Application of nasal bi-level positive airway pressure to respiratory support during combined epidural-propofol anesthesia

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 H2O and BiPAP 14/8 cm H2O was applies. 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 high RR, marked increased PaCO2, and slightly decreased PaO2, whereas BiPAP showed no change or a slightly decreased RR, slightly increased PaCO2, and no change in PaO2 or a great increase in PaO2 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 H2O. Of V-t at 2, 6 or 10 cm H2O of pressure levels, the 6 cm H2O was appropriate. Vecuronium injection showed a slight decrease and then increase in V-t and PaCO2, 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 PaCO2 and PaO2 were at safe values. Rapid induction with 2.0 mg/kg propofol followed by P5 showed satisfactory results, in all but obese patients. Conclusions: BiPAP 14/8 cm H2O 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. (C) 2002 by Elsevier Science Inc.