CA2441017A1 - Method and apparatus for improving the accuracy of noninvasive hematocrit measurements - Google Patents
Method and apparatus for improving the accuracy of noninvasive hematocrit measurements Download PDFInfo
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- CA2441017A1 CA2441017A1 CA002441017A CA2441017A CA2441017A1 CA 2441017 A1 CA2441017 A1 CA 2441017A1 CA 002441017 A CA002441017 A CA 002441017A CA 2441017 A CA2441017 A CA 2441017A CA 2441017 A1 CA2441017 A1 CA 2441017A1
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- 238000005259 measurement Methods 0.000 title claims abstract 28
- 238000005534 hematocrit Methods 0.000 title claims abstract 25
- 238000000034 method Methods 0.000 title claims abstract 13
- 239000008280 blood Substances 0.000 claims abstract 28
- 210000004369 blood Anatomy 0.000 claims abstract 28
- 102000001554 Hemoglobins Human genes 0.000 claims abstract 18
- 108010054147 Hemoglobins Proteins 0.000 claims abstract 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract 14
- 239000012223 aqueous fraction Substances 0.000 claims abstract 8
- 230000005855 radiation Effects 0.000 claims 18
- 238000010521 absorption reaction Methods 0.000 claims 16
- 230000003287 optical effect Effects 0.000 claims 16
- 238000001228 spectrum Methods 0.000 claims 12
- 238000001514 detection method Methods 0.000 claims 10
- 239000000523 sample Substances 0.000 claims 7
- 239000006096 absorbing agent Substances 0.000 claims 4
- 108010058237 plasma protein fraction Proteins 0.000 claims 4
- 229940081857 plasma protein fraction Drugs 0.000 claims 4
- 238000002798 spectrophotometry method Methods 0.000 claims 4
- 206010058990 Venous occlusion Diseases 0.000 claims 3
- 230000001678 irradiating effect Effects 0.000 claims 3
- 230000023077 detection of light stimulus Effects 0.000 claims 2
- 230000010349 pulsation Effects 0.000 claims 2
- 230000002792 vascular Effects 0.000 claims 2
- 230000008320 venous blood flow Effects 0.000 claims 2
- 239000013307 optical fiber Substances 0.000 claims 1
- 210000004204 blood vessel Anatomy 0.000 abstract 1
- 238000000985 reflectance spectrum Methods 0.000 abstract 1
- 238000002834 transmittance Methods 0.000 abstract 1
Classifications
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
- A61B5/6813—Specially adapted to be attached to a specific body part
- A61B5/6825—Hand
- A61B5/6826—Finger
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/14535—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring haematocrit
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
- A61B5/14546—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring analytes not otherwise provided for, e.g. ions, cytochromes
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
- A61B5/683—Means for maintaining contact with the body
- A61B5/6838—Clamps or clips
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
- G01N21/35—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light
- G01N21/359—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry using infrared light using near infrared light
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
- G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
- G01N33/72—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving blood pigments, e.g. haemoglobin, bilirubin or other porphyrins; involving occult blood
- G01N33/721—Haemoglobin
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
- A61B5/021—Measuring pressure in heart or blood vessels
- A61B5/022—Measuring pressure in heart or blood vessels by applying pressure to close blood vessels, e.g. against the skin; Ophthalmodynamometers
Abstract
A device and a method to provide a more reliable and accurate measurement of hematocrit (Hct) by noninvasive means. The changes in the intensities of lig ht of multiple wavelengths transmitted through or reflected light from the tiss ue location are recorded immediately before and after occluding the flow of venous blood from the tissue location with an occlusion device positioned ne ar the tissue location. As the venous return stops and the incoming arterial blood expands the blood vessels, the light intensities measured within a particular band of near-infrared wavelengths decrease in proportion to the volume of hemoglobin in the tissue location; those intensities measured with in a separate band of wavelengths in which water absorbs respond to the difference between the water fractions within the blood and the displaced tissue volume. A mathematical algorithm applied to the time-varying intensities yields a quantitative estimate of the absolute concentration of hemoglobin in the blood. To compensate for the effect of the unknown fractio n of water in the extravascular tissue on the Hct measurement, the tissue wate r fraction is determined before the occlusion cycle begins by measuring the diffuse transmittance or reflectance spectra of the tissue at selected wavelengths.
