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METHOD AND APPARATUS FOR DETERMINING SpO2 OF A SUBJECT FROM AN OPTICAL MEASUREMENT

  • US 20160066863A1
  • Filed: 04/05/2013
  • Published: 03/10/2016
  • Est. Priority Date: 04/05/2013
  • Status: Abandoned Application
First Claim
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1. A method of determining SpO2 of a subject from an optical measurement, the method comprising:

  • (i) obtaining a first signal from a first light illumination;

    (ii) obtaining a second signal from a second light illumination, the second light illumination having a wavelength which is different from that of the first light illumination;

    (iii) pairing the first and second signals in which an amplitude of each cardiac rhythm cycle of the first signal is aligned to an amplitude of a respective cardiac rhythm cycle of the second signal to form a plurality of paired windows;

    (iv) for each paired window, calculating values of a ratio R from the paired first and second signals;

    (v) based on the calculated R values, binning the calculated R values into predetermined frequency bins; and

    (vi) selecting at least one of the frequency bins to derive a revised ratio, Rrev; and

    (vii) determining SpO2 from the revised ratio Rrev;

    whereinthe method further comprises(viii) obtaining ACamb and DCamb;

    (viiii) calculating a ratio, Ramb-signal, based on ACamb and ACsignal;

    (x) providing a zoning schema divided into a plurality of reference zones with each reference zone defined by respective values of first, second and third reference variables which are associated respectively with Rrev, Ramb-signal and DCamb;

    each reference zone being associated with a corresponding method of computing SpO2;

    (xi) comparing Rrev, Ramb-signal and DCamb with respective reference variables of the zoning schema to determine which one of the plurality of reference zones is a selected zone; and

    (xii) applying the method of computing SpO2 corresponding to the selected zone for determining SpO2;

    whereACamb is an AC component value of an ambient signal with the first and second light illuminations switched off;

    DCamb is a DC component value of the ambient signal; and

    ACsignal is an AC component value of the first or second signal.

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