Adaptive line noise canceler and detector for ECG signals

• US 6,041,250 A
• Filed: 05/20/1998
• Issued: 03/21/2000
• Est. Priority Date: 05/21/1997
• Status: Expired due to Term

• Current Assignee: Mortara Instrument, Inc. (Baxter International Inc.)
• Original Assignee: Quinton Instrument Company
• Inventors: dePinto, Victor M.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US09/081,890
• Time in Patent Office: 671 Days
• Field of Search: 600/509, 600/521
• US Class Current: 600/509
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/308 for electrocardiography [ECG]
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/346 Analysis of electrocardiograms
• CPC Class Codes: H03D 7/165 at least two frequency changers being located in different paths, e.g. in two paths with carriers in quadrature combined with amplitude demodulation H03D1/2245, combined with angle demodulation H03D3/007; N-path filters H03H19/002
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

An adaptive line noise detection and cancellation system having a baseline wander filter, high and low pass filters, an adaptive line noise canceler and various noise detectors is provided to identify, signal and remove contamination from an ECG signal wherein the ECG signal is conditioned to remove various portions of the ECG signal prior to processing in various noise detectors while minimizing the signal conditioning effect of the filters on the ECG signal and while further providing the operator with the ability to manually or automatically activate the filters and to indicate the status of the filters on a printout or display.

Claims

1. A device for detecting and removing noise from an ECG signal comprising:

an ECG signal input for receiving an ECG signal from a patient;

an ECG gate signal which has a portion of said ECG signal blanked from a point in time just prior to the onset of the QRS portion of said ECG signal and ending at a point in time just after the end of the QRS portion; and

an adaptive line noise canceler for removing line noise from said ECG signal wherein said adaptive line noise canceler receives said ECG signal and said ECG gate signal adjusts to changes in said ECG signal from said ECG input to remove varying amounts of said line noise from said ECG signal.

2. The device of claim 1 wherein said adaptive line noise canceler removes said line noise from said ECG signal from said ECG input by producing a sinusoidal wave that matches the component of said ECG signal which is induced by said line noise.

3. The device of claim 1 wherein said adaptive noise canceler includes a quadrature sine wave generator therein.

4. The device of claim 1 wherein said adaptive line noise canceler includes a frequency tripler to remove the third harmonic of said line noise from said ECG signal.

5. The device of claim 1 further including a low pass filter for attenuating the components of said ECG signal above a preselected cutoff frequency and for passing the components of said ECG signal below said preselected cutoff frequency and a delay member for delaying said ECG signal for a time approximately equal to the time said low pass filter requires to pass the components of said ECG signal and a summer for subtracting the components of said ECG signal which are passed through said low pass filter from said ECG signal components from said delay member for processing said ECG signal prior to the receipt of said ECG signal by said adaptive line noise canceler.

6. The device of claim 1 wherein said adaptive line noise canceler includes a switch and said ECG gate signal is applied thereto to prevent said ECG signal from causing distortion in said adaptive line noise canceler.

7. The device of claim 1 wherein said device further includes at least one high pass filter therein to remove components of said ECG signal below a preselected cutoff frequency and for passing the components of said ECG signal above said preselected cutoff frequency.

8. The device of claim 1 further including at least one noise detector to signal to the operator of the device that noise exists in said ECG signal from said ECG input.

9. The device of claim 1 wherein said adaptive line noise canceler comprises a quadrature detector.

10. A device for detecting and removing noise from an ECG signal comprising:

an ECG signal input for receiving an ECG signal from a patient;

an ECG gate signal which has a portion of said ECG signal blanked from a point in time just prior to the onset of the QRS portion of said ECG signal and ending at a point in time just after the end of the QRS portion;

means, connected to said input for attenuating and delaying the frequency components of said ECG signal to filter said ECG signal;

means, connected to said means for filtering for removing line noise from said ECG signal wherein said means receives said ECG signal and said ECG gate signal and adjusts to said ECG signal from said ECG input to remove varying amounts of said line noise from said ECG signal in response to changes in said ECG signal.

