Device and method for monitoring body fluid and electrolyte disorders

• US 8,229,529 B2
• Filed: 09/30/2005
• Issued: 07/24/2012
• Est. Priority Date: 03/16/2001
• Status: Expired due to Fees

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett LLC (Medtronic Plc)
• Inventors: Schmitt, Joseph M.
• Primary Examiner(s): Chen, Tse
• Assistant Examiner(s): CHAO, ELMER M
• Application Number:
  US11/240,927
• Publication Number:
  US 20060020181A1
• Time in Patent Office: 2,489 Days
• Field of Search: 600/310, 600/306, 600/307, 600/476, 600/407, 600/551, 356/320
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0053 by applying pressure, e.g. compression, indentation, palpation, grasping, gauging
• 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 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/4878 Evaluating oedema
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

A device and a method for measuring body fluid-related metrics using spectrophotometry to facilitate therapeutic interventions aimed at restoring body fluid balance. The specific body fluid-related metrics include the absolute volume fraction of water in the extravascular and intravascular tissue compartments, as well as the shifts of water between these two compartments. The absolute volume fraction of water is determined using algorithms where received radiation measured at two or more wavelengths are combined to form either a single ratio, a sum of ratios or ratio of ratios, in which the received radiation in the numerator depends primarily on the absorbance of water and the received radiation in the denominator depends primarily on the absorbance of water and the sum of the absorbances of non-herne proteins, lipids and water in tissue. The difference between the fraction of water in the intravascular fluid volume and extravascular fluid volume compartments are also determined.

Claims

1. A device for determining body fluid-related metrics, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the body fluid-related metrics, wherein the body fluid-related metrics comprise absolute volume fractions of water in extravascular and intravascular bodily tissue compartments and differences between intravascular fluid volume and extravascular fluid volume fractions.

2. The device of claim 1, comprising a display device coupled to the processing device and configured to display the body fluid-related metrics.

3. The device of claim 1, wherein the processing device receives and compares at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of the optical radiation whose absorption is primarily due to water, lipids and non-heme proteins, and where the at least second set of optical measurements corresponds to the detection of the optical radiation whose absorption is primarily due to water, and where a comparison of the at least two optical measurements provides a measure of the absolute water fraction within the tissue location.

4. The device of claim 1, wherein the processing device receives and compares at least two sets of optical measurements, where the at least two sets of optical measurements are based on the received optical radiation from at least two wavelengths and which are combined to form either a single ratio of the received optical radiation, a sum of ratios of the received optical radiation, or ratios of ratios of the received optical radiation.

5. The device of claim 1, wherein the processing device receives and compares at least two sets of optical measurements from at least two different wavelengths, where absorption of light at the at least two different wavelengths is primarily due to water which is in vascular blood and in extravascular tissue, and where a ratio of the at least two measurements provides a measure of a difference between fractions of water in the blood and the tissue location.

6. A device for determining body fluid-related metrics, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the body fluid-related metrics, the body fluid-related metrics comprising percent body water and a water balance, where the water balance is an integrated difference between a water fraction in blood and a water fraction in extravascular tissue.

7. A device for determining an absolute volume fraction of water within human tissue, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the absolute volume fraction of water, wherein the processing device receives and compares at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of the optical radiation whose absorption is primarily due to water, lipids and non-heme proteins, and where the at least second set of optical measurements corresponds to the detection of the optical radiation whose absorption is primary due to water, and where a comparison of the at least two optical measurements provides a measure of the absolute volume water fraction within the tissue location.

8. A device for determining a difference between an intravascular fluid volume and an extravascular fluid volume, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the difference between an intravascular fluid volume and an extravascular fluid volume, wherein the processing device receives and compares at least two sets of optical measurements from at least two different wavelengths, where absorption of light at the at least two different wavelengths is primarily due to water that is in vascular blood and in extravascular tissue, and where a comparison of the at least two measurements provides a measure of a difference between the fractions of water in the blood and the tissue location.

