10/24/2016 Probe-Mic Hearing Aid Verification: Can you afford NOT to do it? H. Gustav Mueller Professor, Vanderbilt University, Nashville, TN. Consultant, Sivantos Group Contributing Editor, AudiologyOnline Mueller Disclosures: Consultant, Sivantos Group Consultant, AudiologyOnline Author, Plural Publishing Owner, www.EarTunes.com Related reference material: http://www.audiologyonline.com/articles/20 q-today-s-use-14101 http://www.audiologyonline.com/articles/20 q-probe-mic-measures-12410 http://www.audiologyonline.com/audiology- ceus/course/probe-mic-and-speech- mapping-27179 1
10/24/2016 Probe-mic measures were in the news in back in 2009! July, 2009: Consumer Reports talks about buying hearing aids and hearing aid fittings What the article said: “Audiologists made fewer serious fitting errors than did hearing-aid specialists, but in about two-thirds of all of the fittings, patients ended up with incorrect amplification.” “The provider should do several tests to verify that they [hearing aids] are working optimally. Of that battery of tests, one stands out as a must-have: the real-ear test” 2
10/24/2016 September, 2009: Catherine Palmer talks about ethics and the fitting of hearing aids I f we talk about ethical practice, then we have to be comfortable saying that there are hearing health care providers who are not practicing ethically. There is not room for a statement like: I t’s okay that you aren’t following “Best Practices” by not measuring the output of the hearing aid you are fitting, and charging for your expertise but not using it. I f I ever, ever find out that one of you out there is not conducting probe-mic measures, you cannot hide. I will find you, I will track you down, and . . . Forgetting about ethics for a moment—do you know that every Best Practice Guideline written since 1990 (there are five of them) state that probe-mic measures should be used? 3
10/24/2016 What I read on “AAA SoundOff” “I’d like to talk to some of you out there who use probe to fit hearing aids. I just haven’t found that it makes any difference, and I’m not sure I want to invest the money for the equipment.” An important distinction: Probe-mic measurements are NOT a method of fitting hearing aids; they are simply measures to verify the audiologist’s method of fitting hearing aids. Is the hearing aid fitting “good enough” to allow the patient to walk out the door (or for you to swipe the VISA card)? verification: “substantiating or determining the truth or accuracy” This means that we must have a gold standard—something to verify. 4
10/24/2016 Selecting a gold standard for verification: Some considerations Maximize speech understanding? Maximize audibility? Maximize listening comfort? Maximize sound quality? Maximize patient “first acceptance?” Today, there really are only two prescriptive fitting methods to consider, both have been systematically researched and validated: The Desired Sensation Level (DSL) – Has been used since 1984, there have been several revisions, and the current version is DSL v5, available from most all manufacturers and on probe-mic equipment (but not as stand-alone software). Richard Seewald The National Acoustic Laboratories (NAL) – Has been used since 1976, many cut their teeth on the NAL-R (1986); then there was the non-linear version NAL-NL1, and today we use NAL-NL2, available from most all manufacturers, on probe-mic equipment, and there is a stand-alone version Harvey Dillon See detailed comparison conducted by Earl Johnson, published in JAAA a couple years ago, or see “condensed version” at 20Q 5
10/24/2016 Five audiograms used in analysis 100 1000 10000 0 100 1000 10000 0 20 20 Hearing Level (dB) A-1 Hearing Level (dB) 40 40 A-2 A-1 60 A-3 A-2 A-4 A-3 60 80 A-5 A-4 100 A-5 80 Frequency (Hz) 100 Frequency (Hz) NAL-NL2 versus DSL5.0 (adults) (average speech inputs) More Gain DSL More Gain NAL The bottom line: While somewhat different, for adults, the two methods do not differ greatly, and both the NAL and the DSL are considered to be a reasonable “starting point” for the hearing aid fitting. There is supporting evidence for both (more on that later). 6
