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Middle ear susceptance and conductance were measured before, during, and after general surgery on fifteen subjects. Tympanometric pressure increased with diffusion of gases in the middle ear for all subjects and subsequently decrease due to physiological ventilation for 86.7% of the sample as expected [Perreault et al., Can. Anaesth. Soc. J. (March 1981) (in press)]. However, the changes in shape of the tympanograms and values of the resistance, mass, and stiffness were highly variable. The middle ear system was more mobile than the average as evidenced by the frequent occurrence of regular and irregular W patterns. This did not correlate with microscopic eardrum examination but did correlate with hypermobility of the tympanic membrane found in a control group for which admittance was measured only prior and after surgery. Finally, after anesthesia, diffusion of gases from middle ear caused high negative pressure for 30% of the subjects. This result could be predicted from poor active Eustachian tube function tested before anesthesia. [Work supported by Alma Mater.] [ABSTRACT FROM AUTHOR]