Blog

#1 Wide Band Tympanometry and Absorbance

2021-05-12T10:29:35+00:00

Welcome to Interacoustics Australia’s first ‘Audiology in Brief’ series.

We will be bringing you brief snippets of education on a range of Audiology topics. Easy to digest and quick to read, we hope these articles will entice you to learn more on the topics presented and expand your audiological knowledge.

Audiology in Brief #1 - Wide Band Tympanometry and Absorbance

You’ve known about Wide Band Tympanometry and Absorbance for a few years now. We even have some significant influencers researching it in Australia, so what’s it all about?

We know Audiologists love a good acronym, so let’s break down the main two you hear when we discuss wideband.

WBT – Wide Band Tympanometry and WBA - Wide Band Absorbance

The ‘wideband’ part of the name Wideband Tympanometry or Absorbance refers to the stimulus, which is a click i.e. a broadband sound.

The tympanometry part is just that, a standard tympanometry test but using the wideband stimulus, giving us a tympanometry view from 226 to 8000Hz. Not just at 226Hz like traditional tympanometry results.

The ‘absorbance’ part of the name refers to how effectively the energy from a click sound is transmitted through the middle ear system.

In a bit more detail …

Wide Band Absorbance (WBA) is measured on a scale from 0 to 1, where 0 is no incident sound energy absorbed, and 1 is all incident sound energy absorbed.

WBA is a measure of the effectiveness of the middle ear (to absorb sound) as a function of frequency. It has been shown that measuring middle ear function across frequencies (instead of just at a single frequency, or a handful of frequencies as in traditional tympanometry) can give clinicians a greater understanding of how certain disease processes affect the middle ear¹.

If I were to purchase a WBT device, what will this technology do for my patients?

In Paediatrics:

Differentiate negative pressure tympanometry results and determine whether the middle ear is fluid or air filled - not just a Type B tymp anymore!

Get results in restless and noisy kids with the wideband averaged tymp.

Examine the middle ear performance even with perforations or grommets.

How about in adults or difficult to test populations:

All of the above is still relevant in adult populations, plus there is some great research coming out about how WBA can assist with Meniere’s diagnosis. You can contact us for a list of article links. Here’s one to get you started:

Ishizu et al (2018) Diagnosis and following up of Ménière’s disease using multifrequency tympanometry—Cutoff values and temporal changes in measurements in Auris Nasus Larynx; 45 (2018) 81–87.

https://pubmed.ncbi.nlm.nih.gov/28602229/

So, what could this technology do for your business?

As clinical pressures increase and recent times have shown, less face to face contact is desirable from a health perspective; we are increasingly seeing the desire for faster and more clinically significant objective testing results. The WBT and WBA testing measures on the Titan allow you to quickly and efficiently diagnose middle ear pathologies unlike you have been able to before.

Showcasing your clinic’s advantages to your referral base is a big draw card for clinics utilising this technology. Adding to this, the increasing impressive evidence of the added Meniere’s diagnosis assistance, means we are looking forward to seeing greater specificity over traditional more invasive EcochG (Electrocochleography) tests for Meniere’s confirmation.

Keen to learn more?

The Interacoustics Academy has an array of helpful resources for clinicians. Please use the links to navigate to their website. We suggest starting with one of their e-Learning courses on WBT: https://www.interacoustics.com/academy/training/academy.

You can of course contact an Audiologist at Interacoustics Australia on 02 88991200 or info@interacoustics.com.au.

References:

¹ – Interacoustics Academy – Taken on 15/7/2021: https://www.interacoustics.com/academy/faq/tympanometry/what-exactly-is-wideband-absorbance.

#2 Dynamic Visual Acuity (DVA)

2021-10-12T10:40:06+00:00

Audiology in Brief #2 - Dynamic Visual Acuity (DVA)

Why has your patient’s world gone blurry when they move their head?

How can you quantify this and monitor their rehabilitation?

Every day when we walk, run, and move our head, we want to maintain a clear picture of the world around us. What mechanism drives this?

Try this little experiment:

First – hold your thumb up 30cm in front of you and keep it still. Now move your head quickly back and forth, looking at your thumb. How clear is it?

