Noninvasive Motion and Respiration Monitoring System

• US 20100109875A1
• Filed: 10/08/2009
• Published: 05/06/2010
• Est. Priority Date: 10/08/2008
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Original Assignee: Board of Regents of the University of Texas System (University of Texas System)
• Inventors: Berg, Christopher, Valdez, David C., Ayon, Arturo A.
• Granted Patent: US 8,502,679 B2
• Time in Patent Office: Days
• US Class Current: 340/573.100
• CPC Class Codes: A61B 5/113 occurring during breathing
• CPC Class Codes: A61B 5/4818 Sleep apnoea
• CPC Class Codes: A61B 5/6892 Mats
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G16H 20/30 relating to physical therapies or activities, e.g. physiotherapy, acupressure or exercising
• CPC Class Codes: G16H 40/67 for remote operation

Abstract

A non-invasive motion and respiration monitor receives impulses from a subject'"'"'s movement, heartbeat, and respiration. The raw signal is biased and digitized, and a signal processor applies a Fast Fourier Transform to the signal. The transformed signal is filtered to isolate the component representing heart rate from the component representing respiration. An Inverse Fast Fourier Transform is then applied to the component signals, which are sent to a processor. The processor is programmed to detect irregularities in the respiration and heart rate. If severe irregularities or complete cessation is detected in either signal, a mechanical stimulator is actuated to try to stimulate the subject, and an alarm is sounded to alert a caregiver such as a parent or nurse.

Claims

1. A method of non-invasively monitoring heart rate and respiration of a subject comprising the steps of:

receiving a time-domain signal from a impulse-sensitive sensor array;

applying a Fast Fourier Transform function to the time-domain signal to convert to a frequency-domain signal;

filtering the frequency-domain signal through a first bandpass filter to provide a frequency-domain signal representing a first bio-indicator;

applying an inverse Fast Fourier Transform function to the frequency-domain first bio-indicator signal to provide a time-domain first bio-indicator signal.

2. The method of claim 1 further comprising providing an alert if the first bio-indicator signal is absent for a time span.

3. The method of claim 2 wherein the time span is two seconds.

4. The method of claim 3 wherein the time span is between two seconds and twenty seconds.

5. The method of claim 1 wherein the bandpass filter provides a pass band between 0.4 and 0.98 hertz.

6. The method of claim 5 wherein the first bio-indicator is a respiration rate.

7. The method of claim 1 wherein the bandpass filter provides a pass band between 0.98 and 2.54 Hz.

8. The method of claim 7 wherein the first bio-indicator is a heart rate.

9. The method of claim 1 further comprising:

filtering the frequency-domain signal through a second bandpass filter to provide a frequency-domain signal representing a second bio-indicator; and

applying an inverse Fast Fourier Transform function to the frequency-domain heart rate signal to provide a time-domain second bio-indicator signal.

10. The method of claim 9 wherein:

the first bandpass filter provides a pass band between 0.4 and 0.98 hertz; and

the second bandpass filter provides a pass band between 0.98 and 2.54 hertz.

11. The method of claim 10 wherein:

the first bio-indicator is a respiration rate; and

the second bio-indicator is a heart rate.

12. The method of claim 11 further comprising providing an alert if either bio-indicator is absent for a time span.

13. The method of claim 12 wherein the time span is two seconds.

14. The method of claim 12 wherein the span is between two seconds and twenty seconds.

15. A non-invasive monitoring system comprising:

a sensor array comprising impulse-sensitive transducers, the sensor array disposed on a surface for holding a subject to be monitored and configured to provide a time-domain output waveform;

a signal processor configured to receive the time-domain output waveform and to;

apply a Fast Fourier Transform to the time-domain output waveform to provide a frequency-domain waveform;

filter the frequency-domain waveform through a bandpass filter to provide a frequency-domain bio-indicator signal;

apply an inverse Fast Fourier Transform to the frequency-domain bio-indicator signal to provide a time-domain bio-indicator signal.

16. The system of claim 15 wherein the sensor array comprises piezoelectric sensors.

17. The system of claim 15 wherein the output of the sensor array is biased to a desired output level by means of a voltage divider.

18. The system of claim 15 wherein the signal processor is further configured to provide an alert signal if the bio-indicator signal is absent for a time span.

19. The system of claim 18 wherein the time span is two seconds.

20. The system of claim 18 wherein the time span is between two and twenty seconds.

21. The system of claim 15 wherein:

the sensor array provides the time-domain output waveform to the signal processor by means of an analog-to-digital converter; and

the signal processor is a field-programmable gate array configured to receive a digital input signal.

22. The system of claim 15 wherein the bandpass filter is configured to provide a pass band between 0.4 and 0.98 hertz, and wherein the bio-indicator is a respiration rate.

23. The system of claim 15 wherein the bandpass filter is configured to provide a pass band between 0.98 and 2.54 hertz, and wherein the bio-indicator is a heart rate.

24. The system of claim 15 wherein the signal processor is further configured to:

filter the frequency-domain waveform through a second bandpass filter to provide a second frequency-domain bio-indicator signal; and

apply an inverse Fast Fourier Transform to the second frequency-domain bio-indicator signal to provide a second time-domain bio-indicator signal.

25. The system of claim 24 wherein:

the first bandpass filter provides a pass band between 0.4 and 0.98 hertz, and wherein the first bio-indicator is a respiration rate; and

the second bandpass filter provides a pass band between 0.98 and 2.54 hertz, and wherein the second bio-indicator is a heart rate.

26. The system of claim 24 wherein the signal processor is further configured to provide an alert signal if either bio-indicator is absent for a time span.

27. The system of claim 26 wherein the time span is two seconds.

28. The system of claim 26 wherein the time span is between two and twenty seconds.