[An experimental study of middle ear implantable hearing device].

The partially middle ear implantable hearing device was designed and tested in 7 cats with conductive hearing loss and 5 cats with mixed hearing loss. It was composed of sound processor, connector and ossicular vibrator. The ossicular vibrator was made from piezoelectric ceramic bimorph which was constructed in the form of flat chip 6mm in length, 1mm in width and 0.5mm in thickness. The incus of cat was removed and the lip attachment of the vibrator was attached to the head of the stapes. The base of the vibrator was fixed to the bone wall of bulla with medical glue. The average values of the response threshold of ABR evoked by click via this vibrator got reduction of 37dB and 39dB respectively in conductive hearing loss group and mixed hearing loss group. The gain curve of hearing was flat in the range from 0.5 to 8kHz frequencies. The ABRs evoked by click via ossicular vibrator was similar to that recorded preoperatively in the wave shape. This result indicates that this device is a highly efficient sound conducting divice to inner ear.