Study	Reason for exclusion
Barber 2009	Conference abstract
He 2011	Not a comparison of interest: patients in the control group received a comfortable position (include supine position, lateral position)
Leng 2012b	Not a RCT
Li 2013	Not a comparison of interest: semi‐recumbent position + chlorhexidine oral rinse versus semi‐recumbent position + saline
Liu 2011a	Not a RCT
Liu 2011b	Not a RCT
Liu 2013	Not a comparison of interest: semi‐recumbent position + chlorhexidine gluconate oral rinse versus supine position + 0.9% saline solution
Liu 2014	Quasi‐RCT: patients were assigned based on alternation
Lu 2013	Not a comparison of interest: patients in the treatment group received a comfortable position based on patients' conditions
Mao 2013	Not a RCT
Mi 2013	Not a comparison of interest: head‐of‐bed angle was measured by bedside angle instrument versus visual monitoring
Wang 2013a	Quasi‐RCT: patients were assigned based on alternation
Wang 2013b	Not a comparison of interest: head‐of‐bed angle was measured by self made bed marker versus lifted based on nurses' experience
Wu 2014	Not the target population: paediatric patients from paediatric intensive care unit
Xiao 2006	Cross‐over trial
Zhang 2006	Not a RCT

RCT: randomised controlled trial