Pumping cassette

A disposable cassette configured for operative association with a base unit of a dialysis apparatus to replace a volume of a spent dialysate from a dialyzer with a substantially equal volume of a fresh dialysate, the disposable cassette comprising:

• a fresh dialysate flow network and a spent dialysate flow network, the fresh dialysate flow network comprising an inlet port and an outlet port for the fresh dialysate, and the spent dialysate flow network comprising an inlet port and an outlet port for the spent dialysate;
• a first balancing pod and a second balancing pod, each balancing pod separated into a first chamber and a second chamber by a flexible membrane configured to provide a seal between the first chamber and the second chamber, wherein the first chamber is in fluid communication with the fresh dialysate flow network and the second chamber is in fluid communication with the spent dialysate flow network;
• the first chamber of each of the first and second balancing pods having at least one first chamber balancing pod port for ingress and/or egress of the fresh dialysate, each at least one first chamber balancing pod port in fluid communication with a valve to permit fluid flow between the first chamber and the inlet port of the fresh dialysate flow network, and in fluid communication with a valve to permit fluid flow between the first chamber and the outlet port of the fresh dialysate flow network, and;
• the second chamber of each of the first and second balancing pods having at least one second chamber balancing pod port for ingress and/or egress of the spent dialysate, each at least one second chamber balancing pod port in fluid communication with a valve to permit fluid flow between the second chamber and the inlet port of the spent dialysate flow network, and in fluid communication with a valve to permit fluid flow between the second chamber and the outlet port of the spent dialysate flow network;
• and
• a first reciprocating positive displacement membrane pump and a second reciprocating positive displacement membrane pump, both in fluid communication with the spent dialysate flow network,
• the first reciprocating positive displacement membrane pump having a pump inlet in fluid communication through a valve with the inlet port of the spent dialysate flow network, and a pump outlet in fluid communication with the at least one second chamber balancing pod port of the first balancing pod;
• the second reciprocating positive displacement membrane pump having a pump inlet in fluid communication through a valve with the inlet port of the spent dialysate flow network, and a pump outlet in fluid communication with the at least one second chamber balancing pod port of the second balancing pod;
• wherein
• the disposable cassette can be operated by the base unit so that
• a first volume of the spent dialysate can be drawn through the inlet port of the spent dialysate flow network by the first reciprocating positive displacement membrane pump, stored in the first reciprocating positive displacement membrane pump, and pumped to the second chamber of the first balancing pod to displace the flexible membrane of the first balancing pod and move a first volume of fresh dialysate out of the first chamber of the first balancing pod to exit the cassette through the outlet port of the fresh dialysate flow network, and
• a second volume of the spent dialysate can be drawn through the inlet port of the spent dialysate flow network by the second reciprocating positive displacement membrane pump, stored in the second reciprocating positive displacement membrane pump, and pumped to the secons chamber of the second balancing pod to displace the flexible membrane of the second balancing pod and move a second volume of fresh dialysate out of the first chamber of the second balancing pod to exit the cassette through the outlet port of the fresh dialysate flow network.