Table 2.

Quality assessment of randomized controlled trials

	Selection bias		Performance bias	Detection bias		Attrition bias	Reporting bias
Study	Random sequence generation	Allocation concealment	Blinding of participants and personnel	Blinding for patient reported outcomes	Blinding for clinical outcomes (mortality)	Incomplete outcome data	Selective reporting
Hernandez et al. (2010)	Low	Low	Uncertain	Uncertain	Uncertain	Low	Low
Gunduz et al. (2005)	High	High	High	High	High	Uncertain	Uncertain
Bolliger and Van Eeden (1990)	High	High	High	High	High	Uncertain	Uncertain

^aStudies were considered to be of moderate quality if there were more than two domains with uncertain risk of bias. They were considered to be of low quality if four or more domains had uncertain risk of bias or if one domain had a high risk of bias.