SYSTEMS AND METHODS FOR DETERMINING RESPIRATION INFORMATION FROM A PHOTOPLETHYSMOGRAPH

• US 20130079606A1
• Filed: 09/23/2011
• Published: 03/28/2013
• Est. Priority Date: 09/23/2011
• Status: Active Grant

• Current Assignee: Nellcor Puritan Bennett Ireland
• Original Assignee: Nellcor Puritan Bennett Ireland
• Inventors: McGonigle, Scott, Addison, Paul S., Ochs, James, Watson, James
• Granted Patent: US 9,675,274 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• 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 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A patient monitoring system may receive a photoplethysmograph (PPG) signal including samples of a pulse waveform. The PPG signal may demonstrate morphology changes based on respiration. The system may calculate morphology metrics from the PPG signal, the first derivative of the PPG signal, the second derivative of the PPG signal, or any combination thereof. The morphology metrics may demonstrate amplitude modulation, baseline modulation, and frequency modulation of the PPG signal that is related to respiration. Morphology metric signals generated from the morphology metrics may be used to determine respiration information such as respiration rate.

Claims

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

receiving a photoplethysmograph (PPG) signal;

identifying, using processing equipment, a plurality of fiducial points in the PPG signal;

generating, using the processing equipment, morphology metric signals based at least in part on the PPG signal and based on at least in part on the plurality of fiducial points; and

determining, using the processing equipment, the respiration information based at least in part on the morphology metric signals.

2. The method of claim 1 wherein generating morphology metric signals comprises generating a down metric signal from the PPG signal.

3. The method of claim 1 wherein generating morphology metric signals comprises generating a kurtosis signal from a derivative of the PPG signal.

4. The method of claim 1 wherein generating morphology metric signals comprises generating a delta of second derivative signal from a second derivative of the PPG signal.

5. The method of claim 1 wherein determining respiration information comprises determining respiration rate.

6. The method of claim 1 wherein generating morphology metric signals comprises:

defining a plurality of fiducial-defined portions based on the fiducial points;

calculating a plurality of morphology metric values, wherein each morphology metric value is associated with a fiducial-defined portion; and

generating the morphology metric signals based at least in part on the plurality of morphology metric values.

7. The method of claim 6 wherein determining the morphology metric signals comprises interpolating the morphology metric values.

8. The method of claim 7 wherein determining the morphology metric signals further comprises downsampling the interpolated morphology metric signals.

9. The method of claim 7 wherein determining the morphology metric signals further comprises filtering the interpolated morphology metric signals.

10. The method of claim 6, further comprising attenuating the plurality of morphology metric values.

11. A patient monitoring system comprising:

an interface configured to receive a photoplethysmograph (PPG) signal;

a processor configured to;

identify a plurality of fiducial points in the PPG signal;

generate morphology metric signals based at least in part on the PPG signal and based at least in part on the plurality of fiducial points; and

determine respiration information based at least in part on the morphology metric signals.

12. The patient monitoring system of claim 11, wherein the morphology metric signals comprise a down metric signal.

13. The patient monitoring system of claim 11, wherein the morphology metric signals comprise a kurtosis signal of the derivative of the PPG signal.

14. The patient monitoring system of claim 11, wherein the morphology metric signals comprise a delta of second derivative signal of the second derivative of the PPG signal.

15. The patient monitoring system of claim 11, wherein the respiration information comprises a respiration rate.

16. The patient monitoring system of claim 11, the processor further configured to:

define a plurality of fiducial-defined portions based on the fiducial points;

calculate a plurality of morphology metric values, wherein each morphology metric value is associated with a fiducial-defined portion; and

determine the morphology metric signals based at least in part on the plurality of morphology metric values.

17. The patient monitoring system of claim 16, the processor further configured to interpolate the morphology metric values.

18. The patient monitoring system of claim 17, the processor further configured to downsample the interpolated morphology metric signals.

19. The patient monitoring system of claim 18, the processor further configured to filter the interpolated morphology metric signals.

20. The patient monitoring system of claim 16, the processor further configured to attenuate the plurality of morphology metric values.