Patent ID: 8357298

Claim:
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.