Now – hold your thumb up again, and this time keep the head still and move the thumb back and forth very quickly. How clear is it?

In which situation is your thumb clearer? If your Vestibular Ocular Reflex (VOR) is working, it should be the first one.

The VOR’s primary function is to maintain visual acuity during movement.

In a normal functioning person, with the head is at rest, the neural firings from both labyrinths are equal. This lets the brain know that your head is not moving.

When the head moves to one side, neural firings increase to that side, and decrease on the opposite side. To keep the world from going blurry, the eyes move at the same speed as the head but in the opposite direction. This is controlled by the Vestibular Ocular reflex (VOR).

So, what happens in the case of a vestibular lesion? Straight after a lesion, the neural firings on the lesion side decrease, therefore the person perceives as though their head is moving to the opposite side even when their head is still. The patient feels quite dizzy and can have spontaneous nystagmus. However, this only lasts a few days with the body compensating quickly when the head is still. The patient will start to feel better as long as they don’t move their head. Over time with more compensation the patient will also start to improve with their head moving, this is Dynamic compensation.

So, how can you objectively assess the VOR system in response to head movement?

To assess VOR, you need to assess the patient with their head still and compare to while in motion. Using a device which tracks head movement with an IMU sensor, the patient is asked to look at optotypes and judge which direction it is pointing. The size of the optotype is decreased until the patient can no longer make a correct choice. This test is done with the head still and then while the head is in motion (horizontal and vertical planes). The computer measures the smallest optotype the patient can correctly identify. This can be done as a baseline test and again during the rehab process.

This information can be used to determine the level of vestibular compensation and to measure any improvements with rehabilitation.

If you already have the Visual Eyes system, DVA can be added as an additional test.

Keen on vestibular testing but don’t have the gear?

Why don’t you try a bed side measure first? You need very little equipment:

1. Snellen eye chart
2. Metronome app on your smart device

Have the patient sit in front of the eye chart with their head still and read the smallest line they can see (glasses can be worn, it is not an eye test). This is the baseline. Then moving their head at 2 cycles per second (2Hz), have them read the smallest line they can see (dynamic). In a normal patient, the difference between the baseline and dynamic visual acuity should be two lines or less. (In some patients with vestibular loss, it can be more than 6 lines).

Contact our Audiologists/Product consultants for more information.

#3 Real Ear Coupler Difference (RECD)

2021-11-10T10:44:52+00:00

Audiology in Brief #3 - Real Ear Coupler Difference (RECD)

With Covid-19 affecting the way most of us practice in our clinic, we need to look at other ways to fit and validate hearing aids while reducing the amount of clinic visits.

What is involved in RECD measures?

RE- Real Ear - takes the patients ear canal into account (acoustics and anatomy of their ear) and calculates how it is different to the coupler: CD - coupler difference. This RECD measure is used to fit the hearing aid in the test box.

Procedure of RECD

1. Run a measure in the test box with a REM headset, RECD tube attached to a 2cc coupler

2. Run a measure in the ear with the REM headset with either their own mould (if available) or SPL tube

The above 2 measures can be done at the test appointment. (A hearing aid is not needed for this measurement)

3. Step 2 minus step 1 gives you a RECD measure which can then be taken into account when fitting the hearing aid in the coupler. The hearing aid can be adjusted in the coupler without the patient present and then sent to them.

How does it help reduce the amount of clinic visits?

For previous hearing aid users, the “fitting” appointment can be done without the patient present as all the information is available to obtain a best fit and the patient would already be familiar with how to use a hearing aid. Any follow-up appointments can be done via a video appointment if needed, especially now that the latest hearing aids also allow for remote adjusting.

What other applications can RECD measure be used for?

Home visits
Young paediatrics who are unable to sit through a whole fitting procedure
Profound losses where REM is difficult for very tight-fitting moulds
Adults with special needs who are unable to be present for the fitting procedure
To verify multiple features of the hearing aid.

The RECD procedure allows for a quick measure on the patient and then all the adjustments can be performed in the coupler.

Different styles of hearing aids can be fitted in the coupler using different adaptors, most of which you would be familiar with. There is now a new adaptor for couplers for thin tube and custom fittings. These are called Aidaptors™.

