A high efficiency membrane separator for donor plasmapheresis

The shortfall in human plasma for therapeutic use can be met satisfactorily only by donor plasmapheresis. Membrane blood plasma separators of conventional design work poorly at low rates of blood flow, and performance decreases rapidly as the membrane becomes fouled. To overcome these problems, membrane separators have been developed that employ vortex mixing to prevent blood cells obstructing the membrane pores. These separators consist of a single blood channel 160 mm long by 62.5 mm wide. The two membranes that act as boundaries for the blood channel are thermoformed to provide a closely packed array of outward facing dimples. The membranes are seated on rigid support plates, and flexible diaphragms are attached to each end of the blood channel. The diaphragms were oscillated in antiphase at 3 to 6 Hz, with a stroke volume of 2.8 ml. In 24 clinical trials, mean plasma filtration rate was 18 ml/min at a blood inlet flow of 48 ml/min. In 10 experiments using bovine blood, mean plasma filtration rate was 35 ml/min at a blood inlet flow of 90 ml/min. Little reduction in performance was observed over 80 min. The membrane area was 200 sq cm, which gave a filtration velocity of 1.75 L/min/m2, higher by a factor of five than is reported for hollow fiber or flat plate designs.