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In conjunction with the 2009 introduction of the Interacoustics Titan—a handheld wireless, Bluetooth enabled clinical impedance bridge that allows quick screenings as well as comprehensive diagnostic tests—we thought it would be useful to review common middle ear measures, as well as improvements and upgrades available via the Titan.
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The RECD accounts for the difference in decibels (dB) across frequencies, between the SPL measured in the real-ear and in a 2cc coupler, produced by a transducer generating the same signal.
The RECD ensures that information about the patient’s occluded ear canal characteristics is obtained and enables you to convert this information from dB HL to dB SPL. The RECD may also be utilized in the estimation of 2cc coupler targets which are not only useful in the verification process but also when selecting a suitable hearing aid by means of the manufacturer’s data sheets (Pumford & Sinclair 2001).
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In air conduction audiometry a test signal is presented to the test subject by earphones and the test subject responds to the signal by pressing a client response button. The audiometric threshold is defined as the lowest intensity at which the client is able to detect the test signal 50% of the time. The purpose of air-conduction audiometry is to establish the hearing sensitivity at various frequencies. The test provides information about the conductive and sensory systems of hearing but cannot distinguish between abnormality in the conductive mechanism and sensorineural mechanism.
Most people acquire hearing aids because they or their relatives experience that they have trouble hearing speech. Speech audiometry has the advantage of employing speech signals and is used to quantify the client’s ability to understand everyday communication. It examines the processing ability and can be useful to investigate whether the processing is affected by disorders of the middle ear, cochlear, auditory nerve, brain stem pathway, or auditory centres of the cortex. Speech audiometry can be performed using a number of tests. To mention a few the SRT (Speech Recognition Threshold) refers to the level at which the client can repeat 50% of the presented words correctly. It serves as a check of the pure tone audiogram, gives an index of hearing sensitivity for speech and helps determining the starting point for other suprathreshold measures such as WR (Word Recognition). WR is sometimes also referred to as SDS (Speech Discrimination Scores) and represents the number of words correctly repeated expressed in percent.
Counselling is a crucial part of the audiological evaluation. It provides both relatives andpatient with a better understanding of the measuring results, why they may have beenexperiencing problems, and what they are likely to gain from hearing aid amplification. Thismay later on have a considerable influence on their motivation to use the instruments.In the AC440 module Interacoustics provides two dedicated counselling tools: The HearingLoss Simulation (HLS) and Master Hearing Aid (MHA), which address the needs of relatives andthe patient respectively.
There are many different demands and wishes regarding how an audiometer should bothfunction and appear depending on the specific situation and national standards.One of the greatest advantages of the Affinity and Equinox AC440 module is the high flexibilityenabling the individual clinician to tailor the system according to their specific preferences. Itpermits the creation of an unlimited number of personalized test settings and functions fordifferent purposes and/or for different clinicians working at the same location. These numeroussetup options can be very helpful and time saving in the daily work in the clinic.
Helping the University of Canterbury provide students with solid hands-on experience to diagnose vestibular disorders - or dizziness and balance problems - is behind one of the latest Oticon Foundation grants.
Audiology students are now benefiting from the use of an Interacoustics Videooculography System in the university's Vestibular Disorders Clinic.
"We've traditionally taught the theory side of our Vestibular Disorders courses in house, but student's experience with this type of diagnosis equipment was limited to clinical placements at Christchurch Hospital," says Dr Greg O'Beirne, Senior Lecturer in Audiology. "Having this equipment in our clinic greatly enhances the clinical education of our students and better equips them for practice in vestibular diagnosis."
The equipment has allowed the establishment of a Vestibular Disorders Clinic which:
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The Affinity is an easy and straightforward solution that takes care of all clinical needs.One of the greatest advantages is the high flexibility which permits the creation of an unlimitednumber of personalized protocols for different purposes and/or for different audiologistsworking in the same clinic. This enables each individual clinician to setup the Affinity exactlythe way they wish using the specific tests, stimuli and settings they prefer. These personal testprotocols can swiftly and easily be chosen at any time accommodating the need for speed in abusy clinic.
Decisions regarding vent size are crucial in the fitting process and must be selected carefully to ensure that the gain target is reached and, where possible, without occlusion. Small vents or entirely closed fittings are usually recommended for hearing losses that require high levels of gain especially in the low frequencies. They have the advantage of minimizing problems with feedback squealing as the signal has limited possibilities to leak back into the microphone. However, when the ear canal is completely occluded by a closed fitting, people with thresholds better than approximately 40 dB HL in the lower frequency range are likely to experience discomfort from their own voice. It will sound unnatural, as if they were speaking in a barrel. Closed fittings may introduce this occlusion effect and make the patient feel “plugged up”.
Visible Speech (VSP) is a term widely used amongst manufacturers of various systems todescribe a kind of verification-, fitting-, counselling- or sales tool.
