RETRACTED ARTICLE: Airway occlusion pressure is an indicator of respiratory depression with isoflurane

The purpose of this study was to elucidate the respiratory depressant effects of isoflurane (0%–1.0%) using airway occlusion pressure (P_0.1), a known index of the output of the respiratory centers, in ten anesthetized patients. P_0.1 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 ( ) and a significant increase in Pa_{CO 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 P_0.1 was observed during the period of isoflurane 0.5%. Our results suggested that P_0.1 was a more sensitive indicator of respiratory depression than Pa_{CO 2} or , and the respiratory center was depressed with a considerably lower concentration (0.5%) of isoflurane.