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Dr. Ross on Hearing Loss

A Clinical Research Summit

by Mark Ross, Ph.D.
This article first appeared in
Hearing Loss Magazine (Nov/Dec 2007)

For practitioners in any field, “state-of-the-art” conferences serve as a kind of platform from which the current status of a profession can be examined in order to more effectively chart a path for the future. We must, in other words, know where we are so that we can better plan where we want to go. In the Hearing Care Industry, the most recent such conference was convened by the Starkey Hearing Research Center early in 2007. However, the approach used seemed a bit more creative than that employed in the usual such conference. Rather than simply being assigned a topic, a select group of participants was asked to jointly identify the top challenges and issues that would be facing the field in the next five years.

The six topics that emerged during the two-day summit represented those with which the participants - all leading figures in the field - had personally wrestled. Although the report of the conference, which appeared in the June 2007 edition of Hearing Review, is divided into six chapters authored by different individuals, the sentiments expressed in each one represent a consensus of the entire group. Their relative importance is not reflected in the order in which they are discussed below. But it is important to note that all of them relate, directly or indirectly, to the ultimate goal of enhancing the communication capacities of people with hearing loss.

Using Clinical Measures to Predict Real-World Performance

The first challenge deals with the frequently-observed disparity between the technical performance of a hearing aid in a clinic, and the “real-world” performance of that same hearing aid. Right now, a person’s test scores in a clinic are an imperfect predictor of how the person will function with the aid in his or her usual environment. This is not a trivial consideration. Consider someone who is tested with and purchases a “premium” hearing aid at a premium price. These aids include a number of advanced features not found in a “basic” digital hearing aid. The test scores and technological possibilities of the aid’s special features can’t help but raise a user’s expectations regarding its performance outside of the clinic. Sometimes these heightened expectations are fulfilled, but sometimes not. The goal is to develop clinical measures that can predict, with a reasonable degree of certainty, performance of the hearing aid in a users’ normal environment. People shouldn’t be investing a lot of money in “top-of -the-line” technology without some reasonable assurance that the added cost will be reflected in noticeable listening benefit.

It’s evident why there is often a disparity between the way a hearing aid functions in a clinic and in one’s usual environment: Listening conditions generated in a clinical test situation differ significantly from those that occur elsewhere. In the “real world,” a person is exposed to a host of various and often unique conversational partners and acoustical environments. Interactions may occur between certain hearing aid features and various environmental listening conditions. Therefore, superior performance of a specific hearing aid or feature observed in the clinic may not apply elsewhere.

The challenge we face is in finding ways to rectify this discrepancy, as it always seems easier to define a problem than to develop a research strategy to address it. Conference participants made numerous recommendations for developing such a strategy, foremost among these being the replication of natural listening conditions in a clinic, perhaps by better defining the actual type of noise environment that a particular person encounters. One way this can be accomplished is by incorporating data logging capabilities into a hearing aid, which is already done on a limited basis with some aids. This would permit clinicians to better understand the listening problems faced by a specific person. Additionally, advances in virtual-reality technology may permit people to interact with computer-simulated environments that are similar to what would be occurring outside of a clinic. In the meantime, however, I would strongly suggest that new hearing aid users be sure to do their own careful analyses and comparisons during the trial period.

Understand Individual Audiometric Differences

The second challenge reviewed at the conference concerned the fact that people with similar audiograms will not necessarily understand speech similarly. While numerous conditions can produce comparable audiograms, the underlying pathology may be dissimilar and affect different parts of the auditory system. Consequently, the resulting behavioral consequences would tend to vary. Research studies have demonstrated that differences in speech comprehension may still persist even when people with similar audiograms are aided identically with hearing aids.

A cochlea can be damaged or stressed by any number of factors, including noise trauma, ototoxic drugs that may affect inner as well as outer hair cells, and various genetic abnormalities among many others. Each of these different conditions can produce varying behavioral consequences. The variability in speech comprehension is usually greater when hearing-impaired people are tested under noisy conditions than in quiet. Even the type of noise may increase the differences in speech comprehension observed among people with similar audiograms. For example, interrupted noise will often have a greater effect upon some people than steady or constant noise. The point is that audibility alone i.e., the portion of the speech signal that can be perceived is not a perfect indicator of how well someone can understand speech. Other factors come into play, such as differences in temporal (time) and spectral (frequency) resolution abilities and whether or not there are any regions of dead hair cells in the cochlea. One of the recommendations made at the conference was for the development of additional clinical tests, presumably simpler ones than those now available, which can be used to identify these factors.

