Method and apparatus for distinguishing electric signal waveforms

• US 5,417,221 A
• Filed: 05/07/1993
• Issued: 05/23/1995
• Est. Priority Date: 05/29/1990
• Status: Expired due to Term

• Current Assignee: Psytech Incorporated
• Original Assignee: Psytech Incorporated
• Inventors: Sickler, Robert L.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US08/057,433
• Time in Patent Office: 746 Days
• Field of Search: 128/696, 128/703-708, 128/901, 128/902, 307/517, 328/114, 328/165
• US Class Current: 600/509
• CPC Class Codes: A61B 5/30 Input circuits therefor
• CPC Class Codes: A61B 5/349 Detecting specific parameters of the electrocardiograph cycle
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

Abstract

The heart rate of a subject during strenuous physical exercise is monitored accurately by feeding the plurality of electric signals of diverse amplitudes generated by transducers engaging the skin of the subject, to a variably controlled gain amplifier to adjust the amplitudes to within a predetermined amplitude range, feeding the adjusted amplitude signals to a slew rate filter formed of a pair of slew rate limiters to compare the slew rates of the adjusted signals, feeding the compared signals to a slew rate limit comparator to separate from the QRS waveforms representing heartbeat of the subject those interfering electric signals having slew rates outside the range of slew rates representing QRS waveforms, and monitoring the QRS waveforms. The separation of interfering signals is achieved with minimum complexity of electronic circuitry and correspondingly reduced cost, by feeding the compared signals also to a microprocessor programmed to recognize as interfering signals those waveforms that have slew rates similar to those of the QRS waveforms but originating as waveforms of substantially greater amplitude and/or of an occurrence rate differing from the uniform recurrence rate of QRS waveforms.

Claims

1. Apparatus for identifying a desired electric signal waveform from extraneous electric interference signal waveforms, comprising

a) means for obtaining a plurality of electrical waveforms of diverse amplitude some of which represent desired electric signal waveforms and others of which represent interference waveforms of noise and other extraneous sources which interfere with recognition of the desired electric signal waveforms,

b) means for adjusting the amplitudes of said waveforms to within a predetermined range of amplitudes,

c) means for separating from desired adjusted electric signal waveforms those interference waveforms having slew rates above and below a predetermined range of slew rates representing desired electric signal waveforms, and

d) means for indicating the presence of desired electric signal waveforms.

2. The apparatus of claim 1 wherein the separating means comprises a slew rate filter formed of a pair of slew rate limiters and an algebraic summing amplifier, the limiters having a common input for receiving said electric signal waveforms of adjusted amplitude, and each output being connected to said algebraic summing amplifier.

3. The apparatus of claim 2 wherein the means for separating desired waveforms from interference waveforms comprises a slew rate limit comparator having an output connected to means for indicating the presence of desired electric signal waveforms, and an input connected to the output of one of the slew rate limiters.

4. Apparatus for identifying a desired electric signal waveform from extraneous electric interference signal waveforms, comprising

a) means for obtaining a plurality of electrical waveforms of diverse amplitude some of which represent desired electric signal waveforms and others of which represent interference waveforms of noise and other extraneous sources which interfere with recognition of the desired electric signal waveforms,

b) means for adjusting the amplitudes of said waveforms to within a predetermined range of amplitudes, said means including a variably controlled gain amplifier having an input for receiving said plurality of waveforms of diverse amplitudes, digital gain control means connected to the amplifier for controlling the gain of the amplifier, and a microprocessor connected to the digital gain control means and having a program for adjusting the amplitudes of the desired electrical signal to within said predetermined range, the amplifier having an output connected to separating means,

c) separating means for separating from desired adjusted electric signal waveforms those interference waveforms having slew rates above and below a predetermined range of slew rates representing desired electric signal waveforms, said separating means comprising a slew rate filter formed of a pair of slew rate limiters and an algebraic summing amplifier, the limiters having a common input for receiving said electrical waveforms of adjusted amplitude and each output connected to said algebraic summing amplifier,

d) slew rate limit comparator means having an output connected to the input of said microprocessor, and an input connected to the output of one of the slew rate limiters, and

