Enhancing the Initial Hearing Aid Fitting Michael Block, Ph.D. Session 0228 Importance of a Good Start The consequences of doing a poor job of selling the hearing-impaired client on a positive treatment option is that he/she will likely become more isolated, will see their quality of life continue to deteriorate, and may even experience serious depression and a variety of other problems that can be viewed as symptoms of their hearing loss. Kochkin, 2000 Rationale > All of the fitting targets and settings are based on the Hearing Levels. > Hearing levels are converted to SPL to Coupler to Hearing Aid using average correction factors. > Hearing aid gain to match target is based on average residual ear canal volume. > Only the patients know if the results meet their needs. Topics > In-Situ Audiometry Customizing the gain target > Integrated t Real-Ear measures Customizing the gain target match > Verify Comfort In-Situ functional measures In-Situ Audiometry > In Situ means that the measurement is made while the hearing aid is in the patient s ear > Goal of hearing instrument fitting is the performance of the hearing aid in the patient s ear In-Situ Audiometry Allows for calculating gain targets that represent your patient s actual fitting. Instead of using data for an average fitting. 1
In-Situ Audiometry > In Situ Audiometry takes into account residual ear canal volume >depth of the instrument in the ear canal seal in the ear canal >effects of venting specific receiver in that instrument Residual Ear Canal Volume When the hearing aid fits deeper in the canal the residual volume decreases As the residual volume decreases the sound pressure increases (for the same intensity of input). Effect of Insertion Depth The curves represent the mathematical variation one could expect if the depth of hearing-aid insertion were increased and decreased one and two standard deviations. re: Normal REIR db Difference 20 15 10 5 0-5 -10-15 -20-2 SD 28 mm -1 SD 30 mm Normal 32 mm +1 SD 34 mm +2 SD 36 mm 100 1000 10000 Frequency in Hz -2 SD -1 SD +1 SD +2 SD (DeJonge, 1996). In-Situ Audiometry > The signal is produced by a sine wave generator within the circuit > Thresholds are measured with only the hearing aid in the patient s ear > Targets are recalculated l using in-situ it thresholds > Use in-situ UCLs to set the maximum output levels of the hearing aid In-Situ Audiometry > In-Situ thresholds are generally better than ER-3A thresholds > Targets calculated using in-situ thresholds are more accurate since they represent the actual hearing loss Targets are based on the specific fitting not average data In-Situ Audiometry > Better starting point for Best Fit or to troubleshoot > All other process work better feedback control noise reduction compression settings 2
In-Situ Audiometry > Using the In Situ thresholds to calculate the target results in a better initial starting point and in the long run can save time > Fewer troubleshooting ti complaints associated with high frequencies, occlusion, or tolerance issues In-Situ Thresholds Normal vs. In-Situ Thresholds Clinical Validation > In-situ-based fitting success Subjects were sent home with Insert-earphone-based fitting in one memory and in-situ-based fitting in the other Subjects did not know which setting was in a particular memory Clinical Validation > In-situ-based fitting success They were asked to rate various situations for >Clarity >Loudness >Naturalness >Overall Sound Quality Memory preference was recorded Clinical Validation > N = 18 > Age Range: 42-74 yrs Mean = 66.4 yrs > All previous users of well-fit hearing aids based on probe-microphone verification 3
Clinical Validation average data Clinical Validation -10 0 10 20 Frequency (Hz) 125 250 500 1000 2000 4000 8000 IN SITU ER-3A Insert Ear Phone 12 10 In-Situ Audiometry vs. ER-3A db HL 30 40 50 60 70 B Change in db 8 6 4 80 90 2 100 110 120 0 250 500 1000 1500 2000 3000 4000 Frequency (Hz) CIC N=30 ears ITC N=10 ears (Ioannou, 2000) Fitting Preference Data of ts Number Subject 14 12 10 8 6 4 2 11 6 UCL Measures > Predicted VS Measured > Software allows the use of UCL measures at individual frequencies. > Use in-situ UCLs to set the maximum output levels of the hearing aid 0 IN SITU ER3 NO PREFERENCE Type of Audiometry 1 (Ioannou, 2000) In-Situ UCL Normal vs. In-Situ UCL 4
