Multistage hemodiafiltration/hemofiltration method and apparatus

In a blood dialysis system including a source of substitution fluid and a blood dialysis machine, a hemodiafiltration/hemofiltration system comprising:

• a first dialyzer including:
• a first semi-permeable membrane partitioning said first dialyzer into:
• a first blood compartment having a first blood inlet which receives blood to be cleaned and a first blood outlet which discharges partially diafiltered blood;
• and a first dialysate compartment having a first dialysate inlet and a first dialysate outlet;
• a mixing chamber for mixing said partially diafiltered blood with substitution fluid from said source to obtain a blood/substitution fluid mixture;
• a second hemofilter including:
• a second semi-permeable membrane partitioning said second hemofilter into:
• a second blood compartment having a second blood inlet which receives said blood/substitution fluid mixture and a second blood outlet which discharges filtered blood;
• and a second permeate compartment having a second permeate outlet;
• and a control feature for regulating filtration in at least one of said first dialyzer and said second hemofilter, wherein the control feature comprises:
• a permeate pump disposed along a permeate conduit that is connected at a first end to said second permeate outlet and at a second end to a dialysate conduit that is connected to said first dialysate outlet for carrying dialysate fluid from said first dialysate compartment, said permeate conduit for carrying plasma water from said second hemofilter and being in communication with said dialysate conduit at a location downstream of said permeate pump, said permeate pump for selectively regulating a first fluid pressure of said second permeate compartment relative to a second fluid pressure of said first dialysate compartment.

In a blood dialysis system including a source of substitution fluid and a blood dialysis machine, a hemodiafiltration/hemofiltration system comprising:

• a first dialyzer including:
• a first semi-permeable membrane partitioning said first dialyzer into:
• a first blood compartment having a first blood inlet which receives blood to be cleaned and a first blood outlet which discharges blood having a first concentration of toxins;
• and a first dialysate compartment having a first dialysate inlet and a first dialysate outlet;
• a mixing chamber for mixing said discharged blood from said first dialyzer with substitution fluid from said source to obtain a blood/substitution fluid mixture;
• and a second hemofilter including:
• a second semi-permeable membrane partitioning said second hemofilter into:
• a second blood compartment having a second blood inlet which receives said blood/substitution fluid mixture and a second blood outlet which discharges blood having a second concentration of toxins, the first concentration being greater than the second concentration;
• and a second permeate compartment having a second permeate outlet;
• and a controller for regulating filtration rates in said first dialyzer and said second hemofilter based upon predetermined input, wherein a dialysate conduit is connected at one end to said first dialysate outlet for carrying spend dialysate fluid from said first dialysate compartment;
• a permeate conduit connected at one end to said second permeate outlet and being in communication, at an opposite end, with said dialysate conduit;
• and wherein said permeate conduit carries plasma water that has been filtered across said second semi-permeable membrane to said dialysate conduit, whereby said plasma water bypasses said first dialyzer.

A method of hemodiafiltration/hemofiltration comprising the steps of:

• receiving a blood inflow;
• diafiltering said blood inflow in a first stage to provide a partially diafiltered blood outflow;
• mixing said partially diafiltered blood outflow with a substitution fluid to provide a blood/substitution fluid mixture;
• hemofiltering said blood/substitution fluid mixture in a second stage;
• and providing a flow control feature in a dialysate conduit that carries spent dialysate fluid from the first stage, connecting a permeate conduit that carries plasma water derived from the second stage to said dialysate conduit at a location downstream of said flow control feature;
• and wherein the flow control feature permits a hemodiafiltration rate of the first stage and a hemofiltration rate of the second stage to be varied with respect to one another.

A method of hemodiafiltration/hemofiltration comprising the steps of:

• receiving a blood inflow;
• diafiltering said blood inflow in a first stage to provide a partially diafiltered blood outflow;
• mixing said partially diafiltered blood outflow with a substitution fluid to provide a blood/substitution fluid mixture;
• hemofiltering said blood/substitution fluid mixture in a second stage;
• and disposing a permeate pump in a permeate conduit that carries plasma water derived from the hemofiltering step from said second stage, connecting said permeate conduit at one end to a dialysate conduit that carries spent dialysate derived from said hemodiafiltration step;
• and operating said permeate pump so that a hemodiafiltration rate of the first stage and a hemo filtration rate of the second stage are varied with respect to one another.