Patent ID: 7896831

Claim:
A method of estimating fluid flow rate (Qa) in a fluid flow access, comprising: in a normal position, removing a first fluid flow from said access at a removal position to an external flow circuit comprising a dialyzer having a semipermeable membrane, said first fluid flow passing along said membrane at one side thereof and a dialysis fluid being emitted from the other side thereof, and returning said first fluid flow from said external flow circuit to said access at a return position downstream of said removal position; measuring a first conductivity of the dialysis fluid emitted from the dialyzer in said normal position; in a reversed position wherein the removal position and the return position are reversed, removing a second fluid flow and measuring a second conductivity of the dialysis fluid emitted from the dialyzer in said reversed position; and calculating the fluid flow rate (Qa) in said flow access utilizing said measured first and second conductivities.