These adaptors replace the old acoustic putty (“Blutak”) that audiology clinicians have traditionally used for coupler measurements. What’s even better is that the Aidaptors were designed right here in Australia, by Matthew Callaway and Doug Lloyd.
The Aidapter™ from Interacoustics is a unique silicone piece that clicks onto the HA-1 adapter. Compared to putty, the Aidapter™ provides a good acoustic seal and standardizes the coupling, ensuring repeatable coupler measurements. The Aidapter™ also eliminates the hassle and hygienic issues of using acoustic putty.

The Aidapter™ is compatible with all hearing aid fitting devices from Interacoustics including the Callisto TBS10, TBS25, Affinity 2 and new Affinity Compact.

To place your order please purchase through Sanibel Supply
Item number: 8525568 (Set of 3) – $70 ex GST RRP

For more information, please click here to watch this 4-minute video on Performing Coupler Fittings using the Affinity Compact (RECD).

Also, contact our Audiology/Product Consultants if you have any further questions at info@interacoustics.com.au

#4 CROS/BiCROS Fitting

2023-01-28T09:29:27+00:00

Audiology in Brief #4 - CROS/BiCROS Fitting

The presentation of aidable single sided hearing loss is not as common as the classic symmetrical sensorineural losses seen in the clinic. Often a refresher is needed on these types of fittings.

The goal of the CROS/BiCROS fittings is to ensure that the signal on both sides of the head sound similar. If a client has worse hearing in one ear, we want to ensure that the client can hear if someone is speaking on the worse side.

CROS stand for the Contralateral Routing Of Signal: It is good for unilateral hearing losses, single sided deafness. It is a useful form of amplification when there is a severe/profound loss in the poorer ear and good hearing in the other ear which does not need amplification. The client wears a transmitter in the poorer ear and a receiver in the good ear.

BICROS is very similar to CROS. However, the Bi stands for Bilateral, because the “good” ear has an aidable hearing loss.

The following points apply to the whole testing procedure and will help understanding what is being measured in the different conditions:

The probe microphone is always placed in the better or normal hearing ear, never in the unaidable ear.
The loudspeaker is positioned at 45-90 deg to the measured ear. The same angle is used for each measurement.
The reference microphone is placed on both ears and activated on the same side of the head as the loudspeaker.
The same stimulus is used for all measurements

Cros hearing aids

The objective of this measurement is to make signals from the unaided side of the head sound the same as signals from the side of the better or normal hearing ear.

1. Calibrate and insert both probe microphones.

2. Measurement One:

Measure the REUR/REUG of the best ear with the patient at 45⁰ or 90⁰ to the speaker. Note: The CROS system is not added to the ear at this point. (The Callisto and Affinity software has a CROS/BiCROS specific protocol).

Make sure the position of the speaker is consistent between the two measurements.

3. Measurement Two:

Move the patient so that the loudspeaker and reference microphone are to the side of the unaidable ear (-45⁰ or -90⁰ relative to the poorer ear).

Add the CROS system to your patient’s ear and turn it on. You must also enable the CROS setting in your Affinity/Equinox or Callisto Suite (shown in the image below).

Run the ‘CROS Response’ measurement in the software. The CROS Setting is available in the following location of your Suite.

Both measurements obtained (Better Ear REAR/REIG and the CROS response) should be similar.

You now need to adjust your CROS system until the CROS response from the second measurement overlaps the REUR/REUG from the first measurement. The first measurement is the target curve that you are matching to.

When adjusting the CROS aid in the hearing aid software, you can use our “on top mode” to view both the hearing aid software and REM screen at the same time. Look for this icon.

BiCROS Hearing Aids

The objective of this test is similar to fitting a CROS, however there is a hearing aid on the better ear for which we need to take consideration for.

Firstly, you would fit the hearing aid without the CROS features enabled to a suitable algorithm.

You use the same procedure as for CROS set up except for the first measurement, ensure that the hearing aid is present in the better ear.

