Detection of inspiratory resistive loads after anaesthesia for minor surgery.

We measured the ability to detect inspiratory resistances in 22 patients undergoing minor gynaecological surgery, using linear resistances of 1.2-24.4 cm H2O litre-1 s, and ranked 1-9. The rank that could be detected was measured before surgery, approximately 10 min after recovery from anaesthesia, and then 25 min later. After anaesthesia there was a significant increase (P < 0.001) in the rank number by 2, which returned to preoperative values 25 min later. Minute ventilation was reduced by 25% after operation and this may partly explain this change; however, we believe the transient decrease in ability to sense resistance indicates residual effects of anaesthetics and may explain in part the incidence of hypoxia caused by airway obstruction in patients after anaesthesia.