Method and apparatus for subject monitoring

• US 6,506,153 B1
• Filed: 06/04/2001
• Issued: 01/14/2003
• Est. Priority Date: 09/02/1998
• Status: Expired due to Fees

• Current Assignee: Med-Dev Limited
• Original Assignee: Med-Dev Limited
• Inventors: Littek, Amim, Littek, Celeste Sabra
• Primary Examiner(s): Nasser, Robert L.
• Assistant Examiner(s): MALLARI, PATRICIA C
• Application Number:
  US09/786,234
• Time in Patent Office: 589 Days
• Field of Search: 600/300, 600/301, 600/481, 600/483, 600/484, 600/500-502, 600/529, 600/534, 600/595, 297/217.1, 297/463.2, 297/DIG.4
• US Class Current: 600/301
• 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 5/1071 measuring angles, e.g. using goniometers A61B5/1123 takes precedence
• CPC Class Codes: H10N 30/302 Sensors

Abstract

A method of monitoring a subject (7) in a vehicle seat (6), the method including: a) acquiring a target signal from the subject with a piezoelectric transducer (1) provided in or on the vehicle seat; b) processing the target signal to extract a cardiac signal (24) and/or a respiratory signal (25); and c) outputting the cardiac and/or respiratory signal. A method of monitoring a subject including: a) acquiring a target signal from the subject; b) bandpass filtering (27) the target signal in accordance with a set of cardiac filter coefficients to extract a cardiac signal (24); c) bandpass filtering (30) the target signal in accordance with a set of respiratory filter coefficients to extract a respiratory signal (25); d) adapting (29, 33) the set of cardiac filter coefficients so as to reduce artefacts in the cardiac signal; e) adapting (50, 32) the set of respiratory filter coefficients so as to reduce artefacts in the respiratory signal; and f) outputting the cardiac and respiratory signal signals.

Claims

1. A method of monitoring a subject, comprising the steps of:

a) acquiring a signal from the subject with a transducer;

b) filtering the signal in accordance with a set of cardiac filter coefficients to extract a cardiac signal;

c) filtering the signal in accordance with a set of respiratory filter coefficients to extract a respiratory signal;

d) adapting the set of cardiac filter coefficients so as to reduce artefacts in the cardiac signal;

e) adapting the set of respiratory filter coefficients so as to reduce artefacts in the respiratory signal;

f) outputting the cardiac and respiratory signals from respective signal chains; and

g) reducing signal artefacts by the provision of a cross-adaption feedback path between the cardiac and respiratory signal chains.

2. A method according to claim 1 wherein step d) comprises autocorrelating the cardiac signal to generate a cardiac autocorrelation signal, and adapting the set of cardiac filter coefficients in accordance with the cardiac autocorrelation signal.

3. A method according to claim 1 wherein step e) comprises autocorrelating the respiratory signal to generate a respiratory autocorrelation signal, and adapting the set of respiratory filter coefficients in accordance with the respiratory autocorrelation signal.

4. A method according to claim 1 wherein the cross-adaption feedback path reduces signal artefacts by scaling the cardiac signal to generate a scaled cardiac signal, and subtracting the scaled cardiac signal from the respiratory signal.

5. A method according to claim 1 wherein the cross-adaption feedback path reduces signal artefacts by scaling the respiratory signal to generate a scaled respiratory signal, and subtracting the scaled respiratory signal from the cardiac signal.

6. A method according to claim 1 wherein step a) comprises acquiring a noise signal from the subject'"'"'s environment, acquiring a target signal from the subject, and generating the signal by subtracting the noise signal from the target signal.

7. A method according to claim 1 wherein the subject is located in a vehicle seat.

8. A method according to claim 1 further comprising displaying the cardiac and/or respiratory signal, or a parameter obtained therefrom.

9. A method according to claim 1 wherein the transducer comprises a flexible sheet of piezoelectric material.

10. A method according to claim 1 further comprising analyzing the cardiac and/or respiratory signal to obtain a parameter indicative of a physiological state of the subject.

