Intravenous Remifentanil Patient-controlled Analgesia (PCA) and Epidural Patient Controlled Epidural Analgesia (PCEA) for Labor Analgesia

Inclusion criteria: * Healthy women * American Society of Anesthesiologists physical status class I or II * Body weight less than 110 kg * In active labor (including induced labor and premature rupture of membranes) * Cervical dilatation at 2-6 cm * Regular contractions * Age between 18 and 40 years old * Gestational age greater than 36 completed weeks * Singleton pregnancy and vertex presentation Exclusion criteria: * Contraindication for epidural analgesia (bleeding diathesis, neuropathy, severe scoliosis, previous spine surgery, local anesthetic allergy) * Narcotic administration in the previous 2 hours * Previous uterine surgery * Pre-eclampsia and the inability to adequately understand the consent form * Blocked nose, and any indication patient for whom epidural analgesia is medically indicated (cardiac disease, suspected difficult airway)