Abstract: An improved chemical treatment system for hemodialysis machines, which includes a first three way valve which has a normally open position in the dialysis and rinsing modes of the hemodialysis machine. The valve in the normally open position couples a source of water through the valve to the bicarbonate pump for rinsing purposes before and after dialysis and the chemical treatment modes of the hemodialysis machine. In the chemical treatment mode of the hemodialysis machine the valve is switched to couple a source of treatment chemical through the valve to the bicarbonate pump. The chemical treatment system includes a second valve, which if in the normally open position, then only the bicarbonate portion and associated downstream portions will be chemically treated. In the closed position, the chemical will be switched to also flow through the whole hemodialysis machine from the water inlet to provide for a half or total system chemical treatment cycle.

Abstract: A valveless positive displacement pump including a closed end cylinder having two fluid inlet and outlet ports adjacent the closed end. A piston reciprocably and rotatably driven in the cylinder and including a reduced area portion on one free end which communicates cyclically with the inlet and outlet ports to pump fluid through the positive displacement pump. The piston reduced area is a reduced radius portion to minimize air bubble buildup and to minimize fluid volume at the end of the piston stroke. The piston also has a gland area formed in the piston which cyclically communicates with a pair of ports to clean the piston and cylinder and prevent the buildup of solids. The piston and cylinder can be formed from a hard ceramic material for accuracy and wear resistance. The cylinder is closed by a resilient end cap to relieve pressures caused by piston movement when the inlet and outlet ports are closed.

Abstract: A pressure regulating system for a hemodialysis machine utilizes a deaeration pump and a regulator in a deaeration loop for minimizing pressure and flow transients in a heated water supply. The deaeration loop has the pump, a deaeration pressure regulator, a deaerator, and a back pressure regulator. The pump produces a negative pressure in heated water entering the deaeration pressure regulator to circulate the water in the deaeration loop and to enhance removal of air from the water. The back pressure regulator controls the loop water pressure to a value greater than the incoming water pressure and supplies water to the dialyzer system of the machine isolated from supply water pressure and flow variations.

Abstract: An automated disinfection system for a hemodialysis machine having a proportioning pump includes a manifold block having a check valve for connection to a container of disinfection solution. The manifold block has an outlet connected to the suction line of the pump and an inlet connected to a warm water source via a solenoid valve. A timing and control circuit controls the solenoid valve to produce a water rinse cycle when the solenoid valve is open and a disinfection cycle when the solenoid valve is closed. The check valve closes when positive pressure is present in the manifold block during a rinse cycle and opens to admit solution to the pump when negative pressure is present in the manifold block during a disinfection cycle.

Abstract: A transmembrane pressure regulator especially useful in artificial kidney systems. The regulator will maintain a pre-selected dialysate pressure at a substantially constant value despite changes in dialysate flow. The regulator of the invention will adjust dialysate pressure in response to changes in a patient's venous blood pressure so as to maintain a transmembrane pressure substantially constant at a preselected value.

Abstract: A system continuously prepares dialysate by mixing water under pressure with concentrate to form dialysate under pressure. This dialysate is supplied on demand to a single patient station or to a plurality of patient stations. The pressure at which this dialysate is supplied to multiple patient stations is controlled so changes in the flow to one station will not change the pressure at which dialysate is supplied to other stations. A pressure regulator senses the pressure of the dialysate supplied to the patient stations and controls a regulator valve connected between the source of water under pressure and a proportioning pump which mixes this water with concentrate. The regulator includes a constant force spring assembly which provides a constant bias against the pressure in a sensing chamber over a range of linear movement of the pressure sensing element.