Clinical Protocol. Real Ear Probe Microphone Measurement Verification of Hearing Aids in Adults

Transcription

1 Clinical Prtcl Dcument N.: PROT-QA-02 Authrizatin: QA Cmmittee Apprved: Real Ear Prbe Micrphne Measurement Verificatin f Hearing Aids in Adults PURPOSE SCOPE BACKGROUND Verificatin prcedures are an essential cmpnent f successful hearing aid fitting. The purpse f Real Ear Measurements (REMs, als knwn as prbe-micrphne measures ) is t quantify the acustic utput r gain f the hearing instrument(s) in the client s ear canal and cmpare against a validated prescriptive frmula. Using REMs fr all hearing instrument fittings ensures that evidence-based standards are fllwed fr the verificatin f hearing instrument(s) fittings, culminating in an ptimal hearing instrument fitting fr the client. Registered hearing instrument practitiners and Registered Audilgists REMs using a prbe tube in situ in the client s ear canal have been established as the gld standard fr verifying hearing instrument fittings when initially fitting hearing instrument(s) n a client. Verificatin f a hearing instrument fitting has in the past been achieved using functinal gain in a sundfield r using simulated real-ear in a 2cc cupler. These ther methds have a number f shrtcmings (e.g., simulated real-ear in a 2cc cupler des nt take int accunt any venting effects); therefre, REMs are the recmmended verificatin methd in adults. REMs are bjective and accurate and ffer a mre meaningful metric than measures f functinal gain. They are critical fr assessing audibility, apprpriate utput fr different input levels, and verificatin f prescriptive fitting frmulas (Kchkin et al., 2010). Prescriptive fitting frmulas, such as NAL-NL1, NAL-NL2, and DSL V5a are evidence-based methds fr determining hw much amplificatin t prvide given a particular hearing lss. Using prescriptive targets measured with REMs at the initial fitting f hearing instrument(s) allws the clinician t ensure audibility fr cnversatinal speech, t set apprpriate amunts f amplificatin fr sft sunds, and t prevent lud sunds frm becming uncmfrtable. In the event that a client rejects the prescribed amunt f amplificatin, the fitting t targets is best thught f as a starting pint. The clinician has established that the hearing instrument is functining prperly and is capable f meeting prescriptive targets. If the client prefers less amplificatin, the prescriptive targets culd nw be cnsidered t be an amplificatin gal fr the client as they adapt t their hearing instrument(s). Hearing instrument manufacturers first-fit algrithms are knwn t deviate significantly frm actual prescriptive targets. Azah and Mre (2007) fund that using first-fit, 64% f hearing instruments failed t cme within +/- 10 db f target at ne r mre frequencies. After adjusting the hearing instruments based n REM results, targets were met 83% f the time within +/- 10 db. Similar results were fund fr pen-fit hearing aids (Azah, Mre, & Prasher, 2012). There is n way t knw if hearing instruments are meeting prescriptive targets withut perfrming REMs, which risks cmprmising audibility, r ptentially ver-amplifying at certain frequencies. Cntrlled dcument fr CSHHPBC use nly. Befre use, cmpare all print cpies t the fficial electrnic versin n the CSHHPBC website. Page 1 f 5

