Interview with Patricia Stelmachowicz Ph.D., Director of Audiology, Boys Town, Omaha, Nebraska

Topic: Pediatric Hearing Aid Reflections

Beck: Good Morning Dr. Stelmachowicz. Thanks for giving me a few moments of your time.

Stelmachowicz: My pleasure Dr. Beck.

Beck: For the readers, I should mention that as we speak we're at the Phonak Pediatric Conference in Chicago, and it's November, 2004.

I was very impressed with your presentation and I'd like to highlight a few thoughts and ideas from your talk -- starting with the fact that kids are not just small adults...they are very different in all respects, and they must be tested, fitted and managed differently.

Stelmachowicz: Yes, that's an important point, and one that really carries a lot of weight. Pediatric fittings need to consider intellectual, academic, social growth, and of course, physical growth too. We're not just allowing them to hear again, as we often do with adults, rather we are preparing children and allowing them to learn. So, pediatric fittings require a very different approach.

Beck: I totally agree...and that's why I personally break out in a cold sweat when I have to fit children! Pat, if you don't mind, may I ask a few questions based on the notes I wrote during your talk?

Stelmachowicz: Absolutely.

Beck: OK then.....You made one comment about early digital hearing aids, that I have heard previously, but I think it's very important, and I'd like you to repeat it for me. It had to do with similarities and differences between early digitals and advanced analogs.

Stelmachowicz: Sure. I think you're referring to the fact that early digital technology was a bit disappointing for users and professionals and in retrospect, that makes a lot of sense. When you think about it, so many people were promoting the "digital" issue, and comparing it to "CD-like" sound quality and really building it up. But in reality, what happened was that manufacturers built digital hearing aids, based on the assumptions and realities of the more sophisticated analogs devices. So, the early digital aids were in essence, digital versions of analog aids, and as a result, we saw little tangible differences in the outcomes of the fittings. Patients still had occlusion, feedback, and they had difficulty in noise.

Beck: So we upgraded the circuits electronically, but because the early digital circuits were modeled on previous analog circuits, and because they faithfully reproduced those attributes, we got pretty much the same old results?

Stelmachowicz: Yes, that's what happened in the early days. As a profession and as an industry, we hadn't yet figured out how to use digital signal processing within the new hearing aids to really improve speech processing. But recently, digital achievements have opened-up many new processing opportunities.

Beck: Are we at the point yet, where we have outcomes or evidence-based studies, that can tell us with certainty, that fitting children using X, Y or Z is the best way to fit children, due to A, B or C?

Stelmachowicz: No, not really. We're approaching that, but we're not there yet. Comprehensive studies to determine when to use which technology to maximize pediatric fittings have not been conducted.

Beck: But you do have some general recommendations regarding directionality, wide dynamic range compression and noise reduction?

Stelmachowicz: Yes, but the jury is still out on some issues. While wide dynamic range compression may be good for almost all children, the use of directional hearing aids for children may be age dependent. For example, suppose the directional mics are really good, and they are focused on the front -- what happens if a bus approaches from behind, or what about other warning signals or conversations originating from the "null"? Older children who are capable of deciding when to engage a directional microphone are likely to benefit from the technology. Regarding noise reduction, my concern is audibility. I think it's entirely possible that some of the noise reduction circuits do actually remove some of the speech cues in tandem with the noise, and so the question becomes is it better to reduce the noise or deliver the full speech spectrum? Frankly, there are no studies out there providing us with that answer, so I have to assume the larger priority is to deliver the full speech spectrum until proven otherwise.

Beck: And to my way of thinking, it's not likely that we'll really have studies comparing "treated" versus "untreated" children in the near future, as it would likely be unethical to perform these studies. In other words, you can't continue to expose children to treatments that are negative, nor can you withhold treatments that are beneficial, so this is not a problem that will be solved in the near future! Pat, I know that for many of us, we base our adult fittings on non-linguistic considerations such as; frequency considerations, temporal and amplitude cues and other physical and psychological attributes related to sound. But when fitting children, as you mentioned above, there's more to consider. What can you tell me about linguistic considerations?

Stelmachowicz: There's quite a lot to consider regarding linguistics. For example, we know that when listening to soft speech, or speech-in-noise, speech in reverberation etc, children wearing hearing aids are not doing as well as normally hearing children in those same challenging situations. Children who are learning speech do not yet have a firm "code" for speech. They have not yet learned to use alternate acoustic cues or semantic knowledge to "fill-in-the blanks" as a late onset hearing impaired adult might do. Gaps in the message can occur at the phoneme level, the word level and even the sentence level, and as a result, the young children kids may not be able to make sense of the message. So to get the same performance from hearing impaired children as we get in adults, we need greater audibility and a better signal-to-noise ratio. This is very important and a great place to focus our efforts.

Beck: Pat, can you recommend specific websites, phone numbers or addresses where professionals can locate and acquire tools to use for assessing children and to measure their success?

Stelmachowicz: Sure Doug.

Pediatric Amplification Protocol:
www.audiology.org/professional/positions/pedamp.pdf

Phonak Pediatric Resources for Professionals:
www.phonak.com/professional/pediatrics.htm

Resources for Parents
www.babyhearing.org/

Beck: I know you have to run, but can you tell us a little about the 12 kids you've been following in your longitudinal study at Boys Town?

Stelmachowicz: Yes, well briefly...what we found was that normal hearing children outperformed hearing impaired children, and as you might expect, children who were identified early, have done better than children identified late. With respect to language development, our data as well as that of others, suggest than hearing impaired children who were identified early, performed at about the 25th percentile of children with normal hearing. So there is much room for improvement in terms of signal processing and hearing-aid optimatization with this population. Our data suggest that the bandwidth of signals processed by hearing aids may not be optimal for pre-lingually hearing-impaired. For example, sounds like /s/ and /z/, which have a very important role in language development in English, may not be clearly audible when processed by hearing aids, particularly when listening to female and child talkers. Interestingly, the bandwidth of cochlear implants is not restricted in this way. Our studies with young hearing-impaired children suggest that fricatives are delayed more than other speech sounds; it is our opinion that the relatively narrow bandwidth of current hearing aids may contribute to these delays. So, this is one area that needs further study.

Beck: Once again showing that simply identifying children and placing amplification on them just isn't enough.

Stelmachowicz: Right. They need very high quality sound, strong parental support, and a well-designed rehabilitation program to do really well.

Beck: Thanks so much Pat. I enjoyed your presentation here at the Phonak Pediatric Conference, and I think you brought up a million great points, thanks too for chatting with me.

Stelmachowicz: Thanks Doug. It's been a great conference, and I enjoyed reviewing my work with you. Thanks for your interest.

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