Fig. 4

The first-pass success rate of thoracic epidural placement in the study groups. Data are presented as a proportion with its 95% CI (confidence interval). The Black dashed line represents the pre-specified superiority margin (δs = 0.05). Note the lower bound of the 95%CI for the first-pass success rate of Gp-Usg (real-time ultrasound-guided group) does not overlap the upper bound of the 95%CI of Gp-Conv (conventional anatomic landmark group) and it is beyond the pre-specified δs of 5% confirming clinical superiority of Gp-Usg. # represents inter-group difference p = 0.002, and TEP, thoracic epidural placement