Fig. 2From: A comparison of video laryngoscopy and direct laryngoscopy in critically ill patientsTrial sequential analysis (TSA) of the first-attempt success rate. The blue Z curve represents the treatment effect (pooled relative risk). Green dotted lines denote traditional boundaries, and red solid lines indicate TSA boundaries. RIS, required information size; VL, video laryngoscopy; DL, direct laryngoscopyBack to article page