Impact of the emergency medical services crew size (2 vs. ≥3 personnel) on prehospital performance and survival in severe trauma: a nationwide cohort study in Korea

PURPOSE: Timely and coordinated prehospital interventions are critical to improving outcomes in patients with severe trauma. In Korea, national discussions are underway to expand emergency medical services (EMS) crews from the standard two-person configuration to three, yet nationwide evidence supporting this policy remains limited. This study aimed to evaluate whether EMS crew size (2 vs. ≥3 personnel) is associated with differences in prehospital care performance and survival outcomes among patients with severe trauma, accounting for potential confounding factors, including the COVID-19 period. METHODS: We conducted a retrospective cohort analysis of EMS dispatches linked with trauma registry data in Korea from January 2018 to December 2023. Adults (≥18 years) with field-classified severe trauma were included. The main exposure was EMS crew size. Primary outcomes were scene time ≤10 minutes, advanced airway management among unresponsive patients, and intravenous (IV) access in hypotensive patients (systolic blood pressure ≤90 mmHg). The secondary outcome was survival to hospital discharge. Multivariable logistic regression analyses were performed, and results adjusted for potential confounders are reported. RESULTS: Among 78,203 severe trauma patients, 47,594 (60.9%) were treated by ≥3-person crews. After adjustment, larger crews were significantly associated with improved IV access (adjusted odds ratio [aOR], 1.47; 95% confidence interval [CI], 1.31-1.66) and higher odds of achieving on-scene time ≤10 minutes (aOR, 1.09; 95% CI, 1.05-1.13). Advanced airway management also demonstrated borderline statistical significance (aOR, 1.13; 95% CI, 1.00-1.28). Overall survival to hospital discharge was 89.0%. Although survival was slightly higher in the two-person group (89.7% vs. 88.5%, P<0.01), the difference was not significant after adjustment (aOR, 1.00; 95% CI, 0.94-1.05). CONCLUSIONS: EMS crews of ≥3 members demonstrated improved procedural performance in severe trauma, but no significant survival advantage. System-level investments and further outcome-based research are warranted to optimize crew configurations and resource allocation.