e) means for identifying the slew rates of said desired separated waveforms, said means comprising said microprocessor and an analog-to-digital converter connected thereto, the microprocessor having an output connected to the digital gain control means, an input connected to the output of the slew rate comparator means, and an output for indicating the presence of desired electric signal waveforms, the microprocessor having a program, first for separating the desired electric signal waveforms by identifying as interference waveforms certain of the waveforms differing from the desired electric signal waveforms in at least one of the characteristics of time duration of the rise and fall of the waveforms, the amplitude of the waveforms, and the recurrence rate of the waveforms, second for controlling the digital gain control means, third for detecting the output of the slew rate comparator means, and fourth for enabling the output of the microprocessor to indicate the presence of the desired electric signal waveforms.

5. Apparatus for identifying the desired QRS electric signal waveform of the heartbeat of a subject from extraneous electric interference signal waveforms, comprising

a) means for obtaining a plurality of electrical waveforms of diverse amplitude some of which represent desired QRS electric signal waveforms and others of which represent interference waveforms of noise and other extraneous sources which interfere with recognition of the desired QRS electric signal waveforms,

b) means for adjusting the amplitude of said waveforms to within a predetermined range of amplitudes,

c) means for separating from desired adjusted QRS electric signal waveforms those interfering waveforms having slew rates above and below a predetermined range of slew rates representing desired QRS electric signal waveforms, said separating means comprising a slew rate limit comparator having an output connected to means for indicating the presence of desired electric signal waveforms, and an input connected to the output of one of the slew rate limiters, and

d) means for indicating the presence of the desired separated QRS waveforms.

6. Apparatus for identifying the desired QRS electric signal waveform of the heartbeat of a subject from extraneous electric interference signal waveforms, comprising

a) means for obtaining a plurality of electrical waveforms of diverse amplitude some of which represent desired QRS electric signal waveforms and others of which represent interference waveforms of noise and other extraneous sources which interfere with recognition of the desired QRS electric signal waveforms,

b) means for adjusting the amplitude of said waveforms to within a predetermined range of amplitudes, said adjusting means including a variable controlled gain amplifier having an input for receiving said plurality of waveforms of diverse amplitudes, digital gain control means connected to the amplifier for controlling the gain of the amplifier, and a microprocessor connected to the digital gain control means and having a program for adjusting the amplitudes of the QRS waveform to within a predetermined range, the amplifier having an output connected to separating means,

c) means for separating from desired adjusted QRS electric signal waveforms those interference waveforms having slew rates above and below a predetermined range of slew rates representing desired QRS electric signal waveforms, said separating means comprising a slew rate filter formed of a pair of slew rate limiters and an algebraic summing amplifier, the limiters having a common input for receiving said electrical waveforms of adjusted amplitude and each output connected to said algebraic summing amplifier,

d) slew rate limit comparator means having an output connected to the input of the microprocessor, and an input connected to the output of one of the slew rate limiters,

e) said microprocessor connected to an analog-to-digital converter and having an output connected to the digital gain control means, an input connected to the output of the slew rate comparator means, and an output for indicating the presence of desired electric signal waveforms, the microprocessor having a program, first for separating the QRS waveforms by identifying as interference waveforms certain of the waveforms differing from the QRS waveforms in at least one of the characteristics of time duration of the rise and fall of the waveforms, the amplitude of the waveforms, and the recurrence rate of the waveforms, second for controlling the digital-to-analog converter, third for detecting the output of the slew rate comparator means, and fourth for providing output indicating the presence of desired separated QRS waveforms.

7. The method of identifying a desired electric signal waveform from extraneous electric interference signal waveforms, comprising:

a) obtaining a plurality of electrical waveforms of diverse amplitudes some of which represent the desired electric signal waveforms and others of which represent interference waveforms of noise and other extraneous sources which interfere with identification of the desired electric signal waveforms,

b) adjusting the amplitudes of said waveforms to within a predetermined range of amplitudes,

c) comparing the slew rates of said adjusted waveforms,

d) separating from desired electric signal waveforms those interference waveforms having slew rates above and below a predetermined range of slew rates representing desired electric signal waveforms, and

e) providing output indicating the presence of desired separated electric signal waveforms.

