SYSTEMS AND METHODS FOR IDENTIFYING PORTIONS OF A PHYSIOLOGICAL SIGNAL USABLE FOR DETERMINING PHYSIOLOGICAL INFORMATION

• US 20130289413A1
• Filed: 04/30/2012
• Published: 10/31/2013
• Est. Priority Date: 04/30/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: Ochs, James, McGonigle, Scott, Addison, Paul, Watson, James
• Granted Patent: US 9,179,876 B2
• Time in Patent Office: Days
• US Class Current: 600/476
• 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 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• 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 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7278 Artificial waveform generation or derivation, e.g. synthesising signals from measured signals A61B5/327 takes precedence
• CPC Class Codes: A61B 5/743 Displaying an image simultaneously with additional graphical information, e.g. symbols, charts, function plots

Abstract

A patient monitoring system may determine portions of a PPG signal that correspond to artifacts, to a baseline shift that exceeds a threshold, or to a pulse-to-pulse variability that exceeds a threshold. The patient monitoring system may identify a contiguous portion of the PPG signal that does not include the determined portions. The contiguous portion of the PPG signal may be used to determine physiological information.

Claims

1. A method for determining physiological information from a photoplethysmograph (PPG) signal, the method comprising:

determining, using processing equipment, the presence of an artifact in a first portion of the PPG signal;

determining, using the processing equipment, the presence of a baseline shift that exceeds a baseline shift threshold in a second portion of the PPG signal;

determining, using the processing equipment, a pulse-to-pulse variability that exceeds a variability threshold in a third portion of the PPG signal; and

identifying, using the processing equipment, a contiguous portion of the PPG signal that does not include the first portion, the second portion, and the third portion, wherein the contiguous portion is at least a minimum length; and

determining, using the processing equipment, the physiological information based on the contiguous portion.

2. The method of claim 1, further comprising discarding portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

3. The method of claim 1, further comprising replacing portions of the PPG signal that correspond to the first portion, the second portion, and the third portion with a respective substitute signal.

4. The method of claim 3, wherein replacing portions of the PPG signal comprises substituting an attenuated signal for portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

5. The method of claim 3, wherein replacing portions of the PPG signal comprises substituting cyclical padding for portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

6. The method of claim 1, wherein determining the presence of a baseline shift comprises:

identifying one or more locations in the PPG signal wherein a PPG baseline signal exceeds the baseline shift threshold; and

identifying the second portion based on the one or more locations and based on a buffer region between the one or more locations.

7. The method of claim 1, wherein determining the pulse-to-pulse variability comprises:

determining a mean pulse period associated with the PPG signal; and

determining the pulse-to-pulse variability based on the mean pulse period.

8. A non-transitory computer-readable storage medium for use in determining physiological information from a photoplethysmograph (PPG) signal, the computer-readable medium having computer program instructions recorded thereon for:

determining the presence of an artifact in a first portion of the PPG signal;

determining the presence of a baseline shift that exceeds a baseline shift threshold in a second portion of the PPG signal;

determining a pulse-to-pulse variability that exceeds a variability threshold in a third portion of the PPG signal; and

identifying a contiguous portion of the PPG signal that does not include the first portion, the second portion, and the third portion, wherein the contiguous portion is at least a minimum length; and

determining the physiological information based on the contiguous portion.

9. The computer-readable medium of claim 8, the computer-readable medium having computer program instructions recorded thereon for discarding portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

10. The computer-readable medium of claim 8, the computer-readable medium having computer program instructions recorded thereon for replacing portions of the PPG signal that correspond to the first portion, the second portion, and the third portion with a respective substitute signal.

11. The computer-readable medium of claim 10, wherein replacing portions of the PPG signal comprises substituting an attenuated signal for portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

12. The computer-readable medium of claim 8, wherein determining the presence of a baseline shift comprises:

identifying one or more locations in the PPG signal wherein a PPG baseline signal exceeds the baseline shift threshold; and

identifying the second portion based on the one or more locations and based on a buffer region between the one or more locations.

13. The computer-readable medium of claim 8, wherein determining the pulse-to-pulse variability comprises:

determining a mean pulse period associated with the PPG signal; and

determining the pulse-to-pulse variability based on the mean pulse period.

14. A patient monitoring system comprising processing equipment configured to:

determine the presence of an artifact in a first portion of the PPG signal;

determine the presence of a baseline shift that exceeds a baseline shift threshold in a second portion of the PPG signal;

determine a pulse-to-pulse variability that exceeds a variability threshold in a third portion of the PPG signal; and

identify a contiguous portion of the PPG signal that does not include the first portion, the second portion, and the third portion, wherein the contiguous portion is at least a minimum length; and

determine the physiological information based on the contiguous portion.

15. The patient monitoring system of claim 14, wherein the processing equipment is further configured to discard portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

16. The patient monitoring system of claim 14, wherein the processing equipment is further configured to replace portions of the PPG signal that correspond to the first portion, the second portion, and the third portion with a respective substitute signal.

17. The patient monitoring system of claim 16, wherein the processing equipment is further configured to substitute an attenuated signal for portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

18. The patient monitoring system of claim 16, wherein the processing equipment is further configured to substitute cyclical padding for portions of the PPG signal that correspond to the first portion, the second portion, and the third portion.

19. The patient monitoring system of claim 14, wherein the processing equipment is further configured to:

identify one or more locations in the PPG signal wherein a PPG baseline signal exceeds the baseline shift threshold; and

identify the second portion based on the one or more locations and based on a buffer region between the one or more locations.

20. The patient monitoring system of claim 14, wherein the processing equipment is further configured to:

determine a mean pulse period associated with the PPG signal; and

determine the pulse-to-pulse variability based on the mean pulse period.