title: Is it the H or the EMS in HEMS that has an impact on trauma patient mortality? A systematic review of the evidence.
abstract: OBJECTIVE
  Prehospital care of trauma patients is a matter of great debate. The optimal transport method remains undecided, with conflicting data comparing helicopter and ground emergency medical transfer. This study systematically reviews the evidence comparing helicopter and ground transfer of trauma patients from the scene of injury.
  
  
  METHODS
  A systematic literature review of all population-based studies evaluating the impact on mortality of helicopter transfer of trauma patients from the scene of injury. We searched MEDLINE, CINAHL and EMBASE from January 1980 to December 2008 and selected and reviewed potentially relevant studies.
  
  
  RESULTS
  A search of the literature revealed 23 eligible studies. 14 of these studies demonstrated a significant improvement in trauma patient mortality when transported by helicopter from the scene. 5 of the 23 studies were of level II evidence with the remainder being of level III evidence. Data were then entered into an evidence table and reference made to transport staffing, intubation rate, time at scene and time/distance of transfer.
  
  
  CONCLUSIONS
  The role and structure of HEMS in a modern trauma service is a debate that is likely to continue. Prehospital care design should be specific to critical incident frequency, geographical arrangements of hospital facilities and travel times within each trauma network. It is also important to consider the benefits and capabilities of the emergency medical team separately from the transport method being considered. An effective helicopter EMS will ultimately depend on effective operating procedures and tasking protocols, clinical governance, and auditing of the helicopter EMS activity.
authors.affiliation: Academic Foundation Trainee, Department of Orthopaedic Trauma Surgery, University of Oxford, Kadoorie Centre, John Radcliffe Hospital, Oxford OX3 9DU, UK. dan.butler@doctors.org.uk
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Butler
authors.forename: Imran
authors.initials: I
authors.lastname: Anwar
authors.forename: Keith
authors.initials: K
authors.lastname: Willett
mesh_terms: D017732:Air Ambulances; D000552:Ambulances; D004632:Emergency Medical Services; D006801:Humans; D014187:Transportation of Patients / Q000379:methods*; D014947:Wounds and Injuries / Q000401:mortality*