Method for conductivity calculation in a treatment fluid upstream and downstream a filtration unit in apparatuses for the blood treatment

摘要

A method for conductivity calculation in a treatment fluid downstream a filtration unit in a blood treatment apparatus is provided. The conductivity calculation is then used for clearance and fistula flow determination. A flow of treatment fluid is created in the filtration unit; a change in the conductivity of the treatment fluid at the inlet of the filtration unit is imposed to cause an induced conductivity change in the fluid at the outlet of the filtration unit; a predetermined number of conductivity values Cdo downstream from the filtration unit are measured. The measured conductivity values define a curve the pattern of which is estimated by means of one interpolating mathematical function in an interval of time after the occurrence of the induced conductivity change; a characteristic measuring time tcalcclr is determined. The value of the interpolating mathematical function at the characteristic measuring time tcalcclr represents the conductivity value Cdo2 of the treatment fluid downstream from the filtration unit after the induced conductivity change.