9. A method for determining body fluid-related metrics in a human tissue location, the method comprising:

processing a signal indicative of optical radiation received from the tissue location to compute the body fluid-related metrics via a processing device of a fluid monitor, wherein the body fluid-related metrics comprise absolute volume fractions of water in extravascular and intravascular bodily tissue compartments and differences between intravascular fluid volume and extravascular fluid volume fraction, wherein the processing comprises;

measuring at least two sets of optical measurements based on received optical radiation of at least two wavelengths;

combining the at least two sets of optical measurements to form either a single ratio of the received optical radiation, a sum of ratios of the received optical radiation, or ratios of ratios of the received optical radiation to form combinations of received optical radiation; and

determining the metrics from the combinations.

10. A device for determining body fluid-related metrics, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the body fluid-related metrics, wherein the optical radiation comprises a plurality of spectral wavelengths chosen to be preferentially absorbed by tissue water, non-heme proteins and lipids, where preferentially absorbed wavelengths are wavelengths whose absorption is substantially independent of individual concentrations of non-heme proteins and lipids, and is substantially dependent on a sum of the individual concentrations of non-heme proteins and lipids.

11. The device of claim 10, wherein the processing device is configured to process wavelengths chosen to ensure that the received optical radiation is substantially insensitive to scattering variations and such that the optical path lengths through a dermis portion of the tissue location at the wavelengths are substantially equal.

12. The device of claim 10, wherein the processing device is configured to process wavelengths chosen to ensure that the received optical radiation from the tissue location is insensitive to temperature variations, where the wavelengths are temperature isosbestic in the water absorption spectrum or individual wavelengths of the received optical radiation are combined in a way that substantially cancels temperature dependencies of the individual wavelengths of the received optical radiation when computing tissue water fractions.

13. The device of claim 10, wherein the processing device is configured to process wavelengths chosen from one of three primary bands of wavelengths of approximately 1100-1350 nm, approximately 1500-1800 nm, and approximately 2000-2300 nm.

14. The device of claim 10, wherein the processing device receives and compares at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of the optical radiation whose absorption is primarily due to water, lipids and non-heme proteins, and where the at least second set of optical measurements corresponds to the detection of the optical radiation whose absorption is primarily due to water, and where a comparison of the at least two optical measurements provides a measure of the absolute water fraction within the tissue location.

15. The device of claim 10, wherein the processing device receives and compares at least two sets of optical measurements, where the at least two sets of optical measurements are based on the received optical radiation from at least two wavelengths and which are combined to form either a single ratio of the received optical radiation, a sum of ratios of the received optical radiation, or ratios of ratios of the received optical radiation.

16. The device of claim 10, wherein the processing device receives and compares at least two sets of optical measurements from at least two different wavelengths, where absorption of light at the at least two different wavelengths is primarily due to water which is in vascular blood and in extravascular tissue, and where a ratio of the at least two measurements provides a measure of a difference between fractions of water in the blood and the tissue location.

17. The device of claim 10, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, where the tissue water fraction (f_w) is determined such that

f_w=c₁ log [R(λ

₁)/R(λ

₂)]+c₀, and where;

calibration constants c₀ and c₁ are chosen empirically

R(λ

₁) is the received optical radiation at a first wavelength; and

R(λ

₂) is the received optical radiation at a second wavelength.

18. The device of claim 17, wherein the processing device is configured to process first and second wavelengths that are approximately 1300 nm and approximately 1168 nm, respectively.

19. The device of claim 17, wherein the processing device is configured to process first and second wavelengths that are approximately 1230 nm and approximately 1168 nm, respectively.

20. The device of claim 10, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

f_w=c₂ log [R(λ

₁)/R(λ

₂)]+c₁ log [R(λ

₂)/R(λ

₃)]+c₀, and where;

calibration constants c₀, c₁ and c₂ are chosen empirically;

R(λ

₁) is the received optical radiation at a first wavelength;

R(λ

₂) is the received optical radiation at a second wavelength; and

R(λ

₃) is the received optical radiation at a third wavelength.

