ECG noise detection system

• US 5,983,127 A
• Filed: 05/20/1998
• Issued: 11/09/1999
• Est. Priority Date: 05/21/1997
• Status: Expired due to Fees

• Current Assignee: Quinton, Inc. (Pfizer Inc.)
• Original Assignee: Quinton Instrument Company
• Inventors: dePinto, Victor M.
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US09/082,257
• Time in Patent Office: 538 Days
• Field of Search: 128/901, 600/508, 600/509
• US Class Current: 600/509
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• 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

A noise detection 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.

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;

a baseline wander filter connected to said ECG input for removing baseline wander from said ECG signal;

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

at least one noise detector to signal to the operator of the device that noise exists in said ECG signal from said ECG input.

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 a local power line.

3. The device of claim 1 wherein said at least one noise detector provides a visual indication to the operator of the device that noise exists in said ECG signal of said ECG input.

4. The device of claim 3 wherein said at least one noise detector activates at least one filter to remove said noise from said ECG signal.

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

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

7. The device of claim 1 wherein said baseline wander filter includes 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 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.

8. The device of claim 7 further including a baseline wander detector which compares an output from said low pass filter with a predetermined value to determine if baseline wander is present in said ECG signal.

9. The device of claim 1 further including 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.

10. The device of claim 9 wherein said ECG gate signal is applied to said adaptive line noise canceler.

11. The device of claim 10 wherein said ECG gate signal is applied to a pulse stretcher to increase the duration of said ECG gate signal to operate a switch prior to the application of said ECG signal to said at least one noise detector.

12. 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.

13. The device of claim 12 wherein said high pass filter is an elliptic filter.

14. The device of claim 12 wherein said high pass filter includes first and second order stages.

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

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

means, connected to said input for attenuating and delaying the frequency components of said ECG signal for removing baseline wander from said ECG signal;

means, connected to said means for removing baseline wander for removing line noise from said ECG signal wherein said means adjusts to said ECG signal from said ECG input to remove varying amounts of said line noise from said ECG signal; and

means, connected to said ECG signal to signal to the operator of the device that noise exists in said ECG signal from said ECG input.

16. The device of claim 15 wherein said means to signal provides a visual indication to the operator of the device that noise exists in said ECG signal of said ECG input.

17. The device of claim 15 wherein said means to signal activates at least one filter to remove said noise from said ECG signal.

18. 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.

19. The device of claim 18 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.

20. The device of claim 19 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.

21. 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 baseline wander filter having an ECG input thereon and processing the ECG signal to remove baseline wander 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 the operator of the device that noise exists in the ECG signal.

22. The method of claim 21 wherein the at least one noise detector activates at least one filter to remove the noise the said ECG signal.

23. The method of claim 21 wherein the ECG signal is also processed with a QRS gate switch to create a gated ECG signal which is presented to the adaptive line noise canceler in addition to the ECG signal.