The measurement of occlusion pressure during anaesthesia. A comparison of the depression of respiratory drive by methohexitone and etomidate.

Occlusion pressure (Po max) was used to indicate the depression of respiratory drive following rapid administration of methohexitone 0.5 mg/kg and etomidate 0.067 mg/kg to fourteen patients under stable light anaesthesia. Methohexitone produced considerably more respiratory depression than etomidate, the difference probably being clinically significant. Po max is the maximum sub-atmospheric pressure generated in the trachea when inspiration is prevented by occlusion of the airway, at functional residual capacity. The factors concerning the use of this simple, non-invasive technique during anaesthesia are discussed, and suggestions made for producing consistent, useful, measurements.