MEASURING RESPONSE INTERVALS IN A SYSTEM WITH A 911 PRIMARY AND AN EMERGENCY MEDICAL-SERVICES SECONDARY PUBLIC SAFETY ANSWERING POINT

Study objective: Measurement of interval data is important in the accu rate recording of events that occur in an emergency medical services s ystem. Measurement of intervals should be a simple task. However, when two separate clocks are needed to record the beginning and end of an interval, accurate measurement may be difficult. We sought to accurate ly measure the 911 call receipt-to-vehicle departure and 911 call rece ipt-to-patient access intervals in a system with primary and secondary public safety answering points (PSAPs). Methods: We conducted a descr iptive study between January 1 and July 31, 1993. All 911 calls beginn ing at the primary PSAP, transferred to the EMS secondary PSAP, and en ding with patient access times were eligible. Clock-synchronization er rors and unavailability of 911 time logs were the criteria for exclusi on. We measured the 911 call receipt-to-vehicle departure interval by adding the primary-PSAP and the EMS secondary-PSAP call-processing int ervals. The 911 call receipt-to-patient access interval was the absolu te difference between the time when the 911 primary-PSAP phone rang an d the time of patient access recorded by EMS personnel. Results: The d ata were best described with median and interquartile ranges (IQRs). W e found 1,945 calls that met inclusion criteria. Of these, 270 were de leted because of clock errors and 616 for time log unavailability, yie lding 1,059 calls for interval determinations. The median 911 call rec eipt-to-vehicle departure interval was 1.7 minutes (IQR, 1.2 to 2.2 mi nutes). The median 911 call receipt-to-patient access interval was 8.2 minutes (IQR, 6.4 to 10.5 minutes). Conclusion: The 911 call receipt- to-vehicle departure and 911 call receipt-to-patient access intervals can be accurately measured in a system with two separate PSAP computer -aided dispatch clocks. These intervals are variable and often lengthy .