Normal tympanometric shape.

Computer-assisted curve-fitting techniques were used to describe quantitative and qualitative characteristics of normal tympanometric shape. The data base consisted of set of triplicate tympanograms, obtained at 2-week intervals, from 72 ears of children with normal middle ears enrolled in the first through the fifth grades. A nonlinear equation produced significantly better prediction of normal tympanograms (R2 = 0.70) than did linear equations (R2 less than 0.44), bringing into question the use of the latter in determining normality. The complexity of applying curve fitting in clinical practice led to the development of a qualitative technique to determine normality. An initial application of the technique as a screen in 76 ears subjected to myringotomy produced a sensitivity of 96% and a specificity of 83% with respect to identification of the presence of middle ear fluid.