Effect of Blood Pressure on Cochlear Blood Flow

Observations by Laser Doppler Method, Hydrogen Clearance Method and Oxygen Tension Determined by a Polarographic Technique

Abstract

Cochlear circulation was measured in guinea pigs by three methods : laser Doppler, hydrogen clearance and oxygen tension (PO₂). The effect of blood pressure (BP) changes was examined with a doppler needle probe plased on the 2nd turn, and a hydrogen or oxygen-sensitive microelectrodes inserted into the endolymph of the same turn. The BP was elevated by an intravenous infusion of norepinephrine and lowered by bleeding. The cochlear blood flow (PO₂) correlated well with the BP. However, the percentage of change of cochlear blood flow (PO₂) at low BP was less than that at a high BP, indicating that cochlear vessels have an autoregulating ability at a low BP.