Patent ID: 8529767

Claim:
A device for determining the share of fistula recirculation (R A ) or the share of cardiopulmonary recirculation (R CP ) in the total recirculation (R) for use with an apparatus for extracorporeal blood treatment, the extracorporeal blood treatment apparatus comprising: a dialyser or filter divided by a membrane into a first chamber and a second chamber, an extracorporeal blood circuit which includes the first chamber, a fluid system which includes the second chamber, a device for supplying blood at a specific blood flow rate Q B into the first chamber of the dialyser or filter, a substitution device for supplying substitution fluid at a specific substitution rate Q S to the extracorporeal blood circuit upstream or downstream of the dialyser or filter; and an ultrafiltration device for withdrawing fluid at a specific flow rate Q FM from the extracorporeal blood circuit via the membrane of the dialyser or filter; the device for determining the share of fistula recirculation (R A ) or the share of cardiopulmonary recirculation (R CP ) in the total recirculation (R) comprising: a control unit for controlling the substitution device and the ultrafiltration device, wherein the control unit is configured such that when substitution rate Q S is changed by a predetermined amount upstream or downstream of the dialyser or filter, the flow rate Q FM of the fluid withdrawn through the membrane is also changed; a unit for determining the blood volume (RBV(t 1 )) and (RBV(t 2 )) or a quantity correlating with the blood volume before and after the change in the substitution rate and the flow rate of the fluid withdrawn through the membrane; a unit for determining the total recirculation (R); and an evaluation unit configured to determine the fistula recirculation (R A ) from the ascertained blood volume or the quantity correlating with the blood volume before and after the change in substitution rate Q S and flow rate Q FM , and configured to determine the share of the fistula recirculation (R A ) or the share of cardiopulmonary recirculation (R CP ) in the total recirculation (R) from the ascertained fistula recirculation (R A ) and the ascertained total recirculation (R).