Processing of Photoplethysmography Signals

• US 20090043179A1
• Filed: 08/08/2007
• Published: 02/12/2009
• Est. Priority Date: 08/08/2007
• Status: Active Grant

• Current Assignee: Convergent Engineering, Inc., University of Florida Research Foundation, Incorporated (State University System of Florida)
• Original Assignee: University of Florida Research Foundation, Incorporated (State University System of Florida)
• Inventors: Stahl, Michael W. JR., Melker, Richard J., Euliano, Neil R.
• Granted Patent: US 8,529,459 B2
• Time in Patent Office: Days
• US Class Current: 600/323
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence

Abstract

Disclosed herein are methods and devices of processing photoplethysmography signal information. The methods for processing will allow numerous medical observations and diagnoses from a simple, non-invasive probe.

Claims

1. A method of isolating an AC and DC component from a stream of plethysmography signals comprising identifying the peaks and troughs of said plethysmography signals;

identifying the midpoints or minimum values between said peaks and troughs, wherein the interpolated line connecting said midpoints or minimum values represents said DC component;

extracting said DC component from said plethysmography signals, thereby separately obtaining said AC component, whereby an AC component and DC component are individually isolated.

2. The method of claim 1 wherein said stream of plethysmography signals is obtained from an individual by positioning at least one photodetector on exterior of said individual'"'"'s right or left nares;

and positioning at least one LED in the individual'"'"'s right or left nostril just across from said at least one photodetector.

3. The method of claim 2, wherein said at least one photodetector is positioned on top of said individual'"'"'s fibro-areolar region of said individual'"'"'s nose.

4. A system for processing plethysmography signals from a patient comprising

at least one pulse oximeter probe configured for securing to a central source site of said patient and effective to generate a plethysmography signal stream;

and

a computer communicatingly connected to said at least one pulse oximeter probe, said computer comprising at least one processing module, a first computer-readable program code module for causing said computer to process signals of said at least one pulse oximeter probe to obtain an AC component signal or a DC component signal, or both, and a second computer-readable program code module for causing said computer to analyze said AC component signal or DC component signal, or both to determine a decrease in amplitude of either AC component signal or DC component signal, or both.

5. The system of claim 4, wherein said computer further comprises a display screen.

6. A computer program product for use with a computer comprising at least one processing module, said product comprising:

a computer-usable medium comprising computer readable program code modules embodied in said computer-usable medium;

computer readable first program code module for causing said computer to process plethysmography signals obtained from a pulse oximeter probe by separating out an AC component signal stream and a DC component signal stream; and

computer-readable second program code module for causing said computer to analyze said AC signal stream or said DC signal stream, or both, to determine a decrease in amplitude of either AC component signal or DC component signal, or both.

7. A method of obtaining processed photoplethysmography readings from an individual, said method comprising:

obtaining a pulse oximeter probe comprising at least one LED and at least one photodetector;

securing said probe onto said individual'"'"'s right and/or left nasal alar, whereby tissue of said nasal alar rests between said at least one photodetector and said at least one LED; and

monitoring photoplethysmography signals generated by said probe responsive to blood flow at said tissue of said nasal alar; and

isolating an AC and DC component from a stream of plethysmography signals comprising identifying the peaks and troughs of said plethysmography signals;

identifying the midpoints or minimum values between said peaks and troughs, wherein the interpolated line connecting said midpoints or minimum values represents said DC component;

extracting said DC component from said plethysmography signals, thereby separately obtaining said AC component, whereby an AC component and DC component are individually isolated.

8. A method of isolating an AC and DC component from a stream of plethysmography signals comprising identifying the extrema of said plethysmography signals;

identifying a common point relative to the extrema, wherein the interpolated line connecting said common points represents said DC component;

extracting said DC component from said plethysmography signals, thereby separately obtaining said AC component, whereby an AC component and DC component are individually isolated.

9. The method of claim 8, wherein said common point is a midpoint.

10. The method of claim 8, wherein said common point is a maximum point.

11. The method of claim 8, wherein said common point is a minimum point.

12. The method of claim 8, wherein said common point is a dicrotic notch.

13. The method of claim 8, wherein said common point is a zero-crossing point.

14. The method of claim 8, wherein said common point is an inflection point.

15. The method of claim 8, wherein said common point is a point of equal areas.

16. The method of claim 8, wherein said stream of plethysmography signals is obtained from a pulse oximeter secured to a nasal alar of a patient.

17. A method of isolating a high frequency signal content from a low frequency signal content from a stream of plethysmograph signals comprising a high frequency component, a first low frequency component and a second low frequency component said method comprising identifying extrema of said plethysmography signals;

identifying a common point relative to the extrema, wherein the interpolated line connecting said common points represents the low frequency content of the signal;

extracting said low frequency content from said plethysmography signals, thereby separately obtaining the higher frequency content from the low frequency content.

18. The method of claim 17, wherein said high frequency signal content comprises a cardiac component and said first low frequency content comprises a respiratory component and a sympathetic and parasympathetic tone component.

19. The method of claim 17, further comprising separating said first low frequency component from said second low frequency component.