Multifrequency tympanometry in neonatal intensive care unit and well babies.

BACKGROUND Conventional low probe tone frequency tympanometry has not been successful in identifying middle ear effusion in newborn infants due to differences in the physiological properties of the middle ear in newborn infants and adults. With a rapid increase in newborn hearing screening programs, there is a need for a reliable test of middle ear function for the infant population. In recent years, new evidence has shown that tympanometry performed at higher probe tone frequencies may be more sensitive to middle ear disease than conventional low probe tone frequency in newborn infants. PURPOSE The main goal of this study was to explore the characteristics of the normal middle ear in the NICU (neonatal intensive care unit) and well babies using conventional and multifrequency tympanometry (MFT). It was also within the scope of this study to compare conventional and MFT patterns in NICU and well babies to already established patterns in adults to identify ways to improve hearing assessment in newborns and young infants. METHODS Three experiments were conducted using standard and MFT involving healthy babies and NICU babies. NICU babies (n = 33), healthy three-week-old babies (n=16), and neonates on high-priority hearing registry (HPHR) (n=42) were tested. Thirty-two ears of 16 healthy Caucasian adults (compared to well-babies) and 47 ears of 26 healthy Caucasian adults (compared to NICU babies) were also included in this study. RESULTS The distribution of the Vanhuyse patterns as well as variation of admittance phase and peak compensated susceptance and conductance at different probe tone frequencies was also explored. In general, in both well babies and NICU babies, 226 Hz tympanograms are typically multipeaked in ears that passed or referred on transient otoacoustic emission (TEOAE), limiting the specificity and sensitivity of this measure for differentiating normal and abnormal middle ear conditions. Tympanograms obtained at 1 kHz are potentially more sensitive and specific to presumably abnormal and normal middle ear conditions. Tympanometry at 1 kHz is also a good predictor of presence or absence of TEOAE.