SIGNAL PROCESSING SYSTEMS AND METHODS USING MULTIPLE SIGNALS

• US 20100014723A1
• Filed: 10/01/2008
• Published: 01/21/2010
• Est. Priority Date: 07/15/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James Nicholas
• Granted Patent: US 9,031,627 B2
• Time in Patent Office: Days
• US Class Current: 382/128
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

According to embodiments, techniques for signal processing using multiple signals are disclosed. A first scalogram may be generated from a first signal and a second scalogram may be generated from a second signal. A modified or masked scalogram may then be generated based on the first and second scalograms. The modified scalogram may then be used to determine at least one physiological parameter. In some embodiments, one or both of the first signal and the second signal may be photoplethysmograph (PPG) signals obtained from a pulse oximeter.

Claims

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

receiving a first signal and a second signal;

performing a continuous wavelet transform on the first signal and the second signal to produce a first transformed signal and a second transformed signal;

generating a first scalogram based at least in part on the first transformed signal;

generating a second scalogram based at least in part on the second transformed signal;

generating a scalogram mask based at least in part on the first scalogram and the second scalogram;

filtering one of the first scalogram and the second scalogram using at least the scalogram mask to produce a filtered scalogram; and

determining a physiological parameter based at least in part on the filtered scalogram.

2. The method of claim 1, wherein generating the scalogram mask comprises summing the first scalogram and the second scalogram.

3. The method of claim 1, wherein generating the scalogram mask comprises subtracting the first scalogram from the second scalogram.

4. The method of claim 1, wherein generating the scalogram mask comprises applying a scaling factor to either the first scalogram or the second scalogram before summing or subtracting the first and second scalograms.

5. The method of claim 1, wherein the first signal and/or the second signal is a photoplethysmograph MPG) signal.

6. The method of claim 1, wherein generating a scalogram mask comprises determining the regions where one of the first scalogram and the second scalogram exceed a threshold value.

7. The method of claim 1 further comprising generating a plurality of additional filtered scalograms based at least in part on a plurality of different scaling factors.

8. The method of claim 7 further comprising:

computing a summation of each of the filtered scalogram and the plurality of additional filtered scalograms; and

generating a Time-Scale Metric (TSM) plot of the summations plotted against the summations respective scaling factors.

9. The method of claim 1 wherein determining a physiological parameter comprises determining the physiological parameter in the time-scale domain.

10. The method of claim 1 wherein determining a physiological parameter comprises performing an inverse wavelet transform of the filtered scalogram and determining the physiological parameter in the time domain.

11. A method for generating a reference signal, comprising:

receiving first and second signals;

generating a first scalogram based at least in part on the first signal;

generating a second scalogram based at least in part on the second signal;

generating a modified scalogram based at least in part on the first scalogram and the second scalogram, and

generating a reference signal based at least in part on the modified scalogram.

12. The method of claim 11, wherein the reference signal is generally representative of noise components in the first signal or the second signal.

13. The method of claim 11, wherein the reference signal is representative of one or more desired signal components in the first signal or the second signal.

14. The method of claim 11 further comprising sending the reference signal to an adaptive filter.

15. A system for determining a physiological parameter, comprising:

a sensor capable of generating a first signal and a second signal; and

a processor capable of;

performing a continuous wavelet transform on the first signal and the second signal to produce a first transformed signal and a second transformed signal;

generating a first scalogram based at least in part on the first transformed signal;

generating a second scalogram based at least in part on the second transformed signal;

generating a scalogram mask based at least in part on the first scalogram and the second scalogram;

filtering one of the first scalogram and the second scalogram using at least the scalogram mask to produce a filtered scalogram; and

determining a physiological parameter based at least in part on the filtered scalogram.

16. The system of claim 15, wherein the processor is capable of summing the first scalogram and the second scalogram.

17. The system of claim 15, wherein the processor is capable of subtracting the first scalogram from the second scalogram.

18. The system of claim 15, wherein the processor is capable of applying a scaling factor to either the first scalogram or the second scalogram before summing or subtracting the first and second scalograms.

19. The system of claim 15, wherein at least one of the first signal and the second signal is a photoplethysmograph (PPG) signal.

20. The system of claim 15, wherein the processor is capable of determining the regions where one of the first scalogram and the second scalogram exceeds a threshold value.

21. The system of claim 15 wherein the processor is capable of generating a plurality of additional filtered scalograms based at least in part on a plurality of different scaling factors.

22. The system of claim 21 wherein the processor is capable of:

computing a summation of each of the filtered scalogram and the plurality of additional filtered scalograms; and

generating a Time-Scale Metric (TSM) plot of the summations plotted against the summations'"'"' respective scaling factors.

23. The system of claim 15 wherein the processor is capable of determining the physiological parameter in the time-scale domain.

24. The system of claim 15 wherein the processor is capable of performing an inverse wavelet transform of the filtered scalogram and determining the physiological parameter in the time domain.

25. A computer-readable medium for use in for determining a physiological parameter, the computer-readable medium having computer program instructions recorded thereon for:

receiving a first signal and a second signal;

performing a continuous wavelet transform on the first signal and the second signal to produce a first transformed signal and a second transformed signal;

generating a first scalogram based at least in part on the first transformed signal;

generating a second scalogram based at least in part on the second transformed signal;

generating a scalogram mask based at least in part on the first scalogram and the second scalogram;

filtering one of the first scalogram and the second scalogram using at least the scalogram mask to produce a filtered scalogram; and

determining a physiological parameter based at least in pail on the filtered scalogram.