CONTINUOUS MEASUREMENTS OF INTRA-VASCULAR PO(2) IN THE PIG OPTIC-NERVE HEAD

Background The measurement of oxygen concentration in the microvascula ture of a tissue is important for the understanding of oxygen delivery . Material and Methods A technique was developed to measure in a conti nuous manner the partial pressure of oxygen (pO(2)) in the optic nerve microvasculature of the minipig. This technique is based an the quenc hing by oxygen of the phosphorescence emitted by a dye that is injecte d intravenously. It provides measurements of the intra-vascular pO(2) and was applied simultaneously with measurements of the extra-vascular pO(2) with microelectrodes and blood flow by laser Doppler flowmetry. Results We demonstrate for the first that the optic nerve head intra- vascular pO(2) increases during dark adaptation. Furthermore no change in extra-vascular pO(2) and blood now could be detected. Conclusions Based on Krogh's model, these results suggest that oxygen consumption by the optic nerve head tissue increases during dark adaptation.