Methods and systems for determining noise information from a physiological signal

• US 9,259,186 B2
• Filed: 09/11/2012
• Issued: 02/16/2016
• Est. Priority Date: 09/11/2012
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Rodriguez-Llorente, Fernando, Engelbrecht, Pirow, Wooder, Nicholas James
• Primary Examiner(s): ZEMAN, MARY K
• Application Number:
  US13/609,341
• Publication Number:
  US 20140073861A1
• Time in Patent Office: 1,253 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 5/0806 by whole-body plethysmography measuring blood flow using plethysmography A61B5/0295; impedance plethysmography A61B5/053; measuring volume of the body or parts thereof A61B5/1073
• 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 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61B 5/7228 Signal modulation applied to the input signal sent to patient or subject; demodulation to recover the physiological signal modulation H03C
• CPC Class Codes: A61B 5/7246 using correlation, e.g. template matching or determination of similarity
• CPC Class Codes: A61B 5/7264 Classification of physiological signals or data, e.g. using neural networks, statistical classifiers, expert systems or fuzzy systems neural networks per se G06N3/00; expert systems per se G06N5/00
• CPC Class Codes: A61B 5/7275 Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor
• CPC Class Codes: G16H 40/63 for local operation

Abstract

A physiological monitoring system may determine physiological information, such as physiological rate information, and other information, such as noise information, from a physiological signal. The system may generate a first difference signal based on a first segment of the physiological signal and sort the first difference signal to generate a first sorted difference signal. The system may generate a second difference signal based on a second segment of the physiological signal and sort the second difference signal to generate a second sorted difference signal. The first and second sorted difference signals may be analyzed and a value indicative of noise may be determined based on the analysis.

Claims

1. A pulse oximetry monitoring system for determining pulse rate of a subject, comprising:

a pulse oximetry sensor configured to detect light attenuated by the subject and generate a photoplethysmographic (PPG) signal based on the detected attenuated light; and

a pulse oximeter coupled to the pulse oximetry sensor, wherein the pulse oximeter is configured to;

store a rate algorithm;

generate a first difference signal based on a first segment of the PPG signal;

sort the first difference signal to generate a first sorted difference signal;

generate a second difference signal based on a second segment of the PPG signal;

sort the second difference signal to generate a second sorted difference signal;

analyze the first sorted difference signal and the second sorted difference signal;

determine a value indicative of noise based on the analysis of the first sorted difference signal and the second sorted difference signal;

determine an algorithm setting based on the value indicative of noise;

apply the algorithm setting to the rate algorithm stored by the pulse oximeter to thereby update the rate algorithm; and

determine the pulse rate of the subject using the updated rate algorithm and the PPG signal.

2. The system of claim 1, wherein the pulse oximeter is further configured to:

determine a first line fit having a first slope for the first sorted difference signal;

determine a second line fit having a second slope for the second sorted difference signal; and

determine a difference between the first slope and the second slope.

3. The system of claim 1, wherein the pulse oximeter is further configured to:

determine a first line fit for the first sorted difference signal;

determine a second line fit for the second sorted difference signal;

determine a goodness of fit associated with the first line fit; and

determine a goodness of fit associated with the second line fit.

4. The system of claim 1, wherein the pulse oximeter is further configured to determine a goodness of fit between the first sorted difference signal and the second sorted difference signal.

5. The system of claim 1, wherein the pulse oximeter is further configured to determine a value indicative of differences between the first sorted difference signal and the second sorted difference signal.

6. A pulse oximetry processing module for determining pulse rate of a subject, wherein the pulse oximetry processing module comprises a non-transitory computer readable medium having instructions stored thereon, wherein the instructions comprise a rate algorithm, and wherein the instructions are configured to instruct the pulse oximetry processing module to:

receive a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor output, wherein the pulse oximetry sensor detects light attenuated by the subject and generates the PPG signal based on the detected attenuated light;

generate a first difference signal based on a first segment of the PPG signal;

sort the first difference signal to generate a first sorted difference signal;

generate a second difference signal based on a second segment of the PPG signal;

sort the second difference signal to generate a second sorted difference signal;

analyze the first sorted difference signal and the second sorted difference signal;

determine a value indicative of noise based on the analysis of the first sorted difference signal and the second sorted difference signal;

determine an algorithm setting based on the value indicative of noise;

apply the algorithm setting to the stored rate algorithm to thereby update the rate algorithm; and

determine the pulse rate of the subject using the updated rate algorithm and the PPG signal.

7. The pulse oximetry processing module of claim 6, wherein the instructions are further configured to instruct the pulse oximetry processing module to:

determine a first line fit having a first slope for the first sorted difference signal;

determine a second line fit having a second slope for the second sorted difference signal; and

determine a difference between the first slope and the second slope.

