[Respiratory effects of epidural anesthesia and anesthetic level obtained in patients for cesarean section]

In order to determine the optimal level of epidural anesthesia, the author examined respiratory function of 138 full-term pregnant women in sitting and supine positions without anesthesia, and in supine position under epidural anesthesia prior to the cesarean section. Vital capacity (VC) increased in the sitting position in comparison with supine position because expiratory reserve volume (ERV) and tidal volume (TV) increased. In contrast, %FFV1.0, peak expiratory flow (PEF) and V75 decreased as uterus shifted anteriorly in the sitting position. Under the epidural anesthesia with T4-T6 analgesic, TV showed a relative increase resulting in an increase in VC. This was due to lateral displacement of the uterus alleviating the depression of diaphragm. Epidural anesthesia with levels C8-T3 caused a reduction in inspiratory reserve volume (IRV) and ERV which in turn resulted in a decrease in VC and PaCO2. This change depended on the paralysis of respiratory muscles and the dyspneic feeling of patient. Generally %FFV1.0 and the data related to flow volume curve decreased under epidural anesthesia. In conclusion, epidural anesthesia with T4-T6 levels accompanied a sufficient analgesic efficacy and respiratory function comparable with that in the sitting position without anesthesia, therefore this was considered to be a method of choice for cesarean section.