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[Measurement of tissue (correction of tissne) tension and ventilation resistance in eustachian (correction of eustachiam) tube opened by positive pressure in respiratory tract and the study on mechanism of ventilation].

OBJECTIVE
To determine the ventilation resistance of the Eustachian tube (VRET) and the lowest positive pressure to maintain the opening of the tube. Through which to elucidate the mechanism of positive ventilation.


METHOD
To determine the tissue tension, 24 male flyers. Middle ear pressure was measured by a Zodiac 901 analyzer. To determine the VRET: when the Eustachian tube was opened, the change of pressure in the nasopharynx during the change of pressure in the external auditory canal was the VRET. In order to understand the relationship between middle ear barotraumas and VRET, 160 ears were tested in flight, and 60 ears were tested in the hypobaric chamber.


RESULT
The Eustachian tube ventilation resistance was found to have a large respective divergence (1.20-6.86 kPa). When the tube was opened, the pressure of the middle ear changed with the change of the mask pressure. When the mask pressure dropped to 0.70 kPa, the middle ear pressure dropped down to 0 kPa. The individual difference was comparatively small. Among 160 ears of 80 combat aircraft flyers in flight, 19 ears had presentations of middle ear barotalgia. 141 ears had no presentation of barotalgia. The VRET's were significantly different (P<0.001). Among the 60 ears of 30 flyers tested in the low-pressure chamber, 9 ears had presentations of middle ear barotraumas. 51 ears had no presentation of barotalgia. The difference between the VRET's were also significant (P<0.001).


CONCLUSION
If there is enough positive pressure in the mask, it will open the Eustachian tube. Then, it needs only a small positive pressure (about 0.70 kPa) to maintain the tube open. The airflow in the tube follows the law of pneumatics. The occurrence of barotalgia and VRET are correlative.