Claims (27)
1. A device for measuring hematocrit values using optical spectrophotometry comprising:
a probe housing configured to be placed proximal to a tissue location which is being monitored;
an occlusion device connected to said housing and configured to magnify the fractional change in the vascular blood volume to a value greater than said fractional change produced by normal arterial pulsations;
light emission optics connected to said housing and configured to direct radiation at said tissue location;
light detection optics connected to said housing and configured to receive radiation from said tissue location;
a processing device connected to said housing and configured to process radiation from said light emission optics and said light detection optics to compute said hematocrit values.
a probe housing configured to be placed proximal to a tissue location which is being monitored;
an occlusion device connected to said housing and configured to magnify the fractional change in the vascular blood volume to a value greater than said fractional change produced by normal arterial pulsations;
light emission optics connected to said housing and configured to direct radiation at said tissue location;
light detection optics connected to said housing and configured to receive radiation from said tissue location;
a processing device connected to said housing and configured to process radiation from said light emission optics and said light detection optics to compute said hematocrit values.
2. The device of claim 1, further comprising a display device connected to said probe housing and configured to display said hematocrit values.
3. The device of claim 1, further comprising means for measuring hemoglobin.
4. The device of claim 1, further comprising a pressure transducer connected to said housing and positioned to be placed adjacent to said tissue location, and configured to interface with said processing device and said occlusion device to provide an input to said processing device to control the timing of the data acquisition by said processing device.
5. The device of claim 1, wherein said light emission optics axe tuned to emit radiation at at least a first and a second wavelength, where said at least first wavelength is within a band of wavelengths where hemoglobin is the dominant absorber and where said at least second wavelength is within a band of wavelengths where water is the dominant absorber.
6. The device of claim 1, wherein said light emission optics are tuned to emit radiation at at least a first and a second wavelength, where said at least first wavelength is within a band of wavelengths in the range of approximately 800-1000 nm and where said at least second wavelength is within a band in the range of approximately 1250-1600 nm.
7. The device of claim 1, wherein said light emission optics are tuned to emit radiation at at least a first and a second wavelength, where said first and said second wavelengths are related to each other such that 0.34Hµ,a b » p,a at said first wavelengths and µ~,a » 0.34Hp,a b at said second wavelength, where H is the hematocrit value, µa b is the sum of the absorption coefficient of the two forms of hemoglobin, and µ4 is the absorption coefficient of water.
8. The device of claim 1, wherein said light emission optics are tuned to emit radiation at at least a first and a second wavelength, where said at least first wavelength is in a range approximately between and including 805 to 850 nm and said at least second wavelength is in a range approximately between and including 1310 to 1370.
nm.
nm.
9. The device of claim 1, wherein said light emission optics and said light detection optics are mounted within said probe housing and positioned with appropriate alignment to enable detection in a transmissive mode.
10. The device of claim 1, wherein said light emission optics and said light detection optics are mounted within said probe housing and positioned with appropriate alignment to enable detection in a reflective mode.
11. The device of claim 1, wherein said light emission optics and said light detection optics are placed within a remote unit and which deliver light to and receive light from said probe housing via optical fibers.
12. The device of claim 1, wherein said light emission optics comprise at least one of a (a) incandescent light source, (b) narrowband light source, wherein a narrowband light source comprises one of a light emitting diode ("LED") and a filtered white light source.
13, The device of claim 1, wherein said processing device receives at least two sets of optical measurements, where the at least first set of optical measurements corresponds to the detection of light whose absorption is primarily due to hemoglobin, and where the at least second set of optical measurements corresponds to the detection of light whose absorption is primarily due to water, and where a combination of said at least two sets of optical measurements provides a measure of said hematocrit value.
14. The device of claim 1, wherein said processing device:
receives at least two sets of optical measurements at an at least a first and a second wavelength, where for each wavelength two optical measurements are obtained corresponding to measurements before and after a venous occlusion conducted by said occlusion device to obtain before and after occlusion measurements at each wavelength;
combines said before and after occlusion measurements at each wavelength to determine a blood pulse spectrum at each wavelength;
combines said blood pulse spectra at each wavelength to obtain a ratio of said blood pulse spectra; and combines said ratio with measurements of tissue water fractions to determines the concentration of hemoglobin in the blood.
receives at least two sets of optical measurements at an at least a first and a second wavelength, where for each wavelength two optical measurements are obtained corresponding to measurements before and after a venous occlusion conducted by said occlusion device to obtain before and after occlusion measurements at each wavelength;
combines said before and after occlusion measurements at each wavelength to determine a blood pulse spectrum at each wavelength;
combines said blood pulse spectra at each wavelength to obtain a ratio of said blood pulse spectra; and combines said ratio with measurements of tissue water fractions to determines the concentration of hemoglobin in the blood.
