Evaluation of the structural patency of the Eustachian tube by sonotubometry

<p>Sonotubometry is commonly used for the qualitative (yes/no) detection of active Eustachian tube (ET) opening during swallowing. This study was designed to evaluate whether the external auditory canal sound amplitude (ESA) and duration of ET opening (DETO) of sonotubometry have quantitative information about ET structural patency. Fifty-seven ears with tympanic membrane perforation and 53 contralateral ears without perforation from 55 patients (male:female, 26:29; mean age, 47 years) were included in this study. A commercially available clinical equipment (JK-05A, RION Co., Japan) was used to record the following: the input sound pressure (ISP) level of sonotubometry, ESA, and DETO; ET opening pressure with Valsalva maneuver (VP); and passive opening pressure (POP) with the passage test, which quantitatively measures passive and structural patency of ET. POP was not recorded in 53 years without tympanic membrane perforation, as the test needs perforation. With the VP, 43% of ears did not appropriately complete the maneuver due to the complex task of the maneuver. With the passage test, normal, stenotic, and patulous ETs were found in 70%, 28%, and 2% of ears, respectively. There are statistical correlations between ESA and DETO in tympanic membrane with (r = 0.88; 95% CI, 0.80–0.93; p < 0.0001) and without perforation (r = 0.93; 95% CI, 0.87–0.96; p < 0.0001). ESA (r = –0.50; 95% CI, –0.68– –0.27; p < 0.0001) and DETO (r = –0.46; 95% CI, –0.65– –0.21; p = 0.0004) were significantly correlated with POP. ISP did not correlate with POP (p = 0.21), while VP was correlated with POP (r = 0.37; 95% CI, 0.043–0.62; p = 0.024). The area under the ROC curve (AUC) suggested that ESA (AUC = 0.78; 95% CI, 0.65–0.92; p = 0.0010) and DETO (AUC = 0.78; 95% CI, 0.64–0.92; p = 0.0011) can predict ET patency. For the diagnostic test for stenotic ET, the ESA cut-off value was set at 8 dB by the Youden index, and the stenotic ET on sonotubometry also had a high risk of stenosis of structural patency with an odds ratio of 19.1 (95% CI, 4.2–89.7). Ninety-four percent of non-stenotic ears on sonotubometry were also non-stenotic on structural patency. This study demonstrated that ESA and DETO have quantitative information about the passive ET function.</p>