Closed hemapheresis system and method

Abstract

A hemapheresis system and method in accordance with the invention comprises a stationary closed housing concentric about a central axis and a feed system that moves blood upwardly from the housing lower end toward an outlet port adjacent a substantially closed upper end. Within the stationary housing is a double walled rotor concentric with the housing and rotatable by magnetic means within the housing on sealed end bearings. The space between the rotor walls defines a centrifugation gap into which whole blood is passed and within which centrifugal separation takes place as the rotor is spun at a relatively low rate. Whole blood also seeks to flow upwardly in the space between the rotor and housing, but this path is arranged to have a substantially higher flow impedance, so that the preferential path is within the centrifugation gap. At the upper end of the rotor, lighter matter such as plasma rich in platelets passes continuously inwardly to a central lengthwise passageway leading to an outlet port coaxial with the central axis, while heavier central matter flows through apertures in the outer rotor wall to the upper outlet port. In one example the differential impedance is established by housing and rotor configurations which diverge outwardly with compound curvatures, and with the space between rotor and housing leading to a closed end. In another example the housing-rotor space is of restricted cross section and an opposing flow of compatible fluid is introduced in an intermediate region of the flow path.