Method for evaluating extracellular water concentration in tissue

• US 20070118027A1
• Filed: 11/18/2005
• Published: 05/24/2007
• Est. Priority Date: 03/16/2001
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Hoarau, Carine, Ostrowski, Rafael, Campbell, Shannon, Debreczeny, Martin, Schmitt, Joseph, Durr, Nick, Baker, Clark
• Granted Patent: US 7,657,292 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• 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: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

The present disclosure provides systems, devices, and/or methods for assessing body fluid-related metrics and/or changes therein. The disclosure further provides systems, devices, and/or methods for correlating body fluid-related metrics in a particular tissue with the corresponding whole-body metric. The disclosure also provides, systems, devices, and/or methods for assessment of such metrics to facilitate diagnosis and/or therapeutic interventions related to maintaining and/or restoring body fluid balance.

Claims

1. A method for assessing an extracellular water metric in a subject, said method comprising:

emitting light of at least one wavelength toward a tissue site of interest, wherein a portion of the emitted light is reflected by the tissue site of interest;

detecting at least one wavelength of the light reflected by the tissue site of interest from a position about one millimeter to about five millimeters from the tissue site of interest;

emitting light of at least one wavelength toward a reference tissue site, wherein a portion of the emitted light is reflected by the reference tissue site;

detecting at least one wavelength of the light reflected by the reference tissue site from a position about one millimeter to about five millimeters from the reference tissue site; and

processing detected reflected light from the tissue site of interest and detected reflected light from the reference tissue site to compute the extracellular water metric.

2. A method according to claim 1, wherein the extracellular water metric is selected from the group of extracellular water metrics consisting of intravascular water fraction, ƒ

_w^IV, interstitial water fraction ƒ

_w^IS, extracellular water fraction, ƒ

_w^EC, water balance index, Q, and combinations thereof.

3. A method according to claim 1, wherein the extracellular water metric is selected from the group of extracellular water metrics consisting of changes in the intravascular water fraction, Δ

ƒ

_w^IV, changes in the interstitial water fraction, Δ

ƒ

_w^IS changes in the extracellular water fraction, Δ

ƒ

_w^EC, changes in the water balance index, Δ

Q, and combinations thereof.

4. A method according to claim 1, wherein the extracellular water metric is a metric of at least a portion of the subject'"'"'s whole body.

5. A method according to claim 4 further comprising comparing the extracellular water metric with a control and determining from that comparison whether the at least a portion of the subject'"'"'s whole body is dehydrated or over-hydrated.

6. A method according to claim 5 further comprising administering a hydration therapy to a dehydrated subject.

7. A method according to claim 5 further comprising administering a dehydration therapy to an over-hydrated subject.

8. A method according to claim 1, wherein the hydrostatic pressure of the tissue site of interest differs from the hydrostatic pressure of the reference tissue site.

9. A method according to claim 1 further comprising exhibiting the extracellular water metric on a display.

10. A method according to claim 1, wherein the light detected by the first detector comprises a wavelength selected from the group of wavelengths consisting of 950-1400 nm, 1500-1800 nm, and 2000-2300 nm.

11. A method according to claim 9, wherein the wavelength of light detected by the first detector comprises a wavelength selected from the group of wavelengths consisting of 1180 nm, 1125 nm, 1168 nm, 1170 nm, 1185 nm, 1190 nm, 1230 nm, 1245 nm, 1250 nm, 1274 nm, 1275 nm, 1300 nm, 1330 nm, 1710 nm, 1730 nm, 1740 nm, and combinations thereof.

12. A method according to claim 9, wherein at least two wavelengths of light are detected by the first detector.

13. A method according to claim 12, wherein the wavelengths differ by at least 10 nm.

14. A method according to claim 1, wherein the light detected by the second detector comprises at least one wavelength within a wavelength band selected from the group of wavelength bands consisting of 950-1400 nm, 1500-1800 nm, and 2000-2300 nm.

15. A method according to claim 14, wherein the wavelength of light detected by the second detector comprises a wavelength selected from the group of wavelengths consisting of 1180 nm, 1125 nm, 1168 nm, 1170 nm, 1185 nm, 1190 nm, 1230 nm, 1245 nm, 1250 nm, 1274 nm, 1275 nm, 1300 nm, 1330 nm, 1710 nm, 1730 nm, 1740 nm, and combinations thereof.

