SYSTEMS AND METHODS FOR VARIABLE FILTER ADJUSTMENT BY HEART RATE METRIC FEEDBACK AND NOISE REFERENCE SENSOR

• US 20170290549A1
• Filed: 04/03/2017
• Published: 10/12/2017
• Est. Priority Date: 04/12/2016
• Status: Abandoned Application

• Current Assignee: Valencell, Inc.
• Original Assignee: Valencell, Inc.
• Inventors: ROMESBURG, Eric Douglas
• Application Number:
  US15/477,706
• Publication Number:
  US 20170290549A1
• Time in Patent Office: Days
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/0095 by applying light and detecting acoustic waves, i.e. photoacoustic measurements
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/369 Electroencephalography [EEG] devices for psychotechnics A61B5/16
• CPC Class Codes: A61B 5/721 using a separate sensor to detect motion or using motion information derived from signals other than the physiological signal to be measured
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: A61B 7/00 Instruments for auscultation

Abstract

A physiological signal processing system/method for a physiological waveform that includes a cardiovascular signal component provides a first variable high pass filter that is responsive to the physiological waveform, and to a first corner frequency that is applied. A second variable high pass filter is responsive to a noise reference waveform from a noise reference sensor and is configured to high pass filter the noise reference waveform in response to a second corner frequency that is applied. A heart rate metric extractor is responsive to the variable high pass filters and is configured to extract a heart rate metric from the physiological waveform that is high pass filtered. A corner frequency adjuster is responsive to the heart rate metric extractor and is configured to determine the corner frequencies that are applied to the variable high pass filters, based on the heart rate metric that was extracted.

Claims

1. A physiological signal processing system comprising:

a physiological sensor that is configured to generate a physiological waveform that includes a cardiovascular signal component and a noise component therein;

a noise reference sensor that is configured to generate a noise reference waveform including the noise component therein;

a first variable high pass filter that is responsive to the physiological waveform and that is configured to high pass filter the physiological waveform in response to a first corner frequency that is applied thereto;

a second variable high pass filter that is responsive to the noise reference waveform and that is configured to high pass filter the noise reference waveform in response to a second corner frequency that is applied thereto;

a heart rate metric extractor that is responsive to the first and second variable high pass filters and that is configured to extract a heart rate metric from the physiological waveform that is high pass filtered by the first variable high pass filter and from the noise reference waveform that is high pass filtered by the second variable high pass filter; and

a corner frequency adjustor that is responsive to the heart rate metric extractor and that is configured to determine the first and second corner frequencies that are applied to the first and second variable high pass filters, respectively, based on the heart rate metric that was extracted.

2. A physiological signal processing system according to claim 1 wherein the noise component comprises a motion component and the reference sensor comprises an inertial sensor.

3. A physiological signal processing system according to claim 2 wherein the inertial sensor comprises an accelerometer, a pressure sensor and/or a blocked channel sensor.

4. A physiological signal processing system according to claim 1 wherein the noise reference waveform is substantially devoid of the cardiovascular signal component.

5. A physiological signal processing system according to claim 1 wherein the heart rate metric extractor is configured to obtain a difference between the physiological waveform that is high pass filtered by the first variable high pass filter and the noise reference waveform that is high pass filtered by the second variable high pass filter.

6. A physiological signal processing system according to claim 5 wherein the heart rate metric extractor comprises a spectral subtractor that is configured to obtain a difference between a frequency domain representation of the physiological waveform that is high pass filtered by the first variable high pass filter and a frequency domain representation of the noise reference waveform that is high pass filtered by the second variable high pass filter.

7. A physiological signal processing system according to claim 1 wherein the first and second corner frequencies comprise a substantially same corner frequency.

8. A physiological signal processing system according to claim 1, wherein the physiological waveform also includes a pulmonary signal component therein, the physiological signal processing system further comprising:

a variable low pass filter that is responsive to the physiological waveform and that is configured to low pass filter the physiological waveform in response to a third corner frequency that is applied thereto; and

a respiration rate metric extractor that is responsive to the variable low pass filter and that is configured to extract a respiration rate metric from the physiological waveform that is filtered by the variable low pass filter;

wherein the corner frequency adjustor is further configured to determine the third corner frequency that is applied to the variable low pass filter based on the heart rate metric that was extracted.

