MICROLIGHT-GUIDED SPECTROPHOTOMETRY OF TH E HUMAN COCHLEA

Background: Intraoperative measurements of local intracapillary hemogl obin oxygenation of the human cochlea via the round window membrane ha ve been shown to be possible using the Erlangen microlight-guided spec trophotometer. The aim of the present study was to develop a new micro light 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 g uide was 200 mu m and the angle used was 20 degrees. The recording dep th was about 250 mu m. The atraumatic character of the spectrophotomet ry was demonstrated by monitoring the compound action potential (CAP) threshold tuning curve from 1 to 34 kHz in ketanest-anesthetized guine a pigs. Results: CAP thresholds remained constant (0.3+/-3.9 dB SPL) d uring 3 to 30 min of exposure to the light. Conclusions: These results suggest that the spectrophotometry may be useful as a new technique f or intraoperative monitoring of intracapillary hemoglobin without caus ing physiological deterioration of the cochlea.