Wideband Immittance In Neonates:


The traditional tympanometry probe-tone at 226 Hz evokes different results depending on the anatomical characteristics of the middle ear (ME)  cavity, which can influence the test results. The use of a wideband stimulus (i.e. acoustic click, chirp) has been shown to be more efficient and precise for a ME assessment.  Because of the presence of multiple frequencies in the transient stimuli, Wideband Tympanometry (WBT) is less susceptible to myogenic noise, which originates from the patient movements .

The WBT evaluates the ME function with a transient stimulus (click or chirp) testing frequencies from 226 to 8000 Hz, in small incrementing steps. Assessment of ME function over such a broad bandwidth provides detailed information on the ME status and can assist considerably any needed diagnosis.

Currently there are two families of devices in the market, which offer WBT measurements: (i) the Otostat,  and the HearID systems from Mimosa Acoustics, USA;  and (ii) the Titan system from Interacoustics, Denmark. As in the traditional tympanometry, WBT is performed by placing a sealing probe into the external auditory canal. The probe  contains a microphone, a pressure system and a speaker transducer. The Mimosa devices are PC-independent, while the Titan requires a PC connection to perform the WBT measurements. Figure 1 shows the WBT data from the Otostat system, displayed on a PC running the Otostation data management software. Figures 2, 3 show WBT data from the Titan device. 

Figure 1:WBT data from the Otostat system (Mimosa Acoustics). The panels indicate WBT Reflectance, Absorbance and Pressure response x tested frequency (The Otostat uses a chirp stimulus). The lower panels show the Distortion product OAEs in terms of spectrum and S/N ratios at the 4 tested frequencies. The WBT + OAE combination favors a good assessment of the ME function in neonates and it can be used to avoid many REFER or FAIL results. 


Figure 2: WBT normal data from a neonatal subject.  Portal Users have the possibility to download  a  video on how this image can be manipulated in the Titan environment in order to observe other aspects of the response. 


 Figure 3: WBT normal data from a neonatal subject, which probably presents some ME transmission problems.  Portal Users have the possibility to download  a  video on how this image can be manipulated in the Titan environment in order to observe other aspects of the response.