IMAGING OF OXYGEN-SATURATION AND DISTRIBUTION OF ERYTHROCYTES IN MICROVESSELS

Objective: To construct images of oxygen saturation and tile distribut ion of erythrocytes in a network of microvessels. Methods: The image o f a small group of microvessels under an inverted micro scope was inco rporated into an image processor through a video camera and was digiti zed. Based on tile information obtained through six visible interferen ce filters of different wavelengths, oxygen saturation and the amount of erythrocytes in microvessels were calculated with a computer. The s ystem was as applied to a microvascular bed of isolated rabbit mesente ry perfused with a suspension of human erythrocytes. Results: In a ste ady flow, with lowering of tissue oxygen tension by superfusion with n itrogen-bubbled isotonic saline containing 20 mmol/L sodium dithionite , tile decrease of oxygen saturation of erythrocytes from arterioles r o venules was imaged. Simultaneously, the distribution of erythocytes in the microvessels was imaged and tile marginal cell-free layer was p rofiled under high magnification. No significant alteration of the ery throcyte distribution on tile deoxygenation of erythrocytes was observ ed. The exposure of erythrocytes to acidic pH and the decrease of the flow velocity of erythrocytes increased the release of oxygen fi om th e erythrocytes in microvessels. Conclusions: The present method will b e useful for tile comprehensive analysis of oxygen transfer In tile mi crovascular network, on the basis of both changes of the oxygen satura tion and tile flow behavior of erythrocytes.