Evaluating Emergency Medical Service Provider Perceptions About Patient Acuity Across Various Transport Vehicles

EMS clinicians respond to calls in multiple types of vehicles, including ground ambulances, fixed-wing air ambulances, and rotor-wing air ambulances. Each type of vehicle serves a specific role within the overall EMS system and, based on differences in capabilities and operating costs, likely responds to patients with different clinical needs and acuities. For example, rotor-wing air ambulances are often utilized to transport high-acuity patients significant distances in less time than a ground ambulance and are staffed with highly-trained providers. To better understand the correlation between EMS vehicle type and patient acuity, we examined the National Emergency Medical Services Information System (NEMSIS) database to identify what percentage of calls involve high-acuity, medium-acuity, and low-acuity patients within three EMS vehicle types. Acuity was determined by provider impression. Of the 53,193,098 calls that were included for analysis, 99.14% involved ground ambulances, 0.75% involved rotor-wing air ambulances, and 0.11% involved fixed-wing air ambulances. Rotor-wing air ambulances received the greatest share of high-acuity patients (47.60%), followed by fixed-wing air ambulances (30.15%) and ground ambulances (3.85%). This trend was reversed for low-acuity patients: ground ambulances responded to the highest percentage of low-acuity patients (72.70%), followed by fixed-wing air ambulances (10.69%) and rotor-wing air ambulances (4.47%). These data suggest that air ambulances - both fixed-wing and rotor-wing - mostly respond to patients that providers determine to be medium-acuity or high-acuity, while a majority of calls ground ambulances respond to involve patients determined to be low-acuity. The fact that aeromedical EMS resources are predominantly being used for medium- and high-acuity patients is reassuring, because it suggests they are being effectively deployed. Further research should examine how EMS providers determine patient acuity and see if the trends we identified remain constant or fluctuate.