Impedance audiometry in a young population. The effect of age, sex, and tympanogram abnormalities.

Static compliance, and acoustic reflex thresholds, were studied retrospectively in 883 subjects, aged one to 20 years. Age was a factor in both measurements. In 523 subjects with normal middle ear fuction, static compliance increased as a function of age. Acoustic reflex thresholds for pure tone signals improved with age, while acoustic reflex thresholds for broad band noise (BBN) tended to decrease. Minor tympanogram abnormalities exerted a distinct influence on static compliance and acoustic reflex thresholds. Static compliance was increased, and highly variable, in 93 subjects with A-deep tympanograms. In 212 subjects with either A-deep tympanograms, or slight negative pressure (i.e. -50 to -100 mm H2O), acoustic reflex thresholds were elevated for both pure tone, and BBN signals. In 132 sensorineural impaired subjects, the sensitivity loss differentially affected acoustic reflex thresholds for pure tone vs BBN signals. In view of the potential influence of age, and, especially, minor middle ear abnormalities, on static compliance and acoustic reflex measures, these factors should be seriously considered when interpreting impedance audiometry findings in children.