Effect of Underwater Insertion on Intracochlear Pressure

Area of Science:

• Otolaryngology
• Biomedical Engineering
• Neurosurgery

Background:

• Intracochlear pressure during cochlear electrode insertion is critical for preserving residual hearing.
• Fluid dynamics at the round window significantly impact intracochlear pressure.
• Understanding insertion conditions is key to mitigating hearing loss.

Purpose of the Study:

• To compare different cochlear implant electrode insertion techniques.
• To evaluate the impact of the round window fluid situation on intracochlear pressure.
• To identify insertion methods that minimize intracochlear pressure.

Main Methods:

• Cochlear implant electrode insertion simulated in a curled artificial cochlear model.
• Pressure sensor placed at the cochlear tip to measure intracochlear pressure.
• Four fluid conditions at the round window were tested: hyaluronic acid, dry middle ear with a moisturized electrode, underwater insertion, and wet middle ear with indirect insertion.

Main Results:

• Intracochlear pressure during insertion is directly related to the fluid condition at the round window.
• Lowest pressure amplitude (0.13 mmHg ± 0.07) observed with indirect insertion in a wet middle ear.
• Highest pressure amplitude (0.64 mmHg ± 0.31) observed with hyaluronic acid at the round window.

Conclusions:

• The fluid state at the round window significantly influences intracochlear pressure during electrode insertion.
• Indirect insertion of a moisturized electrode into a wet middle ear yielded the lowest intracochlear pressure values.
• Hyaluronic acid at the round window resulted in high intracochlear pressure in this artificial model.