System and method for monitoring cardiorespiratory parameters

• US 8,834,364 B2
• Filed: 10/31/2007
• Issued: 09/16/2014
• Est. Priority Date: 11/01/2006
• Status: Active Grant

• Current Assignee: ResMed Sensor Technologies Limited (ResMed Incorporated)
• Original Assignee: ResMed Sensor Technologies Limited (ResMed Incorporated)
• Inventors: Heneghan, Conor, Hanley, Conor, De Chazal, Philip
• Primary Examiner(s): Thomson, Bill
• Assistant Examiner(s): SANDS, DAVIN K
• Application Number:
  US12/376,771
• Publication Number:
  US 20100179438A1
• Time in Patent Office: 2,512 Days
• Field of Search: None
• US Class Current: 600/301
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• 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 5/0507 using microwaves or terahertz waves
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1102 Ballistocardiography
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/6802 Sensor mounted on worn items
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/6895 Sport equipment

Abstract

An apparatus, system, and method is disclosed for monitoring the motion, breathing, heart rate of humans in a convenient and low-cost fashion, and for deriving and displaying useful measurements of cardiorespiratory performance from the measured signals. The motion, breathing, and heart rate signals are obtained through a processing applied to a raw signal obtained in a non-contact fashion, typically using a radio-frequency sensor. Processing into separate cardiac and respiratory components is described. The heart rate can be determined by using either spectral or time-domain processing. The respiratory rate can be calculated using spectral analysis. Processing to derive the heart rate, respiratory sinus arrhythmia, or a ventilatory threshold parameter using the system is described. The sensor, processing, and display can be incorporated in a single device which can be worn or held close to the body while exercising (e.g., in a wristwatch or mobile phone configuration), or alternately placed in a fixed piece of exercise equipment at some distance form the body (e.g., in a treadmill dash panel), and may also be integrated with other sensors, such as position locators.

Claims

1. A system for measuring and analyzing respiration and cardiac activity, the system comprising:

one or more radio-frequency Doppler sensors configured to receive a reflected radio-frequency (RF) signal off a living subject, wherein the RF signal comprises a pulsed RF signal;

a mixer that mixes the reflected signal over a predefined period with an RF signal transmitted toward the living subject, the transmitted signal being associated with the reflected signal; and

a processor configured to analyze the reflected signal to determine a measurement of respiration and cardiac activity of the living subject;

wherein the processor is configured to calculate a parameter of cardiorespiratory performance by relating the measured cardiac activity to the measured respiration over a defined period of measurement.

4. The system of claim 1, further comprising an output arranged to output the cardiac activity or respiration.

5. The system of claim 1, further comprising a transmitter that generates the radio frequency signals that are reflected off the living subject.

6. The system of claim 5, wherein the generated radio frequency signal is emitted at a power level safe for use when the living subject is a human.

7. The system of claim 1, wherein the processor is further configured to derive one or more signals related to non-cardiorespiratory bodily movement of the living subject.

8. The system of claim 1, wherein the processor is configured to recognize the respiration or cardiac activity of the living subject using a processed time-domain signal derived from the reflected radio-frequency signal.

9. The system of claim 8, wherein the recognized cardiac activity comprises heart beats of the living subject recognized by identifying peaks in the processed time-domain signal.

10. The system of claim 8, wherein the cardiac activity comprises heart beats of the living subject recognized by a time-domain correlation of the received signal with a prototypical cardiac signal.

11. The system of claim 1, wherein the processor is configured to recognize the respiration or cardiac activity of the living subject using frequency domain processing of the received signal.

12. The system of claim 11, wherein the recognized respiration comprises a breathing rate of the living subject.

13. The system of claim 1, further comprising a filter, wherein the processor is configured to measure an energy content of a filtered signal, wherein periods of bodily motion of the living subject are recognized by comparing the energy content to a predetermined energy value.

14. The system of claim 1, further comprising multiple sensors configured to receive the reflected RF signal.

15. The system of claim 14, in which a plurality of signals provided by the multiple sensors are processed simultaneously to output distinct components of bodily movement.

