A
system for filtering and
processing blood that is simple to implement and that reduces the need for human intervention. The
system may be used to collect red blood cells (RBCs). For such a
system, a disposable set may be provided with an inlet port, an RBC container, a
centrifuge rotor having a variable total volume, and a filter, along with tubing connecting the port, the container, the rotor and the filter. The filter is located in tubing between the inlet port and the rotor. A
control unit is also provided and includes a spinner in which the rotor may be held, a flow-control arrangement for controlling flow among the various components of the disposable set, and an
electronic controller. The
whole blood is directed by the flow-control arrangement from the inlet through the filter to the rotor. The rotor includes an elastic diaphragm, and the
control unit's flow-control arrangement includes a pump or other device for applying a positive and negative pressure to the rotor's elastic diaphragm. The spinner rotates the rotor so as to separate the
whole blood into
plasma and RBCs. Preferably, the
plasma is urged out of the rotor first and returned to the donor, while the rotor is still being spun. After the
plasma has been removed from the rotor, the RBCs are urged from the rotor to an RBC container. In preferred embodiments, the filter is a
white blood cell filter, so that white blood cells are filtered from the blood before it reaches the rotor.