Study objectives: To determine whether criteria based dispatch (CBD) improved the efficiency of the emergency medical services system.
Design: A before and after design was used to measure effects of CBD. Data were reviewed from medical reports from January 1986 through June 1992.
Setting: King County, Washington, excluding the city of Seattle.
Participants: Residents who called 911 to report a medical emergency.
Interventions: Emergency medical dispatching (EMD), basic life support (BLS), and advanced life support (ALS).
Results: Findings show a decrease in ALS responses for two tracer conditions that medical control physicians determined not require ALS intervention. The percentage of febrile seizures in which paramedics responded decreased from 41% to 21% (P < .001). The percentage of cerebrovascular accidents in which paramedics responded decreased from 41% to 28% (P < .001). CBD led to a decrease, from 4.7% to 3.8% (P < .001), in frequency of requests by BLS units for dispatch of ALS units. There was no increase in the time required to dispatch each call.
Conclusion: CBD increased the efficiency of the EMS system by significantly reducing ALS responses to incidents not requiring ALS intervention and reducing requests by BLS units for dispatch of ALS units while maintaining a consistent time from receipt of call to dispatch.