Wideband Tympanometry

WAI (Wideband Acoustic Immittance), PR (Power Reflectance)

The wideband tympanometry (WBT) assesses the middle ear function with a transient wideband stimulus in order to capture the middle ear behavior at a wide range of frequencies. WBT has more sensibility to detect middle ear disorders than the traditional tympanometry. Pathologies, which might be more easily identified/monitored by WBT, include otosclerosis, flaccid eardrums, ossicular chain discontinuity with semicircular canal dehiscence, and negative middle ear pressure with middle ear effusion, Immitance in neonates.

The traditional tympanometry probe-tone at 226 Hz evokes different results depending on the anatomical characteristics of the 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 Middle Ear function with a transient stimulus (click or chirp) testing frequencies from 226 to 8000 Hz, in small incrementing steps. Interacoustics suggests to average the WBT data starting from 375 Hz and not from 226 Hz, since the later frequency does not offer a high discriminative value.

Assessment of ME function over such a broad bandwidth provides detailed information on the ME status.

It is possible to collapse a number of frequencies and obtain absorbance data over an aver- aged frequency range (wideband averaged tympanogram), which might offer better clinical estimates for well babies and NICU residents. The WBT average range used in infants is from 800 to 2000 Hz.

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. Some may be PC independent and some dependent. With a single pressure sweep (as in traditional tympanometry) Wideband Tympanometry allows comprehensive analysis of middle ear status over a frequency range that includes the full speech spectrum.

 

Assists in differential diagnosis Through the measurement of absorbance, Wide Band Tympanometry yields information that helps to differentiate between normal middle ear function and middle ear pathologies such as fluid, otosclerosis, disarticulation of the ossicular chain, tympanic perforations, semicircular canal dehiscence, etc.1. Some of these pathologies are impossible to confirm reliably with only traditional tympanometry.

 

Interacoustics follows the philosophy of presenting the WBT data not in the traditional 2D manner but in a 3D format, depicting pressure (y-axis), frequency (x-axis), and absorbance (z-axis).

Higher absorbance values suggest a more efficient ME. Lower values suggest some sort of energy impediment in the ME structure, with a very good probability of a hearing impairment.

Advantages:

  • Increased clinical confidence and patient care
  • Assists in differential diagnosis
  • Quick and simple to operate
  • Allows efficient monitoring of middle ear status over time

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.