Introduction
Eustachian tube (ET) connects the middle ear (ME) cavity and nasopharynx and has three main physiological functions: ventilation of the ME, drainage and clearance of secretions produced within the ME and protection from nasopharyngeal sound pressure and secretions.1 The ET is usually closed under normal circumstances, opening happens either actively or passively. Passive opening occurs when the ET opens as a result of increased ME or nasopharyngeal pressure while active ET opening usually happens during swallowing.2 The ME is an air cavity which is highly susceptible to perturbations in atmospheric pressure and variations in middle ear pressure(MEP) most often occur due to passive diffusion of nitrogen between the ME and the nasopharynx.3 When the ventilatory function of the ET is impaired, normal gas transfer between the ME and nasopharynx is disrupted resulting in negative MEP and transudation of fluid from local capillaries. All this ultimately leads to otitis media with effusion (OME). In recent years, the incidence of diseases related to eustachian tube dysfunction(ETD), such as OME and adhesive otitis media has gradually increased. Some patients may require multiple tympanostomies or other surgical procedures because of chronic or recurrent OME (COME/ROME). To date, although the pathogenesis of ETD has not been completely elucidated, it has been suggested that ET ventilatory function could be closely related to the prognosis of COME.4 Therefore, accurate measurement of ET ventilatory function is essential to clarify the role of ETD in COME so as to formulate interventions and eventually, to be able to predict the efficacy of surgery.
A high-resolution digital manometer was used to perform the modified ME pressure-equilibration test5,6on ears with perforated tympanic membranes and those with ventilation tube inserted(VTI). Details of the tests were recorded to help us find clues to the pathogenesis of ETD. Our primary aims were: 1. to explore the roles of the two main components of ETD in the formation of COME, i.e., the resistance of ET opening and the contraction of the peritubular muscle, 2. to study the differences in magnitude and duration of ET opening between patients with COME and those with tympanic perforation (TP).