Probable cause in helicopter emergency medical services crashes: what role does ownership play?

BACKGROUND: The National Transportation Safety Board (NTSB) ranks helicopter emergency medical services (HEMS) as one of the most perilous occupations in the United States, with improvements in its safety of highest priority. As many injured patients are transported by helicopter, this is of particular concern to the trauma community. The use of HEMS is associated with a heightened degree of inherent risk. We hypothesized that this risk is not uniform and varies with the entity providing HEMS, specifically, commercial versus public safety providers. METHODS: The NTSB accident database was queried to identify all HEMS-involved events for the 15-year period 1998 to 2012. The NTSB investigation report was reviewed to obtain crash details including probable cause. These were analyzed on the basis of HEMS ownership. Statistical analyses were performed using analysis of variance and Fisher's exact test as appropriate. RESULTS: During the study period, 139 (6.8%) of 2,040 crashes involved HEMS and occurred across 134 cities in 37 states, killing 120 and seriously injuring 146. Of these, 118 involved commercial, 14 not-for-profit, and 7 public safety HEMS. Analyzed in 5-year blocks, no decrease in crash incidence was seen (p = 0.7, analysis of variance). Human and pilot errors were significantly more common among commercial HEMS compared with public safety HEMS (91 of 118 vs. 2 of 7, p = 0.013, and 75 of 116 vs. 1 of 7, p = 0.017, Fisher's exact test). Conditions for which training was not adequate, limited resources, inadequate equipment, and the undertaking of suboptimal trips were identified as key factors. Trauma patients were involved in 34 transports (24.5%), with a fatal or serious outcome in 68 crew/patients on 12 flights. CONCLUSION: Potentially preventable human and pilot error-related HEMS crashes are significantly more frequent among commercial compared with public safety providers. Deficiencies in training, reduced availability of equipment and resources, as well as questionable flight selection seem to play a key role. LEVEL OF EVIDENCE: Epidemiologic study, level III.