Dialysis machine

1. A hemodialysis machine comprising:

a dialysate flow path for delivering a flow of dialysate solution through a dialyser, the flow path including:

a flow balancer for achieving a balance in the dialysate solution flow volume observed between an inlet and an outlet of the dialyser over the course of a treatment, the flow balancer comprising a first flow balance pump having an inlet valve and an outlet valve and a second flow balance pump having an inlet valve and an outlet valve, wherein each of the inlet valves and outlet valves is opened and closed by a flexible film which is pneumatically actuated such that the inlet valve and the outlet valves are compliant structures;

wherein the dialysate flow path further includes a flow restrictor downstream of the flow balance pumps to reduce the pressure difference across the valves in the dialysate flow path and, consequently, a variance in positions of those compliant structures, the flow restrictor being a section of the flow path having reduced diameter tubing; and

wherein the machine includes a disposable cartridge, the cartridge defining the dialysate flow path.

2. The machine according to claim 1 wherein the pumps are switchable between two modes of operation, a first mode of operation in which the first flow balance pump is arranged in the dialysate line upstream of said dialyser and the second flow balance pump is arranged in the dialysate line downstream of said dialyser, and a second mode of operation in which the second flow balance pump is arranged in the dialysate line upstream of said dialyser and the first flow balance pump is arranged in the dialysate line downstream of said dialyser.

3. A hemodialysis machine comprising:

a dialysate flow path for delivering a flow of dialysate solution through a dialyser, the flow path including:

a flow balancer for achieving a balance in the dialysate solution flow volume observed between an inlet and an outlet of the dialyser over the course of a treatment, the flow balancer comprising a first flow balance pump having an inlet valve and an outlet valve and a second flow balance pump having an inlet valve and an outlet valve;

wherein each of the valves is covered by a pneumatically operable membrane for operating the valve, the valves being substantially geometrically identical to one another;

wherein a physical positioning of the first and second flow balance pumps and the inlet and outlet valves is mirrored about a centreline;

wherein the dialysate flow path includes a flow restrictor downstream of the flow balance pumps, and the flow restrictor is a section of the flow path having a reduced diameter; and

wherein the pumps are switchable between two modes of operation, a first mode of operation in which the first flow balance pump is arranged in the dialysate line upstream of said dialyser and the second flow balance pump is arranged in the dialysate line downstream of said dialyser, and a second mode of operation in which the second flow balance pump is arranged in the dialysate line upstream of said dialyser and the first flow balance pump is arranged in the dialysate line downstream of said dialyser.

4. The machine according to claim 3 wherein each of the valves has an inner upstanding wall within an outer upstanding wall and which stands lower than the outer upstanding wall.

5. The machine according to claim 3 wherein the machine includes a disposable cartridge, the cartridge defining the dialysate flow path.

6. A hemodialysis machine comprising:

a dialysate flow path for delivering a flow of dialysate solution through a dialyser wherein the flow path includes:

a pump for pumping dialysate solution, the pump having a pump chamber defining a fluid access port, the fluid access port being in fluid communication with an inlet valve and an outlet valve;

wherein the fluid access port is a combined inlet/outlet to the pump chamber;

wherein the fluid access port is defined by one central aperture surrounded by four outer apertures, concentric with the central aperture, through which the dialysate solution enters or exits the pump chamber;

wherein the pump chamber is configured such that, during a portion of an outlet stroke of the pump, the four outer apertures are covered leaving only the central aperture able to permit fluid to exit the pump chamber so as to reduce pressure downstream at an end of the outlet stroke; and

wherein the machine includes a disposable cartridge, the cartridge defining the dialysate flow path.

7. The machine according to claim 1 , wherein a physical positioning of the first and second flow balance pumps and the inlet and outlet valves is mirrored about a centreline of the cartridge.

8. The machine according to claim 1 , wherein the disposable cartridge comprises a rigid body covered by the flexible film so as to define the dialysate flow path.

9. The machine according to claim 8 , wherein the first and second flow balance pumps are actuated by pneumatically actuating the flexible film.

10. The machine according to claim 5 , where in the disposable cartridge comprises a rigid body covered by a flexible film so as to define the flow path, the flexible film comprising the pneumatically operable membrane.

11. The machine according to claim 10 , wherein the first and second flow balance pumps are actuated by pneumatically actuating the flexible film.

12. The machine according to claim 6 , wherein the disposable cartridge comprises a rigid body covered by a flexible film so as to define the flow path.

13. The machine according to claim 12 , wherein the pump is actuated by pneumatically actuating the flexible film.

14. The machine according to claim 6 , wherein the dialysate flow path includes a flow restrictor downstream of the pump and of the dialyser, and the flow restrictor is a section of the flow path having a reduced diameter.