The summary questions asked by the conferees focused on whether hearing aid fittings could be significantly improved if more was known about each person’s unique auditory abilities. Would alternative fitting strategies or algorithms be appropriate? Perhaps more detailed psychoacoustic information would demonstrate the necessity for developing some new hearing aid features. I think consumers will agree that these are key questions and appropriate topics for future research. But even if additional information about a person’s auditory skills cannot presently result in improved hearing aid fittings, such knowledge can be extremely valuable in helping someone develop realistic expectations. Sometimes it helps to know what is not possible as well as what is.

Evidence-Based Practice

In the last 10-15 years, there has been a technological explosion in hearing aids, with new technological features and speech processing strategies almost deluging the market. Each such development is accompanied by blurbs extolling its virtues, and implicitly or explicitly, implying that this new development has merits not found in previous generations of hearing aids. It is difficult for even the most sophisticated consumer to resist the logic and appeal of many of these technological developments. They all “sound” so good in the telling. Hearing aid dispensers are not immune (if anything, they are even more susceptible) to the allure generated by the possibilities inherent in newly introduced technology. When they recommend some new hearing aid for consumers, they do believe that it will provide additional listening benefits over previous models. A number of factors influence their choice of a specific hearing aid; these would include the technical information provided by the manufacturer; the results of traditional, but fairly insensitive, tests batteries; their own personal experiences with the hearing aid; and what they learned years ago in graduate school. While all of these factors have merit, they are not identical to the concerns raised in the next identified challenge: i.e., making decisions based on the best available evidence.

What evidence-based practice seeks to do is encourage practitioners to use the best available evidence in making decisions regarding the recommendation of specific hearing aids to specific people. Now, this sounds like common sense; as the profession prides itself on being scientifically based, one would expect no less from hearing aid dispensers. But the situation does get a bit murky when it is examined more closely. For instance, there are various levels of evidence that have to be considered. A single study, no matter how well it is done, would not have the weight of the general conclusion of a number of similar studies. But, on the other hand, if it were well controlled and randomized, it would be more convincing than a series of case studies. At the bottom of this hierarchy is “expert opinion,” the practice evidently employed by most hearing aid dispensers. While useful, and indeed often necessary, it is still not quite as convincing as an objective study. The “challenge” articulated by the participants was how to best incorporate this concept in everyday clinical practice. Hearing aid users deserve the assurance that the hearing aid recommendations and fittings that they receive are based on the best available research evidence. This article has mapped out a path to that goal.

Hearing Aids and Wireless Technology

We know that hearing-impaired individuals experience great difficulty understanding speech in situations that are noisy or in which they are located some distance from a talker or a sound source (e.g., a loudspeaker). In these types of situations hearing aids, while necessary, are often insufficient. The challenge reviewed in this section deals with developments in wireless technology that will result in improved speech perception under unfavorable acoustic circumstances beyond that possible with hearing aids alone.

As the authors point out, assistive listening systems (ALDs) have been available for many years. All of these systems FM, Infra-Red, and Induction Loop have one feature in common: They all bridge the space between the sound source (microphone or loudspeaker) and the listener, thus overcoming the potentially detrimental impact of noise, reverberation and distance. While such systems can now be found in many public venues, it is generally agreed that they are insufficiently used by people with impaired hearing. There are numerous reasons for this, foremost among which are logistical problems and the visibility of the receivers. Personal FM assistive listening devices have also been available for many years, but these, too, are rarely used (only one out of every 200 consumers reports the use of these devices). So here we have a situation in which a proven method for improving speech perception - i.e., use of either large or small area ALDs, or both - is insufficiently employed by people who stand to benefit.

The suggested solutions emphasized modifications within hearing aids themselves. The ideal solution visualizes a world in which all PA systems, telephones, etc. would routinely incorporate a wireless transmission capability, interfacing with such hearing aid modifications. Indeed, some current hearing aids now have the capacity to “talk” to each other, using “near field magnetic induction” (NFMI). NFMI works on the principle of magnetic induction, something like a telecoil, but is a short-range two-way radio system, with the capacity to both send and receive transmitted encoded signals. Besides its relatively straightforward capability to simultaneous adjust both aids in a binaural fitting, unique algorithms can be enacted to maximize binaural cues with the intention of improving localization and speech perception in noise (both fundamental binaural functions). One related development includes an external “gateway” device. This is a small body worn receiver that can detect external short-wave radio signals (such as from a Bluetooth equipped cell phone) and retransmit the signal to the hearing aid. Future possibilities would include the reception of audio signals from other sources as well. The article discussed the desirability of incorporating tiny low-power digital chips in hearing aids, smaller and requiring less power than Bluetooth, that would include this capability

One development associated with near field magnetic induction (NFMI) includes an external “gateway” device. This is a small body-worn receiver that can detect external short-wave radio signals (such as from a Bluetooth-equipped cell phone) and retransmit the signal to NFMI equipped hearing aids. Future possibilities would include the reception of audio signals from other sources as well. The article discussed the desirability of incorporating tiny low-power digital chips in hearing aids, smaller and requiring less power than Bluetooth, that would include this capability.

