Tympanometry and otoacoustic emissions in a cohort of special care neonates.

Otoacoustic emission (OAE) screening and oto-admittance testing (678 Hz probe tone) were performed on both ears of 84 special care neonates, as part of a larger study of middle-ear effusion in neonates and infants. OAE results, tympanometry, and acoustic reflex results are all strongly and significantly associated. No evidence was found of any maturational effects in the results. Based on the findings, a tentative classification scheme for neonatal tympanograms is suggested. We conclude that 678 Hz tympanometry is a useful indicator of middle-ear status in very young babies, and that middle-ear effusion does strongly affect OAEs in neonates. OAEs are also strongly affected by negative middle-ear pressure (MEP), and mean MEP in ears failing OAE screens was significantly more negative than in those passing. The prevalence of abnormal tympanometry, which may indicate middle-ear effusion or dysfunction, was 20% of ears (29% of babies) in this group. It appears that middle-ear effusion could account for about half of the ears failing an OAE screen on the special care baby unit. We also find that length of stay on the special care baby unit is an important risk factor for development of middle-ear effusion: those on the unit for over 30 days have about four times the risk of bilateral abnormal tympanometry.