SYSTEMS AND METHODS FOR DETERMINING RESPIRATION INFORMATION FROM SEGMENTS OF A PHOTOPLETHYSMOGRAPH

• US 20140275889A1
• Filed: 03/15/2013
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Abandoned Application

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Covidien LP (Medtronic Plc)
• Inventors: Addison, Paul Stanley, Watson, James
• Application Number:
  US13/841,387
• Publication Number:
  US 20140275889A1
• Time in Patent Office: Days
• US Class Current: 600/324
• CPC Class Codes: A61B 2560/0223 of calibration, e.g. protocols for calibrating sensors
• CPC Class Codes: A61B 2562/08 Sensors provided with means for identification, e.g. barcodes or memory chips
• CPC Class Codes: A61B 2562/085 combined with means for recording calibration data
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• 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 5/7207 of noise induced by motion artifacts

Abstract

A physiological monitoring system may determine respiration information from a PPG signal. The system may analyze the PPG signal with respect to itself by associating values of the PPG signal with values of a time-delayed version of the PPG signal to create pairs of associated values. A subset of associated values may be identified. Respiration metric values may be determined based on the subset of pairs. The respiration metric values may be amplitude values and/or time values corresponding to the subset of pairs. The respiration metric values may be analyzed using autocorrelation, cross-correlation, or other signal processing techniques to determine respiration information such as respiration rate.

Claims

1. A method for determining respiration information, the method comprising:

receiving a photoplethysmograph (PPG) signal;

associating values of the PPG signal with time delayed values of the PPG signal to generate pairs of associated values;

analyzing the pairs of associated values to identify a subset of the pairs; and

determining respiration information based at least in part on the subset of the pairs.

2. The method of claim 1, wherein the PPG signal is approximately centered about zero.

3. The method of claim 1, further comprising:

receiving heart rate information; and

selecting a time delay of the time delayed values of the PPG signal to be approximately one quarter of a period associated with the heart rate information.

4. The method of claim 1, wherein analyzing the pairs of associated values to identify a subset of the pairs comprises identifying pairs of associated values that approximately form a straight line when the pairs are considered in two-dimensional space.

5. The method of claim 1, wherein analyzing the pairs of associated values to identify a subset of the pairs comprises:

determining angles corresponding to the pairs of associated values; and

identifying pairs of associated values whose angles correspond to a predetermined angle.

6. The method of claim 1, wherein analyzing the pairs of associated values to identify a subset of pairs comprises identifying zero crossings associated with the pairs of associated values.

7. The method of claim 1, wherein determining respiration information comprises determining one or more respiration metric values based on the subset of the pairs.

8. The method of claim 7, wherein the one or more respiration metric values are one or more of amplitude values and time values corresponding to the subset of pairs.

9. The method of claim 7, wherein determining respiration information comprises performing a correlation based on the respiration metric values.

10. The method of claim 1, wherein determining the respiration information comprises determining respiration rate.

11. A physiological monitoring system, the system comprising:

processing equipment configured to;

receive a photoplethysmograph (PPG) signal;

associate values of the PPG signal with time delayed values of the PPG signal to generate pairs of associated values;

analyze the pairs of associated values to identify a subset of the pairs; and

determine respiration information based at least in part on the subset of the pairs.

12. The system of claim 11, wherein the processing equipment is further configured to approximately center the PPG signal about zero.

13. The system of claim 11, wherein the processing equipment is further configured to:

receive heart rate information; and

select a time delay of the time delayed values of the PPG signal to be approximately one quarter of a period associated with the heart rate information.

14. The system of claim 11, wherein the processing equipment is configured to identify the subset of pairs by identifying pairs of associated values that approximately form a straight line when the pairs are considered in two-dimensional space.

15. The system of claim 11, wherein the processing equipment is configured to identify the subset of pairs by:

determining angles corresponding to the pairs of associated values; and

identifying pairs of associated values whose angles correspond to a predetermined angle.

16. The system of claim 11, wherein the processing equipment is configured to identify the subset of pairs by identifying zero crossings associated with the pairs of associated values.

17. The system of claim 11, wherein the processing equipment is configured to determine the respiration information by determining one or more respiration metric values based on the subset of pairs.

18. The system of claim 17, wherein the one or more respiration metric values are one or more of amplitude values and time values corresponding to the subset of pairs.

19. The system of claim 17, wherein the processing equipment is configured to determine respiration information by performing a correlation based on the respiration metric values.

20. The system of claim 11, wherein the respiration information comprises respiration rate.