| Study | Reason for exclusion |
|---|---|
| Abbott 1998 | Wrong study design (case‐control) |
| Anderson 1987 | No comparison group |
| Baack 1991 | No outcomes reported |
| Badiali 1989 | No comparison group |
| Baxt 1985 | No comparison group |
| Boyd 1988 | No comparison group |
| Burney 1992 | Quote: "The purpose of this study was to compare the severity of illness or injury and outcomes of patients transported by physician/nurse and nurse/nurse crews" |
| Cameron 1993 | No comparison group |
| Cannell 1993 | Descriptive study |
| Carrel 1994 | No comparison group |
| Chappell 2002 | Wrong study design (before/after study; "natural experiment") |
| Chipp 2010 | No comparison group |
| Cleveland 1976 | Descriptive study |
| Cocanour 1997 | No comparison group |
| Cudnik 2008 | No comparison between HEMS and GEMS |
| Cummings 2000 | No outcomes reported for an ISS >15 group (mortality was not stratified by ISS). Mortality was a secondary outcome, and not reported for HEMS vs. GEMS groups. |
| Dardis 2000 | No comparison group |
| de Jongh 2012 | Helicopter treatment team (people not transported by HEMS), case‐control study |
| De Wing 2000 | Wrong study design (case‐control study); burns |
| Di Bartolomeo 2005 | Only included people with traumatic cardiac arrest |
| Dreyfuss 1979 | Descriptive study |
| Falcone 1998 | No comparison group |
| Fischer 1984 | No comparison group |
| Frankema 2004 | Helicopter treatment team (participants not transported by HEMS) |
| Franschman 2012 | Helicopter treatment team (participants not transported by HEMS) |
| Gerhardt 2000 | Descriptive study |
| Hallock 1985 | People with burn |
| Hoogerwerf 2013 | Letter to the editor |
| Hubner 1999 | Helicopter treatment team (participants not transported by HEMS) |
| Irola 2006 | Helicopter treatment team (participants not transported by HEMS) |
| Jacobs 1999 | No comparison group |
| Jenkinson 2006 | Descriptive study |
| Karanicolas 2006 | Outcome reporting unclear (the primary analysis was a comparison of HEMS vs. GEMS interfacility transport times). It is unclear how many pediatric patients were included (standard deviation was large) and how many patients had an ISS < 15 (large standard deviations). |
| Kidher 2012 | No comparison group |
| Kruesathit 2012 | Descriptive study, does not describe HEMS care |
| Kurola 2002 | No comparison group |
| Lossius 2002 | Helicopter treatment team (participants not transported by HEMS); also included people with medical conditions (mixed participant population) |
| Mackenzie 1979 | No outcomes data (only participants transported by HEMS and those who died reported) |
| Mann 2002 | Wrong type of study design (before/after study) |
| Margolis 2009 | Descriptive study, no comparison group |
| Massarutti 2006 | No comparison group |
| Matsumoto 2006 | No comparison group |
| McCowan 2007 | No comparison group (urban vs. rural HEMS) |
| McCoy 2013 | No comparison group |
| Melton 2007 | No comparison group |
| Michel 1994 | No comparison group |
| Moen 2008 | Patient transfer study, not specifically of HEMS |
| Munford 1994 | Wrong design (editorial) |
| Nielsen 2002 | No comparison group (also included children) |
| Norton 1996 | No comparison group |
| Nutbeam 2011 | No comparison group |
| Palarcik 1991 | Descriptive study |
| Papa 1993 | No comparison group |
| Powell 1997 | No comparison group |
| Purkiss 1994 | No comparison group (examined thoracotomy data by HEMS) |
| Ringburg 2005 | No comparison group (dealt with protocol adherence for helicopter dispatch) |
| Ringburg 2007 | Helicopter treatment team (participants not transported by HEMS) |
| Ringburg 2009 | Helicopter treatment team (participants not transported by HEMS) |
| Roberts 1970 | Descriptive study |
| Rouse 1992 | No outcomes reported (outcome was mission time). ISS was not specified, and the study population was comprised of patients with "compound lower limb fracture." |
| Salimi 2009 | No comparison group |
| Sampalis 1993 | No comparison group (GEMS only) |
| Schiller 2009 | No comparison group (before/after study; 1 vs. 2 helicopters in EMS system) |
| Schipper 2006 | Wrong design (editorial; brief narrative review of previous studies) |
| Schwab 1985 | No comparison group |
| Shatney 2002 | No comparison group |
| Shepherd 2008 | No comparison group |
| Sihler 2002 | No comparison group (descriptive cohort of people who were "twice transferred" by HEMS) |
| Skogvoll 2000 | No comparison group |
| Slater 2002 | No outcomes reported |
| Snooks 1996 | Comparison of 3 different regional HEMS services |
| Spencer‐Jones 1993 | Descriptive study |
| Struck 2007 | Wrong design (questionnaire) |
| Taylor 2010 | Wrong design (systematic review) |
| Taylor 2011 | No outcomes reported (only examined costs) |
| Thomas 2000 | Descriptive study |
| Treat 1980 | No comparison group |
| Urdaneta 1984 | No comparison group |
| Urdaneta 1987 | No comparison group |
| Veenema 1995 | Not a HEMS study |
| Walcott 2011 | No comparison group |
| Williams 2003 | No comparison group |
| Wills 2000 | No comparison group |
| Wirtz 2002 | Examined HEMS crew configuration: nurse/nurse vs. paramedic/nurse |
| Yoon 2011 | Descriptive study |
| Young 1998 | No comparison group (scene vs. transfer of HEMS only) |
EMS: emergency medical service; GEMS: ground emergency medical service; HEMS: helicopter emergency medical service.