Blood processing method and apparatus with disposable cassette

DETAILED DESCRIPTION An apparatus for regulating fluid flow in a blood processing system (such as a blood washing system) includes a motor driven rotor for a peristaltic pump which has a plurality of rollers disposed about the circumference of the rotor.
A disposable cassette houses a flexible tube and manifolds through which fluid flows.
The cassette has a curved platen against which the flexible tube resides.
The cassette is removably secured to the apparatus such that the flexible tube is in contact with both the platen and rollers of the rotor.
A fluid flow is then induced through the tube by rotation of the rotor.
In the preferred embodiment, the flexible tube is a primary flexible tube, and the cassette further includes a manifold which connects a plurality of secondary flexible tubes to the primary flexible tube.
This connection allows fluid flow between the primary flexible tube and each of the secondary flexible tubes.
A plurality of valving elements are provided.
Each element controls the flow of fluid through one of the secondary flexible tubes.
In the preferred embodiment, these valving elements are solenoid controlled pneumatically operated pinch valves.
The cassette includes closing surfaces, or anvils, against which the pinch valves individually occlude the secondary flexible tubes to restrict the fluid flow through the tubes.
The valves are spring biased in a normally-closed position such that with the cassette in place on the working surface, the pinch valves keep the secondary tubes occluded when electrical power to the apparatus is interrupted.
The securing mechanism of the apparatus preferably includes a handle which closes over the disposable cassette, and holds the flexible tube between the rollers of the rotor and the platen of the cassette.
A securing mechanism (in the preferred embodiment a drag bar) moves with motion of the handle, and contacts the cassette, drawing it toward the pump rotor as the handle is moved toward the closed position.
Side rails and a top rail restrict the motion of the cassette in first and second mutually perpendicular directions when it is positioned on the working surface