K. Nagahara

Pertlymph Oxygenation in Sudden and Progressive Sénsorineural Hearing Loss

The perilymphatic oxygen tension of the vestibular perilymph of 34 patients with different inner ear losses were measured with the polarographic method before and after inhalation with carbogen. Two patterns of disturbed perilymphatic oxygenation were observed: 1) Characterized by low initial values of perilymphatic oxygenation and normal response to carbogen inhalation was present in sudden deafness and sudden cochleovestibular loss of inner ear function. 2) Characterized by normal initial values of perilymphatic oxygenation and a low response to carbogen, was found in presence of a slowly progressive sensorineural hearing loss. The significance of the obtained results in regard to the possible vascular pathology of the inner ear is discussed.

Effects of Prostaglandins on Perilymphatic Oxygenation: Enhancement of Cochlear Autoregulation by Prostacyclin

Effects of prostaglandin E1, prostacyclin, a prostacyclin analogue (OP-2507), and an inhibitor of thromboxane A2 synthetase (OKY-046) on the perilymphatic oxygen tension were measured in the feline tympanic perilymph under various respiratory conditions and blood pressure ranges. Factors influencing the capacity of the autoregulative properties of the inner ear vessels to accommodate changes in systemic blood pressure were also examined. Intravenous administration of prostacyclin, OP-2507, and OKY-046 prevented a decrease in perilymphatic oxygen tension when the systemic blood pressure decreased. Even a negative correlation of the differential coefficients between the perilymphatic oxygen tension and the systemic blood pressure was noticed during the administration of prostacyclin. Thus, prostacyclin enhanced the autoregulative property of the inner ear vessels. Furthermore, correlation studies between perilymphatic oxygen tension and cochlear blood flow demonstrated a partial dissociation, indicating the presence of autoregulation in the mean systemic blood pressure range under 80 mmHg.

Tissue Oxygen Tension in the Stria Vascularis

Tissue oxygen tension in the stria vascularis was successfully measured in cats using the polarographic technique. A correlation study using the differential coefficient between oxygen tension in the stria vascularis and systemic blood pressure proved that vascular autoregulation is present in the mean systemic blood pressure range between 40 and 80 mmHg. The anatomical findings and the response patterns to different gas inhalations indicated that the type of vascular regulation present is more closely related to chemical control than to auto-regulation.