Non-invasive in vivo determination of body fluid parameter

• US 20030220581A1
• Filed: 03/26/2003
• Published: 11/27/2003
• Est. Priority Date: 03/26/2002
• Status: Active Grant

• Current Assignee: D.T.R. Dermal Therapy Research Inc.
• Original Assignee: Alan Lorne Perlmutter, Peter Aberg, Stig Ollmar
• Inventors: Aberg, Peter, Ollmar, Stig, Perlmutter, Alan Lorne
• Granted Patent: US 7,050,847 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0531 Measuring skin impedance
• CPC Class Codes: A61B 5/061 Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body A61B1/00158 takes precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/411 Detecting or monitoring allergy or intolerance reactions to an allergenic agent or substance

Abstract

A non-invasive method of monitoring a biological parameter concerning a bodily fluid of a subject, e.g., blood glucose of a human subject. The method includes: placing an electrode against a site of the skin of the subject; measuring impedance of the skin and determining the parameter therefrom; and using substantially the same site in another determination. Another non-invasive monitoring method includes: exposing a skin site to an aqueous salt solution for a pre-determined first period of time; removing excess of the solution from the site; measuring impedance at the site; exposing the site to the solution for a pre-determined second period of time and repeating the removing and measuring steps. It is determined whether the impedance measured falls within a pre-determined range. The latter exposure and removal steps are repeated, if necessary, until two consecutive impedance measurements within the pre-determined range are obtained.

Claims

1. A non-invasive method of monitoring a biological parameter concerning a bodily fluid of a mammal, the method comprising the steps of:

(i) placing an electrode against a site of the skin of the mammal;

(ii) measuring impedance of the skin and determining said parameter therefrom; and

(iii) after a period of time, repeating steps (i) and (ii), wherein during each placing step, said site is substantially the same site.

2. The method of claim 1, wherein the period of time is between 1 hour and 48 hours, or between 1 hour and 36 hours, or between 1 hour and 24 hours, or between 1 hour and 22 hours, or between 1 hour and 20 hours, or between 1 hour and 18 hours, or between 1 hour and 16 hours, or between 1 hour and 14 hours, or between 1 hour and 12 hours, or between 1 hour and 10 hours, or between 1 hour and 8 hours, or between 1 hour and 7 hours, or between 1 hour and 6 hours, or between 1 hour and 5 hours, or between 1 hour and 4 hours, or between 1 hour and 3 hours, or between 1 and 2 hours.

3. The method of claim 1, wherein said electrode has a reference point which abuts a first point of the skin when the electrode is placed against the skin, and during said repeating of step (i) a second said point of the skin is within a distance of 1 cm of the first point of the skin.

4. The method of claim 1, further comprising the step of, prior to step (i), locating an indexing device adjacent the skin of the mammal wherein said site of step (i) is determined by its location with respect to a predetermined position of the device.

5. The method of claim 1 wherein the mammal is human and the site is located on the volar forearm thereof.

6. The method of claim 1 wherein said parameter is the blood glucose level of the mammal.

7. The method of claim 1 wherein a center point of a said site in step (i) is spaced no more than the diameter of the electrode in contact with the skin from the center point of a said site when step (i) is repeated, more preferably, no more than the radius of the electrode, more preferably no more than the radius/2 of the electrode.

8. The method of claim 1 wherein a center point of a said site in step (i) is spaced no more than 3 cm (preferably, no more than 2.5 cm, more preferably 2 cm, more preferably 1.5 cm, more preferably 1 cm, more preferably 0.5 cm) from the center point of a said site when step (i) is repeated.

9. The method of claim 1, further comprising the step of marking the skin.

13. Apparatus for use in determining blood glucose of a mammal by means of a skin impedance measurement of a person, the apparatus comprising an indexing tool for placement in a predetermined position against the skin of the person, the tool including an indicator for locating a probe with respect thereto against the skin of the mammal, and a set of instructions for use of the apparatus according to a method of claim 4.

14. The apparatus of claim 13, wherein the device includes a flange shaped to abut the volar forearm of a said person with the indicator in a location for positioning the probe directly against a skin surface on the volar forearm.

10. A method of calibrating an impedance measuring device for use with a mammalian subject, the method comprising the steps of:

(i) locating an indexing tool in a predetermined position against the skin of the mammal;

(ii) placing a probe of the device against the skin at a predetermined location with respect to the tool;

(iii) measuring impedance of the skin;

(iv) measuring a biological parameter concerning a bodily fluid of a mammal; and

(v) correlating the measurements of steps (iii) and (iv).

11. Apparatus for use during determination of a biological parameter concerning a bodily fluid of a mammal, the apparatus comprising an indexing tool for placement in predetermined position against the skin of the mammal, the tool including an indicator for locating a probe with respect thereto against the skin of the mammal.

12. The apparatus of claim 11, further comprising an impedance measuring device comprising said probe.

15. A method for non-invasively monitoring a component in a body fluid of a subject, the method comprising:

(i) exposing a skin site of the subject at which a measurement is to be made to an aqueous salt solution for a pre-determined first period of time;

(ii) (a) removing excess of the solution from the site;

(b) measuring impedance at the site;

(iii) exposing the site to the solution for a pre-determined second period of time and repeating step (ii);

(iv) determining whether the impedance measured in step (iii) falls within a pre-determined range;

(v) repeating steps (iii) and (iv) as necessary until the impedance measured in step (iii) falls within the pre-determined range; and

(vi) determining the amount of the component in the fluid based upon the impedance measured in step (v).

16. The method of claim 15, wherein the range of step (iv) is empirically determined for the subject, the empirical determination being based on impedance measurements and a second type of measurement in which the amount of component present is determined for a sample of the body fluid obtained from the subject.

17. The method of claim 16, wherein steps (iii) and (iv) are repeated at least until the impedance measured in step (iii) falls with said range for two consecutive of the impedance measurements.

18. The method of claim 17, wherein determining the amount of the component is based on an average of the at least two consecutive impedance measurements.

19. The method of claim 18, wherein the first period is greater than said second period.

20. The method of claim 19, wherein the first period is at least about 40 seconds.

21. The method of claim 20, wherein the second period is less than about 20 seconds.

22. The method of claim 21, wherein the second period is less than about 15 seconds.

23. The method of claim 22, wherein the second period is about 10 seconds.

24. The method of claim 23, wherein the first period is less than about 60 seconds.

25. The method of claim 24, wherein the first period is less than about 50 seconds.

26. The method of claim 25, wherein the first period is about 40 seconds.

27. The method of claim 26, wherein the body fluid is blood.

28. The method of claim 27, wherein the component is glucose.

29. The method of claim 28, wherein comprises an inorganic salt compatible with human skin.

30. The method of claim 29, wherein the aqueous solution is a saline solution.

31. The method of claim 30, wherein, in step (ii) (b), measuring skin impedance includes abutting an electrode in direct contact with the skin site and/or the impedance is measured a plurality of frequencies.