Differential otomanometry

Abstract

Management of otitis media, both acute and chronic, is one of the most common problems in clinical medicine. Among the many unresolved issues in otitis media research is accurate diagnosis which, in turn, depends heavily on valid otoscopic observation. Yet even today clinical otoscopy remains more of an art than a science. Because precise therapy is predicated on precise diagnosis, efforts to improve the validity and reliability of otoscopic techniques are warranted. Of great importance to the otoscopist is the visual estimate of tympanic membrane mobility secondary to hand-generated pneumatic pressure (pneumotoscopy). The degree of motion is usually graded in relative terms. In addition to pneumotoscopy, tympanometry is also used to assess the status of the middle ear. This is done indirectly through the plot of induced pressure versus acoustic immitance (tympanogram). Thus, both procedures depend on the differential application of induced pneumatic pressure on the tympanic membrane. If the middle ear is air-containing and the tympanic membrane is normal, even a slight pressure rise in the ear canal will displace the membrane. If the middle ear is fluid-filled, even large amounts of pressure produce no motion of the tympanic membrane. The pressure gradients, normal threshold, and optimal frequency of application for pneumotoscopy have not been studied previously in humans. Data are presented to compare the sensitivity, specificity, and predictive value of pneumotoscopy and tympanometry in the detection of effusion due to chronic secretory otitis media. In addition, preliminary data obtained by a new procedure, quantitative pneumotoscopy, are discussed.