Agency-Level Factors Associated with EMS Volume for High-impact Clinical Conditions and Patient Populations.

Background: Emergency medical services (EMS) agencies play a crucial role in delivering prehospital care, yet significant variability exists in EMS call volume and the conditions encountered. Variation in EMS call volume across agencies (i.e., high- vs. low-frequency) for specific patient populations and clinical presentations across EMS agencies can have substantial impact on implementation strategies for new guidelines and performance measures. We sought to evaluate agency-level factors associated with EMS volume of specific clinical presentations to inform the planning of targeted quality improvement efforts and resource allocation related to specific high-impact clinical categories.

Methods: We conducted a retrospective analysis of the 2022 and 2023 National EMS Information System datasets, identifying EMS agencies that consistently reported patient encounters over a two-year period. We categorized encounters by key patient populations and clinical presentations, including cardiac arrest, trauma, stroke, pediatric cases, advanced airway management, and non-transport disposition. We used negative binomial regression to assess factors associated with EMS volumes.

Results: We included 7,230 EMS agencies, with 55,705,469 encounters. The median number of encounters by EMS agency was 1,988 encounters averaged per year (IQR 706-5,584 encounters averaged per year). Cardiac arrest was more frequent in mixed/volunteer agencies and less common in for-profit, non-hospital, and tribal-based EMS services. Trauma volume was higher in advanced life support (ALS) and critical care agencies, the West (relative to Midwest), and mixed/volunteer agencies (relative to non-volunteer agencies). Stroke volume was linked to greater ALS/critical care agencies and mixed/volunteer agencies but was lower in urban areas. Pediatric encounters were more common in urban, mixed/volunteer agencies, and tribal services but less frequent in for-profit and hospital-based agencies. Airway interventions were associated with ALS/critical care agencies, but were less frequent in tribal agencies. Non-transport occurred more commonly in ALS agencies and tribal agencies.

Conclusions: Distinct patterns of agency-level characteristics appear to exist in relation to the volume of EMS responses for specific patient populations and clinical presentations. These findings can inform agency-specific strategic planning for guideline implementation, resource allocation, and quality improvement in prehospital care.