ABSTRACT
Membrane filtration technology has been used in extracorporeal medical devices since the first clinically successful hemodialyzer was developed in 1943. Filtration efficiency is governed by many parameters. These include: blood flow rate, pressure difference across the membrane, geometry of the blood flow path, composition and physical structure of the membrane, and the physicochemical nature of the substances that pass through the membrane. Membrane pore density is controlled by the irradiation time. Pore size is controlled by the etching time. The principal parameters of interest in membrane selection for almost any application are its rejection characteristics and its filtration rate. The most common problem arises from substances used during membrane preparation. Further, for a membrane to be effective in plasma exchange, it must be “wetted” by the blood. The patient’s blood viscosity is related to the plasma protein composition and the hematocrit, which influence module pressures and filtration rate.
