Medical fluid sensing and concentration determination using radio frequency energy and a magnetic field

• US 9,597,439 B2
• Filed: 03/15/2013
• Issued: 03/21/2017
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Original Assignee: Fresenius Medical Care Holdings Incorporated (Fresenius Medical Care AG)
• Inventors: Jones, Ross Peter, Crnkovich, Martin Joseph, Wang, Fei, Folden, Thomas Irvin, Jensen, Lynn, Kalaskar, Shashikant Dattatraya
• Primary Examiner(s): Bass, Dirk
• Assistant Examiner(s): BREWSTER, HAYDEN R
• Application Number:
  US13/836,450
• Publication Number:
  US 20140263063A1
• Time in Patent Office: 1,467 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: A61M 1/154 with sensing means or components thereof
• CPC Class Codes: A61M 1/1562 Details of incorporated reservoirs
• CPC Class Codes: A61M 1/16 with membranes
• CPC Class Codes: A61M 1/1605 Physical characteristics of the dialysate fluid
• CPC Class Codes: A61M 1/1619 Sampled collection of used dialysate, i.e. obviating the need for recovery of whole dialysate quantity for post-dialysis analysis
• CPC Class Codes: A61M 1/267 used for pumping
• CPC Class Codes: A61M 1/3609 Physical characteristics of the blood, e.g. haematocrit, urea
• CPC Class Codes: A61M 1/36222 Details related to the interface between cassette and machine
• CPC Class Codes: A61M 1/36224 with sensing means or components thereof
• CPC Class Codes: A61M 1/36226 Constructional details of cassettes, e.g. specific details on material or shape
• CPC Class Codes: A61M 2205/12 with interchangeable cassettes forming partially or totally the fluid circuit
• CPC Class Codes: A61M 2205/3317 Electromagnetic, inductive or dielectric measuring means
• CPC Class Codes: A61M 2205/3324 PH measuring means
• CPC Class Codes: A61M 2205/3331 Pressure; Flow
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2205/6072 Bar codes
• CPC Class Codes: A61M 2205/702 automatically during use
• CPC Class Codes: A61M 2230/20 Blood composition characteristics
• CPC Class Codes: G01N 24/08 by using nuclear magnetic resonance G01N24/12 takes precedence
• CPC Class Codes: G01R 33/1276 of magnetic particles, e.g. imaging of magnetic nanoparticles G01R33/1269 takes precedence
• CPC Class Codes: G01R 33/302 : Miniaturized sample handling arrangements for sampling small quantities, e.g. flow-through microfluidic NMR chips
• CPC Class Codes: G01R 33/34053 : Solenoid coils; Toroidal coils
• CPC Class Codes: G01R 33/383 : using permanent magnets
• CPC Class Codes: G01R 33/465 : applied to biological material, e.g. in vitro testing
• CPC Class Codes: G16H 20/17 : delivered via infusion or injection
• CPC Class Codes: G16H 50/20 : for computer-aided diagnosis, e.g. based on medical expert systems

Abstract

This disclosure relates to medical fluid sensors and related systems and methods. In certain aspects, a method includes using a medical fluid pump of a medical fluid pumping machine, such as a hemodialysis machine, to deliver medical fluid to a first portion of a cartridge that is positioned within a magnetic field, exciting atoms in the medical fluid in the first portion of the cartridge by applying radio frequency energy to the medical fluid in the first portion of the cartridge, receiving radio frequency energy generated by the excited atoms in the medical fluid in the first portion of the cartridge, and determining a concentration of a substance in the medical fluid based on the received radio frequency energy generated by the excited atoms in the medical fluid in the first portion of the cartridge.

Claims

1. A method comprising:

using a dialysis fluid pump of a dialysis machine to deliver dialysis fluid to a first portion of a cartridge by first passing the dialysis fluid through a first fluid passageway of the cartridge, the first fluid passageway being positioned within a first magnetic field and outside a radio frequency device, and the first portion of the cartridge being positioned within the first magnetic field and within the radio frequency device, the first magnetic field aligning atoms of a substance of the dialysis fluid in the first fluid passageway;

exciting the atoms of the substance in the dialysis fluid in the first portion of the cartridge by applying radio frequency energy to the dialysis fluid in the first portion of the cartridge using the radio frequency device, the radio frequency energy changing the alignment of the atoms of the substance of the dialysis fluid, the atoms of the substance generating a second magnetic field in the first portion of the cartridge;

receiving radio frequency energy generated by the excited atoms of the substance in the dialysis fluid in the first portion of the cartridge; and

determining a concentration of the substance in the dialysis fluid in the first portion of the cartridge based on the received radio frequency energy generated by the excited atoms of the substance of the dialysis fluid in the first portion of the cartridge.

