The impact of ambulance diversion on EMS resource availability.
OBJECTIVE
Ambulance diversion has been proposed as a solution to emergency department overcrowding and waiting room deaths. For ethical and legal reasons, it remains highly controversial. The impact on EMS resources is not known. This study seeks to determine how diversion impacts the availability of ambulance resources, specifically transport time, hospital turnaround, and total out-of-service time.


METHODS
All emergency ambulance responses in 2002 while one of the city's hospitals was on diversion were collected, including those responses during the hour of the diversion and 30 minutes before and after. The time intervals for these responses were time and date matched to 2001, if no hospital was on diversion. Total out-of-service time (911 to availability for another call), time from departure from scene to arrival at hospital (transport interval), and time from arrival at hospital to availability for another call (turnaround time) were compared by using a t-test.


RESULTS
The 1,563 instances of diversion were included, with 1,403 controls. Interim analysis allowed calculation of a sample size of 1,049 in each group to show a 2-minute difference in turnaround time and 330 calls in each for a 5-minute difference in total out-of-service time (0.25 SD). Transport, hospital turnaround, and total out-of-service times were not different between diversion and control time periods. This relies on the accuracy of the status button system and may not generalize to systems with different geography, diversion policy, number of hospitals, or handling of interfacility transfers.


CONCLUSIONS
The availability of EMS resources is maintained during times of ambulance diversion. Diversion avoids potential delays associated with sending ambulances to overwhelmed emergency departments.
Carter
Alix J E
AJ
University of Manitoba Section of Emergency Medicine, Winnipeg, Canada. Alix.carter@yale.edu
Grierson
Robert
R
D000552:Ambulances / Q000458:organization & administration* / Q000600:supply & distribution; D003441:Crowding; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D006801:Humans; D010360:Patient Transfer; D012189:Retrospective Studies; D014481:United States