Variable bandwidth ECG high pass filter

1. A variable bandwidth electrocardiogram high pass filter comprising:

a baseline low pass filter including a series connection of a boxcar finite impulse response low pass filter and a Butterworth 2 nd order infinite impulse response low pass filter for low pass filtering a baseline unfiltered electrocardiogram signal (ECG bu ) to output a filtered baseline signal (BSE f ),

wherein the baseline low pass filter further includes a baseline wander estimator operably connected to at least one of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter for dynamically adjusting a corner frequency of the baseline low pass filter as a function of an estimation of any baseline wander within the baseline unfiltered electrocardiogram signal (ECG bu );

a signal delay for time delaying the baseline unfiltered electrocardiogram signal (ECG bu ) to output a delayed baseline unfiltered electrocardiogram signal (ECGd bu ); and

a signal extractor connected to the baseline low pass filter and the signal delay for extracting the filtered baseline signal (BSE f ) from the delayed baseline unfiltered electrocardiogram signal (ECGd bu ) to output a baseline filtered electrocardiogram signal (ECG bf ).

2. The variable bandwidth electrocardiogram high pass filter of claim 1 ,

wherein the boxcar finite impulse response low pass filter includes a plurality of coefficients;

wherein the Butterworth 2 nd order infinite impulse response low pass filter has a corner frequency; and

wherein the series connection of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter outputs the baseline filtered electrocardiogram signal (ECG bf ) being nonresponsive to a ramping of the baseline unfiltered electrocardiogram signal (ECG bu ) as a function of a ratio of a current sample coefficient of the boxcar finite impulse response low pass filter to an inverse of the corner frequency of the Butterworth 2 nd order infinite impulse response low pass filter.

3. The variable bandwidth electrocardiogram high pass filter of claim 2 , wherein the corner frequency of the Butterworth 2 nd order infinite impulse response low pass filter is a function of the estimation of any baseline wander within the baseline unfiltered electrocardiogram signal (ECG bu ).

4. The variable bandwidth electrocardiogram high pass filter of claim 2 , wherein a prior sample coefficient of the boxcar finite impulse response low pass filter is a constant minus the current sample coefficient.

5. The electrocardiogram high pass filter of claim 1 , wherein the series connection of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter includes a gain of the baseline low pass filter being equal to a gain of the signal delay.

6. An electrocardiogram monitor, comprising:

a signal processor operable to generate an electrocardiogram waveform of a heart of a patient, wherein the signal processor includes

a baseline low pass filter including a series connection of a boxcar finite impulse response low pass filter and a Butterworth 2 nd order infinite impulse response low pass filter cooperatively for low pass filtering a baseline unfiltered electrocardiogram signal (ECG bu ) to output a filtered baseline signal (BSE f ),

wherein the baseline low pass filter further includes a baseline wander estimator connected to at least one of the finite impulse response filter and the infinite impulse response low pass filter, for dynamically adjusting a corner frequency of the baseline low pass filter as a function of an estimation of any baseline wander within the baseline unfiltered electrocardiogram signal (ECG bu ),

a signal delay for time delaying the baseline unfiltered electrocardiogram signal (ECG bu ) to output a delayed baseline unfiltered electrocardiogram signal (ECGd bu ), and

a signal extractor connected to the baseline low pass filter and the signal delay for extracting the filtered baseline signal (BSE f ) from the delayed baseline unfiltered electrocardiogram signal (ECGd bu ) to output a baseline filtered electrocardiogram signal (ECG bf ); and

an electrocardiogram display operably connected to the signal processor to display the electrocardiogram waveform.

7. The electrocardiogram monitor of claim 6 ,

wherein the boxcar finite impulse response low pass filter includes a plurality of coefficients;

wherein the Butterworth 2 nd order infinite impulse response low pass filter has a corner frequency; and

wherein the series connection of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter outputs the baseline filtered electrocardiogram signal (ECG bf ) being nonresponsive to a ramping of the baseline unfiltered electrocardiogram signal (ECG bu ) as a function of a ratio of a current sample coefficient of the boxcar finite impulse response low pass filter to an inverse of a corner frequency of the Butterworth 2 nd order infinite impulse response low pass filter.

8. The electrocardiogram monitor of claim 7 , wherein the corner frequency of the Butterworth 2 nd order infinite impulse response low pass filter is a function of a corner frequency of the estimation of any baseline wander within the baseline unfiltered electrocardiogram signal (ECG bu ).

9. The electrocardiogram monitor of claim 7 , wherein a prior sample coefficient of the boxcar finite impulse response low pass filter is a constant minus the current sample coefficient.

10. The electrocardiogram monitor of claim 6 , wherein the series connection of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter includes a gain of the baseline low pass filter being equal to a gain of the signal delay.

11. A defibrillator, comprising:

an electrocardiogram monitor operable to generate an electrocardiogram waveform of a heart of a patient, wherein the electrocardiogram monitor includes

a baseline low pass filter including a series connection of a boxcar finite impulse response low pass filter and a Butterworth 2 nd order infinite impulse response low pass filter for low pass filtering a baseline unfiltered electrocardiogram signal (ECG bu ) to output a filtered baseline signal (BSE f ),

wherein the baseline low pass filter further includes a baseline wander estimator connected to at least one of the finite impulse response filter and the infinite impulse response low pass filter for dynamically adjusting a corner frequency of the baseline low pass filter as a function of an estimation of any baseline wander within the baseline unfiltered electrocardiogram signal (ECG bu ),

a signal delay for time delaying the baseline unfiltered electrocardiogram signal (ECG bu ) to output a delayed baseline unfiltered electrocardiogram signal (ECGd bu ), and

a signal extractor connected to the baseline low pass filter and the signal delay for extracting the filtered baseline signal (BSE f ) from the delayed baseline unfiltered electrocardiogram signal (ECGd bu ) to output a baseline filtered electrocardiogram signal (ECG bf );

a shock source operable to store shock energy; and

a defibrillation controller operably connected to the electrocardiogram monitor and the shock source to control a delivery of the shock energy to the hearth of the patient responsive to a QRS analysis of the electrocardiogram waveform.

12. The defibrillator of claim 11 ,

wherein the boxcar finite impulse response low pass filter includes a plurality of coefficients;

wherein the Butterworth 2 nd order infinite impulse response low pass filter has a corner frequency; and

wherein the series connection of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter outputs the baseline filtered electrocardiogram signal (ECG bf ) being nonresponsive to a ramping of the baseline unfiltered electrocardiogram signal (ECG bu ) as a function of a ratio of a current sample coefficient of the boxcar finite impulse response low pass filter to an inverse of a corner frequency of the Butterworth 2 nd order infinite impulse response low pass filter.

13. The defibrillator of claim 12 , wherein the corner frequency of the Butterworth 2 nd order infinite impulse response low pass filter is a function of a corner frequency of the estimation of any baseline wander within the baseline unfiltered electrocardiogram signal (ECG bu ).

14. The defibrillator of claim 12 , wherein a prior sample coefficient of the boxcar finite impulse response low pass filter is a constant minus the current sample coefficient.

15. The defibrillator of claim 11 , wherein the series connection of the boxcar finite impulse response low pass filter and the Butterworth 2 nd order infinite impulse response low pass filter includes a gain of the baseline low pass filter being equal to a gain of the signal delay.