March 3, 2009 Feature

Beyond BTEs

Earmold Opportunities in Clinical Practice

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In the last few years the use of behind-the-ear (BTE) form-factor "open" hearing instruments has continued to grow. This trend shifts some of the focus away from custom acoustic coupling for hearing aids, and also creates opportunities for parallel markets based on custom earmolds, also known as "otoplastics." With a severe recession underway, one way for audiologists to survive these difficult times is to diversify their income streams and rely less on low-volume, high-priced hearing aids and shift focus to higher-volume, lower-priced alternatives.

There are several ways to expand opportunities to provide custom earmolds for non-hearing aid applications and an anatomically based approach for making ear impressions.

As baby boomers enter the hearing health care delivery system, they bring a challenge for clinicians. These patients are not the typical hearing aid user of 10 years ago, many of whom were in their 70s. Baby boomer patients are seeking hearing health care at younger ages. They have grown up with technology and use a variety of audio devices that couple to the ear, and many insist on better fidelity in all of their electroacoustic devices. Providing acoustically tuned, anatomically accurate solutions is an excellent way to help these clients continue to enjoy their MP3 players and other audio devices.

Audiologists often raise the following two questions:

We don't need earmolds anymore, do we?

For the majority of open hearing aids, this statement is accurate; the same patients who opt for micro behind-the-ear (BTE) receiver-in-the-ear (RITE) instruments, however, may still need custom retention earmolds. All major earmold labs now have the ability to create these for just about any hearing aid. If your lab doesn't send them, make a dummy aid or make an impression of the receiver and send it along with the ear impression.

How about earmolds for hands-free headsets?

A growing number of states and municipalities are passing laws requiring the use of hands-free headsets for cell phone calls made while driving. The majority of these headsets can accommodate a custom earmold, not only improving comfort but also improving the clarity of the signal reaching the wearer. If the user is willing, an audiologist can send the headset into the lab with the ear impression. If not, an impression can be taken of the headset's earpiece and it can be included with the ear impression. A digital photo of the headset in the patient's ear is also helpful, particularly with headsets that have extended-boom microphones. This additional information on use position assists the earmold lab in orienting the mold correctly.

The Sound of Music

It's almost impossible to walk down the street today and not see people using MP3 players. Although this compression format allows for very high-fidelity reproduction of music, standard earbuds cause several acoustic problems. If the earbuds fit, which is rare, they occlude the ear canal and obliterate most of the real-ear unaided response (REUR). More likely, the earbuds fit poorly and allow ambient noise into the ear, requiring the user to turn up the volume to potentially dangerous levels. Poorly fit earbuds also leak low frequencies and distort the frequency response or equalization of the music, lowering the fidelity of the sound.

Several companies now offer a range of "prosumer" earphones designed to fit better and compensate for or replicate ear canal resonance. Although most of these earphones have fairly good ear couplings, these higher-end transducers will always fit and sound better with custom earmolds. Marketing these molds attracts audiophiles to your practice. These critical listeners place a high value on sound quality and are more likely to be open to using custom hearing protection and ultimately be consumers of higher-technology hearing instruments. Attracting these clients to your practice for their MP3 players can be the beginning of a long-term relationship.

In addition to making music easily accessible, computers and the Internet have made it relatively simple for amateur musicians to produce, edit, and publish their own music, and to replicate the classics of their youth. The garage band of the 1980s has evolved, with lawyers, CPAs, and stockbrokers now jamming on the weekends. These amateur musicians may have more disposable income than amateurs in the past—but they are also likely to have fewer outer hair cells, so the old wedge monitors no longer work well. These individuals are strong candidates for custom in-the-ear monitors that are available from several major earmold labs.

Law Enforcement Applications

Another often-overlooked opportunity is the creation of earmolds for law enforcement and security personnel. Several years ago I learned about a retired security professional in California who became licensed as a hearing instrument specialist in order to make ear impressions legally. Using his professional contacts, he built a successful business by exhibiting at police and security conventions. He would take impressions the first day of the show, then send all the impressions overnight to a lab for quick service and deliver them before the customers left the convention. Although this arrangement may not be possible in all markets, making contact with the local, county, and state law enforcement organizations can be a very good supplemental income stream. These same people are good candidates for custom passive and active hearing protection as well as hearing instruments designed for high-frequency hearing loss. These patients are also excellent candidates for tinnitus retraining therapy.

