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US5277181A
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Noninvasive measurement of hematocrit and hemoglobin content by differential optical analysis
Assignee: LOCK J PAUL
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Filing: 1991-12-12
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Granted: 1994-01-11
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Expires: 2011-12-12
Abstract
Abstract The present invention relates to the noninvasive measurement of blood hematocrit and hemoglobin content using differential optical absorption of two or more wavelengths of light during blood volume changes. The method is also useful for noninvasive measurements of other blood analytes, such as glucose, where variations in hematocrit or blood hemoglobin concentration cause errors in the measurement.
Inventors
- 👤 Yitzhak Mendelson
- 👤 Yi Wang
- 👤 Brian D. Gross
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:35
CPC Classifications
A; A61; A61B; A61B5/00; A61B5/145; A61B5/14535; A61B5/1455; A61B5/14551
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
123 words
A noninvasive method of generating a ratio of signals from which measurement of one or more blood parameters in living tissue may be made, comprising the steps of: a) illuminating the tissue with light of a first wavelength λ1 at an incident tissue site, such that the light is scattered and absorbed by the tissue; b) while the volume of blood in the tissue is changing, detecting the scattered light at two separate detection tissue sites remote from said incident site and generating first and second electrical signals proportional to the intensity of the detected light; c) normalizing the first and second electrical signals to produce first and second normalized signals; and d) forming a ratio of the first and second normalized signals.
Claim 2
Dependent Claim
123 words
A noninvasive method of generating a ratio of signals from which measurement of one or more blood parameters in living tissue may be made, comprising the steps of: a) illuminating the tissue with light of a first wavelength λ1 at an incident tissue site, such that the light is scattered and absorbed by the tissue; b) while the volume of blood in the tissue is changing, detecting the scattered light at two separate detection tissue sites remote from said incident site and generating first and second electrical signals proportional to the intensity of the detected light; c) normalizing the first and second electrical signals to produce first and second normalized signals; and d) forming a ratio of the first and second normalized signals.
Claim 3
Dependent Claim
18 words
The method of claim 1 wherein λ1 is about 815 nm and the blood parameter measured is hemoglobin.
Claim 4
Dependent Claim
28 words
The method of claim 1 wherein the volume of blood is changing due to a cardiac cycle, such that the first and second electrical signals represent photoplethysmographic waveforms.
Claim 5
Dependent Claim
27 words
The method of claim 1 wherein the parameter measured is hemoglobin and the wavelength λ1 is a wavelength which is insensitive to all tissue parameters except hemoglobin.
Claim 6
Independent Claim
180 words
A method of noninvasive measurement of predetermined blood constituents in living tissue comprising the steps of: a) illuminating the tissue with light of a first wavelength λ1 at an incident tissue site S1, such that the light is scattered and absorbed in the tissue; b) while the volume of blood in the tissue is changing, detecting the illuminated light, after it is scattered and absorbed at two separate tissue sites remote from the incident site and generating first and second electrical signals proportional thereto; c) separating a respective DC component of the first and second electrical signals from a respective AC component of the first and second electrical signals; d) dividing the AC component of the respective first and second electrical signals by the DC component of the first and second electrical signals to produce a respective normalized first and second electrical signals; e) forming a ratio by dividing the normalized first signal by the normalized second signal; and f) comparing said ratio with a predetermined value to determine the relative concentration of a predetermined blood constituent in the tissue.
Claim 7
Independent Claim
180 words
A method of noninvasive measurement of predetermined blood constituents in living tissue comprising the steps of: a) illuminating the tissue with light of a first wavelength λ1 at an incident tissue site S1, such that the light is scattered and absorbed in the tissue; b) while the volume of blood in the tissue is changing, detecting the illuminated light, after it is scattered and absorbed at two separate tissue sites remote from the incident site and generating first and second electrical signals proportional thereto; c) separating a respective DC component of the first and second electrical signals from a respective AC component of the first and second electrical signals; d) dividing the AC component of the respective first and second electrical signals by the DC component of the first and second electrical signals to produce a respective normalized first and second electrical signals; e) forming a ratio by dividing the normalized first signal by the normalized second signal; and f) comparing said ratio with a predetermined value to determine the relative concentration of a predetermined blood constituent in the tissue.
Claim 8
Dependent Claim
30 words
The method of claim 5 wherein the predetermined blood constituent is hemoglobin content and λ1 is a wavelength chosen to be relatively insensitive to tissue constituents other than hemoglobin content.
Claim 9
Dependent Claim
26 words
The method of claim 6 wherein an optical shield is disposed between the incident site and the detection sites to prevent non-scattered light from being detected.
Claim 10
Dependent Claim
11 words
The method of claim 6 wherein λ1 is about 815 nm.
Claim 11
Dependent Claim
19 words
The method of claim 5 wherein the blood volume in the tissue is changing due to a cardiac cycle.
Claim 12
Dependent Claim
117 words
Apparatus for noninvasive generation of a ratio signal for measurement of blood parameters in living tissue comprising: a) a light source for illuminating the tissue with light of a first wavelength λ1 at an incident tissue site, such that the light is scattered and absorbed by the tissue; b) light detectors for detecting the scattered light from λ1 at two separate detection tissue sites remote from said incident site and generating first and second electrical signals proportional to the intensity of the detected light; c) normalizing means for normalizing the first and second electrical signals to produce first and second normalized signals; and d) ratio means for forming a ratio of the first and second normalized signals.
Claim 13
Dependent Claim
117 words
Apparatus for noninvasive generation of a ratio signal for measurement of blood parameters in living tissue comprising: a) a light source for illuminating the tissue with light of a first wavelength λ1 at an incident tissue site, such that the light is scattered and absorbed by the tissue; b) light detectors for detecting the scattered light from λ1 at two separate detection tissue sites remote from said incident site and generating first and second electrical signals proportional to the intensity of the detected light; c) normalizing means for normalizing the first and second electrical signals to produce first and second normalized signals; and d) ratio means for forming a ratio of the first and second normalized signals.
Claim 14
Dependent Claim
11 words
The apparatus of claim 10 wherein λ1 is about 815 nm.
Claim 15
Dependent Claim
26 words
The apparatus of claim 10 including a signal processor in which the ratio derived in part (d) is processed to produce a measure of blood hemoglobin.
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| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1997-01-10 | 1997-07-12 | 1998-01-11 | $2000.00 | Window Closed / Lapsed |
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