The clinical impact of catheter diameter variability on performance of neonatal continuous arteriovenous hemofiltration (CAVH) systems was shown by demonstration of the effect of catheter inner diameter on catheter and CAVH system blood flow. Diameter of 3.5 Fr and 5 Fr catheters was determined by experimental measurement of catheter flow-pressure drop relationship with known equations for fluid flow. Physical measurements verified the accuracy of the calculated diameters. These diameters were then used in a mathematical simulation to describe blood flow through an entire neonatal CAVH system and predict clinical performance. Catheters of 5 Fr caliber had a 39% variation in diameter among manufacturers, resulting in a 370% variation in blood flows; 3.5 Fr catheters had a 29% variation in internal diameter with a corresponding blood flow variation of 290%. Computer simulation of a neonatal CAVH system revealed a maximum blood flow of 0.8-3.0 ml/min with available 5 Fr catheters. This wide variation is probably responsible for the lack of consistant results in neonatal CAVH systems to date.
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