Endolymphatic Oxygen Tension in the Cochlea of the Guinea Pig

Abstract

Oxygen tension of the endolymph in the scala media of the guinea pig cochlea was measured using a micropolarographic technique. Near the stria vascularis, the oxygen tension was 55–75 mm Hg. Deeper in the scala media it decreased gradually to 16–25 mm Hg. Following sound the oxygen tension fell below normal with very gradual recovery. Breathing pure nitrogen reduced the oxygen tension rapidly. On rebreathing air it usually returned to normal as rapidly overshooting for one or two minutes. If recovery from anoxia was slow no overshoot occurred. Breathing 10% carbon dioxide in air increased the oxygen tension more than pure oxygen. On return to normal air the oxygen tension fell back to normal or slightly below if the animal had previously breathed pure oxygen.