Signal Processing Mirroring Technique

• US 20090326351A1
• Filed: 05/07/2009
• Published: 12/31/2009
• Est. Priority Date: 06/30/2008
• Status: Abandoned Application

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James
• Application Number:
  US12/437,311
• Publication Number:
  US 20090326351A1
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7225 Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

Embodiments may include systems and methods capable of processing an original signal by selecting and mirroring portions of the signal to create a new signal for further analysis. In an embodiment, the signal may be a photoplethysmograph (PPG) signal and the new signal may be further analyzed using continuous wavelet transforms. Any suitable number of reconstructed new signals may be created from the original signal and scalograms may be derived at least in part from the new signals. Ridges may be extracted from the scalograms of the new signals and secondary scalograms may be further derived from the ridges. A sum along amplitudes technique may be applied to a selected scalogram and may be plotted as a function of the scale of the scalogram. Desired information, such as respiration information within the original signal, may be identified from the plot.

Claims

1. A signal processing method comprising:

selecting a first portion of an original signal;

mirroring the first portion of the original signal about a first vertical axis to create a mirrored first portion; and

analyzing the mirrored first portion.

2. The method of claim 1, wherein selecting the first portion of the original signal comprises:

identifying a first local minimum value of the original signal;

identifying a subsequent first local maximum value of the original signal; and

selecting the first portion to be the portion of the original signal between the first local minimum value of the original signal and the subsequent first local maximum of the original signal.

3. The method of claim 1, further comprising selecting a subsequent second portion of the original signal;

mirroring the second portion of the original signal about a second vertical axis to create a mirrored second portion; and

analyzing the mirrored second portion.

4. The method of claim 3, wherein selecting the second portion of the original signal comprises:

identifying a second local minimum value of the original signal, wherein the second local minimum value is subsequent to the first local minimum value of the original signal;

identifying a subsequent second local maximum value of the original signal; and

selecting the second portion to be the portion of the original signal between the second local minimum value of the original signal and the subsequent second local maximum of the original signal.

5. The method of claim 3, further comprising combining the mirrored first portion and the mirrored second portion to create a new signal, and analyzing the new signal.

6. The method of claim 5, wherein the first portion of the original signal is selected from a larger first segment of the original signal, wherein the second portion of the original signal is selected from a larger second segment of the original signal, and wherein the first and the second segments are consecutive segments, the method further comprising:

adjusting the length of the new signal by stretching or compressing the new signal to be substantially identical to a combined length of the first and the second segments.

7. The method of claim 5, wherein the first portion of the original signal is selected from a larger first segment of the original signal and wherein the second portion of the original signal is selected from a larger second segment of the original signal, the method further comprising:

adjusting the length of the mirrored first portion by stretching or compressing the mirrored first portion to be a first size; and

adjusting the length of the mirrored second portion by stretching or compressing the mirrored second portion to be a second size.

8. The method of claim 7, further comprising:

adjusting the amplitude of the mirrored first portion based at least in part on the length adjustment of the mirrored first portion; and

adjusting the amplitude of the mirrored second portion based at least in part on the length adjustment of the mirrored second portion.

9. The method of claim 7, wherein the first portion and the second portion of the original signal are selected based at least in part on a second derivative of the original signal.

10. The method of claim 7, wherein analyzing the new signal comprises transforming the new signal into a transformed signal using a wavelet transform.

11. The method of claim 10, further comprising generating a scalogram based at least in part on the transformed signal.

12. The method of claim 11, wherein the original signal is a photoplethysmograph signal from a user, the method further comprising analyzing the scalogram to obtain respiration information of the user.

13. The method of claim 11, wherein the first portion of the original signal and the second portion of the original signal are up strokes of the photoplethysmograph signal.

14. The method of claim 11, wherein the first portion of the original signal and the second portion of the original signal are down strokes of the photoplethysmograph signal.

15. A system for processing a signal, the system comprising:

an input signal generator for generating the signal;

a processor coupled to the input signal generator, wherein the processor is configured to select a first portion of an original signal, mirror the first portion of the original signal about a first vertical axis to create a mirrored first portion, select a subsequent second portion of the original signal, mirror the second portion of the original signal about a second vertical axis to create a mirrored second portion, combine the mirrored first portion and the mirrored second portion to create a new signal, and analyze the new signal; and

an output coupled to the processor, wherein the output is configured to display the new signal analyzed by the processor.

16. The system of claim 15, wherein the input signal generator is a pulse oximeter coupled to a sensor.

17. The system of claim 15, wherein the processor is further configured to adjust an amplitude of the mirrored first portion based at least in part on a length adjustment of the mirrored first portion, and adjust an amplitude of the mirrored second portion based at least in part on a length adjustment of the mirrored second portion.

18. The system of claim 15, wherein analyzing the new signal comprises transforming the new signal into a transformed signal using a wavelet transform.

19. The system of claim 15, wherein the processor is further configured to generate a scalogram based at least in part on the transformed signal.

20. The system of claim 19, wherein the original signal is a photoplethysmograph signal from a user, the processor further configured to analyze the scalogram to obtain respiration information of the user.