Patent ID: 8858486

Claim:
An arrangement for determining recirculation (R A ) in a fistula and/or the cardio-pulmonary proportion of recirculation (R CP ), for a blood-treating apparatus in which the blood to be treated flows in an extra-corporeal blood circuit through a blood chamber of a dialyzer which is divided into the blood chamber and a dialysis-fluid chamber by a semi-permeable membrane and dialysis fluid flows through the dialysis-fluid chamber of the dialyzer on a path for dialysis fluid, a blood pump being arranged in the extra-corporeal blood circuit, the arrangement comprising: a control unit configured to control first and second changes in a physical or chemical parameter in the blood, wherein the control unit is configured to set first and second blood flow rates to values such that fistula recirculation (R A ) occurs at a value of the first blood flow rate but does not occur at a value of the second blood flow rate; a sensor configured to a) measure, in the blood, the first change in the physical or chemical parameter at the first blood flow rate (Q BH ), and b) measure, in the blood, the second change in the physical or chemical parameter at the second blood flow rate (Q BL ), the first and second blood flow rates being different from one another; and a computing and analyzing unit configured to determine the fistular recirculation (R A ) and/or the cardio-pulmonary proportion of recirculation (R CP ) on the basis of the physical or chemical parameter that is measured at the first and second blood flow rates (Q BH , Q BL ).