16. The system of claim 1, wherein the processor is configured to calculate a parameter of respiratory sinus arrhythmia using measured heart rate and breathing rate information.

17. The system of claim 1, wherein the processor is configured to calculate a parameter of respiratory sinus arrhythmia using cross-spectral analysis of measured heart rate and breathing rate signals.

18. The system of claim 4, wherein the output comprises a display.

19. The system of claim 18, wherein the display is configured to visually signal a heart rate of the living subject to the user.

20. The system of claim 18, wherein the display is configured to visually signal a breathing rate of the living subject to the user.

21. The system of claim 1, wherein the defined period of measurement is a predefined distance.

22. The system of claim 1, wherein the defined period of measurement is a predefined time.

23. The system of claim 1, wherein the processor is configured to audibly signal a heart beat of the living subject.

24. The system of claim 1, wherein the processor is configured to calculate a heart rate of the living subject using spectral analysis that removes periods of measurement containing artifacts therein.

25. The system of claim 1, wherein the processor is configured to calculate a breathing rate of the living subject using spectral analysis that removes periods of measurement containing artifacts therein.

26. The system of claim 1, further comprising multiple sensors operating at different frequencies, wherein a relatively low frequency is used to estimate a large bodily movement of the living subject, and a relatively high frequency is used to estimate a smaller movement of the living subject.

27. The system of claim 1, further comprising a positioning system configured to monitor a location of the living subject.

28. The system of claim 4, further comprising an enclosure configured to enclose the one or more sensors, the processor, and the output.

29. The system of claim 28, wherein the enclosure is suitable for being held in a hand of the user.

30. The system of claim 1, wherein the RF signal comprises a single frequency RF signal.

31. The system of claim 1, wherein the RF signal comprises multiple RF signals each at a different frequency.

32. The system of claim 1, wherein the RF signal comprises a continuous wave (CW) signal.

33. The system of claim 32, wherein the CW signal comprises an frequency modulated continuous wave (FMCW) signal.

38. The system of claim 7, wherein the processor derives one or more signals related to non-cardiorespiratory bodily movement by recognizing periods of high energy content.

40. The system of claim 1, further comprising one or more motion sensors configured to receive the reflected RF signal off the living subject.

41. The system of claim 1, further comprising one or more radio-frequency sensors configured to receive a reflected radio-frequency (RF) signal off the living subject.

2. A system for measuring and analyzing respiration and cardiac activity, the system comprising:

one or more radio-frequency Doppler sensors configured to receive a reflected radio-frequency (RF) signal off a living subject, wherein the RF signal comprises a single RF frequency; and

a processor configured to analyze the reflected signal to determine a measurement of respiration and cardiac activity of the living subject;

wherein the processor is configured to calculate a parameter of cardiorespiratory performance by relating the measured cardiac activity to the measured respiration over a defined period of measurement.

3. A system for measuring and analyzing respiration and cardiac activity, the system comprising:

two or more radio-frequency Doppler sensors, each sensor configured to receive at a different radio frequency a reflected radio-frequency (RF) signal off a living subject;

a processor configured to analyze the reflected signals to determine a measurement of respiration and cardiac activity of the living subject,

wherein the processor is configured to calculate a parameter of cardiorespiratory performance by relating the measured cardiac activity to the measured respiration over a defined period of measurement.

34. A method for measuring and analyzing respiration and cardiac activity, the method comprising:

receiving a pulsed radio-frequency (RF) signal, at at least one radio-frequency Doppler sensor, reflected from the living subject;

analyzing the reflected signal to produce measurements relating to the respiration and cardiac activity of the living subject; and

calculating a parameter of cardiorespiratory performance, using a processor, by relating the measured cardiac activity to the measured respiration over a defined period of measurement.

35. The method of claim 34, further comprising outputting selected measurements or parameters.

36. The method of claim 35, wherein said outputting comprises displaying one or more measurements relating to the cardiac activity of the living subject.

37. The method of claim 35, wherein said outputting comprises displaying one or more measurements relating to the respiration of the living subject.

39. The method of claim 34, further comprising pre-processing the reflected signal to reduce the effect of motion artifacts.