Does loud sound influence the intracochlear oxygen tension?
The effect of loud sound on the perilymphatic oxygen tension was studied in anesthetized guinea pigs. Pure tone (4 kHz) and broad-band noise were given at 85-130 dB SPL for 3-8 min. No effects were seen either in the animals exposed to pure tone or in the animals exposed to 85 dB broad-band noise. In the animals exposed to noise at 130 dB SPL both increases and decreases of perilymphatic oxygen were measured but the changes were only of about 12% or less. The response to anoxia was normal. In animals with hypotension ( less than 8 kPa) the perilymphatic PO2 fluctuated with the blood pressure. When the sound was delivered directly into the opened bulla the measured PO2 dropped immediately but was found to be caused by the cooling effect of an air current produced by the noise. Flushing the opened bulla with nitrogen, air or oxygen caused the same temperature-induced drop of measured PO2. The results and the artifacts are discussed.
