Renal failure therapy machines and methods including convective and diffusive clearance

1. A renal failure therapy machine comprising:

a blood cleaning filter;

a dialysis fluid circuit including a balance chamber, the balance chamber including a fresh dialysis fluid compartment configured to send fresh dialysis fluid to the blood cleaning filter and a used dialysis fluid compartment configured to receive used dialysis fluid from the blood cleaning filter;

a fresh dialysis fluid line in fluid communication with the fresh dialysis fluid compartment of the balance chamber and the blood cleaning filter; and

a flow restrictor in fluid communication with the blood cleaning filter, the flow restrictor configured to cause fresh dialysis fluid delivered from the fresh dialysis fluid compartment, through the fresh dialysis fluid line, to the blood cleaning filter to be pressurized so that a first amount of the fresh dialysis fluid performs convective clearance and a second amount of the fresh dialysis fluid performs diffusive clearance.

2. The renal failure therapy machine of claim 1 , which operates the flow restrictor to cause the fresh dialysis fluid to be pressurized so that ten percent to seventy percent of the fresh dialysis fluid performs convective clearance and at least a substantial amount of remaining fresh dialysis fluid performs diffusive clearance.

3. The renal failure therapy machine of claim 1 , which includes a used dialysis fluid pump in fluid communication with the used dialysis fluid compartment and the blood cleaning filter, wherein used dialysis fluid pumped from the used dialysis fluid pump to the used dialysis fluid compartment causes the fresh dialysis fluid to be delivered from the fresh dialysis fluid compartment to the blood cleaning filter.

4. The renal failure therapy machine of claim 1 , wherein the flow restrictor is pneumatically actuated.

5. The renal failure therapy machine of claim 1 , wherein the flow restrictor includes a backpressure regulator.

6. The renal failure therapy machine of claim 1 , wherein the flow restrictor includes a variable orifice valve.

7. The renal failure therapy machine of claim 1 , wherein the flow restrictor is configured to vary a percentage of the fresh dialysis fluid used for convective versus diffusive clearance during treatment.

8. The renal failure therapy machine of claim 1 , wherein the blood cleaning filter includes a venous filter and an arterial filter, and wherein the flow restrictor is located between the venous filter and the arterial filter.

9. A renal failure therapy machine comprising:

a blood circuit including a blood cleaning filter;

a dialysis fluid circuit including a balance chamber, the balance chamber including a fresh dialysis fluid compartment configured to send fresh dialysis fluid to the blood cleaning filter and a used dialysis fluid compartment configured to receive used dialysis fluid from the blood cleaning filter;

a valve located along a fresh dialysis fluid pathway placing the fresh dialysis fluid compartment of the balance chamber into fluid communication with the blood cleaning filter, the valve enabling fresh dialysis fluid to flow selectively from the fresh dialysis fluid compartment of the balance chamber to the blood cleaning filter; and

a flow restrictor in fluid communication with the blood cleaning filter, the flow restrictor configured to cause fresh dialysis fluid pumped past the valve to the blood cleaning filter to be pressurized so that a first amount of the fresh dialysis fluid performs convective clearance and a second amount of the fresh dialysis fluid performs diffusive clearance.

10. The renal failure therapy machine of claim 9 , wherein the flow restrictor includes a variable pneumatic valve.

11. The renal failure therapy machine of claim 9 , wherein the flow restrictor includes a backpressure regulator.

12. The renal failure therapy machine of claim 9 , wherein the flow restrictor includes a variable orifice valve.

13. The renal failure therapy machine of claim 9 , which includes a disposable cassette, the disposable cassette including at least a portion of the dialysis fluid circuit.

14. The renal failure therapy machine of claim 9 , which includes a disposable cassette, the disposable cassette including at least a portion of the blood circuit.

15. The renal failure therapy machine of claim 9 , wherein the valve is a first valve and which includes a second valve located along a used dialysis fluid pathway placing the used dialysis fluid compartment in selective communication with the blood cleaning filter.

16. A renal failure therapy method comprising:

delivering fresh dialysis fluid from a fresh dialysis fluid compartment of a balance chamber to a blood cleaning filter;

pumping used dialysis fluid from the blood cleaning filter to a used dialysis fluid compartment of the balance chamber;

restricting flow to cause a first amount of fresh dialysis fluid to be pressed through a membrane of the blood cleaning filter into an extracorporeal circuit so that the first amount of the fresh dialysis fluid performs convective clearance; and

using a second amount of the fresh dialysis fluid to cause the blood cleaning filter to perform diffusive clearance.

17. The renal failure therapy method of claim 16 , which includes pneumatically restricting flow to cause the fresh dialysis fluid to be pressed through the membrane.

18. The renal failure therapy method of claim 16 , the blood cleaning filter including a venous filter and an arterial filter, wherein restricting flow includes flowing the fresh dialysis fluid through a restriction placed between the venous filter and the arterial filter.

19. The renal failure therapy method of claim 16 , wherein pumping the used dialysis fluid causes the delivery of the fresh dialysis fluid from the fresh dialysis fluid compartment of the balance chamber to the blood cleaning filter.

20. The renal failure therapy method of claim 16 , which includes causing a second percentage of dialysis fluid performing convective clearance in a second treatment to be different from a first percentage in a first treatment.