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Comprehensive Assessment of Emergency Medical Services 81 <br />and 911 /Communications Center Operations Study <br />Average vs. Fractile Response Time Performance Criteria <br />It is has been a common practice in the past to report response times by using averages. This is an easy - <br />to- understand methodology that calculates response times by adding all individual call response times <br />together and then dividing the total number of minutes by the total number of responses to come up <br />with an average. <br />Unfortunately, measuring and reporting average response times is inadvisable because one -half of the <br />patients may receive the required response time, while the other half will not. Given what has been <br />discussed about the need for an eight- minute response to maximize survivability from cardiac arrest, an <br />average eight- minute response, by definition, means that one -half, or more, of the service's patients are <br />not reached within that critical time. <br />Many high - performance emergency ambulance services use a different methodology to measure <br />response times to ensure service equality to all patients: fractile distribution; in most instances as <br />suggested by NFPA and others, reported at the 90`" percentile. <br />This methodology places each response within the minute it is achieved and stacks the minutes in <br />ascending order to establish a fractile response -time distribution. The point at which the fractile <br />response time crosses the percentile measures the point of the service's response -time reliability. <br />For example; the current Orange County EMS response time objectives, as published in the Orange <br />County EMS System Plan on file with the State Office of EMS, states that: <br />For Emergency Responses; <br />..... A Paramedic be on scene within 12 minutes 90% of the time <br />For Non - Emergency Responses; <br />..... A Paramedic be on scene within 15 minutes 90% of the time <br />Figure 26 <br />Annual Average Response Time - Emergency vs. Non-Emergency-All Calls 2009 -2011 <br />90% Fractile Times - Emergency vs. Non-Emergency-All Calls 2011 <br />0:12:23 - -- r----------- r----- - - - - - - - <br />0:12:0b ----------------------------------------------- ai , 90% @22 Minutes <br />0:11:48 ------- - - - - -- --- s - - - -- <br />- 0:11:30 <br />'------------------------------ <br />0:10:57 <br />-------- -� -- --------- <br />O:1Q:37 : 90% @18 Minutes <br />0:10:39 - - -- - - - -' -- Q �- <br />0:10:22 o:1p:15 <br />0:10:05-----------'----------- L----------- 1---------- - - - - -- - -. .. -- ' <br />0:09:48 .............................. ------------ ------------ <br />0 :04:34 -- -- - -- -1 --- 1 - - -- - - - - <br />- - - - - - - - - --- - - - - -- - - -- --- -- - - - - -- -- - - - - -- <br />0:09:13 <br />2009 2010 <br />+Emergency +N on- Emerge ncy <br />Solutions for Local Government, Inc. 37 <br />