Patent ID: 8679054

Claim:
A peritoneal dialysis method comprising: applying a vacuum from a negative pressure source communicating pneumatically with a vacuum chamber to a portion of a flexible membrane of a dialysis fluid carrying pumping cassette aligned with the vacuum chamber; turning a stepper motor shaft a controlled amount to correspondingly move a piston head and the portion of the flexible membrane into the pumping cassette, so as to push fresh dialysis fluid out of the disposable cassette through a patient line connected to a patient connector or spent dialysis fluid out through a drain line; and turning the stepper motor shaft in an opposite direction a controlled amount to correspondingly retract the piston head from the portion of the flexible membrane of the pumping cassette membrane, the vacuum causing the flexible membrane to follow the piston head as the piston head is retracted, so as to draw fresh dialysis fluid into the pumping cassette through a fill line connected to a dialysate source or spent dialysis fluid into the pumping cassette through the patient line.