Symposium on prophylaxis and treatment of middle ear effusions.: Ii. Eustachian tube function and middle ear pressures as they influence susceptibility to disease

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Abstract
The bursting pressure necessary to rupture the tympanic membrane of cats and guinea pigs was determined by increasing and decreasing the intrabullar pressures and by increasing and decreasing the pressures in the external auditory canal after the bulla was vented to the outside. The average pressures in all experiments varied from 100 to 180 mm. Hg. Such pressures are far greater than the fall in intrabullar pressure which occurs following ligation of the eustachian tube in cats. It is suggested that drumhead perforations in humans with serous otitis may be due to smaller diminished tympanic pressures over a long period of time, leading to retraction pocket, entrapment of debris, and development of an expanding epithelial‐lined cyst.