Eustachian tube pressure equilibration. Temporal analysis of pressure changes based on direct physiological recordings with an intact tympanic membrane

a b s t r a c t Eustachian tube function is important in pressure regulation of the middle ear. The efficacy or magnitude of pressure equilibration by tube openings should be determined by the gradient between middle ear and ambient pressure, but in theory also the duration of the tube opening may play a role. This study employed direct measurements of middle ear pressure in patients, who after parotidectomy had a catheter inserted into the mastoid with a pressure transducer connected. Thus, monitoring of the middle ear pressure in response to experimentally induced pressure changes could be performed under physiological conditions with an intact tympanic membrane. A set of six experiments was performed in four healthy subjects with different pressure deviations, where the counter-regulation was recorded over 10 min's time frames; a total of 75 events of tube openings were recorded. The transducer had a high accuracy of AE0.1 daPa, and data were sampled at 10 Hz, so that detailed parameters for each tube opening event could be obtained: the pressure change, the pressure gradient, and the duration of the opening were determined. The pressure changes in response to Eustachian tube openings showed significant positive correlation to the pressure gradient and ambient pressure (p < 0.001). However, the duration of the opening time was not related to the pressure gradient (p ¼ 0.16), as well as the pressure change was also not related to the duration of the opening time (p ¼ 0.34). This meant that the magnitude of a pressure equilibration during tube openings was only determined by the pressure gradient and not variations in the duration of the opening time. Additional correlations were investigated including the pressure change rate. In conclusion, under physiological conditions the opening of the Eustachian tube behaves similarly to a reflex mechanism with relative constant duration. Therefore, in order to equilibrate higher pressure gradients, series of Eustachian tube openings are needed, rather than the tube will open during a longer period of time