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HIGHLIGHTED TOPICS
Oxygen Sensing in Health and Disease

Red blood cell velocity and oxygen tension measurement in cerebral microvessels by double-wavelength photoexcitation

¹Department of Physiology, Kawasaki Medical School, Kurashiki, 701-0192; ²Department of Clinical Research, National Saitama Hospital; Wako, 351-0102; ³Oshio Clinic, Chiyoda-ku, 101-0063; and ⁴Department of Applied Physics and Physico-Informatics, Faculty of Science and Technology, Keio University, Yokohama, 223-8522 Japan

Submitted 23 July 2003 ; accepted in final form 2 December 2003

Because the regulation of microcirculation in the cerebral cortex cannot be analyzed without measuring the blood flow dynamics and oxygen concentration in cerebral microvessels, we developed a fluorescence and phosphorescence system for estimating red blood cell velocity and oxygen tension in cerebral microcirculation noninvasively and continuously with high spatial resolution. Using red blood cells labeled with fluorescent isothiocyanate to visualize red cell distribution and using the oxygen quenching of Pd-meso-tetra-(4-carboxyphenyl)-porphyrin phosphorescence to measure oxygen tension enabled simultaneous measurement of blood velocity and oxygen tension. We examined how the measurement accuracy was affected by the spatial resolution and by the excitation laser light passing through the targeted microvessel and exciting the oxygen probe dye in the tissue beneath it. Focusing the excitation light into the microvessel stabilized the phosphorescence lifetime at each spatial resolution; moreover, it greatly reduced phosphorescence from the brain tissue. Animal experiments involving acute hemorrhagic shock demonstrated the feasibility of our system by showing that the changes in venular velocity and oxygen tension are synchronized to the change in mean arterial pressure. Our system measures the red cell velocity and oxygen concentration in the cerebral microcirculation by using the differences in luminescence and wavelength between fluorescence and phosphorescence, making it possible to easily acquire information about cerebral microcirculatory distribution and oxygen tension simultaneously.

cerebral microcirculation; erythrocyte velocity; oxygen tension; fluorescence; phosphorescence

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