Case study : Mrs. M – Single Sided Deafness

A client Mrs. M (aged 57 years) who has long standing Meniere’s disease in her left ear, and normal hearing in her right ear was finding increasing difficulty hearing at work as her hearing dropped with each Meniere’s attack. A recent audiogram revealed a severe hearing loss in the left ear with only 20 % speech intelligibility. Her right ear was in the normal hearing range. She was fitted with an Oticon CROS hearing aid to help in this situation. She found that with all the new features in the Oticon CROS, she was able to hear customers approaching her on her left side and could follow the conversation. She also enjoys the twin link dual streaming feature to watch TV, while still being able to talk to her husband. She enjoys commenting on the TV program together.

Here are some of the highlights of Oticon's new CROS fitting aid. It can be swet up as both a CROS or BiCROS fitting.

Features include:

Open Sound Navigator – delivering a 360° listening experience by balancing the sound in the environment and removing extraneous noise.
New rechargeable versions to ease the burden of battery changes and down time.
Twin link dual streaming –The aid can connect to an external audio stream at the same time as sound transmission from poorer ear to better ear. For example; clients can watch TV while talking to someone sitting on their poorer side.

Keen to learn more about how Oticon hearing aids together with Interacoustics CROS measurements can lead to a successful CROS fitting? Reach out to your local Oticon or Interacoustics clinical team to find out more.

https://www.oticon.com.au/

ABR Interacoustics Eclipse

2024-03-06T13:39:05+00:00

Quality Indicators in ABR measurement and When to Stop Testing

In the realm of audiology, assessing hearing function in infants presents unique challenges. Auditory Brainstem Response (ABR) testing is a vital tool in this process, but we often we find ourselves racing against the clock to get results whilst the baby sleeps. Knowing when to conclude testing and how to determine if your waveforms are of good quality is critical for accurate diagnosis and effective intervention. Applying these tools can help maximise the limited time we have. In this article, we'll address some of the recommended stop criteria recommendations and quality indicators for infant ABR testing, providing insights to help clinicians navigate this critical aspect of infant diagnostic assessment.

Understanding Stop Criteria and Quality Indicators:

Stop criteria and Quality Indicators serve to indicate when it's appropriate to conclude ABR testing and/or move on to the next frequency. These criteria are designed to ensure the reliability and validity of the results obtained. Below we will explore some key stop criteria recommendations:

Residual Noise: Residual noise in the ABR trace should ideally be kept below 15-25 microvolts. Higher residual noise levels can obscure the response (especially at or near threshold) and compromise the accuracy of the results.
FMP is a statistical online analysis of the ABR recording from beginning to end. The Response Confidence is a statistical measure of a true response being present. Work by Guy Lightfoot out of the UK using the Eclipse 4.6.1, has found that on infants and newborns undergoing follow up, an FMP of 2.2 corresponds to a true response detection of 97.5%. Based on this it is recommended to use an Fmp of 2.25, which corresponds to a confidence level of 97.5%.
It works on the principle of comparing response amplitude to residual noise to provide confidence level or detection rate. The underlying analysis considers the ABR recording typically in a time window of 10 ms. The FMP ratio between the response amplitude and the residual noise is calculated. In a response situation, lower noise or larger response amplitude will drive the FMP up (indicated by the red line and bar). In a no-response situation, the response amplitude will not rise above the residual noise, thus the Fmp value and the Response Confidence will remain low.

Image: FMP and residual noise graph.
Wave V Amplitude and morphology: Wave V should exhibit clear and robust morphology with an amplitude greater than 0.04 microvolts. A distinct Wave V morphology signifies a robust neural response, indicating adequate auditory pathway function.
Signal-to-Noise Ratio (SNR) > 3.1: The SNR refers to the ratio of the amplitude of the ABR response to the background noise. A recommended SNR threshold of greater than 3.1 indicates a sufficient signal strength relative to noise, ensuring the reliability of the recorded response. In order to obtain the SNR and amplitude information, wave V peak and trough markers are required (see below).
Amplitude Change and Latency Shift: Does the amplitude of wave V decrease with decreasing stimulus intensity, accompanied by an increase in latency?

In the case of infant audiology, knowing when to stop ABR testing is crucial for obtaining reliable results and ensuring accurate diagnosis. By adhering to established stop criteria recommendations, clinicians can confidently interpret test findings and provide appropriate intervention strategies for infants with hearing impairment.

You might like to refer to our Summary Chat below and save it for future use.

Want to learn more?

