HDF is a blood purification methods that incorporates a convective-type driving force in addition to diffusional-type. The convection is caused by creating a positive pressure gradient across the dialyzer membrane. The pressure causes uremic plasma water to flow across the membrane, pulling large molecular weight uremic toxins across the membrane as well.
To stay in fluid balance, HDF requires the addition of a purified or sterile substitution fluid to be infused back into the blood to replace the flow of uremic plasma water.
Standard Hemodialysis (HD)
HD is primarily a diffusive-type blood purification method that relies on differences in concentration as the driving force to remove toxins from of uremic blood. This method is effective for small uremic toxins like Urea. However HD is less effective at removing larger molecular weight uremic toxins, like beta-2-microglobulin.
HD is primarily performed in an outpatient clinic, but is often performed in an acute hospital setting. Recent developments have enabled HD to be performed in the home setting.
The Nephros HDF Solution
Nephros has designed and patented the OLpür H2H Module and HDF Filter to be used in conjunction with a standard HD machine to deliver HDF therapy. The H2H Module is connected to fresh dialysate fluid line from the HD machine. The H2H Module delivers ultrafiltered dialysate to the HDF Filter to enable both diffusive-type and convective-type forces to remove uremic toxins, and to provide substitution fluid to replace fluid loss from convection.
The Nephros HDF Filter, OLpür MD220, provides a unique solution to standard HDF, which is commonly used in Europe. For practical reasons, the injection location of the substitution fluid is typically performed either before or after the blood flows through the dialyzer. The mid-filter location of substitution fluid injection attempts to maximize the positive impact of both post-dilution and pre-dilution injection modalities.
As show in the picture below, the patented HDF Filter is a two stage device. In the first stage, incoming blood flows down a portion of the hollow fibers making up an annular area of the outside of the fiber bundle and is discharged into the substitution header region at the other end. Substitution fluid is infused into the substitution header and mixes with the blood exiting from stage 1. In stage 2, the mixture flows through the remaining portion of hollow fibers in the core area of the fiber bundle. After passing through the hollow fibers of Stage 2, blood enters the center header region of the two-port cap and exits out the blood outlet port of the device. Dialysate flows in one direction that is counter-current to blood flow in stage 1 and co-current to blood flow of stage 2.
OLpur® H2H Hemodiafiltration Module
The OLpur® H2H Hemodiafiltration Module (H2H Module) utilizes a standard HD machine to perform on-line hemodiafiltration therapy. The HD machine controls and monitors the basic treatment functions, as it would normally when providing HD therapy.
The H2H Module is a free-standing, movable device that is placed next to either side of an HD machine. The H2H Module is connected to the clinic’s water supply, drain, and electricity.
The Nephros OLpur H2H Module has received FDA 510(k) clearance in the U.S.A.
OLpur® MD220 Hemodiafilter
The OLpur® MD220 Hemodiafilter (HDF Filter) is very similar to a typical hollow fiber dialyzer assembled with a single hollow fiber bundle made with a high-flux (or high-permeability) membrane. The fiber bundle is separated into two discrete, but serially connected blood paths. Dialysate flows in one direction that is counter-current to blood flow in Stage 1 and co-current to blood flow of Stage 2.