15. The device of claim 1, wherein said processing device determines hematocrit based on optical measurements such that H is the hematocrit value;
fw is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µHb (.lambda.~) is the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µw a(.lambda.2 ) is the absorption coefficient of water at a second wavelength;
O,us (~, ) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
.DELTA.µs (.lambda.1 ) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
fw is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µHb (.lambda.~) is the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µw a(.lambda.2 ) is the absorption coefficient of water at a second wavelength;
O,us (~, ) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
.DELTA.µs (.lambda.1 ) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
16. A device for measuring hematocrit values using optical spectrophotometry comprising:
a probe housing configured to be placed proximal to a tissue location which is being monitored;
an occlusion device connected to said housing and configured to magnify the fractional change in the vascular blood volume to a value greater than said fractional change produced by normal arterial pulsations;
light emission optics connected to said housing and configured to direct radiation at said tissue location, wherein said light emission optics comprise at least one of a (a) incandescent light source, (b) white light source and (c) light emitting diodes ("LEDs") which are tuned to emit radiation at at least a first and a second wavelength, where said at least first wavelength is within a band of wavelengths where hemoglobin is the dominant absorber and where said at least second wavelength is within a band where water is the dominant absorber;
a photodiode connected to said housing and configured to receive radiation from said tissue location;
a processing device connected to said housing and configured to process radiation from said light emission optics and said light detection optics to compute said hematocrit values, wherein said processing device:
receives at least two sets of optical measurements at an at least a first and a second wavelength, where for each wavelength two optical measurements are obtained corresponding to measurements before and after a venous occlusion conducted by said occlusion device, to obtain before and after occlusion measurements at each wavelength;
combines said before and after measurements at each wavelength to determine a blood pulse spectrum at each wavelength;
combines said blood pulse spectra at each wavelength to obtain a ratio of said blood pulse spectra;
combines said ratio with measurements of tissue water fractions to determines the blood hematocrit value, such that H is the hematocrit value;
fW is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µ Hb a (.lambda.1) is the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µw a (.lambda.2) is the absorption coefficient of water at a second wavelength;
.DELTA. µs (.lambda.1) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
.DELTA. µ s(.lambda.2) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
a probe housing configured to be placed proximal to a tissue location which is being monitored;
an occlusion device connected to said housing and configured to magnify the fractional change in the vascular blood volume to a value greater than said fractional change produced by normal arterial pulsations;
light emission optics connected to said housing and configured to direct radiation at said tissue location, wherein said light emission optics comprise at least one of a (a) incandescent light source, (b) white light source and (c) light emitting diodes ("LEDs") which are tuned to emit radiation at at least a first and a second wavelength, where said at least first wavelength is within a band of wavelengths where hemoglobin is the dominant absorber and where said at least second wavelength is within a band where water is the dominant absorber;
a photodiode connected to said housing and configured to receive radiation from said tissue location;
a processing device connected to said housing and configured to process radiation from said light emission optics and said light detection optics to compute said hematocrit values, wherein said processing device:
receives at least two sets of optical measurements at an at least a first and a second wavelength, where for each wavelength two optical measurements are obtained corresponding to measurements before and after a venous occlusion conducted by said occlusion device, to obtain before and after occlusion measurements at each wavelength;
combines said before and after measurements at each wavelength to determine a blood pulse spectrum at each wavelength;
combines said blood pulse spectra at each wavelength to obtain a ratio of said blood pulse spectra;
combines said ratio with measurements of tissue water fractions to determines the blood hematocrit value, such that H is the hematocrit value;
fW is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µ Hb a (.lambda.1) is the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µw a (.lambda.2) is the absorption coefficient of water at a second wavelength;
.DELTA. µs (.lambda.1) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
.DELTA. µ s(.lambda.2) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
17. The device of claim 16, further comprising a pressure transducer connected to said housing and positioned to be placed adjacent to said tissue location, and configured to interface with said processing device and said occlusion device to provide an input to said processing device to control the timing of the data acquisition by said processing device.
18. The device of claim 16, wherein said light emission optics are tuned to emit radiation at at least a first and a second wavelength, where said at least first wavelength is within a band of wavelengths in the range of approximately 800-1000 mn and where said at least second wavelength is within a band in the range of approximately 1250-1600 nm.
