System and method for determining changes in a body state

• US 9,420,958 B2
• Filed: 03/15/2013
• Issued: 08/23/2016
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Original Assignee: Honda Motor Co., Ltd. (Honda Motor Company)
• Inventors: Hall, Charles William Jr., Fung, Kin C., Dick, Timothy J.
• Primary Examiner(s): Cattungal, Sanjay
• Application Number:
  US13/843,077
• Publication Number:
  US 20140276112A1
• Time in Patent Office: 1,257 Days
• Field of Search: 600508-530, 600/407, 600/437, 600473-480
• US Class Current: 1/1
• 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 5/02405 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 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/6893 Cars
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 8/02 Measuring pulse or heart rate

Abstract

A method and a system for determining changes in a body state of an individual including receiving a signal from a monitoring system, where the signal indicates a measurement of cardiac activity of the individual over a period of time and determining at least one signal feature, where the signal feature is a reoccurring event of the signal over the period of time. The method also includes determining a first interval between two successive signal features and determining a second interval between two successive first intervals. A derivative is calculated based on the second interval. Changes in the body state are identified based on the derivative.

Claims

1. A computer-implemented method for determining changes in a body state of an individual, comprising:

receiving a signal from a monitoring system, said signal indicating a measurement of cardiac activity over a period of time;

determining at least one signal feature and a value representative of the signal feature, wherein the signal feature is a reoccurring event of the signal over the period of time;

calculating a first interval as a difference between a value representative of a first signal feature and a value representative of a second signal feature, wherein the first signal feature and the second signal feature are successive in the signal between two successive signal features;

calculating a second interval as a difference between a value representative of a third signal feature and a value representative of a fourth signal feature, wherein the third signal feature and the fourth signal feature are successive in the signal;

calculating a difference between the first interval and the second interval between two successive first intervals;

calculating a derivative based on the difference between the first interval and the second interval; and

identifying changes in the body state based on the derivative.

2. The computer-implemented method of claim 1, wherein the signal is measured by a contactless sensor.

3. The computer-implemented method of claim 2, wherein the signal is one of an electric signal, an acoustic or an optical signal representing the measurement of cardiac activity.

4. The computer-implemented method of claim 1, wherein the signal feature is a peak of the signal.

5. The computer-implemented method of claim 1, wherein the signal is an electrocardiogram signal and the signal feature is an R wave of the electrocardiogram signal.

6. The computer-implemented method of claim 1, wherein identifying changes in the body state based on the derivative further includes extracting a series of contiguous heart rate accelerations or decelerations based on the derivative.

7. The computer-implemented method of claim 6, wherein the series of contiguous heart rate accelerations or decelerations correlate to a change in the body state.

8. The computer-implemented method of claim 6, wherein identifying changes in the body state based on the derivative further includes calculating a threshold based on a count of the contiguous heart rate accelerations or decelerations in the series.

9. The computer-implemented method of claim 7, wherein identifying changes in the body state based on the derivative further includes generating a graphic representation and identifying changes in the body state as a function of the graphic representation.

15. The computer-implemented method of claim 1, wherein a set of contiguous derivatives having a negative sign correlates to a burst of sympathetic activity and a set of contiguous derivatives having a positive sign correlates to a burst of parasympathetic activity.

24. The computer-implemented method of claim 1, wherein calculating the derivative further includes calculating the derivative as a fraction of the difference between the first interval and the second interval, and the first interval.

10. A computer-implemented method for analyzing transitions in a body state, comprising:

receiving a signal from an individual indicating a measurement of cardiac activity over a period of time;

calculating a plurality of first interval values, wherein each interval value of the plurality of first interval values is calculated as a difference between two successive signal features of the signal;

calculating a plurality of second interval values, wherein each interval of the plurality of second intervals is calculated as a difference between two successive first intervals of the plurality of first intervals;

calculating a plurality of derivatives based on each of the plurality of second interval values;

extracting a plurality of heart rate accelerations or decelerations from the plurality of derivatives; and

identifying a transition in the body state based on the plurality of heart rate accelerations or decelerations.