Interacoustics VSP440 is a tool to help the dispenser explain the meaning and benefit of ahearing aid. It has a comprehensive layout to assist in explaining and makingrecommendations. Visible Speech can also present reasons for why advanced nonlinearhearing aids are recommended over conventional hearing aids and help to explain why abinaural solution is preferable in most cases.
The auditory steady-state response (ASSR) can be thought of as an electrophysiologic response to rapid auditory stimuli. The goal of ASSR is to create an estimated audiogram from which questions regarding hearing, hearing loss, and aural rehabilitation can be answered.
Evoked potentials are now a routine part of the audiological world. They are objective and reliable and enable us to estimate the audiogram where it would be impossible by any other means. Testing is also straightforward. One electrode behind each ear and another on top of the head connect the patient to the test equipment. During the test, the audiologist adjusts the dials and after a while we have an estimated audiogram.
Simple? Well, not quite. The electrical signals from the cochlea and auditory nerve are very small compared to other electrical signals in the head and body and around the room. Electrode placement, patient state and several other factors play a role in obtaining accurate results. But given suitable conditions, the test equipment decides the outcome.
So how do we separate the hearing signals from the electric noise that surrounds them? There are a variety of techniques, each with their own acronym. The two that matter most in this article are ABR and ASSR (also known as SSEP).
In ABR (auditory brainstem response) we stimulate the ear with a toneburst and measure the response plus noise at the electrodes. We repeat this thousands of times and add the results together. The noise, being random, cancels out and the response appears as notches on the electrical waveform. The notches get smaller as we get closer to the hearing threshold.
In ASSR (auditory steady state response) we do something similar, but now the stimuli are very rapid. We know that responses to the tonebursts will occur at the same repetition rate as the stimuli, so we do amplitude and frequency analysis to find them. By using four frequencies in the stimulus, each at a different presentation rate, we can test four frequencies in each ear at the same time. Electronics and mathematics take care of the calculations, but the result is a good estimate of the audiogram.
Recently, Interacoustics® has patented two advances that take ASSR to a new level. We have redesigned the stimulus to adjust for cochlear delay. This means that more hair cells fire at the same time for a given stimulus level, producing greater electrical activity and a better response. This is especially useful near hearing threshold. And when looking for target frequencies in the response, we also examine their harmonics to further improve the distinction between signal and noise.
Put these advances together and you have a system that can approximate the audiogram in about half the time required to do the same thing using traditional ASSR or ABR. At present ASSR is used to perform diagnostic audiometry on babies referred from screening procedures, but it isn’t difficult to see it finding other applications in future.
During the last year, newspapers around the world have reported that surveys indicate that excessive use of MP3 players may damage the hearing.
The dangers of MP3 playersThe problem with MP3 players is that the volume on many of them can be turned up to more than 100 dB HL. As many of these music players are used in noisy surroundings and with typical in-the-ear headphones that do not completely attenuate the ambient noise, higher listening volumes are typically used.
With batteries on a typical MP3 player lasting up to 12 hours many young people listen to the music at very high levels for extended periods of time, which may lead to temporary hearing loss or in the worst case permanent hearing loss.
Measuring temporary and permanent threshold shiftWhen the ear is exposed to high music for long periods of time, the hair cells might be damaged and lead to temporary or in the worst case permanent threshold shift.
According to researchers at Aalborg University, Denmark, measuring OAEs (otoacoustics emissions) before and after noise exposure suggests that OAE is a more sensitive method than pure-tone audiometry and therefore might be a method for early identification and monitoring of hair cell damage which in turn may lead to hearing loss.
OAE tests to assess the consequences of high level sound exposureThe greatest effect of a temporary hearing loss due to noise exposure is recorded 2 minutes after the exposure. If the hearing improves after some time the patient is suffering from temporary hearing loss. If the OAEs do not improve by days and weeks the patient may have a permanent hearing loss.
With the DPOAE20 system from Interacoustics® it is possible to use the I/O and high resolution versions of the DP-gram tests to make a very detailed recording of OAE, which may be helpful in assessing the consequences of high level sound exposures from e.g. MP3 players. This can be done also as an educating tool, demonstrating the consequences of loud MP3 use for people at risk for this type of hearing damage.
Sources: “Digital music craze stores up ear trouble for iPod fanatics”, Scotland on Sunday, 8 May 2005, by Richard Gray, ”Really?”, New York Times, 6 September 2005, by Anahad O'connor, “Repeatability of DPOAEs and their vulnerability to over-exposure”, Conference Article from DAGA 2003 in Aachen, Germany, by Reuter, Karen : Ordonez, Rodrigo : Hammershøi, Dorte
Testing the sacculus has always been the weak link in traditional balance investigations. VEMP (Vestibular Evoked Myogenic Potential) recording is the only clinical test that evaluates Sacculus function in both ears individually.
