Abstract
Erythrocyte deformability can be measured as filterability through a polycarbonate filter. To evaluate the influence of variations in filtration pressures the present study was performed as filtration of red cell suspensions with a pore size of 5 um at constant negative pressures of −10, −20, −30, −40 and −50 mm H2O in the St. George's Filtrometer. Filtration parameters were expressed as passage time, flow rate, flow resistance, initial relative filtration rate (IrFR) , red cell transit time (RCTT) and clogging particles (CP). Passage time was decreased and flow rate was increased significantly at all filtration pressures compared to preceding pressure level (p<0.001). In the pressure range −10 to −30 mm H2O flow resistance decresed significantly (p<0.001) , but was almost constant in the range −30 to −50 mm H2O. Also IrFR and RCTT showed a significantly greater change (p<0.001) when the pressure was increased from −10 to −20 mm H2O compared to the same pressure change in the range −30 to −50 mm H2O. CP varied more with pressure, but the greatest change was found in the range −10 to −20 mm H2O. Variations of MCV within the normal range were associated with changes in passage time, flow resistance and CP in the pressure range −20 to −50 mm H2O.
It is concluded that the filtration pressure is an important factor in studies on blood cell filterability. For the St. George's Filtrometer the optimal pressure range seems to be −30 to −50 mm H2O.
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