Systems and methods for estimating values of a continuous wavelet transform

• US 8,346,333 B2
• Filed: 07/30/2009
• Issued: 01/01/2013
• Est. Priority Date: 07/30/2009
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Watson, James Nicholas, Addison, Paul Stanley, Van Slyke, Braddon M.
• Primary Examiner(s): WINAKUR, ERIC FRANK
• Application Number:
  US12/512,132
• Publication Number:
  US 20110028813A1
• Time in Patent Office: 1,251 Days
• Field of Search: 600/310, 600/322, 600/323, 600/324, 600/330, 600/336, 600/502, 600/529, 356/41, 702/19, 702/189, 702/190, 700/1, 365/94
• US Class Current: 600/336
• 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 5/1455 using optical sensors, e.g. spectral photometrical oximeters
• 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
• CPC Class Codes: G06F 17/148 Wavelet transforms
• CPC Class Codes: G06F 2218/08 Feature extraction

Abstract

According to embodiments, 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 arrangement, energy values in the wedge region of the scalogram may be estimated by calculating a set of estimation locations in the wedge region and estimating scalogram energy values at each location. In an arrangement, scalogram energy values may be estimated based on an estimation scheme and by combining scalogram values in a vicinity region. In an arrangement, the vicinity region may include energy values in a resolved region of the scalogram and previously estimated energy values in the wedge region of the scalogram. In an arrangement, 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 to estimate one or more energy values in a wedge region of the scalogram, the method comprising:

receiving a signal; and

using processing equipment for;

transforming the signal based at least in part on a continuous wavelet transform;

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

estimating the one or more energy values in the wedge region of the scalogram based at least in part on an estimation scheme;

determining one or more signal parameters of the signal based at least in part on the one or more estimated energy values; and

outputting the determined one or more signal parameters to an output device.

2. The method of claim 1, wherein estimating the one or more energy values comprises:

determining a plurality of estimation points and a set of locations corresponding to the plurality of estimation points in the wedge region of the scalogram;

determining a set of estimation parameters corresponding to the estimation scheme; and

determining a size and shape of a vicinity region.

3. The method of claim 2, wherein the determined size and shape of the vicinity region is based, at least in part, on one or more characteristics of the one or more signal parameters.

4. The method of claim 2, wherein the determined size and shape of the vicinity region is based, at least in part, on one or more characteristics of a patient.

5. The method of claim 1, wherein the signal comprises a photoplethysmograph (PPG) signal received from a sensor.

6. The method of claim 1, wherein the one or more signal parameters comprises a patient oxygen saturation level.

7. The method of claim 1, wherein the signal parameter comprises a patient respiration rate.

8. The method of claim 1, wherein the method further comprises:

determining one or more confidence metrics based at least in part on the one or more estimated energy values; and

determining if the one or more confidence metrics satisfy a constraint set.

9. The method of claim 8, wherein determining the one or more confidence metrics comprises:

determining energy values and energy structure in a pulse band of the scalogram; and

determining energy values and energy structure in a noise band of the scalogram.

10. The method of claim 1, wherein the estimate of at least one energy value in the one or more estimated energy values is based, at least in part, on a set of resolved energy values in a resolved region of the scalogram and a set of estimated energy values in the wedge region of the scalogram.

11. A system for processing a scalogram to estimate one or more energy values in a wedge region of the scalogram, the system comprising:

a sensor capable of generating a signal; and

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

receiving the signal from the sensor;

transforming the signal based at least in part on a continuous wavelet transform;

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

estimating the one or more energy values in the wedge region of the scalogram based at least in part on an estimation scheme;

determining one or more signal parameters of the signal based at least in part on the one or more estimated energy values; and

outputting the determined one or more signal parameters to an output device.

12. The system of claim 11, wherein estimating the one or more energy values comprises:

determining a plurality of estimation points and a set of locations corresponding to the plurality of estimation points in the wedge region of the scalogram;

determining a set of estimation parameters corresponding to the estimation scheme; and

determining a size and shape of a vicinity region.

13. The system of claim 12, wherein the determined size and shape of the vicinity region is based, at least in part, on one or more characteristics of the one or more signal parameters.

14. The system of claim 12, wherein the determined size and shape of the vicinity region is based, at least in part, on one or more characteristics of a patient.

15. The system of claim 11, wherein the signal comprises a photoplethysmograph (PPG) signal received from a sensor.

16. The system of claim 11, wherein the one or more signal parameters comprises a patient oxygen saturation level.

17. The system of claim 11, wherein the one or more signal parameters comprises a patient respiration rate.

18. The system of claim 11, wherein the one or more processors are further capable of:

determining one or more confidence metrics based at least in part on the one or more estimated energy values; and

determining if the one or more confidence metrics satisfy a constraint set.

19. The system of claim 18, wherein determining the one or more confidence metrics comprises:

determining energy values and energy structure in a pulse band of the scalogram; and

determining energy values and energy structure in a noise band of the scalogram.

20. The system of claim 11, wherein the estimate of at least one energy value in the one or more estimated energy values is based, at least in part, on a set of resolved energy values in a resolved region of the scalogram and a set of estimated energy values in the wedge region of the scalogram.