A MATHEMATICAL-MODEL FOR FLOW, PRESSURE, AND ULTRAFILTRATION RATE IN EXTRACORPOREAL FILTRATION OF BLOOD

A mathematical model of extracorporeal hydraulics (pressures and flows ) has been developed for common extracorporeal blood purification moda lities. The model includes a description of the blood pathway which ac counts for Hagan-Poiseuille flow and for pathway contractions and expa nsions. The hemofilter description accounts for membrane-limited and b oundary layer limited ultrafiltration. In vitro experiments using huma n blood in ultrafiltration circuits have been conducted to test the va lidity of this model. Pressures and flows of blood and ultrafiltrate w ere measured as a function of ultrafiltrate pressure. Computer simulat ions developed from the model were run based on the experimental start ing conditions. The results of these simulations were compared with th ose obtained by experiment. The agreement among results was good. This model can be used to evaluate the effect of design parameter changes on circuit pressures and flows for systems such as hemodialysis, hemof iltration, or continuous arteriovenous hemofiltration.