9. A physiological signal processing system according to claim 1 wherein the physiological waveform comprises an electrical physiological waveform including an electroencephalogram (EEG), an electrocardiogram (ECG) and/or a radio frequency (RF) waveform, an electro-optical physiological waveform including a photoplethysmograph (PPG) waveform, an electro-photoacoustic waveform including a photoacoustic waveform, an electro-mechanical physiological waveform including an auscultation waveform, a piezo sensor waveform and/or an accelerometer waveform, and/or an electro-nuclear physiological waveform.

10. A physiological signal processing system according to claim 1 wherein the first and second variable high pass filters each comprises a single high pass filter having an adjustable corner frequency.

11. A physiological signal processing system according to claim 1 wherein the first and second variable high pass filters each comprises a plurality of high pass filters, a respective one of which includes a different value of the corner frequency, and wherein the corner frequency adjustor is configured to select one of the plurality of high pass filters that corresponds to the corner frequency that is determined.

12. A physiological signal processing system according to claim 1 wherein the first and second variable high pass filters each comprises a variable digital high pass filter having a plurality of delay taps and wherein the corner frequency corresponds to a number of the plurality of delay taps that are selected to filter the physiological waveform.

13. A physiological signal processing system according to claim 12 wherein the corner frequency adjustor comprises a mapping system that is configured to map the heart rate metric that is extracted into the number of the delay taps that are selected to high pass filter the physiological waveform.

14. A physiological signal processing system according to claim 1 wherein the corner frequency adjuster is configured to reduce locking on an erroneous heart rate metric.

15. A physiological signal processing system according to claim 1 wherein the corner frequency adjuster is configured to initially set predetermined first and second corner frequencies corresponding to a predetermined heart rate prior to determining the first and second corner frequencies that are applied to the first and second variable high pass filters, respectively.

16. A physiological signal processing system according to claim 15 wherein the predetermined heart rate is a resting heart rate.

17. A physiological signal processing system according to claim 15 wherein the corner frequency adjuster is configured to initially set the predetermined first and second corner frequencies corresponding to the predetermined heart rate until the heart rate metric extractor locks on a heart rate in the physiological waveform.

18. A physiological signal processing system according to claim 15 wherein the corner frequency adjuster is configured to reset the predetermined first and second corner frequencies corresponding to the predetermined heart rate in response to determining that the physiological sensor is no longer responsive to a source of the physiological waveform.

19. A physiological signal processing system according to claim 1 wherein the corner frequency adjuster is configured to set predetermined first and second corner frequencies corresponding to a predetermined heart rate in response to determining that the physiological sensor is not responsive to a source of the physiological waveform.

20. A physiological signal processing system according to claim 1 wherein the corner frequency adjuster is configured to determine the first and second corner frequencies that are applied to the first and second variable high pass filters, respectively, by applying a margin to the heart rate metric.

21. A physiological signal processing system according to claim 1 further comprising:

a physiological metric assessor that is responsive to the heart rate metric extractor and that is configured to process the heart rate metric to generate at least one physiological assessment.

22. A physiological signal processing system comprising:

a photoplethysmograph (PPG) sensor that is configured to generate a PPG waveform that includes a cardiovascular signal component and an acceleration signal component therein;

an accelerometer that is configured to generate an accelerometer waveform including the acceleration component therein;

a first variable high pass filter that is responsive to the PPG waveform and that is configured to high pass filter the PPG waveform in response to a first corner frequency that is applied thereto;

a second variable high pass filter that is responsive to the accelerometer waveform and that is configured to high pass filter the accelerometer waveform in response to a second corner frequency that is applied thereto;

a heart rate metric extractor that is responsive to the first and second variable high pass filters and that is configured to extract a heart rate metric from the PPG waveform that is high pass filtered by the first variable high pass filter and from the accelerometer waveform that is high pass filtered by the second variable high pass filter; and

a corner frequency adjustor that is responsive to the heart rate metric extractor and that is configured to determine the first and second corner frequencies that are applied to the first and second variable high pass filters, respectively, based on the heart rate metric that was extracted.

23. A physiological signal processing method for a physiological waveform that includes a cardiovascular signal component and a noise component therein, and a noise reference waveform including the noise component therein, the physiological signal processing method comprising:

high pass filtering the physiological waveform in response to a first adjustable high pass filter corner frequency;

high pass filtering the noise reference waveform in response to a second adjustable high pass filter corner frequency;

extracting a heart rate metric from the physiological waveform that is high pass filtered and from the noise reference waveform that is high pass filtered; and

determining the first and second adjustable high pass filter corner frequencies from the heart rate metric that was extracted.