Biomedical subjects

H Izukura

Publications and source records attributed to H Izukura.

7 recordsLinked to original sources

PubMed1994

Effect of atmospheric pressure on hearing in normal subjects.

Hearing is assumed to be altered during or immediately after a change in atmospheric pressure, although this has not been tested experimentally. We used a soundproof pressure chamber to examine the effect of alterations in atmospheric pressure on hearing in 26 normal healthy subjects. The subjects were placed in the soundproof pressure chamber in a supine position and instructed to actively equilibrate middle ear pressure or to abstain from doing so. When the pressure was changed to +/- 500 mmH2O at 33 mmH2O/s the results were as follows: When subjects did not equilibrate middle ear pressure, air conduction at low frequency tones increased more than bone conduction. The degree of deterioration in hearing was greater when the chamber pressure was increased (descent) than where pressure was decreased (ascent). When the subjects equilibrated middle ear pressure, little change in the levels of air or bone conduction was observed. Most of the deterioration in bone conduction was considered to reflect functional loss due to increased stiffness and damping of the sound transmission mechanism.

Adult↗

PubMed1994

Mechanism of hearing disturbance due to alteration in atmospheric pressure.

We used a soundproof pressure chamber to examine how the changes in atmospheric pressure as experienced in daily life reduces bone conduction in a total of 48 normal adults. The subjects were given special ear plugs that connected external auditory canal to the pressure gauge and a small pump located outside the chamber, and were instructed not to swallow, to avoid active opening of the Eustachian tube. The chamber pressure was increased (or decreased) to +/- 500 mmH2O at a rate of 33 mmH2O/s. Then pressure in the external auditory canal was increased (or decreased) gradually after the chamber pressure had reached +/- 500 mmH2O, to equilibrate the pressure across the ear drum. Bone conduction did not recover the level before increase (or decrease) in the chamber pressure. We conclude that at least a minor part of the deterioration in bone conduction after changes in the chamber pressure was caused by displacement of the round window membrane.

Adult↗

PubMed1994

Test for pressure control capacity of the Eustachian tube.

Because of Eustachian tube controls middle ear pressure to maintain the best hearing level, we tested the equilibration capacity of the Eustachian tube by measuring hearing levels in a soundproof pressure chamber. The number of swallows to recover normal hearing after the chamber pressure reached -200 mm H2O (an index of equilibration capacity for the static pressure differences across the eardrum) was less than 9 in normal subjects. The worst level of hearing and the time required to recover normal hearing from the beginning of alteration in the chamber pressure to -700 mm H2O (indexes of equilibration capacity for dynamic pressure differences across the eardrum) were 0-17 dB and within 120s in normal subjects. It was difficult to determine definitive normal ranges of the equilibrium capacity of the Eustachian tube when positive pressure was applied.

Adult↗

PubMed1994

A ventilation capacity test for the Eustachian tube using a soundproof pressure chamber.

Using a soundproof pressure chamber, we performed Békésy air conduction audiometry at 1000 Hz under the following pressure conditions: 1) from atmospheric pressure (AP) to 200 mmH2O below AP, 2) AP to 200 mmH2O above AP, 3) AP to 700 mmH2O below AP, and 4) AP to 700 mmH2O above AP. In conditions 1) and 2), the patient was instructed not to swallow until the pressure change was complete, then to swallow once every 15 seconds. The number of swallows required for hearing to return to the baseline level was counted. In conditions 3) and 4), the patient was told to swallow as many times as possible both before and after completion of the pressure change; maximum hearing level and the time needed for return to the baseline level were measured. Although all except one of the seven patients with suspected tubal dysfunction showed normal results with catheter insufflation and tympanometry, six of the seven showed abnormality and one reported the disappearance of ear stuffiness after the ventilation capacity test. We concluded that this test is useful not only for the diagnosis of tubal dysfunction but also as a possible therapy for aiding adaptation to changing environmental pressure.

Acoustic Impedance Tests↗

PubMed1994

Pressure test in normal subjects.

The application of pressure to the middle ear changes the normal inner ear pressure in animal experiments. In this study we tested the effect of exposure to under- or overpressure on hearing in a total of 78 normal ears (40 subjects) in a soundproof pressure chamber. [After exposure to underpressure, a 10 dB or more gain in 3 ears and loss in 2 ears for at least one of the test frequencies was observed in 38 ears. After exposure to overpressure, a 10 dB or more gain in 5 ears and loss in 1 ear for at least one of the test frequencies was observed in 40 ears.] The characteristics of transferred inner ear pressure during a series of exposures to underpressure seemed to be similar to those during exposures to overpressure.

Acoustic Impedance Tests↗

PubMed1994

Pressure test for the diagnosis of Menière's disease.

In the last 15 years, a pressure chamber able to generate negative air pressure has been used to treat patients with Menière's disease. In this study we sought to clarify whether the underpressure chamber can be used to diagnose Menière's disease. We studied 45 ears from patients with neurotological diseases. The subjects were placed supine in a soundproof pressure chamber. The pressure was first decreased to -500 mmH2O, and after 5 min to -700 mmH2O. The pressure was kept at this level for another 5 min and then increased to 0 mmH2O. This procedure was done three times in succession. While the chamber pressure was below 0 mmH2O, the subjects were instructed to abstain from actively equilibrating middle ear pressure. When the chamber pressure was raised to 0 mmH2O, they were instructed to equilibrate middle ear pressure, and if necessary Politzerization or catheterization of the Eustachian tube was done. As a result, hearing was improved after this procedure only in patients with Menière's disease (50%) and/or cochlear Menière's disease (32%) in which endolymphatic hydrops was suspected.

Acoustic Impedance Tests↗

PubMed1994

Effect of atmospheric pressure on hearing in patients with Menière's disease.

Hearing in patients with Menière's disease improved when they were treated in an underpressure chamber. In this study 46 patients with neurotological diseases, including 32 cases of Menière's disease, were tested in an overpressure chamber. As a result, hearing in 32% of the patients with Menière's disease improved, although this was lower than the 50% rate of improvement in Menière's disease patients tested in an underpressure chamber.

Atmosphere Exposure Chambers↗