Advantages of RECD measurements with infants and young children
First, the measure is quick. Children may have a short window of cooperation for real ear testing procedures. With practice and with appropriate distraction for the child, RECD measures can be completed in less than 5 minutes per ear. All other electroacoustic measures and hearing instrument adjustments can be completed in the 2 cc3 coupler without the child present.
Third, the measure can be used with any age child. Audiologists are at a particular disadvantage when fitting hearing instruments on infants younger than 6 months. Threshold information is typically limited to ABR responses and behavioral testing is not possible for either unamplified or amplified conditions. Using the RECD with 2cc coupler measures allows the audiologist to fit and evaluate the response of a hearing instrument before behavioral threshold testing can be completed.
Measure and mark the insert tube for the appropriate insertion depth (10-15 mm from ear canal entrance or 20-25 mm from intertragal notch)
Determine shape and length of canal before placing probe-tube
Ensure appropriate insertion depth after placing probe tube.
Note any wax or drainage that may prevent making the RECD measure
Note the presence of PE tubes / TM perforations / Otitis Media. All of these conditions can have an acoustic effect on the RECD
Lubricate the probe tube
Lubricate the earmold
Pre-measure the 2cc coupler response before seeing the child
Pre-mark tubes to correct length
Stabilize the probe tube before inserting the earmold using FunTac, lubricant, tape or the strap of the probe microphone itself
Practicing on others before making the real measure will increase your comfort level
Have Toys, Bubbles or Mirror ready before testing starts
Use a second examiner or helpful parent to keep the child distracted. In the RECD procedure illustrated above, a second examiner was present, although out of camera range.
Using a least-restrictive hold generally makes for a happier baby and more reliable measures
Troubleshoot Your Measurement:
Know what to expect so you know when something isn't correct!
Look for high frequency roll-off or negative values in the low frequencies
What if I just can't measure the RECD?
Between-ear RECD values are highly correlated (Tharpe, et al, 2001, Munro & Buttfield, 2004). The measured RECD from one ear can be used to predict the second ear RECD, unless an obvious difference between ears is found. Differences may be related to ear malformations, middle ear effusions or TM perforations.
Average RECD values do exist, though individual variability from age-related averages is high
Using average values is better than ignoring the RECD completely
Using average values is better than using functional gain which has no estimate of output or audibility