WO2013144229A1 - Dispositif et procédé de mesure de potentiels électriques d'un être vivant - Google Patents

Dispositif et procédé de mesure de potentiels électriques d'un être vivant Download PDF

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Publication number
WO2013144229A1
WO2013144229A1 PCT/EP2013/056567 EP2013056567W WO2013144229A1 WO 2013144229 A1 WO2013144229 A1 WO 2013144229A1 EP 2013056567 W EP2013056567 W EP 2013056567W WO 2013144229 A1 WO2013144229 A1 WO 2013144229A1
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Prior art keywords
signal
frequency
electrodes
bandpass filter
signal output
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PCT/EP2013/056567
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German (de)
English (en)
Inventor
Jürgen Gross
Rudolf Mauser
Original Assignee
Gross Juergen
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Priority to EP13715638.6A priority Critical patent/EP2830493A1/fr
Publication of WO2013144229A1 publication Critical patent/WO2013144229A1/fr

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Classifications

    • 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
    • A61B5/30—Input circuits therefor
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/16—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state
    • A61B5/18—Devices for psychotechnics; Testing reaction times ; Devices for evaluating the psychological state for vehicle drivers or machine operators
    • 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
    • A61B5/369—Electroencephalography [EEG]
    • A61B5/372—Analysis of electroencephalograms
    • A61B5/374—Detecting the frequency distribution of signals, e.g. detecting delta, theta, alpha, beta or gamma waves
    • 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
    • A61B5/389—Electromyography [EMG]
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/48—Other medical applications
    • A61B5/4806—Sleep evaluation
    • A61B5/4809—Sleep detection, i.e. determining whether a subject is asleep or not
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/48—Other medical applications
    • A61B5/4821—Determining level or depth of anaesthesia
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/74—Details of notification to user or communication with user or patient ; user input means
    • A61B5/746—Alarms related to a physiological condition, e.g. details of setting alarm thresholds or avoiding false alarms

Definitions

  • the present invention relates to a device for measuring electrical potentials of a living with at least two electrodes suitable for the derivation of electrical potentials of a living organism, an electrically connected to the electrodes isolation amplifier and an electrically connected to the isolation amplifier signal output, the isolation amplifier and the signal output set up are that in operation of the device of the isolation amplifier amplifies the signal coming from the electrodes and the amplified signal can be tapped at the signal output.
  • the present invention further relates to a method for measuring electrical potentials of a living being.
  • the present invention further relates to an apparatus and method for the early detection of imminent microsurft attacks, and to an apparatus and method for monitoring anesthetized patients, both of which may have the aforementioned features of the apparatus.
  • Electroencephalographic signals are used to visualize brain waves and reflect the state of excitement of brain cells.
  • electroencephalographic signals up to 256 electrodes, usually up to 128 electrodes, are arranged at predetermined positions on the skull surface. Through the skullcap, only those potentials can be detected that reach sufficient size and size as a result of the synchronous activity of numerous nerve cells on the surface of the brain.
  • a finite electrical resistance of the biological structures involved weakenings and distortions of the potentials on the skull occur.
  • a contact agent for example sodium chloride, can be applied to the contact surface of the electrodes.
  • the quasi-periodic signal thus derived contains a plurality of frequencies which are superimposed.
  • the amplitudes of the derived signals can reach up to several 10 ⁇ .
  • EEG electroencephalography
  • the EEG signals are subjected to a fast Fourier transformation in a defined period of time for the calculation of an EEG power spectrum.
  • a fast Fourier transform breaks the electroencephalographic signals into the individual frequency components that overlap the signal. The relative shares of the original signal are calculated. The squared amplitudes of the individual frequency components form the EEG power spectrum.
  • all frequencies occurring in the time domain signal are readable.
  • the use of a fast Fourier transformation has the disadvantage that due to the finite measurement signal, only individual finite signal sections can be analyzed by means of the fast Fourier transformation. A real-time assessment of the measured brain waves is therefore not possible. In addition, it is very costly to place the large number of required electrodes on the skull or the brain surface exactly.
  • the electrodes arranged on the skullcap or brain surface also limit the freedom of movement of the patients as well as of the care staff and thus also the possible fields of application.
  • the number of necessary electrodes should be reduced.
  • a real-time evaluation is also an attainable goal.
  • the term living organism is understood to mean a warm-blooded animal, preferably a humanoid, but at least a primate.
  • At least one of the aforementioned objects is achieved by a device with the aforementioned features, wherein according to the invention at least one bandpass filter and at least one integrator are connected between the isolation amplifier and the signal output, wherein the bandpass filter and the integrator are set up in such a way that during operation Device the bandpass filter passes a predetermined frequency range of the signal and the integrator integrates the filtered signal, wherein the integrated signal can be tapped at the signal output.
  • the bandpass filter, the integrator and the signal output together form a frequency channel.
  • the device and method according to the present invention are particularly useful for the derivation of electroencephalographic signals, i. the electrical potentials of the brain, are provided and will be described in the text below mainly with regard to this application.
