MYRINGOSCLEROSIS CAUSED BY INCREASED OXYGEN CONCENTRATION IN TRAUMATIZED TYMPANIC MEMBRANES - EXPERIMENTAL-STUDY

The purpose of this study was to elucidate possible relationships betw een the oxygen concentration of the middle ear cavity and the developm ent of myringosclerosis. Three groups of rats with myringotomized tymp anic membranes were exposed to different oxygen concentrations of 10%, 15%, and 40%, respectively, for 1 week. A fourth group was kept in am bient air. Two other groups of rats with myringotomized and intubated tympanic membranes were exposed to oxygen concentrations of 10% and 40 %,respectively, for the same period of time. Otomicroscopically, all h yperoxic animals had more numerous myringosclerotic lesions compared w ith the ambient air group, and also displayed a pronounced hyperplasia of the keratinizing epithelium around the perforation border. By cont rast, the hypoxic animals showed less pronounced myringosclerotic lesi ons or even completely lacked them. It is inferred that an increased o xygen concentration in the middle ear cavity will increase the likelih ood of myringosclerotic deposits. The mechanism involved could be rela ted to the formation of oxygen radicals.