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Ventilation‐Perfusion Relationships During Epidural Analgesia

Resting lung volume (FRC), airway closure (CC) and ventilation‐perfusion relationships, using the multiple inert gas elimination technique, were studied during epidural analgesia. The material consisted of 10 patients, 55–84 years of age. Epidural blockade (9–13 ml mepivacaine‐adr. 1/200,000) was instituted to an upper level corresponding to Th3‐Th6. Minute ventilation and breathing frequency remained unchanged during the epidural block, while cardiac output was significantly increased (4.80‐5.74 1/min). The relationship between FRC and CC (FRC‐CC) was unchanged during the block, indicating an unchanged magnitude of airway closure. Multiple inert gas elimination data revealed virtually unchanged distribution of ventilation and perfusion during the epidural block in 9 of the 10 patients. It is concluded that lumbar epidural analgesia up to Th3‐Th6 does not influence the degree of airway closure, nor does it cause V̇a/Q̇. mismatching as general anaesthesia does.