Validation of sonotubometry in healthy adults

Background: Frequent active opening of the eustachian tube (ET) allows ventilation of the middle ear and equilibration of pressure changes. Active opening is accomplished by the contraction of the paratubal muscles during swallowing. Because a disturbance of the ventilatory function of the ET may contribute to the development of otitis media with effusion, it is important to investigate ET function. Sonotubometry can be used to detect whether the ET can open or not during swallowing acts. Methods: We developed a sonotubometer to test ET ventilatory function in 36 healthy adults. The width of the test signal frequency was between 5500 and 8500 Hz (centre frequency of 7000 Hz) and the loudness was 95 dB. To test reproducibility, testing took place in two sessions of 10 swallowing acts each. Results: Opening of the ET could be registered in 91.6 per cent of the subjects in at least one of the two measurements. The first and the second measurements were highly correlated, with a Spearman's coefficient of 0.907. Conclusion: We confirmed that there is generally a good ventilatory ET function in otologically healthy adults, although, in a few cases, ET opening was not registered. Furthermore, we confirmed that our sonometric test equipment had acceptable reproducibility. Sonotubometry is a promising method for assessing ventilatory ET function. Research is ongoing to test the discriminative power of sonotubometry in children with various otological conditions.