Hemodialysis systems and methods
The present invention generally relates to hemodialysis and similar dialysis systems, including a variety of systems and methods that would make hemodialysis more efficient, easier, and/or more affordable. One aspect of the invention is generally directed to new fluid circuits for fluid flow. In one set of embodiments, a hemodialysis system may include a blood flow path and a dialysate flow path, where the dialysate flow path includes one or more of a balancing circuit, a mixing circuit, and/or a directing circuit. Preparation of dialysate by the preparation circuit, in some instances, may be decoupled from patient dialysis. In some cases, the circuits are defined, at least partially, within one or more cassettes, optionally interconnected with conduits, pumps, or the like. In one embodiment, the fluid circuit and/or the various fluid flow paths may be at least partially isolated, spatially and/or thermally, from electrical components of the hemodialysis system. In some cases, a gas supply may be provided in fluid communication with the dialysate flow path and/or the dialyzer that, when activated, is able to urge dialysate to pass through the dialyzer and urge blood in the blood flow path back to the patient. Such a system may be useful, for example, in certain emergency situations (e.g., a power failure) where it is desirable to return as much blood to the patient as possible. The hemodialysis system may also include, in another aspect of the invention, one or more fluid handling devices, such as pumps, valves, mixers, or the like, which can be actuated using a control fluid, such as air. In some cases, the control fluid may be delivered to the fluid handling devices using an external pump or other device, which may be detachable in certain instances. In one embodiment, one or more of the fluid handling devices may be generally rigid (e.g., having a spheroid shape), optionally with a diaphragm contained within the device, dividing it into first and second compartments.
1. A hemodialysis system, comprising:
a blood path through which blood is drawn from a patient and passed through a dialyzer; the blood path comprising a pump cassette that includes:
a pneumatically actuated diaphragm-based blood flow pump capable of pumping fluid through the dialyzer; and
an air vent in fluid communication with the blood flow pump;
a dialysate path comprising:
the dialyzer;
a first pneumatic actuated diaphragm-based dialysate pump being in valved connection with the dialyzer and a liquid supply; and
a controller for controlling pneumatic actuation pressure delivered to the blood flow pump, the first dialysate pump, one or more blood-path valves and one or more dialysate-path valves, wherein the controller is configured to prime the dialyzer and blood path with liquid, the blood flow pump to pump air from the air vent through the blood path to the dialyzer to push the liquid in the blood path through a membrane of the dialyzer, wherein the controller is configured to detect a rupture of the membrane of the dialyzer when air flow through the dialyzer from the blood flow pump continues after all of the liquid on a blood path side of the dialyzer has been displaced.
2. The hemodialysis system of claim 1 , wherein the air vent includes a filter.
3. The hemodialysis system of claim 1 , wherein the controller is configured to cycle a pneumatic valve to vary the pressure delivered to the blood flow pump and determine a flow rate and an end of stroke based on a signal from a pressure sensor in fluid connection to blood flow pump.
4. The hemodialysis system of claim 1 , wherein the controller is configured to fill the blood flow pump with liquid from the liquid supply, deliver the liquid in the blood flow pump to prime the dialyzer, fill the blood flow pump with air, and pump the air to the dialyzer, wherein the controller is configured to detect a ruptured membrane of the dialyzer when the flow does not stop once the liquid in the blood path side of the dialyzer has been displaced by the air.
5. The hemodialysis system of claim 1 , further comprising a second pneumatic actuated diaphragm-based dialysate pump in fluid communication with the dialyzer, the dialysate path being configured to fluidically connect the second dialysate pump to atmosphere, wherein the controller is configured to empty the second dialysate pump of liquid and fluidically connect the second dialysate pump to atmosphere before the blood flow pump pumps the air to the dialyzer.
6. The hemodialysis system of claim 1 , wherein the blood flow pump comprises a pneumatic actuation chamber separated from a pumping chamber by a flexible diaphragm, the pneumatic actuation chamber in fluidic communication with a pressure sensor, and wherein pressure data from the pressure sensor is monitored by the controller.
7. The hemodialysis system of claim 1 , wherein the controller is configured to control the blood flow pump to pump air by pulling the air from the air vent through a medication pump.
8. The hemodialysis system of claim 7 , wherein the controller is configured to control the blood flow pump to pull the air past a first valve positioned between the air vent and the medication pump and a second valve positioned between the medication pump and the blood flow pump.