Intracochlear oxygen tension during and after loud sound exposure

Inner ear oxygen tension can be a measure of metabolic capacity in the inner ear, in that the energy production of the sensory epithelium could draw upon the available oxygen in the cochlear fluids. During periods of loud sound the metabolic needs of the inner ear presumably increase in order to meet the demands of greater transduced energy. Increased magnitudes of cochlear potentials reflect this higher demand. Additionally, loud sound is also known to have an effect (directly or indirectly) on the state of capillary networks within the inner ear. In the present experiments on guinea pigs, oxygen sensitive microelectrodes were placed into various fluid compartments of the inner ear to measure oxygen changes during the application of intense loud sound. In other experiments, similar electrodes, calibrated for absolute oxygen tension, were placed into the perilymph and endolymph of the first cochlear turn 2 to 7 h after a 4 h period of 120 dBC broad‐band noise exposure. Oxygen levels did not change significantly or consistently during acute loud sound exposure. The chronic loud sound exposure. on the other hand, resulted in significantly elevated levels of perilymphatic and endolymphatic oxygen tension. These results will be discussed and related to present and past histological findings. [This work was supported by Public Health Service Grants NS 05785 and NS 11731.]