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).