System and Methods for Wireless Body Fluid Monitoring

• US 20090076410A1
• Filed: 09/12/2008
• Published: 03/19/2009
• Est. Priority Date: 09/14/2007
• Status: Active Grant

• Current Assignee: Medtronic Monitoring, Inc. (Medtronic Plc)
• Original Assignee: Corventis Inc (Medtronic Plc)
• Inventors: Libbus, Imad, Bly, Mark
• Granted Patent: US 8,374,688 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 2560/0412 Low-profile patch shaped housings
• CPC Class Codes: A61B 2562/0215 Silver or silver chloride containing
• CPC Class Codes: A61B 2562/043 in a linear array
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/259 using conductive adhesive means, e.g. gels
• CPC Class Codes: A61B 5/28 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/282 Holders for multiple electrodes for introduction into the body A61B5/287
• CPC Class Codes: A61B 5/443 Evaluating skin constituents, e.g. elastin, melanin, water
• CPC Class Codes: A61B 5/6833 Adhesive patches
• CPC Class Codes: A61B 5/6843 Monitoring or controlling sensor contact pressure
• CPC Class Codes: G16H 40/67 for remote operation
• CPC Class Codes: G16H 50/30 for calculating health indices; for individual health risk assessment

Abstract

An adherent device to monitor a tissue hydration of a patient comprises an adhesive patch to adhere to a skin of the patient. At least four electrodes are connected to the patch and capable of electrically coupling to the patient. Impedance circuitry is coupled to the at least four electrodes to measure a tissue resistance of the patient, where the circuitry is configured to determine the tissue hydration in response to tissue resistance. The circuitry may comprise a processor system and the tissue resistance may correspond to a change in patient body fluid. The impedance circuitry is configured to measure the hydration signal using at least one low measurement frequency, which may be in the range of 0 to 10 kHz. Multiple measurement frequencies may be used and the hydration signal may include a tissue reactance measurement.

Claims

1. An adherent device to monitor a tissue hydration of a patient, the device comprising:

an adhesive patch to adhere to a skin of the patient;

at least four electrodes connected to the patch and capable of electrically coupling to the patient; and

circuitry coupled to the at least four electrodes to measure a tissue resistance of the patient, wherein the circuitry is configured to determine the tissue hydration in response to tissue resistance.

2. The adherent device of claim 1, wherein the circuitry comprises a processor system configured to determine the hydration of the patient in response to the tissue resistance.

3. The adherent device of claim 2, wherein the impedance circuitry is configured to measure the tissue resistance at a single frequency without tissue reactance and wherein the processor system is configured to determine the tissue hydration in response to the tissue resistance measured at the single frequency.

4. The adherent device of claim 1, wherein the tissue resistance corresponds to a change in patient body fluid.

5. The adherent device of claim 4, further comprising a processor coupled to the impedance circuitry, wherein the processor is configured to determine an amount of extracellular edema from the change in patient body fluid.

6. The adherent device of claim 1, wherein the hydration signal of the patient comprises a measurement of extracellular fluid.

7. The adherent device of claim 1, wherein the hydration signal of the patient further comprises a tissue reactance measurement.

8. The adherent device of claim 1, wherein the impedance circuitry is configured to measure the hydration signal using at least one low measurement frequency.

9. The adherent device of claim 8, wherein the at least one low measurement frequency is in the range of 5 to 15 kHz.

10. The adherent device of claim 8, wherein the at least one low measurement frequency comprises a single measurement frequency.

11. The adherent device of claim 10, wherein the single measurement frequency is in the range of 0 to 10 kHz.

12. The adherent device of claim 8, wherein the at least one low measurement frequency comprise multiple measurement frequencies.

13. The adherent device of claim 12, wherein the hydration signal further comprises a tissue reactance measurement.

14. An adherent device to monitor a patient, the device comprising:

an adhesive patch to adhere to a skin of the patient;

at least four electrodes connected to the patch and capable of electrically coupling to the patient at a skin-electrode interface; and

impedance circuitry coupled to the at least four electrodes to measure a hydration signal of the patient, wherein the impedance circuitry is configured to measure multiple frequencies.

15. The adherent device of claim 14, wherein the hydration signal comprises a tissue resistance measurement and a tissue reactance measurement.

16. The adherent device of claim 15, further comprising a processor coupled to the impedance circuitry, wherein the processor is configured to determine a quality of the skin-electrode interface from at least one of an ECG signal-to-noise ratio, a tissue reactance, a tissue impedance measured between any two of the at least four electrodes, or a second measurement frequency.

