Patent ID: 7850856

Claim:
A method for monitoring the supply of a substitution fluid during an extracorporeal blood treatment, said method comprising: providing an extracorporeal blood circuit comprising: a first chamber of a dialyser, wherein the dialyser is subdivided by a semipermeable membrane into the first chamber and a second chamber; providing a fluid system comprising: the second chamber of the dialyser, a substitution fluid line connecting to the extracorporeal blood circuit upstream or downstream of the dialyser, a substituate pump on the substitution fluid line to deliver the substitution fluid from the fluid system to the extracorporeal blood circuit upstream or downstream of the dialyser, and a pressure sensor in the fluid system for measuring pressure waves generated by the substituate pump in the upstream direction of the substitution fluid line; generating a plurality of pressure waves with the substituate pump; measuring the pressure waves in the fluid system with the pressure sensor; converting the measured pressure waves into an electrical signal having an amplitude; comparing the amplitude to a preset limiting value; and determining there is an interruption of the supply of the substitution fluid when the amplitude of the pressure waves exceeds the preset limiting value.