Physiological waveform detector

• US 3,878,833 A
• Filed: 10/09/1973
• Issued: 04/22/1975
• Est. Priority Date: 10/09/1973
• Status: Expired due to Term

• Current Assignee: Marquette Electronics Inc (GE Healthcare Technologies, Inc.)
• Original Assignee: Harold N. Arneson, Louis J. Heitlinger
• Inventors: Arneson, Harold N., Heitlinger, Louis J.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/404,408
• Time in Patent Office: 560 Days
• Field of Search: 128/2.6A,2.6B,2.6F,2.6G,2.6R,2.5A,2.5M,2.5P,2.5Q,2.5R,2.05
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02108 from analysis of pulse wave characteristics
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives

Abstract

A physiological waveform detector such as for cardiac R-wave and blood pressure uses a comparator to compare the derivative of the waveform signal with a reference signal representing some percentage of the magnitude of the derivative of the waveform. If the derivative is of sufficient magnitude to trip the comparator a timing circuit begins counting. If the comparator remains tripped for a predetermined interval, the waveform is considered to be the desired one. Means are provided for detecting waveform peaks and valleys. The detector recognizes desired waveforms by two characteristics, one being magnitude and the other being duration.

Claims

1. A device for detecting the R-wave of an ECG waveform by identifying the time rate of change or slope of the R-wave as criteria of its existence to the exclusion of other waveform and noise characteristics, comprising:

a. means for differentiating said waveform and producing a differentiated waveform signal having peaks and valleys, b. means for receiving said differentiAted signal waveform and for converting it to a waveform signal representative of the absolute values of said peaks and valleys, c. comparator means having an input for receiving said absolute value signal and another input for receiving a reference signal, said comparator means producing an output signal change for a period during which the magnitude of said absolute value signal is greater than said reference signal, d. means for producing a reference signal including peak detector means receiving said absolute value signal and producing a signal corresponding with the maximum peak value thereof, and means for storing said peak signal for a short period, e. second means and normally nonconductive switch means interposed between said storing means and second means, said switch means being responsive to a control signal by transferring said peak signal to said second means, f. means connected to said second means for producing a signal having a magnitude equal to a predetermined percent of the signal magnitude of said second means, said last named signal constituting said reference signal which is applied to another of said comparator means inputs, said reference signal being representative of the magnitude of said waveform portion, g. timing means responsive to occurrence of an output signal change by said comparator means by initiating measurement of a first time interval which, if completed, is indicative of said R-wave having occurred, said timing means also being responsive to terminate measurement of said first interval if said comparator output signal change discontinues before expiration of said characteristic period as indicative of a signal other than an R-wave having occurred, h. means responsive to completion of said first time interval by actuating said timing means to continue to measure second and third time intervals, i. means responsive to completion of said second time interval by producing a control signal for operating said switch means to transfer said existing peak signal to said second means, and, j. means responsive to completion of said third time interval by resetting the signal on said first peak detector means to a level at which it can accept the next ensuing peak.

2. The device set forth in claim 1 wherein:

a. said first time interval is about 11 milliseconds.

3. The device set forth in claim 1 wherein:

a. said first time interval is about 11 to 11.5 milliseconds.

4. The device set forth in claim 1 wherein:

a. said first time interval is within the range of 6 to 20 milliseconds.

5. The device set forth in claim 1 wherein:

a. said second time interval is substantially greater than said first time interval.

6. The device set forth in claim 1 wherein:

a. said second time interval is about 125 milliseconds.

7. The device set forth in claim 1 wherein:

a. said third time interval is about 200 milliseconds.

8. The device set forth in claim 1 including:

a. a source of a preestablished voltage, b. normally nonconductive switch means connecting said voltage source to said second means, c. means responsive to the absence of a detected R-wave for an interval substantially greater than said third interval by causing said last named switch means to become conductive to thereby establish a predetermined voltage on said second means.

9. A device for detecting R-wave of an ECG waveform signal in the presence or absence of other signals by determining the magnitude and predetermined slope of the R-wave signals to the exclusion of other signals, comprising:

a. means for differentiating said waveform signal which produces negative going and positive going signals, b. means for converting said signals to signals representative of their absolute values, c. comparator means for comparing said absolute value of said differentiated signals with a reference signal, said comparator means undergoinG an output signal change in response to the absolute value of said differentiated signals being greater than the magnitude of said reference signal, said greater signal being a criteria for waveform signals of interest as well as for other signals, d. means for detecting the peak of said absolute value signal including first means and second means for storing said peak signal, e. switch means selectively operative to transfer said peak signal from said first to said second storage means, f. means controlled by said second signal storage means to produce a signal representing a predetermined percent of said peak signal magnitude, said last named signal constituting said reference signal, g. time measuring means responsive to said comparator means undergoing an output signal change by measuring the time interval during which said change exists, said time measuring means being responsive to it measuring a predetermined interval by continuing to measure a second time interval, and said switch means being operative to transfer said peak signal in response to said measuring means measuring said second time interval.

