The Eustachian tubes, leading from the middle ears to the nasopharynx, are normally closed and only open with movements such as swallowing and yawning. If there is some obstruction and normal opening movements do not then open the tubes, a vacuum is produced in the middle-ear cavities and this results in impaired hearing.
There are numerous common causes of obstruction in the Eustachian tubes. Among them are hypertrophied adenoid tissue, upper respiratory infections, respiratory allergy, tumors, et cetera. If these obstructions are eliminated and not allowed to continued for a long period of time, normal physiology is restored and no permanent pathology will result.
However, there are many cases in which the cause of blockage cannot be found or where it cannot be completely eliminated. If such conditions are not properly treated, a chronic obstruction, or partial obstruction, will produce irreversible middle-ear changes with resulting impairment of hearing.
RAWLINS AG. The Value of Self-Inflation of the Middle Ear. AMA Arch Otolaryngol. 1959;69(5):547–548. doi:10.1001/archotol.1959.00730030559004
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