2. The method of claim 1, wherein the dialysis fluid is blood.

3. The method of claim 1, wherein the dialysis fluid is dialysate.

4. The method of claim 3, wherein the dialysate is spent dialysate.

5. The method of claim 4, further comprising delivering fresh dialysate to the first portion of the cartridge, exciting atoms of the substance in the fresh dialysate in the first portion of the cartridge by applying radio frequency energy to the fresh dialysate in the first portion of the cartridge, receiving radio frequency energy generated by the excited atoms of the substance in the fresh dialysate in the first portion of the cartridge, and determining a concentration of the substance in the fresh dialysate based on the received radio frequency energy generated by the excited atoms of the substance in the fresh dialysate in the first portion of the cartridge.

6. The method of claim 5, further comprising determining a concentration of the substance in blood of a dialysis patient based on the determined concentrations of the spent dialysate and the fresh dialysate.

7. The method of claim 6, further comprising adjusting a concentration of the substance in the fresh dialysate to match the determined concentration of the substance in the blood.

8. The method of claim 1, wherein the substance is sodium.

9. The method of claim 1, wherein the dialysis fluid is delivered to the first portion of the cartridge while dialysis treatment is being carried out by the dialysis machine.

10. The method of claim 9, wherein the concentration of the substance in the dialysis fluid is determined while dialysis treatment is being carried out by the dialysis machine.

11. The method of claim 1, wherein the dialysis fluid is blood, and the method further comprises adjusting a concentration of the substance in dialysate based on the determined concentration of the substance in the blood.

12. The method of claim 11, wherein the concentration of the substance in the dialysate is adjusted to match the determined concentration of the substance in the blood.

13. The method of claim 1, wherein the radio frequency energy generated by the excited atoms in the dialysis fluid in the first portion of the cartridge is received by the radio frequency device.

14. The method of claim 13, wherein applying the radio frequency energy to the dialysis fluid in the first portion of the cartridge comprises activating the radio frequency device.

15. The method of claim 14, wherein the radio frequency device is a radio frequency coil.

16. The method of claim 13, wherein the first magnetic field is generated by a magnet assembly defining a cavity in which the radio frequency device and the first portion of the cartridge are disposed.

17. The method of claim 1, wherein the first fluid passageway is a first meandering fluid passageway, the first meandering fluid passageway being positioned within the first magnetic field.

18. The method of claim 17, wherein the dialysis fluid is in the first meandering fluid passageway for a sufficient period of time to polarize nuclei of the atoms of the substance.

19. The method of claim 17, wherein the first portion of the cartridge defines a second meandering fluid passageway.

20. The method of claim 19, wherein the dialysis fluid is in the second meandering fluid passageway for a sufficient period of time for the atoms of the substance in the dialysis fluid to be excited by the applied radio frequency energy and for the radio frequency energy generated by the excited atoms to be received.

21. The method of claim 1, wherein the dialysis fluid is delivered to the first portion of the cartridge at a rate of 50 milliliters per minute to 200 milliliters per minute.

22. The method of claim 1, wherein the dialysis fluid flows through the first portion of the cartridge.

23. The method of claim 22, wherein the dialysis fluid flows through the first portion of the cartridge at a rate of 50 milliliters per minute to 200 milliliters per minute.

24. The method of claim 1, wherein the dialysis fluid resides substantially stagnantly within the first portion of the cartridge for a period of time.

25. The method of claim 24, wherein the dialysis fluid is dialysate.

26. The method of claim 1, wherein a first portion of the dialysis fluid is delivered to the first portion of the cartridge, and a second portion of the dialysis fluid passes through a second portion of the cartridge.

27. The method of claim 26, wherein the second portion of the cartridge is positioned outside the radio frequency device that applies the radio frequency energy to the dialysis fluid in the first portion of the cartridge, and the second portion of the cartridge is at least partially positioned outside a magnet assembly that generates the magnetic field.

28. The method of claim 26, wherein the second portion of the cartridge defines a fluid passageway that bypasses the first portion of the cartridge.

29. The method of claim 26, wherein the first portion of the dialysis fluid flows through the first portion of the cartridge at a slower rate than the second portion of the dialysis fluid passes through the second portion of the cartridge.

30. The method of claim 1, wherein the concentration of the substance in the dialysis fluid is determined as a function of (i) the radio frequency energy generated by the excited atoms of the substance in the dialysis fluid in the first portion of the cartridge and (ii) a volume of the first portion of the cartridge.