Liver Tissue Blood Flow Measurement Using the Microbubble Method

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At first organ blood flow measurements were conducted in a rabbit model using the colored-microsphere method to establish the liver tissue blood flow measurement by the micobubble method. Although mechanical ventilation reduces the respiratory muscle workload, the effects of ventilatory settings on blood flows of respiratory muscle and major organs have been little studied. Using the different-colored microspheres method, we measured the regional blood flow of respiratory muscle and major organs at different mechanical ventilatory settings in a rabbit model. Ten New Zealand white rabbits were anesthetized by continuous infusion of ketamine and propofol and then tracheostomized. A 19G catheter was inserted into the left ventricle via the left carotid artery to inject colored microspheres. The right femoral artery was cannulated for blood sampling. The regional blood flows in diaphragm (Diaphcost, crur), kidney and liver were studied during pressure support ventilation (PSV) of 0, 6, 12 cmH_2O and then pressure controlled ventilation (PCV) of 6 and 12 cmH_2O after the administration of muscle relaxant. Blood flows in diaphragm during PSV6, PCV 6, 12cmH_2O were significantly smaller than that during PSV0cmH_2O (p<0.05). Blood flows in other organs including kidney and liver did not change significantly among ventilatory settings. We speculate that the difference of blood flow in diaphragm was derived from the inspiratory asynchrony between the ventilator and the animal. With this study we could establish a method to measure organ blood flow. Now we are trying to establish the microbubble method to measure regional liver tissue blood flow using the values measured by the coloredmicrosphere method as control values.