16. A method according to claim 14, wherein at least two wavelengths of light are detected by the second detector.

17. A method according to claim 16, wherein the wavelengths differ by at least 10 nm.

18. A method according to claim 1, wherein the emitting light of at least one wavelength toward the tissue site of interest comprises emitting light from a light source and wherein the emitting light of at least one wavelength toward the reference tissue site comprises emitting light from said light source.

19. A method according to claim 1, wherein the emitting light of at least one wavelength toward the tissue site of interest comprises emitting light from a first light source and wherein the emitting light of at least one wavelength toward the reference tissue site comprises emitting light from a second light source.

20. A method according to claim 1, wherein the detecting light of at least one wavelength reflected by the tissue site of interest comprises detecting light with a detector and wherein the detecting light of at least one wavelength reflected by the reference tissue site comprises detecting light with said detector.

21. A method according to claim 1, wherein the detecting light of at least one wavelength reflected by the tissue site of interest comprises detecting light with a first detector and wherein the detecting light of at least one wavelength reflected by the reference tissue site comprises detecting light with a second detector.

22. A method according to claim 1, wherein the tissue site of interest and reference tissue site are located at two different sites within a single, contiguous organ.

23. A method according to claim 1, wherein the tissue site of interest and reference tissue site are located within different organs.

24. A method according to claim 1, wherein the tissue site of interest and reference tissue site are at substantially the same site under differing hydrostatic pressures.

25. A method according to claim 1, wherein the assessment is substantially independent of light scattering variations and temperature variations.

26. A method according to claim 1, wherein the light source is from about one millimeter to about five millimeters from the tissue site of interest.

27. A method according to claim 1, wherein the light source is from about one millimeter to about five millimeters from the reference tissue site.

28. A method according to claim 1 further comprising (a) excising from the subject the site of interest before the emitting, (b) excising from the subject the reference site before the emitting, or (c) excising from the subject both the site of interest and the reference site before the emitting.

29. A method according to claim 1, wherein the subject is a mammal.

30. A method according to claim 29, wherein the mammal is a human.

31. A method for assessing a whole-body extracellular water metric in a subject, said method comprising:

assessing a first localized extracellular water metric at a first tissue site in the subject;

assessing a second localized extracellular water metric at a second tissue site in the subject; and

processing the first and second localized extracellular water metrics to produce a whole-body extracellular water metric.

32. A method according to claim 31, wherein the first tissue site comprises the skin.

33. A method according to claim 31, wherein the second tissue site comprises the skin.

34. A method according to claim 31, wherein assessing the first localized extracellular water metric comprises measuring bioimpedence, transepidermal water loss, viscoelasticity, infrared light, magnetic resonance, ultrasound, or combinations thereof.

35. A method according to claim 31, wherein assessing the second localized extracellular water metric comprises measuring bioimpedence, transepidermal water loss, viscoelasticity, infrared light, magnetic resonance, ultrasound, or combinations thereof.

36. A method according to claim 31, wherein the extracellular water metric is selected from the group of extracellular water metrics consisting of intravascular water fraction, ƒ

_w^IV, interstitial water fraction ƒ

_w^IS, 5 extracellular water fraction, ƒ

_w^EC, water balance index, Q, and combinations thereof.

37. A method according to claim 36, wherein the extracellular water metric is selected from the group of extracellular water metrics consisting of changes in the intravascular water fraction, Δ

ƒ

_w^IV, changes in the interstitial water fraction, Δ

ƒ

_w^IS, changes in the extracellular water fraction, Δ

ƒ

_w^EC, changes in the water balance index, Δ

Q, and combinations thereof.

38. A method according to claim 31 further comprising exhibiting the whole-body extracellular water metric on a display.

39. A method according to claim 31, wherein the first and second tissue sites are two different locations within a single, contiguous organ.

40. A method according to claim 31, wherein the first and second tissue sites are located within different organs.

41. A method according to claim 31, wherein the first tissue site has a different hydrostatic pressure than the second tissue site.

42. A method according to claim 41, wherein the first tissue site is at the same location in the tissue as the second tissue site.

43. A method according to claim 41, wherein the subject is a mammal.

44. A method according to claim 43, wherein the mammal is a human.

45. A method according to claim 31 further comprising (a) excising from the subject the first tissue site before the assessing, (b) excising from the subject the second tissue site before the assessing, or (c) excising from the subject both the first tissue site and the second tissue site before the assessing.

49. A method according to claim 44, wherein the first optical signal comprises at least one wavelength selected from the group of wavelengths consisting of 950- 1400 nm, 1500-1800 nm, and 2000-2300 nm.

