Hemodialysis systems and methods

A method of using a hemodialysis system, the hemodialysis system comprising:

• a blood flow path;
• a dialysate flow path;
• a blood pump fluidically connected to the blood flow path and configured to draw blood from a patient and pump the blood through a dialyzer comprising a blood side fluidically connected to the blood flow path and a dialysate side fluidically connected to the dialysate flow path, wherein the blood side is separated from the dialysate side by a dialyzer membrane;
• the dialysate flow path comprising:
• a balancing circuit which controls the amount of dialysate passing through the dialyzer,
• a mixing circuit which forms dialysate from constituents including water, and
• a directing circuit which passes water from a water supply to the mixing circuit and passes dialysate from the mixing circuit to the balancing circuit;
• and
• a reciprocating membrane based dialysate pump forming part of the balancing circuit and fluidically connected to the dialysate flow path, the dialysate pump being configured to pump dialysate through the dialyzer;
• the method comprising steps of:
• measuring a blood-side related pressure indicative of a pressure of blood in the blood side of the dialyzer;
• measuring a dialysate-side related pressure indicative of a pressure of dialysate in the dialysate side of the dialyzer;
• and
• operating the dialysate pump to pass dialysate through the dialyzer and to cause fluid to flow across the dialyzer membrane into the blood flow path when the measured blood-side related pressure is less than the measured dialysate-side related pressure and fluid to flow from the blood flow path across the dialyzer membrane into the dialysate flow path when the measured blood-side related pressure is greater than the measured dialysate-side related pressure.