Method and device for measuring tissue oedema

• US 6,760,617 B2
• Filed: 12/20/2001
• Issued: 07/06/2004
• Est. Priority Date: 06/22/1999
• Status: Expired due to Term

• Current Assignee: Queensland University of Technology, The University of Queensland
• Original Assignee: Queensland University of Technology, The University of Queensland
• Inventors: Cornish, Bruce Herbert, Ward, Leigh
• Primary Examiner(s): Hindenburg, Max F.
• Assistant Examiner(s): FOREMAN, JONATHAN M
• Application Number:
  US10/029,015
• Publication Number:
  US 20020161311A1
• Time in Patent Office: 929 Days
• Field of Search: 600/372, 600/382, 600/384, 600/393, 600/547, 600/548
• 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 5/4878 Evaluating oedema

Abstract

The present invention provides a method of assessing tissue oedema, in particular lymphoedema, by measuring bioelectrical impedance at a single frequency. Comparison of a single frequency bioelectrical impedance measurement taken at an anatomical region affected by tissue oedema to that taken at an anatomical region unaffected by tissue oedema is a reliable indicator of the presence or possible presence of lymphoedema. The present invention further provides an apparatus for determining the presence of tissue oedema.

Claims

1. A method of assessing tissue oedema comprising the steps of:

performing a first measurement of bioelectrical impedance of a first anatomical region in a subject at a single low frequency alternating current;

performing a second measurement of bioelectrical impedance of a second anatomical region in the same subject at the same low frequency alternating current; and

analysing the first and second measurements to obtain an indication of the presence of tissue oedema;

wherein the step of analysing the first and second measurements to obtain an indication of the presence of tissue oedema includes the step of applying the algorithm;

$F=\frac{Z_h}{Z_l}-\mathrm{cf}$

 

where;

F is an indication of tissue oedema;

Z_h is the greater bioelectrical impedance reading;

Z₁ is a lesser bioelectrical impedance reading; and

cf is a correcting factor.

2. The method of claim 1 wherein the correcting factor is 1.066.

3. The method of claim 1, wherein the first anatomical region and the second anatomical region are paired and wherein one of the anatomical regions is unaffected by tissue oedema.

4. The method of claim 1, wherein the first anatomical region and the second anatomical region are dissimilar and wherein one of the anatomical regions is unaffected by tissue oedema.

5. The method of claim 1, wherein the first anatomical region and the second anatomical region are the same and wherein the first measurement and the second measurement are separated in time.

6. The method of claim 1, wherein the anatomical regions are limbs or parts of limbs.

7. The method of claim 1, wherein the single low frequency alternating current is in the range of 5 to 20 kHz.

8. The method of claim 7, wherein the single low frequency alternating current is in the range of 10 to 15 kHz.

9. The method of claim 8, wherein the single low frequency alternating current is 10 kHz.

10. The method of claim 1, further including the step of establishing a correcting factor for analysing the two measurements.

11. The method of claim 10, wherein the step of establishing a correcting factor includes the step of obtaining bioelectric impedance measurements from a plurality of subjects unaffected by tissue oedema.

12. An apparatus for determining the presence of tissue oedema, including:

current means for applying an alternating current to an anatomical region at a single frequency;

monitoring means to monitor the bioelectrical impedance of said region and produce signals characteristic of bioimpedance; and

analysis means to analyse the signals indicative of bioimpedance to provide an indication of tissue iedema;

wherein the analysis means is programmed to analyse data according to the algorithm;

$F=\frac{Z_h}{Z_l}-\mathrm{cf}$

 

where;

F is an indication of the presence of tissue oedema;

Z_h is a greater bioelectrical impedance measurement;

Z_l is a lesser bioelectrical impedance measurement; and

cf is the correcting factor.

13. The apparatus of claim 12, wherein the current means is a proximal electrode and a distal electrode in connection with a power source.

14. The apparatus of claim 12, the monitoring means is a first connection and a second connection for location on or near the anatomical region.

15. The apparatus of claim 12, wherein the analysis means is at least one processing means programmed to perform analysis of data to provide an indication of the presence of tissue oedema.

16. The apparatus of claim 12, further including means for recording bioimpedance in two anatomical regions of the same subject simultaneously.

17. A method of assessing tissue oedema comprising the steps of:

performing a first measurement of bioelectrical impedance of a first anatomical region in a subject at a single low frequency alternating current;

performing a second measurement of bioelectrical impedance of a second anatomical region in the same subject at the same low frequency alternating current; and

analysing the first and second measurements to obtain an indication of the presence of tissue oedema;

wherein the step of analysing the first and second measurements to obtain an indication of the presence of tissue oedema includes the step of applying the algorithm;

$F={\mathrm{cf}}_1-\frac{Z_l}{Z_h}$

 

where;

F is an indication of tissue oedema;

cf₁ is a correcting factor;

Z_l is a lesser bioelectrical impedance reading, and

Z_h is a greater bioelectrical impedance reading.

18. The method of claim 17, when used on paired limbs and cf₁=0.862.

19. The method of claim 17, wherein the first anatomical region and the second anatomical region are paired and wherein one of the anatomical regions is unaffected by tissue oedema.

20. The method of claim 17, wherein the first anatomical region and the second anatomical region are dissimilar and wherein one of the anatomical regions is unaffected by tissue oedema.

21. The method of claim 17, wherein the first anatomical region and the second anatomical region are the same and wherein the first measurement and the second measurement are separated in time.

22. The method of claim 17, wherein the first and second anatomical regions are limbs or parts of limbs.

23. The method of claim 17, wherein the single low frequency alternating current is in the range of 5 to 20 kHz.

24. The method of claim 23, wherein the single low frequency alternating current is in the range of 10 to 15 kHz.

25. The method of claim 24, wherein the single low frequency alternating current is 10 kHz.

26. The method of claim 17, further including the step of establishing a correcting factor for analysing the two measurements.

27. The method of claim 26, wherein the step of establishing a correcting factor includes the step of obtaining bioelectrical impedance measurements from a plurality of subjects unaffected by tissue oedema.

28. An apparatus for determining the presence of tissue oedema, including:

current means for applying an alternating current to an anatomical region at a single frequency;

monitoring means to monitor the bioelectrical impedance of said region and produce signals characteristic of bioimpedance; and

analysis means to analyse the signals indicative of bioimpedance to provide an indication of tissue oedema;

wherein the analysis means is programmed to analyse data according to the algorithm;

$F={\mathrm{cf}}_1-\frac{Z_l}{Z_h}$

 

where;

F is an indication of tissue oedema;

cf₁ is a correcting factor;

Z_l is a lesser bioelectrical impedance measurement; and

Z_h is a greater bioelectrical impedance measurement.

29. The apparatus of claim 28, wherein the current means is a proximal electrode and a distal electrode in electrical connection with a power source.

30. The apparatus of claim 28, wherein the monitoring means is a first connection and a second connection for location on or near the anatomical region.

31. The apparatus of claim 28, wherein the analysis means is at least one processing means programmed to perform analysis of data to provide an indication of the presence of tissue oedema.

32. The apparatus of claim 28, further including means for recording bioimpedance in two anatomical regions of the same subject simultaneously.