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KMID : 0378019770200080049
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New Medical Journal
1977 Volume.20 No. 8 p.49 ~ p.63
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A Study on the Effect of Air Volume and Pneumatization of Temporal Bone upon the Middle Ear Impedance
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Abstract
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The impedance. audiometry has recently been essential to clinical audiology.
The vibratory energy introduced into the external ear canal has known to be modified by many factors such as the mechanical property of eardrum, the motility of ossicles, the resistance of inner ear system and the air volume of tympanomastoid cavity.
This study- was designed to observe the role of air volume in determining the middle ear impedance.
To find it out, the change in middle ear impedance was studied in 12 dogs whose both temporal bones were connected with various sized hard-walled cavities. The middle ear impedance and the pneumatization of temporal bone were also examined in 333 human adults (509 ears) who proved not to have any previous and present illness of middle ear conduction system. Then the correlation between the pneumatization and the middle ear impedance was investigated.
The results were as follows;
1. In the dog´s middle ear, tympanometric curve of type A was only found, and its configuration was not changed by the air volume.
2. In the dog´s middle ear, the static compliance revealed a linear increase in proportion to the air volume; the increasing rate was 0.05±0.02cc/cc of air volume.
3. In the human middle ear, the static compliance showed a tendency to increase in proportion to the pneumatization of temporal bone.
4. In the human middle ear, there was a significant regression equation between the pneumatization of temporal bone (X variable) and the static compliance of middle ear(Y variable); Y=0.22X+0.14±0.07 in the normal cases, Y=0.18X+0.13±0.04 in the pure sensorineural hearing loss cases, and Y=0. 19X+0. 16±0.05 in the total cases.
5. The above results suggest that the static compliance of middle ear have another clinical value as a diagnostic means examining the pneumatization of temporal bone.
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