Background Survival benefit of Helicopter Emergency Medical Services (HEMS) attended major trauma remains inadequately quantified across injury severity. We evaluated HEMS performance and identified predictors of survival. Methods Retrospective observational analysis of 3225 trauma patients attended by a regional HEMS in South-East England (2013–2022). Survival was assessed using W-statistic ( W s ) methodology stratified by probability of survival ( P s ) bands. Multivariable logistic regression identified predictors of 30-day mortality in major trauma (injury severity score (ISS) ≥15). Sub-analysis examined unexpected survival predictors and return of spontaneous circulation (ROSC) rates in traumatic cardiac arrest (TCA). Results Among 2125 patients meeting W s analysis criteria, observed (O) 30-day survival exceeded expected (E) survival (84.7% vs 81.3%; O/E ratio 1.04), yielding adjusted W s of 5.23 (95% CI 3.27 to 7.19), representing 5.23 excess survivors per 100 patients. Survival benefit was greatest in severely injured patients with moderate survival probability ( P s 25–45%: 3.33 excess survivors per 100, 95% CI 1.37 to 5.29). Among patients with low probability of survival ( P s <50), 38.7% survived unexpectedly; younger ages and higher presenting Glasgow Coma Scale scores were key predictors of unexpected survival. Pre-hospital emergency anaesthesia (PHEA) was independently associated with unexpected survival in this group (adjusted OR 2.01, 95% CI 1.12 to 3.72, p=0.023). TCA ROSC rates demonstrated an annual improvement (6.3% increased odds per year, 95% CI 1.02 to 1.10, p=0.002). Conclusion HEMS attendance to major trauma in this regional service was associated with survival exceeding case-mix adjusted predictions, and was most pronounced in severely injured patients. PHEA was associated with survival benefit in low probability patients, supporting the value of advanced pre-hospital interventions.
Griggs et al. (2026) studied this question.