Abstract
If a steady flow rate of a Newtonian liquid is established in a capillary device (having many equal-sized capillaries in parallel) and then the liquid entering the device is changed to blood, with the flow rate kept constant, the pressure drop across the device rises to a peak which exceeds the ultimate steady pressure drop associated with blood flow. The effect has been observed in bundles of parallel capillaries ranging in diameter from 200 to 1000 μm, lengths 3–200 mm and numbers of capillaries from 14 to ca. 50,000, in experiments using fresh anti-coagulated blood with hematocrits ranging from 20 to 72%. The strength of the effect varies with conditions. The cumulative flow of blood required to reach the pressure peak can be several times the priming volume of the capillary device, and decreases with increase in flow rate.
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