HEMS inter-facility transfer: a case-mix analysis

Helicopter emergency medical services (HEMS) are popular rescue systems despite inconsistent evidence in the scientific literature to support their use for primary interventions, as well as for inter-facility transfer (IFT). There is little research about IFT by HEMS, hence questions remain about the appropriateness of this method of transport. The aim of this study was to describe a case-mix of operational and medical characteristics for IFT activity of a sole HEMS base, and identify indicators of over-triage.

This is a retrospective study on HEMS IFT over 36 months, from January 1st 2013 to December 31st 2015. Medical and operational data from the database of the Emergency Department of Lausanne University Hospital, which provides the emergency physicians for this helicopter base, were reviewed. It included distance and time of flight transport, type of care during flight, and estimated distance of transport if conducted by ground.

There were 2194 HEMS missions including 979 IFT (44.6%). Most transfers involved adults (> 17 years old; 799 patients, 81.6%). Forty patients (4.1%) were classified as having benefitted from resuscitation or life-saving measures performed in flight, 615 (62.8%) from emergency treatment and 324 (33.1%) from simple clinical examination. The median distance by air between hospitals was 35.4 km. The estimated median distance by road was 47.7 km. The median duration time from origin to destination by air was 12 min.

This case-mix of IFTs by HEMS presents a high severity. There are many signs in favour of over-triage. We propose indicators to help choosing whether HEMS is the most appropriate mean of transport to perform the transfer regarding patient condition, geography, and medical competences available aboard ground ambulances; this may reduce over-triage.