  • the device and the method are basically also suitable for detecting electrical potentials of other parts of the body, for example electromyographic potentials (EMG) due to muscle activities.
  • EMG electromyographic potentials
  • the derived signal usually contains several overlapping frequency components which are divided into several frequency bands. In this case, the consideration of the signal components of each individual frequency band can provide information about different brain activities.
  • the electroencephalographic signal is derived from the at least two electrodes and amplified with an isolation amplifier electrically connected to the electrodes.
  • the isolation amplifier also causes the electrodes to be galvanically isolated from the supply voltage such that during operation of the device there is no danger to the subject connected to the electrodes.
  • At least one bandpass filter which filters the electroencephalographic signal, is electrically connected to the isolation amplifier.
  • the filtering a predetermined frequency range of the signal is transmitted during operation of the device, which then passes into the integrating element which is electrically connected to the bandpass filter, where the filtered signal is imprinted.
  • the signal amplitudes of the selected frequency band are added up within a predetermined integration interval, so that a temporal sequence of integral frequencies is added.
  • the temporal sequence of integration values can be tapped in the operation of the device as an output signal at the signal output of the device. On the basis of the output signal, the respective excitation state of the detected brain areas can be detected in real time during operation of the device.
  • the bandpass filter, the integrator and the signal output together form a frequency channel with a passband defined by the bandpass filter and a defined bandwidth.
  • the bandpass filter comprises two low-pass filters and two high-pass filters. These are preferably connected in succession in the order of the first low-pass filter, the second low-pass filter, the first high-pass filter, the second high-pass filter, and their parameters are expediently adjustable.
  • the low and high pass filters used for the bandpass filter have an attenuation of -36 dB / octave each. If several low-pass and high-pass filters are connected in series, it is advantageously possible to provide filters of a higher order in order to improve the slope and quality of the band-pass filtering.
  • the ⁇ -frequency band has an average frequency of 10 Hz
  • the ⁇ -frequency band has an average frequency of 20 Hz
  • the ⁇ -frequency band has an average frequency of 3 Hz
  • the ⁇ -frequency band has an average frequency of 6 Hz
  • Signals in these four frequency bands can be attributed to the excitation states of the brain waves of psychological and / or physiological causes, such as an eyelid movement, excitement, fatigue or concentration.
  • a fifth frequency channel is provided for providing a fifth frequency band 5 SUb , wherein preferably the 5 SUb frequency band comprises the frequency range from 0.05 Hz to 2 Hz, preferably the frequency range from 0.05 Hz to 0.5 Hz having.
  • the device has exactly five frequency channels with the frequency bands a, ß, ⁇ , ⁇ , 5 sub .
  • Each of the frequency channels comprises at least one bandpass filter, an integrator and a signal output, on which the filtered and integrated signal can be tapped off.
  • each of the frequency channels next to the bandpass filter, the integrator and the signal output have further electrical components.
  • the integrated signal it is expedient for the integrated signal to be able to be tapped at the signal output of the device in such a way that it can be further processed by any signal processing device and / or can be displayed visually and / or acoustically with the aid of a suitable display device.
  • a screen and / or a printer can be connected to the signal output for this purpose.
  • electrically connected in the sense of the present invention is to be understood as meaning that both a direct electrical connection of two electrical components and an indirect connection of two electrical components are included.
  • the integration interval indicates the period of time over which the amplitude of the signal fed into the integrator is added up.
  • the integrated signal is forwarded to the signal output as a time-dependent signal.
  • the integration interval the greater the temporal resolution of the signal and the more the integrated signal approaches a representation of the unintegrated raw signal.
  • the integration interval can not be chosen to be arbitrarily small. Also, if the integration interval is too small, the influence of possible noise components in the signal comes to the fore.
  • each frequency channel comprises a rectifier, preferably a full-wave rectifier, which is arranged in front of the interposer, preferably between the bandpass filter and the integrator.
  • the signal derived from the electrodes is an AC voltage signal.
  • the rectifier now ensures that the positive and negative contributions of the AC signal during integration are not compensated.
  • the frequencies of interest of the brain waves are application specific in a range of 0.05 Hz to 200 Hz, so that in one embodiment of the invention, another bandpass filter is provided before the frequency channel or the plurality of frequency channels.
  • This bandpass filter limits the voltage applied between the isolation amplifier and the signal output electroencephalographic signal to a frequency range of 0.05 Hz to 200 Hz, preferably 0.05 Hz to 100 Hz and more preferably from 0.5 Hz to 42 Hz
  • Another embodiment may be advantageous if the filter is a bandpass filter, the passband is adjustable.
  • the device it is expedient for the device to have a notch filter with a blocking frequency at the mains frequency of the low-voltage power supply network, preferably at 50 Hz (Europe) or 60 Hz (North America) in front of the one frequency channel or the plurality of frequency channels, in order to filter out the network frequency.
  • a comparator is provided which determines the input resistance of the electrodes and which, when the electrical resistance of one of the electrodes is more than 1 k ⁇ , outputs a signal which indicates a malfunction of the electrode.
