Wearable heart rate monitor

• US 9,456,787 B2
• Filed: 06/03/2014
• Issued: 10/04/2016
• Est. Priority Date: 06/22/2012
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Venkatraman, Subramaniam, Yuen, Shelten Gee Jao
• Primary Examiner(s): JANG, CHRISTIAN YONGKYUN
• Application Number:
  US14/295,076
• Publication Number:
  US 20140288436A1
• Time in Patent Office: 854 Days
• US Class Current: 1/1
• 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 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0245 by using sensing means generating electric signals, i.e. ECG signals
• CPC Class Codes: A61B 5/1118 Determining activity level
• CPC Class Codes: A61B 5/1123 Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: A61B 5/318 Heart-related electrical modalities, e.g. electrocardiography [ECG]
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6824 Arm or wrist
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses
• 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 5/742 using visual displays A61B5/339 takes precedence

Abstract

A biometric monitoring device is used to determine a user'"'"'s heart rate by using a heartbeat waveform sensor and a motion detecting sensor. In some embodiments, the device collects collecting concurrent output data from the heartbeat waveform sensor and output data from the motion detecting sensor, detects a periodic component of the output data from the motion detecting sensor, and uses the periodic component of the output data from the motion detecting sensor to remove a corresponding periodic component from the output data from the heartbeat waveform sensor. From this result, the device may determine and present the user'"'"'s heart rate.

Claims

1. A method of determining a user'"'"'s heart rate using a worn biometric monitoring device comprising a plurality of sensors including a heartbeat waveform sensor and a motion detecting sensor, wherein the heartbeat waveform sensor comprises at least one light source and at least one photodetector, the method comprising:

(a) pulsing the at least one light source to emit light pulses in a time period when the biometric monitoring device is worn by the user;

(b) operating the at least one photodetector to detect the light pulses emitted by the at least one light source after the light pulses interact with the user'"'"'s tissue, and obtaining, through the at least one photodetector, output data from the heartbeat waveform sensor, wherein the output data from the heartbeat waveform sensor contains information about the user'"'"'s heart rate and is susceptible to motion artifacts;

(c) operating the motion detecting sensor in the time period when the biometric monitoring device is worn by the user, and obtaining output data from the motion detecting sensor, wherein the output data from the motion detecting sensor provides information about the user'"'"'s periodic physical movements other than heartbeats;

(d) determining a periodic component of the output data from the motion detecting sensor;

(e) processing the output data from the heartbeat waveform sensor to remove the periodic component from the output data from the heartbeat waveform sensor;

(f) using the output data from the motion detecting sensor to determine a range of expected heart rates;

(g) determining the user'"'"'s heart rate by excluding from consideration one or more putative heart rates outside of the range of expected heart rates from either the output data produced in (e), or from data derived therefrom, and further determining the user'"'"'s heart rate within the range of expected heart rates; and

(h) presenting the user'"'"'s heart rate.

2. The method of claim 1, wherein determining the range of expected heart rates comprises:

(i) determining the user'"'"'s stationary heart rate when another output data from the motion detecting sensor indicates that the user is substantially stationary;

(ii) determining the user'"'"'s activity level and/or activity type from the periodic component of the output data from the motion detecting sensor; and

(iii) determining the range of expected heart rates from the user'"'"'s stationary heart rate determined in (i) and the user'"'"'s activity level and/or activity type determined in (ii).

3. The method of claim 2, wherein a minimum expected heart rate in the range of expected heart rates is greater than the user'"'"'s stationary heart rate determined in (i).

4. The method of claim 2, wherein determining the user'"'"'s activity type comprises inferring the activity type from information contained in the output data from the motion detecting sensor or detecting a manually entered selection of activity type.

5. The method of claim 1, wherein determining the range of expected heart rates comprises determining the user'"'"'s step rate from the output data from the motion detecting sensor.

6. The method of claim 1, wherein determining the user'"'"'s heart rate comprises calculating the spectral density of the output data produced in (e).

7. The method of claim 1, wherein the user'"'"'s periodic physical movements other than heart beats comprise a wearer'"'"'s limb movements.

8. The method of claim 1, wherein the motion detecting sensor is an accelerometer, a gyroscope, or a GPS sensor.

9. The method of claim 1, wherein:

pulsing the at least one light source comprises pulsing the at least one light source at a first frequency; and

operating the at least one photodetector comprises detecting light pulses at the first frequency.

10. The method of claim 9, wherein pulsing the at least one light source at the first frequency comprises emitting a succession of light pulses of substantially constant intensity.

11. The method of claim 1, wherein presenting the user'"'"'s heart rate comprises presenting the heart rate on the worn biometric monitoring device or on an external device that periodically communicates with the worn biometric monitoring device.

12. The method of claim 1, wherein determining a range of expected heart rates comprises:

determining the user'"'"'s activity type from the output data from the motion detecting sensor; and

determining the range of expected heart rates based on the determined activity type.

13. The method of claim 1, wherein determining the user'"'"'s heart rate comprises, before excluding the one or more putative heart rates from consideration, transforming the output data from the motion detecting sensor into a frequency domain to obtain spectral representations of the putative heart rates.

14. The method of claim 1, wherein the worn biometric monitoring device further comprises one or more processors, and wherein (d)-(g) are performed by the one or more processors.

15. The method of claim 1, wherein the worn biometric monitoring device further comprises a display device, and wherein presenting the user'"'"'s heart rate in (h) comprises visually displaying the user'"'"'s heart rate on the display device.

