Background: Helicopter emergency medical services (HEMS) have demonstrated survival benefits over ground emergency medical services (GEMS) for trauma patient transport. While HEMS speed is often-cited, factors such as provider experience and level of care may also play a role. Our objective was to identify patient groups that may benefit from HEMS even when prehospital time for helicopter utilization is longer than GEMS transport.
Methods: Adult patients transported by HEMS or GEMS from the scene of injury in the Pennsylvania State Trauma Registry were included. Propensity score matching was used to match HEMS and GEMS patients for likelihood of HEMS, keeping only pairs in which the HEMS patient had longer total prehospital time than the matched GEMS patient. Mixed-effects logistic regression evaluated the effect of transport mode on survival while controlling for demographics, admission physiology, transfusions, and procedures. Interaction testing between transport mode and existing trauma triage criteria was conducted and models stratified across significant interactions to determine which criteria identify patients with a significant survival benefit when transported by HEMS even when slower than GEMS.
Results: From 153,729 eligible patients, 8,307 pairs were matched. Helicopter emergency medical services total prehospital time was a median of 13 minutes (interquartile range, 6-22) longer than GEMS. Patients with abnormal respiratory rate (odds ratio [OR], 2.39; 95% confidence interval [CI], 1.26-4.55; p = 0.01), Glasgow Coma Scale score of 8 or less (OR, 1.61; 95% CI, 1.16-2.22; p < 0.01), and hemo/pneumothorax (OR, 2.25; 95% CI, 1.06-4.78; p = 0.03) had a significant survival advantage when transported by HEMS even with longer prehospital time than GEMS. Conversely, there was no association between transport mode and survival in patients without these factors (p > 0.05).
Conclusion: Patients with abnormal respiratory rate, Glasgow Coma Scale score of 8 or less, and hemo/pneumothorax benefit from HEMS transport even when GEMS transport was faster. This may indicate that these patients benefit primarily from HEMS care, such as advanced airway and chest trauma management, rather than simply faster transport to a trauma center.
Level of evidence: Therapeutic, level III.