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A rat model of otitis media with effusion (OME) was developed by intratympanic injection of E. coli endotoxin and section of the third branch of the trigeminal nerve (V3). The period of fluid retention induced by the endotoxin was prolonged for 5 days or longer, in cases when tubal function was impaired by cutting of V3. Three Eustachian tube function tests (patency test of inflation-deflation tests, forced response test and negative pressure test) were carried out before and after the endotoxin inoculation and V3 sectioning. At 4 days after these procedures, passive opening pressure (Po), closing pressure (Pc) and tubal resistance (R2) were significantly lowered. The negative pressure test showed impaired capacity of active opening. This model of Eustachian tube dysfunction is considered to reveal functional obstruction, a condition similar to that of clinical cases of OME. The study shows that both inflammation in the middle ear and tubal dysfunction, such as functional obstruction, are factors in the development and prolongation of OME.

Prognostic value of the Eustachian tube function test remains controversial. To prevent ear drum adhesion or the recurrence of cholesteatoma it is important to select cases with severe organic obstruction of the Eustachian tube and to use surgical procedures to restore function. We summarize here the indications and the surgical procedure for organic obstruction of the Eustachian tube, especially in the region of the tympanic orifice. Adequate preoperative evaluation of Eustachian tube function and pertinent surgical procedures will pave the way for a better prognosis for patients subjected to ear surgery.

We have summarized various methods for testing Eustachian tube function since the 1980's. There have been numerous contributions to our knowledge on Eustachian tube and middle ear functions, and the pathophysiology of disorders of the middle ear has been clarified. Understanding of the Eustachian tube function and controlling the Eustachian tube dysfunction are mandatory for adequate clinical management and for improvement of the prognosis.

Sonotubometry and pressure equilibration test are representative test methods to evaluate the active opening capacity of the Eustachian tube. We applied these tests to 72 ears with otitis media with effusion and 21 ears with chronic otitis media. In 73 ears, both tests showed identical results (11 ears with good active function and 62 ears with poor function). Twenty ears showed good active opening by sonotubometry despite inability to relieve applied negative pressure by swallowing. This inconsistency is believed to result from a too short duration of the tubal opening, by which sound is transmitted through the Eustachian tube, without pressure change in the middle ear cavity. We propose that sonotubometry is a suitable method of detecting impairment of the tubal active opening function, but that a good result by sonotubometry does not always indicate a satisfactory pressure equilibration capacity of the Eustachian tube.

Eustachian tube (ET) function was studied in 162 ears with otitis media with effusion (OME) and chronic otitis media (COM), using tubo-tympanoaerodynamic graphy, patency and pressure equilibration test in the inflation-deflation test. Severe impairment of active opening function was found in both OME children and adults compared with that of COM patients. This impairment in active opening was thought to result from functional obstruction of the ET in 71.8% of OME children and 51.8% of OME adults. However, 45.6% of OME adults had an organic obstruction while such was present only in 28.2% of OME children. We deduce from this study that impaired active opening function of the ET in both OME children and adults is the result of functional obstruction rather than organic obstruction, but organic obstruction is considered to be related to the pathogenesis of OME in adults.

We studied Eustachian tube function of healthy adults by two air flow methods, namely tubo-tympano-aerodynamic graphy by Valsalva maneuvre, and Tyonbee maneuvre during swallowing. We observed for the first time the presence of reciprocal features in normal Eustachian tubes. We also compared the tubal function of the same group using an air flow method and sound transmission method. The results of these observations showed that 77.4% of the subjects were positive for TTAG in Valsalva pattern, and 85.4% for sonometry. It can be inferred that data on the tubal opening in response to Valsalva and Toynbee maneuvres is obtained more easily by sonometry than by TTAG. TTAG, which permits examination of minute changes in air flow dynamics even in healthy Eustachian tubes, provides more important information on tubal function than does sonotubometry.