16. A wearable fitness monitoring device comprising:

a motion sensor configured to provide output corresponding to motion by a user wearing the fitness monitoring device;

a heartbeat waveform sensor comprising at least one light source and at least one photodetector; and

control logic comprising instructions for;

(a) pulsing the at least one light source to emit light pulses in a time period when the wearable fitness monitoring device is worn by the user;

(b) operating the at least one photodetector to detect the light pulses emitted by the at least one light source after the light pulses interact with the user'"'"'s tissue, and obtaining, through the at least one photodetector, output data from the heartbeat waveform sensor, wherein the output data from the heartbeat waveform sensor contains information about the user'"'"'s heart rate and is susceptible to motion artifacts;

(c) operating the motion detecting sensor in the time period when the wearable fitness monitoring device is worn by the user, and obtaining output data from the motion detecting sensor, wherein the output data from the motion detecting sensor provides information about the user'"'"'s periodic physical movements other than heartbeats;

(d) determining a periodic component of the output data from the motion detecting sensor;

(e) processing the output data from the heartbeat waveform sensor to remove the periodic component from the output data from the heartbeat waveform sensor;

(f) using the output data from the motion detecting sensor to determine a range of expected heart rates;

(g) determining the user'"'"'s heart rate by excluding from consideration one or more putative heart rates outside of the range of expected heart rates from either the output data produced in (e), or from data derived therefrom, and determining the user'"'"'s heart rate within the range of expected heart rates; and

(f) presenting the user'"'"'s heart rate.

17. The wearable fitness monitoring device of claim 16, wherein the heartbeat waveform sensor is a photoplethysmographic sensor comprising (i) a periodic light source, (ii) a photo detector positioned to receive periodic light emitted by the periodic light source after interacting with the user'"'"'s skin, and (iii) circuitry determining the user'"'"'s heart rate from output of the photo detector.

18. The wearable fitness monitoring device of claim 17, wherein the photoplethysmographic sensor comprises two periodic light sources straddling the photo detector.

19. The wearable fitness monitoring device of claim 17, wherein the photoplethysmographic sensor further comprises a housing having a recess in which the photo detector is disposed.

20. The wearable fitness monitoring device of claim 19, wherein the housing of the photoplethysmographic sensor further comprises a second recess in which the periodic light source is disposed.

21. The wearable fitness monitoring device of claim 20, wherein the housing protrudes at least about 1 mm above a base surface of the wearable fitness monitoring device arranged to press against the user'"'"'s skin when worn.

22. The wearable fitness monitoring device of claim 17, wherein the photoplethysmographic sensor further comprises an in-mold-labeling (IML) film over the photo detector and the periodic light source.

23. The wearable fitness monitoring device of claim 16, wherein the instructions for determining the range of expected heart rates comprise instructions for:

(i) determining the user'"'"'s stationary heart rate when another output data from the motion detecting sensor indicates that the user is substantially stationary;

(ii) determining the user'"'"'s activity level and/or activity type from the periodic component of the output data from the motion detecting sensor; and

(iii) determining the range of expected heart rates from the user'"'"'s stationary heart rate determined in (i) and the user'"'"'s activity level and/or activity type determined in (ii).

24. The wearable fitness monitoring device of claim 23, wherein a minimum expected heart rate in the range of expected heart rates is greater than the user'"'"'s stationary heart rate determined in (i).

25. The wearable fitness monitoring device of claim 23, wherein the instructions for determining the user'"'"'s activity type comprise instructions for inferring the activity type from information contained in the output data from the motion detecting sensor or detecting a manually entered selection of activity type.

26. The wearable fitness monitoring device of claim 16, wherein the instructions for determining the range of expected heart rates comprise instructions for determining the user'"'"'s step rate from the output data from the motion detecting sensor.

27. The wearable fitness monitoring device of claim 16, wherein the instructions for determining the user'"'"'s heart rate comprise the instructions for calculating the spectral density of the output data produced in (e).

28. The wearable fitness monitoring device of claim 16, wherein the motion detecting sensor is an accelerometer, a gyroscope, or a GPS sensor.

29. The wearable fitness monitoring device of claim 16, wherein:

pulsing the at least one light source comprises pulsing the at least one light source at a first frequency; and

operating the at least one photodetector comprises detecting light pulses at the first frequency.

30. The wearable fitness monitoring device of claim 29, wherein the instructions for pulsing the at least one light source at the first frequency comprise the instructions for emitting a succession of light pulses of substantially constant intensity.

31. The wearable fitness monitoring device of claim 16, wherein the instructions for presenting the user'"'"'s heart rate comprise instructions for presenting the heart rate on the wearable fitness monitoring device or on an external device that periodically communicates with the wearable fitness monitoring device.

32. The wearable fitness monitoring device of claim 16, wherein the instructions for determining a range of expected heart rates comprises instructions for:

determining the user'"'"'s activity type from the output data from the motion detecting sensor; and

determining the range of expected heart rates based on the determined activity type.

33. The wearable fitness monitoring device of claim 16, wherein the instructions for determining the range of expected heart rates comprise instructions for:

(i) determining the user'"'"'s stationary heart rate when another output data from the motion detecting sensor indicates that the user is substantially stationary;

(ii) determining the user'"'"'s step rate from the output data from the motion detecting sensor; and

(iii) determining the range of expected heart rates from the user'"'"'s stationary heart rate determined in (i) and the user'"'"'s step rate determined in (ii).

34. The wearable fitness monitoring device of claim 16, wherein determining the user'"'"'s heart rate comprises, before excluding the one or more putative heart rates from consideration, transforming the output data from the motion detecting sensor into a frequency domain to obtain spectral representations of the putative heart rates.