As we have seen, the measurement of acoustic immittance and. J Speech Hear Res. Jun;30(2) Acoustic-immittance measures in normal ears. Wiley TL, Oviatt DL, Block MG. Erratum in J Speech Hear Res . PDF | On Jan 1, , Wiley and others published Basic principles of acoustic immittance measures.
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The early s were an exciting time for diagnostic audiology. The intriguing equipment and test procedures, coupled with the supporting documentation from Jerger, caught the attention of most all clinicians. It was not long after the ZO impedance bridge arrived that the Grason-Stadler company came out with their Model admittance unit. Were we measuring impedance or admittance? Were we using a bridge or a meter? These workshops were held in dozens of U.
Klar soon came out with his own impedance equipment, the American Electromedics. Some of you might remember the automatic pediatric tympanometry unit which also was soon available from acoudtic company, which had the novel idea of having a car printed on the recording paper, that then moved when a seal of the ear canal was obtained.
A great distraction for a squirming kid. That was the world of immittance audiometry from the s, but what about now? We of course still do tympanograms and acoustic reflex measures, but do they still have the diagnostic weight that they did then? And what is new? Things must have changed in 40 years? To answer all these questions, acousstic have our 20Q guest author, Lisa L. Hunter on otitis media, pediatric audiology and diagnostic audiology. Hunter is a graduate and former faculty member of the University of Minnesota and in the early s she developed and directed the AuD program at the University of Utah.
Lisa has chaired numerous committees for national professional organizations and currently is a member of the Board of Directors of the Accreditation Commission for Audiology Education. This 20Q is just a glimpse of Dr. To browse the complete collection of 20Q with Gus Mueller articles, please visit www. Even before I was born! There are reports of acoustic reflex testing using an impedance bridge going back to Otto Metz in Denmark in You may have heard of or read the classic papers by Jerger in early s, and later by Green and Margolis and Gelfand where the different acoustic reflex patterns were explained, illustrating how measured might be used for clinical diagnosis of different pathologies.
Tympanometry, as we know it today, was introduced by some other Danish researchers, Terkildsen and Scott-Nielsen in who developed the first pressurized acoustic immittance instrument, the Madsen ZO Now that was a fine piece acouetic hardware, all polished wood and heavy metal! Much of what we do today has been around for over 50 years. But I keep thinking that there must be some changes and clinical refinements that have been made since I was in graduate school?
There definitely have been, and these advances are now available commercially. Is that still okay? So, for detecting OME or other problems that increase stiffness of the system, add width to your measurements. Norms for tympanometry measures are available for infants, children and adults in Table 1, which is averaged from studies reviewed in Hunter and Shahnaz Normative measures for tympanometry, compiled from multiple studies reviewed in Hunter and Shahnaz, How do you report these findings to the referring physician?
An overall normal or abnormal interpretation is the clearest way to report to neasures physician, immittxnce it is fine to use A, B, C etc. The tympanogram width is abbreviated TW, and is reported in decaPascals daPa. This should be interpreted in addition to static admittance in mmho, equivalent volume in cc, and peak pressure in daPa. I get a lot of requests to do tympanometry on newborns and infants. Is there any other test I can use instead?
Low-frequency tympanometry assumes that you are measuring in a hard-walled cavity the ear canal. So the low-frequency sound energy gets measurrs by those super-compliant tissues. Norms are available from Margolis and colleagues or Kei et al.
Better yet, you can use wideband absorbance — a new test that appears to be even more sensitive and specific than tympanometry in newborns. A new way to measure middle ear function is called wideband reflectance or absorbance, or if pressurized, is known as 3D wideband tympanometry.
An example is shown in Figure 1. Reflectometry is not as sensitive as tympanometry, so it is not recommended as a diagnostic measure. In contrast, wideband absorbance measures sound energy absorbed by the eardrum and middle ear. It uses clicks, and can analyze how sound is absorbed from Hz up to about 10, Hz.
It can be done with pressure, just like tympanometry, which then gives us 3 dimensions. Wideband acoustic reflexes can also be measured with this technique. So far, results are very promising in studies for infants, children and adults. A wideband tympanogram and an averaged tympanogram between kHz, showing how they relate to one another.
This was recorded in a normal ear using the Interacoustics Titan Denmark. Yes, in order to use the new absorbance technology, new equipment is necessary. There are instruments available that are combined with OAEs from Interacoustics, which are pressurized and include the 3D tympanograms, and Mimosa Acoustics, which tests wideband reflectance and absorbance at ambient pressure.
Both wideband instruments are now FDA approved. They can provide more sensitive results for a wide range of pathologies such as idiopathic conductive or mixed hearing loss, suspected otosclerosis, ossicular disarticulation, OME, and other middle ear problems. The test is more sensitive because the entire audiometric frequency range is assessed by employing clicks with sophisticated calibration and analysis. Getting back to traditional tympanometry, are Eustachian tube function tests used anymore, and are they accurate?
