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Method and apparatus for measuring blood oxygen saturation

  • US 8,280,472 B2
  • Filed: 12/27/2007
  • Issued: 10/02/2012
  • Est. Priority Date: 07/19/2007
  • Status: Active Grant
First Claim
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1. A method for measuring blood oxygen saturation, the method comprising:

  • acquiring intensities of transmitted lights that are obtained by transmitting respectively a light of a first wavelength and a light of a second wavelength through organism tissues, and converting the intensities of the transmitted lights into corresponding signals for the light of the first wavelength and the light of the second wavelength;

    defining at least one interval on waveforms of the signals for the light of the first wavelength and the light of the second wavelength, and performing an area integral on the waveforms of the signals for the light of the first wavelength and the light of the second wavelength in the at least one interval to produce a total area integral of the signal for the light of the first wavelength and a total area integral of the signal for the light of the second wavelength;

    calculating a ratio of the total area integral of the signal for the light of the first wavelength to the total area integral of the signal for the light of the second wavelength as a blood oxygen content R; and

    calculating a blood oxygen saturation according to the following formula;


    SpO2=(

    R+B
    )/(

    R+D
    ),where SpO2 is the blood oxygen saturation;

    A=ε

    4;

    B=−

    ε

    2;

    C=ε

    4

    ε

    3;

    D=ε

    1

    ε

    2;

    ε

    1, ε

    2 are respectively an absorption rate of oxyhemoglobin to the light of the first wavelength and an absorption rate of deoxyhemoglobin to the light of the first wavelength; and

    ε

    3, ε

    4 are respectively an absorption rate of oxyhemoglobin to the light of the second wavelength and an absorption rate of deoxyhemoglobin to the light of the second wavelength;

    wherein the at least one interval is divided into different confidence intervals according to different degrees of noise interference in a pulse fluctuation cycle, wherein a confidence value of one confidence interval with relatively high interference is less than that of another confidence interval with relatively low interference, wherein the total area integral of the signal for the light of the first wavelength comprises a sum of products of the area integral of the waveform of the signal for the light of the first wavelength in all the confidence intervals and the corresponding confidence, and wherein the total area integral of the signal for the light of the second wavelength comprises a sum of products of the area integral of the waveform of the signal for the light of the second wavelength in all the confidence intervals and the corresponding confidence.

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