An analysis of a single helicopter emergency medical service (HEMS) in South East England found 30-day survival among major trauma patients was higher than predicted by standard risk models, equivalent to about five additional survivors per 100 patients treated. The study, published online in the Emergency Medicine Journal, also reported improving rates of return of spontaneous circulation in traumatic cardiac arrest over the 2013–2022 period, while cautioning the findings do not prove the helicopter service caused the better outcomes.
Researchers reviewed outcomes for 3,225 trauma patients who received pre-hospital care from one HEMS team operating across Kent, Surrey and Sussex between 2013 and 2022.
Using a modelling approach known as Ws analysis to compare observed survival with model-predicted survival (adjusting for differences in injury severity and patient characteristics), the study reported that 2,125 patients survived at least 30 days after injury—an observed 30-day survival rate of 85%, compared with an expected rate of 81%.
The authors said the difference amounted to roughly five additional survivors per 100 patients treated, and estimated this could be equivalent to as many as 115 additional lives saved per year, based on the service’s usual caseload.
The analysis suggested the largest gains were among patients with severe injuries and a moderate predicted survival probability (25%–45%): in that group, 35% were reported to survive to 30 days. Survival was also described as higher than predicted among patients with a low predicted chance of survival (below 50%).
The researchers also examined traumatic cardiac arrest—when the heart stops after severe injury such as major bleeding or chest trauma. Among 1,316 such patients, 356 (27%) were reported to achieve sustained return of spontaneous circulation while being transported to hospital, while 960 were pronounced dead at the scene. Among those with sustained circulation, 30-day survival status was available for 185 patients, and 46 (25%) of those were reported to be alive at 30 days.
Across the 2013–2022 study period, the team reported that the probability of return of spontaneous circulation increased by about 6% per year.
The researchers said factors associated with unexpected survival included younger age, being more responsive at initial assessment (commonly measured using the Glasgow Coma Scale, scored from 3 to 15), and receipt of pre-hospital emergency anaesthesia, which they described as placing a trauma patient into an induced coma and as an intervention that can be delivered only by advanced care teams such as HEMS.
In their conclusions, the authors cautioned that the results reflect excess survival relative to statistical predictions, and do not establish a causal effect of helicopter care. They noted that some estimates assume consistent case-mix and service performance over time, which may not always hold. The team concluded that the findings offer supportive evidence for continued investment in HEMS for severely injured patients, while calling for comparative research against alternative care pathways to better establish causal effectiveness.
