Patent ID: 8182691

Claim:
An apparatus for extracorporeal blood treatment comprising: a dialysis fluid preparation device for preparing fresh dialysis fluid, adapted to change at least one of a chemical and a physical property of the dialysis fluid; a filter divided into a first filter chamber and a second filter chamber by a membrane for filtering microorganisms, the filter located downstream from the dialysis fluid preparation device; a measuring device for measuring a change in the at least one of the chemical and physical property of the dialysis fluid, the measuring device located downstream from the filter; a dialyzer divided by a semi-permeable membrane into a first dialyzer chamber and a second dialyzer chamber, the first dialyzer chamber being arranged in a dialysis fluid circuit and the second dialyzer chamber being arranged in a blood circuit, the dialyzer located downstream from the filter; and a computing unit configured to: determine at least one reference value representative of a filter being present; determine a first time t 0 at which the dialysis fluid preparation device changes the at least one of the chemical and physical property of the dialysis fluid; determine a second time t 1 at which the measuring device detects the change in the at least one of the chemical and physical property of the dialysis fluid; determine a time interval Δt by subtracting the first time t 0 from the second time t 1 ; compare the time interval Δt, or a parameter correlating to the time interval Δt, to the reference value; and determine that a filter is present if the time interval, or a parameter correlating to the time interval, matches the at least one reference value, or determine that a filter is not present if the time interval, or a parameter correlating to the time interval, does not match the at least one reference value.