In this test, loud stimuli (min. 85 dB nHL) are used to evoke a response in the Musculus Sterno-cleidomastoideus. This reaction, known as the VEMP (vestibular evoked myogenic potential) occurs in the region of 13-23 ms after stimulus.
To increase tonus in the responding muscle, the suppine patient raises their head from the bed or, if sitting, turns their head to the non-stimulated side. A single test takes 30 seconds with several tests done during a session.
With Interacoustics® systems the VEMP ratio is calculated automatically and you can also record from both sides simultaneously while the patient is supine. This is useful because many patients have difficulty maintaining their head in the raised position.
Interacoustics® can offer several options that include this test, either as a dedicated VEMP system or as part of a complete balance-testing system.
Video-oculographic recording of eye movement has been shown to be a highly effective non-invasive technology for evaluating eye movement.
Real-Ear-to-Coupler Difference (RECD) accounts for the difference in decibels as a function of frequency between sound pressure level (SPL) at a specified measurement point in the ear canal relative to the SPL measured in a 2cc coupler for a specified input signal. Put less formally the RECD equals the difference (in dB) across frequencies, between the SPL measured in the real-ear and in a 2cc coupler, produced by a transducer generating the same input signal (Pumford & Sinclair 2001).
First released in 2001, the AT235h clinical middle ear analyzer (the “h” indicates the additional high-frequency probe tones) has a proven track record for reliability and a solid reputation worldwide. This year a number of features have been updated which make it an extremely attractive choice for both clinical and screening purposes.
With manual and automatic test modes, programmable test sequences for tympanometry, acoustic reflex and reflex decay testing, plus intelligent pump and probe features, it has become the ideal tool for impedance testing in most situations. It can even function as an air-conduction-only, pure tone screening audiometer when needed.
The AT235h is designed for speed and convenience:
The intelligent pump system automatically compensates for slight pressure leaks, completing the test for as long as the required pressure can be maintained. It also modifies pump speed according to tympanogram gradient, ensuring accurate peak compliance readings even at high speed. And there is a manual mode for those who prefer it.
The unique exchangeable probe system allows a screening (pencil) probe to be replaced with a clinical probe in seconds. The AT235h will automatically recognize the change and adjust the calibration values.
The AT235h has two independent programmable automatic test sequences. You can program these in many ways. One example would be where the instrument was used as a screening device and then later for clinical work. Protocol A would be for screening; protocol B for the more extensive clinical tests. The programmable reflex protocols allow presentation levels to be set at fixed levels or to increase until threshold is identified. Stimuli can also be presented in a defined sequence (e.g. to display reflex growth). Ipsi- and contralateral reflexes can be tested in any order and with pure tones or noise. Reflex decay can also be tested ipsi- or contralaterally. In fact, more than 40 reflexes can be recorded per ear. And, with the press of a button, you can do reflex testing manually. Tympanogram and reflex test results are displayed simultaneously.
For young children, there is a Moving Train function to catch their attention while tests are running.
Two tests of Eustachian tube function (one for intact and one for perforated tympanic membranes) are included, with patient instructions conveniently given on the display.
The AT235h has a built-in thermal printer for immediate printout and now has a standard USB socket for even easier connection to a PC. It is fully compatible with the NOAH database and handles data transfer and storage with ease.
At 2.8kg (6lbs) the AT235h is easily portable. And when you travel, the AT235h has a hard-walled lightweight case for the unit and all its accessories.
It isn’t difficult to see why the AT235h is so popular!
Audiologist Aysen Erdil does a lot of voluntary work in Turkey using Interacoustics equipment. In 2004 she tested children in Turkish schools and in the fall of 2006 she will be testing children and babies in small villages on the Turkish border. Therefore, it was not unusual for her to decide on testing babies' hearing in Nepal while trekking in the Himalayas in early 2006.
Testing Sherpa babies 5140 meters above sea levelWhile trekking in the Himalayas with a friend, the Turkish audiologist Aysen Erdil brought along an OtoRead OAE screener from Interacoustics®. Whenever she found a baby on her way she checked its hearing. “It was minus 20 degrees Celsius at night, so I had to keep the OtoRead with me in my sleeping bag in the tent,” she explains.
The baby in the picture was a 23 day old boy of the Sherpa people whom Aysen Erdil tested. He passed the OAE screening on both ears, which naturally made his mother very happy. The picture was taken at Gorak Shep 5140m above sea level, the highest point in the world with a settlement. The Sherpa are the local people who live in Solu Khumbu Valley in the Himalayas.
Increasing awareness of newborn hearing screening in NepalA national hearing screening program is already in place in Turkey. In fact, the hospital where Aysen Erdil works is in a leading position on this matter. Therefore, she wanted to demonstrate the OAE screener to her Nepalese colleagues. On her way from to Gorak Shep (near Everest Base Camp) Aysen Erdil visited the hospitals at Lukla, 2840m ASL, and at Namche Pazar, 3440m ASL.
