Patent ID: 7195711

Claim:
An in-vivo plasmapheresis and/or in-vivo ultrafiltration membrane comprising: a plurality of elongated hollow fibers, each fiber comprising an outer wall, a higher mass density outer wall zone and an outer wall surface for being exposed to whole blood, wherein said higher mass density outer wall zone has a pore size capable of separating plasma and plasma components from whole blood by passing plasma and plasma components therethrough, and one or more lower mass density inner wall zones, an inner wall and an interior lumen extending along the length thereof and defined by an inner wall surface, and characterized by having an average elongation breaking force strength of at least about 0.2 lbs. and an average elongation of at least about 45%, and wherein the fiber wall structure is a continuous change in mass density from said outer wall surface to said inner wall surface and comprises a continuum of voids bounded by solid frames and substantially without macrovoids.