19 19. A method of measuring a percent hematocrit near a tissue location using optical spectrophotometry comprising:
placing a probe housing proximal to said tissue location;
occluding the venous blood flow adjacent to said tissue location;
emitting radiation at at least two wavelengths using light emission optics configured to direct radiation at said tissue location;
detecting radiation using light detection optics configured to receive radiation from said tissue location;
processing said radiation from said light emission and said light detection optics using a processing device;
computing said percent hematocrit, where said percent hematocrit is determined by:
receiving at least two sets of optical measurements at an at least a first and a second wavelength, where for each wavelength two optical measurements are obtained corresponding to measurements before and after a venous occlusion, to obtain before and after occlusion measurements at each wavelength;
combining said before and after measurements at each wavelength;
determining a blood pulse spectrum at each wavelength;
obtaining a ratio of said blood pulse spectra;
combining said ratio with measurements of tissue water fractions; and determining said percent hematocrit value such that H is the hematocrit value;
fw is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µ Hb a (.lambda.1) is the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µ w a(.lambda.2) is the absorption coefficient of water at a second wavelength;
~,us (02, ) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
placing a probe housing proximal to said tissue location;
occluding the venous blood flow adjacent to said tissue location;
emitting radiation at at least two wavelengths using light emission optics configured to direct radiation at said tissue location;
detecting radiation using light detection optics configured to receive radiation from said tissue location;
processing said radiation from said light emission and said light detection optics using a processing device;
computing said percent hematocrit, where said percent hematocrit is determined by:
receiving at least two sets of optical measurements at an at least a first and a second wavelength, where for each wavelength two optical measurements are obtained corresponding to measurements before and after a venous occlusion, to obtain before and after occlusion measurements at each wavelength;
combining said before and after measurements at each wavelength;
determining a blood pulse spectrum at each wavelength;
obtaining a ratio of said blood pulse spectra;
combining said ratio with measurements of tissue water fractions; and determining said percent hematocrit value such that H is the hematocrit value;
fw is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µ Hb a (.lambda.1) is the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µ w a(.lambda.2) is the absorption coefficient of water at a second wavelength;
~,us (02, ) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
20 .DELTA.µ (.lambda.2 ) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
20. The method of claim 19, wherein said first wavelength is chosen from within a band of wavelengths in the range of approximately 800-1000 nm and where said second wavelength is chosen from within a band of wavelengths in the range of approximately 1350-1600 nm.
20. The method of claim 19, wherein said first wavelength is chosen from within a band of wavelengths in the range of approximately 800-1000 nm and where said second wavelength is chosen from within a band of wavelengths in the range of approximately 1350-1600 nm.
21. The method of claim 19, wherein said first and said second wavelengths are related to each other such that 0.34Hµa Hb » µ wa at said first wavelengths and µ w a » 0.34Hµ a Hb at said second wavelength, where H is the hematocrit value, µ Hb a is the sum of the absorption coefficient of the two forms of hemoglobin, and µ w a is the absorption coefficient of water.
22. The method of claim 19, wherein said first and second wavelengths are approximately between and including 805 to 850 nm and approximately between and including 1310 to 1370 nm respectively.
23. A method of computing percent hematocrit based on optical measurements, wherein said percent hematocrit is determined such that H is the hematocrit value;
fW is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µ Hb a (.lambda.1) is. the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µ w a (.lambda.2) is the absorption coefficient of water at a second wavelength;
.DELTA.µ (.lambda.1) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
.DELTA.µ (.lambda.2) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
fW is the tissue water fraction;
fpp is the plasma protein fraction;
R is the ratio of magnitudes of the blood pulse spectrum;
µ Hb a (.lambda.1) is. the sum of the absorption coefficient of the two forms of hemoglobin at a first wavelength;
µ w a (.lambda.2) is the absorption coefficient of water at a second wavelength;
.DELTA.µ (.lambda.1) is the difference between the scattering coefficients of the blood and surrounding tissue at a first wavelength;
.DELTA.µ (.lambda.2) is the difference between the scattering coefficients of the blood and surrounding tissue at a second wavelength; and 0.34 is the fraction of the red cell volume occupied by hemoglobin, which is assumed to be constant.
24. The method of claim 23, wherein said first wavelength is chosen from within a band of wavelengths in the range of approximately 800-1000 nm and where said second wavelength is chosen from within a band of wavelengths in the range of approximately 1350-1600 nm.
25. The method of claim 23, wherein said first and said second wavelengths are related to each other such that 0.34H µ,a Hb » µ wa at said first wavelengths and µ wa » 0.34Hµ a Hb at said second wavelength, where H is the hematocrit value, µ w a is the sum of the absorption coefficient of the two forms of hemoglobin, and µ w a is the absorption coefficient of water.
