Helicopter emergency medical service in out-of-hospital cardiac arrest - a10-year population-based study

Background: In 1988, Norway established a countrywide, physician staffed he licopter emergency medical service (HEMS). The medical benefit remains cont roversial. The aim of this study was to estimate the population incidence o f HEMS involvement in out-of-hospital cardiac arrest, report the patient ou tcome and evaluate the contribution of HEMS to survival. Methods: We studied HEMS operations in central Norway (population 364 000) during a 10-year period (1988-1997). Missions were classified according to type and quality of intervention done by the primary care providers. HEMS w itnessed cardiac arrests were not considered. Patient outcome was determine d as survival to hospital discharge with cerebral performance category (CPC ) score. The contribution made by HEMS in each survivor was assessed from t he timing of return of spontaneous circulation (ROSC) and from subsequent n eed for advanced medical intervention. The relation between survival and HE MS response time was investigated by ordinal correlation. Results: A total of 541 requests (14.9 per 100 000 inhabitants per year) we re identified, of which 424 missions were completed. population survival in cidence of 1 per 100 000 per year. Ninety-five percent of survivors made a favourable cerebral outcome (CPC 1 or 2). General practitioners/ambulance p ersonnel resuscitated 29 out of 36 survivors. The remainder achieved ROSC a fter HEMS arrival. Case by case, HEMS assistance was considered possibly im portant in 17 survivors. We found no relation between survival and HEMS res ponse time (P=0.77). Discussion: Survival following out-of-hospital cardiac arrest assisted by H EMS in this region is low, but not negligible. While primary care is most i mportant, HEMS may possibly contribute to the additional survival of 0.19 t o 0.46 patients per 100 000 per year. This benefit appears to be independen t of HEMS response time.