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SEROUS OTITIS MEDIA:
INTRODUCTION 3
| Description | : | Measurements of the gas concentrations within the middle ear indicate that the relative oxygen concentration is less than that of the surrounding environment.
This finding suggests that oxygen is absorbed by the mucosa. By contrast, the relative concentration of C02 in the middle ear is higher than that of the surrounding atmosphere, suggesting that C02 may be actively produced by the mucosa. The fundamental cause of SOM is a blockage of the Eustachian tube which prevents the normal replacement of the air within the middle ear cleft that is continuously being absorbed by the mucosal lining. Consequently, as the air within the middle ear is gradually absorbed, a negative pressure or partial vacuum develops between the middle ear and the mucosal lining. Over time, this negative pressure gradually draws a serous type of transudate from the capillaries of the mucosa into the middle ear cleft (the theory of "hydrops ex vacuo"). The most common cause of Eustachian tube obstruction is a viral upper respiratory infection. The most serious cause of Eustachian tube obstruction is a carcinoma of the nasopharynx, which must be suspected in all nonresolving cases of SOM. |
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