Aural Rehabilitation (A/R)

The actual title of this fifth challenge is “Warning: Do NOT add on A/R or auditory training to your fitting procedures.” In using this catchy title, the authors are trying to get our attention; they are not suggesting that A/R be ignored! They are, instead, making the point that it not be viewed as an “add-on” activity that may or may not take place at the conclusion of the dispensing process. What the authors are suggesting is that A/R be regarded as an integral component of the entire hearing aid selection and management process. I must admit that I chuckled when I read this comment. In my first exposure to A/R, as a patient at the Walter Reed Army hospital in January l952, this is exactly the approach I was exposed to. It sounds to me that basically what they’re suggesting is that we go “back to the future.” In those far-off days, when Audiology was first emerging as an independent profession, the selection and fitting of the hearing aid (vacuum tube body- worn) was not viewed as a separate mission, as is now done. Rather, it was integrated into the total A/R program (consisting mainly of speechreading and auditory-training). Therefore, I completely agree with the recommendations made by the summit participants. They would like to see A/R viewed not as some sort of dessert, to be partaken after the main course (hearing aids) is completed, but rather simply as a component of the main course itself (maybe more like a “grazing” menu?).

As satisfying as the A/R banquet I received from Walter Reed Hospital 56 years ago was (to continue the metaphor), we are now able to improve the offerings even more with our present state of knowledge. The participants identified the A/R components that must be addressed when the activity is viewed holistically. The foremost need is sensory management to optimize sensory capabilities. This would include hearing aids, assistive listening devices, and all other types of hearing-assistive technologies. This is self-evident. Unfortunately, however, this is also too often the point where A/R activities cease. A holistic program would be significantly more inclusive, and might offer such services as hints on how to be a more effective communicator, perceptual training (speechreading and auditory training), and counseling, as needed. This latter activity can consist of information (i.e., explanation of the audiogram, care and use of hearing aids and other devices, etc.) or emotional support (probably best provided in a group setting). Indeed, from my perspective, the most enduring impact of the holistic A/R program I received so many years ago was an inadvertent outcome of the group setting. All the patients were housed together, and in our informal interactions we were able to share our experiences, encourage one another to wear the hearing aid, and most importantly to accept ourselves and the reality of the hearing loss.

The main challenge, as outlined by the authors, is not what to do but how to achieve the desired result. What can be done to increase the acceptance and implementation of a holistic approach to A/R (by consumers and professionals alike)? How can more third-party payers be sufficiently convinced of the merits of A/R so that they will underwrite much of the cost? What specific A/R procedures would be most cost-effective? The authors outline a number of potential research projects that can assist in determining the efficacy A/R procedures. Once the value of A/R is clearly demonstrated, then these other goals (i.e., more acceptance by both professionals and consumers and additional funding by third party payers) will more likely be realized.

The Future of Hearing Health Care Delivery

Fundamentally, the methods by which hearing aids are dispensed have been essentially unchanged for the past 60 years. The model still requires people to travel to a dispenser where all services related to the hearing aid are performed (interviews, audiometric testing, ear impressions, hearing aid selection and programming, and follow-up visits). For the last challenge, the participants visualize a future in which the service-delivery model completely changes its focus to one in which all tests and services can be obtained at home using personal computers.

They believe that this is a logical consequence of the modern explosion in technology, coupled to an increasingly technical-savvy, and younger, patient population. This population, they feel, is not only capable of self-testing via remote sensors, but prefer to receive their services in this fashion. These test results would then interface with computer controlled programs in which hearing aids are selected, individually adjusted, and then dispensed without the necessity of a user having any personal contact all with a human provider. They see a future in which a hearing aid is basically a “receiver,” one designed to accept multiple inputs such as e-mail, phone, MP3 player, FM, Bluetooth as well as serving as an appropriate sound amplifier, one that incorporates the recommended hearing aid features.

The new generation of tech-savvy consumers will likely welcome this extension of a hearing aid’s usual function; they will also likely welcome a service delivery model that places more of the responsibility in their hands. But, as the authors of the article caution us, there is a danger in placing all of our eggs in this technology basket. While technology may have been changing, human beings have not. The psychosocial impact of a hearing loss is not likely to change. People with a hearing loss will still be facing the same issues and exhibiting the same reactions they always did. Where the participants see as the role of audiologists in this techno-savvy future is as guides, professionals whose focus on the personal and rehabilitative needs of individuals transcends what is possible with a purely technological focus.

Summary

Of necessity, I omitted more material than I included in this review of the Clinical Research Summit. Each of these challenges deserves more space than can be devoted here. What they show me is the seriousness that hearing health care providers take their responsibilities. What these professional leaders say and do does eventually filter down to individual practitioners, and thus to the clients they serve us.

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