WO1980000006A1 - Appareil de diagnostic - Google Patents

Appareil de diagnostic Download PDF

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Publication number
WO1980000006A1
WO1980000006A1 PCT/GB1979/000094 GB7900094W WO8000006A1 WO 1980000006 A1 WO1980000006 A1 WO 1980000006A1 GB 7900094 W GB7900094 W GB 7900094W WO 8000006 A1 WO8000006 A1 WO 8000006A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
circuit
electrodes
buffer
automatic gain
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1979/000094
Other languages
English (en)
Inventor
J Anderson
J Pantridge
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of WO1980000006A1 publication Critical patent/WO1980000006A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/18—Applying electric currents by contact electrodes
    • A61N1/32—Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/38—Applying electric currents by contact electrodes alternating or intermittent currents for producing shock effects
    • A61N1/39—Heart defibrillators
    • A61N1/3904—External heart defibrillators [EHD]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/318—Heart-related electrical modalities, e.g. electrocardiography [ECG]
    • A61B5/346—Analysis of electrocardiograms
    • A61B5/349—Detecting specific parameters of the electrocardiograph cycle
    • A61B5/361—Detecting fibrillation

Definitions

  • This invention relates to diagnosis of heart conditions which may require defibrillation.
  • Ventricular fibrillation very often occurs during a coronary/heart attack and is commonly fatal unless treatment is applied very rapidly. Ventricular fibrillation is a condition in which the heart has ceased to pump or has spasmodically irregular contractions, accompanied by chaotic electrical activity.
  • This condition can be treated by defibrillation, i.e. by applying a controlled electric shock to the patient, normally through electrodes applied to the chest.
  • defibrillator of the type described in our British Patents 1,435,709 and 1,481,469.
  • an electrocardiograph in which the electrical activity of the heart is monitored through electrodes attached to the body and the electric pulses displayed on a cathode ray tube or equivalent device.
  • Accurate interpretation of the signals obtained with an electrocardiograph requires considerable medical training. However in the event of a heart attack it is not always possible to summon a doctor before defibrillation treatment has to be applied. Diagnosis and treatment of the patient's condition then has to be carried out by paramedical or other personnel who may not be fully qualified medically.
  • the present invention is intended to provide diagnostic apparatus which is capable of detecting fibrillation in a patient automatically without the need for an operator to interpret the data received by the apparatus.
  • the present invention is intended to provide apparatus for detecting ventricular fibrillation, comprising a pair of electrodes capable of being put in electrical contact with the body of a patient (normally the patient's chest), a circuit capable of distinguishing a signal received from the electrodes characteristic of ventricular fibrillation from signals characteristic of other heart conditions, and indicating means to indicate to an operator when said signal is characteristic of ventricular fibrillation.
  • the electric signal received from the heart during normal operation by electrodes positioned on the chest is shown in the accompanying Figure 1, in which the voltage is plotted on the y -axis and time on the x—axis. This condition is known as the Sinus Rhythm.
  • Ventricular fibrillation is characterised by a disordered trace of the kind shown in Figure 2, plotted in the same manner as in Figure 1.
  • advantage is taken of the different energy contained in the signals of Figures 1 and 2 when they are amplified to the same amplitude.
  • advantage is taken of the fact that the signal generated by ventricular fibrillation is essentially continuous and free from regular peaks (as shown in Figure 2) whereas an ordinary Sinus Rhythm shows regular peaks ( Figure 1).
  • This allows use of an analogue switch to actuate the indicating means and circuit means connected to the analogue switch to allow it to operate only when a continuous signal substantially free from peaks characteristic of ventricular fibrillation is fed to the analogue switch.
  • the positive and negative components of the signal from the electrodes are summed, i.e. the polarity of one of these components is reversed and its magnitude is added to the other.
  • the summed signal is then passed to an automatic gain chip where it may be amplified and successively through a buffer amplifier and peak detector to the analogue switch.
  • the summed signal may be split and the split signals passed respectively to a buffer and to a peak signal capacitor decay circuit and buffer.
  • the outputs from these units are passed to a comparator which is connected to an automatic gain control unit provided with a direct-current pump with decay to the automatic gain control chip.
  • the comparator is such that it emits a substantially continuous output when the signals it receives represent ventricular fibrillation but emits a pulsed output when the signals it receives show the peaks obtained from Sinus Rhythm.
  • This pulsed output fed to the automatic gain control will prevent the automatic gain chip passing an amplified signal to the peak detector and hence the analogue switch: thus no amplified signal is passed when the comparator detects the presence of peaks in the original signal.
  • the outputs from the peak signal capacitor decay circuit and the buffer may also be fed to an event comparator provided with a direct current pump with decay connected to the analogue switch through an OR gate.
  • the event comparator is arranged such that if a significant number of pulses representing peaks in the original signal is received it generates no output and the analogue switch is closed. Thus the event comparator emits an output allowing the summed signal to pass the analogue switch only when the original signal represents ventricular fibrillation. Provision may also be made to eliminate the effect short bursts of noise or other extraneous signals which may affect the circuit. This may be done by connecting a reset unit, emitting a reset signal at short intervals such as 3 seconds, to a direct current pump and buffer through which the output from the analogue switch is passed.
  • the diagnostic unit may be self-contained, battery operated and by use of microcircuits wherever possible it may be made small and highly portable. It may be incorporated in the same unit as a defibrillator and may use the same electrodes as the defibrillator, with a relay or other device to isolate the diagnosis unit from the electrodes when a defibrillation shock is administered. With this arrangement the operation of a patient's heart may be diagnosed and if defibrillation is required it can be administered immediately through the same electrodes.
  • the indicating device may comprise any visual or acoustic indicating device to inform the operator that defibrillation is required.
  • This device may be much smaller and simpler than the display system, generally a cathode ray tube, which is required by conventional electrocardiographs.
