Trimming Eartips and ABR Responses

Question

We have a technician who trims the length of the eartips for infants so that they will sit better in a baby's ear with insert tubing. In infant screenings, she is just simply looking for the appearance of wave V and not necessarily latency and amplitude. Should I be concerned about a variance in the output when the black straw is half of its original length?

Answer

Any change in length of the insert phone tubing or tip length will change the physical characteristics of the stimulus. This includes the stimulus timing, frequency response and stimulus level. As the system is calibrated to the transducer, any change to the properties of the transducer characteristics will change the calibration. Thus, shortening the length of the tip or tubing would make the calibration inaccurate.

Since your technician is not looking at latency or amplitude but simply the presence or absence of the waveform, I don't believe any grave mistakes could be made. However, this is not good practice and it must be noted that the stimulus is not calibrated properly. This could be considered a liability for your facility.

Most manufacturers of evoked potential equipment sell appropriate adaptors for insert earphones that fit a variety of ear canal sizes including newborns. I would recommend contacting the manufacturer of your equipment to determine what adaptor is available.

Jill Craig is the product manager for Evoked Potential products at GN Otometrics. She is a graduate of the University of Tennessee-Knoxville with a degree in Audiology. After working for an otologist, Jill spent 12 years as distributor for audiology equipment before moving to the manufacturing side of the business.