11. The computer-implemented method of claim 10, further including transmitting the signal from a monitoring system associated with the individual, wherein said signal is one of an electrical signal, an acoustic signal or an optical representing the measurement of cardiac activity.

12. The computer-implemented method of claim 11, wherein receiving a signal further includes processing the signal into a plurality of waveforms, each one of said waveforms indicating a heart beat.

13. The computer-implemented method of claim 10, wherein a sign of each derivative in the plurality of derivatives indicates a heart rate acceleration or deceleration.

14. The computer-implemented method of claim 10, wherein identifying a transition in the body state further includes generating a graphical representation illustrating a first set of contiguous derivatives from the plurality of derivatives wherein each derivative of the first set of contiguous derivatives have the same sign and a second set of contiguous derivatives from the plurality of derivatives where each derivative of the second set of contiguous derivatives have the same sign, and identifying the transitions in the body state as a function of a distance between the first set and the second set.

25. The computer-implemented method of claim 10, wherein the plurality of first interval values, the plurality of second interval values, and the plurality of derivatives are expressed in vector form.

16. A computer system for determining changes in a body state of an individual, comprising:

a monitoring system configured to monitor cardiac activity;

a signal receiving module configured to receive a signal from the monitoring system, said signal representing a measurement of cardiac activity over a period of time;

a feature determination module configured to determine a signal feature and a value representative of the signal feature, wherein the signal feature is a reoccurring event of said signal over the period of time;

an interval determination module configured to calculate a first interval as a difference between a value representative of a first signal feature and a value representative of a second signal feature, wherein the first signal feature and the second signal feature are successive in the signal,

configured to calculate a second interval as a difference between a value representative of a third signal feature and a value representative of a fourth signal feature, wherein the third signal feature and the fourth signal feature are successive in the signal,

and configured to calculate a difference between the first interval and the second interval;

a derivative calculation module configured to calculate a derivative of a heart rate based on the difference between the first interval and the second interval; and

an identification module configured to identify changes in the body state based on the derivative.

17. The computer system of claim 16, wherein the monitoring system further includes a plurality of contactless sensors for monitoring cardiac activity of the individual.

18. The computer system of claim 16, wherein the signal is one of an electrical signal, an acoustic signal or an optical signal representing the measurement of cardiac activity.

19. The computer system of claim 16, the identification module further configured to extract a series of contiguous heart rate accelerations or decelerations based on the derivative.

20. The computer system of claim 19, wherein the series of contiguous heart rate accelerations or decelerations correlate to a change in the body state.

21. A non-transitory computer-readable medium storing computer-executable instructions that when executed by a computer, which includes at least a processor, cause the computer to perform a method, the method comprising:

receiving, using at least the processor, a signal indicating a plurality of cardiac cycles of an individual over a period of time;

detecting, using at least the processor, a signal feature and a value representative of the signal feature, wherein the signal feature is a reoccurring event of the signal over the period of time; and

calculating, using at least the processor, a first interval as a difference between a value representative of a first signal feature and a value representative of a second signal feature, wherein the first signal feature and the second signal feature are successive in the signal;

calculating, using at least the processor, a second interval as a difference between a value representative of a third signal feature and a value representative of a fourth signal feature, wherein the third signal feature and the fourth signal feature are successive in the signal;

calculating, using at least the processor, a difference between the first interval and the second interval;

calculating, using at least the processor, a derivative based on the difference between the first interval and the second interval; and

identifying, using at least the processor, changes in a body state based on the derivative.

22. The non-transitory computer-readable medium of claim 21, wherein identifying changes in the body state based on the derivative further includes extracting a series of contiguous heart rate accelerations or decelerations based on the derivative.

23. The non-transitory computer-readable medium of claim 22, wherein the series of contiguous heart rate accelerations or decelerations correlate to changes in the body state.