In Situ Versus Coupler Verification Working Smarter !

1
In Situ Versus CouplerVerificationWorking
Smarter !

• Ed Brown
• Consultant Audiological Scientist
• MCHAS
• University of Manchester

2
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

3
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

4
What Resources Do You Have?

• How many staff involved in a childs 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

5
So what are you going to do?
6
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

7
RECD Definition
-

Difference between the SPL measured in the real
ear and SPL measured in a 2 cc coupler.
8
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
200324100-10. Munro KJ, Hatton N. Customized
acoustic transform functions and their accuracy
at predicting real-ear hearing aid performance.
Ear and Hearing 20002159-69.
9
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 41408-13. 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.
10
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
11
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 200015432, 34-36
12
RECD on Infant
13
Effect of OME
14
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 ?

15
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
Questionnaire Completion
Frequency Response Curves
Initial Evaluation, Hearing Instrument
Orientation Programme
16
In SummaryThe 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