Middle Ear Function Changes due to the Combined Effect of Pressure along with Fluid in Middle Ear Pressure Regulation- A Review

Abstract

The pressure changes in Middle Ear (ME) are due to the effect of both fluid and pressure, which can be detected by tympanometry. In this review article, the mathematical and formal model of regulation of ME pressure is discussed. The air pressure in the ME chamber and the surrounding environment are the same. The auditory tube is a common connection between the ME chamber and the nasopharynx. The main functional role of the auditory tube is the ventilation of ME. When a person breathes air through an auditory tube, it enters into the ME and ventilates it. The ossicles in the ME collect sound from the tympanic membrane and transfer it to the inner ear, which requires proper ventilation of the ME. The auditory tube maintains ME pressure, the same as the external auditory canal and outside pressure. If an auditory tube is blocked, it leads to failure to ventilate ME, leading to changes in ME pressure. Swallowing and yawning allow the passive opening of the auditory tube and thus results in air flow out of the chamber. Easy and passive air exchange is allowed from the ME to the pharynx if, the pressure in the ME is higher than in the surrounding environment. ME pressure is highly variable and can change in many conditions. ME pressures increase when the body rotates from a vertical to a horizontal position because it increases the effusion of the ME mucosa due to an increase in hydrostatic pressure, which leads to an increase in the perfusion rate. Therefore, pressure increases in the case of sleeping and drowsiness. Regulation of ME pressure is a physiological process in which pressure between ME and the surrounding environment is maintained at equilibrium. The mechanism of pressure regulation is possible because of the complex sensory neural reflex pathway. A laser doppler vibrometer measures displacement of the tympanic membrane in response to sound and ME compliance is calculated by tympanometry. The movement of the tympanic membrane reduces due to the combined effect of fluid and pressure on the ME. The ME functions are altered due to the negative pressure of the fluid rather than the positive pressure.