ED90 of Bupivacaine After Lidocaine Test Dose With DPE and EPL

The primary objective of our study is to use a biased coin up-down allocation methodology to estimate the dose of bupivacaine required after the lidocaine test dose to achieve initial effective comfort in 90% of patients (post test-dose ED90) via the epidural (DPE or EPL) technique in women undergoing labor induction or augmentation; the investigators hypothesize that the investigators will be able to determine the post test-dose ED90 of bupivacaine for each technique with adequate precision to inform the optimal doses to study in a subsequent randomized trial comparing the analgesic effects of DPE vs. EPL. The investigators also hypothesize that the post test-dose ED90 of bupivacaine is lower with a DPE technique than with a conventional epidural technique.