Effects of minor surgery and endotracheal intubation on postoperative breathing patterns in patients anaesthetized with isoflurane or sevoflurane

We studied the effects of minor surgery and endotracheal intubation on post operative breathing patterns. We measured breathing patterns and laryngeal resistance during the periods immediately before intubation (preoperative) and immediately after extubation following minor surgery (postoperative) in eight patients anaesthetized with sevoflurane and eight patients anaesthet ized with isoflurane, breathing spontaneously through a laryngeal mask airw ay at a constant end-tidal anaesthetic concentration (1.0 MAC). In both sev oflurane-anaesthetized and isoflurane-anaesthetized patients, expiratory ti me was reduced and inspiratory and expiratory laryngeal resistance increase d after surgery. In sevoflurane-anaesthetized patients, occlusion pressure (P-0.1) increased without changes in inspiratory time (T1). Occlusion press ure did not change and T1 was greater in isoflurane-anaesthetized patients after surgery. Minor surgery may have a small but significant influence on breathing and increased laryngeal resistance following endotracheal intubat ion may modulate these changes. The difference in breathing pattern between sevoflurane and isoflurane may be a result of different responses of the c entral nervous system to different anaesthetics in the presence of increase d laryngeal resistance.