Respiratory effects of high thoracic epidural anaesthesia.

The respiratory effects of high thoracic epidural anaesthesia (TEA) were studied in nine healthy volunteers by means of spirometry, nitrogen single-breath test and flow-volume loop. After the baseline measurements an epidural catheter was inserted at T4 level, and 5 ml of 0.5% bupivacaine were injected. This volume led to sensory block within dermatomes T1-T5. Total lung capacity, vital capacity and inspiratory capacity decreased slightly but significantly during TEA. Expiratory reserve volume was not affected. Maximal inspiratory flow at 50% VC decreased 24%. Maximal expiratory (low at 75% VC and peak expiratory flow were not changed. N2 difference during a constant flow rate of 0.5 l/s and forced expiratory volume in l s were not changed, which indicates that there were no changes of bronchial tone. The respiratory effects of high TEA in this study were caused by the motor block of the intercostal muscles.