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Introduction

The use of technology to support emergency medical services (EMS) care has grown substantially, including mobile applications that provide real-time access to protocols, policies, and clinical decision support in the field. Despite this evolution from paper-based to dynamic software-based tools, data on EMS clinician adoption and longitudinal use of these applications remain limited. The Los Angeles (LA) County EMS Agency developed the mobile application ‘RAPID LAC Medic’ to provide immediate access to treatment protocols, just-in-time training videos, and clinical decision-making support tools for EMS clinicians and hospital-based nurses and physicians providing online medical direction with the regional EMS system. Our objective was to characterize the timing and patterns of initial uptake and to quantify longitudinal user engagement with the mobile application.

Methods

LA County has a regional, fire-based EMS system with over 4500 paramedics and approximately 800,000 EMS responses annually. Online medical direction is provided at 21 Base hospitals. We conducted a retrospective analysis of one year of use data from the RAPID LAC Medic mobile application within the LA County EMS system after its implementation in January 2025. The mobile application tracks data on the specific content accessed, the date of access, and the geographic coordinates at the time of access (if location sharing is enabled by the user). It assigns an anonymized identifier to each device. All paramedics and online medical clinicians working in LA County received mandatory training on the application, which was conducted from April 1 to June 30, 2025. We analyzed data for the entire year of 2025. Our primary outcomes were monthly new device activations, number of active devices, and the frequency of page views by specific content. We used the geographic coordinates to spatially attribute use to fire stations, EMS service areas, and Base hospitals using defined proximity buffers. We quantified the frequency of mobile application use related to EMS patient care encounters. To improve specificity, we applied DBSCAN to identify density-based spatial clusters and censored those unlikely to represent patient care encounters (e.g., high volume of use at paramedic schools and fire department headquarters). We also performed sensitivity analyses to normalize use trends and account for fluctuations in EMS call volumes.

Results

A total of 7,855 active devices generated 628,667 page views during the one year study period. New device activations peaked in April 2025 at the beginning of the annual systemwide education period and gradually declined through December 2025. The number of active devices peaked in June 2025, followed by a decline in use at fire stations and in EMS service areas, while use was sustained at Base hospitals. Treatment protocols were the most commonly accessed content (73% of all page views). Location data were available for 365,646 page views (58%). After exclusion of page views in location clusters identified as unrelated to patient care, we attributed 88,198 page views (37%) to fire stations, 98,880 (42%) to EMS service areas, and 49,029 (21%) to Base hospitals providing online medical direction. Weekly page views peaked in July 2025 overall. After the training period, there was a gradual decline in use at fire stations. Use in EMS service areas and Base hospitals was sustained through the year, and this was confirmed after normalization of use by EMS call volume.

Conclusions

We observed sustained use of a new mobile application to support EMS patient care in the one year following implementation. While limited to a single fire-based EMS system, these findings suggest that software-based tools to provide EMS clinicians real-time access to treatment protocols, policies and clinical decision support can achieve meaningful adoption and sustained use within EMS systems.