Airway occlusion pressure is an indicator of respiratory depression with isoflurane

Abstract

The purpose of this study was to elucidate the respiratory depressant effects of isoflurane (0%-1.0%) using airway occlusion pressure (P0.1), a known index of the output of the respiratory centers, in ten anesthetized patients. P0.1 was measured as the pressure change obtained after the first 0.1 sec of spontaneous inspiration against the occluded airway. A significant decrease in minute volume ([Formula: see text]) and a significant increase in PaCO 2 were not observed during the periods of isoflurane 1.0% at the end-tidal concentration compared with those of control period (0% isoflurane) (P<0.05), whereas a significant decrease in P0.1 was observed during the period of isoflurane 0.5%. Our results suggested that P0.1 was a more sensitive indicator of respiratory depression than PaCO 2 or[Formula: see text], and the respiratory center was depressed with a considerably lower concentration (0.5%) of isoflurane.