Passive and dynamic properties of the eustachian tube: quantitative studies in a model

To question the conception of Eustachian tube (ET) dysfunction by investigating some of its passive and active properties.

Middle ear (ME) fluid accumulation accompanied by a negative pressure is generally accepted to be induced by ET dysfunction, implying that the origin of pathology is within the tube.

Pressure changes were continuously and directly measured in a ME model having human dimensions, constructed with a patent ET, and employing different mastoid sizes. Various liquids were introduced into the ME chamber while maintaining atmospheric pressure. The model was tilted to a 45 degrees angle below the horizon, causing the liquid to block the tympanic inlet of the ET. Then either the ME was opened to the atmosphere (simulating an insertion of a ventilating tube) and the ET was inspected for liquid passage through it, or the cartilaginous ET was compressed and opened, imitating the "pumping" action of the ET at the process of deglutition.

ET blockage produced a ME negative pressure in the range of -8 to -10 mm H2O. ET pumping caused a ME pressure change of 2 to 60 mm H2O, a greater change when a smaller mastoid was used.

ET obstruction by intratympanic fluid may cause a negative pressure in an ME having a normal, patent ET. Clearance of such fluid would be facilitated according to its viscosity. The ET pumping mechanism may play a major role in fluid transport and pressure regulation of the ME.