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Biomedical subjects

A Zelman

Publications and source records attributed to A Zelman.

15 recordsLinked to original sources
PubMed1981

Pressure control of ultrafiltration rate with high-flux dialysis membranes.

Control of ultrafiltration with high-flux dialysis membranes is normally achieved using complex, expensive, volumetric control methods. By using high-flux dialyzers with distensible membranes (parallel-plate dialyzers) in the cocurrent rather than in the countercurrent mode, ultrafiltration can be controlled simply and inexpensively by controlling the outlet pressure differential. Since this is the traditional method of ultrafiltration control, only minor, inexpensive equipment modifications are needed. As expected from transport theory, small molecule clearances are lower with cocurrent than with countercurrent flow. They are, however, adequate and superior to those achieved with post-dilutional hemofiltration (urea clearance greater than 110 ml/min with cocurrent single-pass, high-flux dialysis). Ultrafiltration control with this method is so simple and predictable that clearances at zero net ultrafiltration rates can easily be measured rather than extrapolated. Since dialysate pressure is always positive, no deaeration systems would be needed in dialysis equipment designed for use with cocurrent single-pass, high-flux dialysis.

Blood↗
PubMed1980

Controlled ultrafiltration during single-pass dialysis with the RP-6 dialyzer and evaluation of its time-dependent ultrafiltration index.

A simple and inexpensive method is described for controlling ultrafiltration when using the high flux RP-6 dialyzer. When th RP-6 is operated in the co-current mode and with single-pass dialysate delivery, (PBo-PDo) can be used to accurately and safely control ultrafiltration. Combined results from ten dialyses indicate there is a pressure-dependent concentration polarization which affects ultra-filtration as reported previously, and in addition, a time-dependent effect indicating a more complex dialyzer/blood interaction. The ultrafiltration index decreases linearly with time. The ultrafiltration can be adequately predicted by (Formula: see text).

Blood Flow Velocity↗
PubMed1979

A simple method for incorporating single pass dialysate delivery and controlled ultrafiltration with the RP-6 high flux dialyzer.

A simple hemodialysis protocol has been developed to permit significant "middle molecule" clearance, yet retain normal low molecular weight clearance. The high flux RP-6 dialyzer has been combined with a single pass dialysate delivery system to provide accurate control of ultrafiltration without resorting to specialized or expensive equipment. By operating the RP-6 in the co-current mode, a simple valve on the dialysate output can be used to regulate ultrafiltration. At QB = 200 ml/min and QD = 500 ml/min, CU = 127 ml/min and CB12 = 56 ml/min at zero ultrafiltration rate; these values increase considerably with ultrafiltration. This protocol offers dialysis centers with standard equipment the opportunity to use high flux membranes in a routine manner.

Animals↗
PubMed1979

In vitro characterization of the RP-6 dialyzer: co-current and counter-current clearance as a function of ultrafiltration.

Analytical and graphical techniques are described for presenting clearance data as a function of ultrafiltration; thus for the first time comparison of clearance values between dialyzers can be made unambiguously. This simple method uses a hand calculator to determine three coefficients. Clearance has been shown to be accurately described by the equation C = alpha 1 + alpha 2 Qv + alpha 3 (1/QBi). This formula permits construction of easily read families of curves which can predict clearance values under most clinical situations. The RP-6 dialyzer is characterized by these methods for clearance of urea, glucose and vitamin B 12 for counter-current and co-current modes.

Blood Flow Velocity↗
PubMed1979

Standards for accurate in vitro characterization of dialyzers: test case the Vivacell.

A standard format is proposed for cataloging dialyzer transport data in order to improve communication and understanding of published results. The need for such a format is obvious from the ambiguity and lack of uniformity in published data. This report for in vitro characterization also describes an adequate experimental set-up for proper dialyzer characterization and an improved means for reporting uncertainty where curve fitting techniques are employed. The Vivacell dialyzer has been evaluated by these means as the first test case.

Blood↗
PubMed1978

Hyper/hypo-osmotic peritoneal dialysis.

This report concerns the augmentation of peritoneal dialysis using alternating hyper/hypoosmotic peritoneal dialysates, and covers a detailed examination of the longest lived, anephric goat to be maintained using this delivery system. Experimental results show that with this technique: 1) urea clearance can be increased some 200% over control values, 2) the convective transport of urea is unimportant and the increased urea clearance is due primarily to increased peritoneal permeability, 3) net ultrafiltration and electrolyte balance can be easily controlled by variation of total electrolyte and glucose about an appropriate mean. A detailed autopsy failed to demonstrate any gross or microscopic pathology.

Abdomen↗
PubMed1972

Membrane permeability. Generalization of the reflection coefficient method of describing volume and solute flows.

The reflection coefficient method for describing volume and solute fluxes through membranes is generalized to take into account the nonideality of the solutions bathing the membrane and/or multicomponent systems. The reflection coefficient of the impermeable species in these systems is less than unity by a coefficient gamma. The reflection coefficient obtained solely from the volume flow equation, sigma(v), will always be less than the reflection coefficient obtained from the solute flow equation, sigma(8) (v). These two coefficients are related by sigma(8) (v) = sigma(v) + gamma.

Chemical Phenomena↗