Modified Pulse Oximetry Technique For Measurement Of Oxygen Saturation In Arterial And Venous Blood
First Claim
1. A method for the measurement of oxygen saturation in arterial blood, the method comprising:
- (a) applying to the skin an apparatus including;
(i) light-sources for generating light of three peak wavelengths λ
1, λ
2 and λ
3;
(ii) a detector arrangement; and
(iii) an electronics unit, the apparatus configured to detect, for each light-source, the transmitted light through the tissue;
(b) for each light source, deriving a PPG curve;
(c) deriving from the three PPG curves a parameter related to the relative change in light transmission for each of the three wavelengths, and the ratio R12 and R13 of that parameter for the two wavelengths λ
1 and λ
2 and for the two wavelengths λ
1, and λ
3, respectively; and
(d) determining the oxygen saturation in arterial blood, SaO2, from the solution of three equations including;
a. relationship between SaO2 and R12, which includes the optical path-lengths l1 and l2;
b. relationship between SaO2 and R13, which includes the optical path-lengths l1 and l3;
c. relationship between small changes in the path-length l and small changes in the wavelength λ
,where the first two equations include the values of the extinction coefficient for the three peak wavelength for oxygenated blood ε
o and for deoxygenated blood ε
d.
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Abstract
A method for the measurement of oxygen saturation in arterial blood SaO2 by means of pulse oximetry without calibration is described. Photoplethysmography (PPG) is measured in three wavelengths in the infrared and for each PPG curve the relative change in light transmission is obtained. Two equations, each relating SaO2 to the ratio of the relative changes in light transmission for two wavelengths, using the values of the extinction coefficients of oxygenated and deoxygenated hemoglobin for the three wavelengths, enable the determination of SaO2, assuming linear dependence of the optical path-length on the wavelength, for the three wavelengths in the infrared. Similar technique for the determination of oxygen saturation in venous blood from changes in light transmission due to changes in venous blood volume is suggested
46 Citations
25 Claims
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1. A method for the measurement of oxygen saturation in arterial blood, the method comprising:
-
(a) applying to the skin an apparatus including; (i) light-sources for generating light of three peak wavelengths λ
1, λ
2 and λ
3;
(ii) a detector arrangement; and
(iii) an electronics unit, the apparatus configured to detect, for each light-source, the transmitted light through the tissue;(b) for each light source, deriving a PPG curve; (c) deriving from the three PPG curves a parameter related to the relative change in light transmission for each of the three wavelengths, and the ratio R12 and R13 of that parameter for the two wavelengths λ
1 and λ
2 and for the two wavelengths λ
1, and λ
3, respectively; and(d) determining the oxygen saturation in arterial blood, SaO2, from the solution of three equations including; a. relationship between SaO2 and R12, which includes the optical path-lengths l1 and l2; b. relationship between SaO2 and R13, which includes the optical path-lengths l1 and l3; c. relationship between small changes in the path-length l and small changes in the wavelength λ
,where the first two equations include the values of the extinction coefficient for the three peak wavelength for oxygenated blood ε
o and for deoxygenated blood ε
d. - View Dependent Claims (5, 9)
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2. A method for the measurement of oxygen saturation in arterial blood, the method comprising:
-
(a) applying to the skin an apparatus including; (i) light-sources for generating light of three peak wavelengths λ
1, λ
2 and λ
3;
(ii) a detector arrangement; and
(iii) an electronics unit, the apparatus configured to detect, for each light-source, the transmitted light through the tissue;(b) for each light-source, determining the mean extinction coefficients over the spectrum band of the light-source emitted light for oxygenated blood ε
o and for deoxygenated blood ε
d;(c) for each light source, deriving a PPG curve; (d) deriving from the three PPG curves a parameter related to the relative change in light transmission for each of the three wavelengths, and the ratio R12 and R13 of that parameter for the two wavelengths λ
1 and λ
2 and for the two wavelengths λ
1 and λ
3, respectively; and(e) determining the oxygen saturation in arterial blood, SaO2, from the solution of three equations including; a. relationship between SaO2 and R12, which includes the optical path-lengths l1 and l2; b. relationship between SaO2 and R13, which includes the optical path-lengths l1 and l3; c. relationship between small changes in the path-length l and small changes in the wavelength λ
,where the first two equations include the values of said mean extinction coefficient for the three light sources for oxygenated blood ε
o and for deoxygenated blood ε
d. - View Dependent Claims (3, 4, 6, 7, 8, 10)
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11. A method for the measurement of oxygen saturation in tissue venous blood, the method comprising:
-
(a) applying to the skin an apparatus including; (i) light-sources for generating light of three peak wavelengths λ
1, λ
2 and λ
3;
(ii) a detector arrangement; and
(iii) an electronics unit, the apparatus configured to detect, for each light-source, the transmitted light through the tissue;(b) for each light source, deriving a curve of light transmission through the tissue while venous blood volume changes; (c) deriving from the three light transmission curves a parameter related to the relative change in light transmission for each of the three wavelengths, and the ratio R12 and R13 of that parameter for the two wavelengths λ
1 and λ
2 and for the two wavelengths λ
1 and λ
3, respectively, and(d) determining the oxygen saturation in venous blood, SvO2, from the solution of three equations including; a. relationship between SaO2 and R12, which includes the optical path-lengths l1 and l2; b. relationship between SaO2 and R13, which includes the optical path-lengths l1 and l3; c. relationship between small changes in the path-length l and small changes in the wavelength λ
,where the first two equations include the values of the extinction coefficient for the three peak wavelength for oxygenated blood ε
o and for deoxygenated blood ε
d. - View Dependent Claims (15, 19)
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12. A method for the measurement of oxygen saturation in tissue venous blood, the method comprising:
-
(a) applying to the skin an apparatus including; (i) light-sources for generating light of three peak wavelengths λ
1, λ
2 and λ
3;
(ii) a detector arrangement; and
(iii) an electronics unit, the apparatus configured to detect, for each light-source, the transmitted light through the tissue;(b) for each light-source, determining the mean extinction coefficients over the spectrum band of the light-source emitted light for oxygenated blood ε
o and for deoxygenated blood ε
d;(c) for each light source, deriving a curve of light transmission through the tissue while venous blood volume changes; (d) deriving from the three light transmission curves a parameter related to the relative change in light transmission for each of the three wavelengths, and the ratio R12 and R13 of that parameter for the two wavelengths λ
1 and λ
2 and for the two wavelengths λ
1 and λ
3, respectively; and(e) determining the oxygen saturation in venous blood, SvO2, from the solution of three equations including; a. relationship between SaO2 and R12, which includes the optical path-lengths l1 and l2; b. relationship between SaO2 and R13, which includes the optical path-lengths l1 and l3; c. relationship between small changes in the path-length l and small changes in the wavelength λ
,where the first two equations include the values of said mean extinction coefficient for the three light sources for oxygenated blood ε
o and for deoxygenated blood ε
d. - View Dependent Claims (13, 14, 16, 17, 18, 20, 21, 22, 23, 24, 25)
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Specification