Patent ID: 8858787

Claim:
A dialysis system comprising: a dialyzer; a blood pump coupled operably to the dialyzer; a dialysate inlet pump coupled operably to a dialysate inlet of the dialyzer; a dialysate outlet pump coupled operably to a dialysate outlet of the dialyzer; a first non-invasive fluid velocity sensor positioned to sense an inlet velocity of dialysate pumped to the dialyzer inlet by the dialysate inlet pump; a second non-invasive fluid velocity sensor positioned to sense an outlet velocity of dialysate pumped from the dialyzer outlet by the dialysate outlet pump; and a logic implementor programmed to: (i) set a speed of the dialysate inlet pump and a speed of the dialysate outlet pump so that an ultrafiltration rate is achieved, (ii) multiply a cross-sectional area of the dialyzer inlet by the sensed fluid inlet velocity and by a sample time to determine a sample time inlet volume, (iii) multiply a cross-sectional area of the dialyzer outlet by the sensed fluid outlet velocity and by the sample time to determine a sample time outlet volume, (iv) integrate the determined sample time inlet and outlet volumes over a treatment period to determine a total amount of dialysate delivered to and from the dialyzer during the treatment, and (v) use the determined total amount of dialysate delivered to and from the dialyzer to adjust the ultrafiltration rate as treatment proceeds.