Optical digital registration of erythrocyte sedimentation and its modeling in the form of the collective process

The dependence of the sedimentation rate of donor blood on its percentage in the sample (the degree of its dilution with physiologic saline) ranging from 0.25 to 100% (whole undiluted blood) is investigated with digital video equipment. The ratio of the value of displacement of the sediment–supernatant boundary per time unit was taken as the blood sedimentation rate. In case of registration of different speeds of movement of this boundary in a given volume of the cuvette, their spatial averaging was performed. A substantial increase in the blood sedimentation rate was found experimentally at high levels of its dilution, and, conversely, at blood concentrations in physiologic saline solutions that are close to whole blood. At the same time, the rate of blood sedimentation decreased several times with blood content in the range of 30–50%. It was experimentally shown that variation of blood content in the physiologic saline solution over a wide range did not affect the evenness of sedimentation occurring for almost any blood concentration in the mixture. In other words, in the process of sedimentation of a single blood sample of a given dilution in the physiologic saline solution, the sedimentation rate does not change with time. The experimentally obtained results allowed to build a theoretical model of blood sedimentation for two cases: 1) sedimentation of free erythrocytes (highly diluted blood) and 2) sedimentation of erythrocyte aggregates (almost undiluted blood, up to whole blood). The originality of the model comes from the proposition to consider the sedimentation of cells and/or their aggregates as a collective effect, and not in the traditional form of sedimentation of individual particles or particles interacting with each other. This model gives a satisfactory agreement with experimental laws with the use of certain empirical constants. The study is useful for understanding the process of erythrocyte sedimentation.