In-Situ Audiometry - Summary > Corrects the Hearing Levels based on the actual insertion depth of the hearing aid. > The corrected Hearing levels represent the actual test conditions for your patient. > The customized data are used to compute the gain requirements (targets) for each hearing aid for that particular patient. Survey > How many use Real Ear Measures with almost all fittings? > How many use it 50% of the time? > How many people never do real-ear measurement? How often do we use REM? Aud HIS Never 29.5 27.0 Occasionally 19.5 21.1 Less than half the time 13.2 8.9 Half the time 7.1 8.9 Most of the Time 11.5 13.0 Almost Always 19.2 21.1 Kirkwood D. Survey: Dispensers fitted more hearing aids in 2005 at higher prices. Hear J.2006;59(4):48 REM Survey Data > 2006 HR Dispenser Survey: More than half (57%) of dispensing offices possess REM equipment, but Only about one quarter (23%) use it routinely during adult hearing aid fittings. Strom KE. The HR 2006 dispenser survey. Hearing Review. 2006;13(6):34 Variables Affecting Target-Matching Accuracy > Transducer variability > Hearing Levels In-Situ measures correct this > Hearing aid size > Residual canal space variables > Vent size/slit leak Why Don t We Do Real Ear Measures? > Too expensive > Too much space > Too cumbersome > Too time consuming > Doesn t really help much > One Solution is to use real-ear measures 5
Too Expensive Takes too much Space $12,000 - $15,000 In a solo practice doing 5 units per week for 5 years $11 per unit Too Cumbersome Too Time Consuming > Boys Town National Research Hospital estimates 5 to 10 minutes per ear. > Then the data need to be uploaded to your hearing aid fitting system. > Estimate t about 30 minutes. If everything works smoothly maybe 20 minutes Doesn t really help much? Doesn t really help much? Conclusion: Initial fit may not tbe the best fit 9 Ears Identical Settings Variation: ~15dB Courtesy of Mike Valente, 2007 Yanz & Olson, 2006 6
Using Real Ear Measures > Is Real Ear a good idea? > If you could obtain Real Ear Measures (REM) in the fitting software in seconds, without any additional equipment in the office, would you do it? Standard Real Ear Loudspeaker Computer and monitor Microphone housing Probe tube Ear Loop Connect to PC (Noah) via Ethernet > No Additional equipment > Uses existing clinical space > No Additional cost > Very little additional time > Benefits of REM More accurate target match More successful Best Fit More knowledgeable fine-tuning Probe tube Programming connections > Can we expect that a simple integrated system will work as well as a complicated stand-alone system? > The key measure is the Real-Ear-Coupler Difference Measuring > If the residual ear cavity is smaller than the 2cc coupler cavity, the amount of SPL in the ear cavity is: 2cc coupler REM Background > If the residual ear cavity is larger than the 2 cc coupler cavity, the amount of SPL in the ear cavity is: 2cc coupler REM re SPL Mor Less SPL 7
Measurement with Commercial Device Measurement with Commercial Device > Apply electrical signal to transducer > Measure SPL generated in 2 cc coupler Audioscan Verifit > Apply same electrical signal to transducer > Measure SPL generated in the ear Audioscan Verifit SPL in Ear Canal REUR SPL in Coupler 2cc and Simulated Real Ear Respo onses (db SPL) Derivation of > Apply electrical signal to transducer > Measure SPL in coupler and in ear > = Real-ear SPL - Coupler SPL Real Ear SPL Coupler SPL (db) Audioscan Verifit Uses for > Predict real-ear acoustic behavior from known coupler behavior > Pediatric application > Manufacturing software uses average s to simulate real-ear performance based on known coupler performance Average vs. Measured Fikret-Pasa, Revit, 1992 8
