Three-line apheresis system and method

A discontinuous blood processing system for collecting and exchanging blood components comprising;

• a venous-access device for drawing whole blood from a subject and returning blood components to the subject;
• a blood component separation device for separating the drawn blood into a first blood component and a second blood component, the blood component separation device having an outlet and being configured to send the first blood component to a first blood component bag, the blood component separation device alternating between discharging the first blood component and the second blood component through the same outlet of the blood component separation device;
• a blood draw line fluidly connected to the venous-access device and configured to transport drawn whole blood to the blood component separation device, the flow through the blood draw line being controlled by a blood draw pump;
• an anticoagulant line connected to an anticoagulant source, the anticoagulant line introducing anticoagulant into the drawn whole blood, the flow through the anticoagulant line being controlled by an anticoagulant pump;
• a dilution/extraction line fluidly connected to the first blood component bag and the blood component separation device, the dilution/extraction line being configured to reintroduce the first blood component from the first blood component bag into the blood component separation device;
• a return line fluidly connected to the venous-access device and the blood component separation device for returning blood components remaining within the separation device to the patient, the flow through the return line being controlled by a return pump, wherein the return line fluidly connects to the venous-access device at a point between the blood draw pump and the venous-access device;
• and
• a compensation fluid line configured to be connected to a compensation fluid source and fluidly connected at a point on the return line between the venous access device and the blood component separation device, the compensation line for returning compensation fluid to the subject.