Separating motion from cardiac signals using second order derivative of the photo-plethysmogram and fast fourier transforms
First Claim
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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Abstract
The present invention is directed toward a pulse oximetry system for the determination of a physiological parameter capable of removing motion artifacts from physiological signals comprises a hardware subsystem and a software subsystem. The software subsystem is used in conjunction with the hardware subsystem to perform a method for removing a plurality of motion artifacts from the photo-plethysmographic data and for obtaining a measure of at least one physiological parameter from the data. The method comprises acquiring the raw photo-plethysmographic data, transforming the data into the frequency domain, analyzing the transformed data to locate a series of candidate cardiac spectral peaks (primary plus harmonics), reconstructing a photo-plethysmographic signal in the time domain with only the candidate cardiac spectral peaks (primary plus harmonics), computing the second order derivative of the reconstructed photo-plethysmographic signal, analyzing the candidate second order derivative photo-plethysmographic signal to determine the absence or presence of cardiac physiologic signal characteristics, and finally selecting the best physiologic candidate from the series of potential cardiac spectral peaks (primary plus harmonics) based upon a second derivative scoring system. This scoring system is preferentially based upon second derivative processing analysis, but can be equally applied using the first, third, fourth or other similar derivative processing analysis.
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Citations
14 Claims
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
- 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;
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14. 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) analyze frequency domain data derived from said photo-plethysmographic data, (b) transform the frequency domain data into a time domain photo-plethysmographic signal;
(c) analyze a second order derivative of the time domain photo-plethysmographic signal to identify parameters; and
(d) use the identified parameters to separate a physiological signal from a motion artifact in the time domain photo-plethysmographic signal.
- 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;
Specification