Characteristics of the type B tympanogram can predict the magnitude of the air-bone gap in otitis media with effusion.

Tympanometry is well established as a means of assessing the presence of fluid in the middle ear. The type B tympanogram is usually considered a unique entity. However, its shape may vary from a rounded type B with a "pseudopeak" to a completely flat response. The aim of this study was to compare the characteristics of the B curve (maximum admittance, tympanometric peak pressure, and area under the curve) to the viscosity of the middle ear fluid and to the air-bone gap (ABG). In 67 children (93 ears) who underwent ventilation tube insertion, no correlation was found between the viscosity of the middle ear fluid and the characteristics of the B curve. However, these characteristics were able to differentiate between a low ABG (0 to 20 dB) and a high ABG (>20 dB). A statistical difference was also found for the three parameters (maximum admittance, p < .0025; pressure, p < .025; and area under the curve, p < .0005). Tympanometry may be used as an objective measure to estimate the extent of conductive hearing loss, especially in young children.