Abstract
BackgroundSonotubometry is a non-invasive means of assessing Eustachian tube (ET) function. Its interpretation remains a complex task with questionable results due to wide variation between trials. A study was conducted to ascertain whether the measurement of phase shift in sonotubometric signals would be a more reliable indicator of ET patency than fluctuating Sound Pressure Level (SPL).MethodsThe ears of six healthy participants and two participants with patulous ET (PET) were probed with a 100 Hz signal. Five recordings of SPL were performed at the external auditory canal. Cross-correlation was performed among filtered SPL signals and among extracted phase shift waveforms. Peak coefficients were averaged to provide a measure of waveform similarity between trials.ResultsMean peak cross correlation coefficient for SPL signal measured 0.603 ± 0.057 Standard Error of Mean (SEM) whilst that for Phase-Shift signal measured 0.884 ± 0.027 (SEM). All normal participants demonstrated an observable phase change between the ear and nasal signal during swallowing indicating an acoustic impedance change during the event. For the PET patients tested, the phase measurements in ear and nasal signals follow one another reasonably closely, indicating little or no impedance change during swallowing. It is thought that this impedance change is indicative of opening of the ET in normal patients, and the lack impedance change indicates ET either remaining open or remaining closed throughout the swallow.ConclusionsExperimental data suggest that phase-shift detection is a more consistent means of interpreting sonotubometric data than SPL analysis.
Highlights
Sonotubometry is a non-invasive means of assessing Eustachian tube (ET) function
A large negative phase shift is visualized in the recording at the ear during the swallowing period indicating reduced lag or impedance. This could suggest that there is an opening of the ET during this time period that would coincide with the swallowing action
Previous attempts have used the detection of Sound Pressure Level (SPL) and their standard deviation from the mean to infer the state of the ET, the SPL of the test tone may or may not be consistent in the nasopharynx complicating the interpretation of the SPL data at the external auditory canal
Summary
Sonotubometry is a non-invasive means of assessing Eustachian tube (ET) function. Bordered laterally by the tympanic membrane (TM) and medially by the inner ear, ventilation and pressure equalization are achieved through the periodic opening of the Auditory canal or Eustachian tube (ET) [1]. Maximum power transmission occurs when the pressure on either side of the TM are equal – a state described as impedance matched. Auditory tube dysfunction is subjectively assessed, limiting the ability of physicians to detect the early signs of ET dysfunction and objectively assess the efficacy of surgical and medical interventions.
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Schedule a callMore From: Journal of otolaryngology - head & neck surgery = Le Journal d'oto-rhino-laryngologie et de chirurgie cervico-faciale
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