How is home hemodialysis technically performed when compared with conventional hemodialysis?
The common conventional in-center dialysis machine is a “single-pass system” (SPS) machine. A SPS machine produces dialysate within the machine by proportionally mixing acid and base concentrates with a purified water source. The dialysate then moves as a single-pass, high-flow fluid to the dialyzer for transmembrane contact with the patient’s blood. A SPS machine typically uses a dialysate flow to blood flow (Qd:Qb) ratio of 2:1. With an L-FS machine (like the NxStage), the flow rates are reversed so that Qd:Qb is between 1:2 and 1:3. This permits a more complete equilibrium between dialysate and patient’s blood, ultimately allowing for the use of less dialysate.