Thoracic impedance monitor and electrode array and method of use

• US 20050215918A1
• Filed: 03/24/2005
• Published: 09/29/2005
• Est. Priority Date: 03/24/2004
• Status: Active Grant

• Current Assignee: Caldwell Simpson LLC
• Original Assignee: Non-invasive Medical Technologies
• Inventors: Frantz, Ann K., Hamski, Philip
• Granted Patent: US 7,474,918 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/4869 Determining body composition
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses

Abstract

A portable thoracic impedance monitor for monitoring thoracic fluid levels, an electrode array assembly having a single linear electrode array lead with first, second, third, and fourth electrodes arranged sequentially and axially along the linear electrode array lead, and a method of use of the thoracic impedance monitor. A measurement of the user'"'"'s thoracic impedance is obtained by connecting the second electrode to the user'"'"'s body at the junction of the clavicles, superior to the sternum, the third electrode to the user'"'"'s body at the xyphiod-sternal junction, and the first and fourth electrodes to the user'"'"'s body substantially along a centerline of the user'"'"'s sternum respectively at a first pre-determined distance above the second electrode and a second predetermined distance below the third electrode, followed by initiating operation of the monitor.

Claims

1. A thoracic impedance monitor for determining thoracic impedance of a user, comprising:

an electrode array including a single linear electrode array lead and at least first, second, third, and fourth electrodes arranged axially along the single electrode array lead and connectable to the user at corresponding first, second, third, and fourth separate locations on a body of the user; and

a portable base unit operatively connected to the electrode array lead, including;

a power supply;

circuitry operatively connected to one of the first and second electrodes and to one of the third and fourth electrodes for generating an electrical signal for delivery to the one of the first and second electrodes and to the one of the third and fourth electrodes;

circuitry operatively connected to the other of the first and second electrodes and the other of the third and fourth electrodes for detecting differential electrical potential;

circuitry for calculating thoracic impedance of the user based upon the differential electrical potential; and

a display for displaying the thoracic impedance of the user.

2. The thoracic impedance monitor of claim 1, wherein the second electrode is operatively placed on the user'"'"'s body at the junction of the user'"'"'s clavicles, superior to the sternum and the third electrode is placed on the user'"'"'s body at the xyphiod-sternal junction.

3. The thoracic impedance monitor of claim 2, wherein the first electrode is placed higher on the user'"'"'s body substantially along a centerline of the user'"'"'s sternum at a first predetermined distance from the second electrode and the fourth electrode is placed lower on the user'"'"'s body substantially along the centerline of the user'"'"'s sternum at a second pre-determined distance from the third electrode.

4. The thoracic impedance monitor of claim 3, wherein the first and second electrodes are spaced on the electrode array lead at the first pre-determined distance and the third and fourth electrodes are spaced on the electrode array lead at the second pre-determined distance, such that with the electrode array lead fully extended, the first and second electrodes are spaced apart the first pre-determined distance and the third and fourth electrodes are spaced apart the second pre-determined distance.

5. The thoracic impedance monitor of claim 4, wherein the first and second pre-determined distances are each about five cm (about two inches).

6. The thoracic impedance monitor of claim 2, wherein the electrical signal is delivered to the first and fourth electrodes and the differential electrical potential is measured between the second and third electrodes.

7. The thoracic impedance monitor of claim 1, wherein the circuitry generating an electrical signal generates a current of about 2 mA and the circuitry detecting differential electrical potential detects a voltage in the range of about 20 mV to about 100 mV, corresponding to a thoracic impedance of the user in the range of about 10 to about 50 ohms.

8. The thoracic impedance monitor of claim 1, wherein the electrical signal is a pure sinusoidal wave generated by electrical components including a constant current source and a clock oscillator.

9. The thoracic impedance monitor of claim 8, wherein the electrical signal has a frequency in the range of about 90 kHz to about 110 kHz and current in the range of about 1.97 mA to about 1.99 mA.

10. The thoracic impedance monitor of claim 9, wherein the electrical signal has a frequency of about 100 kHz and a current of about 1.98 mA.

11. The thoracic impedance monitor of claim 1, the base unit further including a handle to facilitate transport of the base unit.

12. The thoracic impedance monitor of claim 1, wherein the power supply is provided by batteries.

13. The thoracic impedance monitor of claim 1, the base unit further including a serial data port.

14. A method of monitoring thoracic fluid level of a person, comprising the steps of:

providing a thoracic impedance monitor including;

an electrode array including a single linear electrode array lead and first, second, third, and fourth electrodes arranged axially along the single electrode array lead and connectable to the user at respective first, second, third, and fourth separate locations on a body of the user; and

a portable base unit operatively connected to the electrode array lead, including;

a power supply;

base unit circuitry including;

circuitry operatively connected to one of the first and second electrodes and to one of the third and fourth electrodes for generating an electrical signal for delivery to the one of the first and second electrodes and to the one of the third and fourth electrodes;

circuitry operatively connected to the other of the first and second electrodes and the other of the third and fourth electrodes for detecting differential electrical potential between the first and second electrodes and the third and fourth electrodes;

circuitry for calculating thoracic impedance of the user based upon the differential electrical potentials;

a start button operatively connecting the power supply to the base unit circuitry, and

a display for displaying the thoracic impedance of the user; and

obtaining a measurement of the user'"'"'s thoracic impedance by;

connecting the second electrode to the user'"'"'s body at the junction of the clavicles, superior to the sternum, the third electrode to the user'"'"'s body at the xyphiod-sternal junction, the first electrode to the user'"'"'s body substantially along a centerline of the user'"'"'s sternum at a first pre-determined distance above the second electrode and the fourth electrode to the user'"'"'s body substantially along the centerline of the user'"'"'s sternum at a second predetermined distance below the third electrode;

initiating operation of the thoracic impedance monitor by pressing the start button to apply a sinusoidal current to the first and fourth electrodes and detecting a differential electrical potential between the second and third electrodes; and

recording the thoracic impedance reading of the user from the display.

15. The method of monitoring thoracic fluid level of a person of claim 14, wherein the step of obtaining a measurement of the user'"'"'s thoracic impedance is performed on at least a daily basis.

16. The method of claim 15, wherein the daily measurements are taken at substantially the same time during the day.

17. The method of claim 16, wherein the daily measurements are taken before the user eats a first meal of the day.

18. An electrode array for use with a physiological electronic monitor used to monitor electrical characteristics of a user'"'"'s body, comprising a single linear electrode array lead including at least first, second, third, and fourth electrodes arranged sequentially and axially along the linear electrode array lead.

19. The electrode array of claim 18, wherein the first and second electrodes are spaced apart a first pre-determined distance by a first portion of the electrode lead and the third and fourth electrodes are spaced apart a second pre-determined distance by a second portion of the electrode lead equal to the first pre-determined distance.

20. The electrode array of claim 19, wherein-the electrode lead is sufficiently flexible between the second and third electrodes to vary the distance between the second and third electrodes on the user'"'"'s body.

21. The electrode array of claim 18, wherein the electrode lead is sufficiently flexible between the second and third electrodes to vary the distance between the second and third electrodes on the user'"'"'s body.

22. The electrode array of claim 18, in operable combination with a thoracic impedance monitor.