HEART RATE PATH OPTIMIZER

• US 20180110469A1
• Filed: 12/20/2017
• Published: 04/26/2018
• Est. Priority Date: 08/22/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: MAANI, Ehsan, Culbert, Daniel J., Shapiro, Ian R.
• Granted Patent: US 11,986,322 B2
• Time in Patent Office: Days
• CPC Class Codes: A61B 2560/0493 controlled by voice
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• 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 5/024 Detecting, measuring or recording pulse rate or heart rate A61B5/0205, A61B5/021 take precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/11 Measuring movement of the entire body or parts thereof, e.g. head or hand tremor, mobility of a limb for measuring pulse A61B5/02 ;A61B5/1038 takes precedence; motion detection to correct for motion artifacts in physiological signals A61B5/721
• 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 5/7257 using Fourier transforms
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence

Abstract

A device for determining a heart rate of a user has a PPG sensor and an accelerometer to compensate for acceleration artifacts within the PPG signal. The device transforms time domain PPG and accelerometer signals into the frequency domain using a Fourier transformation and utilizes the Fourier coefficient magnitudes as indicative of the probability of candidate heart rate values. Candidate heart rate values are determined at sampling times over a time interval and a most probable heart rate path during the time interval is determined using a reward/penalty algorithm.

Claims

1. A device for determining a heart rate (HR) of a user comprising:

a (HR) sensor configured to be worn by a user and for providing HR signals corresponding to HR values;

processing circuitry capable of;

selecting a first path of HR values over a first sequence of HR measurements in accordance with a given criteria, wherein the first path includes a selection of a respective candidate HR value for each HR measurement of the first sequence of HR measurements; and

selecting a second path of HR values over a second sequence of HR measurements in accordance with the given criteria, the second sequence of HR measurements including the first sequence of HR measurements and at least one additional HR measurement subsequent to the first sequence of HR measurements,

wherein the second path includes at least one different selection of a respective candidate HR value for at least one of the HR measurements of the first sequence of HR measurements.

2. The device of claim 1, wherein the given criteria is based on consecutive Fourier coefficient magnitudes of corresponding consecutive HR values along each of the first and second paths and differences in consecutive HR values along each of the first and second paths.

3. The device of claim 2, wherein the processing circuitry provides the HR values by transforming the HR signals into frequency domain HR signals (FDHR signals) and adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost.

4. The device of claim 3, wherein the Fourier component magnitudes are absolute values of Fourier coefficients of the FDHR signals.

5. The device of claim 1, wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and low pass filtering Fourier component magnitudes of the FDHR signals.

6. The device of claim 5, wherein the low pass filtering is provided by utilizing a Gaussian convolution.

7. The device of claim 1, wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and providing a peak boost to Fourier component magnitudes of the FDHR signals.

8. The device of claim 7, wherein the peak boost multiplies each local maxima of the Fourier component magnitudes by a number larger than 1.

9. The device of claim 8, wherein the Fourier component magnitudes are absolute values of Fourier coefficients of the FDHR signals.

10. The device of claim 1, wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost and further providing a peak boost to Fourier component magnitudes of the FDHR signals by multiplying local maxima of the Fourier component magnitudes by a number larger than 1.

11. A computer-implemented method for determining a heart rate (HR) of a user comprising:

providing HR signals corresponding to HR values;

selecting a first path of HR values over a first sequence of HR measurements in accordance with a given criteria, wherein the first path includes a selection of a respective candidate HR value for each HR measurement of the first sequence of HR measurements; and

selecting a second path of HR values over a second sequence of HR measurements in accordance with the given criteria, the second sequence of HR measurements including the first sequence of HR measurements and at least one additional HR measurement subsequent to the first sequence of HR measurements,

wherein the second path includes at least one different selection of a respective candidate HR value for at least one of the HR measurements of the first sequence of HR measurements.

12. The method of claim 11, wherein the given criteria is based on consecutive Fourier coefficient magnitudes of corresponding consecutive HR values along each of the first and second paths and differences in consecutive HR values along each of the first and second paths.

13. The method of claim 12, further comprising providing the HR values by transforming the HR signals into frequency domain HR signals (FDHR signals) and adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost.

14. The method of claim 13, wherein the Fourier component magnitudes are absolute values of Fourier coefficients of the FDHR signals.

15. The method of claim 11, wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and low pass filtering Fourier component magnitudes of the FDHR signals.

16. The method of claim 15, wherein the low pass filtering is provided by utilizing a Gaussian convolution.

17. The method of claim 11, wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and providing a peak boost to Fourier component magnitudes of the FDHR signals.

18. The method of claim 17, wherein the peak boost multiplies each local maxima of the Fourier component magnitudes by a number larger than 1.

19. The method of claim 18, wherein the Fourier component magnitudes are absolute values of Fourier coefficients of the FDHR signals.

20. The method of claim 11, wherein providing the HR values includes transforming the HR signals into frequency domain HR signals (FDHR signals) and adding together at least a fundamental and first harmonic of Fourier component magnitudes of the FDHR signals corresponding to the HR signals to provide a harmonic boost and further providing a peak boost to Fourier component magnitudes of the FDHR signals by multiplying local maxima of the Fourier component magnitudes by a number larger than 1.