FR2520605A1 - MEASUREMENT AND CONTROL SYSTEM, PARTICULARLY FOR MONITORING THE CONDITION OF A PATIENT DURING A SURGICAL OPERATION - Google Patents

Abstract

THIS INVENTION CONCERNS A MEASUREMENT AND CONTROL FACILITY FOR MONITORING AND RECORDING THE CONDITION OF A PATIENT, PARTICULARLY DURING ANESTHESIA DURING SURGICAL OPERATIONS. THIS INSTALLATION INCLUDES ELECTRODES 1 FOR DETECTING BIOELECTRIC SIGNALS REPRESENTATIVE OF THE SPONTANEOUS EMG PATIENT ACTIVITY, MEANS 2 FOR AMPLIFYING THESE SIGNALS, MEANS 3, 6 TO DISTINGUISH THE EMG COMPONENTS OF SAID SIGNALS AND FOR THE QUANTIFIER OF A CONVENIENT , AS WELL AS THE MEANS FOR PROCESSING THE RESULTING ELECTRICAL INFORMATION FOR THE PURPOSES OF DISPLAY. THE INSTALLATION ALSO INCLUDES MEANS 14, 15 FOR SEPARATELY MEASURING THE NEUROMUSCULAR LOCKING OF THE PATIENT, ALMOST AT THE SAME TIME AS SAID EMBODIMENT SPONTANEOUS BY STIMULATING A NER MOTOR BY MEANS OF ELECTRIC PULSES AND MEASURING THE REACTION MUSCULAR. . THE QUANTITIES SO DETERMINED ARE DESIGNED TO BE RECORDED AND DISPLAYED BY MEANS OF DISPLAY ON A REAL-TIME BASIS, SO THAT THE INFORMATION OBTAINED FROM SAID EMONT SPONTANEOUS SIGNALS AND THE MUSCULAR PARALYSY MEASURED BY STIMULATION COMMON DISPLAY 10.

Description

The present invention relates to an installation for measuring and

  control to record and monitor the status of a patient, in particular,

  during anesthesia during surgical operations.

  Monitoring a patient during surgical operations has two main phases: on the one hand, it is necessary to ensure that the depth of the patient's anesthesia and that the neuromuscular blockage or paralysis are sufficient for execution surgical or other operations and, on the other hand, care must be taken that the patient's paralysis and state of anesthesia do not become too deep; 2 s, the risk being a permanent coma of the patient It is obvious that the more numerous and faster the information concerning both the patient's state of anesthesia and the muscular relaxation of the patient and the more clear and easily interpretable is said information, the more conclusions we can draw

  are safe and faster it is possible to take action if necessary-

  ment necessitated by the situation.

  Traditionally, the depth of anesthesia of a

  patient mainly by controlling his blood pressure, pulse,

  trocardiogram, respiration and pupillary reflexes A problem with these control parameters is that reliable conclusions cannot be drawn from them, but that the estimates which are arrived at

  depend on how the anesthetics and paralyzers are used

  read at the time considered In addition, these parameters can be modified

  by several factors As examples of these factors, we can cite a pre-

  possible medication, patient illness, age and general condition, location and degree of surgical stimulation, the combined effect of different anesthetics and paralyzers, body temperature, partial pressure of blood carbon dioxide ( Pa C 02) A difficulty is also raised by the variations of these parameters depending on the dosage

  anesthetic and paralyzing substances.

  It is also known to ensure the depth of anesthesia by monitoring the EEG waves representing the electrical functioning of the brain (electroencephalogram) in order to control the electrical activity of the patient's brain. On this basis, a group of researchers from the " Duke University Medical Center "(from Durham, North Carolina, USA) has devised ways to significantly simplify the detected and recorded basic information which

  are important for monitoring the patient's condition during anesthesia.

  Since the EEG waves recorded in the patient's skull region are often scrambled by those from muscle activity, the basic idea has been that, in conjunction with monitoring the EEG using a

  recorder, it would be equally possible to use and record the acti-

  vity EMG (electromyogram) representing the electrical action of the muscles and

  which will be further qualified by the "spontaneous EMG" suite Based on the findings

  monitoring made by this group of researchers, EMG monitoring can be advantageously used to signal sufficient relaxation of a patient,

  since the registration of the EMG surely reveals its own

  tions of the patient concerning his relaxation, regardless of the means available to an outside observer If, then in relation to the monitoring, it is verified that, on the basis of the recorded EMG activity, the patient's relaxation is not sufficient, for example for surgical operations, the situation can be remedied by administering to the patient more paralyzing or anesthetic agent. On the other hand, EEG monitoring can be used to observe the depth of the patient's state of anesthesia (References :

  D.A Davis, F F Klein, M Harmel, L Burton, L Dewell: The Electroencepha-

  lomyogram, Quantitation of Depth of Anesthesia, Relaxation et Paralysis, American Society of Anesthesiologists of San Francisco, October 20 25, 1979, I.H Harmel, F F Klein, D A Davis: The EEMG A Practical Index of Cordial

  Activity an Muscular Relaxation, Acta Anaesthesiologia Scandinavica 1978, fasci-

cule 70, pages 97 102).

