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Measuring process for blood gas analysis sensors

  • US 6,226,540 B1
  • Filed: 06/04/1999
  • Issued: 05/01/2001
  • Est. Priority Date: 12/13/1995
  • Status: Expired due to Term
First Claim
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1. A method of determining the level of oxygenation of arterial blood SaO2 in tissue in vivo considering optical tissue properties by pulse oximetry, comprising the steps of:

  • a) emitting light through said tissue at a plurality of wavelengths at different instants of time, and different blood flow;

    b) measuring said light received passing through said tissue at said plurality of wavelengths at said instants of time;

    c) calculating a plurality of ratios of differential attenuation vs. time, Ω

    i corresponding to Ω

    i
    =ln





    (imin/imax)a
    ln





    (imin/imax)b
    for each wavelength pair i=a,b of different frequencies, wherein at least one wavelength pairing is selected based on optical tissue parameters, sufficient wavelength pairings and calibration curves of SaO2 v. Ω

    i have been empirically made such that the calibration curves are chosen for Ω

    i depending on optical tissue parameters to minimize error in producing an output signal indicative of level of arterial oxygenation;

    d) calculating at least one attenuation ratio LAj through said tissue for at least one wavelength, where LAj corresponds to;

    LAj=ln (light intensity received/light intensity emitted);

    using calibration data of SaO2 v. Ω

    i for at least one said LAj; and

    f) computing the level of oxygenation by comparing measured data with the calibration data.

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