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Separating motion from cardiac signals using second order derivative of the photo-plethysmogram and fast fourier transforms

  • US 8,073,516 B2
  • Filed: 01/30/2006
  • Issued: 12/06/2011
  • Est. Priority Date: 01/31/2002
  • Status: Active Grant
First Claim
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1. A pulse oximetry system for the determination of a physiological parameter wherein said pulse oximetry system is configured to remove motion artifacts from physiological signals, comprising:

  • an optical sensor for providing said pulse oximetry system with photo-plethysmographic data, wherein said sensor comprises a light emitting diode for emitting light and a photo-detector for detecting said light, wherein said detected light contains information on the photo-plethysmographic data;

    a processor for processing the photo-plethysmographic data; and

    a memory unit, wherein said memory unit is operably coupled to said processor, and wherein said processor is configured to;

    (a) acquire said photo-plethysmographic data;

    (b) transform the photo-plethysmographic data into frequency domain data;

    (c) analyze the frequency domain data;

    (d) reconstruct a time domain data photo-plethysmographic signal from said frequency domain data;

    (e) analyze a second order derivative of the time domain photo-plethysmographic signal to identify parameters;

    (f) use said parameters to separate a physiological signal from a motion artifact in the time domain photo-plethysmographic signal; and

    (g) compute a physiological parameter from said motion artifact independent physiological signal.

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