26. The method of claim 23, wherein said first and second wavelengths axe approximately between and including 805 to 850 nm and approximately between and including 1310 to 1370 nm respectively.
27. A method of measuring a percent hematocrit near a tissue location using optical spectrophotometry comprising:
irradiating said tissue location and processing received signals from said tissue location to measure tissue water;
occluding the venous blood flow adjacent to said tissue location;
repeat irradiating said tissue location;
detecting radiation from said tissue following said repeat irradiating; and calculating hematocrit values using tissue water measurements.
irradiating said tissue location and processing received signals from said tissue location to measure tissue water;
occluding the venous blood flow adjacent to said tissue location;
repeat irradiating said tissue location;
detecting radiation from said tissue following said repeat irradiating; and calculating hematocrit values using tissue water measurements.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US09/811,328 | 2001-03-16 | ||
US09/811,328 US6606509B2 (en) | 2001-03-16 | 2001-03-16 | Method and apparatus for improving the accuracy of noninvasive hematocrit measurements |
PCT/US2002/007760 WO2002075289A2 (en) | 2001-03-16 | 2002-03-13 | Method and apparatus for improving the accuracy of noninvasive hematocrit measurements |
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CA2441017A1 true CA2441017A1 (en) | 2002-09-26 |
CA2441017C CA2441017C (en) | 2011-07-12 |
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CA2441017A Expired - Fee Related CA2441017C (en) | 2001-03-16 | 2002-03-13 | Method and apparatus for improving the accuracy of noninvasive hematocrit measurements |
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US (1) | US6606509B2 (en) |
EP (1) | EP1368638B1 (en) |
JP (1) | JP4176480B2 (en) |
CA (1) | CA2441017C (en) |
DE (1) | DE60223787T2 (en) |
ES (1) | ES2299558T3 (en) |
HK (1) | HK1063072A1 (en) |
WO (1) | WO2002075289A2 (en) |
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US5638816A (en) * | 1995-06-07 | 1997-06-17 | Masimo Corporation | Active pulse blood constituent monitoring |
US5853364A (en) | 1995-08-07 | 1998-12-29 | Nellcor Puritan Bennett, Inc. | Method and apparatus for estimating physiological parameters using model-based adaptive filtering |
US5827181A (en) | 1995-09-07 | 1998-10-27 | Hewlett-Packard Co. | Noninvasive blood chemistry measurement method and system |
US6064898A (en) * | 1998-09-21 | 2000-05-16 | Essential Medical Devices | Non-invasive blood component analyzer |
US6402690B1 (en) * | 1999-04-23 | 2002-06-11 | Massachusetts Institute Of Technology | Isolating ring sensor design |
US6400971B1 (en) * | 1999-10-12 | 2002-06-04 | Orsense Ltd. | Optical device for non-invasive measurement of blood-related signals and a finger holder therefor |
-
2001
- 2001-03-16 US US09/811,328 patent/US6606509B2/en not_active Expired - Lifetime
-
2002
- 2002-03-13 WO PCT/US2002/007760 patent/WO2002075289A2/en active IP Right Grant
- 2002-03-13 CA CA2441017A patent/CA2441017C/en not_active Expired - Fee Related
- 2002-03-13 JP JP2002573656A patent/JP4176480B2/en not_active Expired - Fee Related
- 2002-03-13 ES ES02709832T patent/ES2299558T3/en not_active Expired - Lifetime
- 2002-03-13 EP EP02709832A patent/EP1368638B1/en not_active Expired - Lifetime
- 2002-03-13 DE DE60223787T patent/DE60223787T2/en not_active Expired - Lifetime
-
2004
- 2004-06-10 HK HK04104183A patent/HK1063072A1/en not_active IP Right Cessation
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JP4176480B2 (en) | 2008-11-05 |
EP1368638A2 (en) | 2003-12-10 |
US6606509B2 (en) | 2003-08-12 |
EP1368638B1 (en) | 2007-11-28 |
HK1063072A1 (en) | 2004-12-10 |
US20020165439A1 (en) | 2002-11-07 |
DE60223787D1 (en) | 2008-01-10 |
JP2004523320A (en) | 2004-08-05 |
CA2441017C (en) | 2011-07-12 |
DE60223787T2 (en) | 2008-11-27 |
ES2299558T3 (en) | 2008-06-01 |
WO2002075289A2 (en) | 2002-09-26 |
WO2002075289A3 (en) | 2002-11-21 |
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