Method for evaluating relative oxygen saturation in body tissues
First Claim
1. A method for determining hemoglobin oxygen saturation in a tissue in vivo;
- said method comprising the steps of;
(a) measuring the visible reflectance spectrum or the visible absorbance spectrum of the tissue in vivo over at least a portion of the range of wavelengths between 530 nm and 584 nm;
(b) determining one or more of the values x, y, and z, wherein;
(i) x is proportional to the integral of {the reference stratum minus the measured visible spectrum} over at least a portion of region I;
(ii) y is proportional to the integral of {the measured visible spectrum minus the reference stratum} over at least a portion of region II;
(iii) z is proportional to the integral of {the reference stratum minus the measured visible spectrum} over at least a portion of region III;
(iv) region I is the region of the visible spectrum between the hemoglobin isosbestic point at about 530 nm and the hemoglobin isosbestic point at about 545 nm;
(v) region II is the region of the visible spectrum between the hemoglobin isosbestic point at about 545 nm and the hemoglobin isosbestic point at about 570 nm;
(vi) region III is the region of the visible spectrum between the hemoglobin isosbestic point at about 570 nm and the hemoglobin isosbestic point at about 584 nm;
(vii) the reference stratum comprises a sequence of three linear segments;
a first linear segment connecting the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 530 nm to the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 545 nm;
a second linear segment connecting the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 545 nm to the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 570 nm; and
a third linear segment connecting the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 570 nm to the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 584 nm;
whereby;
(viii) larger values of x, y, or z correspond to higher hemoglobin oxygen saturation in the tissue in vivo, and lower values of x, y, or z correspond to lower hemoglobin oxygen saturation in the tissue in vivo.
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Abstract
A new method was discovered to analyze continuous spectral curves to determine relative hemoglobin oxygen saturation, using spectral curves collected from a continuous range of wavelengths from about 530 nm to about 584 nm, including spectra from transmitted or reflected light. Using isosbestic points and curve areas, a relative saturation index was calculated. With this method, noninvasive, in vivo measurement of relative oxygen saturation was made using light reflected from blood vessels in the eye and to map and measure relative changes in hemoglobin oxygen saturation in primate retinal vessels and optic nerve head in response to controlled changes in inspired oxygen and intraocular pressure (IOP). This method could also measure oxygen saturation from other blood vessels that reflect light sufficient to give a clear spectra from the blood hemoglobin. Changes in blood oxygen saturation can be monitored with this method for early detection of disease.
28 Citations
13 Claims
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1. A method for determining hemoglobin oxygen saturation in a tissue in vivo;
- said method comprising the steps of;
(a) measuring the visible reflectance spectrum or the visible absorbance spectrum of the tissue in vivo over at least a portion of the range of wavelengths between 530 nm and 584 nm; (b) determining one or more of the values x, y, and z, wherein; (i) x is proportional to the integral of {the reference stratum minus the measured visible spectrum} over at least a portion of region I; (ii) y is proportional to the integral of {the measured visible spectrum minus the reference stratum} over at least a portion of region II; (iii) z is proportional to the integral of {the reference stratum minus the measured visible spectrum} over at least a portion of region III; (iv) region I is the region of the visible spectrum between the hemoglobin isosbestic point at about 530 nm and the hemoglobin isosbestic point at about 545 nm; (v) region II is the region of the visible spectrum between the hemoglobin isosbestic point at about 545 nm and the hemoglobin isosbestic point at about 570 nm; (vi) region III is the region of the visible spectrum between the hemoglobin isosbestic point at about 570 nm and the hemoglobin isosbestic point at about 584 nm; (vii) the reference stratum comprises a sequence of three linear segments;
a first linear segment connecting the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 530 nm to the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 545 nm;
a second linear segment connecting the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 545 nm to the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 570 nm; and
a third linear segment connecting the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 570 nm to the visible reflectance or absorbance of hemoglobin at the isosbestic point at about 584 nm;whereby; (viii) larger values of x, y, or z correspond to higher hemoglobin oxygen saturation in the tissue in vivo, and lower values of x, y, or z correspond to lower hemoglobin oxygen saturation in the tissue in vivo. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- said method comprising the steps of;
Specification