[The measurement of cochlear flow by laser Doppler in man: the preliminary results]

Laser-Doppler flowmetry is presently one of the methods of choice in measuring cochlear blood flow. The techniques is non-invasive and is based on the frequency shift of the laser beam induced by the red blood cell movement. Previous studies of cochlear blood flow carried out on animals and humans demonstrated the reliability of laser-Doppler flowmetry and its usefulness in understanding inner ear microcirculation physiology. In this paper we present preliminary data obtained from three patients examined under general anesthesia while undergoing tympanoplasty. Results showed that tracings, whose baseline is proportional with the blood flow, are characterized by waves correlated to pulse beat and automatic ventilation. Moreover, intrinsic contractions of inner ear vessels (waves of vasomotion) as exist in cerebral microcirculation, were observed. Pharmacological hypotension hypocapnia and the application of epinephryne determine a significant reduction of cochlear blood flow. These results suggest that while cochlear blood flow is related to systemic pressure, it has an intrinsic control system. As well since we did not obtain any modification in bone conduction threshold after surgery, we conclude that laser-Doppler flowmetry is a safe technique.