Physiological waveform detector

• US 3,939,824 A
• Filed: 01/09/1975
• Issued: 02/24/1976
• Est. Priority Date: 10/09/1973
• Status: Expired due to Term

• Current Assignee: Marquette Electronics (General Electric Company)
• Original Assignee: General Electric Company
• Inventors: Arneson, Harold N., Heitlinger, Louis J.
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/539,698
• Time in Patent Office: 411 Days
• Field of Search: 128/2.06 A, 128/2.06 B, 128/2.06 F, 128/2.06 G, 128/2.05 A, 128/2.05 M, 128/2.05 P, 128/2.05 Q, 128/2.05 R, 128/2.05 T
• US Class Current: 600/485
• CPC Class Codes: A61B 5/02116 of pulse wave amplitude A61B5/02225 takes precedence
• 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
• CPC Class Codes: Y10S 128/901 Suppression of noise in electric signal

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 a waveform signal portion in the presence of other signals by using the characteristic time rate of change or slope of the waveform signal portion as criteria for its existence, comprising:

A. means for differentiating said waveform signal to produce a differentiated signal having a portion whose magnitude is representative of said slope criteria,

b. means for detecting the peak magnitude of said differentiated signal,

c. means for producing a reference signal including means for converting said peak magnitude signal to a signal representing a predetermined percentage thereof, said last named signal constituting said reference signal and corresponding in magnitude with the derivative of the slope of said waveform signal portion,

d. comparator means having inputs for receiving said differentiated signal and reference signal, respectively, said comparator means producing an output signal change when said differentiated signal magnitude is greater than said reference signal,

e. timing means responsive to occurrence of said last named output signal change by initiating measurement of a first time interval which, if completed, is indicative of said waveform portion meeting the time criteria, said timing means also being responsive to terminate measurement of said first interval if said output signal discontinues before expiration of said predetermined period,

f. means responsive to completion of said first time interval by actuating said timing means to continue to measure a second time interval, and

g. resetting means responsive to completion of said second interval by resetting said reference signal producing means to produce a reference signal having a different value than the preceding reference signal existing when said comparator produced the aforementioned output signal.

2. A device for detecting a particular waveform signal in the presence of other signals, comprising:

a. means for differentiating said signals,

b. means for detecting a peak value of said differentiated signal,

c. means for sampling said detected peak value signal in response to a signal indicative of said particular waveform being detected,

d. means for producing a reference signal from said sampled peak signal which said reference signal is a predetermined percentage of the sampled peak magnitude of said differentiated signal,

e. means for continuously comparing said differentiated signal with said reference signal, said comparing means changing its output signal in response to said differentiated signal exceeding said reference signal as an indication of a magnitude characteristic of said particular waveform,

f. timing means responsive to said output signal change by initiating measurement of a first predetermined time interval indicative of a time characteristic of said particular waveform, and

g. output means responsive to said timing means reaching said predetermined interval by producing an output signal incidative of said particular waveform being detected.

3. A device for detecting the minimum and maximum magnitudes of a particular waveform signal in the presence of other signals by using plural characteristics of said waveform signal for identification thereof, comprising:

a. means for receiving and differentiating said signals,

b. means for producing a reference signal,

c. means for comparing the magnitude of said differentiated signals with the magnitude of said reference signal, said comparing means changing its output signal in response to said differentiated signal magnitude being greater than said reference signal magnitude, said signal change being indicative of one characteristic of said waveform if said change is sustained for a predetermined time interval and being indicative of a waveform which it is not desired to detect if it is sustained for less than said predetermined time interval.

d. timing means for measuring the duration of said change,

means for detecting said undifferentiated waveform signal, and

f. means for sampling the minimum and maximum magnitudes of said last named detected signal in response to said timing means measuring a change duration at least as long as said predetermined interval, and

means for storing said minimum and maximum signals.

4. A device for detecting a particular waveform signal in the presence of other signals, comprising:

a. means for receiving and producing differentiated signals whose time intervals correspond with the slopes of the signals wherein the slope of the waveform signal of interest is identified by it having a known first predetermined time interval,

b. means for producing a reference signal which is representative of the magnitude of said derivative of said waveform signal;

c. means for sampling the peak of said differentiated signal in response to said particular waveform being detected,

d. means responsive to said timing means timing a second interval by resetting said reference signal producing means to a new signal level,

e. means for comparing said differentiated signals with said reference signal whereby if any differentiated signal is greater than said reference signal for said first predetermined time interval it is indicative of detecting said particular waveform signal of interest and if greater than said reference signal for other than said predetermined interval it is indicative of a signal which is not of interest, said comparing means producing an output signal when said differentiated signal is greater, and

f. timing means for determining the intervals of said signals whereby to accept signals of interest and reject signals which are not of interest.

5. The device set forth in claim 4 wherein:

a. said means for producing a reference signal includes means for detecting the peak value of said differentiated signal,

b. first storage means for storing said peak value,

c. second storage means,

d. switch means operable by selected signals to transfer said peak value to said second storage means,

e. said means for producing said reference signal being controlled by the value in said second storage means to produce a reference signal which is a predetermined percent of said peak value.

f. said timing means being responsive to said differentiated signal exceeding said reference signal for a predetermined time by continuing timing and producing a first output signal and a later second output signal,

g. said switch means responding to said first output signal by said transferring of said peak value from said first to said second storage means, said second output signal resetting said first storage means to enable said first storage means to store the ensuing detected peak value.

6. The device set forth in claim 5 including:

a. further timing means adapted to be reset to restart a substantial time interval upon occurence of each of said first output signals and to produce a further output signal at the end of said substantial timing interval if said further timing means is not reset, and

b. means for producing a predetermined potential, said switch means being responsive to occurrence of said further output signal by applying said predetermined potential to said second storage means whereby to update the potential in said second storage means if said first output signal does not occur within said substantial time interval.

7. The device set forth in claim 5 including:

a. circuit means including switch means connected to said first storage means, said last named switch means being operated in response to occurrence of said second output signal from said timing means to update the signal in said first storage means.