Systems And Methods For Resolving The Continuous Wavelet Transform Of A Signal

• US 20110028810A1
• Filed: 07/30/2009
• Published: 02/03/2011
• Est. Priority Date: 07/30/2009
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Addison, Paul Stanley, Watson, James Nicholas, Van Slyke, Braddon M.
• Granted Patent: US 8,594,759 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• 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 5/726 using Wavelet transforms
• CPC Class Codes: G06F 17/148 Wavelet transforms
• CPC Class Codes: G06F 2218/06 by applying a scale-space analysis, e.g. using wavelet analysis

Abstract

According to an embodiment, techniques for estimating scalogram energy values in a wedge region of a scalogram are disclosed. A pulse oximetry system including a sensor or probe may be used to receive a photoplethysmograph (PPG) signal from a patient or subject. A scalogram, corresponding to the obtained PPG signal, may be determined. In an approach, energy values in the wedge region of the scalogram may be estimated by performing convolution-based or convolution-like operations on the obtained PPG signal, or a transformed version thereof, and the scalogram may be updated according to the estimated values. In an approach, a deskewing technique may be used to align data prior to adding the data to the scalogram. In an approach, one or more signal parameters may be determined based on the resolved and estimated values of the scalogram.

Claims

1. A method for processing a scalogram, the method comprising:

receiving a signal from a signal generator;

using processing equipment for;

generating the scalogram based at least in part on a continuous wavelet transform of the signal,

sampling the signal,

convolving the samples of the signal with wavelet coefficients to produce skewed scalogram samples,

deskewing the skewed scalogram samples to produce scalogram update samples,

updating the scalogram by adding the scalogram update samples to the scalogram, and

determining information from the signal based at least in part on the updated scalogram; and

outputting the information to an output device.

2. The method of claim 1, wherein the signal comprises a photoplethysmograph (PPG) signal.

3. The method of claim 1, wherein the updating is performed at a refresh rate that depends at least in part on an expected time-rate of change of at least one patient parameter.

4. The method of claim 1, wherein the output device comprises a display.

5. The method of claim 1, wherein the convolving is performed at least in part by at least one processor, and wherein the at least one processor performs one or more matrix multiplications.

6. The method of claim 1, wherein the wavelet coefficients correspond to a truncated Morlet wavelet.

7. The method of claim 2, wherein the information comprises a patient respiration rate.

8. The method of claim 2, wherein the information comprises a patient oxygen saturation level.

9. The method of claim 2, wherein the information comprises a patient respiration effort level.

10. The method of claim 2, wherein the sampling is performed at a substantially constant time-rate.

11. A system for processing a scalogram, the system comprising:

a sensor for receiving a signal from a signal generator;

one or more processors coupled to the sensor, wherein the one or more processors are configured to;

generate the scalogram based at least in part on a continuous wavelet transform of the signal,

sample the signal,

convolve the samples of the signal with wavelet coefficients to produce skewed scalogram samples,

deskew the skewed scalogram samples to produce scalogram update samples,

update the scalogram by adding the scalogram update samples to the scalogram, and

determine information from the signal based at least in part on the updated scalogram; and

output the information to an output device.

12. The system of claim 11, wherein the signal comprises a photoplethysmograph (PPG) signal.

13. The system of claim 11, wherein the updating is performed at a refresh rate that depends at least in part on an expected time-rate of change of at least one patient parameter.

14. The system of claim 11, wherein the output device comprises a display.

15. The system of claim 11, wherein the convolving is performed at least in part by at least one processor, and wherein the at least one processor performs one or more matrix multiplications.

16. The system of claim 11, wherein the wavelet coefficients correspond to a truncated Morlet wavelet.

17. The system of claim 12, wherein the information comprises a patient respiration rate.

18. The system of claim 12, wherein the information comprises a patient oxygen saturation level.

19. The system of claim 12, wherein the information comprises a patient respiration effort level.

20. The system of claim 12, wherein the sampling is performed at a substantially constant time-rate.