  • the comparator is preferably present the frequency channel or the plurality of frequency channels arranged. Inaccurate measurements due to poor contact with the electrodes can be avoided.
  • the order of amplification and frequency-selective filtering can be reversed without departing from the essential idea of the invention.
  • the same applies if several amplifiers are combined to form an amplifier with a correspondingly adapted amplification factor or if a single amplifier is divided among a plurality of amplifiers.
  • a bandpass filter having two low-pass and high-pass filters connected in series, their order can be reversed without departing from the essential concept of the invention.
  • two or more low-pass filters may be combined into a first filter and two or more high-pass filters combined into a second filter. Accordingly, individual filters can also be replaced by a plurality of filters.
  • the device can also be used to measure other cell potentials, so the device can be used in particular for the preparation of an electrocardiogram or electromyogram. For this, if necessary, only the number of electrodes and their placement must be adjusted.
  • the parameters used for filtering the signals can also be set to the frequencies to be expected for such an application.
  • the device for measuring electroencephalographic signals has at least two electrodes suitable for measuring electroencephalographic signals and at least two electrodes suitable for measuring electromyographic signals.
  • the electrodes suitable for the measurement of electromyographic signals are connected at least to a frequency channel whose structure corresponds to that of a frequency channel, as previously described in detail for the electroencephalographic signal. It is understood that electroencephalographic and electromyographic signals may differ in amplitude and frequency, so that the parameters of the electronic components of the at least one intended for electromyographic signals frequency channel are adjusted accordingly.
  • the device has an intermediate tap, which is arranged in front of the at least one frequency channel and at which the unfiltered and non-integrated raw signal can be tapped.
  • the raw signal can thus be directed to further devices for further processing and / or evaluation.
  • an intermediate tap is provided which makes it possible to tap and display the filtered but not yet integrated signal in a frequency channel.
  • At least one of the above-mentioned objects is also achieved by a method for measuring electrical potentials of a living being with the steps of deriving electrical potentials of a living being with at least two electrodes and providing a measurement signal, amplifying the measurement signal with an isolation amplifier, filtering out a frequency band of interest Measuring signal with a bandpass filter, integrating the filtered signal with an integrator and providing the integrated signal at a signal output.
  • a device for the early detection of microsleep attacks, a device is provided according to the invention which, in addition to the previously described necessary and optional features of the device for measuring electrical potentials of a living being, has a signal generator which generates a provocation signal perceptible to the subject. Such a signal that can be perceived by the subject may be perceptible in particular visually, acoustically and / or haptically.
  • the device for the early detection of microsatisfaction attacks works particularly advantageously with a device for measuring electrical potentials of a living being, as described above, i. with an integration of the frequency-filtered derivative signal
  • the device for early detection of microsleep attacks can also be implemented with other and in particular with conventional embodiments of EEG devices.
  • a device for measuring electrical potentials of a living being with at least two electrodes for the derivation of electrical potentials of the living being, wherein the electrodes are connected to an EEG device and wherein the device has a signal generator which generates a provocation signal perceptible for the subject.
  • the EEG device has no frequency channel with a bandpass filter and an integrator in the frequency channel.
  • a Fourier transformer may be provided which divides the signal into its frequency components, so as to correlate the phase and / or frequency of the derived signal to enable the provocation signal.
  • the signal generator is a visually perceptible light source, preferably a light emitting diode, which is alternately “on” and “off” in accordance with a predetermined frequency.
  • the light emitting area of the transmitter has an area greater than 75 mm 2 .
  • a light source is used as the signal generator, it is expedient in one embodiment if interference caused by ambient light is reduced by arranging a tunnel with its opening pointing in the direction of the subject around the light source. Such a tunnel shields the light source from ambient light, so that the test person perceives essentially only the provocation signal when looking into the tunnel.
  • the provocation signal provokes an excitation state such that the electroencephalographic signals derived from the involved brain areas are corresponding to the provocation signal. If, on the other hand, the provocation signal is no longer perceived by the subject due to a threatening secondary sleep attack, the derived electroencephalographic signals show no significance. The provocation signal then triggers no more arousal state. Based on the presence and / or absence of a state of excitement can thus be concluded on the state of consciousness and / or the attention of the subject.
  • a signal driver connected to the signal generator is provided which, in accordance with a predetermined and preferably adjustable switching sequence, triggers a plurality of provocation signals with different frequencies one after the other.
  • the signal driver and the signal generator are set up such that during operation of the device, provocation signals with a descending frequency of 40 Hz, 35 Hz, 30 Hz and 25 Hz are transmitted in succession from the transmitter.
  • rest periods may additionally be provided between the emission of the provocation signals with mutually different frequencies in which no provocation signal is transmitted.
  • the rest periods have a duration in the range of 10 seconds to 30 seconds.
  • the device has a correlation detector which carries out a correlation between the emitted provocation signal and the detected electroencephalographic signal.
  • the correlation detector triggers a warning signal when it exceeds or falls below a predetermined limit value in the integrated output signal, preferably in haptic, optical and / or acoustic form.
