Electronic measurement of red cell flow in micropipettes.

The velocity of human erythrocytes in flow-through tubes of diameter less than 5 mum is measured as a function of driving pressure. The electrical resistance in the lumen of the tube increases when a cell is present, so a pulse can be generated of length inversely proportional to velocity. In the apparatus described the pulses and driving pressure are fed to a computer which derives the correlation between pressure and velocity. Experiments confirm that the resistance to flow of erythrocytes in a narrow tube is substantially the same as that of the suspending medium. The apparatus is being used to study the effects of changes in erythrocyte deformability on flow.