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

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.

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.

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.

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.