  • the integrated output signal is in correlation with the provocation signal above a predetermined threshold value, then in one embodiment the provocation is repeated at predetermined and preferably adjustable time intervals.
  • the evaluation is based on a plurality of predetermined frequency bands.
  • At least one of the aforementioned objects is also achieved by a method for the early detection of microsatisfaction attacks with the steps of providing a provocation signal perceptible to the subject and emitting the provocation signal with a transmitter, deriving electrical potentials of the subject with at least two electrodes, providing a measurement signal, Amplifying the measurement signal with an isolation amplifier, filtering out at least one frequency band of interest from the measurement signal, comparing the measurement signal with at least one predetermined limit value and outputting a warning signal if the measurement signal deviates from the predetermined limit value by a predetermined value.
  • the frequency band of interest is filtered out using a bandpass filter, and the filtered signal is integrated with an integrator.
  • An embodiment of the method for the early detection of microsleep attacks further comprises the steps of providing a plurality of provocative measures perceptible to the subject. ondsignalen with decreasing frequency, wherein if the comparison of the integrated signal with at least one predetermined limit value does not detect a deviation by a predetermined value, the perceptible for the subject provocation signal of the next lower frequency is transmitted with a transmitter.
  • Both the device for the early detection of microsatisfies and the method for the guidance detection of microsleep attacks are advantageously suitable for aiding a vehicle and / or machine operator in order to avoid accidents or the like due to microsleep attacks and / or attention deficits.
  • the excitation state of the brain areas of interest is measured independently of a provocation signal with the device for measuring electrical potentials and compared with predetermined limit values.
  • a device for monitoring anesthetized patients, which, in addition to the previously described necessary and optional features of the device for measuring electrical potentials of a living being, has a device for measuring its terminal blood flow velocity.
  • the velocity of the blood in the terminal blood vessels i. the blood vessels close to the body surface in the periphery of the body understood.
  • a device can be used to determine the blood flow velocity of terminal blood vessels of extremities, the so-called "acres".
  • the actual blood flow rate may be determined by means of high-frequency ultrasound, i. Ultrasound with frequencies in the MHz range, preferably in the range of 10 MHz to 16 MHz, in certain cases also above, or laser Dopplerflowmetrie, each be determined by utilizing the Doppler effect.
  • electromagnetic waves having a wavelength in the range from 600 nm to 900 nm, preferably at wavelengths of 633 nm, 520 nm and / or 805 nm.
  • the Doppler effect, laser and / or ultrasound-determined frequency shift ⁇ is a measure of blood flow velocity, with changes in blood flow velocity indicative of the patient's depth of anesthesia, thus helping to monitor the anaesthetized patient. As the depth of anesthesia decreases, so does the determined frequency shift ⁇ .
  • the determined frequency shift ⁇ is preferably in a range from 0.1 Hz to 2000 Hz and can be converted into a speed value with the device for measuring the terminal blood flow velocity.
  • the converted velocity value corresponds to the average erythrocyte velocity in the respective terminal blood vessel, wherein the velocity value can preferably be tapped off as an amplitude-normalized voltage signal with respect to time at an output of the device for measuring the terminal blood flow velocity.
  • a change in the voltage signal of 1 mV corresponds to a change of 1 Hz in the frequency domain.
  • the isolation amplifier and the signal output exactly four, preferably exactly five, frequency channels for providing the integrated signals corresponding to the ⁇ -, ß-, ⁇ -, ⁇ - frequency bands, and at five frequency channels corresponding to the ⁇ -, ß, ⁇ -, ⁇ -, 5 S UB frequency bands, are connected, wherein for amplifying said integrated signals the output of each frequency channel, each with an amplifier, and for adding said integrated and amplified signals, each amplifier electrically connected to a summing amplifier. are so that in operation of the device at an output of the summing a sum signal of the four, preferably the five, integrated and amplified signals can be tapped.
  • a signal processing device and / or a display device for processing and / or displaying both the sum signal and the time course of the blood flow velocity.
  • both the time course of the sum signal and the time course of the blood flow velocity can be compared graphically on a screen.
  • the sum signal and the signal of the blood flow velocity can be compared with a comparator which is electrically connected to the device, wherein the comparator, in operation, determines a difference between the sum signal and the blood flow velocity which exceeds a predetermined limit value. and / or falls below an alarm signal.
  • the comparator is electrically connected thereto with an alarm.
  • a limit value a plurality of limit values, for example a lower and an upper limit value can be used if required.
  • a first display is provided for displaying, preferably for separate presentation, the voltage signals from the ⁇ , ⁇ , ⁇ frequency bands applied to the signal output and a second display for displaying, preferably separate, the sum signal and the blood flow rate.
  • the first display may be a first monitor and the second display may be a second monitor.
  • the first display may be a first Graphical User Interface (GUI) and the second display may be a second graphical window (GUI) of a common monitor.
  • GUI Graphical User Interface
  • GUI second graphical window
  • the voltage signal of the ⁇ and / or 5 SUb frequency band applied to the signal output can additionally be represented in the first display.