10/24/2016 So, prescriptive methods seem to work pretty well . . . But to state the (hopefully) obvious: The “prescription” is for the hearing aid output in earcanal SPL. Therefore, the earcanal SPL must be measured, or otherwise you have no clue if you’re even close to the prescribed gain! Today’s probe-mic measures: What’s pretty much the same as 30 years ago? Verification is conducted for fitting targets displayed on the screen. The probe, regulating mics and sound delivery system is basically the same. The “technique” (placing the probe, positioning the patient, etc.) is basically the same. This book was the first time that all the probe- mic terminology was summarized in one source (although it has changed a little since then) 7
10/24/2016 Today’s probe-mic measures: What’s changed over the past 30 years? We tend to verify using “output” rather than “gain” We verify at several different input levels The input signal is now speech (or speech-like); the process is sometimes referred to as “speechmapping.” Today’s hearing aids have more special features to verify Fitting Targets Patient’s LDLs (in earcanal SPL) Patient’s Threshold Range Of Average Of (in earcanal SPL) Amplified LTASS Amplified LTASS And, in case you’re curious, this would be considered a “good” fitting! Fitting targets compared to patient thresholds for NAL-NL2 (left) and DSL V5 (right) 8
10/24/2016 Reasons why the targets are below the thresholds in the high frequencies: Consider the complete speech spectrum, not just the “average line.” You only have so much loudness to use—use it effectively. There is a point where extra audibility does not equate to increases speech understanding. The overall fitting must be reasonably “comfortable” for patients, or they will turn down gain and reduce audibility for ALL frequencies. This is not a good fitting This is an “okay fitting” (especially if patient has VC) This verification process is conducted for several different inputs (e.g., 50, 65 and 80 dB SPL) 9
10/24/2016 So, if probe-mic measures are: The intuitive thing to do . . . The right thing to do . . . The ethical thing to do . . . The evidence-based thing to do . . . Then everyone must be using them, right? From Mueller and Picou, 2010 Three common choices used by audiologists when fitting hearing aids ? 10
10/24/2016 The importance of audibility in successful amplification of hearing loss Ron Leavitt and Carol Flexer Hearing Review , 2012 What they did . . . Selected the premier product from each of the “Big Six,” and programmed these hearing aids to each manufacturer's recommended fitting. All special features were activated. For benchmarking purposes, they added a 7 th hearing aid—a circa 2002 single-channel analog instrument, which they programmed to NAL-NL1. What they did . . . The subjects were all experienced hearing aid users with typical downward sloping hearing losses. The subjects, fitted bilaterally, were tested with all seven sets of instruments. The speech recognition test was the QuickSIN, presented at 57 dB SPL. Following the initial testing, all hearing aids were re-programmed to NAL-NL1 and QuickSIN testing was repeated 11
10/24/2016 Performance for the aided QuickSIN presented soundfield at 57 dB SPL. Bars indicate “SNR-Loss”: The average SNR disadvantage compared to individuals with normal hearing HA-1 HA-2 HA-3 HA-4 HA-5 HA-6 OLD So maybe things have gotten better? Or the problem is only with one or two manufacturers? Protocol for Sanders et al, 2015 ( Data collected December, 2014) Selected the premier hearing aid from the five • leading manufacturers. Selected the manufacturer’s “default” fitting in the • software for typical downward sloping hearing loss; entered appropriate data for earmold plumbing, etc. Matched all fitting and patient characteristics • between software and probe-mic equipment. Conducted probe-mic measures using speech • mapping (male passage from the Verifit); 16 ears tested (8 male, 8 female) 12
10/24/2016 Input=55 dB SPL: Real Speech of Verifit System Output (dB) Frequency (Hz) Input=65 dB SPL: Real Speech of Verifit System Output (dB) Frequency (Hz) Input=75 dB SPL: Real Speech of Verifit System Output (dB) Frequency (Hz) 13
10/24/2016 SIIs for Manufacturer Proprietary Fittings and NAL-NL2 targets Speech Intelligibility Index Input=75 dB SPL: Real Speech of Verifit System Output (dB) Frequency (Hz) Relating the SII (soft intputs) to speech recognition 14
Recommend
More recommend
