Question
I have a problem acquiring OAE results in infants from birth through about two months of age. Our protocol is to provide hearing screening on all children before their discharge, especially those within the high risk register. My problem is essentially fixing the ear tip inside the baby's very narrow ear canal. It is difficult to get a clear, artifact-free response. Do you have suggestions on how to get better OAE recordings on these tiny ears, or should we just screen with ABR?
Answer
Many screening programs in well baby nurseries effectively perform OAE measures. However, they likely did not achieve this effectiveness instantly. The literature shows a significant learning curve for new testers and new programs. Some regulations even state that the criterion performance for a program need not be achieved for the first year of testing. This indicates that practice makes perfect and that perseverance will eventually improve performance.
First, I assume that you are concerned primarily with the "Could not test" cases rather than the "Refer" cases. A "Refer" result can be correct but due to amniotic fluid in the ear canal. A "Could not test" result can be caused by inability to obtain a probe seal, inability to attain a calibrated stimulus because of blocking one or more of the probe tubes against the ear canal wall, and finally because of too much acoustic noise (both baby noise and environmental noise). Here are some things to try. For probe seal problems try the newer probe tips that have ridges that may make it easier to obtain a probe seal in even tiny ears. For probe-tube blockage problems, try ear manipulation (gently pull pinna back) to open the ear canal. For acoustic noise problems, locate the source and try to control it (talking by testers or Moms is a common source). Finally implement a systematic tester training program that attempts to use the same testers, allows documented discussion between successful and unsuccessful testers, and careful documentation on the exact rate of failures including isolating the exact cause for the failures (probe seal, probe blockage, noise, wiggly baby, etc.) Once these data are collected then you can concentrate on the specific problem.
Some professionals (me included) contend that a baby at risk should have both OAE and ABR testing. A viable protocol may be OAE on all babies, then add ABR on at risk babies.
Gerlad Popelka, Ph.D. is a professor, research neuroscientist and audiologist. He also is involved with creating and commercializing new technology including the first all digital hearing aid and the first neonatal screening device that combined otoacoustic emissions and auditory screening capability in a single hand held unit. He can be reached at geraldp@mac.com.