Physiological metric estimation rise and fall limiting
First Claim
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1. A physiological processor configured to process a time domain photoplethysmography waveform provided by a photoplethysmography sensor, the processor comprising:
- a spectral transformer configured to;
convert the photoplethysmography waveform from the time domain to a frequency domain to generate a spectrum; and
determine, responsive to the spectrum, an instantaneous estimate of a heart rate; and
a filter configured to;
compare the instantaneous estimate to a current filtered estimate of the heart rate; and
output, to an output interface, a revised filtered estimate of the heart rate computed based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate.
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Abstract
Methods and apparatus disclosed herein use a filtering technique to improve the accuracy of the results achieved when processing data provided by a physiological sensor. The disclosed filtering technique corrects many of the accuracy problems associated with physiological sensors, particularly PPG sensors. Broadly, the filtering technique adjusts a current filtered estimate of a physiological metric as a function of a rate limit based on a comparison between an instantaneous estimate of the physiological metric and the current filtered estimate.
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Citations
34 Claims
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1. A physiological processor configured to process a time domain photoplethysmography waveform provided by a photoplethysmography sensor, the processor comprising:
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a spectral transformer configured to; convert the photoplethysmography waveform from the time domain to a frequency domain to generate a spectrum; and determine, responsive to the spectrum, an instantaneous estimate of a heart rate; and a filter configured to; compare the instantaneous estimate to a current filtered estimate of the heart rate; and output, to an output interface, a revised filtered estimate of the heart rate computed based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate. - View Dependent Claims (2)
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3. A method of processing data provided by a physiological sensor, the method comprising:
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receiving a time domain physiological waveform from the physiological sensor; converting the received physiological waveform from the time domain to a frequency domain to generate a physiological spectrum; determining, using the physiological spectrum, an instantaneous estimate of a physiological metric; comparing the instantaneous estimate to a current filtered estimate of the physiological metric; computing a revised filtered estimate of the physiological metric based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate; and outputting the revised filtered estimate to an output interface; wherein the rate limit comprises one of a first rate limit for an increasing physiological metric and a second rate limit for a decreasing physiological metric, where a magnitude of the second rate limit relative to the current filtered estimate is different from a magnitude of the first rate limit relative to the current filtered estimate; and wherein the revised filtered estimate comprises; the sum of the current filtered estimate and the extremum value wherein the extremum value comprises the minimum of the first rate limit and the difference between the instantaneous estimate and the current filtered estimate when the instantaneous estimate is greater than the current filtered estimate; and the sum of the current filtered estimate and the extremum value wherein the extremum value comprises the maximum of the second rate limit and the difference between the instantaneous estimate and the current filtered estimate when the instantaneous estimate is less than the current filtered estimate. - View Dependent Claims (4, 5, 6)
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7. A physiological processor configured to process a time domain physiological waveform provided by a physiological sensor, the processor comprising:
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a spectral transformer configured to; convert the physiological waveform from the time domain to a frequency domain to generate a physiological spectrum; and determine, using the physiological spectrum, an instantaneous estimate of a physiological metric; and a filter configured to; compare the instantaneous estimate to a current filtered estimate of the physiological metric; and output, to an output interface, a revised filtered estimate of the physiological metric based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate; wherein the rate limit comprises one of a first rate limit for an increasing physiological metric and a second rate limit for a decreasing physiological metric, where a magnitude of the second rate limit relative to the current filtered estimate is different from a magnitude of the first rate limit relative to the current filtered estimate; and wherein the revised filtered estimate comprises; the sum of the current filtered estimate and the extremum value wherein the extremum value comprises the minimum of the first rate limit and the difference between the instantaneous estimate and the current filtered estimate when the instantaneous estimate is greater than the current filtered estimate; and the sum of the current filtered estimate and the extremum value wherein the extremum value comprises the maximum of the second rate limit and the difference between the instantaneous estimate and the current filtered estimate when the instantaneous estimate is less than the current filtered estimate. - View Dependent Claims (8, 9, 10, 11)
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12. A method of processing data provided by a physiological sensor, the method comprising:
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receiving a time domain physiological waveform from the physiological sensor; converting the received physiological waveform from the time domain to a frequency domain to generate a physiological spectrum; determining, using the physiological spectrum, an instantaneous estimate of a physiological metric; comparing the instantaneous estimate to a current filtered estimate of the physiological metric; determining a rate limit relative to the current filtered estimate responsive to one or more properties of the physiological waveform; computing a revised filtered estimate of the physiological metric based on the current filtered estimate and the rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate; and outputting the revised filtered estimate to an output interface. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A method of processing data provided by a physiological sensor, the method comprising:
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receiving a time domain physiological waveform from the physiological sensor; converting the received physiological waveform from the time domain to a frequency domain to generate a physiological spectrum; determining, using the physiological spectrum, an instantaneous estimate of a physiological metric by processing the physiological spectrum responsive to a second waveform from a second sensor to reduce noise in the instantaneous estimate; comparing the instantaneous estimate to a current filtered estimate of the physiological metric; computing a revised filtered estimate of the physiological metric based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate; and outputting the revised filtered estimate to an output interface. - View Dependent Claims (23)
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24. A physiological processor configured to process a time domain physiological waveform provided by a physiological sensor, the processor comprising:
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a spectral transformer configured to; convert the physiological waveform from the time domain to a frequency domain to generate a physiological spectrum; and determine, using the physiological spectrum, an instantaneous estimate of a physiological metric; and a filter configured to; compare the instantaneous estimate to a current filtered estimate of the physiological metric; and output, to an output interface, a revised filtered estimate of the physiological metric based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate; wherein the filter comprises an adjustment processor configured to determine the rate limit relative to the current filtered estimate responsive to one or more properties of the physiological waveform. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32)
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33. A physiological processor configured to process a time domain physiological waveform provided by a physiological sensor, the processor comprising:
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a spectral transformer configured to; convert the physiological waveform from the time domain to a frequency domain to determine a physiological spectrum; and determine, based on the physiological spectrum, an instantaneous estimate of a physiological metric; a filter configured to; compare the instantaneous estimate to a current filtered estimate of the physiological metric; and output, to an output interface, a revised filtered estimate of the physiological metric based on the current filtered estimate and a rate limit and responsive to the comparison between the instantaneous estimate and the current filtered estimate, said revised filtered estimate comprising a sum of the current filtered estimate and an extremum value, said extremum value comprising the extremum of the rate limit and a difference between the instantaneous estimate and the current filtered estimate; and a second sensor configured to receive a time domain second waveform; wherein the spectral transformer is further configured to convert the second waveform from the time domain to the frequency domain to determine a second spectrum, and to determine the instantaneous estimate responsive to the second spectrum to reduce the noise in the instantaneous estimate. - View Dependent Claims (34)
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Specification