Question
When testing for thresholds using click and tone burst ABR, can a patient with loud strider or excessively loud snoring affect the accuracy of the threshold results? In other words, is it possible for the threshold results to be elevated? If so, is there a correction that is used or do you just report fair reliability due to patient noise?
Answer
There are some variables that should be addressed with your question.
If the stridor is creating unwanted myogenic activity or postauricular muscle activity (PAM), then you will not be able to collect any evoked potentials due to excessive physiological (not acoustic) noise. I've had occasions of conducting evoked potentials in patients with blepharospasms, and found even orbital muscles will impede testing.
If the acoustic energy (SPL) of the snoring is of concern, it's important to remember when placed appropriately, the insert earphone can provide a ~30 - 45 dB attenuation while testing. Not knowing the intensity level of the stridor or snoring, it is difficult to determine a correction factor that might need to be enforced. BUT, it is most unlikely that the acoustic energy of snoring would significantly interfere with the testing.
From a pragmatic point of view, it certainly wouldn't hurt to collect the evoked potentials during the noise peak and compare to the quiet phase to determine if there is quantifiable interference in the threshold testing. However, any time there are any transient environmental sounds during testing, the examiner is well advised to pause the collection during those "noisy" times and resume after the noise peak passes. In all cases, if there are unusual circumstances that occur during testing, it is important to document the issues and concerns with explanation of what the examiner did to reduce the impact.
Dr. Jackie L. Clark currently is a Clinical Assistant Professor for the University of Texas at Dallas at the Callier Center for the AuD Program, and an Adjunct Research Associate for the University of Witwatersrand in Johannesburg, South Africa. When she isn't teaching or conducting research she has carried a clinical case load for the past 22 years. She is the Managing Editor for the International Journal of Audiology and resides close to Dallas, Texas. Dr. Clark can be contacted via email (jclark@utdallas.edu).