Tympanometric preconditioning of the tympanic membrane

Preconditioning is a general biomechanical phenomenon, where tissue characteristics change due to repetitive loading-unloading experiments, resulting in an increased compliance. Increasing compliance by repetitive tympanometric measurements has previously been described and may be related to rate of pressure change during recordings. Presently, 9 tympanometries were performed in a group of normal adults (n = 103 ears) at 4 different rates: 50, 100, 200, and 400 daPa/s. Compliance showed an initial larger increase from trial to trial, tending to reach a steady state during later trials, and the pattern was found identical in all 4 groups. However, stratifying data according to compliance at 1st trial of each ear, the preconditioning effect was found significantly correlated to compliance (P < 0.001), so that low compliance was associated with low preconditioning and vice versa. Stratification also illustrated that, while most ears reached a steady state, some ears with high compliance (> or = 1.04 cm3) did not. In this way identification is possible of tympanic membranes, which are less resistant to pressure loads and therefore may be susceptible to development of retraction pockets. Repeatable measures of compliance with insignificant effect of preconditioning could be obtained after 5 tympanometries, and measures of precision of compliance are reported.