10. The device set forth in claim 9 wherein:

a. said reference signal magnitude is about 43 percent of said peak signal magnitude.

11. The device set forth in claim 9 wherein:

a. said reference signal magnitude is in the range of 20 to 60 percent of said peak signal magnitude.

12. The device set forth in claim 9 wherein:

a. said predetermined time interval is in the range of 6 to 20 milliseconds.

13. The device set forth in claim 9 wherein:

a. said predetermined time interval is about 11 milliseconds.

14. The device set forth in claim 9 wherein:

a. said predetermined time interval is about 11.5 milliseconds.

15. The device set forth in claim 9 wherein:

a. said second interval is about 125 milliseconds.

16. The device set forth in claim 9 wherein:

a. said time measuring continues to measure a third time interval in addition to said second interval, and b. means responsive to completion of said third interval by resetting the signal on said first peak signal storage means to a lower than previously level, whereby to enable it to receive and store the next ensuing peak absolute value signal.

17. The invention set forth in claim 9 including:

a. second time measuring means responsive to completion of said second time interval by initiating a timing period on the order of a few seconds which is completed if another of said second intervals is not completed within said period, b. a voltage source and switch means connected between said source and said second peak signal storage means, c. completion of said timing period causing said last named switch means to apply the voltage of said source to said second peak signal storage means, whereby to update the signal on said storage means if an R-wave is not detected in said few seconds.

18. The device set forth in claim 9 wherein said time measuring means are counting means, and including:

a. first gate means having an input connected to receive signals from said comparator means and another input, said means also having an output connected to said counting means for controlling said counting means, b. flip-flop switch means having an output connected to said other input of said gate means, c. further gate means connected between the outputs of said counting means and said flip-flop means for changing the output state thereof in response to said counting means making a number of counts equivalent in time to said first time interval, d. said comparator input causing said first gate means to turn on said counting means in response to said absolute value signal being greater than said reference signal and said output from said flip-flop means at the end of said first interval causing said first gate means to maintain said counting means counting for an interval grEater than said first interval.

19. A device for determining in a blood pressure waveform signal the peak and valley representative of systolic and diastolic blood pressure by detecting the systolic upslope of the waveform signal, comprising:

a. means for receiving and differentiating said waveform signal and producing a differentiated signal corresponding with said upslope, b. means for detecting the minimum magnitude of said differentiated signal and means for storing said minimum peak signal, c. means controlled by said stored signal to produce a reference signal proportional thereto, d. comparator means having an input for said differentiated signal and another input for said reference signal and said means having an output which changes state when said differentiated signal becomes greater in magnitude than said reference signal, e. systolic peak signal detector means for receiving said waveform signal and for producing a signal having the magnitude of said systolic peak, and first and second means for storage of said systolic peak and first switch means operable to transfer said signal from said first to said second storage means, f. diastolic valley signal detector means for receiving said waveform signal and for producing a signal having the magnitude of said diastolic valley, and first and second means for storage of said valley signal and second switch means operable to transfer said valley signal from said first to said second storage means, g. time measuring means responsive to said comparator means changing state by measuring the time interval during which said differentiated signal has a greater magnitude than said reference signal, h. means for actuating said timing means to continue measuring time for a second interval in response to said measured interval exceeding a predetermined interval, which predetermined interval is indicative of a systolic upslope having occurred, and i. means for operating said first and second switching means to transfer said peak and valley signal to said first and second storage means, respectively, at the completion of said second interval, said transferred signal, respectively, corresponding with systolic and diastolic blood pressure.

20. The device set forth in claim 9 wherein:

a. said first predetermined time interval is selected from the range of 10 to 40 milliseconds.

21. The device set forth in claim 9 wherein:

a. said first predetermined time interval is about 21 milliseconds.

22. The device set forth in claim 9 wherein:

a. said second time interval is about 200 milliseconds.

23. The device set forth in claim 9 wherein:

a. said second time interval is at least 140 milliseconds.

24. The device set forth in claim 9 wherein:

a. said time measuring means measures a third time interval, b. means responsive to completion of said third time interval by producing a resetting signal, and c. switch means connected to said storage means of said peak detector, said swtich means responding to said resetting signal by conducting and changing the signal stored on said peak signal storing means to a lower level for enabling detection of the next ensuing signal peak.

25. The device set forth in claim 24 including:

a. switch means to said storage means of said valley detector, said switch means responding to said resetting signal by conducting and changing the signal stored on said valley signal storing means to a higher level for enabling detection for the next ensuing valley signal.

26. The device set forth in claim 9 including means for updating the signal on said second storage means of said diastolic valley detector if a systolic upslope is not detected for a certain time period, comprising:

a. timing means controlled by said time measuring means to produce a signal at said certain time on the order of seconds after the last systolic upslope is detected, b. means responsive to occurrence oF said last named signal by producing a signal for causing said switching means to conduct and transfer said diastolic valley signal from said storage means to said second storage means to thereby update the diastolic pressure signal on said second storage means.