Consistent signal selection by signal segment selection techniques

• US 9,392,975 B2
• Filed: 09/06/2013
• Issued: 07/19/2016
• Est. Priority Date: 06/30/2008
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: McGonigle, Scott, Addison, Paul S., Watson, James N.
• Primary Examiner(s): ZEMAN, MARY K
• Application Number:
  US14/020,547
• Publication Number:
  US 20140012109A1
• Time in Patent Office: 1,047 Days
• US Class Current: 1/1
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• 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 5/7207 of noise induced by motion artifacts
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/726 using Wavelet transforms
• CPC Class Codes: G06F 2218/10 by analysing the shape of a waveform, e.g. extracting parameters relating to peaks

Abstract

According to embodiments, techniques for selecting a consistent part of a signal, including a photoplethysmograph (PPG) signal, are disclosed. A pulse oximetry system including a sensor or probe may be used to obtain a PPG signal from a subject. Signal peaks may be identified in the PPG signal. Characteristics of the signal peaks, including the amplitude levels of the signal peaks and/or the time-distance between the signal peaks may be used to determine if the PPG signal is consistent. In an embodiment, signal peaks are processed based on a consistency metric, and the processed signal peaks are compared to the consistency metric to determine if the PPG signal is consistent. If the PPG signal is determined to be consistent, the PPG signal may be further analyzed to determine an underlying signal parameter, including, for example, a patient respiration rate. If the PPG signal is determined to be inconsistent, the inconsistent portion of the signal may be removed from the overall signal or otherwise transformed.

Claims

1. A method for processing a physiological signal, comprising:

obtaining a photoplethysmograph (PPG) signal from a pulse oximetry sensor;

selecting, using a pulse oximeter, a current portion of the PPG signal for analysis;

identifying, using the pulse oximeter, a plurality of signal peaks in the current portion of the PPG signal;

determining, using the pulse oximeter, a peak characteristic for each of the plurality of signal peaks, wherein the peak characteristic comprises one or more of peak amplitude, trough amplitude, and interpeak distance;

comparing, using the pulse oximeter, the peak characteristic for each of the plurality of signal peaks to each other to determine if the current portion of the PPG signal is consistent; and

responsive to determining that the current portion of the PPG signal comprising a plurality of peaks is consistent, determining, using the pulse oximeter, respiration rate based at least in part on the current portion of the PPG signal.

2. The method of claim 1, wherein the peak characteristic comprises peak amplitude and wherein comparing the peak characteristic for each of the plurality of signal peaks comprises:

selecting a first signal peak from the plurality of signal peaks; and

setting a lower threshold at an amplitude level smaller than the determined peak amplitude associated with the first signal peak, and setting an upper threshold at an amplitude level larger than the determined peak amplitude associated with the first signal peak.

3. The method of claim 2, wherein comparing the peak characteristic for each of the plurality of signal peaks further comprises:

selecting a second signal peak from the plurality of signal peaks;

determining if the determined peak amplitude associated with the second signal peak is generally greater than the lower threshold; and

determining if the determined peak amplitude associated with the second signal peak is generally lower than the upper threshold.

4. The method of claim 1, wherein the peak characteristic comprises interpeak distance.

5. The method of claim 4, wherein comparing the peak characteristic for each of the plurality of signal peaks comprises:

determining if a first interpeak distance exceeds a threshold value; and

if the first interpeak distance exceeds the threshold value, determining if the first interpeak distance exceeds one or more past or future interpeak distances.

6. The method of claim 1, wherein if a current portion of the PPG is determined not to be consistent, the current portion of the PPG signal is removed from a processed version of the PPG signal.

7. The method of claim 1, wherein obtaining the PPG signal from the pulse oximetry sensor further comprises processing the PPG signal to remove artifacts present in the PPG signal.

8. The method of claim 1, wherein the plurality of signal peaks are identified using an extrema-finding process.

9. A system for processing a physiological signal, the system comprising:

a pulse oximeter configured for;

obtaining a photoplethysmograph (PPG) signal from a pulse oximetry sensor;

selecting a current portion of the PPG signal for analysis;

identifying a plurality of signal peaks in the current portion of the PPG signal;

determining a peak characteristic for each of the plurality of signal peaks, wherein the peak characteristic comprises one or more of peak amplitude, trough amplitude, and interpeak distance

comparing the peak characteristic for each of the plurality of signal peaks to each other to determine if the current portion of the PPG signal is consistent; and

responsive to determining that the current portion of the PPG signal comprising a plurality of peaks is consistent, determining respiration rate based at least in part on the current portion of the PPG signal.

10. The system of claim 9, wherein the peak characteristic comprises peak amplitude and wherein the pulse oximeter is further configured for comparing the peak characteristic for each of the plurality of signal peaks at least in part by:

selecting a first signal peak from the plurality of signal peaks; and

setting a lower threshold at an amplitude level smaller than the determined peak amplitude associated with the first signal peak, and setting an upper threshold at an amplitude level larger than the determined peak amplitude associated with the first signal peak.

11. The system of claim 10, wherein the pulse oximeter is further configured for comparing the peak characteristic for each of the plurality of signal peaks at least in part by:

selecting a second signal peak from the plurality of signal peaks;

determining if the determined peak amplitude associated with the second signal peak is generally greater than the lower threshold; and

determining if the determined peak amplitude associated with the second signal peak is generally lower than the upper threshold.

12. The system of claim 9, wherein the peak characteristic comprises interpeak distance.

13. The system of claim 12, wherein the pulse oximeter is further configured for comparing the peak characteristic for each of the plurality of signal peaks at least in part by:

determining if a first interpeak distance exceeds a threshold value; and

if the first interpeak distance exceeds the threshold value, determining if the first interpeak distance exceeds one or more past or future interpeak distances.

14. The system of claim 9, wherein if a current portion of the PPG is determined not to be consistent, the current portion of the PPG signal is removed from a processed version of the PPG signal.

15. The system of claim 9, wherein obtaining the PPG signal from the pulse oximetry sensor further comprises processing the PPG signal to remove artifacts present in the PPG signal.

16. The system of claim 9, wherein the plurality of signal peaks are identified using an extrema-finding process.

17. A non-transitory computer readable medium comprising:

computer program instructions stored therein for causing a pulse oximeter to;

obtain a photoplethysmograph (PPG) signal from a pulse oximetry sensor;

select a current portion of the PPG signal for analysis;

identify a plurality of signal peaks in the current portion of the PPG signal;

determine a peak characteristic for each of the plurality of signal peaks, wherein the peak characteristic comprises one or more of peak amplitude, trough amplitude, and interpeak distance

compare the peak characteristic for each of the plurality of signal peaks to each other to determine if the current portion of the PPG signal is consistent; and

responsive to determining that the current portion of the PPG signal comprising a plurality of peaks is consistent determining respiration rate based at least in part on the current portion of the PPG signal.

18. The computer readable medium of claim 17, wherein the peak characteristic comprises peak amplitude and wherein the computer program instructions cause the pulse oximeter to compare the peak characteristic for each of the plurality of signal peaks by:

selecting a first signal peak from the plurality of signal peaks; and

setting a lower threshold at an amplitude level smaller than the identified amplitude level associated with the first signal peak, and setting an upper threshold at an amplitude level larger than the identified amplitude level associated with the first signal peak.