  • the described embodiments may be implemented with one or more of the above-described features of the device for measuring electrical potentials of a Living and / or the device for monitoring anesthetized patients can be supplemented. Where necessary, the respective signals for display and / or further processing can be inverted to compensate for any circuit-related sign changes.
  • the device for monitoring anesthetized patients is particularly advantageous with a device for measuring electrical potentials of a living being, as described above, ie with an integration of the frequency-filtered derivative signal, the device for monitoring anesthetized patients with other embodiments of EEG devices be realized, which preferably dispense with a bandpass filter and an integrator in the frequency channel.
  • a Fourier transformer for example, can be provided for evaluating the derived electroencephalographic signal, which divides the signal into its frequency components so as to enable evaluation of the phase and / or frequency of the derived signal for monitoring anesthetized patients.
  • a device for measuring electrical potentials of a living being with at least two electrodes for the derivation of electrical potentials of the living being, wherein the electrodes are connected to an EEG device and wherein the device has a device for measuring the terminal blood flow velocity.
  • a device for measuring electroencephalographic potentials with only a single frequency channel is used.
  • the bandpass filter is set up in particular such that frequencies in the range from 0.05 Hz to 2 Hz, preferably frequencies in the range from 0.05 Hz to 0.5 Hz, can be picked up at the signal output.
  • These frequencies referred to as the 5- SUb frequency band, can be used in the operation of the device as an indicator of the oxygen supply to the brain, with a decrease in the amplitude and / or frequency of the SUb signal starting from a decrease in the oxygen supply of the brain.
  • the device for monitoring anesthetized patients additionally has an electromyograph which records an electromyogram of the facial musculature and / or the forearm musculature. Muscle activities that may indicate insufficient depth of anesthesia can be determined using the electromyogram.
  • the device for monitoring anesthetized patients has an evaluation unit, which with the integrator or the EEG device of the device for measuring the electroencephalographic potentials, the means for measuring the blood flow velocity and optionally the electromyographies is electrically connected and is set up so that during operation of the device, the voltage applied to the signal output electroencephalographic signal, the Blutströmungsgeschwindig- keitssignal and optionally the Elektromyographiesignal with each is comparable to a predetermined limit and an alarm signal is triggered at a predetermined deviations of all three signals from their respective limit. If all three signals deviate by a predetermined value from their respectively predetermined limit value, this is an indication of a non-optimal anesthetic guide.
  • Non-optimized anesthesia may indicate too high as well as too low a dose medication in the pre- and / or intraoperative phase.
  • the risk of overdose or underdose of the specific anesthetics is shown, among other things, by atypical characteristics (signal forms) in the corresponding measured values.
  • At least one of the above objects is also achieved by a method for monitoring anesthetized patients with the steps of deriving electrical potentials of a patient with at least two electrodes and providing a measurement signal, amplifying the measurement signal with an isolation amplifier, filtering out a frequency band of interest from the measurement signal providing the signal at a signal output, measuring the blood flow velocity of terminal blood vessels of extremities of the patient, and providing the blood flow velocity measurement signal at a signal output.
  • the frequency band of interest is filtered out using a bandpass filter, and the filtered signal is integrated with an integrator.
  • An embodiment of the method for monitoring anesthetized patients also has the steps of measuring an electromyogram of the facial muscles and / or forearm muscles of the patient and providing the electromyogram at a signal output.
  • a further embodiment of the method for monitoring anesthetized patients further comprises the steps of: comparing the integrated signal, the blood flow velocity signal and the electromyogram signals with limit values respectively predetermined for the individual signals and outputting a warning signal when each of the three signals deviates from its predetermined limit by a predetermined value.
  • the method of monitoring anesthetized patients may be performed in combination with the previously described apparatus for measuring electrical potentials of a living being.
  • the method can be used for Monitoring anesthetized patients but also in combination with conventional EEG devices.
  • FIG. 1 shows a schematic representation of a device for measuring electroencephalographic signals according to an embodiment of the present invention
  • Figure 2 is a schematic representation of another embodiment of the invention of a device for measuring electroencephalographic signals
  • FIG. 3 shows equivalent circuit diagrams of a frequency channel according to an embodiment of the invention with two low-pass filters connected in series (FIG. 3a), two high-pass filters connected in series (FIG. 3b) and with an amplifier, full-wave rectifier and integrator (FIG. 3c) electrically connected to one another;
  • FIG. 4 shows a representation of signals which could be tapped off at the signal output of a device according to FIG. 2;
  • FIG. 5 shows a schematic representation of an apparatus for the early detection of secondary sleep attacks in accordance with an embodiment of the present invention
  • Figure 6 is a schematic representation of a device for monitoring anesthetized
  • the device 1 for measuring electroencephalographic signals has at least two electrodes 2, wherein the individual representation has been dispensed with.
  • the electrodes 2 are connected, for example, with the skull of a subject. Between the electrodes 2 there is a voltage signal whose origins are predominantly in specific see areas of the brain lie in the sphere of influence, the electrodes 2 are arranged in the operation of the device 1.
