates

Posted January 31, 2012

By Kathryn Sloniowski

If a medical emergency happens outside of a hospital, we rely on the rapid response of emergency medical services (EMS) to provide us with medical care and even to potentially save our lives. A common principle in modern EMS systems is that a faster response saves lives and many EMS systems have translated this into a policy of responding to 911 calls within eight minutes. New research from the University of Calgary’s Faculty of Medicine has investigated the clinical effectiveness of this goal.

In a study that looked at more than 7,500 life-threatening emergency calls, EMS was able to respond to patients within eight minutes, 76 per cent of the time. Of these patients, 6.4 per cent died. Of the patients who were responded to in more than eight minutes, 7.1 per cent died. This finding suggests there is little difference in mortality associated with an eight minute response time policy.

“In the study, we failed to detect a statistically significant difference in mortality between those patients that received a response time of less than eight minutes, versus those who were responded to in over eight minutes,” says Ian Blanchard, lead author of the study.

Blanchard says the study could not rule out that the observed difference in mortality rates occurred due to chance; however, it is important to note that the study does not suggest that a rapid response is not important for some patients. When the study team looked at patients who were admitted to the hospital, for example, there appeared to be a beneficial effect to an eight minute response time.

“It highlights the need for further research on this critical topic,” he says.

Maintaining an eight minute response time involves high speed driving on public roads with the use of lights and siren–all factors that could put both the public and EMS crews at risk of a vehicle collision. Blanchard says it is a balancing act to ensure that EMS arrives in a time affording the patient the best opportunity for survival while also minimizing the risk associated with getting to the scene quickly.

Dr. Christopher Doig, a critical care physician, is principle investigator of the study and head of the Department of Community Health Sciences at the Faculty of Medicine. He says the study addresses an important preliminary question regarding EMS response time and raises awareness of an important area of research requiring further attention.

“A health-care system can have world-class hospital facilities and staff, but if patients are not delivered in a condition that is amenable to survival, then the full potential of
in-hospital care will not be realized. In order to implement policies that minimize the risk for the public and EMS providers and to maximize the potential for survival of patients, more research needs to be done,” he says.

The study, which is published in this month’s issue of Prehospital Emergency Care, looked at adult patients in Calgary who were identified as being in a life threatening condition and subsequently received a high-priority EMS response between Jan. 1, 2006 and Dec. 31, 2006. The response time is defined as the time between when a 911 call is received until the arrival of the first ambulance on the scene.