  On the other hand, it was discovered (B R Fink: Electromyography in

  General Anaesthesia, British Journal of Anaesthesia, 1961, 33, pages 555 -

  559) that the activity of the abdominal muscles tends to be increased by stimulation

  surgery and to be reduced by the action of anesthetics and

  muscle laxants The group of researchers mentioned above also

  verified that the facial EMG provides information on the general state of activity

  vity of the patient and represents a combination of the following parameters having an effect on the EMG signal: 1 The depth of anesthesia; 2 Neuromuscular blockage; 3 Painful sensations So, we can say in summary

  that when, during surgical operations, this spontaneous EMG is sufficient

  low, the depth of anesthesia and muscle paralysis of the patient

  are, in most cases, considered sufficient.

  quence, the increase in the amplitude of the spontaneous EMG signal, during a surgical intervention, is a cause for concern However, it is then difficult to determine which of the above parameters is the cause of

  this elevation and whether to give the patient more anesthetic agent

  siant, paralyzing or analgesic and in what dose.

  An EEG / EMG analyzer, based on what has just been described above,

  was carried out by the aforementioned group of researchers by measuring and processing

  both said signals and by generating with a digital voltmeter and a recorder, from the EEG signal, an average frequency and from es s: gau: ès and EMG an average unidirectional amplitude From the point of - rue de l'z Sraur, this solution is not very clever because it encounters _ a difficulty

  particular to monitor and determine the origin of affi es quantities.

  Besides that, relatively sophisticated recording and display systems have been developed simply for EEG waves. A known monitoring system for EEG waves is disclosed in the US patent.

  no. 4,215,697 In this system, the distribution of amplitude or power

  frequency and frequency of the EEG signal recorded from the skull of a pa-

  holds is displayed as a function of time three-dimensionally on a screen the video control in the form of a diagram with continuous propagation of srcene that, in addition to information in real time, the screen displays a part the history of the signal EEG A other EEG monitoring system I 'the prior art uses, moreover, a video control screen, to sharpen the frequency spectrum of the amplitude or power of the EEG signal in a' time representing a second dimension, in the form lines of luminous points with continuous propagation, the last line of luminous points in date representing the real time The intensity of the amplitude or the real power is simply represented by the relative luminosity of the points These known systems offer a means of monitoring much more representative than the simple EEG curve obtained on a recorder However, these systems are relatively complicated and expensive and moreover, are not well suited s for

  display and monitor multiple signals simultaneously.

  An object of the present invention is to provide an improved nveusyst EMS for monitoring a patient which makes it possible to eliminate the drawbacks of the prior art and which provides more reliable information concerning the state of anesthesia and paralysis of the patient. , information that is displayed from the

as clearly as possible.

  Another object of the invention is to provide a compact display

  and easily usable by the operator, from the state of anesthesia and paraly-

  Another object of the invention is to provide an analog display of these quantities so as to obtain, on the one hand, the value of a patient in the form of signals to be determined so that the mutually complementary and explanatory quantities are easily comparable. control value in real time of these quantities and on the other hand, their history At the same time, the aim is also to provide a representative display and, preferable for the use

  memorization equipment Other objects and advantages of the invention rt-

  will emerge from the description which follows.

  The invention achieves the goals which it has set for itself by a measuring and control installation for monitoring and recording the condition of a patient, in particular during anesthesia during surgical operations, which is characterized in that it comprises electrodes for detecting bioelectric signals representative of the spontaneous EMG activity of the patient, means for amplifying said signals, means for dictating the EMG component of said signals and for quantifying it in an appropriate manner, as well as means for processing this information in order to display it, in that the installation also comprises means for separately measuring the neuromuscular blockage of the patient, practically at the same time as said spontaneous EMG activity, by stimulating a motor nerve by means of electrical impulses and by measuring the muscular reaction, preferably by means of an EMG, and in that the determined quantities are arranged to be recorded and a displayed by means of display, practically on a real-time basis, and preferably in such a way that the output information relating to said spontaneous EMG and that relating to the muscular paralysis measured by stimulation appears on a common display unit . According to the invention, it is possible for the anesthesiologist to continuously monitor, on a real time basis, and to compare each other, of a