8. The method of claim 7 wherein the separating of interference waveforms is achieved by identifying as interference waveforms certain of the waveforms differing from the desired electric signal waveforms in at least one of the characteristics of the time duration of the rise and fall of the waveforms and the amplitude of the waveforms.

9. The method of claim 7 wherein the separating of interference waveforms is achieved by feeding the electrical waveforms to a microprocessor programmed to indentify as interference waveforms certain of the waveforms differing from the desired electrical signal waveforms in at least one of the characteristics of the time duration of the rise and fall of the waveforms, the amplitude of the waveforms, and the recurrence rate of the waveforms.

10. The method of claim 7 for identifying the desired QRS electric signal waveform of the heartbeat of a subject from extraneous electric interference signal waveforms, wherein the obtaining of the electrical waveforms from a subject is achieved by contacting the skin of an exercising subject with transducer means capable of producing electrical signals representing said QRS and interference waveforms.

11. The method of claim 7 for identifying the desired QRS electric signal waveform of the heartbeat of a subject from extraneous electric interference signal waveforms, wherein the separating of interference waveforms is achieved by identifying as interference waveforms certain of the waveforms differing from the QRS waveforms in at least one of the characteristics of the time duration of the rise and fall of the waveforms, the amplitude of the waveforms and the recurrence rate of the waveforms.

12. The method of claim 7 for identifying the desired QRS electric signal waveform of the heartbeat of a subject from extraneous electric interference signal waveforms, wherein the separating of interference waveforms is achieved by feeding the electrical waveforms to a microprocessor having a program for indentifying as interference waveforms certain of the waveforms differing from the QRS waveforms in at least one of the characteristics of the time duration of the rise and fall of the waveforms, the amplitude of the waveforms, and the recurrence rate of the waveforms.

13. The method of claim 7 for identifying the desired QRS electric signal waveform of the heartbeat of a subject from extraneous electric interference signal waveforms, wherein

a) the obtaining of electrical waveforms from the subject is achieved by contacting the skin of an exercising subject with transducer means capable of producing electrical signals representing the QRS waveform and interference waveforms representing muscle artifact, and

b) the separating of interfering waveforms is achieved by feeding the electrical waveforms to a microprocessor having a program for identifying as waveforms certain of the waveforms differing from the QRS waveforms in at least one of the characteristics of the time duration of the rise and fall of the waveforms, the amplitude of the waveforms, and the recurrence rate of the waveforms.

14. Apparatus for identifying a desired electric signal waveform from extraneous electric interference signal waveforms, comprising

a) means for obtaining a plurality of electrical waveforms of diverse amplitude some of which represent desired electric signal waveforms and others of which represent interference waveforms of noise and other extraneous sources which interfere with identification of the desired electric signal waveforms,

b) means for adjusting the amplitude of said waveforms to within a predetermined range of amplitudes,

c) means for separating from desired adjusted electric signal waveforms those interference waveforms having slew rates above and below a predetermined range of slew rates representing desired electric signal waveforms, and

d) means for indicating the presence of desired electric signal waveforms having slew rates within said predetermined range of slew rates.

15. The apparatus of claim 14 wherein the means for adjusting the amplitudes of said waveforms includes a variably

controlled gain amplifier having an input for receiving said plurality of waveforms of diverse amplitudes, digital gain control means connected to the amplifier for controlling the gain of the amplifier, and a microprocessor connected to the digital gain control means and having a program for adjusting the amplitudes of the desired electrical signal to within said predetermined range, the amplifier having an output connected to the separating means.

16. The apparatus of claim 14 for indicating the presence of the desired electric signal waveforms wherein the desired electric signal is the QRS waveform of the heartbeat of a subject, and wherein the means for obtaining electrical waveforms from a subject comprises transducer means for contacting the skin of a subject during physical exercise and capable of conducting electrical signals representing said waveforms.

17. The apparatus of claim 14 wherein the transducer means comprise hand-grip electrodes.