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In Situ Versus Coupler Verification Working Smarter ! Ed Brown Consultant Audiological Scientist MCHAS University of Manchester RECD Refresher Course 17th November 2004 What Needs to be Done ? Audiometry (Custom moulds & Inserts) HA Prescription Fine Tuning +++ 2 ears, 4 levels, 1 restless child In Situ HA Verification (50, 65, 80, 90) Comfortable verifying at 80 and 90 in real ear ? Speech Testing Programs, Use, Parent/Child Instruction Frequency Response Curves RECD Refresher Course 17th November 2004 What Else Needs to be Done ? Listening/Comfort Check Other Programmes Volume Control Disabled, enabled, what range ? Conductive Loss How much gain, what strategy ? New Earmoulds Completion/Collation of Questionnaires FM Balance/Advantage …and then the PC crashes RECD Refresher Course 17th November 2004 What Resources Do You Have? How many staff involved in a child’s review ? What are their skills, experience ? Do all staff in department work with children ? How long is your review appointment ? Variable in the UK 1 person 40 minutes 2 persons 2 hours MCHAS recommend 2 persons 90 minutes RECD Refresher Course 17th November 2004 So what are you going to do? RECD Refresher Course 17th November 2004 RECD Advantages One measurement not four Child does not need to be present once measured Can be measured/recorded elsewhere Gives the option to multitask Save the RECD You can build/rebuild (almost) everything from this Compile your own normative data Improve accuracy of “first fits” Easy to monitor changes in canal acoustics Pattern recognition RECD Refresher Course 17th November 2004 RECD Definition - = Difference between the SPL measured in the real ear and SPL measured in a 2 cc coupler. RECD Refresher Course 17th November 2004 Are RECDs Valid ? Yes The RECD/REDD will take you, on average, to within 1 dB of the ear canal SPL The error will never be more than 5 dB (in 95% of subjects) References: Munro KJ, Davis J. Deriving the real-ear SPL of audiometric data using the "coupler to dial difference" and the "real ear to coupler difference". Ear and Hearing 2003;24:100-10. Munro KJ, Hatton N. Customized acoustic transform functions and their accuracy at predicting real-ear hearing aid performance. Ear and Hearing 2000;21:59-69. RECD Refresher Course 17th November 2004 What about Transducer Type ? There are issues regarding transducer type/methodology when measuring RECD There are differences between using an Insert Phone and Hearing Instrument To do with acoustic impedances Most pronounce around 2k Hz May need to measure two RECDs ? References: Munro KJ, Salisbury VA. Is the real-ear to coupler difference independent of the measurement earphone? International Journal of Audiology 2002; 41:408-13. Munro KJ, Toal S. Measuring the RECD Transfer function with and Insert and a hearing instrument. Are they the same thing ?. 2004. In Phonak Focus 33. RECD Refresher Course 17th November 2004 Measure Each Ear ? Co operation may be limited Use one RECD for both ears In general differences are less than 3 dB Proviso: no significant wax, normal middle ear function Probably better than using predicted data Reference: Munro KJ, Buttfield, L. A comparison of real ear to coupler difference values in the right and left ear of adults using 3 earmould configurations, in press, Ear and Hearing RECD Refresher Course 17th November 2004 How Often ? Biggest changes occur within first 2 years of life RECD can be 20-30 dB for 1 month old Not a difficult (relatively) age to measure Ideally should be measured whenever new earmoulds provided In practice Every 3 months until 2 years of age ? Then every 6 months until 5 years of age ? Reference: Bagatto MP. Optimising your RECD Measurements. Hearing Journal 20001;54:32, 34-36 RECD Refresher Course 17th November 2004 RECD on Infant RECD Refresher Course 17th November 2004 Effect of OME RECD Refresher Course 17th November 2004 So… There are limitations to an RECD/Coupler compared to In Situ Approach… …but the clinical advantage for most children probably outweighs this RECDs are potentially useful for all children Adults also ? On going research Measure In Situ response if you can At subsequent review appointment ? RECD Refresher Course 17th November 2004 DSP Exchange (90 min) Pre-Visit (Audio on NOAH, LIFE & LSQ available (on PMS)) “First Fit” aids, previous audiometry, predicted RECD “Insert Phone Audiometry (Custom Earmoulds & Inserts) Assess VC, Processing and Program need Measure RECDs Prescription & Verification (2cc Coupler) Speech Testing Frequency Response Curves Questionnaire Completion Initial Evaluation, Hearing Instrument Orientation Programme RECD Refresher Course 17th November 2004 In Summary The Clinical Advantages Can be used to improve accuracy of some manufacturer “first fit” procedures Only require co-operation for one measurement rather than multiple real ear measurements Prescription can be verified in coupler without child present and/or “off line” More effective use of clinic appointment time Skills (e.g. insert PTA & RECD versus full prescription procedure RECD Refresher Course 17th November 2004