Devices and methods for heart rate measurement and wrist-watch incorporating same

• US 20040228217A1
• Filed: 06/16/2003
• Published: 11/18/2004
• Est. Priority Date: 05/13/2003
• Status: Active Grant

• Current Assignee: Dayton Technologies Limited
• Original Assignee: Century Ocean Corporation Limited
• Inventors: Szeto, Chi Cheong
• Granted Patent: US 7,379,770 B2
• Time in Patent Office: Days
• US Class Current: 368/11
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/02455 provided with high/low alarm devices
• CPC Class Codes: A61B 5/35 by template matching
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: G04B 47/00 Time-pieces combined with other articles which do not interfere with the running or the time-keeping of the time-piece clockwork cases for special purposes G04B37/12; clocks with magnifying glass built in the face G04B39/00; time-pieces in which parts or cases produce special effects, e.g. aesthetic effects, G04B45/00, particularly with inscriptions or pictures moved by hand G04B45/003, with specially shaped cases or parts G04B45/0069; combination of writing or drawing implements with devices for indicating time B43K29/087; combined with cameras, projectors, or photographic printing apparatus G03B29/00

Abstract

Method of measuring the heart rate of a human being, including the steps of:—

receiving a stream of signals containing ECG signals,

selecting a reference QRS complex from said stream of signals according to a first set of predetermined criteria, and characterising the electrical signal characteristics of said reference QRS complex,

detecting and characterising a first QRS complex from said stream of signals which is immediately adjacent to said reference QRS complex in the time domain, fulfils a second set of predetermined criteria, and satisfies a threshold level of similarity with said reference QRS complex,

evaluating the instantaneous heart rate from said first QRS complex and said reference QRS complex when the similarity between said first QRS complex and said reference QRS complex fulfils a predetermined threshold.

Claims

1. Method of measuring the heart rate of a human being, including the steps of:

—

receiving a stream of signals containing ECG signals,

selecting a reference QRS complex from said stream of signals, according to a first set of predetermined criteria, and

characterising the electrical signal characteristics of said reference QRS complex,

detecting and characterising a first QRS complex from said stream of signals which is immediately adjacent to said reference QRS complex in the time domain, fulfils a second set of predetermined criteria, and satisfies a threshold level of similarity with said reference QRS complex,

evaluating the instantaneous heart rate from said first QRS complex and said reference QRS complex when the similarity between said first QRS complex and said reference QRS complex fulfils a predetermined threshold.

2. A method of claim 1, wherein said first set of predetermined criteria for selecting said reference QRS complex includes the occurrence of the maximum signal peak of a predetermined minimum amplitude within a predetermined time from the beginning of receipt of said stream of signals.

3. A method of claim 2, wherein said predetermined time from the beginning of receipt of said stream of signals within which said peak amplitude must occur being in the region of 1.6 seconds.

4. A method of claim 1, wherein the characterising of the electrical signal characteristics of said reference QRS complex includes the taking and recording of a plurality of samples of the amplitude of said reference QRS complex at a plurality of sampling times within a predetermined window of time, the boundaries of said predetermined window of time being determined with reference to at least a signal characteristic of said reference QRS complex.

5. A method of claim 4, wherein the signal characteristic of said reference QRS complex for determining the boundaries of said window of time being the peak amplitude of said reference QRS complex.

6. A method of claim 4, wherein the characterising of said first QRS complex includes the taking and recording of a plurality of samples of the amplitude of said first QRS complex within a predetermined window of time, the time domain location of said window being determined with reference to said reference QRS complex.

7. A method of claim 6, wherein the time span of said predetermined window of time being adequate to cover a complete QRS complex.

8. A method of claim 6, wherein said second set of predetermined criteria includes the occurrence of a signal peak of a predetermined minimum amplitude within a predetermined time frame from said reference QRS complex.