You can read more about the Interacoustics Eclipse and testing ABR on our website: www.interacoustics.com.au.

Affinity 2.0 - NOW - Affinity Compact

2023-01-31T09:15:34+00:00

Affinity 2.0 - NOW - Affinity Compact

By now you would know that we have released our latest hearing aid analyser unit, the Affinity Compact. This has taken all the features of the traditionally Affinity 2.0 and put them into a small configuration. It is also more customisable, allowing you to select which features and hardware you require for your specific clinical needs. For the next 6 months we will be highlighting all the features of the Affinity Compact and detailing how this unit can be used to better suit your clinical needs.

This first blog will go into detail about some new features of the Affinity software and the Affinity Compact, covering hardware components and new software features.

4 versions of AC

Lights on AC and what they mean:

The LED light is visible from both the front and the top of the Affinity Compact.

GREEN: Ready in AUD module

RED: Indicates right ear selected in REM and HIT module

BLUE: Indicates left ear selected in REM and HIT module

PURPLE: Indicates both ears selected in REM and HIT module

LIGHT BLUE: Indicates that the Affinity Compact is not correctly connected to the Affinity Compact Suite

A dimmed light indicates that the Affinity Compact has entered power saving mode. This can happen in any of the colours mentioned above.

HIMSA IMC 2 ready fitting

This HIMSA IMC2 regulated integration allows a faster communication between fitting software and diagnostic software to perform fitting. We have already implemented the IMC2 protocol into our software. We are ready to support all hearing aid manufacturers

Probe placement indicator

The Probe Placement Indicator is an easy-to-use feature that provides assistance with placement of the probe when performing real-ear measurements. This feature can be added as a test in the REM module.

Ambient Noise monitor

The ambient noise monitor uses a dedicated microphone that continuously monitors the test environment and displays when noise is exceeding recommended levels.

Free-field adjustment mic

This is ideal for the traveling clinician or if there are changes to the clinic room. Ensure that you have the FF Calibration Adjustment microphone and FF speakers plugged into your Affinity Compact. In AUD mode, click on free field adjustment icon, and it will run automatically.

Hold the microphone where the patients head would be before running the test.

The process is fully automatic and will apply the corrections as needed based on room acoustics.

Note: This process does not overwrite your existing calibration files, it simply adds a correction to them so that the correct stimulus is applied at the reference point in your new environment. On closing the suite this correction is removed.

Listen to Function

Listen directly to the probe microphone or the coupler microphone to hear what the hearing aid is doing. This can help to further understand the patient’s feedback about their hearing aid or it can be used to help the patient’s support person understand how the hearing aid is performing. Listening in to the coupler microphone is a great tool for parents to hear how their child’s hearing aid performs.

This is accessed in REM or HIT module by clicking on the monitor icon.

The monitor will default to 0 % to avoid loud intensity levels.

A great introductory video can be seen as well: 'Listen To' Function on Affinity Compact | Interacoustics.

Delta Values

Delta values calculates the difference between your measurement curve and the target curve. Use the delta symbol to access this information. It gives you a numerical value of the difference between the two curves. A correct match would give a value of 0.

Delta Value icon

This feature can be applied for both REIG and REAR measurements and works for both in-ear measurements and coupler fitting measurements. Delta values are also available when performing Visible Speech Mapping measurements.

High frequency REM/RECD

Hearing aids are amplifying higher frequencies and will continue to do so in the future.

To allow for testing higher frequencies, we have increased our frequency range for REM to 12.5 kHz and to 16 kHz RECD in coupler measurements.

Hearing aid transition

Hearing aid transition is a dedicated test in the REM440 module. This is a valuable test when you have a new patient who attend with their existing hearing aid and sound preferences, but you do not have their historic fitting sessions. The Hearing aid transition test has been created to help you to copy fine tuning preferences.

It is designed to run three different intensities which are customizable to the clinicians preference.

The three intensities are transferred to the built-in Hearing Aid transition fitting prescription and this is automatically selected. The performance of the old hearing aid will now display as a target in standard REM screens and the new hearing aid can be fitted matching the old hearing aids performance.

