This study evaluates the respiratory effects of laparoscopy under epidural anesthesia in seven female patients (ASA physical status I) scheduled for a gamete intrafallopian transfer procedure. Epidural anesthesia was performed with 15-18 mL of 1.5% plain lidocaine using a catheter inserted at the L3-4 level. The upper level of analgesia to pinprick was measured 20 min after lidocaine injection. Ventilatory measurements and arterial blood gas analyses were performed (a) preoperatively, in the horizontal supine position with a T7-9 level of analgesia; (b) in the 20 degrees Trendelenburg position with a T2-5 level of analgesia; (c) during intraabdominal insufflation of CO2 through the laparoscope; and (d) after CO2 exsufflation by manual compression of the abdomen before removal of the laparoscope while in the horizontal position. On-line measurements of VO2, VCO2, VE, VT, F, and PETCO2 were made using a Beckman metabolic cart, while the patients breathed room air through an anesthetic face mask. No significant changes in the ventilatory variables were observed in the Trendelenburg position. In contrast, CO2 insufflation significantly increased VE (from 9.1 +/- 1.0 L/min to 11.8 +/- 2.6 L/min, mean +/- SD), and F (from 16.9 +/- 1.9 breaths/min to 23.1 +/- 3.3 breaths/min, mean +/- SD), whereas VCO2 remained unchanged. PaCO2 remained constant throughout the study. These results suggest that epidural anesthesia may be a safe alternative to general anesthesia for outpatient laparoscopy, as it is not associated with ventilatory depression.