Method and device for filtering out baseline fluctuations from an electrocardiogram

• US 5,469,856 A
• Filed: 12/22/1993
• Issued: 11/28/1995
• Est. Priority Date: 03/04/1991
• Status: Expired due to Term

• Current Assignee: Draeger Medical Systems Incorporated (FPS Vermögensverwaltung GmbH)
• Original Assignee: Siemens AG
• Inventors: Karlsson, Peter, Ohlsson, Thomas, Lundstrom, Lena
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): Jastrzab, Jeffrey R.
• Application Number:
  US08/117,069
• Time in Patent Office: 706 Days
• Field of Search: 128/695, 128/696, 128/706, 128/710, 128/901, 128/703, 128/708, 128/902
• 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: A61B 5/347 Detecting the frequency distribution of signals

Abstract

Method and device for filtering out baseline fluctuations from an electrocardiogram. It is known to provide a high pass filter for filtering out baseline fluctuations from an electrocardiogram, the lower cut off frequency of a high pass filter is at a value below the frequencies which are characteristic of the heart signals at the lowest possible heart rate. In order to increase the effectiveness of the baseline filtering, it is provided that in a device (4) the current heartbeat rate is determined from the electrocardiogram and, in dependence thereupon, the lower cut off frequency of the filter (2) is altered in such a manner that the lower cut off frequency is increased in the case of an increasing heartbeat rate and is decreased in the case of a decreasing heartbeat rate.

Claims

1. A method for filtering out baseline fluctuations from an electrocardiogram, comprising the steps of:

determining a current heartbeat rate from said electrocardiogram by subjecting said electrocardiogram to a frequency analysis;

filtering said electrocardiogram in a filter having a lower cut off frequency; and

altering said lower cut off frequency of said filter, by increasing said lower cut off frequency in the presence of an increasing heartbeat rate and decreasing said lower cut off frequency in the presence of a decreasing heartbeat rate.

2. An apparatus for filtering out baseline fluctuations from an electrocardiogram signal comprising:

a bandpass filter having a signal input, a variable lower cut off frequency, a control input and an output, said electrocardiogram signal being supplied to said signal input; and

means connected to said signal input of said filter for determining a heartbeat rate from said electrocardiogram signal, said heartbeat rate being supplied to said control input of said filter for varying said lower cut off frequency dependent on said heartbeat rate.

3. A method for filtering out baseline fluctuations from an electrocardiogram, the method comprising the steps of:

filtering said electrocardiogram in a filter having a lower cut off frequency;

determining a current heartbeat rate from said electrocardiogram by detecting occurrences of QRS complexes having a temporal spacing therebetween in said electrocardiogram; and

forming a reciprocal value from the temporal spacing of successive, detected QRS complexes and altering said lower cut off frequency of said filter dependent on said heartbeat rate.

4. An apparatus for filtering out baseline fluctuations from an electrocardiogram signal comprising:

a filter having a signal input, a variable lower cut off frequency, a control input and an output, said electrocardiogram signal being supplied to said signal input; and

a frequency analyzer capable of determining a heartbeat rate from said electrocardiogram signal, said frequency analyzer connected to said signal input of said filter, said heartbeat rate being supplied to said control input of said filter for varying said lower cut off frequency dependent on said heartbeat rate.

5. An apparatus for filtering out baseline fluctuations from an electrocardiogram signal comprising:

a filter having a signal input, a variable lower cut off frequency, a control input and an output, said electrocardiogram signal being supplied to said signal input;

a QRS detector connected to said signal input of said filter to determine a heartbeat rate from said electrocardiogram signal, said QRS detector having an output;

measurement means connected to said output of said QRS detector for measuring chronological spacing between successive, detected QRS complexes, said measurement means having an output; and

means connected to said output of said measurement means for forming a reciprocal of said chronological spacing indicative of said heartbeat rate, said heartbeat rate being supplied to said control input of said filter for varying said variable lower cut-off frequency dependent on said heartbeat rate.