Patent ID: 8764987

Claim:
An apparatus for the determination and regulation of the concentration of at least one dissolved substance in a fluid circuit, the fluid circuit including an extracorporeal blood circuit and a dialysate circuit having at least one filter which separates the extracorporeal blood circuit and the dialysate circuit in a semipermeable manner, said apparatus comprising: a detection unit having at least a first determining element with which a concentration difference of at least one first dissolved substance can be determined indirectly and/or directly by the detection unit before and after the filter in the dialysate circuit; a determination unit which determines an influence of at least one second dissolved substance, which is not identical to the at least one first dissolved substance, on the first determining element of the detection unit while using a model and calculates the concentration difference of the at least one first dissolved substance before and after the filter in the dialysate circuit; and a regulation unit for regulating the concentration of the at least one dissolved substance in the fluid circuit, the regulation unit including a regulation element and a storage element, with an actual value of the determined concentration difference of the at least one first dissolved substance in the dialysate circuit being calibrated by the regulation element with respect to a desired value for the concentration or for a concentration change of the at least one first dissolved substance in the extracorporeal blood circuit or in a vascular blood circuit, and the concentration of the at least one first dissolved substance in the dialysate circuit being regulated to a desired value via the regulation element, or with a desired value for the concentration of the at least one first dissolved substance in the dialysate circuit upstream of the filter being determined by the regulation element from the actual value of the determined concentration difference of the at least one first substance in the dialysate circuit before and after the filter, and the concentration of the at least one first dissolved substance in the dialysate circuit upstream of the filter being regulated to the desired value via the regulation unit.