  • the signal detected by the electrodes 2 is forwarded to an isolation amplifier 3, which is electrically connected to the electrodes 2.
  • a bandpass filter 4 is electrically connected, which filters the coming of the isolation amplifier 3 signal.
  • the band-pass filter 4 of this embodiment is selected to pass only the frequency components of the signal which are in a range of 0.5 Hz and 42 Hz.
  • the filtered signal then passes into an integrator 5, which is electrically connected to the bandpass filter 4.
  • the integrated signal wherein the integration values of successive integration intervals are present in the form of a time-varying signal, can be tapped off. Not shown is a connected to the signal output 6 display device for graphical representation of the output signal.
  • the bandpass filter 4, the integrator 5 and the signal output 6 form a first and only frequency channel 10 of the device 1.
  • FIG. 1 A development of the device 1 according to FIG. 1 is shown in a schematic view in FIG. In contrast to the device 1 from FIG. 2, the device V has four frequency channels 10a to 10d.
  • the device V for measuring electroencephalographic signals has three suitable electrodes for the derivation of electroencephalographic signals 2 and an electrically connected to the electrodes 2 isolation amplifier 3.
  • the signal at the output of the isolation amplifier 3 via a further filter 7, an amplifier 8 and a comparator 9 given the four frequency channels 10a to 10d, each having a signal output 6a to 6d.
  • Each of the four channels 10a to 10d has a bandpass filter 4 and an integrator 5 so that each channel 10a to 10d forms an independent electrical unit.
  • each of the four bandpass filters 4 comprises a series of filters 11, 12, 13, 14, a first low-pass filter 11, a second low-pass filter 12, a first high-pass filter 13 and a second high-pass filter 14 in this order electrically connected to each other.
  • the two low-pass filters 1 1, 12 connected in series and the two high-pass filters 13, 14 connected in series form in each case a third filter Order, which has an optimized slope and adjusted quality.
  • Each of the filters 1 1, 12, 13, 14 has an attenuation of -36 dB / octave.
  • the frequency channels 10a to 10d shown in FIG. 2 are largely identical in their basic functionality and their technical function, so that identical reference symbols are used for the components integrated therein. Nevertheless, the band pass filters 4 of the respective channels 10 on closer inspection differ in that the low and high pass filters 1 1, 12, 13, 14 of each channel 10a to 10d have individual parameters and thus a matched pass band compared to the other channels.
  • each bandpass filter 4 is chosen such that it passes a specific frequency range of the measured electroencephalographic signal.
  • Each bandpass filter 4 thus provides a specific frequency band.
  • the channel 10a in this embodiment is arranged to pass an a frequency band having frequencies in the range of 8 Hz to 13 Hz, while the second channel 10b transmits a ⁇ frequency band having frequencies in the range of 14 Hz to 30 Hz.
  • the parameters of the filters 11, 12, 13, 14 are selected in such a way that they provide a ⁇ frequency band with frequencies in the range from 0.5 Hz to 3.5 Hz.
  • the parameters of the filters 11, 12, 13, 14 of the fourth channel 10d are designed to provide a ⁇ frequency band with frequencies in the range of 4 Hz to 7 Hz.
  • a full-wave rectifier 16 is further electrically connected, which rectifies the respective amplified and bandpass filtered signal so that positive and negative signal amplitudes do not cancel out in the subsequent integration.
  • each one integrator 5 For the actual integration behind each full-wave rectifier 16 each one integrator 5 is connected, which integrates the corresponding signals over a predetermined integration interval t int and forwards to the respective signal output 6a to 6d.
  • the integration interval t int of each integrator 5 is selected to be 250 ms in the illustrated embodiment.
  • the embodiment of FIG. 2 also has a first filter 7, an amplifier 8 and a comparator 9, which are included in this order. electrically connected and arranged between the isolation amplifier 3 and the channels 10a to 10d.
  • the first filter 7 is set up such that, during operation of the device, the signal for noise suppression coming from the insulation amplifier 3 is limited to a frequency range from 0.05 Hz to 100 Hz.
  • the filter 7 has a Bessel high-pass filter with a cutoff frequency of 0.05 Hz and an attenuation of -18 dB / octave and a low-pass filter with a cutoff frequency of 100 Hz and an attenuation of -18 dB / octave.
  • a 50 Hz notch filter is provided in the filter 7 at -36 dB / octave for the separation of remaining AC components in the DC supply voltage.
  • the comparator 9 checks whether the electrical resistances between the electrodes 2 are possibly greater than 1 k ⁇ and thus detects whether the electrodes 2 may not be contacted correctly. In the event that one or more electrodes 2 are not properly connected, the electrical resistance is greater than 1k ⁇ and the comparator 9 outputs a constant signal in the form of a -6V voltage signal to the signal output 31, where the signal is for evaluation Available.
  • a first tap is provided between the isolation amplifier 3 and the first filter 7, which conducts the raw signal coming from the isolation amplifier 3 to the signal output 32.
  • a tap is provided in each of the four channels 10a to 10d between the amplifier 15 and the full-wave rectifier 16, so that the band-pass filtered and amplified, but not integrated signal of each channel 10a to 10d at a signal output 30a to 30d can also be tapped.
