OAE screening: a quick test with a lasting impact
Peter Bray, Ph.D., Interacoustics’ OAE specialist, has more than 35 years’ experience when it comes to otoacoustic emissions (OAEs). A good proportion of his career, he has focused on capitalizing on technological advances to increase the speed and reliability of OAE measurements.
When Peter Bray started working with OAE in the 80s, there was no such thing as a neonatal hearing screening. At the time, the infant hearing test was conducted at eight months of age using a rattle in the behavioral distraction test. Despite the best endeavors of the health visitors performing the test, it was only able to detect around 50% of the children with a hearing impairment. As a result, the average age of detecting a hearing impairment in children was around two and a half years of age.
According to Peter Bray:
- The consequence of this was late fitting of amplification and language delay and often resulted in attendance at a special educational facility.
The birth of screening
In the 80s, Peter Bray was a researcher with Professor David Kemp, the pioneer of OAEs. In a slightly more modest technological age, Peter Bray describes clinical OAE testing in 1984:
- We used a mini-computer the size of a large filing cabinet. Considered state-of-the-art at the time, patients had to breathe very quietly and avoid swallowing as we lacked processing power to employ noise rejection. Babies tend to be noisy breathers and make many other sucking and swallowing sounds.
Peter Bray was made aware that noise was the major obstacle in neonatal OAE testing. A publication by Claus Elberling would change matters, however.
- I then saw the publication by Claus Elberling and co-workers, which showed he had tested 20 neonates. This provided the impetus to rewrite some of the core code of the algorithm, so that we could reject patient noises, he explains.
Not long after, a young mum presented at the clinic with a newborn baby. Peter Bray remembers the day clearly:
- The infant refused to settle for the test until the mother decided to start feeding it. The noise rejection method was able to obtain tiny bursts of clean signal in between the sucking and swallowing noises. In less than a minute, we were able to report that her baby had normal cochlear function.
One false pass or refer is one too many
Typically, one out of every 1000 babies is born with hearing loss. This presents two big challenges in hearing screening. Peter Bray elaborates:
- Firstly, we must never miss that one child, as it could have a profound and lasting impact on their life. Secondly, we must not be over cautious, as this would impose a high cost on the diagnostic department and a degree of anxiety on the parents as they wait to find that their child can hear perfectly normally. The two challenges relate to the sensitive nature of screening equipment and ensuring that it makes the correct decision time after time.
- We can run hundreds of tests in the presence of recorded realistic noise environments to ensure that our algorithms are correct. However, the OAE signal from the cochlea contains the same kind of frequency content as the noise from the patient and the room. Therefore, the algorithms are optimized to harvest as much of the cochlea signal and reject as much of the noise as possible, Peter Bray says.
A deep passion for OAE
Despite his long career in OAE, Peter Bray shows no lack of enthusiasm:
- I am fortunate to be part of a team with a deep understanding of the human hearing pathway, probe and ear canal acoustics, middle ear behavior and so forth. I have no doubt that we will continue to roll out better and better OAE screening instruments in the years to come. I predict that the screening instruments will provide a more detailed picture of the neonate ear and will further reduce the diagnostic investigation workload.