TY - JOUR
T1 - Rheological effects of red blood cell aggregation in the venous network
T2 - A review of recent studies
AU - Bishop, Jeffrey J.
AU - Popel, Aleksander S.
AU - Intaglietta, Marcos
AU - Johnson, Paul C.
PY - 2001
Y1 - 2001
N2 - It has long been recognized that understanding the rheological properties of blood is essential to a full understanding of the function of the circulatory system. Given the difficulty of obtaining carefully controlled measurements in vivo, most of our current concepts of the flow behavior of blood in vivo are based on its properties in vitro. Studies of blood rheology in rotational and tube viscometers have defined the basic properties of blood and pointed to certain features that may be especially significant for understanding in vivo function. At the same time, differences between in vivo and in vitro systems combined with the complex rheological properties of blood make it difficult to predict in vivo blood rheology from in vitro studies. We have investigated certain flow properties of blood in vivo, using the venular network of skeletal muscle as our model system. In the presence of red blood cell aggregation, venous velocity profiles become blunted from the parabolic as in Poiseuille flow, as pseudo-shear rate (= mean fluid velocity/vessel diameter) is decreased from ∼100 s-1 to 5 s-1. At control flow rates, the short distance between venular junctions does not appear to permit significant axial migration and red cell depletion of the peripheral fluid layer before additional red cells and aggregates are infused from a feeding tributary. Formation of a cell-free plasma layer at the vessel wall and sedimentation in vivo are evident only at very low pseudo-shear rates (< 5 s-1). These findings may explain in large part observations in whole organs of increased venous resistance with reduction of blood flow.
AB - It has long been recognized that understanding the rheological properties of blood is essential to a full understanding of the function of the circulatory system. Given the difficulty of obtaining carefully controlled measurements in vivo, most of our current concepts of the flow behavior of blood in vivo are based on its properties in vitro. Studies of blood rheology in rotational and tube viscometers have defined the basic properties of blood and pointed to certain features that may be especially significant for understanding in vivo function. At the same time, differences between in vivo and in vitro systems combined with the complex rheological properties of blood make it difficult to predict in vivo blood rheology from in vitro studies. We have investigated certain flow properties of blood in vivo, using the venular network of skeletal muscle as our model system. In the presence of red blood cell aggregation, venous velocity profiles become blunted from the parabolic as in Poiseuille flow, as pseudo-shear rate (= mean fluid velocity/vessel diameter) is decreased from ∼100 s-1 to 5 s-1. At control flow rates, the short distance between venular junctions does not appear to permit significant axial migration and red cell depletion of the peripheral fluid layer before additional red cells and aggregates are infused from a feeding tributary. Formation of a cell-free plasma layer at the vessel wall and sedimentation in vivo are evident only at very low pseudo-shear rates (< 5 s-1). These findings may explain in large part observations in whole organs of increased venous resistance with reduction of blood flow.
KW - Axial migration
KW - Blood viscosity
KW - Red blood cell sedimentation
KW - Velocity profiles
KW - Venous vascular resistance
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M3 - Review article
C2 - 11381180
AN - SCOPUS:0034977555
SN - 0006-355X
VL - 38
SP - 263
EP - 274
JO - Biorheology
JF - Biorheology
IS - 2-3
ER -