  • the signal outputs 6a to 6d, 30a to 30d and 32 there are thus signals in various stages of processing, all of which can be used for evaluation and / or for further processing.
  • FIGS. 3a to 3c show a circuit diagram of one of the four channels 10a to 10d according to the embodiment of FIG. 2, the arrangement of the components of the individual ones being as already mentioned Channels 10a to 10d are basically identical. Accordingly, FIG. 3a shows the two series-connected low-pass filters 11, 12, while FIG. 3b shows the two high-pass filters 13, 14 connected in series, and FIG. 3c shows the amplifier 15, the full-wave rectifier 16 and the integrator 5 connected in this order are connected.
  • the first low-pass filter 1 1 has the electrical resistors R 1 to R 5, the capacitors C 1 to C 3 and the operational amplifier I which are interconnected to realize an active third-order low-pass filter.
  • the gain of the operational amplifier is set by the choice of the electrical resistance R5.
  • the second low-pass filter 12 is connected, which has the resistors R6 to R10, the capacitors C4 to C6 and the operational amplifier II.
  • the arrangement of the individual components corresponds to that of the first low-pass filter 11, so that the second low-pass filter 12 is also an active third-order filter.
  • the two low-pass filters 1 1, 12 connected in series thus act as the sixth-order active low-pass filter.
  • the sixth-order low-pass filter such that the signal output by the comparator 9 can be tapped off the electrical ground resistor R1 of the first low-pass filter 11 relative to the ground GND.
  • the double arrow in FIG. 3a indicates the connection to the pin IN of FIG. 3b, which serves as the input of the circuit from FIG. 3b, so that the signal filtered with the low-pass filter is applied between the pin IN and the ground GND.
  • the high-pass filter 13 shown in FIG. 3b has the resistors R1 1 to R14, the capacitors C7 to C9 and the operational amplifier III. on.
  • the high-pass filter 14 connected behind the high-pass filter 13 has the resistors R15 to R18, the capacitors C10 to C12 and the operational amplifier IV.
  • Both the high-pass filter 13 and the high-pass filter 14 are third-order active high-pass filters, so that an active high-pass filter of the sixth order is implemented by the series connection shown.
  • the resistors R14 and R18 serve to adjust the gain of the respective operational amplifier III. and IV. Behind the sixth-order high-pass filter, which forms the band-pass filter 4 together with the sixth-order low-pass filter, the amplifier 15 is connected. The connection of the bandpass filter 4 to the amplifier 15 is indicated in the transition from Figure 3b to Figure 3c with a dashed line extending from the double arrow OUT of Figure 3b to the pin IN of Figure 3c.
  • the amplifier 15 has the resistors R19 to R21 and the operational amplifier V.
  • the electrical resistance R19 is designed as a potentiometer with which the amplification factor G 3 can be set.
  • the full-wave rectifier 16 is connected, the resistors R22 to R25, the capacitors C13, C14, the diodes D1, D2 and the operational amplifier VI. having.
  • the resistor R23 serves to adjust the gain of the operational amplifier.
  • the capacitors C13, C14 With the capacitors C13, C14, the applied AC voltage signal can be transmitted substantially loss-free to the full-wave rectifier, which rectifies the signal.
  • the rectified signal is then integrated with the integrator 5, which is connected to the full-wave rectifier 16, in dependence on the predetermined integration interval t int . As can be seen in FIG.
  • the integrator 5 has the resistors R26 to R29, the capacitor C15 and the operational amplifier VII. Between the pin OUT and ground GND of Figure 3c is accordingly the bandpassgefilter- te, amplified, rectified and integrated signal of the respective channel 10, which can also be tapped off at the associated signal output 6.
  • FIG. 1 A comparison of electroencephalographic signals, as can be measured with an embodiment according to FIGS. 2 and 3, is shown in FIG.
  • the curves 1 and 2 show the a-frequency band with a frequency range of 8 Hz to 13 Hz
  • the curves 3 and 4 the ⁇ -frequency band with a frequency range of 4 Hz to 7 Hz
  • the curves 5 and FIG. 6 shows the ⁇ frequency band with a frequency range from 0.5 Hz to 3.5 Hz
  • the curves 7 and 8 the ⁇ frequency band with a frequency range from 14 Hz to 30 Hz.
  • FIG the signal amplitudes are plotted in volts versus time in seconds.
  • Curves 1, 3, 5, and 7 show the non-integrated signal of a channel 10a-10d after bandpass filtering and subsequent amplification, as applied to the signal outputs 6a-6d.
  • the associated curves 2, 4, 6 and 8, however, show the integrated signal of each channel 10a to 10d, as it rests behind the integrator 5 of each channel and can be tapped at the respective signal output 6a to 6d. While the degree of excitation from curves 1, 3, 5 and 7 is not readily apparent, this is easily possible for the integrated signals of curves 2, 4, 6 and 8.
