Forest plot showing the effect of probiotics on the occurrence of nosocomial pneumonia (NP) in critical ill patients. Pooled ORs were calculated using the Mantel-Haenszel (M-H)Estimator. Study-level data were pooled using a random-effects model when I2 was > 50% or a fixed-effects model when I2 was < 50%.
Liu et al. Critical Care 2012 16:R109 doi:10.1186/cc11398