An automated real time capillary viscometer

Abstract

Abstract-This study describes how to establish a capillary viscometer (microviscosimeter) that uses an inline microflowmeter that can accurately measure whole blood effective viscosity in tubes of arteriolar diameter at physiologically nominal flow rates with all benefits of digital media. Total measurement time is 4 minutes. The data can be digitally handled. Currently this system is assembled at the Department of Anatomy, Istanbul Medical School, University of Istanbul. The system diagnoses elevated viscosity as a routine procedure providing valuable criteria for many clinical manifestations. Keywords -Capillary viscometer, microviscometer, blood viscosity I. INTRODUCTIONViscosity as a hemorheological criteria has become far more important after the clinicians started to blame it for some pathological conditions. There is a bunch of study showing that the blood viscosity is apparently relevant with erythrocyte aggregation, endothelial damage, intimal thickening, coronary artery disease and diabetic ischemia.Clinical manifestations of coronary and cerebrovascular disease are associated with an increased blood viscosity [1,2]. Plasma viscosity is predictive of ischemic heart disease events in a free-living population [3] and progression to acute myocardial infarction in patients with unstable angina pectoris [4]. Abnormalities in blood rheology, including elevations of blood and plasma viscosity, are related to vascular complications in Diabetes Mellitus [5].The rise in blood viscosity accounts for clinical manifestations of Polycythemia that have been observed in approximately 50 % of newborn infants with hematocrit values of 0.65 or greater. In neonates, hyperviscosity increases the risk of pulmonary hypertension, renal failure, necrotizing enterocolitis, cerebral ischemia, intracranial hemorrhage, and developmental retardation [6][7][8][9][10].Currently, most of the researchers have used very conventional types of viscometers (cone-in-cone or cone-onplate) or newer or developing systems such as ball or capillary types for measuring blood and plasma viscosity. Among all these type of viscometers, capillary type of viscometers seem to be more reliable than the others, because the blood flows in vessels that have similar geometry and size with capillary tubes of these instruments.The capillary viscometer created by Kirby [11] is closer to the physiological system, because of the velocitycontrolled nature of his instrument.Kirby's system consisted of three parts; capillary tubes, transducers and amplifers, and a paper-chart recorder.Kirby collects at least 38 data from paper chart by counting squares. Surely, this method is very slow, inaccurate and impractical. Also, it yields high observation error, limited number of data points, and low accuracy. To overcome the handicaps of this system's time consuming third part, we proposed a digital system. II. METHODOLOGY A. TheoryWhen fluid is flowing steadily through the entire system, the modified Hagen-Pouiseuille flow relationship holds throughout the flow system su...