  on the one hand, a measured and determined spontaneous EMG of the patient and on the other hand, its para-

  muscle lysia, which helps in a new and remarkable way, to

  to tune the responses due to arousal and arousal from those which result from the reduction of muscular paralysis In this respect, the compactness and the real time of the display are important, since the awakening responses are rapid phenomena placing the electrodes in the skull area

  and / or the neck of the patient, it is also possible, by means of electro mg

  des, to monitor the electrical activity of the patient's brain (EEG) and based on it, to ensure that the anesthetic state of the patient does not become too deep Thus, the spontaneous EMG, representative of the degree of muscle paralysis , informs the anesthesiologist of awakening responses or of too light anesthesia and on the other hand, the EEG warns him of disturbances

  metabolic processes in the brain, which are linked to too deep anesthesia.

  In addition to real-time information, the display means are preferably capable of simultaneously presenting a significant part of the history or of the origin of the events recorded. By adopting, for the

  EMG waves a relatively wide frequency band, it is possible to con-

  contribute more to the reliability of EMG information, since EMG waves

  appear in a wide frequency band As on the other hand, the importance

  so much is to know if the EMG activity actually exists and not what is its frequency, its amplitude or its absolute power, we use according to

  the invention a column diagram displaying in particular the pre-

  sentes in a logarithmic form and used to visualize, most clearly

  possible, the patient's physical activity The display in a logarithmi-

  that is also preferable with regard to amplitude or power

  EEG waves, since the effect of anesthesia decreases to a significant extent

  aunt, the level of EEG waves, door that the detection of variations rela-

  tives of EEG activity offers much more interest than the detection of

  absolute values of the signal peaks, even if they have a high intensity.

  EEG waves provide a good indication of the anesthetic state of the patient, as explained above. A preferred indication for the control of this state is explicitly obtained by monitoring a possible simultaneous significant reduction in the amplitude or power of the EEG signals. and the average frequency of the EEG In practice, the anesthesiologist, or another person performing the functions of monitoring the anesthetic state of the patient in an operating room, generally performs other tasks at the same time, such as monitoring the functioning of the heart, blood pressure, etc., not to mention the actual administration of the anesthetic and the paralyzer to the patient, so that it is not always possible for him to continuously observe the display device In an installation according to the invention, it is preferable to incorporate an automatic alarm device by selecting a limit value or an appropriate threshold for the sum of the values represented. presenting these quantities By providing such an alarm in the

  monitoring of spontaneous EMG signals to indicate insufficient relaxation

  patient, for example, for a surgical operation, it is

  possible to avoid the need to continuously observe the display device

  filing. We will now describe the invention in more detail with reference

  in the single figure of the appended drawing which is a block diagram of an installation

  measurement and control relationship in accordance therewith.

  In this installation, the bioelectric activity of a patient P is observed by means of detection electrode 1 The signal obtained is amplified in an insulating preamplifier 2 and passes through discrimination means

  bands 3, and 4 which separate the EEG and EMG wave ranges from each other.

  In reality, these wave ranges overlap or overlap in a certain

  taine mesure As far as the extent of the information to be monitored is concerned, however, it is perfectly sufficient and, for processing

  signals, it’s easier to completely separate the wave ranges to be analyzed

  for example, by adopting for the EEG band the range from 1 to 40 Hz, a range from 2 to 25 Hz being sufficient in practice, and for the EMG band the range from 60 to 500 Hz, a range from 65 to 350 Hz being sufficient, in practice. One factor that plays a role in the choice of bands is that, since the EEG and EMG waves can be relatively weak,

  it is necessary to eliminate the main disturbances before analysis.

  When the network frequency is 50 Hz, the selected EEG ranges can

  wind ensure direct elimination of the fundamental disturbance frequency

  and its harmonics The elimination of disturbances from the

  EMG signal is effected by means of a set of filters 5 which can advantageously-

  be designed as described in Finnish patent application no. 811 941.

  Then, by sampling the EMG signal and averaging the samples

  lons, it is possible to eliminate the fundamental disturbing frequency of the signal and its odd harmonics, the signal being put at the same time in the form of a wave of frequency lower than that of the fundamental disturbing frequency Thus, even harmonics can be eliminated by means of a simple high-pass filter This ripple of a signal does not affect monitoring in this case, since the amplitude or the power of the EMG signal is simply determined After the elimination of disturbances from the network , the

  determination of the amplitude or power of the EMG signal and the 'logarithmi-

  sation "of the values is carried out by means of known equipment 6 Similarly, equipment 7 is used to determine the amplitude or the strength of the signal

  EEG and also to make logarithmic values Equipment 8 is used to determine

  reduce the average frequency of the EEG signal.