46. A method for assessing changes in extracellular fluid volume, said method comprising:

measuring a first optical signal received by an optical detector at a tissue site having a first hydrostatic pressure;

measuring a second optical signal received by an optical detector at a tissue site having a second hydrostatic pressure;

estimating fluid content from the first and second sets of optical signals; and

determining the relationship of said fluid-content estimates to the differences in hydrostatic pressure and estimating changes in extracellular fluid volume from said relationship.

47. The method according to claim 46, wherein the first and second optical signals are independently selected from the group of optical signals consisting of reflectance, transmittance, and absorption.

48. A method according to claim 46 further comprising exhibiting the changes in extracellular fluid volume on a display.

50. A method according to claim 46, wherein the second optical signal comprises at least one wavelength selected from the group of wavelengths consisting of 950- 1400 nm, 1500-1800 nm, and 2000-2300 nm.

51. A method according to claim 46, wherein the tissue site having a first hydrostatic pressure and the tissue site having a second hydrostatic pressure are located at two different sites within a single, contiguous organ.

52. A method according to claim 46, wherein the tissue site having a first hydrostatic pressure and the tissue site having a second hydrostatic pressure are located within different organs.

53. A method according to claim 46, wherein the measurements are substantially independent of light scattering variations and temperature variations.

54. A method according to claim 46, wherein the subject is a mammal.

55. A method according to claim 54, wherein the mammal is a human.

56. A method according to claim 46 further comprising (a) excising from the subject the tissue site having a first hydrostatic pressure before the measuring the first optical signal, (b) excising from the subject the tissue site having a second hydrostatic pressure before the measuring the second optical signal, or (c) excising from the subject both the tissue site having a first hydrostatic pressure and the tissue site having a second hydrostatic pressure before the measuring the first and second optical signals.

57. A system for assessing a whole body fluid metric in a subject, said system comprising:

a local fluid content probe configured to assess a local fluid metric at a tissue site of interest;

a local fluid content probe configured to assess a local fluid metric at a tissue reference site; and

a processing device, wherein the processing device is operably coupled to the local fluid content probe configured to assess a local fluid metric at a tissue site of interest, operably coupled to the local fluid content probe configured to assess a local fluid metric at a tissue reference site, and configured to process a local fluid content metric at a tissue site of interest and a local fluid content metric at a tissue reference site to produce a whole-body fluid content metric.

58. A system according to claim 57 further comprising a tissue compressor configured to alter the hydrostatic pressure of a tissue site of interest, alter the hydrostatic pressure of a tissue reference site, or alter the hydrostatic pressure of both a tissue site of interest and a tissue reference site.

59. A system according to claim 57 further comprising a bioimpedance probe.

60. A system according to claim 57 further comprising an optical spectrophotometry probe.

61. A system according to claim 57, wherein at least a portion of the system is configured to be sterile, sanitizable, disposable, replaceable, or repairable.

62. A system for assessing an extracellular fluid metric in a subject, said system comprising:

a local fluid content probe configured to assess a local fluid content metric at a tissue site;

a location information sensor configured to assess location information of the probe, the tissue site of interest, or the probe and the tissue site of interest; and

a processor, wherein the processor is operably coupled to the local fluid content probe, operably coupled to the location information processor, and configured to process a local fluid content metric and location information to produce an extracellular fluid metric.

63. A probe for assessing a body fluid metric, said probe comprising:

a probe housing configured to be placed proximal to a tissue site of interest and having at least one sanitized surface;

a near infrared light emission fiber optic cable connected to the probe housing and configured to conduct radiation of at least one wavelength to the tissue location;

a near infrared light detection fiber optic cable connected to the probe housing and configured to receive at least one wavelength of radiation from the tissue location; and

a tissue compressor configured to alter the hydrostatic pressure of a tissue site of interest, alter the hydrostatic pressure of a tissue reference site, or alter the hydrostatic pressure of both a tissue site of interest and a tissue reference site.

64. A probe according to claim 63, wherein the probe is configured to be disposable.

65. A probe according to claim 63 further comprising a processing device configured to process radiation from the light emission fiber optic cable, radiation from the light detection fiber optic cable, and location information from the location information sensor to produce a body fluid-related metric.

66. A system for assessing an extracellular fluid content metric, said system comprising:

a means for assessing a fluid content metric at a tissue site at a first hydrostatic pressure;

a means for assessing a fluid content metric at a tissue site at a second hydrostatic pressure; and

a means for processing the fluid content metric at the tissue site at the first hydrostatic pressure and the fluid content metric at the tissue site at the second hydrostatic pressure to produce an extracellular fluid content metric.