Adaptive calibration pulsed oximetry method and device
First Claim
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1. A method for calibrating an oximeter for use in determining an arterial blood oxygen saturation level in tissue, comprising:
- determining a steady-state component of a light transmission through or reflection from a tissue at each of a first and second wavelengths;
using the steady-state component of the light transmission or reflection to select a calibration curve, said calibration curve representing a level of arterial blood oxygen saturation in relation to a pulsatile factor;
determining the pulsatile factor; and
determining the arterial blood oxygen saturation level using the selected calibration curve and the pulsatile factor.
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Abstract
A method for determining an arterial blood oxygen saturation level according to this invention includes measuring the light transmittance through tissue of light of a first wavelength and a second wavelength. A steady-state component of the measured light transmission is used to select an appropriate calibration curve. A pulsatile component of the measured light transmission is used to determine the arterial blood oxygen saturation level using the selected calibration curve. An oximetry system is also provided.
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Citations
21 Claims
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1. A method for calibrating an oximeter for use in determining an arterial blood oxygen saturation level in tissue, comprising:
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determining a steady-state component of a light transmission through or reflection from a tissue at each of a first and second wavelengths;
using the steady-state component of the light transmission or reflection to select a calibration curve, said calibration curve representing a level of arterial blood oxygen saturation in relation to a pulsatile factor;
determining the pulsatile factor; and
determining the arterial blood oxygen saturation level using the selected calibration curve and the pulsatile factor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 20)
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10. An oximetry system for measuring arterial blood oxygen saturation levels in a tissue, comprising:
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a light source configured to transmit light of a first wavelength and a second wavelength to a medium;
a light transducer configured to measure an amount of the light of each of the first and second wavelengths transmitted through or reflected from the medium and to generate light measurement data corresponding to the measured amount of light; and
a data processor configured to use one or more steady-state components of the light measurement data to adaptively select a calibration curve, said calibration curve being representative of an amount of arterial blood oxygen saturation relative to a pulsatile factor. - View Dependent Claims (11, 12, 13, 14)
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15. A method of measuring an arterial blood oxygen saturation level in a tissue, comprising:
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comparing steady-state light measurements in a standard medium of light of a first and second wavelengths with steady-state light measurements in the tissue of the light of the first and second wavelengths;
measuring an amount of the light of the first and second wavelengths transmitted through or reflected from the tissue to obtain a light measurement for each wavelength;
using steady-state components of the light measurements to select a calibration curve; and
using the selected calibration curve to determine an arterial blood oxygen saturation level in the tissue. - View Dependent Claims (16, 17, 18, 19)
using the steady-state component of the light measurements to determine a blood volume fraction and a mixed blood oxygen saturation value;
using the mixed blood oxygen saturation value and the blood volume fraction to select the calibration curve from a plurality of sets of calibration curves.
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19. A method according to claim 15, further comprising:
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calculating a pulsatile factor using pulsatile signals normalized by the steady-state component of the light measurements at the first and second wavelengths; and
using the pulsatile factor and the selected calibration curve to determine the arterial blood oxygen saturation level.
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21. A method of generating a function grid relating optical properties of a tissue to a blood volume fraction and a mixed blood oxygen saturation level, comprising:
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generating a light transport function for light of a first wavelength as a function of absorption and scattering coefficients and a geometry of a probe;
generating a light transport function for light of a second wavelength as a function of absorption and scattering coefficients and the geometry of the probe; and
using the light transport functions for light of the first and second wavelengths in conjunction with spectral optical absorption properties of blood and tissue components to generate a function grid relating measured light transmission or reflectance of a tissue to a blood volume fraction and a mixed blood oxygen saturation level.
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Specification