Blood processing systems and methods using apparent hematocrit as a process control parameter

A blood processing system comprising

• a centrifugal separation device rotatable about a rotational axis at a controlled rate of rotation, the separation device having an area A,
• an inlet path operable to convey whole blood at a determinable rate Qb into the separation device for separation into red blood cells and a plasma constituent, the whole blood in the inlet path having an actual whole blood hematocrit value, the red blood cells in the separation device having an actual red blood cell hematocrit value,
• an outlet path operable to remove plasma constituent from the separation device at a determinable rate Qp at least in part while whole blood is conveyed into the separation device,
• an outlet path operable to remove red blood cells from the separation device at least in part while whole blood is conveyed into the separation device and plasma is removed from the separation device,
• a controller including a stage operable, at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device, to derive a value Hb representing an apparent hematocrit of whole blood entering the separation device and a value Hrbc representing an apparent hematocrit of red blood cells within the separation device, where:
• Hb=f(Hrbc)
• and where:
• Hrbc=f(Qb, Qp, A, g, RBC)
• where:
• g represents a centrifugal acceleration factor based upon the controlled rate of rotation, and
• RBC represents at least one red blood cell dependent factor not including either the actual whole blood hematocrit value or the actual red blood cell hematocrit value, and
• the controller including a stage operable to generate a control command at least in part while whole blood is conveyed into the separation device and plasma and red blood cells are removed from the separation device, based, at least in part, upon Hb.