21. The device of claim 10, wherein the processing device is configured to process first, second and third wavelengths that are approximately 1190 nm, approximately 1170 nm and approximately 1274 nm, respectively.

22. The device of claim 10, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

23. The device of claim 22, wherein the processing device is configured to process first, second and third wavelengths that are approximately 1710 nm, approximately 1730 nm and approximately 1740 nm, respectively.

24. The device of claim 10, wherein the processing device is configured to compute body fluid-related metrics that comprise a quantified measure of a difference between a water fraction in blood and a water fraction in extravascular tissue, where the difference is determined such that

25. The device of claim 24, wherein the processing device is configured to compute body fluid metrics that comprise an integral of the difference between the water fraction in the blood and the water fraction in the extravascular tissue to provide a measure of water that shifts into and out of capillaries in the tissue location.

26. The device of claim 24, wherein the processing device is configured to process first and second wavelengths that comprise approximately 1320 nm and approximately 1160 nm, respectively.

27. A device for determining body fluid-related metrics, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the body fluid-related metrics, wherein the body fluid-related metrics comprises a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

28. The device of claim 27, wherein the processing device is configured to process wavelengths chosen to ensure that the received optical radiation is substantially insensitive to scattering variations and such that the optical path lengths through a dermis portion of the tissue location at the wavelengths are substantially equal.

29. The device of claim 27, wherein the processing device is configured to process wavelengths chosen to ensure that the received optical radiation from the tissue location is substantially insensitive to temperature variations, where the wavelengths of the optical radiation are temperature isosbestic in the water absorption spectrum or where the wavelengths of the received optical radiation are combined in a way that substantially cancels temperature dependencies of individual wavelengths of the received optical radiation when computing tissue water fractions.

30. The device of claim 27, wherein the processing device is configured to process wavelengths chosen from one of three primary bands of wavelengths of approximately 1100-1350 nm, approximately 1500-1800 nm, and approximately 2000-2300 nm.

31. The device of claim 27, wherein the processing device receives and compares at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of the received optical radiation whose absorption is primarily due to water, lipids and non-heme proteins, and where the at least second set of optical measurements corresponds to the detection of the received optical radiation whose absorption is primarily due to water, and where a comparison of the at least two optical measurements provides a measure of the absolute water fraction within the tissue location.

32. The device of claim 27, wherein the processing device is configured to process first, second and third wavelengths that are approximately 1710 nm, approximately 1730 nm and approximately 1740 nm, respectively.

33. A device for determining body fluid-related metrics, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location to compute the body fluid-related metrics, wherein received optical radiation comprises a plurality of spectral wavelengths chosen to ensure that the computed body fluid-related metrics are substantially insensitive to scattering variations and such that the optical path lengths through the tissue location at the wavelengths are substantially equal.

34. The device of claim 33, wherein the processing device is configured to process wavelengths chosen to ensure that the received optical radiation from the tissue location is substantially insensitive to temperature variations, where wavelengths of the received optical radiation are temperature isosbestic in the water absorption spectrum, or where wavelengths of the received optical radiation are combined in a way that substantially cancel temperature dependencies of any individual wavelength of the received optical radiation when computing tissue water fractions.

35. The device of claim 33, wherein the processing device is configured to process wavelengths of the received optical radiation are chosen from one of three primary bands of wavelengths of approximately 1100-1350 nm, approximately 1500-1800 nm, and approximately 2000-2300 nm.

36. The device of claim 33, wherein the processing device receives and compares at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of the received optical radiation whose absorption is primarily due to water, lipids and non-heme proteins, and where the at least second set of optical measurements corresponds to the detection of the received optical radiation whose absorption is primarily due to water, and where a comparison of the at least two optical measurements provides a measure of the absolute water fraction within the tissue location.

37. The device of claim 33, wherein the processing device receives and compares at least two sets of optical measurements, where the at least two sets of optical measurements are based on the received optical radiation from at least two wavelengths and which are combined to form either a single ratio of the received optical radiation, a sum of ratios of the received optical radiation, or ratios of ratios of the received optical radiation.

