APPARATUS FOR MONITORING RECURRENT WAVEFORMS

• US 3,654,916 A
• Filed: 03/16/1970
• Issued: 04/11/1972
• Est. Priority Date: 03/14/1969
• Status: Expired due to Term

• Current Assignee: James Mcewan Mcintyre Neilson
• Original Assignee: James Mcewan Mcintyre Neilson
• Inventors: Neilson, James McEwan McIntyre
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US05/019,715
• Time in Patent Office: 757 Days
• Field of Search: 128/2.5R,2.6A,2.6R
• US Class Current: 600/515
• CPC Class Codes: A61B 5/316 Modalities, i.e. specific diagnostic methods
• CPC Class Codes: A61B 5/364 Detecting abnormal ECG interval, e.g. extrasystoles, ectopic heartbeats
• CPC Class Codes: A61B 5/7239 using differentiation including higher order derivatives
• CPC Class Codes: A61B 5/7242 using integration
• CPC Class Codes: G01R 29/02 Measuring characteristics of individual pulses, e.g. deviation from pulse flatness, rise time or duration
• CPC Class Codes: G06G 7/60 for living beings, e.g. their nervous systems ; for problems in the medical field

Abstract

An electrocardiogram waveform is monitored by superimposing the waveform complexes upon a stored waveform complex representative of a '"'"''"'"'normal'"'"''"'"' complex, using derived reference levels and timing data and then integrating successive segments of a waveform complex, measuring the difference between the integrated value of each segment in the complex and the integrated value of a corresponding segment of a normal waveform complex, quantitatively summing the differences and producing a signal and/or record if the total difference exceeds a predetermined value.

Claims

1. A method of monitoring a recurrent waveform to detect abnormal waveform complexes consisting in the steps of sensing the recurrent waveform, integrating and storing segments of a normal waveform complex, integrating successive segments of a waveform complex to be compared, measuring the difference between the integrated value of each segment in the complex to be compared and the integrated value of a corresponding segment of the normal waveform complex, quantitatively summing the differences and producing a signal if the total difference exceeds a predetermined value.

2. A method according to claim 1 including using the normal waveform complex to provide a reference waveform, deriving, from the recurrent waveform, timing signals which represent the time location of particular selected parts of the waveform complex required to be compared with corresponding parts of the stored normal complex, deriving a reference voltage level by sampling the recurrent waveform immediately before the start of each complex, and superimposing each waveform complex, by the aid of said timing signals and said reference voltage level, upon the stored reference waveform before effecting said successive integration of segments. A method according to claim 2 wherein said timing signals are derived from the waveform by firstly differentiating each waveform complex twice to obtain peak signals representing the approximate time location of the particular part of the waveform complex selected for comparison with the stored complex, secondly blanking out another version of said second derivative signals during the periods thus established as including said peaks to obtain a threshold level representative of the remainder of the complex plus noise, and comparing the original unblanked second derivative signals with said threshold level to determine the '"'"''"'"''"'"''"'"'sTart'"'"''"'"''"'"''"'"' and '"'"''"'"''"'"''"'"'center'"'"''"'"''"'"''"'"' of that part of each individual waveform complex which is to be superimposed on the stored reference waveform.

4. A method according to claim 3 including feeding the recurrent waveform through a delay line to a trigger section to generate a master timing pulse and a master trigger pulse for each detected waveform complex.

5. A method according to claim 4 wherein said integration of the corresponding segments of the normal waveform complex to be stored and the superimposed waveform complex to be compared with it is successive and carried out by operational amplifiers and including electronically switching the operational amplifiers under the control of the master timing pulses and the master trigger pulses.

6. A method according to claim 5 including obtaining the differences between each integrated segment of the waveform complex and the stored reference waveform and obtaining the sum of the magnitudes of said individual differences over a time interval and selecting the time interval to include the start of the waveform complex and the end of the widest expected waveform complex.

7. Apparatus for monitoring recurrent waveforms to detect abnormal waveform complexes in said recurrent waveform comprising means for sensing the recurrent waveform, means for integrating and storing segments of normal waveform complex for use as a reference, means for integrating successive segments of a waveform complex to be compared, means for determing the difference between the integrated value of each segment and that of the corresponding segment of the normal complex, means for adding the magnitudes of said differences irrespective of sign to determine the resultant difference, and means for indicating whether the magnitude of said resulting difference indicates an abnormal complex.

8. Apparatus according to claim 7 including a trigger section for deriving, from the recurrent waveform, timing signals which represent the time location of particular selected parts of the waveform complexes required to be compared with corresponding parts of the stored normal complex, means for sampling the waveform immediately before the start of each complex and deriving a reference voltage level, and means for superimposing each waveform complex, by the aid of said timing signals and said reference voltage level, upon the stored reference waveform.

9. Apparatus according to claim 8, wherein said trigger section includes means for differentiating each waveform complex twice to obtain peak signals representing the approximate time location of the particular part of the waveform complex selected for comparison, means for blanking out another version of said second derivative signals during the periods thus established as including the peaks to obtain a threshold level representative of the remainder of the complex plus noise, each part of each individual waveform complex to be compared having a start and a centre, and means for comparing the original unblanked second derivative signals with said threshold level, means responsive to said comparing for generating a master timing pulse in determined relation to the start of that part of each individual waveform complex which is to be compared with the stored reference waveform and further means responsive to said comparing for generating a master trigger pulse having a determined time relation to the center of said part of the waveform complex.

10. Apparatus according to claim 9, including a delay line through which the recurrent waveform is fed to said trigger section.

11. Apparatus according to claim 7, wherein the means for storing and integrating the normal waveform complex and the means for integrating the waveform complex to be compared include an operational section having operational amplifiers wherein the segments of the stored reference waveform complex and the superimposed waveform complex to be compared with it are successively integrated by the operational amplifiers, and including also a trigger section for generating master timing pulses and master trigger pulses from said recurrent waveform, control means for delivering a sequence of command pulses under the control of the master timing pulses and the master trigger pulses, and means for feeding said command pulses successively to the operational section.

12. Apparatus according to claim 11, wherein the operational section includes amplifier stages comprising said means for determining the difference between the integrated value of each segment of the waveform complex and the corresponding integrated segment of the stored reference waveform, said operational section including said means for adding the magnitudes of said individual differences and means for causing said adding to take place over a time including the start of the waveform complex and the end of the widest expected waveform complex.

13. Apparatus according to claim 11 including a logic section and means connecting same to said operational section for receiving from the operational section an output signal representing '"'"''"'"''"'"''"'"'abnormal shape'"'"''"'"''"'"''"'"' or '"'"''"'"''"'"''"'"'normal shape'"'"''"'"''"'"''"'"' in dependence upon the comparison results of said operational section, said logic section including means for delivering a command pulse in response to a '"'"''"'"''"'"''"'"'normal shape'"'"''"'"''"'"''"'"' signal, said operational section including sample/hold stages, means for feeding said command pulse to said sample/hold stages for causing said stages to sample the values of the waveform complex being held in said operational section.

14. Apparatus according to claim 11 including inhibit means for inhibiting all outputs from the apparatus when the sensed recurrent waveform is degraded by noise to a level severe enough to disturb correct analysis, said inhibit means including means for delivering a warning pulse and an inhibit pulse of such duration and timing as at least to cover the time elapsing between the sensing of the degraded portion of the recurrent waveform up to the completion of the integration and comparison with the stored reference complex.