The 678 Hz acoustic immittance probe tone: A more definitive indicator of PET than the traditional 226 Hz method

Abstract

BackgroundThe accurate diagnosis of Eustachian tube (ET) dysfunction can be very difficult. Our aim is to determine whether a 678 Hz probe tone is a more accurate indicator of Patulous ET (PET) than the 226 Hz probe tone when used in compliance over time (COT) testing.MethodsTwenty subjects (11 normal ET ears and 7 PET ears) were individually seated in an examination room and connected to a GSI TympStar Middle Ear Analyzer. The order of probe tone frequency (678 or 226 Hz) was randomized. Baseline “testing” COT recordings for each ear undergoing testing were completed. Subjects were instructed to occlude their contralateral nostril and to breathe forcefully in and out through their ipsilateral nostril until the test had run to completion. This process was repeated with the probe tone that had not been previously run. For the control group, each subject had one random ear tested. For the experimental group, only the affected ear(s) was tested. Wilcoxon rank rum tests were performed to determine statistical significance.ResultsThe baseline COT measurements for the control group and PET group were similar, 0.86 mL (SD = 0.34) and 0.74 (SD = 0.33) respectively. Comparing the 226 Hz tone between groups revealed that PET patients had a median COT difference 0.19 mL higher than healthy ET patients, and for the 678 Hz tone, PET patients had a median COT difference of 0.57 mL higher than healthy ET patients. Both were deemed to be statistically significant (p = 0.002, p = 0.004 respectively). The was a statistically significant median COT difference between the 678 Hz and 226 Hz of 0.61 mL (p = 0.034) for the PET group, while the same comparison for the control group of 0.05 mL was not significant (p = 0.262), suggesting that the 678 Hz tone yields a larger response for PET than the 226 Hz tone, and no difference for the control group, thus making it less prone to artifact noise interference.ConclusionThe 678 Hz probe tone is a more reliable indicator of ET patency, and should be preferably used over the 226 Hz tone for future COT testing.

Patulous Eustachian tube (PET), a practical overview

“…We have shown that a 668 Hz probe tone is more sensitive and has fewer false positive results than a 226 Hz probe tone when using this method of diagnosis 12 …”

“…We have shown that a 668 Hz probe tone is more sensitive and has fewer false positive results than a 226 Hz probe tone when using this method of diagnosis. 12 Other tests that have been reported include nasal audiometry, in which a sound is presented in the nose, and the audibility in the ear is measured. This has been reported to show good results in the Japanese literature, 13,14 but in our own experiments in a Caucasian population, we have found it of limited use.…”

Ambient pressure tympanometry in the workup of patulous eustachian tube and neurotologic disorders

“…Several proposed algorithms involve assessment for respiration-synchronous tympanic membrane (TM) movement on otoscopy or tympanometry or nasopharyngeal pressure measurement with specialised equipment. [2][3][4][5] However, nasopharyngeal pressure measurement is time-intensive and requires expertise. Clinicians may benefit from a simple diagnostic test performed during routine audiology workup.…”

“…Ambient pressure tympanometry (APT), an established but infrequently employed test for PET, measures TM compliance over 20 seconds without external pressure changes and can be performed on most versions of standard tympanometry equipment. APT may demonstrate pulse‐synchronous waveforms associated with SSCD and other neurotological conditions 6,7 or respiration‐synchronous waveforms during respiratory manoeuvres, which are associated with PET 3,5,8 …”

“…APT may demonstrate pulse-synchronous waveforms associated with SSCD and other neurotological conditions 6,7 or respiration-synchronous waveforms during respiratory manoeuvres, which are associated with PET. 3,5,8 In this study, we measure the sensitivity and specificity of APT for PET and compare the sensitivity of various respiratory manoeuvres. We further analyse a subset of patients with suspected PET that demonstrated pulse-synchronous APT waveforms at rest and displayed radiographic findings supportive of alternative neurotological processes.…”