Martin, Robert L. PhD
I was fitting a patient with a pair of simple ultrahigh-powered behind-the-ear aids. BTEs are great if the patient needs high gain and high output. This patient's most recent audiogram was a 70-dB flat curve. My internal warning bell went off — something was terribly wrong.
Figure. iStockphoto....Image Tools
Her aids do not have automatic gain control or a multimicrophone system. My assistant said the aids were just replacements, and that the patient liked the hearing aids she was wearing.
Figure. Robert L. Ma...Image Tools
The patient's chart had two previous audiograms. Her hearing had dropped 20 dB from 2008 to 2012. She returned to the office earlier this year asking for more sound. Apparently we had given her enough sound to curl her hair, toast her bagel, and heat her coffee in the morning. She told me she loved the fact that she could hear so well, but she noted that the world was noisy. Loud sounds bothered her, she said, and cars and trucks were irritating.
Adjusting her replacement hearing aids was impossible. The fitting was wrong. No question, this patient needed features that these hearing aids did not have: automatic gain control and a multimicrophone system to reduce unwanted noise. I returned the hearing aids to the manufacturer, and ordered the appropriate set.
This patient needed more sound. We have to be careful when this occurs that we do not, as the saying goes, jump from the frying pan into the fire. I loaned her a simple high-powered hearing aid, and she loved it. I was not wise enough to realize these hearing aids, while making her happy initially, would create major problems later on. Six critical questions should be answered before deciding which hearing aid is best for a patient.
* Is automatic gain control needed?
* Should the fit be open or occluded?
* Will the patient perceive a major reduction in background noise if the traditional noise reduction strategy is implemented?
* Are there environmental constraints in the area such as a living on a noisy street, a barking dog, or a crying baby?
* Are there acoustical challenges such as a loud or soft-spoken family member who lives with the patient?
* Does the patient have an occupation that requires excellent hearing on a cell phone (e.g., a real estate agent)?
AUTOMATIC GAIN CONTROL
This problem could have been avoided if I had answered the critical question, “Does this patient need automatic gain control?” Some experts contend that all hearing aids should have it, but I strongly disagree. Most patients need automatic gain control (compression), but at least 10 to 20 percent of patients need huge, unrestricted power that can be delivered without distortion and feedback — megapower. These megapower BTEs are great if the patient has a large mixed hearing loss with high, uncomfortable listening levels. Patients are euphoric when they can finally hear well.
The question of automatic gain control forces us to study the patient's uncomfortable listening levels and think about output rather than gain. The output values for these instruments are more than 130 dB. These instruments are not appropriate if you were worried about high output levels.
It is not an easy task to select the best hearing aid for each patient. The most expensive, flexible hearing aid on the market fits only a small percentage of patients. Patients often have financial constraints, dexterity and memory are often poor, and some have cosmetic issues. The patient may not want a complicated system, and may be at the stage in life where simplicity is most important.
OPEN VS. OCCLUDED
Another patient had hearing loss in both ears. His thresholds are 10 dB at 0.25 kHz; 30 dB at 0.5 kHz; 55 dB at 1.0 kHz; 80 dB at 2.0 kHz; 100 dB at 4.0 kHz; and no response at 8.0 kHz. Speech reception thresholds are 50 dB and the WUSs are 80 percent at 75 dB bilaterally. Simplistically, these thresholds can be written as 10-30-55-80-100-100+.
You may wonder if this patient can be fitted with a pair of open-fitted hearing aids, or you might start with an open fitting and switch to an occluded fitting if he is unhappy. This may or may not be wise. The patient may reject the hearing aids if he does not hear well in the first few days. He may also reject them if you occlude his ears too much. So what to do? There is no easy answer. You earn your living by making tough decisions, studying data, talking to the patient and his family, and determining the effect of hearing loss on the patient's life.
Hearing loss severity in the high frequencies suggests a dead zone beyond the help of amplification. The speech tests indicate the need for considerable amplification. The ease and comfort of an open fitting is highly desirable, but is it the best choice? This patient may have no usable hearing in the octave band centered at 4.0 kHz and little or no usable hearing at 2.0 kHz. The dropoff in the higher frequencies is 10-30-55-80-100-100+.