9. A method of claim 8, wherein said second set of criteria includes the occurrence of the peak of said first QRS complex in the region of 0.25 to 1.5 seconds from the peak of said reference QRS complex.

10. A method of claim 8, wherein the lower and upper boundaries of said time window from said reference QRS complex being determined respectively by the maximum and minimum possible time periods of normal QRS complexes of normal human beings.

11. A method of claim 6, wherein said second set of predetermined criteria includes the occurrence of a first signal with a sufficient degree of similarity with said reference QRS complex within a predetermined time frame determined by the maximum and minimum time period of a normal QRS complex of a normal human being.

12. A method of claim 1, wherein the comparison of similarity between said reference QRS complex and said first QRS complex includes the correlation of the corresponding samples of said reference QRS complex and said first QRS complex.

13. A method of claim 12, wherein the corresponding samples of said reference QRS complex and said first QRS complex being contained in a predetermined window of time, the centre of said predetermined window of time respectively for characterising said reference QRS complex and said first QRS complex being the amplitude peak of said reference QRS complex and said first QRS complex.

14. A method of claim 13, wherein the sampling intervals and the width of said windows being the same.

15. A method of claim 13, wherein said width of said sampling window being in the region of 0.1 seconds.

16. A method of claim 12, wherein the correlation between the corresponding samples of said reference QRS complex and said first QRS complex includes the summation of the multiplication of the relative amplitudes of said corresponding samples.

17. A method of claim 2, wherein the detection of said first QRS complex includes the continuous seeking of a signal fulfilling said threshold level of similarity with said reference QRS complex within a predetermined window of time.

18. A method of claim 1, further including the step of noise filtering before the characterising of said reference QRS complex.

19. A method of claim 18, wherein said noise filtering includes the filtering of noise due to AC mains.

20. A method of claim 19, wherein said noise filtering further includes the filtering of noise common in the detection of QRS complexes.

21. A method of claim 1, further including the detection of a second QRS complex from said stream of signals, said second electrical signal being immediately adjacent either to said reference QRS complex or said first detected electrical signal, said second QRS complex fulfils a third set of predetermined criteria and satisfying a threshold level of similarity with said reference QRS complex.

22. A method of claim 21, wherein said third set of predetermined criteria includes the occurrence of said second QRS complex within a predetermined time frame from said first QRS complex, said forecast time frame being determined by the heart rate evaluated from said reference QRS complex and said first QRS complex.

23. A method of claim 22, wherein the boundary of said forecast time frame being symmetrical about the predicted time period evaluated with reference to said evaluated heart rate.

24. A method of claim 23, wherein said boundary being 12.5% of said predicted time period evaluated from said heart rate.

25. A method of claim 21, wherein said threshold level of similarity between said second QRS complex and said reference QRS complex being within a predetermined range of said threshold level of similarity between said reference QRS complex and said first QRS complex.

26. A portable heart rate measuring device, including:

—

means for receiving a stream of signals containing QRS complexes,

means for selecting a reference QRS complex from said stream of signals according to a first set of predetermined criteria, and characterising the electrical signal characteristics of said reference QRS complex,

means for detecting and characterising a first QRS complex from said stream of signals which is immediately adjacent to said reference QRS complex in the time domain, fulfils a second set of predetermined criteria, and satisfies a threshold level of similarity with said reference QRS complex,

means for comparing said first QRS complex with said reference QRS complex and evaluating the similarity between said detected first electrical signal and said reference QRS complex,

means for evaluating the instantaneous heart rate from said first QRS complex and said reference QRS complex when the similarity between said first QRS complex and said reference QRS complex fulfils a predetermined threshold.

27. A wrist-watch including a heart rate measuring device of claim 26.

28. A wrist-watch according to claim 27, further including heart rate sensing electrodes on the watch case.

29. A wrist-watch according to claim 28, further including noise filtering means.

30. A wrist-watch according to claim 27, wherein said noise filtering means include a notch filter.