Air ambulance tasking: mechanism of injury, telephone interrogation or ambulance crew assessment?

OBJECTIVE: The identification of serious injury is critical to the tasking of air ambulances. London's Air Ambulance (LAA) is dispatched by a flight paramedic based on mechanism of injury (MOI), paramedical interrogation of caller (INT) or land ambulance crew request (REQ).This study aimed to demonstrate which of the dispatch methods was most effective (in accuracy and time) in identifying patients with serious injury.

METHODS: A retrospective review of 3 years of data (to December 2010) was undertaken. Appropriate dispatch was defined as the requirement for LAA to escort the patient to hospital or for resuscitation on-scene. Inaccurate dispatch was where LAA was cancelled or left the patient in the care of the land ambulance crew. The χ(2) test was used to calculate p values; with significance adjusted to account for multiple testing.

RESULTS: There were 2203 helicopter activations analysed: MOI 18.9% (n=417), INT 62.4% (n=1375) and REQ 18.7% (n=411). Appropriate dispatch rates were MOI 58.7% (245/417), INT 69.7% (959/1375) and REQ 72.2% (297/411). INT and REQ were both significantly more accurate than MOI (p<0.0001). There was no significant difference in accuracy between INT and REQ (p=0.36). Combining MOI and INT remotely identified 80.2% of patients, with an overtriage rate of 32.8%. Mean time to dispatch (in minutes) was MOI 4, INT 8 and REQ 21.

CONCLUSIONS: Telephone interrogation of the caller by a flight paramedic is as accurate as ground ambulance crew requests, and both are significantly better than MOI in identifying serious injury. Overtriage remains an issue with all methods.