[Microlight-guided spectrophotometry of the cochlea].
BACKGROUND
Intraoperative measurements of local intracapillary hemoglobin oxygenation of the human cochlea via the round window membrane have been shown to be possible using the Erlangen microlight-guided spectrophotometer. The aim of the present study was to develop a new microlight guide suitable for measurements in the round window niche and to evaluate electrophysiologically the possible impact of the procedure on the cochlea.


METHODS
Measurements were made for wavelengths of 450 to 900 nm at a total power of 5.3 mW. The exit diameter of the light guide was 200 microns and the angle used was 20 degrees. The recording depth was about 250 microns. The atraumatic character of the spectrophotometry was demonstrated by monitoring the compound action potential (CAP) threshold tuning curve from 1 to 34 kHz in ketanest-anesthetized guinea pigs.


RESULTS
CAP thresholds remained constant (0.3 +/- 3.9 dB SPL) during 3 to 30 min of exposure to the light.


CONCLUSIONS
These results suggest that the spectrophotometry may be useful as a new technique for intraoperative monitoring of intracapillary hemoglobin without causing physiological deterioration of the cochlea.
Leuwer
R
R
HNO-Klinik, Universitäts-Krankenhaus Hamburg-Eppendorf.
Maier
H
H
Gummer
A W
AW
D000818:Animals; D001300:Audiometry, Evoked Response / Q000295:instrumentation; D001309:Auditory Threshold / Q000502:physiology; D002196:Capillaries; D003051:Cochlea / Q000098:blood supply*; D003055:Cochlear Microphonic Potentials; D004867:Equipment Design; D006168:Guinea Pigs; D006452:Hemoglobinometry / Q000295:instrumentation*; D006801:Humans; D008866:Microsurgery / Q000295:instrumentation*; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D010100:Oxygen / Q000097:blood*; D012405:Round Window, Ear / Q000098:blood supply; D013053:Spectrophotometry / Q000295:instrumentation*
D010100:Oxygen