Continuous measurements of intra-vascular pO2 in the pig optic nerve head.

BACKGROUND

The measurement of oxygen concentration in the microvasculature of a tissue is important for the understanding of oxygen delivery.

MATERIAL AND METHODS

A technique was developed to measure in a continuous manner the partial pressure of oxygen (pO2) in the optic nerve microvasculature of the minipig. This technique is based on the quenching by oxygen of the phosphorescence emitted by a dye that is injected intravenously. It provides measurements of the intra-vascular pO2 and was applied simultaneously with measurements of the extra-vascular pO2 with microelectrodes and blood flow by laser Doppler flowmetry.

RESULTS

We demonstrate for the first that the optic nerve head intra-vascular pO2 increases during dark adaptation. Furthermore no change in extra-vascular pO2 and blood flow 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.