STUDY OBJECTIVE To examine whether nasal bi-level positive airway pressure (BiPAP) can be used as an airway during combined epidural-propofol anesthesia. DESIGN Prospective, consecutive case series study. SETTING Operating room at a general hospital. PATIENTS 213 ASA physical status I and II adult patients undergoing lower extremity or lower abdominal gynecology surgery. INTERVENTIONS After epidural anesthesia, propofol was infused at 20 mg/kg/hr (P20) for 4 to 5 minutes followed by 5 mg/kg/hr (P5), and nasal continuous positive airway pressure (CPAP) 8 cm H(2)O and BiPAP 14/8 cm H(2)O was applied. In clinical situations, BiPAP with respiratory rate (RR) 10 breaths/min was applied. Furthermore, tidal volume (V(T)) during anesthesia, the effect of changing pressure support levels, and evaluation of pressure-controlled ventilation without spontaneous breathing were examined. MEASUREMENTS AND MAIN RESULTS CPAP resulted in a high RR, marked increased PaCO(2), and slightly decreased PaO(2), whereas BiPAP showed no change or a slightly decreased RR, slightly increased PaCO(2), and no change in PaO(2) or a great increase in PaO(2) with oxygen delivery. In clinical applications, similar results were found and anesthetic conditions were sufficient. Tidal volume increased after induction and maintained increased values under BiPAP 14/8 cm H(2)O. Of V(T) at 2, 6, or 10 cm H(2)O of pressure support levels, the 6 cm H(2)O was appropriate. Vecuronium injection showed a slight decrease and then increase in V(T) and PaCO(2), but the values were within normal (safe) limits. Respiration after rapid and high-dose infusion of propofol showed a markedly decreased RR, but the V(T) was maintained, and PaCO(2) and PaO(2) were at safe values. Rapid induction with 2.0 mg/kg propofol followed by P5 showed satisfactory results, in all but the obese patients. CONCLUSIONS BiPAP 14/8 cm H(2)0 with RR at 10 breaths/min during combined epidural-propofol anesthesia can be used to provide ventilatory support in lower extremity or lower abdominal gynecology surgery.