RBC-aggregation and –relaxation measurements

The state of RBC (dis-)aggregation is shear rate dependent: at high shear rates, all red cells in normal human blood are dispersed and deformed. At very low shear rates or at stasis, aggregates (rouleaux) will form. RBC aggregation behaviour can be studied from light intensity measurements; both changes in light absorption and in light back scatter can be used. The LoRRca applies a light back scatter system.

Various aggregation indices can be determined in whole blood by means of back scatter measurements. A diode laser, which is mounted inside the BOB, serves as light source. Light that is back scattered by the layer of blood in the gap is collected by two photodiodes inside the static BOB and is converted into an electrical signal (Figure 5).