Figure 3: Pooled estimate for risk of needing additional medication during labor epidural analgesia after use of air or liquid in the loss-of-resistance (LOR) technique. Sixty-one of 253 patients in the air group and 44 of 252 patients in the liquid group needed additional medications. The pooled estimate and 95% confidence interval (CI) cross 1, suggesting no significant difference between use of air and saline (p = 0.18); RR, relative risk.