  A processor 9 is designed to collect samples, represented

  preferably, successive periods of time of equal duration, starting from the quantities, determined continuously and for processing these samples in a way allowing them to be displayed on a video control screen or on a similar display device 10 as continuous propagation

for each quantity measured.

  An essential part of the system is that measuring the blockage

  patient's neuromuscular, regardless of the EMG and EEG signals described above

  above This can be done, in a manner known per se, by a device

  , a nerve stimulator 15 b periodically delivering electrical impulses

  successive electrodes 14 b It can, for example, deliver four pulses in the space of a second ("train of four"), these trains of four pulses being repeated at intervals of 10 to 60 seconds The muscular reaction is recorded by the electrodes 14 a, in the form of a signal

  EMG amplitude completely independent of the spontaneous EMG signal described above

  above, using an electric detection and amplification device 15

  trode 14 a is a reference electrode.

  The processor 9 controls the operation of the device 15 and ela-

  boron information it receives for display on a monitor

  video screen 10 The display can advantageously be designed so that each pulse is represented by a column, which represents the EMG response

  measured, the patient's tendency to muscle paralysis being thus clear-

  visibly visible With regard to interpretation, the main points are,

  on the one hand, the length of a column which represents the muscular force remaining

  aunt and on the other hand, the ratio between the first and the last columns of the same period which represents the degree of decrease in muscular strength during the repeated stimulations With regard to the practical realization of the muscular paralysis measures, it is advisable to refer, for example, to the following articles: Lam, HS, Cass NM and Ng, RC "Electromyographic monitoring of neuromuscular block", Br T Anaesth (1981), 53, 1351; Lam, H.S, Morgan D L and Lampard D G "Derivation of reliable electromyograms and their relation to tension in mmnmalian skeletal muscles during synchronous stimulation" EEG Clin Neurophysiol (1979, january), 46, 72; Ali, HH and Savarese, JJ "Monitoring of neuromuscular function Anesthesiology" (197-6) 45,216 In this way, separately measured muscle paralysis can be used to determine which part of the increase in spontaneous EMG activity, measured on the face of a patient, results mainly from insufficient paralysis and which part comes from an insufficient depth of anesthesia, since the EMG activity due to algenic stimulation can be

  controlled by simultaneously monitoring the actual surgical operation.

  The installation also includes means 11 for storing the information

  matiors should be displayed so that any part of the history

  toric of the recorded signals can be presented on a control screen

video, if applicable.

  When the screen has been filled in the direction of the time axis, it is possible, for example, to roll back the histograms by 2/3 back along the time axis Thus, assuming that the time axis

  represents, for example, a period of 30 minutes, the part of the diagram represented

  feeling the last 10 minutes can be shifted toward the beginning of the time axis to match the first 10 minutes It should be noted

  that the column diagram or histogram representing muscle relaxation

  laire, can, if desired, have a different time scale from that

other histograms.

  In the displays representing the EEG and the spontaneous EMG, each column can advantageously correspond to the measured average bt calculated for a period of 10 seconds. If necessary, the last column can be updated - for example, at intervals of one second, in order to provide continuous information practically in real time With regard to the means of storing information, such an arrangement is very advantageous,

  because it saves space The column representing the information

  tions in real time can also be slightly spaced from the rest of the histo-

  gram, as shown in the drawing Naturally, a corresponding arrangement

  laying can be adopted for recording muscle relaxation, for example, by measuring the cycle of four pulses more often than every minute, with the result that there are intermediaries representing

better real time.

  The installation can also be equipped with alarm means 12 which, under the control of the processor 9, automatically emits an alarm signal,

  for example, an audible or light signal, when one of the quantities

  lées goes below or exceeds the threshold set With regard to the over-

  monitoring of the EEG, the alarm can advantageously be arranged to trigger

  expensive when the frequency and the amplitude or the power go down simultaneously-

  ment below a certain limit On the screen, this alarm limit can be represented visually by a certain minimum level common to the columns indicating said quantities, this level being able to be marked visibly on the display device, if applicable This alarm signal is used

  to signal an excessive depth of the patient's state of anesthesia.

  In the same way, it is possible to provide a certain alarm mode in the spontaneous EMG monitoring systems, this alarm mode being neutralized when the patient's state of anesthesia and his degree of relaxation are sufficient to allow surgery, while it is triggered when EMG activity exceeds a certain limit, indicating that

  the patient's degree of anesthesia is insufficient.

