Estimating transform values using signal estimates

• US 8,364,225 B2
• Filed: 05/20/2009
• Issued: 01/29/2013
• Est. Priority Date: 05/20/2009
• 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.
• Primary Examiner(s): SZMAL, BRIAN SCOTT
• Application Number:
  US12/469,491
• Publication Number:
  US 20100298676A1
• Time in Patent Office: 1,350 Days
• Field of Search: 600/323, 600/310, 600/480, 600/485, 600/502, 600/529, 600/336, 708/400, 702/19
• US Class Current: 600/336
• CPC Class Codes: A61B 2562/0233 Special features of optical sensors or probes classified in A61B5/00
• CPC Class Codes: A61B 2562/046 in a matrix array
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/726 using Wavelet transforms

Abstract

According to embodiments, estimated values for a signal transform may be generated using estimated values for the signal. Signal parameters may then be determined based on the estimated signal transform. A first portion of a signal may be obtained. A second portion of the signal may be estimated. The second portion of the signal may correspond to a portion of the that is unknown, that is not yet available and/or that is obscured by noise and/or artifacts. A transform (e.g., a continuous wavelet transform) of both of the signal portions may be performed. One or more parameters corresponding to the signal may then be determined from transformed signal.

Claims

1. A method for estimating transform values using a signal estimate comprising:

obtaining a first portion of a biological signal from a sensor;

estimating a second portion of the signal based at least in part on the first portion of the signal;

performing a transform of the signal based at least in part on the first portion of the signal and the second portion of the signal; and

determining a biological parameter corresponding to the signal based at least in part on the transformed signal.

2. The method of claim 1 wherein the biological signal comprises a photoplethysmograph (PPG) signal and wherein the determined parameter comprises blood oxygen saturation level, respiration rate, respiration effort metric, pulse rate, and/or blood pressure.

3. The method of claim 1 wherein the transform comprises a continuous wavelet transform.

4. The method of claim 3 wherein estimating the second portion of the signal further comprises:

selecting a range of scales for the continuous wavelet transform; and

determining a length for the second portion of the signal based at least in part on the selected range of scales.

5. The method of claim 4 wherein selecting the range of scales for the continuous wavelet transform comprises locating one or more features within a continuous wavelet transform of the signal.

6. The method of claim 1 wherein estimating the second portion of the signal comprises:

determining an amplitude value of the first portion of the signal;

estimating the determined amplitude value as a constant value for the second signal.

7. The method of claim 1 wherein estimating the second portion of the signal comprises:

fitting a function to the first portion of the signal; and

estimating the second signal using the function.

8. The method of claim 1 wherein estimating the second portion of the signal comprises:

determining that the first portion of the signal is a known signal type;

determining one or more characteristic values of the first portion PPG signal; and

estimating the second signal by generating a signal portion of the known signal type having at least one of the determined characteristic values.

9. The method of claim 1 further comprising determining an estimation confidence value for the second portion of the signal.

10. The method of claim 1 further comprising updating the transform of the signal in response to obtaining signal values corresponding to the second portion of the signal.

11. The method of claim 1 wherein the second signal portion is generally adjacent to an end of the first signal portion.

12. The method of claim 1 wherein the second signal portion is generally within the first signal portion.

13. A system for processing a signal to estimate transform values using a signal estimate, the system comprising:

a sensor to receive data indicative of a biological signal;

a processor coupled to the sensor, wherein the processor is capable of;

obtaining a first portion of the received signal;

estimating a second portion of the signal based at least in part on the first portion of the signal;

performing a wavelet transform of the signal based at least in part on the first portion of the signal and the second portion of the signal; and

determining a biological parameter generally corresponding to the signal based at least in past on the transformed signal.

14. The system of claim 13 wherein the biological signal comprises a photoplethysmograph (PPG) signal and wherein the determined parameter comprises blood oxygen saturation level, respiration rate, respiration effort metric, pulse rate, and/or blood pressure.

15. The system of claim 13 wherein the processor is further capable of:

selecting a range of scales for the continuous wavelet transform; and

determining a length for the second portion of the signal based at least in pail on the selected range of scales.

16. The system of claim 15 wherein selecting the range of scales for the continuous wavelet transform comprises locating one or more features within a continuous wavelet transform of the signal.

17. The system of claim 13 wherein the processor is further capable of:

determining an amplitude value of the first portion of the signal;

estimating the determined amplitude value as a constant value for the second signal.

18. The system of claim 13 wherein the processor is further capable of:

generally fitting a function to the first portion of the signal; and

estimating the second signal using the function.

19. The system of claim 13 wherein the processor is further capable of:

determining that the first portion of the signal is a known signal type;

determining one or more characteristic values of the first portion PPG signal; and

estimating the second signal by generating a signal portion of the known signal type having at least one of the determined characteristic values.

20. The system of claim 13 wherein the processor is further capable of determining an estimation confidence value for the second portion of the signal.