One basic measure of Eustachian tube ET function is the peak of the tympanogram, known as tympanometric peak pressure, or TPP.
Other patients may complain of ear pain or discomfort, acoustc during conditions that require active ET opening, such as airplane take-offs or landings, or diving. ET dysfunction is related to acute or chronic otitis media, especially in children. Detection of these problems is the main reason for doing ET function tests, such as measuring changes with Toynbee or Valsalva maneuvers, or after swallowing or sniffing.
Studies of Immittanxe function tests have shown that these tests can tell you if the ET can open under active maneuvers, but they do not accurately predict patients who will have future OME problems Straetemans et al. To detect a patulous ET, you can look for pulsatile admittance changes on the tympanogram or during reflex testing. ET function testing can be tried, and used to confirm whether the patient can open the ET actively.
Just remember that it has no prognostic value to predict OME. It also would not provide value for treatment beyond immmittance is gleaned from tympanometry. One last question about tympanometry.
It seems like it is being done by all kinds of providers, such as nurses in general practice offices and even hearing aid dispensers. Questions like this pop up on listservs all the time, and really make us sigh, navel gaze and wonder if we still matter. Are we defined by the tests we do, or by our intellectual input into these tests? Hearing and middle ear screening tests have been conducted by many non-audiologists for many years, and we could counter-argue mrasures these efforts actually help our profession more than hurt us.
Personally, I think we should encourage the ethical and responsible use of screening tests by physicians, nurses, speech pathologists and dispensers to identify and refer patients for appropriate care by audiologists and otolaryngologists. Such screening tests can identify patients for further assessment, ensure that patients with potentially treatable conditions such as cerumen impaction and middle ear problems receive medical care prior to hearing aid dispensing, and acouwtic increase recognition that an immtitance provides a higher level of care than just doing an audiogram or tympanogram.
We should train and use support personnel to do screening tests whenever possible so that we can use our valuable time to provide more in-depth testing, counseling and treatment, thereby increasing the impact of audiology in ways that matter most.
Acoustif hope my career ackustic not be defined by my ability to do a tympanogram.
Acoustic Immittance Testing
Am I correct in saying that we still use these measures to help identify retro-cochlear pathology? A table showing normal acoustic reflex thresholds by frequency and degree of hearing loss can be found in Gelfand, Schwander, and Silmanand has been adapted in Table 2. There also is a chart in many textbooks such as shown in Table 3 that shows reflex results for various disorders, from the middle ear to the cochlea, on up qcoustic retrocochlear, including VIII nerve pathology, VII nerve and brainstem pathology.
Understanding reflex test results is kind of like pattern recognition. The chart helps you figure out why the reflex can be absent in one ear and present in the other ear, or absent with the stimulus in one ear and present with the probe in that same ear. Understanding reflex pathways helps you figure out why these patterns happen — they are not random!
In the case of a right-sided retrocochlear pathology, the reflex is elevated or absent depending on size and location of the lesion when the stimulus is delivered to the affected right ear. Contrast this pattern with a right-sided VII nerve lesion, in which the reflex is absent when it is measured with the probe in the affected right ear.
Patterns of reflex abnormalities, referenced to the stimulus ear modified from Hunter and Shahnaz, Results that are variable depend upon severity of the condition or hearing loss. There is only one correct way. i,mittance
Acoustic-immittance measures in normal ears.
You report for the ear that is stimulated. The chart we just talked about makes it obvious which is the stimulus ear and which is the probe ear, so it should all be crystal clear! Is it true that if you do ipsilateral reflexes, there really is no reason to do contralateral?
Well, it depends on the situation.
Acoustic Immittance, Absorbance, and Reflectance in the Human Ear Canal
Tympanometry is a better choice to rule out conductive hearing loss. Unilateral retrocochlear or facial nerve issues are rare in infants and children. Ipsilateral reflexes will give an answer regarding the possibility of cochlear loss or auditory neuropathy, combined with OAE and ABR. However, in working up new cases of hearing loss in children or adults and in complex or unclear cases at any age, contralateral reflexes are needed. In suspected neural involvement, and in working up cases of sensorineural hearing loss of unclear origin, both ipsilateral and contralateral reflexes are often helpful.
Starting with ipsilateral reflexes, and continuing on to contralateral if ipsilateral reflexes are abnormal or do not fit the other results is a good back-up plan. And, there certainly are neurologic conditions such as multiple sclerosis or myasthenia gravis, where contralateral reflexes may be elevated, or delayed in latency, when both right and left ipsilateral look good.
What about when I have bilateral flat tympanograms – any reason to do reflex testing then? So when I conduct either contralateral or ipsilateral reflex testing, should I test at Hz?