11. The device of claim 10 further including at least one detector means and wherein said detector means provides a visual indication to the operator of the device that said line noise exists in said ECG signal of said ECG input.

12. The device of claim 10 further including at least one detector means and wherein said detector means activates at least one filter to remove said line noise from said ECG signal.

13. The device of claim 10 wherein said means for removing line noise includes a quadrature sine wave generation means therein.

14. The device of claim 13 wherein said means for removing line noise includes a frequency tripler to remove the third harmonic of said line noise from said ECG signal.

15. The device of claim 10 wherein said means for removing line noise includes a means for frequency multiplication to remove the harmonics of said line noise from said ECG signal.

16. A device for detecting and removing noise from an ECG signal comprising:

an ECG signal input for receiving an ECG signal from a patient;

an ECG gate signal which has a portion of said ECG signal blanked from a point in time just prior to the onset of the QRS portion of said ECG signal and ending at a point in time just after the end of the QRS portion;

a filter connected to said ECG input for removing contamination from said ECG signal; and

an adaptive line noise canceler for removing line noise from said ECG signal wherein said adaptive line noise canceler receives said ECG signal and said ECG gate signal and adjusts to said ECG signal from said ECG input to remove varying amounts of said line noise from said ECG signal.

17. The device of claim 16 further including at least one noise detector to signal to the operator of the device that noise exists in said ECG signal from said ECG input.

18. The device of claim 16 further including at least one switch which is activated by said ECG gate signal to switch the application of said ECG signal to said at least one noise detector.

19. The device of claim 16 wherein said adaptive line noise canceler includes at least one multiplier therein to multiply said ECG signal by a cosine wave.

20. The device of claim 16 wherein said adaptive line noise canceler includes at least one multiplier therein to multiply said ECG signal by a sine wave.

21. The device of claim 16 wherein said adaptive line noise canceler includes at least one low pass filter therein to filter said ECG signal.

22. The device of claim 21 wherein said low pass filter is a second order butterworth filter.

23. The device of claim 16 wherein said adaptive line noise canceler includes a frequency tripler to remove the third harmonic of said line noise from said ECG signal.

24. The device of claim 16 wherein said adaptive line noise canceler includes a quadrature sine wave generator therein.

25. A method for detecting and removing noise from an ECG signal comprising:

providing an ECG signal input for receiving an ECG signal from a patient;

providing an ECG gate signal which has a portion of said ECG signal blanked from a point in time just prior to the onset of the QRS portion of said ECG signal and ending at a point in time just after the end of the QRS portion;

providing the ECG signal and ECG gate signal to an adaptive line noise canceler for removing line noise from the ECG signal and adjusting the adaptive line noise canceler to changes in the ECG signal to remove varying amounts of line noise from the processed ECG signal.

26. The method of claim 25 wherein at least one noise detector is provided and the at least one noise detector activates at least one filter to remove the detected noise from the ECG signal.

27. The method of claim 25, further includes the step of presenting the ECG signal and the gated ECG signal to the adaptive line noise canceler to improve detection of the line noise by removing CRS portion of the ECG signal during the detection of line noise.

28. A method for detecting and removing noise from an ECG signal comprising:

providing an ECG signal input for receiving an ECG signal from a patient;

providing the ECG signal to a filter having an ECG input thereon and processing the ECG signal to remove contamination from the ECG signal;

providing the processed ECG signal to an adaptive line noise canceler for removing line noise from the processed ECG signal and adjusting the adaptive line noise canceler to the processed ECG signal to remove varying amounts of line noise from the processed ECG signal; and

providing at least one noise detector to signal to an operator of the device that noise exists in the ECG signal.

29. The method of claim 28 wherein the at least one noise detector activates at least one filter to remove the noise from the said ECG signal upon the detection of line noise in the ECG signal.

30. The method of claim 28 wherein the ECG signal is also processed with a QRS gate switch for use in the adaptive line noise canceler to create a gated ECG signal which has the QRS portion of the ECG signal removed therefrom.