Observations of middle ear pressures. Commentary with movie.
Previous direct measurements of middle ear pressure in ears with serous otitis resulted in the range of from 0 to -10 mm H2O pressure. To confirm these findings we attempted to quantify middle ear pressures by doing myringotomies in serous otitis patients through sterile saline solution. We compared the rate of aspiration of the saline in ears with serous otitis to the rate of aspiration of saline after an experimental myringotomy in an ear model in which known pressures were imposed. To record our findings we used motion picture photography. Layering a film of sterile oil suspension of oxytetracycline and hydrocortisone over dry tympanic membrane perforations resulted in the demonstration of a pulsatile positive pressure of about 6 mm water in many of the ears which we tested. The oil film often formed an external bubble which ruptured after several minutes. In some ears there was no change in pressure and in only a small percentage there was evidence of a decreased pressure by absorption of air in the middle ear during the period of observation. This positive pressure is unrelated to swallowing and suggests that the current theories of middle ear aeration via opening of the eustachian tube may not be valid. These findings were demonstrated with motion picture film.
D000158:Acoustic Impedance Tests; D004432:Ear, Middle / Q000502:physiology / Q000503:physiopathology*; D006801:Humans; D008954:Models, Biological; D010033:Otitis Media / Q000503:physiopathology* / Q000601:surgery; D011312:Pressure; D014432:Tympanic Membrane / Q000601:surgery