  If desired, the quantities obtained can also be used to digitally display their value in real time, the threshold value of

  the alarm, etc., as shown in the drawing.

  It goes without saying that many modifications can be made to the embodiment shown and described, without however departing from the

part of the invention.

Claims (11)

  1 Measuring and control installation to monitor and record   trer the condition of a patient, in particular, during anesthesia during   of surgical operations, characterized in that it comprises electro-   (1) for detecting bioelectric signals representative of the spontaneous EMG activity of the patient, means (2) for amplifying said signals, means (3, 6) for distinguishing the EMG component from said signals and for quantifying it by appropriately, as well as means (9-) for processing this information in order to display it, in that the installation comprises   also means (14, 15) for separately measuring neuromuscular blockage   patient's blood, practically at the same time as said spontaneous EMG activity, by stimulating a motor nerve by means of electric pulses and by measuring the muscular reaction, preferably by means of an EMG, and in that the determined quantities are arranged to be recorded and displayed by   display means, practically on a real time basis and pre-   reference, in such a way that the output information relating to said spontaneous EMG and that relating to muscular paralysis measured by the   stimulation appear on a common display unit (10).   2 Installation according to claim 1, characterized in that the-   said electrodes (1) are arranged to be placed in the region of the skull and / or neck of the patient so as to also detect the EEG signals produced by the patient, and in that the installation takes signals (h, 78) to distribute   the EEG components of the signals of the bioelectric components and for quanti-   trust these components as appropriate.   3 Installation according to claim 1 or 2, characterized in that said spontaneous EEG and EMG components are designed to be able to be distinguished from one another with band discrimination means, so that the band chosen for the EEG component is in the range of 1 to 40 Hz, preferably 2 to 25 Hz, while the band chosen for the EMG component is between 60 and 500 Hz, preferably, between and 350 Hz.   4 Installation according to any one of the preceding claims,   characterized in that the EMG component is designed to be displayed in the form of effective values and in that the installation includes means   filter (5) for said EMG component in order to eliminate the fundamental frequency   of the electrical network, as well as its harmonic frequencies.   Installation according to any one of claims 2 to 4,   characterized in that said EEG component is designed to be displayed   in the form of rms or amplitude and frequency values.   6 Installation according to any one of the preceding claims,   characterized in that the determined quantities are designed to be displayed   stored simultaneously as analog histograms arranged in quantities in the form of sequences of two-dimensional transferable symbols, so that one dimension is designed to indicate the quantized value and the other dimension, parallel to the direction of transfer of the sequence of symbols   is arranged to indicate the time.   7 Installation according to any one of claims 2 to 6,   characterized in that said analog symbols representing in a quantified form the EEG and EMG components of the signals are arranged in the form of a column diagram, so that the columns relating to each quantity indicate mean values representing the periods of chosen times, and that this column diagram also has a column   designed to indicate the real-time value of the quantity.   8 Installation according to any one of claims 5 to 7,   characterized in that the display of said EEG signal signal is designed to   so that the analog columns describing the rms and fre-   quence are arranged to point in opposite directions, while their zeros are, at least substantially, aligned directly or by a narrow intermediate zone.   9 Installation according to claim 8, characterized in that it comprises an alarm device (12), for example for emitting a sound or light signal, which is designed to be activated when the joint length of the columns indicating the actual value of said EEG component and value   frequency drops below a selected limit.   Installation according to any one of claims 4 to 9,   characterized in that it includes an alarm system (12) designed to be activated   when the effective values of the EMG component exceed a certain threshold.   11 Installation according to any one of the preceding claims,   characterized in that stimulation by so-called "trains of four" is intended to be used to determine muscle paralysis, so that four electrical pulses separated from each other by short intervals are applied by means of a nerve stimulator in repeated cycles, and in that the measured EMG signal, representing the electrical reaction of the muscle is arranged to be displayed so that each electrical pulse is represented by an individual column indicating, preferably, the integrated value of the EMG signal measured over a longer period   shorter than the mutual interval between said four pulses.   12 Installation according to any one of the preceding claims,   characterized in that it comprises a digital / analogue converter and a memory device (11) for storing information displayed in digital form, so that a necessary part of the history of the   detected signal can be redisplayed by means of said display unit.   13 Installation according to any one of the preceding claims,   characterized in that it comprises means (6,7,8) for delivering si-   output signals representative of the amplitude or effective values of   at least one of the signals, in a logarithmic form.