Method, apparatus and software program for measurement of a parameter relating to a heart-lung system of a mammal

• US 20050148923A1
• Filed: 11/18/2004
• Published: 07/07/2005
• Est. Priority Date: 11/20/2003
• Status: Active Grant

• Current Assignee: Gambro Lundia AB (Baxter International Inc.)
• Original Assignee: Gambro Lundia AB (Baxter International Inc.)
• Inventors: Sternby, Jan Peter
• Granted Patent: US 7,815,852 B2
• Time in Patent Office: Days
• US Class Current: 604/4.10
• CPC Class Codes: A61B 5/0275 using tracers, e.g. dye dilution
• CPC Class Codes: A61B 5/029 Measuring or recording blood output from the heart, e.g. minute volume A61B8/065 takes precedence
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/1609 after use, i.e. downstream of dialyser
• CPC Class Codes: A61M 1/1617 using measurements made during a temporary variation of a characteristic of the fresh dialysis fluid
• CPC Class Codes: A61M 2205/058 with ultrasound therapy
• CPC Class Codes: A61M 2230/65 Impedance, e.g. conductivity, capacity

Abstract

A method, apparatus and software program for measuring a parameter relating to the heart-lung system of a mammal are described. The method, software and apparatus can be implemented in a dialysis or other blood treatment apparatus comprising an extracorporeal blood circuit connected to a mammal; the circuit comprises a dialyzer, or other treatment unit, having a blood inlet, a blood outlet, a treatment fluid inlet and a treatment fluid outlet. The method comprises the steps of providing a pulse of a detectable substance in the blood circuit, measuring an integrated concentration of the detectable substance on the dialysis fluid outlet, determining the parameter based on the measurements on the dialysis fluid outlet.

Claims

1. Method for measuring a parameter relating to the heart-lung system of a mammal connected to a blood treatment equipment, said equipment comprising an extracorporeal blood circuit, which is connected to the mammal, in which blood circuit a blood treatment unit having a blood inlet, a blood outlet, a treatment fluid inlet and a treatment fluid outlet is arranged, characterized in that said method comprises the steps of

providing a detectable perturbation to at least a measurable blood characteristic in the blood circuit,

measuring an integrated change of a corresponding characteristic on the treatment fluid outlet,

determining the parameter relating to the heart-lung system based on the measurement of said integrated change on the treatment fluid outlet.

2. Method according to claim 1, wherein the detectable perturbation to at least a measurable blood characteristic comprises a change in concentration of a detectable substance.

3. Method according to claim 1 or 2, wherein the detectable perturbation is carried out either on the treatment fluid before the treatment fluid inlet or on the blood before the blood inlet or on the blood after the blood outlet.

4. Method according to claim 2, wherein the change in concentration of a detectable substance comprises a pulse of detectable substance provided in the treatment fluid before the treatment fluid inlet.

5. Method according to claim 2, wherein the change in concentration of a detectable substance comprises a pulse of detectable substance provided by insertion of the detectable substance in the blood circuit.

6. Method according to claim 5, wherein the detectable substance is inserted before the blood inlet.

7. Method according to claim 5, wherein the detectable substance is inserted after the blood outlet.

8. Method according to claim 2, wherein the change in concentration of a detectable substance is provided by bypassing the treatment unit for a time period.

9. Method according to claim 1, wherein said parameter relating to the heart-lung system comprises at least one selected in the group comprising:

the cardiac output;

a parameter proportional to the cardiac output;

the heart-lung system volume;

a parameter proportional to the heart-lung system volume.

10. Method according to claim 9, also comprising the steps of:

providing a clearance for the treatment unit, a flow rate on the treatment liquid side and the mass of the detectable substance in said change,

determining an integrated concentration change from a background level of the detectable substance on the treatment fluid output side during a time interval determined by the time when blood, that has passed through the heart of the mammal, passes the treatment unit,

calculating a the heart-lung system parameter based on the integrated concentration change from the background level of the detectable substance on the dialysate side, the flow rate on the dialysate side, the clearance and the mass of the detectable substance in the change.

11. Method according to claim 10, wherein said change is a pulse.

12. Method according to claim 11 wherein the cardiac output CO is calculated using the relationship:

13. Method according to claim 12, wherein the change is carried out upstream the treatment unit, either in the blood circuit or in the treatment liquid, and corresponding first and second concentration pulses appear in the treatment liquid line downstream the treatment unit, said integration of Δ

C_d being done over the length of the second pulse.

