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

Abstract

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 2O and BiPAP 14/8 cm H 2O 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 2O. Of V T at 2, 6, or 10 cm H 2O of pressure support levels, the 6 cm H 2O 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 20 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.