Method for reducing baseline drift in a biological signal

• US 20100076329A1
• Filed: 09/25/2008
• Published: 03/25/2010
• Est. Priority Date: 09/25/2008
• Status: Active Grant

• Current Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Original Assignee: Air Products and Chemicals Incorporated (Linde Plc)
• Inventors: Toth, Michael S.
• Granted Patent: US 8,301,230 B2
• Time in Patent Office: Days
• US Class Current: 600/509
• CPC Class Codes: A61B 5/0006 ECG or EEG signals
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval

Abstract

The present invention relates to a computer-based method for reducing or eliminating baseline drift from a biological (bio) signal. The method includes the steps of dividing the bio signal into a plurality of shorter signals having fixed time intervals, fitting a baseline function to a baseline of each of the shorter signals, and subtracting each baseline function from a corresponding shorter signal, resulting in a bio signal with a flat baseline.

Claims

1. A computer-based method for reducing baseline drift in a biological (bio) signal, the method comprising:

dividing the bio signal into a plurality of shorter signals having fixed time intervals;

fitting a baseline function to a baseline of each of the shorter signals; and

subtracting each baseline function from a corresponding shorter signal, thereby flattening the baseline of the bio signal.

2. The method of claim 1, wherein a length of the time intervals corresponds to a frequency value of the baseline drift.

3. The method of claim 2, wherein the frequency value lies in a range from 0.5 Hertz to 150 Hertz.

4. The method of claim 1, wherein the fitting is performed using cubic-spline interpolation.

5. The method of claim 1, wherein the fitting is performed using a least squares fit.

6. The method of claim 2, further comprising:

repeating the steps of dividing, fitting and subtracting, using a new time interval of different length than the previous time interval, a length of the new time interval corresponding to another frequency value of the baseline drift.

7. The method of claim 6, wherein the other frequency value is of higher value than the previous frequency value.

8. The method of claim 6, wherein the steps are repeated based on an evaluation of a flatness of the flat-baselined bio signal.

9. The method of claim 8, further comprising:

evaluating the flatness by fitting an evaluation function to the flat-baselined bio signal and examining a magnitude of the evaluation function.

10. The method of claim 9, further comprising:

repeating the steps when the magnitude exceeds a predetermined threshold value.

11. The method of claim 6, wherein the steps are repeated as a function of a comparison between a variation in a value of the baseline functions to a resolution of an analog-to-digital converter used to generate the bio signal.

12. The method of claim 11, further comprising:

repeating the steps when the variation exceeds the resolution.

13. The method of claim 1, wherein the bio signal is an electrocardiogram signal.

14. The method of claim 1, in which baseline drift is eliminated resulting in a flat baseline of the bio signal.

15. A device for reducing baseline drift in a biological (bio) signal, the device being constructed and arranged to:

divide the bio signal into a plurality of shorter signals having fixed time intervals;

fit a baseline function to a baseline of each of the shorter signals; and

subtract each baseline function from a corresponding shorter signal, thereby flattening the baseline of the bio signal.

16. A device according to claim 15, comprising:

a communications arrangement configured to receive the bio signal; and

a processor configured to divide the bio signal into a plurality of shorter signals having fixed time intervals, fit the baseline function to a baseline of each of the shorter signals, and subtract each baseline function from a corresponding shorter signal, thereby flattening the baseline of the bio signal.

17. A device according to claim 16, comprising memory including instructions configuring the processor to divide the bio signal into a plurality of shorter signals having fixed time intervals, fit the baseline function to a baseline of each of the shorter signals, and subtract each baseline function from a corresponding shorter signal, thereby flattening the baseline of the bio signal.

18. The device of claim 15, wherein a length of the time intervals corresponds to a frequency value of the baseline drift.

19. The device of claim 18, wherein the frequency value lies in a range from 0.5 Hertz to 150 Hertz.

20. The device of claim 16, wherein the processor is configured to perform the fitting using cubic-spline interpolation.

21. The device of claim 16, wherein the processor is configured to perform the fitting using a least squares fit.

22. The device of claim 17, wherein the instructions direct the processor to:

repeat the steps of dividing, fitting and subtracting using a new time interval of different length than the previous time interval, a length of the new time interval corresponding to another frequency value of the baseline drift.

23. The device of claim 22, wherein the other frequency value is of higher value than the previous frequency value.

24. The device of claim 22, wherein the processor is configured to repeat the steps based on an evaluation of a flatness of the flat-baselined bio signal.

25. The device of claim 24, wherein the processor is configured to evaluate the flatness by fitting an evaluation function to the flat-baselined bio signal and examining a magnitude of the evaluation function.

26. The device of claim 25, wherein the processor is configured to repeat the steps when the magnitude exceeds a predetermined threshold value.

27. The device of claim 22, wherein the steps are repeated as a function of a comparison between a variation in a value of the baseline functions to a resolution of an analog-to-digital converter used to generate the bio signal.

28. The device of claim 27, wherein the processor is configured to repeat the steps when the variation exceeds the resolution.

29. The device of claim 15, wherein the bio signal is an electrocardiogram signal.

30. A computer-readable storage medium having stored thereon a series of instructions executable by a processor for removing noise from a digital signal, the instructions configured to cause the processor to perform the steps of:

dividing the bio signal into a plurality of shorter signals having fixed time intervals;

fitting a baseline function to a baseline of each of the shorter signals; and

subtracting each baseline function from a corresponding shorter signal, thereby flattening the baseline of the bio signal.