To learn more about the HAT procedure please visit our Academy website for a tutorial: Performing the Hearing Aid Transition Test | Interacoustics

Aidaptors

These adaptors replace the old acoustic putty (“Blutak”) that audiology clinicians have traditionally used for coupler measurements.

The Aidapter™ from Interacoustics is a unique silicone piece that clicks onto the HA-1 adapter.

It provides a good acoustic seal and standardizes the coupling, ensuring repeatable coupler measurements. The Aidapter™ also eliminates the hygienic issues of using Blutak.

The Aidapter™ is compatible with all hearing aid fitting devices from Interacoustics including the Callisto TBS10, TBS25, Affinity 2 and Affinity Compact.

For more information on Affinity Compact, please also refer to our website with these links :

Website: Affinity Compact | Modular fitting solution | Interacoustics

Video: Affinity Compact YouTube

Instructions for Us: Operation Instruction (interacoustics.com)

Academy training: Real ear measurement (REM) training | Interacoustics

Next month we will cover Visible Speech Mapping (VSMP) and how you can fully utilise this great REM program into your clinic. Helping you obtain faster results with counselling advantages.

To chat to our team about your Affinity Compact needs and how we can help you better refine your assessments,

please call (02) 8899 1200 or email us at info@interacoustics.com.au.

ASSR

2022-11-05T10:47:35+00:00

ASSR on the Interacoustics Eclipse

There is a common misconception that ASSR is only suitable for detecting severe to profound hearing losses and that ASSR isn’t sensitive enough or able to detect normal hearing. A lot has changed in the world of ASSR since it was first released in the 90’s.

Previous ASSR technology was shown to have poor correlation with behavioural thresholds and was also found to not be as sensitive as ABR. This has all changed with the introduction of the second generation ASSR in the Interacoustics Eclipse.

Interacoustics second generation ASSR now ensures accurate and sensitive results can be obtained all within very efficient timeframes.

These improvements in sensitivity and accuracy are achieved via the implementation of the following technologies. This is achieved via the use of:

1. CE Chirp stimuli. CE Chirp stimuli ensures synchronous activation of the basilar membrane which leads to better SNR and faster testing time. Take a look at our quick video demonstration of CE Chirp.

2. Utilisation of multiple harmonics instead of relying solely on the fundamental frequency

3. Phase coherence – a true response will have a similar phase delay to the stimulus.

Want to know more?

A paper by Sininger et al (2018) compared the thresholds and time taken to perform ASSR and ABR in 4 frequencies in each ear for a group of infants and toddlers. The results they obtained demonstrated lower thresholds were obtained with ASSR; specifically, 14.39dB lower at 500Hz, 10.12 at 1000Hz, 3.73 at 2000Hz and 3.67 at 4000Hz. Further to this there was a significant reduction in test time.

To get a great rundown of the research and application of ASSR, tune in to Dr Yvonne Sininger’s webinar “ASSR findings in Infants” to get in to the nitty gritty of how it all works: Click here

Want to test it out yourself?

Give us a call (02) 8899 1200 or email info@interacoustics.com.au and have a chat with one of our audiologists about how to arrange a demo.

ASSR and ABR Comparison on the Eclipse

2023-11-30T14:56:01+00:00

ABR & ASSR Comparison on the Interacoustics Eclipse

The introduction of the new Eclipse ASSR technology has encouraged more and more clinics to make ASSR an integral part of their newborn hearing test protocol. How can we utilise ASSR results and what should we keep in mind when comparing them to ABR thresholds? This blog post will attempt to answer these questions and provide important points for consideration.

For clinicians who have not used the Eclipse ASSR platform, here is a link to a quick video explaining the testing process: What is ASSR Hearing Testing.

The ASSR module on the Eclipse enables testing all 4 main frequencies in both ears at the same time. It uses a CE-Chirp stimulus and a powerful detection algorithm which improves threshold detection. ASSR is an objective test showing the statistical certainty of a result rather than looking for a wave V on an ABR waveform. In view of this, research has found that the new generation of ASSR is on average yielding better thresholds than threshold ABR testing. The Sininger et al 2018 paper shows the main differences were at the lower frequencies.

The corrected ABR–ASSR discrepancy. The table below describes the average dB that ASSR results were below the ABR threshold at the same frequency.