14. Method according to claim 13, wherein the change is carried out upstream the treatment unit, in the blood circuit, wherein

15. Method according to claim 13, wherein the change is carried out in the treatment liquid upstream the treatment unit, and the excess mass passed to the patient M′

is calculated by subtracting what is passed to the treatment unit from the excess mass M in the bolus.

16. Method according to claim 12, wherein the change is carried out in the blood circuit downstream the treatment unit, and wherein

17. Method according to claims 9 or 11, also comprising the steps of

providing the detectable change by injecting the substance either in the blood circuit upstream the blood inlet or in the treatment liquid side upstream the treatment unit, determining corresponding first and second concentration changes appearing in the treatment liquid line downstream the treatment unit

determining the clearance from the first integrated concentration change, and

determining the heart-lung parameter from the second integrated concentration change.

18. Method according to claim 9, further comprising the step of determining the heart-lung volume, or a parameter proportional to the heart-lung volume, as a product of the cardiac output and the time for the blood to pass the heart-lung system.

19. Method according to claim 18, also comprising the steps of

measuring a total time for the blood to pass trough the extracorporeal circuit, from a vascular access site to the heart lung system, and out from the heart lung system back to the access site,

providing the volume of the blood in the extracorporeal blood circuit and the blood circuit within the mammal from the extracorporeal blood circuit to the heart, and

determining the blood volume in heart-lung system using the measured time, the provided blood volumes and the cardiac output.

20. Method according to claim 18, wherein said time for passing through the heart lung system is obtained by:

determining a total time for the blood to pass trough the extracorporeal circuit, from a vascular access site to the heart-lung system, and out from the heart lung system back to the access site,

subtracting, from said total time, the time for the blood to flow through the extracorporeal circuit, and the time to reach the heart-lung system from access site and the time for the blood to go back out from the heart-lung system to the access site.

21. Method according to claim 19 or 20, wherein the step of determining the total time is obtained as follows:

in case the detectable perturbation is a change in concentration of a detectable substance carried out either on the blood upstream the treatment unit or on the treatment liquid upstream the treatment unit, then the total time is calculated as time lag between a first and a second change in the concentration of a substance with respect to a background level in the spent treatment liquid line at the outlet of the treatment unit,

in case the detectable perturbation is a change in concentration of a detectable substance carried out into the blood stream at a point downstream of the treatment unit, thereby giving only one change in the concentration of a substance with respect to a background level in the spent treatment liquid line at the outlet of the treatment unit, the total time is calculated as time lag between said change into the blood stream and the passage of said corresponding change in the spent treatment liquid.

22. Method according to claim 20, wherein the time for the blood to flow through the extracorporeal circuit is determined as function of blood flow rate within the extracorporeal circuit and of the dimensions of the circuit.

23. Method according to claim 20, wherein the time for the blood to flow through the extracorporeal circuit is determined by:

directing back to the extracorporeal circuit the blood which is returning to the patient, without passing through the heart-lung system of the patient,

making a measurable change in at least a blood property in a section of said extracorporeal circuit,

measuring the time for said change to flow through the extracorporeal circuit.

24. Method according to claim 23, wherein the directing step is obtained by creating a shortcut just outside the patient, so that, without entering the patient, the blood directed to the patient is redirected to the blood line leading back from the patient to the equipment.

25. Method according to claim 23, wherein the directing step is obtained by switching the blood lines so that blood is withdrawn from the patient at a point downstream and is returned to a point upstream, thus creating an artificial recirculation through the access of the patient.

26. Method according to claim 20, wherein the time for the blood to reach the heart-lung from the access is estimated as a function of access flow.

27. Method according to claim 26, wherein the time, indicated as vessel time, for the blood to reach the heart-lung from the access is estimated as:

Vessel time (in seconds)=1/Access flow (in L/min).

28. Method according to claim 20, wherein the time for the blood to reach the heart-lung from the access is a fix value in the range of 1-3 seconds.

29. Method according to claim 2, wherein the detectable substance is urea.

30. Method according to claim 29, wherein the urea concentration is measured on the treatment liquid side by the steps of

providing the urea in a reaction with a catalyst to form a second substance which effects the conductivity of the dialysis fluid, and

measuring the conductivity change.

31. Method according to claim 2, wherein the detectable substance is a salt.

32. Method according to claim 31, wherein the detectable substance is injected as a saline solution in water.

33. Method according to claim 2, wherein the detectable substance is glucose, which is injected as a solution in water.

34. Method according to claim 2, wherein the concentration change is measured by measuring the conductivity change of the treatment fluid.

35. Blood treatment equipment for implementing the method according to claim 1.

36. Software program for a control unit of a blood treatment equipment, said software program when executed by the control unit rendering the blood treatment equipment able to execute a method according to claim 1.