Ion imbalance detector

• US 9,289,165 B2
• Filed: 10/15/2014
• Issued: 03/22/2016
• Est. Priority Date: 02/07/2005
• Status: Active Grant

• Current Assignee: Mozarc Medical US LLC
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Soykan, Orhan, Robinson, Timothy H., Carney, James K., Nahey, Tara L., Chan, Cygni
• Primary Examiner(s): Bertram, Eric D.
• Application Number:
  US14/514,829
• Publication Number:
  US 20150032023A1
• Time in Patent Office: 524 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/1107 Measuring contraction of parts of the body, e.g. organ, muscle apparatus for measuring work or force in general G01L
• CPC Class Codes: A61B 5/1451 for interstitial fluid
• CPC Class Codes: A61B 5/14542 for measuring blood gases A61B5/14551 takes precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/1473 invasive, e.g. introduced into the body by a catheter A61B5/1482 takes precedence
• CPC Class Codes: A61B 5/4519 Muscles A61B5/389, A61B5/224 take precedence
• CPC Class Codes: A61B 5/686 Permanently implanted devices, e.g. pacemakers, other stimulators, biochips A61B5/6861 takes precedence
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61M 5/14276 specially adapted for implantation
• CPC Class Codes: A61M 5/1723 using feedback of body parameters, e.g. blood-sugar, pressure measurement of body parameters A61B5/00
• CPC Class Codes: A61N 1/36135 using physiological parameters
• CPC Class Codes: A61N 1/36167 Timing, e.g. stimulation onset
• CPC Class Codes: A61N 1/36557 controlled by chemical substances in blood

Abstract

In general, the invention is directed to methods and devices for determining an ion concentration in the extracellular fluid of a patient. As examples, the ion may be one or more of potassium, sodium, chloride, or calcium. A system includes an electrode deployed in or near a tissue, such as a skeletal muscle, of the patient. A pulse generator supplies one or more stimulations to the tissue, and a sensor, such as an accelerometer, detects the response of the tissue to the stimulations. A processor determines a concentration of ions in the extracellular fluid as a function of the response. The system may detect an ion imbalance based upon the determined concentration of ions.

Claims

1. A method comprising:

delivering an electrical stimulation to a tissue in a patient using an electrode;

detecting a response of the tissue to the electrical stimulation using a sensor;

wherein the response is any one or more selected from the group consisting of a sustained contraction of the tissue, a rippled contraction of the tissue, a rate of relaxation of the tissue, a pulse width of the response, an occurrence of summation in the response, an amplitude of the response, muscle tension, muscle motion or muscle length, a decline of muscle tension following cessation of the stimulation, and a fall time of muscle tension following cessation of the stimulation; and

storing a relationship between a concentration of ions in extracellular fluid of the patient and the response in a non-transitory, computer readable medium.

2. The method of claim 1, wherein the ions are at least one of potassium, sodium, chloride, calcium, bicarbonate, or magnesium ions.

3. The method of claim 1, wherein the electrical stimulation is delivered to any of cardiac muscle, skeletal muscle, smooth muscle, nerve tissue, or skin of the patient.

4. The method of claim 1, wherein the electrical stimulation is a first electrical stimulation and the response is a first response, the method further comprising

delivering a second electrical stimulation to the tissue;

detecting a second response of the tissue to the second electrical stimulation; and

determining a concentration of ions in the extracellular fluid of the patient as a function of the first and second responses.

5. The method of claim 4, wherein determining the concentration of ions in the extracellular fluid of the patient comprises determining a change in concentration of ions in the extracellular fluid over time.

6. The method of claim 4, wherein the first electrical stimulation and second electrical stimulation each comprise two stimulations;

wherein the time between the two stimulations of the first electrical stimulation is different from the time between the two stimulations of the second electrical stimulation.

7. The method of claim 4, wherein the frequency of the first electrical stimulation is different from the frequency of the second electrical stimulation.

8. The method of claim 1, further comprising determining the absolute concentration of ions in the extracellular fluid.

9. The method of claim 1, further comprising determining the activity status of the patient;

wherein the electrical stimulation is delivered when the activity status of the patient is inactive.

10. The method of claim 1, wherein storing a relationship between a concentration of ions in extracellular fluid of the patient and the response comprises storing a relationship between a concentration of 2 or more different ions in extracellular fluid of the patient and the response.

11. The method of claim 10, wherein the relationship between the concentration of 2 or more different ions in extracellular fluid of the patient and the response comprises a ratio of the 2 or more different ions in extracellular fluid.

12. The method of claim 1, wherein the response is any one of muscle tension, muscle motion or muscle length.

13. The method of claim 1 wherein the response is the decline of muscle tension following cessation of the stimulation.

14. The method of claim 1 wherein the response is the fall time of muscle tension following cessation of the stimulation.

15. A system, comprising

a control unit configured to control a pulse generator to deliver an electrical stimulation to a tissue in a patient;

and

a processor configured to receive from a sensor a signal indicative of a response of the tissue to the electrical stimulations and store a relationship in a non-transitory, computer readable medium between a concentration of ions in extracellular fluid of the patient and the response;

wherein the response is any one or more selected from the group consisting of a sustained contraction of the tissue, a rippled contraction of the tissue, a rate of relaxation of the tissue, a pulse width of the response, an occurrence of summation in the response, an amplitude of the response, muscle tension, muscle motion or muscle length, a decline of muscle tension following cessation of the stimulation, and a fall time of muscle tension following cessation of the stimulation.

16. The system of claim 15, wherein the ions are at least one of potassium, sodium, chloride, calcium, or magnesium ions.

17. The system of claim 15, wherein the processor is further configured to receive data concerning a measured concentration of ions in the extracellular fluid;

and correlate the measured concentration with the response.

18. The system of claim 15, wherein the signal indicative of a response of the tissue to the electrical stimulations is a radio frequency signal or a wire transmitted signal.

19. The system of claim 15, wherein the processor is configured to transmit the relationship between the concentration of ions in extracellular fluid of the patient and the response to an external computing device.