Automated control mechanisms in a hemodialysis apparatus

A system for controlling fluid flow in a hemodialysis apparatus comprising:

• a dialysate pump constructed and arranged to receive a fluid from a dialysate outlet of a dialyzer;
• a blood pump comprising a reciprocating diaphragm constructed and arranged to deliver blood from an extracorporeal blood circuit to a blood inlet of the dialyzer, a pumping chamber of the blood pump separated from a control chamber of the blood pump by a flexible diaphragm, the control chamber constructed and arranged to contain a control fluid at a positive or a negative pressure to operate the diaphragm;
• a pressure sensor constructed and arranged to measure a pressure of the control fluid contained in the control chamber of the blood pump;
• a controller adapted and programmed to receive information from the pressure sensor, and programmed to operate a valve connecting a source of the control fluid to the control chamber of the blood pump;
• wherein the controller is adapted and programmed to control the valve to generate a time-varying pressure waveform of the control fluid in the control chamber during a fill-stroke of the blood pump and to monitor a resulting pressure variation in the control chamber, and
• wherein the controller is adapted and programmed to initiate a procedure to pause or stop the dialysate pump if a magnitude of the measured pressure variation deviates from a pre-determined value, the procedure comprising alerting a user of a fault condition and waiting a pre-determined time period for a user response to correct the fault condition before pausing or stopping the dialysate pump.