Filterability of equine erythrocytes and whole blood: Effects of haematocrit, pore size and flow rate

Abstract

The filterability of equine RBC and whole blood was evaluated to better understanding the effects of exercise-associated haemoconcentration and increased cardiac output on the flow properties of blood in the microvasculature. When RBC were filtered through filters with 3 µm pores (3 µm filters), the initial increase in filtration pressure (Pi) increased 4.6-fold between packed cell volumes (PCV) of 5% and 40%. Filters with 5 µm pores had lower Pi at all PCV studied and the absolute increase in Pi with increasing PCV was minimal. Increasing the flow rate resulted in marked increases in Pi for 3 µm filters. The Pi for 5 µm filters also increased with increasing flow rate but values were consistently less than for 3 µm filters. The Pi values for horse RBC were less than those for human RBC at all flow rates evaluated. Calculated wall shear stress values were much higher for 3 µm filters than those for 5 µm filters. Filtration pressures and wall shear stress values for whole blood were greater than those for RBC for both 3 µm and 5 µm filters. These data suggest that changes in PCV and flow rate may significantly alter shear forces in the microvasculature particularly in vessels approaching 3 µm in diameter.