Average vs. Measured Average vs. Measured Some s are smaller than average Other s are larger than average Bottom Line on Average > Average is sufficient for some ears > but not for others > You don t know if an ear is average unless you measure it > Integrated REM Sound generated through the hearing aid receiver Hearing aid microphone measures sound in the ear Measurement results integrated in Inspire OS and stored in the hearing aid No separate equipment or data entry required > Standard REM Loudspeaker generates sound sound Probe microphone measures sound in the ear Measurement results stored in database of fitting audiologist audiologist Separate equipment for measurement and data transfer > Real Ear system as part of the hearing aid Rear Ear Aided (REAR) >measurement of the hearing aid output (db SPL) while it is in the ear 2cc Coupler >measurement of the hearing aid output while it is in a 2cc coupler Real Ear to Coupler Difference () Average Measured 9
8.00 6.00 400 4.00 2.00 0.00-2.00 100 1000 10000 FFToMic BTE FFToMic ITE FFToMic ITC Two essential sets of data > Individual hearing aid coupler response Measured at the lab Stored in the Hearing Aid > Measured Measured in the ear Stored in the Hearing Aid From Real-Ear SPL to REAR > Add Microphone Location Effect (MLE) > Changes with Hearing Aid style > Quite consistent across subjects nge in db Relative Cha 8.00 6.00 4.00 2.00 0.00-2.00-4.00 Microphone Location Effects 100 1000 10000 Frequency in Hz FFToMic BTE FFToMic ITE FFToMic ITC Bentler and Pavlovic, 1989 Deriving REAR from Coupler Microphone Location Effects + = Relative Chang ge in db + -4.00 Frequency in Hz Mic Coupler Measured + + Location = Effects Individual REAR Integrated REM is used for all adjustments Integrated REM is used for all adjustments Change in Gain, Max Output, + = Compression Ratio, Compression Threshold + = Stored Coupler New Parameter Settings + = New Coupler New Coupler + = Stored New Real-Ear Aided 10
SPL) 2cc and Simulated Real Ear s (db Calculate Real Ear 2cc Coupler 70 db input (db) Real Ear Aided (REAR) minus 2cc Coupler =Real Ear to Coupler Difference Example Audiogram Target Matching Target Fit to REM Target: Average Ear matching ± 3 db Average Measured Fit to REM Target: non Average Ear Average Measured 11
Fit to REM Target: Average Ear modeling Average Measured Fit to REM Target: non Average Ear Average Measured BTE > Insert probe tube in ear canal > Start REM > Wait less than one minute > Replace RE earhook with standard earhook > is ready to be used ITE > Insert probe tube in ear canal > Start REM > Wait less than one minute > Remove probe tube from aid > is ready to be used Verify Comfort > Goal is to ensure that at a given frequency: Soft inputs are audible, yet perceived as soft Loud inputs are perceived as loud, but not uncomfortable Verify Comfort > Procedure to verify dynamic range: Patient is presented a series of soft and loud tones swept across frequencies Each side is verified individually Hearing Aid is muted during presentation >other side (if binaural fitting) is not muted Verify Comfort > Subjective measurement that verifies dynamic range Patient provides verbal response for the clinician Promotes interaction between patient and professional 12
Verify Comfort >Verify Comfort can be done: At the initial fit (Delivery) or first follow-up check to customize compression settings >Audibility for soft sounds >Loud sounds are loud but tolerable Troubleshooting tool used to resolve patient complaints Verify Comfort Verify Comfort > Loud is always 90 db SPL regardless of preferences > Soft is always 50 db SPL regardless of preferences > Make adjustments directly from this screen Verify Comfort > Provides an in-situ measurement to verify the patient s dynamic range. > Promotes interaction between the professional and the patient to achieve a better fit. Summary > We have learned how our hearing aids Create an individual target by allowing Hearing Levels to be measured through the hearing aid. (In-Situ Audiometry) Enable a precise target match by providing actual Real-Ear Coupler Differences. () Offer a system to verify the fitting assuring that soft sounds are clearly audible and that loud sounds are not uncomfortable (Verify Comfort) Thanks for your attention Do you have any questions? 13