Fig. 3
Effect of subglottic secretion suction on preventing ventilator-associated pneumonia in four high-quality trials. a Forest plot comparing subglottic secretion suction (SSS) and non-SSS on incidence of ventilator-associated pneumonia. b Trial sequential analysis for incidence of ventilator-associated pneumonia with control arm event proportion of 21.2 %, relative risk reduction of 20 %, α of 5 % (two sided), β of 20 %, and I 2 = 0 %. The required information size was calculated as 2729. Z curve has across-trial sequential monitoring boundary for benefit. Risk of bias: A random sequence generation (selection bias), B allocation concealment (selection bias), C blinding of outcome assessment (detection bias), D incomplete outcome data (attrition bias), E selective reporting (reporting bias), F other bias; CI confidence interval, M-H Mantel-Haenszel