Development of a Middle Ear Gas Exchange Model to Predict the Effects of Pressure Variations on the Tympanic Membrane during Flights

The middle ear pressure variation is one of the most important factors that causes discomfort on flight passengers and crew. The purpose of this work is to develop a mathematical model of the middle ear cavity pressure variation during typical flight’s conditions. The middle ear cavity was modeled as a gas chamber that transfer gas to other physiological systems trough three different ways. One of them is through the Eustachian tube, that conects the tympanic cavity to the nasopharynx. The tympanic cavity also transfes gas through diffusion to the blood stream in the tympanic cavity and in the mastoid cavities system. A system of four non-linear ordinary differential equations was obtained which was resolved using the forth order Runge-Kutta numerical method. Parametric analysis of the active airflow resistance of the Eustachian tube, tympanic membrane compliance and mastoid cavities volume were conducted because it was found in the literature that these parameters varies among population. Simulation’s results, for a typical cabin pressure variation curve, showed that people with higher airflow resistances of the Eustachian tube may experiment higher gradients of pressure in their tympanic membranes. They also showed that the model is not much sensitive to the tympanic membrane compliance parameter and that higher mastoid volumes increases gas diffusion between the middle ear and blood stream.