Voluntary work inspired by "Medecins sans frontieres"Each year Aysen Erdil does voluntary work for one week in remote parts of Turkey inspired by the work of “Medecins sans frontieres”.
The Interacoustics® distributor in Turkey, Erisci, always helps her by supplying the necessary equipment, which was MT10 last year and the OtoRead this spring. The picture below was taken in 2004 when Aysen Erdil was testing with the MT10 middle ear analyzer at a school in Damal, a tiny village in far-east Turkey.
This September (2006) she and a group of voluntary doctors are going to visit 14 small villages on both sides of the Turkish and Georgian border to test children and babies.
Source: Aysen Erdil holds a BA in psychology and a MSc. in audiology. She has worked at the Hacettepe University Hospital in Ankara and now works for Amerikan Hastanesi in Istanbul, a non-profit general hospital. It is owned by a private foundation and this year is its 86th birthday.
Since its launch in February 2007 Interacoustics ASSR has proven its reliability worldwide.
Test times down to 20 minutes are not unusual and the estimated audiogram often shows remarkably precise results. At present Interacoustics ASSR is the best ASSR system on the market. FDA recently approved the system for the US.
Among the many reported cases are four from Russia, Denmark, Sweden and Germany. They and others show reliable and quicker estimated audiograms than the competition.
Case 1: Hospital SwedenThe hospital needed to change 3 systems and wanted to test the Interacoustics ASSR. The first test on a 20 year old man showed a result after 25 minutes on all frequencies at 10dB. The next was a 50 year old man who was supposed to have no hearing in his left ear. After 30 minutes, Interacoustics ASSR showed a hearing loss of 55-60 dB on the left ear – which the man confirmed afterwards as the actual hearing loss.
Case 2: Hospital DenmarkTwo children (aged 2 and 4) were tested for hearing loss. EcochG tests (the hospital’s gold standard) had indicated hearing levels at around 80 dbHL. The hospital normally used a competing product for four-frequency threshold estimation, but wanted to test with Interacoustics ASSR.The competing product showed very inconclusive threshold estimates – so they were surprised when Interacoustics ASSR showed thresholds consistent with the EcochG. They were also pleased with the speed and accuracy during the demonstration. They now rely on Interacoustics ASSR for their four-frequency follow up to EcochG.
Case 3: Hospital RussiaAn ENT specialist obtained an audiogram from a 5 year child. However, he was much in doubt if the girl pressed the button at the right time. Interacoustics ASSR estimated the audiogram at better thresholds, especially at the higher frequencies. According to her mother, the girl could understand quite a lot of speech and the ENT specialist confirmed that the Interacoustics ASSR estimates were almost certainly closer to the real audiogram. So Interacoustics ASSR delivered a more accurate audiogram than traditional measurement for a difficult to test patient.
Case 4: Hospital GermanyTwo girls (aged 2 and 3) underwent surgery under general anesthetic. Interacoustics ASSR was used to check post operative hearing while the patients were still anesthetized. After 15-20 minutes testing they obtained results down to 15dbHL, confirming the success of the surgery.
The word pc-based can be misleading. Perhaps pc-integrated would describe it better. Either way, it’s important to understand that the audiometric signals are not created in the PC. What has happened is that we have divided the functions of an audiometer into two groups. In one group are the electronics that create and deliver test signals. These are state-of-the-art, as ever, but now fit into a compact, beautifully-designed unit that will grace any sound-proof booth or office. In the other group are the switches and dials. These have been moved to the PC screen or you can use a specially-designed audiometric keyboard.
The change is driven by the increasing need to automate and integrate audiometric information into record systems, typically a database. The software on the PC is the binding link, automating transfer of data between the audiometer and the database where it is available for other uses such as hearing-aid fitting or comparison with previous audiograms. Having to enter data manually is a thing of the past.
But there is more to it than that. Bringing the PC into the system gives the audiologist greater control over how their system is set-up. The audiologist has a set of requirements when they place their order. These become protocols in the software and are delivered with the system. But the audiologist can adapt these protocols at any time, create new ones, even change how switches appear on the screen or customize reports on the printer. Anyone who has travelled in the audiological world knows how much individual preferences matter. This is part of bringing control closer to the people who use the equipment.
We call our system Equinox to give the idea of balance between two needs: complex and precise control over the test signals and freedom of use for the audiologist. That reflects the driving philosophy here at Interacoustics. And it seems to work!
Visible Speech allows the dispensing professional to record, demonstrate, and verify theappropriateness of the hearing aid fitting while reviewing, demonstrating, and explaining theprocess in terms the patient understands—based on human speech and the SpeechIntelligibility Index.