2 Clinical Prtcl Dcument N.: PROT-QA-02 Authrizatin: QA Cmmittee Apprved: Real Ear Prbe Micrphne Measurement Verificatin f Hearing Aids in Adults A measurement integral t successful REMs is the Real-Ear-t-Cupler Difference (RECD). Best practice is t perfrm RECD measurements n all adults, and this is a highly recmmended cmpnent f a successful hearing aid fitting. Cmplete details f the ratinale fr and applicatin f the RECD is prvided in Mdie, Seewald, and Sinclair (1994). The RECD allws the accurate cnversin f audimetric threshlds cllected with insert phnes frm db HL t db SPL (Scllie, Seewald, Crnelisse, & Jenstad, 1998) by adjusting the 2cc cupler calibratin values used with insert phnes. Hearing instruments and verificatin equipment all wrk in db SPL, making this cnversin crucial t ensure that apprpriate targets in db SPL are generated fr each individual client. By default, mst REM equipment defaults t average RECDs, but there can be significant variatins in adult ear canal sizes. This results in difference in residual ear canal vlume, which wuld require mre r less utput frm the hearing instrument(s) t meet targets (e.g., a smaller than average ear canal will require less amplificatin t meet a particular target, cmpared t a larger than average ear canal). The measurement f RECDs allws cmpensatin fr variatins in middle ear impedance and residual ear canal vlume, which can significantly influence the adult RECD (Bagatt, 2001). Mueller (2014) thrughly utlined the imprtance f REM and ratinale fr perfrming these measurements, alng with sme excellent examples. APPLICATION PARAMETERS REMS must be perfrmed and the hearing instrument(s) adjusted apprpriately: fr any new hearing instrument(s) received frm the manufacturer t be fit t an adult client at the time f initial fitting when there have been substantial changes in the client s audimetric threshlds (e.g., 20 db r mre at tw r mre frequencies r mre than 30 db at any single frequency) REMs shuld be perfrmed and the hearing instrument(s) adjusted apprpriately when: INTERVENTION the venting characteristics f the hearing instrument(s) have been significantly altered (e.g., changing frm an pen-fit t a mre ccluded fitting). earmld materials have been changed (e.g., changing frm lucite t silicn earmlds) a hearing instrument is repaired r remade (i.e., received back frm the manufacturer) REM Prcedures A number f detailed guides have been published describing the prcedures required t successfully perfrm REMs: Test Prtcls fr Prbe-Micrphne Measurements (Mueller Hawkins, & Nrthern, 1992) Real-Ear Measurement: Basic Terminlgy and Prcedures (Pumfrd & Sinclair, 2001) Guidance n the Use f Real Ear Measurement t Verify The Fitting Of Digital Signal Prcessing Hearing Aids (British Sciety f Audilgy, 2007). Cntrlled dcument fr CSHHPBC use nly. Befre use, cmpare all print cpies t the fficial electrnic versin n the CSHHPBC website. Page 2 f 5

3 Clinical Prtcl Dcument N.: PROT-QA-02 Authrizatin: QA Cmmittee Apprved: Real Ear Prbe Micrphne Measurement Verificatin f Hearing Aids in Adults Evaluating the Perfrmance f Digital Hearing Aid Features: A Real-Wrld Apprach (Brwn, 2008) Additinally, manufacturers f REM instrumentatin have detailed instructin manuals specific t their equipment, e.g., the Audiscan Verifit. Best Practices in Perfrming REMs In situ REM using prbe tubes must be used (rather than cupler measures) unless nt pssible. Every effrt must be made t perfrm REM in situ. If nt pssible, cupler simulated REM r sundfield functinal gain measurements wuld be required. Example situatins culd include: client physically unable t sit still thrugh the prcedure client in remte lcatin and unable t cme int the ffice deep-insertin hearing aid such as the Phnak Lyric Perfrm RECD measurements rather than using average values. Use f Speech Mapping r SPL-O-GRAM type utput measures is preferred ver Insertin Gain methds. Calibrated speech signals shuld be used whenever available. If the equipment des nt prvide calibrated speech, a speech-like signal shuld be used (e.g., mdulated speech nise). Obtain measures and adjust the hearing instrument(s) t target, at a minimum, fr: sft input levels (50-55 db SPL) average input levels (60-65 db SPL) lud input levels (70-75 db SPL) Maximum Pwer Output (MPO), ideally in cnjunctin with frequency-specific UCLs, which must nt be exceeded NOTE: Mre input levels can be tested when indicated. Open-fit hearing instruments r thse with very large vents cannt be verified using cupler measures. The reference micrphne f the real ear test system must be disabled during measurement, accrding t the prcedure specified by the manufacturer f the real ear equipment. Telecil perfrmance is best measured in situ, fr example using the Live Speech functin f a Verifit. REM systems can be used t measure and verify the cclusin effect. Directinal micrphne perfrmance can be assessed using REM test systems. Many REM systems have special tests t verify hearing instrument features, fr example nise reductin and incipient feedback. Cntrlled dcument fr CSHHPBC use nly. Befre use, cmpare all print cpies t the fficial electrnic versin n the CSHHPBC website. Page 3 f 5

