Patent ID: 8029454

Claim:
A medical fluid therapy system comprising: a blood line configured and arranged to be coupled to a patient; a blood pump connected to the blood line; a blood filter in communication with the blood line, the filter operable to allow a liquid portion of a patient's blood to pass from the filter to a therapy fluid flow path; a pair of peristaltic fluid pumps positioned and arranged to pump therapy fluid to one of the blood filter and the blood line and from the blood filter; and at least one balance tube, including a tube and a separator mechanically free from first and second fluidly sealed closed ends of the balance tube, the separator fitted tightly and moveably back and forth between end-of-stroke positions within the tube for volumetric control that assumes a constant volume is maintained collectively between (i) the first closed end and the separator and (ii) the separator and the second closed end, regardless of an orientation of the balance tube, or tortuous path volume control device, the balance tube or tortuous path volume control device in fluid communication with the pair of peristaltic pumps and operable to control an amount of therapy fluid that is pumped to the blood filter or the blood line and an amount of the fluid that is pumped from the filter.