Method for determining a patient's blood sodium level and artificial kidney for the application thereof
First Claim
1. A method for determining the blood sodium level of a patient whose blood circulates through a first compartment of an exchanger of an artificial kidney, said first compartment being separated from a second compartment of the exchanger by a semipermeable membrane for permitting dialysis and ultrafiltration of the blood, said second compartment being disposed in a dialysis fluid circuit through which dialysis fluid passes, comprising the steps of:
- changing, in a selected manner, the conductivity of the dialysis fluid flowing into the second compartment of the exchanger;
measuring, in response to the step of changing the conductivity of the dialysis fluid, the change in conductivity of the dialysis fluid flowing out of the second compartment of the exchanger;
determining a lag time tL between the change in conductivity of the dialysis fluid flowing into the second compartment of the exchanger and the corrresponding measured change in conductivity of dialysis fluid flowing out of the second compartment of the exchanger;
determining an equilibrium conductivity value of the dialysis fluid in the second compartment of the exchanger for which the conductivity of the dialysis fluid at outflow from the second compartment at a time t is substantially equal to the conductivity of the dialysis fluid at inflow into the second compartment at a time t'"'"'=t-tL ; and
determining the sodium concentration in the patient'"'"'s blood in accordance with the determined equilibrium conductivity value.
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Accused Products
Abstract
A method for determining the blood sodium level of a patient whose blood circulates through one compartment of an exchanger separated from a dialysis fluid by a semipermeable membrane, wherein the conductivity of the dialysis fluid of equilibrium with the plasma is determined by: changing in a selected manner the conductivity of the dialysis fluid at inflow the exchanger, measuring the conductivity of the dialysis fluid at outflow from the exchanger, determining a lag time tL of the change in conductivity of dialysis fluid between inflow to and outflow from the exchanger, and determining an equilibrium conductivity value of the dialysis fluid for which the conductivity at outflow from the exchanger at an instant t is equal to the conductivity at inflow at an instant t-tL. The invention also relates to an artificial kidney incorporating means for carrying out this method.
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Citations
15 Claims
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1. A method for determining the blood sodium level of a patient whose blood circulates through a first compartment of an exchanger of an artificial kidney, said first compartment being separated from a second compartment of the exchanger by a semipermeable membrane for permitting dialysis and ultrafiltration of the blood, said second compartment being disposed in a dialysis fluid circuit through which dialysis fluid passes, comprising the steps of:
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changing, in a selected manner, the conductivity of the dialysis fluid flowing into the second compartment of the exchanger; measuring, in response to the step of changing the conductivity of the dialysis fluid, the change in conductivity of the dialysis fluid flowing out of the second compartment of the exchanger; determining a lag time tL between the change in conductivity of the dialysis fluid flowing into the second compartment of the exchanger and the corrresponding measured change in conductivity of dialysis fluid flowing out of the second compartment of the exchanger; determining an equilibrium conductivity value of the dialysis fluid in the second compartment of the exchanger for which the conductivity of the dialysis fluid at outflow from the second compartment at a time t is substantially equal to the conductivity of the dialysis fluid at inflow into the second compartment at a time t'"'"'=t-tL ; and determining the sodium concentration in the patient'"'"'s blood in accordance with the determined equilibrium conductivity value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for determining the blood sodium level of a patient'"'"'s blood circulating through a first compartment of an exchanger of an artificial kidney, said exchanger including a semipermeable membrane separating the first compartment from a second compartment of the exchanger through which dialysis fluid in a dialysis fluid circuit passes, said membrane being adapted to permit the dialysis and ultrafiltration of the blood from between the first and second compartments, comprising the steps of:
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selectively changing the conductivity of dialysis fluid flowing into the second compartment of the exchanger; monitoring the conductivity of the dialysis fluid flowing into the second compartment to determine a time to at which the conductivity of the dialysis fluid flowing into the second compartment changes in response to the step of selectively changing the conductivity; monitoring the conductivity of the dialysis fluid flowing out of the second compartment to determine a time tl at which the conductivity of the dialysis fluid flowing out of the second compartment changes in response to the step of selectively changing the conductivity; determining a lag time tL between initialization of the change in conductivity of the dialysis fluid flowing into and out of the second compartment in accordance with the difference between the times t0 and t1 ; determining an equilibrium value between the conductivity of the dialysis fluid in the second compartment and the conductivity of the blood in the first compartment in accordance with the monitored values of conductivity of the dialysis fluid and the lag time tL ; and determining the patient'"'"'s blood sodium level in accordance with the determined equilibrium conductivity value. - View Dependent Claims (10)
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11. An artificial kidney including an exchanger having at least first and second compartments separated by a semipermeable membrane for permitting the dialysis and ultrafiltration of the blood therethrough, said first compartment being disposed in an extracorporeal blood circuit and said second compartment having an inlet and an outlet for flow communicating with a dialysis fluid circuit having dialysis fluid flowing therethrough, comprising:
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means for selectively changing the conductivity of the dialysis fluid flowing into said second compartment through said inlet; means for measuring the conductivity of the dialysis fluid flowing out of said second compartment through said outlet; means for determining a lag time tL between a change in conductivity of the dialysis fluid flowing into said second compartment and a corresponding change in conductivity of the dialysis fluid flowing out of said second compartment; means for determining an equilibrium conductivity value of the dialysis fluid relative to the blood for which value the conductivity of the dialysis fluid at outflow from said second compartment at an instant t is equal to the conductivity of the dialysis fluid at inflow to said second compartment at an instant t'"'"'=t-tL. - View Dependent Claims (12, 13, 14, 15)
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Specification