Method and apparatus for calculating fluid flow rate
First Claim
1. 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.
4 Assignments
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Accused Products
Abstract
A switch valve for use in an extracorporeal blood flow circuit comprises a valve housing having a chamber, four openings communicating with the chamber, and a valve member located in the valve chamber. A first opening is to be connected to a patient via an arterial cannula, a second opening is to be connected to a patient via an venous cannula, a third opening is to be connected to a first inlet/outlet of a blood treatment device, and a fourth opening is to be connected to a second inlet/outlet of a blood treatment device. The valve member is movable within the valve housing to fluidly connect the first opening to either the third or the fourth opening and to fluidly connect the second opening to either the third or the fourth opening. The width of the valve member is smaller than a peripheral dimension of the openings.
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Citations
11 Claims
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1. A method of estimating fluid flow rate (Qa) in a fluid flow access, comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus for extracorporeal blood treatment comprising:
- a dialyzer having first and second compartments separated by a semi-permeable membrane;
a blood circuit having;
a blood removal line for connecting, in a normal condition, an inlet of the first compartment to a blood access of a patient at a first connecting point, and a blood return line for connecting, in the normal condition, an outlet of the first compartment to the blood access of the patient at a second connecting point;
a reversal means for switching the connection of the blood removal line and the blood return line to the blood access so that, in a reverse condition, the first connecting point is in fluid communication with the outlet of the first compartment and the second connecting point is in fluid communication with the inlet of the first compartment;
a dialysis liquid circuit having;
a dialysis liquid line for supplying a dialysis liquid to an inlet of the second compartment, and a dialysate line for draining a dialysate from an outlet of the second compartment;
a sensor connected to the dialysate line for measuring, in the normal condition, a first conductivity of the dialysate, and for measuring, in the reverse condition, a second conductivity of the dialysate;
a calculating means for calculating a fluid flow rate (Qa) in the blood access from the first and second conductivities and from a clearance of the dialyzer. - View Dependent Claims (8, 9, 10, 11)
- a dialyzer having first and second compartments separated by a semi-permeable membrane;
Specification