  • FIG. 5 shows a development of the embodiment according to FIG. 1, namely a device 21 for the early detection of microsatricidal attacks, in a schematic view.
  • the device 21 for the early detection of microsatisfactor attacks has three electrodes 2 suitable for the discharge of electroencephalographic signals, an isolation amplifier 3 electrically connected to the electrodes 2 and a signal output 6 electrically connected to the isolation amplifier 3. Between the isolation amplifier 3 and the signal output 6, a bandpass filter 4 and an integrator 5 are connected.
  • a signal generator 18 which emits light as a provocation signal with a predetermined and adjustable frequency. The light is visually perceptible by a subject during operation of the device.
  • the signal generator 18 is formed as a light-emitting diode having a circular, light-emitting surface with a radius of 5 mm and emitting light of a wavelength in the range of 600 nm to 630 nm.
  • the signal generator is controlled by a controller 17 with a predetermined switching sequence, so that the signal generator is alternately switched on and off.
  • the device 21 has a correlation detector 19, which is electrically connected both to the signal output 6 and to the controller 17 and an alarm transmitter 20.
  • the controller 17 provides the correlation detector 19 with a reference signal which reflects the switching state of the light-emitting diode 18.
  • the provocation signal is perceived by the subject as a result of light pulses, this is reflected in an excitation of brain waves which can be detected with the aid of the device according to the invention.
  • the correlation detector 19 detects a correlation between the provocation signal and the signal present at the signal output 6, it outputs a corresponding control signal to the controller 17.
  • the controller 17 in turn reduces the frequency at which the LED 20 is turned on and off. In this case, a rest phase of 30 seconds is provided between the emission of two provocation signals with different frequencies.
  • the frequency of the provocation signal is reduced in four stages, namely at 40 Hz, 35 Hz, 30 Hz and 25 Hz.
  • the correlation detector 19 can not detect a correlation between the brain currents applied to the signal output 6 and the provocation signal, ie the emission of a light Signal having a switching frequency in accordance with the provocation signal results in no measurable excitation of the brain waves, so the correlation detector 19 generates an alarm signal, which is forwarded to the alarm generator 20.
  • the alarm generator 20 generates an audible alarm signal and thus indicates that the subject's attention has fallen below a predetermined limit and thus threatens a second sleep attack.
  • FIG. 6 shows a schematic view of an apparatus 22 for the monitoring of anesthetized patients, which uses the device 1 for measuring electroencephalographic signals from FIG.
  • the device 22 for monitoring anesthetized patients has three electrodes 2, which are suitable for the derivation of electroencephalographic signals and which are electrically connected to an isolation amplifier 3.
  • the isolation amplifier 3 is in turn electrically connected to a signal output 6.
  • a bandpass filter 4 and an integrator 5 are connected between the isolation amplifier 3 and the signal output 6, a bandpass filter 4 and an integrator 5 are connected.
  • the bandpass filter 4 has a passband of 0.05 Hz to 0.5 Hz.
  • the device 22 has a device for measuring the terminal blood flow velocity, namely a laser Doppler flow meter 23, which determines the blood flow velocity of the subject with the aid of laser radiation having a wavelength of 805 nm and taking advantage of the Doppler effect.
  • the device 22 also includes an electromyograph 24 which senses the activity of the facial muscles, preferably those of the facial nerve, and / or the activity of the forearm muscles of the patient.
  • the output signals of the device 1 for measuring electroencephalographic signals, the laser Doppler flow meter 23 and the electromyograph 24 are fed into the evaluation unit 25.
  • the evaluation unit 25 analyzes the state of anesthesia on the basis of the derived brain waves, the blood flow velocity and the muscle activity of the subject. For this purpose, all three signals are compared with a threshold value. If all signals simultaneously have a predetermined deviation from the respective threshold value, the evaluation unit 25 triggers an alarm if it must be assumed that the patient is at least not absolutely free from pain.

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Abstract

L'invention concerne un dispositif de mesure de potentiels électriques d'un être vivant, comprenant au moins deux électrodes pour dévier des potentiels électriques, un amplificateur d'isolation électriquement relié aux électrodes et une sortie de signaux électriquement reliée à l'amplificateur d'isolation, l'amplificateur d'isolation et la sortie de signaux étant agencés de sorte que l'amplificateur d'isolation amplifie le signal provenant des électrodes et que le signal amplifié peut être capté à la sortie de signaux. Entre l'amplificateur d'isolation et la sortie de signaux sont montés au moins un filtre passe-bande et au moins un circuit d'intégration, le filtre passe-bande et le circuit d'intégration étant agencés de sorte que, le dispositif étant en fonctionnement, le filtre passe-bande laisse passer une plage de fréquences prédéterminée du signal et le circuit d'intégration intègre le signal filtré, le signal ainsi intégré pouvant être capté à la sortie de signaux, et le filtre passe-bande, le circuit d'intégration et la sortie de signaux formant ensemble un canal de fréquence.
PCT/EP2013/056567 2012-03-29 2013-03-27 Dispositif et procédé de mesure de potentiels électriques d'un être vivant WO2013144229A1 (fr)

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