Fig. 4From: Efficacy of programmed intermittent bolus epidural analgesia in thoracic surgery: a randomized controlled trialVAS scores at POD 1. Data are presented as median [lower–upper quartiles]. The Mann–Whitney U test was used for comparison of categorical variables. VAS: visual analog scale, PIB: programmed intermittent bolus, CEI: continuous epidural infusion, POD: postoperative dayBack to article page