Wj. Doyle et Cm. Alper, A model to explain the rapid pressure decrease after air-inflation of diseased middle ears, LARYNGOSCOP, 109(1), 1999, pp. 70-78
Objectives: Air-inflation in humans and monkeys with significant negative m
iddle ear pressure or with middle ear inflammation was shown to cause great
er than ambient middle ear pressure initially, followed by a rapid rate of
pressure decrease to approach the preinflation value. Study Design: A mathe
matical model of middle ear pressure regulation is presented and used to si
mulate air-inflation of the normal and diseased middle ear. Materials and M
ethods: The model represents the total volume of the middle ear as consisti
ng of three subcompartments representing the airspace, effusion, and mucosa
/blood. Gas exchange among those compartments was assumed to be diffusion l
imited, and the gas exchange between the mucosa/blood compartment and syste
mic blood was assumed to be perfusion limited. Disease was modeled as an in
crease in mucosal blood flow or, alternatively, as an increase in the volum
es of the effusion and mucosa/blood compartments. Results: The predictions
of the model agree better with the experimental data when the increased rat
e of pressure change after middle ear inflation in diseased ears is driven
by an increased volume of the effusion compartment as opposed to an increas
ed perfusion rate. The responsible mechanism is a rapid redistribution amon
g subcompartments of the gas volume introduced into the air compartment. Co
nclusions: These results suggest that middle ear inflation with inert gas c
an be used to diagnose the presence and relative amount of middle ear effus
ion, and that current protocols for treating otitis media with effusion usi
ng inflation need to be modified to optimize their intended effect.