11. A method according to claim 10 further comprising generating an alarm when the parameter crosses a predetermined threshold.

12. A method according to claim 10 further comprising activating or deactivating a control device associated with a vehicle'"'"'s drive control mechanism when the parameter crosses a predetermined threshold.

13. A method according to claim 10 wherein the parameter is indicative of a sleep state of the subject.

14. A method according to claim 10 wherein the parameter comprises respiratory rate or cardiac rate.

15. Apparatus for monitoring a human or animal subject comprising:

a) a transducer for acquiring a signal from the subject;

b) a cardiac signal chain including a cardiac adaptive filter for filtering the signal in accordance with a set of cardiac filter coefficients to extract a cardiac signal;

means for adapting the set of cardiac filter coefficients so as to reduce artefacts in the cardiac signal; and

means for outputting the cardiac signal;

c) a respiratory signal chain including a respiratory adaptive filter for filtering the signal in accordance with a set of respiratory filter coefficients to extract a respiratory signal;

means for adapting the set of respiratory filter coefficients so as to reduce artefacts in the respiratory signal; and

means for outputting the respiratory signal; and

d) a cross-adaption feedback path between the cardiac and respiratory signal chains.

16. Apparatus according to claim 15 wherein the transducer comprises a piezoelectric transducer.

17. Apparatus according to claim 15 comprising means for autocorrelating the cardiac signal to generate a cardiac autocorrelation signal, and means adapting the set of cardiac filter coefficients in accordance with the cardiac autocorrelation signal.

18. Apparatus according to claim 15 comprising means for autocorrelating the respiratory signal to generate a respiratory autocorrelation signal, and means for adapting the set of respiratory filter coefficients in accordance with the respiratory autocorrelation signal.

19. Apparatus according to claim 15 wherein the cross-adaption feedback path comprises means for scaling the cardiac signal to generate a scaled cardiac signal, and means for subtracting the scaled cardiac signal from the respiratory signal.

20. Apparatus according to claim 15 wherein the cross-adaption feedback path comprises means for scaling the respiratory signal to generate a scaled respiratory signal, and means for subtracting the scaled respiratory signal from the cardiac signal.

21. Apparatus according to claim 15 comprising means for acquiring a noise signal from the subject'"'"'s environment, means for acquiring a target signal from the subject, and means for generating the signal by subtracting the noise signal from the target signal.

22. Apparatus according to claim 15 further comprising means for displaying the cardiac and/or respiratory signal, or a parameter obtained therefrom.

23. Apparatus according to claim 15 wherein the transducer comprises a flexible sheet of piezoelectric material.

24. Apparatus according to claim 15 further comprising means for analyzing the cardiac and/or respiratory signal to obtain a parameter indicative of a physiological state of the subject.

25. Apparatus according to claim 24 further comprising means for generating an alarm when the parameter crosses a predetermined threshold.

26. Apparatus according to claim 24 further comprising means for activating or deactivating a control device associated with a vehicle'"'"'s drive control mechanism when the parameter crosses a predetermined threshold.

27. Apparatus according to claim 24 wherein the parameter is indicative of a sleep state of the subject.

28. Apparatus according to claim 24 wherein the parameter comprises respiratory rate or cardiac rate.

29. Apparatus for monitoring a subject in a vehicle, the apparatus comprising:

a vehicle seat;

a transducer provided in or on the vehicle seat for acquiring a signal from the subject;

a cardiac signal chain including a cardiac adaptive filter for filtering the signal in accordance with a set of cardiac filter coefficients to extract a cardiac signal;

means for adapting the set of cardiac filter coefficients so as to reduce artefacts in the cardiac signal; and

means for outputting the cardiac signal;

a respiratory signal chain including a respiratory adaptive filter for filtering the signal in accordance with a set of respiratory filter coefficients to extract a respiratory signal;

means for adapting the set of respiratory filter coefficients so as to reduce artefacts in the respiratory signal; and

means for outputting the respiratory signal; and

a cross-adaption feedback path between the cardiac and respiratory signal chains.