38. The device of claim 33, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

f_w=c₁ log [R(λ

₁)/R(λ

₂)]+c₀, and where;

calibration constants c₀ and c₁ are chosen empirically;

R(λ

₁) is the received optical radiation at a first wavelength; and

R(λ

₂) is the received optical radiation at a second wavelength.

39. The device of claim 38, wherein the processing device is configured to process first and second wavelengths that are approximately 1300 nm and approximately 1168 nm, respectively.

40. The device of claim 38, wherein the processing device is configured to process first and second wavelengths that are approximately 1230 nm and approximately 1168 nm, respectively.

41. The device of claim 33, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

f_w=c₂ log [R(λ

₁)/R(λ

₂)]+c₁ log [R(λ

₂)/R(λ

₃)]+c₀, and where;

calibration constants c₀, c₁ and c₂ are chosen empirically;

R(λ

₁) is the received optical radiation at a first wavelength;

R(λ

₂) is the received optical radiation at a second wavelength; and

R(λ

₃) is the received optical radiation at a third wavelength.

42. The device of claim 41, wherein the processing device is configured to process first, second and third wavelengths that are approximately 1190 nm, approximately 1170 nm, and approximately 1274 nm, respectively.

43. A device for determining body fluid-related metrics, the device comprising:

a processing device configured to process a signal indicative of optical radiation received from a tissue location compute the body fluid-related metrics, wherein the received optical radiation comprises a plurality of spectral wavelengths chosen to ensure that the received optical radiation from the tissue location is substantially insensitive to temperature variations, wherein wavelengths of the received optical radiation are temperature isosbestic in the water absorption spectrum or wherein the signal is processed in such a way that temperature dependencies of individual wavelengths of the received optical radiation is substantially cancelled when computing tissue water fractions.

44. The device of claim 43, wherein the processing device is configured to process wavelengths chosen from one of three primary bands of wavelengths of approximately 1100-1350 nm, approximately 1500-1800 nm, and approximately 2000-2300 nm.

45. The device of claim 43, wherein the processing device receives and compares at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of optical radiation whose absorption is primarily due to water, lipids and non-heme proteins, and where the at least second set of optical measurements corresponds to the detection of optical radiation whose absorption is primarily due to water, and where a comparison of the at least two optical measurements provides a measure of the absolute water fraction within the tissue location.

46. The device of claim 43, wherein the processing device receives and compares at least two sets of optical measurements, where the at least two sets of optical measurements are based on the received optical radiation from at least two wavelengths and which are combined to form either a single ratio of the received optical radiation, a sum of ratios of the received optical radiation, or ratios of ratios of the received optical radiation.

47. The device of claim 43, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

f_w=c₁ log [R(λ

₁)/R(λ

₂)]+c₀, and where;

calibration constants c₀ and c₁ are chosen empirically;

R(λ

₁) is the received optical radiation at a first wavelength; and

R(λ

₂) is the received optical radiation at a second wavelength.

48. The device of claim 47, wherein the processing device is configured to process first and second wavelengths that are approximately 1300 nm and approximately 1168 nm, respectively.

49. The device of claim 47, where the processing device is configured to process first and second wavelengths that are approximately 1230 nm and approximately 1168 nm, respectively.

50. The device of claim 43, wherein the processing device is configured to compute body fluid-related metrics that comprise a tissue water fraction, and where the tissue water fraction (f_w) is determined such that

f_w=c₂ log [R(λ

₁)/R(λ

₂)]+c₁ log [R(λ

₂)/R(λ

₃)]+c₀, and where;

calibration constants c₀, c₁ and c₂ are chosen empirically;

R(λ

₁) is the received optical radiation at a first wavelength;

R(λ

₂) is the received optical radiation at a second wavelength; and

R(λ

₃) is the received optical radiation at a third wavelength.

51. The device of claim 50, wherein the processing device is configured to process first, second and third wavelengths that are approximately 1190 nm, approximately 1170 nm, and approximately 1274 nm, respectively.