Theoretical model of blood flow through hollow fibres considering hematocrit-dependent, non-Newtonian blood properties.
Accounting for the non-Newtonian blood viscosity by the Quemada descriptive viscosity equation, we deduced velocity profiles and volumetric capillary flows from the Navier-Stokes-equation. An arbitrary axial and/or radial hematocrit profile can be chosen. The hematocrit dependence of the intrinsic viscosities k0 (H) (characterizing, at least in part, the RBC aggregation) and k infinity (H) (describing orientation/deformation of RBC) was taken into account. Velocity profiles for pressure gradients of 4-4000 Pa/cm show a distinct flattening, if a pronounced axial migration of RBC is assumed. The higher the axial concentration, the higher the flow at the same pressure gradient. Small deviations (less than or equal to 10%) of the capillary number per dialyzer or of the radius of capillaries lead to a strong change of the pressure gradient with the same dialyzer flow. Whereas small hydraulic conductivities do not significantly change this gradient, high conductivities decrease the pressure gradient by about 10%. Impaired blood flow properties (hemoconcentration) result in a slight deviation from the linear axial pressure drop.
Lerche
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Humboldt University Berlin, Medical School (Charité), Berlin, Germany.
Oelke
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D001783:Blood Flow Velocity; D001809:Blood Viscosity; D002196:Capillaries / Q000502:physiology*; D006400:Hematocrit; D008955:Models, Cardiovascular; D006435:Renal Dialysis; D012212:Rheology; D014655:Vascular Resistance / Q000502:physiology