[Comparison of the low and high frequency tympanometries as diagnostic tests of middle ear function in infants].

Objective: To evaluate the effect of low frequency and high frequency tympanometry in the diagnosis of middle ear function of infants.

Methods: Tympanometries with 226 Hz, 678 Hz and 1000 Hz probe tones were obtained from infants aged 5-25 weeks with normal ABR (15 infants, 30 ears) and those with prolonged Wave I latency suggesting middle ear dysfunction (17 infants, 20 ears) using GSI Tympstar middle ear analyzer.

Results: The type, peak pressure, peak compensated static acoustic admittance and gradient of 226 Hz tympanometry were of no significant differences between two groups. The pattern of 678 Hz tympanograms for admittance, susceptance and conductance included non-peaked, single-peaked, W-shaped and three-peaked type in both groups. The consistency between auditory brainstem response (ABR) and 678Hz tympanometry for admittance, susceptance and conductance were 70.0%, 58.0%, 64.0% (kappa = 0. 324,0. 234,0. 118) respectively. A single peaked tympanogram was typical in normal infants for 1000 Hz admittance, susceptance and conductance tympanograms and there were 28 ears (93.3%), 25 ears (83.3%) and 26 (86.7%) respectively. Tympanogram without any positive peak was the most characteristic for a probe frequency of 1000 Hz in infants with prolonged wave I latency and there were 15 ears (75%), 17 ears (85%) and 13 ears (65%) respectively. For admittance, susceptance and conductance, the consistency between 1000 Hz tympanometry and ABR were 90.0%, 92.0% and 86.0% and kappa were 0.783, 0.831 and 0.690, respectively.

Conclusions: 1000 Hz probe tone tympanometry was accurate diagnostic tests for middle ear function in infants younger than 25 weeks of age, while 226 Hz and 678 Hz probe tone tympanometries were not.