Berlot 2009.

Methods	Retrospective cohort, ground comparison group only
Participants	People with traumatic brain injury in the Fruli‐Venezia Giulia region, Italy, 2002‐2007
Interventions	HEMS vs. GEMS transport to 1 of 2 specialty hospitals for traumatic brain injury
Outcomes	Mortality
Notes	HEMS crews had advanced‐life support‐capable physicians and 2 nurses, GEMS crews had a nonadvanced life support physician and 2 nurses; people transported by HEMS were treated more aggressively
Risk of bias
Bias	Authors' judgement	Support for judgement
Reporting bias	High risk	7/11
External validity	Low risk	3/3
Internal validity	High risk	4/7
Internal validity: confounding and selection bias	High risk	1/6
Power	High risk	0/5