I keep a pair of open-fitted hearing aids in my office for patients to try during live voice testing with and without instruments. It's worth doing this because he will probably want to return them if he does not see a substantial improvement in his hearing.
This patient's response to an open fitting is critically important. The fitting's success is in danger if he reports no difference when the aids are on or off. This is not the fitting's logical stage; it is the emotional one. The patient needs to experience a surge of positive emotion to propel the fitting through the first few weeks.
REDUCTION IN BACKGROUND NOISE
Patients with a flat, moderate sensorineural hearing loss often experience huge reductions in perceived background noise when switching between programs. Working with these types of patients is rewarding, but unfortunately, many patients do not receive significant improvement from a noise-reduction strategy. Their hearing may be too good in lower frequencies so they do not perceive any noise reduction. Poor hearing may indicate that functional hearing only occurs in lower frequencies, and activating a directional microphone system eliminates usable hearing.
We need to be careful what we say to patients about this topic. I do not discuss it if it appears that noise reduction will be highly successful for a patient. Instead I demonstrate it by tuning the aids, fitting them, placing a 75-dB composite noise directly behind the patient, and switching back and forth between the everyday setting and noise reduction setting. Many patients will no longer hear the noise if the setting has been adjusted properly and the earmolds are doing their job.
ENVIRONMENTAL AND ACOUSTICAL CHALLENGES
A patient's primary challenge may come from his family or environment — a barking dog nearby or a soft-spoken or loud family member. You need to spend considerable energy ensuring the automatic gain control settings are ideal. I am old school; I spend more time looking at gain than output. Situations like these, however, require running series of output curves. Remember, noises that can be tolerated for a few minutes during an uncomfortable listening level test in the office do not have the same level of irritation as noises that go on all day. When in doubt, use a little extra compression or expand the number of settings the patient is using to include a barking dog setting.
Carefully adjust the gain in the low frequencies if the patient lives on a noisy street or near a highway. An everyday setting in some cases cannot be used at home because of surrounding noise. It helps to have the patient use the noise setting at home if street noise is excessive. This markedly reduces the distance the patient can hear with the hearing aids, but it also reduces perceived noise. It helps to remember we are fitting the patient's life, not his ears or hearing loss.
BLUETOOTH AND CELL PHONES
Many hearing aid models, ear molds, programming codes, and remote controls are predetermined for patients who depend on hearing well on a cell phone, especially for their occupation. Bluetooth connectivity and some types of ear molds become a requirement, not an option. A cell phone system that provides real ear gain in the high frequencies (a completely open system) cannot compete in hearing quality with a system that provides clear, broadband, undistorted, real ear sound. The open system does not plug out environmental noise for a cell phone user, but the occluded system does.
You spend most of your professional life helping people, and the six critical questions help you do that and make your life easier. When I make mistakes, as I did with the first patient, I realize that I was distracted at the time. I knew she wanted more sound, but I was not paying attention to other important issues. The fitting is easier, the patient is eventually satisfied, life is better, and the fitting does not fall apart after a few months when you choose wisely. If I select the wrong product or the patient talks me into trying something that I know will not work, I make life more difficult for my patient and myself. Starting on the right track avoids major headaches down the road.
* Read Dr. Martin's past columns in a special collection in The Hearing Journal archive at http://bit.ly/HJMartin.
* Visit HJ's Student Blog at http://bit.ly/HJStudentBlog.
* Check out HJ's R&D Blog at http://bit.ly/RDBlog.
* Click and Connect! Access the links in The Hearing Journal by reading this issue on our website or in our new iPad app, both available at thehearingjournal.com.
* Comments about this article? Write to HJ at HJ@wolterskluwer.com.
* Follow us on Twitter at twitter.com/hearingjournal and like us on Facebook at www.facebook.com/HearingJournal.
© 2012 Lippincott Williams & Wilkins, Inc.