Making Effective Earmolds

The rapid evolution of hearing instruments away from occluding earmolds has taken good ear impression technique somewhat off the radar of many audiologists. Hearing instrument and earmold manufacturers have new and better tools for fabricating earmolds, including the use of three-dimensional computer modeling and laser-guided fabrication. With these tools, new possibilities exist to better control feedback and modify the frequency response of the amplified signal. The potential weakness of these new systems is that they still rely on a conventional ear impression. These tools and techniques allow for more precise duplication of the impression and make the quality and accuracy of that impression more critical than ever.

In addition, the migration of laser scanning and fabrication from hearing aids to earmolds means that audiologists need to learn the capabilities of these new technologies so that we can take advantage of them. This reality and the higher expectations of the baby boomer market make it prudent for audiologists take a hard look at their techniques and make any needed changes.

Effective Customizing

In order to make effective earmolds and other custom otoplastics, keep the anatomy of the ear and the physics of sound as the primary navigators. The impression-taking process begins with observation. Look at and feel the pinna. Check the mastoid process for defects. Palpate the massiter muscle during jaw movement. These observations are key to understanding how the ear and ear canal will interact with the earmold.

The shape, firmness, and size of the pinna will guide in the selection of style and material. Extremely firm pinnae require extra attention to accuracy in impressions. For these patients, avoid stretching the pinna—this distortion will create an impression and mold that are too tight, leading to discomfort and the need for modification or remake. Very soft pinnae, such as those on infants, are very susceptible to over-stretching and distortion if the wrong impression material is used. Generally, the softer the pinna, the lower the viscosity and shore value of the impression material.

Following this evaluation, perform a thorough otoscopic examination. The use of a video otoscope allows for the documentation of any landmarks or abnormalities and also engages the patient. During the otoscopic examination, I memorize the path of the ear canal so that when I place the otoblock, I can replay that path in my mind. This knowledge allows the otoblock to be placed in a single smooth movement rather than in a series of short, sharp jabs. This whole external ear evaluation takes three to four minutes.

To avoid excessive insertion loss, plan for the real ear occluded response (REOR) ahead of time. By making a few probe microphone measurements before the impression, I know the location of the resonant peak for the patient's individual ear canals. With this data, I can plan any needed bore modifications such as a Libby Horn or a CFA Bore #3 to overcome the insertion loss. It is, of course, possible to compensate for this loss with hearing aid programming, but if the earmold can be acoustically transparent, sound quality can be maximized.

It has been determined that 50% of hearing aid re-makes are due to poor impressions (Pirzanski, 2000). After spending time in an earmold lab, I feel that at least that many earmolds are re-made for the same reason.

Taking a pair of accurate ear impressions requires approximately one-sixth of an hour—but 100% of your attention. If the impression comes out of the ear and is even a little off, you should do it again. Consider how your patient might interpret a statement like the following:

"This impression is quite good, but not quite up to my standards. I know it's not the most comfortable procedure, but I really need to do one more, so we have the best impression possible in order to make the best possible earmold (hearing aid)."

Some may consider that such a blatant admission of imperfection will erode patient confidence. It has been my experience that just the opposite is true. Ensuring the impressions are as perfect as possible is critical to the success of the final hearing aid or earmold and should therefore be a requirement for concluding the patient contact.

One of the most helpful habits I've developed over the years is to periodically take an additional impression of a patient or of a staff member and send it to my preferred lab for a critique. It is very helpful to get an objective opinion of one's technique.

Throughout my career, I have been fortunate to work closely with some excellent otologists. This has provided me with the opportunity, as part of my daily practice, to make impressions of an unusually large number of post-surgical ears.

Audiologists in more traditional practice settings should seek out these unusual ears to practice their technique. A relatively inexpensive way to do this is to remark to the owners of these ears how interesting they are and that in exchange for allowing you to practice on them, you'll make them a free cell phone headset or hearing protection earmold.

Brad Ingrao, AuD, CCC-A,, is director of audiology for the Canadian Sensory Institute and conducts workshops (online and in person) on earmold technologies and other audiology topics. His clinical interests include earmold technology, computer automation and integration, and accessibility for individuals with hearing loss. He is developing a telepractice system to deliver services to remote areas of British Columbia and beyond. Contact him at bingrao@sensory.ca.

cite as: Ingrao, B. (2009, March 03). Beyond BTEs : Earmold Opportunities in Clinical Practice. The ASHA Leader.

References

Ingrao, B. (2005, Nov. 8). Stick it in your ear: A systematic approach to earmold selection.The ASHA Leader, p. 6–7, 30–31.

Pirzanski, C. (2000). Selecting material for impression-taking: The case for standard viscosity slicones.The Hearing Journal, 53(10), 45, 48–50.



  

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