Phillips 1999.

Methods	Retrospective cohort, ground comparison group only
Participants	People with trauma in San Antonio, TX, USA, October 1995‐September 1996
Interventions	HEMS vs. GEMS transport to a single level I trauma center
Outcomes	Mortality
Notes	HEMS crews: nurse and paramedic, GEMS crews: 2 paramedics
Risk of bias
Bias	Authors' judgement	Support for judgement
Reporting bias	Low risk	9/11
External validity	High risk	1/3
Internal validity	Low risk	5/7
Internal validity: confounding and selection bias	High risk	3/6
Power	High risk	0/5