[Low-frequency tympanometry in normal neonates].

Objective: To find the characteristic of tympanogram results obtained from normative neonates 2 - 7 days about low frequency (226 Hz) probe tone, and to determine the normative values for tympanometric variables.

Method: Transient evoked otoacoustic emission (TEOAE) screening were performed by using AccuScreen Pro instrument for 135 neonates. Among them, 105 neonates passed the TEOAE screening in both ears. The 226 Hz probe tone tympanograms and their normative values were obtained from them using GSI-33 middle ear analyzer.

Result: The 226 Hz tympanometric data for the 105 neonates (210 ears) passed the TEOAE screening in both ears showed a double-peaked tympanogram in 202 ears (96.19%), a single-peaked tympanogram in 8 ears (3.81%). For double-peaked tympanogram in 202 ears, the tympanometric normative values was below: the first peak admittance is (0.91 +/- 0.18)mmho, Tpp is about (18.02 +/- 12.26)daPa; the second peak admittance is (1.05 +/- 0.23)mmho, Tpp is about (-35.05 +/- 16.80) daPa; the admittance of notch between the two peaks is (0.74 +/- 2.57)mmho, its pressure is about (0.37 +/- 7.61) daPa. Vec is about (0.50 +/- 0.08)ml.

Conclusion: The 226 Hz tympanograms obtained from this cohort may serve as a guide for evaluating middle ear function in neonates.