The use of acoustic impedance measurement as a means of evaluating the physiological function of the middle ear system is gaining wide interest by pediatricians.1-3 The impedance technique is extremely sensitive to differentiating between normal and pathological middle ears.
Children with middle ear effusions are typically identified by physicians through an otoscopic examination, or by audiologists when the child fails the traditional hearing screening test at school. Most physicians use otoscopy to visually examine the tympanic membrane, but with varying degrees of success.4 Otologists teach that pneumatic otoscopy is an absolute necessity to identify the presence of middle ear disease, yet only 25% of physicians use the pneumatic otoscope.5 In a recent study of the accuracy of otoscopic diagnoses, 15% to 20% of ears in children under 3 years of age with effusions were missed clinically. This high miss rate was noted in a group of examiners from a medical center who were aware that their diagnostic skill was being evaluated and thus should have been motivated to perform their most careful otoscopy.6 Accurate otoscopy and pneumotoscopy require skilled and experienced individuals. Our experience in training health professionals shows considerable variability in interpretation of otoscopic observations. Other problems in otoscopy include difficulty in visualizing the tympanic membrane, the removal of cerumen prior to examination, and the unwillingness of some children to cooperate with the examination.
Tympanometry resolves many of the disadvantages of conventional audiology and otologic assessment. It requires only passive cooperation from children since no overt response is required.