Systems And Methods For Signal Rephasing Using The Wavelet Transform

• US 20120310051A1
• Filed: 05/31/2011
• Published: 12/06/2012
• Est. Priority Date: 05/31/2011
• Status: Abandoned Application

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul, Watson, James, McGonigle, Scott
• Application Number:
  US13/149,755
• Publication Number:
  US 20120310051A1
• Time in Patent Office: Days
• US Class Current: 600/301
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

Methods and systems are disclosed for defining a physiological parameter. A first physiological signal is transformed into in a complex transform space, the transformed signal having a magnitude and a phase. The transformed signal is rotated by altering its phase. The rotated signal is inverted, and the inverted signal is aligned in phase with a second physiological signal. The aligned inverted signal and the second physiological signal are combined to form a combined signal indicative of the physiological parameter.

Claims

1. A method for defining a physiological parameter, comprising:

generating a transformed signal in a complex transform space, the transformed signal based on a first physiological signal, and the transformed signal having a magnitude and a phase;

generating a rotated signal by altering the phase of the transformed signal;

generating an inverted signal by inverting the rotated signal, wherein the inverted signal is aligned in phase with a second physiological signal; and

generating a combined signal indicative of the physiological parameter by combining the aligned inverted signal with the second physiological signal.

2. The method of claim 1, wherein at least one of the first physiological signal and the second physiological signal is a photoplethysmograph signal measured by a pulse oximeter.

3. The method of claim 2, wherein the photoplethysmograph signal includes at least one respiratory component.

4. The method of claim 3, wherein generating the transformed signal is done by transforming the photoplethysmograph signal using a continuous wavelet transform.

5. The method of claim 3, wherein generating the transformed signal is done by transforming the photoplethysmograph signal using a short time Fourier transform.

6. The method of claim 3, wherein a phase shift value is used to alter the phase of the transformed signal.

7. The method of claim 6, wherein the phase shift value is a minimum value of a median of distances between corresponding peaks of the first and second physiological signals.

8. The method of claim 3, further comprising aligning at least one additional physiological signal to the second physiological signal by:

generating an additional transformed signal in a complex transform space, the additional transformed signal based on the additional physiological signal, and the additional transformed signal having a magnitude and a phase;

generating an additional rotated signal by altering the phase of the additional transformed signal; and

generating an additional inverted signal by inverting the additional rotated signal, wherein the additional inverted signal is aligned in phase with the second physiological signal.

9. The method of claim 8, wherein the phase of the transformed signal is altered by a phase shift value that is different from a phase shift value for altering the additional transformed signal.

10. The method of claim 3, wherein transforming the first physiological signal into the complex transform space reduces noise in the signal.

11. The method of claim 3, wherein a first photoplethysmograph signal is received from a first sensing device positioned at a first part of a subject'"'"'s body, and a second photoplethysmograph signal is received from a second sensing device positioned at a second part of the subject'"'"'s body.

12. The method of claim 3, wherein combining the aligned inverted signal and the second physiological signal comprises normalizing and summing the signals.

13. The method of claim 3, further comprising extracting a rate of respiration from the combined signal.

14. The method of claim 3, wherein the transformed signal has a plurality of phases, and generating a rotated signal comprises altering more than one of the phases of the transformed signal.

15. A system for displaying a physiological parameter comprising:

a signal input configured to receive at least one physiological signal of a subject from a sensing device;

electronic processing equipment coupled to the signal input, the electronic processing equipment configured for;

receiving the at least one physiological signal;

aligning the at least one physiological signal with a reference physiological signal; and

generating a combined signal indicative of the physiological parameter by combining the at least one physiological signal with the reference physiological signal; and

a monitor for displaying a physiological parameter representative of the combined signal.

16. The system of claim 15, wherein aligning a first physiological signal with the reference physiological signal comprises:

generating a transformed signal in a complex transform space, the transformed signal based on the first physiological signal, and the transformed signal having a magnitude and a phase;

generating a rotated signal by altering the phase of the transformed signal; and

generating an inverted signal by inverting the rotated signal, wherein the inverted signal is aligned in phase with the reference physiological signal.

17. The system of claim 16, wherein the at least one physiological signal is a photoplethysmograph signal measured by a pulse oximeter.

18. The system of claim 17, wherein the photoplethysmograph signal includes at least one respiratory component.

19. The system of claim 16, wherein generating the transformed signal involves using a continuous wavelet transform.

20. The system of claim 16, wherein generating the transformed signal involves using a short time Fourier transform.

21. The system of claim 16, wherein a phase shift value is used to alter the phase of the transformed signal.

22. The system of claim 21, wherein the phase shift value is a minimum value of a median of the distances between corresponding peaks of the physiological signals.

23. The system of claim 16, wherein the electronic processing equipment is further configured for aligning at least one additional physiological signal to the reference physiological signal:

24. The system of claim 16, wherein the monitor is further configured to display the combined signal.

25. The system of claim 17, wherein:

the signal input is configured to receive a photoplethysmograph signal of the subject from a first sensing device and a photoplethysmograph signal of the subject from a second sensing device positioned at a different part of the body of the subject from the first device;

the first physiological signal is the signal input from the first sensing device; and

the reference physiological signal is the signal input from the second sensing device.

26. The system of claim 18, wherein the physiological parameter is a respiration rate.

27. The system of claim 16, wherein the transformed signal has a plurality of phases, and generating a rotated signal comprises altering more than one of the phases of the transformed signal.

28. Computer-readable medium for use in defining a physiological parameter, the computer-readable medium having computer program instructions recorded thereon for:

generating a transformed signal in a complex transform space, the transformed signal based on a first physiological signal, and the transformed signal having a magnitude and a phase;

generating a rotated signal by altering the phase of the transformed signal;

generating an inverted signal by inverting the rotated signal, wherein the inverted signal is aligned in phase with a second physiological signal; and

generating a combined signal indicative of the physiological parameter by combining the aligned inverted signal with the second physiological signal.