Thomas 2002.

Methods	Retrospective cohort, ground comparison group only
Participants	People with blunt trauma only, in New England, USA, 1995‐1998
Interventions	HEMS vs. GEMS transport to 1 of 5 level I trauma centers
Outcomes	Mortality
Notes	HEMS crews: all had a nurse, some had a physician, GEMS crews: paramedics and nurses
Risk of bias
Bias	Authors' judgement	Support for judgement
Reporting bias	Low risk	9/11
External validity	Low risk	3/3
Internal validity	Unclear risk	4/7
Internal validity: confounding and selection bias	Unclear risk	3/6
Power	High risk	0/5