  • Figure 1 shows an oscilloscope trace showing the normal Sinus Rhythm from a patient's heart
  • Figure 1a shows the same trace after automatic gain amplification and clipping
  • Figure 2 shows a similar trace of a signal received on ventricular fibrillation
  • Figure 2a shows the trace of Figure 2' after automatic gain amplification and clipping
  • Figure 3 shows a trace of a signal received on ventricular tachycardia
  • Figure 3a shows the trace of Figure 3 after automatic gain amplification and clipping
  • Figure 4 is a schematic circuit diagram of diagnostic apparatus according to one embodiment of the invention
  • Figure 5 is a schematic circuit diagram of diagnostic apparatus according to another embodiment of the invention.
  • the various block components may be standard components known in the electronics and computer arts and so will not be described in detail.
  • the defibrillator part of the apparatus comprises electrodes 1 and 2 arranged to be placed in electrical contact with the body of a patient and connected in series with a choke 3 and capacitor 4 by relay-operated switches 5 and 6.
  • Capacitor 4 may be charged to a high voltage by means of a high voltage source 7 powered by an oscillator 8.
  • the operation of this part of the apparatus is controlled by circuitry assembled as a hybrid package 9.
  • the defibrillator part may be functionally the same as those described in British Patents 1,481,469 and 1,435,709.
  • Electrodes 1 and 2 are also connected to leads 10 and 11 connected to the diagnostic part of the apparatus.
  • This comprises an amplifier 12 in which the electric signals received by the electrodes from the patient are amplified to about 1 volt.
  • the amplified signals are then sent to an automatic gain control unit 13 which is set to produce an output between the same positive and negative set levels regardless of whether the signals received represent Sinus Rhythm or ventricular fibrillation: the automatic gain control unit is tuned so that the automatic gain is selective for the frequencies obtained from Sinus Rhythm and from defibrillation.
  • the output from the automatic gain control is then fed to positive and negative clipping circuits 14 which remove the positive and negative peaks of the output from the automatic gain control.
  • the clipped outputs are fed to respective integrator and reset circuits 15 which integrate the outputs for about 3 seconds at a time.
  • the outputs from the integrators are then fed to a dual comparator unit in which they are compared and their magnitudes measured.
  • the comparator unit is provided with a system of AND gates such that a signal is emitted if the absolute magnitudes of the integrated signals, and the relationship between these magnitudes, indicate fibrillation. This signal actuates a visual indicating device 17 which indicates to the operator that defibrillation is required.
  • a defibrillation shock can then be administered to the patient immediately through electrodes 1 and 2 which remain in contact with the patient.
  • Apparatus according to another embodiment of the invention will be described with reference to Figure 5.
  • the electrodes to be in contact with the patient are connected to a notch filter 1 in order to remove any interfering signal derived from the electric mains: this filter will remove 50 Hz components in countries where this frequency is used for the public electricity supply.
  • the signals passing filter 21 and then passed through the band pass filter 22 which passes only frequencies from 2 to 17 Hz: these are the main frequency components obtained from the ventricular fibrillation condition and the central frequencies obtained with a normal Sinus Rhythm from the heart.
  • the output from filter 22 is then fed to a unit which carries out negative summing of both the positive and negative components of the signal.
  • This unit comprises a buffer amplifier 23 and an inverting buffer 24, connected as shown with diodes 25 to give a negative summed signal at point 26. If the original signal represents the QRS complex obtained from normal heart operation the summed signal contains pronounced peaks corresponding to the peaks of the complex: if the signal received represents ventricular fibrillation the summed signal is much more uniform and does not contain such pronounced peaks.
  • the summed signal is passed to automatic gain control chip 27. Chip 27 is controlled by further circuitry described below.
  • the signal may then be passed to buffer amplifier 28, peak detector 29 and analogue switch 30.
  • Analogue switch 30 is arranged to actuate a visible or acoustic indicating means to indicate to an observer the existence of ventricular fibrillation in the patient. This indicating means may be of a conventional type and so will not be described.
  • the summed signal from point 26 is also fed by signal splitting device 31 to a buffer 32 and a peak signal capacitor decay circuit and buffer 33 to a comparator 34, which is itself connected to an automatic gain control unit 35 having a direct-current pump with decay associated with the automatic gain control chip 27.
  • Comparator 34 is arranged so as to generate a substantially continuous output when the summed signal received represents ventricular fibrillation but produces pulses corresponding to the Sinus Rhythm peaks when a normal Sinus Rhythm signal is received.
  • the Sinus Rhythm pulses are fed to the control unit 35, which is arranged such that it prevents the signal received by chip 27 from point 26 being passed through the automatic gain when a summed signal displaying peaks is received.
  • the outputs from units 32 and 33 are fed to an event comparator with a direct current pump with decay 36 and thence to an OR gate 37 which is itself connected to analogue switch 30.
  • the event comparator is arranged to give an output to the OR gate only when the signal received represents ventricular fibrillation.
  • the analogue switch 30 is opened on receipt of the output through the OR gate allowing the signal from peak detector 29 to pass through.
  • the analogue switch 30 is provided with an additional direct-current pump and buffer 38 connected to a reset device 39 and a unit 40 generating a 3-second interval reset signal. The purpose of this arrangement is to eliminate the effect of "short" bursts of noise or other signal not derived from the patient which may find its way through the circuit to this point.
  • the analogue switch 30 is controlled by the event comparator 36. When the number of pulses in the signal received reaches a certain number the pumping action of unit 36 is sufficient to operate the analogue switch to prevent any signal from peak detector 29 being passed.
  • the reset arrangement 39 and 40 resets the pump and buffer 38 at 3-second intervals, thus preventing any stray signals received by the circuit affecting the output for more than a very short period.
  • the effect of this arrangement is to block signals received from the heart which do not show the characteristics of fibrillation while allowing a fibrillation signal to operate a fibrillation indicator.
  • the apparatus shown in Figure 5 may be incorporated in self-contained apparatus including a defibrillator, as in the embodiment of Figure 4.

