Figure 4: Pooled estimate for risk of needing a replacement epidural catheter during labor epidural analgesia after use of air or liquid for use in the loss-of-resistance (LOR) technique. Seven of 253 patients in the air group and 10 of 252 patients in the liquid group had their epidural catheters replaced. The pooled estimate and 95% confidence interval (CI) cross 1, suggesting no significant difference between use of air and saline (p = 0.45); RR, relative risk.