Tympanometry: What it is and why should you invest in it?
Tympanometry, introduced in the early 1970s, is an objective measure that assesses the function of the middle ear. Specifically, it measures the mobility of the eardrum and the ossicles (middle ear conductive bones).
Tympanometry works by placing a probe into the ear canal of a patient to introduce varied air pressure. While changing the pressure in the ear canal (usually from +200 to -300 daPa), a pure tone of 226 Hz (for adults) is presented continuously in the ear to measure the resistance encountered by the pure tone sound waves introduced to the medium. The results from this measurement indicate various states that the patient’s middle ear may be in, i.e. presence of fluid in the middle ear.
Why is tympanometry important?
Tympanometry, unlike pure tone audiometry, is an objective measurement. This means that the testing does not require subjective feedback from the patient. The patient simply sits still while the testing is in process, and results are yielded without their participation. Tympanometry yields crucial objective information such as:
- The volume of the ear canal (an indication of ear drum perforation or impacted wax),
- Pressure in the middle ear (an indicator of middle ear status – i.e. ear drum retracted; fluid in middle ear),
- Compliance of the eardrum/ middle ear system (an indicator for various conditions, i.e. ossicular discontinuation, otosclerosis).
The information yielded by tympanometry plays a crucial role in optimizing the management of auditory disorders and referral pathways. For example, in school-based hearing screenings, pure tone audiometry (air conduction) alone is not a sufficient assessment tool, nor cost effective because of over referrals. Tympanometry, in such cases, indicates whether the site of lesion is likely the outer or middle ear, or neither. This allows the tester to refer directly to a medical doctor in case of middle ear infection, or to an audiologist in case of possible auditory deficit resulting from either the inner ear or the brain.
Why should tympanometry be part of every audiological clinic?
Tympanometry is an efficient and effective test of assessing the middle ear. This measurement is useful in children, adults and the elderly.
As mentioned earlier, school-based hearing screenings are an example of the services that should incorporate tympanometric measurements. Otitis media or middle ear infection is prevalent in children. It is a fact that middle ear infections may significantly affect the hearing status of children, resulting in delayed language acquisition, and resulting in academic difficulties. As a result, it is crucial for tympanometry to be part of every pediatric audiology test battery.
Otitis media may not be as prevalent in adults and the elderly, however, this does not mean that it is impossible for adults and the elderly to have middle ear infections. In addition to this, there are multiple conditions that can affect the middle ear. Traditionally, audiologists would assess air and bone conduction in patients in order to determine the site of lesion (i.e. where exactly is the issue in the auditory system?). Because of the subjective nature of pure tone audiometry and the test protocols used in clinics, it is important to verify or interpret air-bone gaps, or lack of, with tympanometry. For example, if screening adults down to 25 dB HL with air conduction only, a ‘slight’ conductive loss/ deficit might be missed. It is a fact that hearing loss associated with otitis media typically ranges between 15-50 dB HL across frequencies of 0.5-4 kHz. Thus a screening pass down to 25 dB HL should still be verified by tympanometry.
KUDUwave™ Pro TMP
The use of tympanometry should not eliminate the traditional pure tone audiometry test. In fact, it should be used in conjunction with pure tone audiometry, otoscopy and other test equipment. Information from other tests, including that from tympanometry, allows for restricted referrals and appropriate management of audiological patients.
Traditionally, tympanometry is unilateral – meaning one can only test one patient ear at once. In addition to this, the equipment is normally separate from the clinician’s pure tone audiometry system, and may be bulky. This can make it difficult or inconvenient to provide mobile audiology services.
The KUDUwave, a boothless audiometer, has recently integrated tympanometric functionality within the KUDUwave system. This tympanometric configuration was recently validated and reported in an international peer reviewed journal. This tympanometer has several more benefits;
- Ability to assess two ears simultaneously (bilateral tympanometry)
- Integration with diagnostic pure tone audiometry
- Integrated with acoustic reflex measurements
- Has two tympanometers, which allows a hearing health clinic to continue functioning should one tympanometer stop functioning
- Effective first-time probe sealing as a result of KUDUwave TMP placement (see image below)
Tympanometry should be part of every hearing health clinic. Whether for diagnostic audiology services, school-based hearing screening, or for occupational health (i.e. industrial audiology). It is a necessary investment that is cost effective in the long run (i.e. restricted referrals and appropriate management).