[Development of a three-dimensional impedance meter and its clinical applicability to diagnosing middle ear diseases].

An impedance meter (IM) is well known to be a valuable apparatus for the diagnosis of secretory otitis media (SOM). However, it is insufficient for the diagnosis of ossicular chain disorders, because the probe tone is limited to one or two frequencies. Therefore, we developed a new IM, with sweeping functions for both frequency and pressure which can display measurement results in a three-dimensional format. In this study, the middle ear dynamic characteristics of normal subjects and patients were measured, and the effects of various kinds of middle ear diseases on these dynamic characteristics were examined. The measurement results of the patients with ossicular chain separation, ossicular chain fixation, SOM, tympanic membrane perforation and tympanic membrane atelectasis showed their own distinctive patterns, and were also clearly different from those of normal subjects. Therefore, it is concluded that this apparatus has a high degree of clinical applicability to the diagnosis of these diseases.