Patent ID: 7500958

Claim:
An extracorporeal circuit for use with blood flow from a blood access comprising: a switch valve comprising: a valve housing defining a chamber, four openings communicating with the chamber wherein each opening has a peripheral width; and a connector for each of said openings, said connectors including: a first blood inlet connector, a second blood outlet connector, a circuit inlet connector, and a circuit outlet connector; a dialyzer having a blood compartment and a dialysis fluid compartment separated by a semi-permeable membrane, wherein the blood compartment comprises: an inlet connected to the circuit outlet connector; and an outlet connected to the circuit inlet connector; a first line connected to the first blood inlet connector; an arterial needle connected to the first line and for connection to the blood access; a second line connected to the second blood outlet connector; a venous needle connected to the second line and for connection to the blood access; the dialysis fluid compartment comprises: an inlet for connection to a source of dialysis fluid, and an outlet; a dialysate line connected to the outlet of the dialysate compartment; the switch valve comprising: a pivotable valve member located in the valve chamber and pivotable therein to change the direction of blood flow among the openings from a normal condition to a reversed condition, said pivotable valve member having a blood-impervious partition which is rotatable with said valve member, said pivotable valve member being arranged to adopt an idle position in which all four openings are interconnected, said partition in said normal condition extending across the entire inside diameter of said valve chamber and thereby sealing a pathway between said first blood inlet connector and said circuit outlet connector, said partition being constructed of a width that is less than the peripheral width of each opening; a monitor connected to the dialysate line for measuring, in the normal condition of blood flow, a first variable in the dialysate, and for measuring, in the reversed condition of blood flow, a second variable in the dialysate; a calculating means for calculating a blood flow rate in the blood access from the first and second variables, wherein the openings are disposed on the valve housing diametrically opposite to each other, the valve chamber is cylindrical and the openings are spaced 90° relative to each other around the chamber, the openings are each provided with a respective connector, said partition divides the valve chamber in two portions, and each of said portions is semi-circular, and wherein a first and a second of said connectors extend diametrically opposite from the valve housing and a third and a fourth of said connectors are symmetrically inclined by less than 90 degrees with respect to a direction of the first connector.