Computer-Controlled Filtration and Strength Analysis of Blood Icroaggregates

A microcomputer-controlled blood filtration system was developed to control the filtration pressure independent of flowrate. Using the device, a mathematical model of constant-pressure filtration (CPF) of suspended particulars was confirmed using microspheres. Microaggregates were generated in whole citrated human blood by exposure to polymethylmethacrylate (PMMA) surfaces for 15, 30, and 60 minutes and were then filtered through 20μ pore filters at various pressures using the computer-controlled device. Resulting filtration flowrate curves were consistent with the mathematical model, and microemboli “effective concentrations” were obtained. The occlusion of the filters decreased with increasing filtration pressure, and an index of aggregate “fragility” was derived. As exposure time to the PMMA increased, the “effective concentration” of microemboli increased, but the average microaggregate strength did not change significantly. The contribution to filter blockage by a few very large microemboli (diameter > 100 μ) was estimated to be small, and arguments were presented for the absence of significant blood-filter interactions.