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Effects of erythrocyte deformability and aggregation on the cell free layer and apparent viscosity of microscopic blood flows.

ABSTRACT: Concentrated erythrocyte (i.e., red blood cell) suspensions flowing in microchannels have been simulated with an immersed-boundary lattice Boltzmann algorithm, to examine the cell layer development process and the effects of cell deformability and aggregation on hemodynamic and hemorheological behaviors. The cells are modeled as two-dimensional deformable biconcave capsules and experimentally measured cell properties have been utilized. The aggregation among cells is modeled by a Morse potential. The flow development process demonstrates how red blood cells migrate away from the boundary toward the channel center, while the suspending plasma fluid is displaced to the cell free layer regions left by the migrating cells. Several important characteristics of microscopic blood flows observed experimentally have been well reproduced in our model, including the cell free layer, blunt velocity profile, changes in apparent viscosity, and the Fahraeus effect. We found that the cell free layer thickness increases with both cell deformability and aggregation strength. Due to the opposing effects of the cell free layer lubrication and the high viscosity of cell-concentrated core, the influence of aggregation is complex but the lubrication effect appears to dominate, causing the relative apparent viscosity to decrease with aggregation. It appears therefore that the immersed-boundary lattice Boltzmann numerical model may be useful in providing valuable information on microscopic blood flows in various microcirculation situations.

SUBMITTER: Zhang J

PROVIDER: S-EPMC2917820 | biostudies-literature | 2009 May

REPOSITORIES: biostudies-literature

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Effects of erythrocyte deformability and aggregation on the cell free layer and apparent viscosity of microscopic blood flows.

Zhang Junfeng J Johnson Paul C PC Popel Aleksander S AS

Microvascular research 20090204 3

Concentrated erythrocyte (i.e., red blood cell) suspensions flowing in microchannels have been simulated with an immersed-boundary lattice Boltzmann algorithm, to examine the cell layer development process and the effects of cell deformability and aggregation on hemodynamic and hemorheological behaviors. The cells are modeled as two-dimensional deformable biconcave capsules and experimentally measured cell properties have been utilized. The aggregation among cells is modeled by a Morse potential ...[more]

PMID: 19323969

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Project description:Erythrocyte cell membranes undergo morphologic changes during storage, but it is unclear whether these changes are reversible. We assessed erythrocyte cell membrane deformability in patients before and after transfusion to determine the effects of storage duration and whether changes in deformability are reversible after transfusion.Sixteen patients undergoing posterior spinal fusion surgery were studied. Erythrocyte deformability was compared between those who required moderate transfusion (? 5 units erythrocytes) and those who received minimal transfusion (0-4 units erythrocytes). Deformability was measured in samples drawn directly from the blood storage bags before transfusion and in samples drawn from patients before and after transfusion (over 3 postoperative days). In samples taken from the blood storage bags, we compared deformability of erythrocytes stored for a long duration (? 21 days), those stored for a shorter duration (<21 days), and cell-salvaged erythrocytes. Deformability was assessed quantitatively using the elongation index (EI) measured by ektacytometry, a method that determines the ability for the cell to elongate when exposed to shear stress.Erythrocyte deformability was significantly decreased from the preoperative baseline in patients after moderate transfusion (EI decreased by 12% ± 4% to 20% ± 6%; P = 0.03) but not after minimal transfusion (EI decreased by 3% ± 1% to 4% ± 1%; P = 0.68). These changes did not reverse over 3 postoperative days. Deformability was significantly less in erythrocytes stored for ? 21 days (EI = 0.28 ± 0.02) than in those stored for <21 days (EI = 0.33 ± 0.02; P = 0.001) or those drawn from patients preoperatively (EI = 0.33 ± 0.02; P = 0.001). Cell-salvaged erythrocytes had intermediate deformability (EI = 0.30 ± 0.03) that was greater than that of erythrocytes stored ? 21 days (P = 0.047), but less than that of erythrocytes stored <21 days (P = 0.03).The findings demonstrate that increased duration of erythrocyte storage is associated with decreased cell membrane deformability and that these changes are not readily reversible after transfusion.

Dataset Information

Effects of erythrocyte deformability and aggregation on the cell free layer and apparent viscosity of microscopic blood flows.

Publications

Effects of erythrocyte deformability and aggregation on the cell free layer and apparent viscosity of microscopic blood flows.

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