An In-Vitro Method for Simulation of Oxygen Transport in the Microcirculation
Mathematical modeling of oxygen transport in the microcirculation normally requires the introduction of a number of simplifying assumptions to reduce the very complicated physical situation to a form that is tractable (for a review see Fletcher, 1978). Unfortunately, there are great difficulties in designing and executing experiments that will serve to test these assumptions critically, Pittman and Duling (1975b, 1977) have made substantial progress in the measurement of oxygen uptake and release by red cells in hamster cheek pouch microvessels. However, in these and other in vivo experiments, the boundary conditions and exact geometries for the diffusion problem are difficult to ascertain. We have attempted to circumvent these problems by constructing an in vitro silicone rubber capillary system which simulates the real physiological situation and also allows precise measurement of flow and transport characteristics. capillary bed can be computed by established mathematical techniques. Heineken et al. (1978) developed the technique for fabricating silicone rubber capillaries. They also made substantial progress in demonstrating the applicability of these systems for studying gas transport by the use of oxygen electrodes. We have gone one step further and are measuring directly the fractional saturation of red cells or free hemoglobin by microspectrophoto-metry. The latter detection system represents an adaptation of previous work by Sinha (1969) with stationery red cells, and by Pittman and Duling (1975a, b, 1977) with red cells flowing through micro-vessels. In our apparatus the artificial capillary is placed on the stage of a microscope, and the transmitted light is diverted to a photomultiplier for absorbance measurements.
KeywordsOxygen Transport Absorbance Change Tungsten Wire Fractional Saturation Hemoglobin Solution
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