If there is a considerable difference in results between the two tests you may need to consider the following points:

Compare the same stimulus type

ASSR uses the CE-Chirp stimulus, so it is easier to compare with ABR also using CE-Chirp stimulus. CE-Chirp gives a larger wave V as it considers the travel time of the stimulus in the cochlear. If the clinic is using a different stimulus type for ABR eg. toneburst, click etc. it is difficult to compare to ASSR CE-Chirp, as the ASSR may have lower thresholds.

Use the latest Eclipse software for ABR and ASSR available

At the time of writing the latest ABR/EP software 4.6.1 has the new FMP calculation. This calculation is not affected by the HP and LP filter setting.

ASSR software 1.3.0 now has correction factors for BC and the artefact rejection level defaults to 20 uV (which is a more appropriate level).

Recommended protocol for ASSR

Before commencing an ASSR, you can select the test method priority and the correction factors to use. Test method priority options are speed or accuracy. We would recommend using “Accuracy” for testing babies. This gives a 99 % confidence in the result, as opposed to 95% for Speed.

You should also select the correction factors for ASSR for inserts, headphones, and BC. This is available for different ages up to 2 years of age. These transducer details need to be added into the protocol set up for each test, so that the system converts nHL to eHL automatically. The result is an audiogram which has both nHL and eHL marked.

Use residual noise as a stop criteria

If you are only collecting 2000 sweeps and not considering the residual noise, you may find the traces obtained have too much noise, which can obscure your waveform. Worldwide it is recommended to use a stop criteria of 15-25nV for infants depending on the test room environment. If higher residual noise is present, more sweeps will be needed to achieve a result. If you are only collecting 2000 sweeps and not considering the residual noise, you may find the traces obtained have too much noise.

Repeat waveforms if needed

It is recommended to repeat waveforms at the “response absent” level to help confirm the result. If unsure of a waveform during testing, repeat to confirm.

Use the ABR wave V trough marker to check amplitude and SNR of the waveform.

Place the wave V trough marker at the lowest point that follows wave V (generally around 10ms). An amplitude of 0.04 or greater – then you probably have an ABR. If less than this, may not be big enough to count. The trough also gives us a SNR. (amplitude divided by residual noise). A value of 3.1 as a minimum is acceptable. This means ABR is 3 times larger than the noise. Any less is not acceptable.

Ensure that correction factors are used to obtain eHL

For ASSR on the Eclipse, if the age and transducer used are selected in the protocol before testing, the ASSR module will automatically calculate the eHL and plot on an audiogram.

For ABR on the Eclipse, the combined correction tables from the BSA Guidelines (2021) are recommended for converting ABR thresholds to eHL. The Chirp data in these tables refers to the CE-Chirp which is used in the Eclipse.

To compare ABR and ASSR thresholds, you need to compare in eHL.

Conclusion

Incorporating ASSR testing into your ABR tests yields numerous advantages. As we compare this technique to more conventional methods, we must make sure we're mindful of the changes that might be required to ensure accurate comparisons. These include; using the same stimulus, carefully inspecting our noise parameters, and deploying up-to-date software. Doing so guarantees quicker, more reliable, and more accurate results for both types of tests.

If you need help with your ASSR and ABR testing, please reach out to our experienced audiological team to assist you via email at info@interacoustics.com.au or phone on 02 8899 1200.

References

British Society of Audiology (2021), Guidelines for the Early Audiological Assessment and Management of Babies Referred from the Newborn Hearing Screening Programme: Practice Guidance Document

Sininger, Yvonne S; Hunter, Lisa L; Hayes, Deborah; Roush Patricia A; Uhler Kristin M (2018): Evaluation of speed and accuracy of next generation of ASSR and ABR audiometry in children with normal hearing and hearing loss: Ear & Hearing 2018 Nov-Dec; 39(6) 1207-1223. Abstract available here: Sinniger et al Abstract

Audiometry made plug and play

2021-03-15T10:20:25+00:00

At Interacoustics, we know that hearing screening is an essential service in ensuring early diagnoses and improved management of hearing loss, so we’ve developed a simple solution to help you see more patients with ease. Now available, Luna is a fast and reliable air conduction audiometer built right into a headset.