Selection of preset filter parameters based on signal quality

• US 20040138538A1
• Filed: 01/13/2003
• Published: 07/15/2004
• Est. Priority Date: 01/13/2003
• Status: Active Grant

• Current Assignee: Covidien LP (Medtronic Plc)
• Original Assignee: Nellcor Puritan Bennett Incorporated (Medtronic Plc)
• Inventors: Stetson, Paul F.
• Granted Patent: US 7,016,715 B2
• Time in Patent Office: Days
• US Class Current: 600/310
• CPC Class Codes: A61B 5/01 Measuring temperature of body parts ; Diagnostic temperature sensing, e.g. for malignant or inflamed tissue clinical contact thermometers G01K13/20
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 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 5/14551 for measuring blood gases
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7221 Determining signal validity, reliability or quality A61B5/7207 and A61B5/7217 take precedence
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/725 using specific filters therefor, e.g. Kalman or adaptive filters A61B5/316 take precedence
• CPC Class Codes: G06F 2218/02 Preprocessing

Abstract

Methods and devices for reducing noise effects in a system for measuring a physiological parameter, including receiving an input signal; obtaining an assessment of the signal quality of the input signal; selecting coefficients for a digital filter using the assessment of signal quality; and filtering the input signal using the digital filter, without comparing the filter'"'"'s output signal with the input signal.

Claims

1. A method of reducing noise effects in a system for measuring a physiological parameter, comprising:

receiving an input signal;

obtaining an assessment of the signal quality of said input signal;

selecting coefficients for a digital filter using said assessment of signal quality; and

filtering said input signal using said digital filter, without comparing said filter'"'"'s output signal with said input signal.

2. The method of claim 1 wherein said selecting comprises selecting coefficients from a plurality of discrete preset values.

3. The method of claim 1 wherein said selecting comprises selecting coefficients from a plurality of constant and preset values.

4. The method of claim 1 wherein said filtering comprises operating a digital filter having a linear input-output relationship.

5. The method of claim 1 wherein said filtering comprises operating a digital filter having a non-linear input-output relationship.

6. The method of claim 1 wherein said obtaining an assessment of said signal quality comprises obtaining a measure of the skew of the time-derivative of the input signal.

7. The method of claim 1 wherein said receiving comprises receiving input signals form more than one wavelength, and said obtaining an assessment of said signal quality comprises obtaining a measure of the correlation between the signals from different wavelengths.

8. The method of claim 1 wherein said obtaining an assessment of said signal quality comprises obtaining a measure of the variation in the amplitude of the input signal.

9. The method of claim 1 wherein said obtaining an assessment of said signal quality comprises obtaining a measure of the maximum value of the input signal.

10. The method of claim 1 wherein said obtaining an assessment of said signal quality comprises obtaining a measure of the spectral peak frequency or frequencies of the input signal.

11. The method of claim 1 wherein said selecting is performed in real time, with said coefficients of said digital filter being determined using a current input sample.

12. The method of claim 1 wherein said selecting is performed using a previously stored input signal sample.

13. The method of claim 1 wherein said receiving comprises receiving a signal from an oximeter, wherein said signal is a function of an oxygen saturation.

14. The method of claim 1 wherein said receiving comprises receiving a signal from an oximeter, wherein said signal is a function of a pulse rate.

15. The method of claim 1 wherein said receiving said input signals comprises receiving signals corresponding to sensed optical energies from a plurality of wavelengths.

16. An apparatus for reducing noise effects in a system for measuring a physiological parameter, comprising:

means for receiving an input signal;

means for obtaining an assessment of the signal quality of the input signal;

means for selecting coefficients for a digital filter using said assessment of signal quality; and

means for filtering said input signal using said digital filter, without comparing said filter'"'"'s output signal with said input signal.

17. The apparatus of claim 16 wherein said means for selecting are configured to select said coefficients from a plurality of discrete preset values.

18. The apparatus of claim 16 wherein said means for selecting are configured to select said coefficients from a plurality of constant and preset values.

19. The apparatus of claim 16 wherein said means for filtering comprise a digital filter having a linear input-output relationship.

20. The apparatus of claim 16 wherein said means for filtering comprise a digital filter having a non-linear input-output relationship.

21. The apparatus of claim 16 wherein said means for obtaining an assessment of said signal quality are configured to obtain a measure of the skew of the time-derivative of said input signal.

22. The apparatus of claim 16 wherein said means for receiving are configured to receive input signals form more than one wavelength, and said means for obtaining an assessment of said signal quality obtain a measure of the correlation between said signals from different wavelengths.

23. The apparatus of claim 16 wherein said means for obtaining an assessment of said signal quality are configured to obtain a measure of the variation in the amplitude of said input signal.

24. The apparatus of claim 16 wherein said means for obtaining an assessment of said signal quality are configured to obtain a measure of the maximum value of said input signal.

25. The apparatus of claim 16 wherein said means for obtaining an assessment of said signal quality are configured to obtain a measure of the spectral peak frequency or frequencies of said input signal.

26. The apparatus of claim 16 wherein said means for selecting are configured to select said coefficients in real time, with said coefficients for said digital filter being determined using a current input sample.

27. The apparatus of claim 16 wherein said means for selecting are configured to select said coefficients using a previously stored input signal sample.

28. The apparatus of claim 16 wherein said means for receiving are configured to receive a signal from an oximeter, wherein said signal is a function of an oxygen saturation.

29. The apparatus of claim 16 wherein said means for receiving are configured to receive a signal from an oximeter, wherein said signal is a function of a pulse rate.

30. The apparatus of claim 16 wherein said means for receiving are configured to receive signals corresponding to sensed optical energies from a plurality of wavelengths.