17. The adherent device of claim 16, wherein the processor is configured to determine the quality of the skin-electrode interface from a second measurement frequency.

18. The adherent device of claim 16, wherein the processor is configured to measure a droop in the tissue resistance.

19. A method of monitoring a patient, the method comprising:

adhering an adhesive patch to a skin of the patient to couple at least four electrodes to the skin of the patient to form a skin-electrode interface; and

measuring a hydration signal of the patient with impedance circuitry coupled to the at least four electrodes, wherein the hydration signal comprises a tissue resistance measurement.

20. The method of claim 19, wherein the tissue resistance measurement corresponds to a change in patient body fluid.

21. The method of claim 20, further comprising determining an amount of extracellular edema from the change in patient body fluid with a processor coupled to the impedance circuitry.

22. The method of claim 19, wherein the hydration signal is measured with at least one low measurement frequency.

23. The method of claim 22, wherein the at least one low measurement frequency is between 0 and 10 kHz.

24. The method of claim 22, wherein the at least one low measurement frequency comprise a single measurement frequency.

25. The method of claim 22, wherein the at least one low measurement frequency comprise multiple measurement frequencies.

26. The method of claim 19, wherein the hydration signal further comprises a tissue reactance measurement.

27. The method of claim 26, further comprising determining a quality of the skin-electrode coupling from the tissue reactance measurement.

28. The method of claim 27, wherein determining the quality of the skin-electrode coupling comprises at least one of determining an ECG signal-to-noise ratio, determining a tissue reactance, measuring the impedance between any two of the at least four electrodes, or measuring resistance at a second measurement frequency.

29. The method of claim 28, wherein determining the quality of the skin-electrode coupling further comprises identifying a poor skin-electrode coupling when the tissue reactance is greater than a threshold of about 10Ω

.

30. The method of claim 28, wherein determining the quality of the skin-electrode coupling further comprises identifying an irregular skin-electrode coupling when a tissue resistance droop exceeds a threshold of 10% of a nominal value.

31. The method of claim 28, wherein determining the quality of the skin-electrode coupling further comprises identifying a poor skin-electrode coupling when an impedance measured between two of the at least four electrodes is greater than a threshold of 5 kΩ

.

32. A method of monitoring a patient, the method comprising:

adhering an adhesive patch to a skin of the patient to couple at least four electrodes to the skin of the patient to form a skin-electrode interface;

measuring a hydration signal of the patient with impedance circuitry coupled to the at least four electrodes, wherein the hydration signal comprises a tissue resistance measurement and a tissue reactance measurement;

determining an amount of extracellular edema from the tissue resistance measurement; and

determining a quality of skin-electrode coupling from the tissue reactance measurement.

33. The method of claim 32, further comprising indicating a replacement status of the adhesive patch based on the quality of the skin-electrode coupling.

34. An adherent device to monitor a patient, the device comprising:

an adhesive patch to adhere to a skin of the patient;

at least four electrodes mechanically coupled to the patch and capable of electrically coupling to the patient, the at least four electrodes comprising at least two force electrodes and at least two sense electrodes;

impedance circuitry electrically coupled to the at least two force electrodes to force an electrical current and coupled to the at least two sense electrodes to measure a hydration signal of the patient, wherein the hydration signal comprises a tissue resistance measurement; and

a processor system coupled to the impedance circuitry configured to determine an amount of extracellular edema from the hydration signal.

35. The adherent device of claim 34, wherein the processor system is configured to calculate and report a patient risk of an adverse cardiac event to at least one of a remote center or a physician based on the amount of extracellular edema.

36. A method of monitoring a patient, the method comprising:

adhering an adhesive patch to a skin of the patient so as to couple at least four electrodes to the skin of the patient, the at least four electrodes comprising at least two force electrodes and at least two sense electrodes;

measuring a tissue resistance of the patient with impedance circuitry electrically coupled to the at least two force electrodes and to the at least two sense electrodes, such that the force electrodes force an electrical current between the at least two force electrodes, wherein the impedance circuitry generates a hydration signal; and

determining an amount of extracellular edema from the hydration signal.

37. The method of claim 36, wherein the electrical current is a low frequency current.

38. The method of claim 37, wherein the low frequency current has a frequency from 0 to 10 kHz.

39. The method of claim 36, wherein the electrical current has a single measurement frequency.