Molecular separation may prove to be an inexpensive and simple artificial kidney technique if the problems of concentration polarization and practical implementation of a multistage design can be overcome. The potential of available membranes and hydraulic means of controlling protein deposition were investigated with 4 different experimental test units in a continuous system where pressure and flow could be varied independently. Short entrance lengths within a flat plate minimized the protein gel problem compared to long narrow channels or jet impingement on the membrane surface. Water filtrate fluxes could be approached with a low permeability membrane at high flow rates. As the basic membrane permeability increased, protein gel formation limited filtration to values only slightly higher than with the low permeability membranes. Approximate theoretical mass balances were utilized to assess the magnitude of transfer coefficients and gel properties. When concentration polarization dominated filtration, electrolyte and end metabolic product rejections decreased as the protein gel developed with time. Under these conditions, preferential passage of end metabolic products occurred compared to sodium. Transfer coefficients to and from the membrane surface were high and comparable to theoretical predictions prior to the long term build up of surface proteins, but then decreased by more than a factor of 10 as the gel thickened. Suitable membranes are available for staged molecular separation of body fluids. Complexing of end metabolic products after gross filtration was discussed as a means of minimizing reconstituting fluids. It was noted that filtration was noticeably improved with blood compared to plasma when the protein gel dominated transfer. By designing a multistage preclinical test unit to minimize protein deposition, the concept of molecular separation may become practical. However, advances in correlation of the data and a better theoretical understanding are needed to develop an optimal device. In addition, the possibilities of interstage complexing and selective membrane properties must be investigated.
|Original language||English (US)|
|Number of pages||7|
|Journal||Transactions - American Society for Artificial Internal Organs|
|State||Published - Apr 1970|
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