4 Clinical Prtcl Dcument N.: PROT-QA-02 Authrizatin: QA Cmmittee Apprved: Real Ear Prbe Micrphne Measurement Verificatin f Hearing Aids in Adults DOCUMENTATION CLINICAL OUTCOMES REM results shwing that the hearing instrument(s) are capable f meeting the chsen prescriptive targets shuld be saved in the client file (either as print-uts r saved electrnically). If hearing instrument(s) settings preferred by the client deviate (either much less r much mre) significantly frm prescriptive targets, thse REM results shuld be saved in the client file (either as print-uts r saved electrnically). If instruments cannt be prgrammed r set t prvide adequate gain, a clinical nte must be entered in the client's file. Dcumentatin shuld be cnsistent with the CSHHPBC Standard f Practice Framewrk and clinical practice guideline CPG-04 Dcumentatin and Recrd Management. Clinical utcmes include: REFERENCES quantifying the acustic utput r gain f the hearing instrument(s) in the client s ear canals, taking int accunt the client s specific ear canal acustics as well as the hearing instrument(s) s venting characteristics cnverting accurately frm dbhl t dbspl fr the purpses f hearing aid fitting with the use f RECDs matching t prescriptive targets, eliminating manufacturer first-fit deviatins frm thse targets, and prviding an evidence-based amplificatin starting-pint fr the client. In the prcess: sft sunds are audible audibility and cmfrt are maintained fr mderate level sunds lud sunds are prevented frm becming uncmfrtably lud prviding a reference against which future hearing instrument electracustic utput may be measured Azah, H., & Mre, B. C. (2007). The value f rutine ear measurement f the gain f digital hearing aids. Jurnal f the American Academy f Audilgy, 18(8): Azah, H., Mre, B. C., & Prasher, D. (2012). The accuracy f matching target insertin gains with pen-fit hearing aids. American Jurnal f Audilgy, 21: Bagatt, M. (2001). Optimizing yur RECD measurements. The Hearing Jurnal, 54(9): Cntrlled dcument fr CSHHPBC use nly. Befre use, cmpare all print cpies t the fficial electrnic versin n the CSHHPBC website. Page 4 f 5

5 Clinical Prtcl Dcument N.: PROT-QA-02 Authrizatin: QA Cmmittee Apprved: Real Ear Prbe Micrphne Measurement Verificatin f Hearing Aids in Adults British Sciety f Audilgy. (2007). Guidance n the use f real ear measurement t verify the fitting f digital signal prcessing hearing aids. Retrieved frm /index.php?ptin=cm_cntent&view=categry&layut=blg&id=7&itemid=16 Brwn, M. (2008, August). Evaluating the perfrmance f digital hearing aid features: A realwrld apprach. Audilgy Online, Article 916. Retrieved frm Kchkin, S., Beck, B. L., Christensen, L. A., Cmptn-Cnley, C., Fligr, B. J., Krics, P. B., McSpaden, J. B., Mueller, G.,... & Turner, R. G. (2010). MarkeTrak VIII: The impact f the hearing healthcare prfessinal n hearing aid user success. Hearing Review, 17(4): Mdie, K. S., Seewald, R. C., Sinclair, S. T. (1994). Prcedure fr predicting real-ear hearing aid perfrmance in yung children. American Jurnal f Audilgy, 3: Mueller, H. G. (2014, January). 20Q: Real-ear prbe-micrphne measures - 30 years f prgress? AudilgyOnline, Article Retrieved frm Mueller, H. G., Hawkins, D. B., Nrthern, J. L. (1992). Test prtcls fr prbe-micrphne measurements. In Prbe Micrphne Measurements (pp ). San Dieg, CA: Singular Publishing Grup, Inc. Pumfrd, J., & Sinclair, S. (2001, May). Real-ear measurement: Basic terminlgy and prcedures. Audilgy Online, Article Retrieved frm Scllie, S., Seewald, R., Crnelisse, L., & Jenstad, L. (1998). Validity and repeatability f levelindependent HL t SPL transfrms. Ear and Hearing, 19(5): RELATED CSHHPBC RESOURCES PROT-QA-01 Adult Ear-Related Red Flags Medical Referral Criteria ACPG-06 Audilgic Management f Adult Hearing Impairment PROT-QA -03 Clinical Masking fr Audimetric Testing in Adults CPG-04 Dcumentatin and Recrd Management PRCS-P-01 Dcumentatin and Recrd Management POLICY-QA-05 Hearing Assessment and Hearing Instrument Fitting and Dispensing fr Adults Cntrlled dcument fr CSHHPBC use nly. Befre use, cmpare all print cpies t the fficial electrnic versin n the CSHHPBC website. Page 5 f 5