In order to evaluate the usefulness of impedance audiometry as a screening method for school children, two different pilot studies were performed. The results indicated that impedance audiometry (tympanometry and stapedius reflex test) was more efficient than otoscopy and pure tone screening in the detection of ears with secretory otitis media (SOM). In order to gain some more experience, an extended study of 800 7-year-olds was performed. The results from this investigation showed 6.5% pathological values with pure tone screening, 13.5% pathological values with tympanometry and 32% elevated or nonelicitable stapedius reflexes. Analysis of our observations indicates that the stapedius reflex may be too sensitive a test to be used as a screening method. Tympanometry, however, is recommended as a complement to pure tone screening in screening of children. A 6–12 months follow-up was also performed on 357 ears in which an initial study had shown a middle ear pressure of ≤ −100 mm H2O. At the repeated test 20% had pathological pure tone screening, 40% had a middle ear pressure of ≤ −100 mm H2O, 57% had elevated or nonelicitable stapedius reflexes, and 14% had middle ear effusion. The high frequency of persisting abnormal middle ear pressure and effusion in these 357 ears suggests that a middle ear pressure of ≤ −100 mm H2O can be a predisposing factor for SOM. In an experimental study on human temporal bones it was demonstrated that the tympanogram preserves its original appearance when the water level is low in the middle ear, while a higher level gives rise to a pathological tympanogram. It is also demonstrated that there is a discrepancy between the tympanometrically, indirectly recorded middle ear pressure and the middle ear pressure as measured manometrically, directly from the middle ear.
Impedance Audiometry in Clinical Practice
