ELECTROCHEMICAL ANALYSIS OF BLOOD CELL SUBSTRATE INTERACTIONS OF UNDER FLOW CONDITIONS/

Interactions of blood cells (RBCs) with a microelectrode of 50 mu m di ameter have been examined under flow conditions using impedance measur ements at high frequencies. At such frequencies, the electrolyte resis tance (R(e)) is assimilated to the real part of impedance, and interac tions are associated with transient fluctuations of R(e). Sedimentatio n experiments suggest that one erythrocyte contributes to 1.1% R(e) in crease. Effects of wall shear rate (from 25 to 140 s(-1)) and RBC conc entration (from 8.4 x 10(5) to 2.7 x 10(6) cells/ml) have been investi gated; the number of interactions rapidly decreases with wall shear ra te. Event frequency is proportional to RBC concentration ranging from 3.1 x 10(6) cells/ml to 1.3 x 10(7) cells/ml. At high concentrations o f RBCs, some transient events overlap. Videotaped images help to deter mine how many RBCs interact with the microelectrode at the same time o n separate surface areas. Under flow conditions, the contribution of o ne RBC on the R(e) increase is similar to the mathematical value obtai ned by sedimentation and decreases slightly with wall shear rate.