Electronic Thesis/Dissertation


Improving Critical Patient Outcomes through Geospatial Optimization of Paramedic Ambulance Locations Open Access

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Ambulance response time is a paramount factor contributing to patient outcomes of critical medical emergencies, particularly cardiac emergencies. In Ventura County, California, we established that over an 11-year period there was no significant difference in ambulance response time between critical medical emergencies and other medical emergencies. The objective of our research was to show response times to critical medical emergencies, which in Ventura County are primarily cardiac emergencies, could be improved through the optimization of ambulance staging and stationing locations. Incident location data was analyzed to optimize ambulance locations using the Ventura County road network dataset and various geospatial analytical tools available from the Environmental Systems Research Institute (ESRI), including ArcMap and ArcGIS Pro software. Using the Google Distance Matrix Service (GDMS) we showed response times from our optimized locations would be, on average, 134 seconds faster the historical response times. We showed that using optimized ambulance locations could achieve a 43 percent improvement meeting Ventura County Emergency Medical Service (EMS) Agency’s 8-minute response time ambulance contract metric. Accounting for the other time periods involved in the response process, we translated response time into time-from-first-ring at the public safety answering point (PSAP) to time-at-patient-side. To infer improvement of critical patient outcomes, we cited research that found a 134 second decrease in response time correlates to a 17 percent increase in the probability a cardiac patient will survive one day, and a 38 percent increase in the likelihood a cardiac patient will survive 90 days. These response time improvements were achieved to the detriment of non-critical medical emergency response times. Additionally, we showed optimized ambulance locations achieve a 60 percent improvement (15,315 versus 9,587 incidents) meeting the 8-minute total response time (time-of-first-ring to time-at-patient-side) goal for defibrillation of patients in cardiac arrest. Furthermore, if responding from an optimized location, we predicted the probability a paramedic will arrive at patient-side within 8-minutes (from time-of-first-ring to time-at patient-side) increases by 36 percent.

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