Development of a method for simultaneous measurement of blood flow and blood gases

点击翻译按钮获取中文摘要

A novel method to measure blood flow and blood gases simultaneously in vivo was developed. This method is based on in vivo fluorometry of chemical substances sensitive to physiological parameters such as blood gases, blood temperature, pH and so on. The fluorescent dye was encapsulated in liposomes so as to administer into blood circulation. The liposome was also used to measure blood flow velocity using transit time method.Multilamellar liposome was fabricated from phosphatydylcholine using reverse-phase evaporation methods. Addition of cholesterol enabled to sustain fluorescent chemicals well, and activated methoxypolyethylene glycol reduced uptake of liposome by reticulo-endothelial system. The size of liposome was standardized using polycarbonate membrane filter. When liposome with less than 8mum of diameter were used, the flow velocity observed in mesenteric vessel showed no difference with that observed with erythrocytes. The administration of this liposome caused no embolism and toxicity for at least a week.The optical system finally attained after several trials is as follows : argon-laser was used modulating with Acousto-Optic modulator, exciting and signal laser was transferred with plastic optical fibers, and the fluorescence intensity was determined using photon counting. Since the relaxation time of the fluorescence is related to the oxygen concentration by Stern-Volmer equation, exygen tension of liposome suspension was determined from the lifetime of the signal light. Using this system we measured successfully the partial pressure of oxygen in vitro experiment and also in vivo experiment using anesthetized rat.The application of this system for the continuous monitoring of physiological parameters including CO_2 tension, and local temperature are underway.