Loose or tight hearing aid fittings? How I got it all wrong

One of the great joys of having led a long and busy professional life is the pleasure that comes from growth. We all have much to learn and there is nothing like vast amounts of experience to help us refine the skills we use at work each day.

Today’s post, on whether or not to make custom hearing aids (or earmolds) tightly fitting, addresses a topic on which I have completely reversed my opinion. Thirty years ago, I had it all figured out–exactly wrong! So, pour yourself a cup of coffee, or glass of whatever you prefer, and let me tell you the story.

In November 1989 I wrote an article in my Nuts and Bolts column in The Hearing Journal entitled “Avoiding Sore Ears.” I had spent a lot of time working with Jack Scribner, the owner of Earway Laboratory, an earmold lab here in San Diego. Jack was one of those opinionated people who had an unlimited ability to fix things and make them work. Unfortunately, his ability to explain why they worked was not so great. I learned most of my earmold skills and impression-taking techniques from Jack.

 

WHAT I THOUGHT THEN

In my 1989 column I wrote, “Do not make tight impressions! Do not ask the lab or factory for tightly fitting earmolds or hearing aids. A perfect fit is loose; like a piston in a cylinder block, the piston is always smaller than the space it occupies.”

I went on, “Tight-fitting plastics almost always cause sores. So always work with runny impression material. This material is very heat-sensitive; therefore, in the hot summer months you must refrigerate it. Never try to cheat the material by using excessive liquid.

“After you make the impression, have the client do exaggerated chewing movements. This reshapes the material, relieving pressure points. …When you get the hearing aids or earmold back from the factory… cut down the tight spots on the impression. Use as little plastic as possible in the canal and in the helix.”

Now, 25 years later, I understand that almost everything in that passage is wrong!

 

WHAT I KNOW NOW

After that column was published, I received a telephone call from the owner of an earmold lab. I’m sorry to say, I don’t remember his name or the name of his lab, but I do remember what he told me:

“Dr. Martin,” he said, “I disagree with everything you wrote in your article.” He went on to tell me about his experience and what he believed. I acknowledged his comments, but I basically ignored his ideas.

Years later, two different people forced me to take another look at this issue. One of them was a patient of mine–an intelligent and well-respected retired plastic surgeon. The custom-fitted hearing aid in his right ear had feedback, but I didn’t want to make it tight for fear of hurting the tissue in the canal.

 

ADVICE FROM A SURGEON AND AN ENGINEER

This man had a lot of experience fitting prosthetics to the human body, and he shared with me his insights into how much pressure is required to cause necrosis. He cited dozens of different items that are safely attached tightly to the human body. He convinced me that tight is not necessarily bad.

I made him several different “experimental” tight hearing aid fittings. One of them worked very well and was comfortable to wear.

I also became familiar with Chester Pirzanski, an engineer now with Unitron in Canada, who previously worked for Starkey and Oticon. He has written and spoken extensively on how to make earmolds, and recommends deep canal impressions and snugly fitting hearing aids. I have tried many of his ideas, and had success with them.

 

THE REAL PROBLEM

Over the years I have come to understand that the risky part of fitting a hearing aid in a patient’s ear is not that it causes general tightness, but rather that the aid has an “edge” or a rough spot that cuts into the tissue of the ear canal. Most of the sores we see in the ears of hearing aid wearers are the result of edges, points, and/or bumps on the shell of the hearing aid.

I now devote extra effort to eliminating any sharp edge that can cut into the patient’s skin. Now, please don’t misunderstand me, tightness is still an issue. New patients, especially, may be uncomfortable wearing tightly fitted instruments, and so they may reject the entire fitting for reasons of comfort.

But general tightness no longer holds the “peril” for me that it used to. I often make snugly fitting impressions and earmolds, especially in the aperture where most of the leakage that causes feedback occurs. This is one of many areas where long experience is a true blessing.

2 Comments

  1. Dr Bob, I went on hiatus from the hearing aid profession for over 15 years in 1995, literally in “Rip Van Winkle” mode; and when I woke up, had things really changed, and for the better: Suddenly I had effective anti-feedback processing at my disposal, and I’ve yet to have a problem, especially providing venting for profoundly deaf patients who I would never even dare to try before.

    That Being Said, if you go back and look at Chester Pirzanski’s articles, you’ll also see that he recommends using a bite block *and telling the lab*, as that will solve the TMJ problems for about 20% of the patients.I mark “Jaw open impression w/Bite Block” on the order form & inside lid flap of the box, and for good measure I toss the bite block into the box as well.

    In extreme TMJ cases if you use an earmold lab that scans & 3D prints the earmolds or shells, you can take two impressions of the ear, with bite block & jaw closed, and mark them accordingly. This way the technician will superimpose the two “wireframe” images in the modelling software, and make the proper adjustments.

  2. I find that the only way I get molds that are comfortable is by making all the mouth motions you mention, especially smiling broadly. No audiologist told me that, but I realized my aids hurt when I smiled. After that I always smiled and moved my mouth into contortions when a mold was made and that took care of the problem.

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