8. The pulse oximetry processing module of claim 6, wherein the instructions are further configured to instruct the pulse oximetry processing module to:

determine a first line fit for the first sorted difference signal;

determine a second line fit for the second sorted difference signal;

determine a goodness of fit associated with the first line fit; and

determine a goodness of fit associated with the second line fit.

9. The pulse oximetry processing module of claim 6, wherein the instructions are further configured to instruct the pulse oximetry processing module to determine a goodness of fit between the first sorted difference signal and the second sorted difference signal.

10. The pulse oximetry processing module of claim 6, wherein the instructions are further configured to instruct the pulse oximetry processing module to determine a value indicative of differences between the first sorted difference signal and the second sorted difference signal.

11. A method for determining pulse rate of a subject, comprising:

storing, using a pulse oximeter, a rate algorithm;

receiving, using the pulse oximeter, a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor output, wherein the pulse oximetry sensor detects light attenuated by the subject and generates the PPG signal based on the detected attenuated light;

generating, using the pulse oximeter, a first difference signal based on a first segment of the PPG signal;

sorting, using the pulse oximeter, the first difference signal to generate a first sorted difference signal;

generating, using the pulse oximeter, a second difference signal based on a second segment of the PPG signal;

sorting, using the pulse oximeter, the second difference signal to generate a second sorted difference signal;

analyzing, using the pulse oximeter, the first sorted difference signal and the second sorted difference signal;

determining, using the pulse oximeter, a value indicative of noise based on the analysis of the first sorted difference signal and the second sorted difference signal;

determining, using the pulse oximeter, an algorithm setting based on the value indicative of noise;

applying, using the pulse oximeter, the algorithm setting to the rate algorithm stored by the pulse oximeter thereby updating the rate algorithm; and

determining, using the pulse oximeter, the pulse rate of the subject using the updated rate algorithm and the PPG signal.

12. The method of claim 11, wherein analyzing the first sorted difference signal and the second sorted difference signal comprises:

determining a first line fit having a first slope for the first sorted difference signal;

determining a second line fit having a second slope for the second sorted difference signal; and

determining a difference between the first slope and the second slope.

13. The method of claim 11, wherein analyzing the first sorted difference signal and the second sorted difference signal comprises:

determining a first line fit for the first sorted difference signal;

determining a second line fit for the second sorted difference signal;

determining a goodness of fit associated with the first line fit; and

determining a goodness of fit associated with the second line fit.

14. The method of claim 11, wherein analyzing the first sorted difference signal and the second sorted difference signal comprises determining a goodness of fit between the first sorted difference signal and the second sorted difference signal.

15. The method of claim 11, wherein analyzing the first sorted difference signal and the second sorted difference signal comprises determining a value indicative of differences between the first sorted difference signal and the second sorted difference signal.

16. A non-transitory computer-readable medium for use in determining the pulse rate of a subject, the computer-readable medium comprising:

computer program instructions recorded thereon for causing a pulse oximeter storing a rate algorithm to;

receive a photoplethysmographic (PPG) signal derived from a pulse oximetry sensor output, wherein the pulse oximetry sensor detects light attenuated by the subject and generates the PPG signal based on the detected attenuated light;

generate a first difference signal based on a first segment of the PPG signal;

sort the first difference signal to generate a first sorted difference signal;

generate a second difference signal based on a second segment of the PPG signal;

sort the second difference signal to generate a second sorted difference signal;

analyzing the first sorted difference signal and the second sorted difference signal;

determine a value indicative of noise based on the analysis of the first sorted difference signal and the second sorted difference signal;

determine an algorithm setting based on the value indicative of noise;

apply the algorithm setting to the stored rate algorithm to thereby update the rate algorithm; and

determine the pulse rate of the subject using the updated rate algorithm and the PPG signal.

17. The non-transitory computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to:

determine a first line fit having a first slope for the first sorted difference signal;

determine a second line fit having a second slope for the second sorted difference signal; and

determine a difference between the first slope and the second slope.

18. The computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to:

determine a first line fit for the first sorted difference signal;

determine a second line fit for the second sorted difference signal;

determine a goodness of fit associated with the first line fit; and

determine a goodness of fit associated with the second line fit.

19. The computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to determine a goodness of fit between the first sorted difference signal and the second sorted difference signal.

20. The computer-readable medium of claim 16, comprising further computer program instructions recorded thereon for causing the pulse oximeter to determine a value indicative of differences between the first sorted difference signal and the second sorted difference signal.