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  • Health & Medical Sciences (AREA)
  • Cardiology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Veterinary Medicine (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Public Health (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Physics & Mathematics (AREA)
  • Biophysics (AREA)
  • Medical Informatics (AREA)
  • Pathology (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Electrotherapy Devices (AREA)

Abstract

Un appareil pour le diagnostic de la fibrillation ventriculaire chez un patient comprend une paire d'electrodes (1, 2) placees en contact avec un patient et connectees a un circuit (16) pour distinguer le signal recu caracteristique des fibrillations, ainsi qu'un indicateur (17) qui est actionne a la reception d'un tel signal. Un signal de fibrillation peut etre distingue soit par observation de sa capacite energetique apres amplification de gain automatique soit par son traitement pour en detecter les cretes presentes dans les signaux representant d'autres conditions cardiaques.
PCT/GB1979/000094 1978-06-02 1979-06-01 Appareil de diagnostic Ceased WO1980000006A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB7826304 1978-06-02
GB7826304 1978-06-02

Publications (1)

Publication Number Publication Date
WO1980000006A1 true WO1980000006A1 (fr) 1980-01-10

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ID=10497845

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1979/000094 Ceased WO1980000006A1 (fr) 1978-06-02 1979-06-01 Appareil de diagnostic

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WO (1) WO1980000006A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2626164A1 (fr) * 1988-01-26 1989-07-28 Gorny Philippe Procede et dispositif de detection d'anomalies de l'activite cardiaque

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2362070A1 (de) * 1973-12-13 1975-06-19 Siemens Ag Vorrichtung zum erfassen bzw. verarbeiten elektrischer signale
US3950694A (en) * 1973-12-13 1976-04-13 Siemens Aktiengesellschaft Installation for the detection and processing of electrical signals
US3968430A (en) * 1973-12-13 1976-07-06 Siemens Aktiengesellschaft Installation for the detection and processing of electrical signals
DE2643907A1 (de) * 1975-09-30 1977-04-07 Mieczyslaw Mirowski System zum anzeigen von herzzustaenden

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2362070A1 (de) * 1973-12-13 1975-06-19 Siemens Ag Vorrichtung zum erfassen bzw. verarbeiten elektrischer signale
US3950694A (en) * 1973-12-13 1976-04-13 Siemens Aktiengesellschaft Installation for the detection and processing of electrical signals
US3968430A (en) * 1973-12-13 1976-07-06 Siemens Aktiengesellschaft Installation for the detection and processing of electrical signals
DE2643907A1 (de) * 1975-09-30 1977-04-07 Mieczyslaw Mirowski System zum anzeigen von herzzustaenden

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2626164A1 (fr) * 1988-01-26 1989-07-28 Gorny Philippe Procede et dispositif de detection d'anomalies de l'activite cardiaque
EP0327427A1 (fr) * 1988-01-26 1989-08-09 Philippe Gorny Procédé et dispositif de détection d'anomalies de l'activité cardiaque

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