Implantable multi-wavelength venous oxygen saturation and hematocrit sensor and method
First Claim
1. A method for determining a value of oxygen saturation of blood, comprising:
- (a) determining a value R1 indicative of a relative reflectance of the blood for light of a first wavelength compared to light of a second wavelength, and determining a value R2 indicative of a relative reflectance of the blood for light of the second wavelength compared to light of a third wavelength;
(b) determining a value m indicative of a level of hematocrit of the blood; and
(c) determining a value of oxygen saturation of the blood utilizing a first polynomial function of the values R1 and R2 divided by a second polynomial function of the values R1 and R2, wherein one of the first and second polynomial functions of the values R1 and R2 includes the value m as a factor;
wherein at least one of steps (a), (b) and (c) is performed using at least one processor.
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Accused Products
Abstract
An intravenous implantable optical sensor assesses the relative absorbance of multiple wavelengths of light in order to determine oxygen saturation. The calculation of oxygen saturation is enhanced by use of a function of hematocrit which is derived from the relative absorbance of light of an isobestic wavelength along two different length paths through the blood. The use of the hematocrit-dependent term and multiple wavelengths of light to calculate oxygen saturation provides results that are less susceptible to noise and variation in hematocrit and thus provides a more accurate measure of oxygen saturation over a wider range of conditions than previously possible. The optical sensor may form part of an implantable system which performs the calculation of oxygen saturation and uses the results for a diagnostic or therapeutic purpose.
64 Citations
24 Claims
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1. A method for determining a value of oxygen saturation of blood, comprising:
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(a) determining a value R1 indicative of a relative reflectance of the blood for light of a first wavelength compared to light of a second wavelength, and determining a value R2 indicative of a relative reflectance of the blood for light of the second wavelength compared to light of a third wavelength; (b) determining a value m indicative of a level of hematocrit of the blood; and (c) determining a value of oxygen saturation of the blood utilizing a first polynomial function of the values R1 and R2 divided by a second polynomial function of the values R1 and R2, wherein one of the first and second polynomial functions of the values R1 and R2 includes the value m as a factor; wherein at least one of steps (a), (b) and (c) is performed using at least one processor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for determining a value of oxygen saturation of blood, comprising:
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(a) emitting light of first, second and third wavelengths toward the blood; (b) generating light intensity values indicative of the intensity of light of each of the first, second and third wavelengths reflected back from the blood over a first distance; (c) using the light intensity values to determine a value R1 indicative of a relative reflectance of the blood for light of the third wavelength compared to light of the second wavelength; (d) using the light intensity values to determine a value R2 indicative of a relative reflectance of the blood for light of the second wavelength compared to light of the first wavelength; (e) determining a value m indicative of a level of hematocrit of the blood; and
(f) determining a value of oxygen saturation of the blood utilizing a polynomial function of the values R1, R2 and m. - View Dependent Claims (12)
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13. An implantable system for measuring oxygen saturation of blood comprising:
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a plurality of light sources that emit light into the blood at first, second, and third wavelengths; one or more light sensors that permit the measurement of the relative reflectance of the blood for light of each of the first, second, and third wavelengths; a hematocrit calculation unit that calculates a ratio Rh of relative reflectance of the blood for light of the third wavelength over a first distance relative to a second longer distance, wherein the ratio Rh is indicative of a level of hematocrit of the blood; and an oxygen saturation calculation unit that calculates a value R1 indicative of relative reflectance of the blood for light of the third wavelength relative to light of the second wavelength, and calculates a value R2 indicative of relative reflectance of the blood for light of the second wavelength relative to light of the first wavelength, and determines the oxygen saturation of the blood based on a first polynomial function of the values R1 and R2 divided by a second polynomial function of the values R1 and R2, wherein one of the first and second polynomial functions of the values R1 and R2 includes a third polynomial function of the ratio Rh as a factor. - View Dependent Claims (14, 15, 16, 17, 18)
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19. A method for determining oxygen saturation of blood having hematocrit, comprising:
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(a) measuring a first property of the blood that varies with the oxygen saturation of the blood and the hematocrit of the blood and generating a value R1 indicative of the first property; (b) measuring a second property of the blood that varies with the oxygen saturation of the blood and the hematocrit of the blood and generating a value R2 indicative of the second property; (c) measuring a third property of the blood that varies with the hematocrit of the blood but that does not vary significantly with the oxygen saturation and generating a ratio Rh indicative of the third property; and (d) determining the oxygen saturation of the blood utilizing a first polynomial function of the values R1 and R2 divided by a second polynomial function of the values R1 and R2, wherein one of the first and second polynomial functions of the values R1 and R2 includes a third polynomial function of the ratio Rh as a factor; wherein at least step (d) is performed using at least one processor. - View Dependent Claims (20, 21, 22, 23, 24)
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Specification