System for prefiltering a plethysmographic signal

• US 20060293575A1
• Filed: 10/14/2005
• Published: 12/28/2006
• Est. Priority Date: 06/28/2005
• Status: Active Grant

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Norris, Mark A.
• Granted Patent: US 7,403,806 B2
• Time in Patent Office: Days
• US Class Current: 600/336
• CPC Class Codes: A61B 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/7207 of noise induced by motion artifacts

Abstract

A detector signal in a pulse oximeter is prefiltered, prior to processing so as to determine a physiological parameter value, so as to reduce the effects of artifact in the signal. An exemplary prefilter multiplies signal amplitude values by a quantitude that is inversely proportional to a substantially current amplitude so as to reduce the amplitude of large amplitude sections typically associated with artifact. In one implementation, the quantity is a ratio of an amplitude associated with a clean section of the signal by some exponential factor of a substantially current amplitude. In this manner, artifact affected portions of the signal are deemphasized in subsequent analyses.

Claims

1. A method for use in pulse oximetry, comprising the steps of:

receiving an electronic signal reflective of one or more optical signals incident on a detector of a pulse oximeter, wherein said electronic signal includes a first temporal portion that is potentially corrupted by artifact;

processing said signal such that an amplitude associated with said first temporal portion of said signal is reduced in relation to a second temporal portion of said signal, thereby providing a processed signal; and

using said processed signal to obtain physiological information regarding a patient.

2. A method as set forth in claim 1, wherein said step of processing comprises substantially continuously prefiltering said signal so as to reduce any large amplitude portions thereof.

3. A method as set forth in claim 1, wherein said step of processing comprises monitoring said signal to identify said first temporal portion and selectively reducing said amplitude responsive to said step of identifying.

4. A method as set forth in claim 1, wherein said step of processing comprises processing to achieve the effect of multiplying an amplitude value of said signal corresponding to a time within said first temporal portion by a value less than 1.0.

5. A method as set forth in claim 1, wherein said step of processing comprises processing to achieve the effect of multiplying an amplitude value of said signal corresponding to a time within said first temporal time portion by a variable quantity that is inversely proportional to said amplitude.

6. A method as set forth in claim 5, wherein said variable quantity is inversely proportional to a multiple or exponential factor of said amplitude.

7. A method as set forth in claim 1, wherein said step of processing at least said first temporal portion of said signal using a first quantity associated with an amplitude of said first portion of said signal and a second quantity associated with said second portion of said signal.

8. A method as set forth in claim 1, wherein said step of using comprises transforming said processed signal into the frequency domain to obtain spectral information and using such spectral information to obtain said physiological information.

9. A method as set forth in claim 8, wherein said physiological information comprises one of a pulserate and an arterial oxygen saturation value for said patient.

10. A method for use in pulse oximetry, comprising the steps of:

receiving an electronic signal reflective of one or more optical signals incident on a detector of a pulse oximeter;

identifying, based on an amplitude related analysis of the received signal, an artifact affected portion of said signal; and

applying a correction to reduce an effect of said artifact.

11. A method as set forth in claim 10, wherein said step of identifying comprises repeatedly measuring an amplitude of said received signal to identify a larger amplitude or portion thereof.

12. A method as set forth in claim 10, wherein said step of applying a correction comprises selectively executing an algorithm with respect to data corresponding to said artifact affected portion of said signal.

13. A method as set forth in claim 10, wherein said step of applying a correction comprises prefiltering said received signal to reduce an amplitude of said artifact affected portion of said signal in relation to another portion of said signal.

14. A method for use in pulse oximetry, comprising the steps of:

receiving a time-based signal reflective of one or more optical signals incident on a detector of a pulse oximeter;

performing a correction with respect to a portion of said received time-based signal to reduce an effect of artifact, thereby providing a processed time-based signal;

performing a transform on said processed time-based signal to obtain transformed information relative to a second domain; and

processing the transformed information to obtain physiological information regarding a patient.

15. A method as set forth in claim 14, wherein said step of performing a correction comprises prefiltering said received time based signal to reduce an amplitude of an artifact affected portion of said signal in relation to another portion of said signal.

16. A method as set forth in claim 14, wherein said step of processing comprises performing a spectral analysis to determine one of a pulserate and an arterial oxygen saturation value for said patient.

17. An apparatus for use in pulse oximetry, comprising:

a port for receiving an electronic signal reflective of one or more optical signals incident on a detector of a pulse oximeter;

a prefilter for filtering said signal such that an amplitude associated with an artifact affected portion of said signal is reduced in relation to a second portion of said signal, thereby providing a process signal; and

a processor for processing said processed signal to obtain physiological information regarding a patient.

18. An apparatus as set forth in claim 17, wherein said port comprises input structure associated with the digital signal processing unit.

19. An apparatus as set forth in claim 17, wherein said prefilter is operative for substantially continuously prefiltering said signal source to reduce any large amplitude portions thereof.

20. An apparatus as set forth in claim 17, wherein said prefilter is operative for monitoring said signal to identify said artifact affected portion and selectively reducing said amplitude responsive to said identifying.

21. An apparatus as set forth in claim 17, wherein said processor is operative for calculating one of a pulse rate and an arterial saturation value for said patient.