Table 2 Knowledge basis for the risk assessment

i)

A review of the literature on outcomes of pre-hospital advanced airway management (unpublished), including a recent Cochrane review on the same topic [30].

ii)

A recent survey of Norwegian helicopter emergency medical service (HEMS) physicians' own perceptions of the safety and quality of pre-hospital airway management in their system [19].

iii)

Audit of data from patients with severe traumatic injury treated by the assessed HEMS systems in the 1994 -- 2005 period (unpublished data, manuscript in preparation).

iv)

Expert judgement by three of the authors (SS, HML and ARN) as experienced HEMS physicians and one independent HEMS physician from the system assessed.

v)

The literature cited in this study.