Pressure-dependent variation in volume of mucosal lining of the middle ear.

A method is described for studying pressure-dependent variation in the volume of the mucosa of the middle ear. Studies were performed at different pressures in the middle ear as well as at different ambient pressures. It was found that the pressure-dependent volumetric changes of the mucosa were the same whether the pressure in the middle ear was changed directly by altering the intratympanic or indirectly by altering the ambient pressure. With the method described it is also possible to determine the middle ear volume without artefacts due to the middle ear mucosa. The volume-pressure relationship of the middle ear mucosa varied from 0.6 to 1.7 mul/cm H2O and linearly with the volume of the middle ear. Comparisons between determinations of the middle ear volume with and without consideration of the mucosal compliance showed differences, especially in small middle ears. The effect on the volume of the mucosa caused by variation of posture was also studied. The physiological middle ear pressure depends on the functional state of the Eustachian tube, the middle ear volume, the tympanic membrane and the middle ear mucosa. Thus, knowledge of the mucosa compliance is important for calculating middle ear pressure as well as for determining the volume of the air-filled middle ear space. The method might also prove a useful tool in the elucidation of the vascular bed both in health and in disease as well as the reaction of the mucosal vessels to drugs.