Abstract
The red blood cell (RBC) sediment formation was studied using an optical method. The intensity of light transmitted through the blood sample was measured as a function of time and distance from the bottom of the sample. Blood was obtained from healthy donors and measurements were performed at initial hematocrits ranging from 30 to 50%. Sedimentation curves and time dependence of the intensity averaged along the height of the RBC suspension were determined to give a cumulative description of the process. Detailed analysis of the transmitted light intensity revealed a moving interface between sedimenting RBC aggregates and the forming of a deposit of the cells. It was shown that although there is no discontinuity in the intensity an averaged interface can be found. A novel curve describing the sedimentation process called the deposit formation curve was found. Below this curve a formation of the RBC deposit occurs. Firstly, this curve represents the position of the interface between sedimenting RBC aggregates and a forming deposit, secondly this curve coincides with the last part of the sedimentation curve.