CZ20002377A3 - Process and apparatus for automatic monitoring the anaesthetized status of a patient in the course of a surgical procedure on the patient - Google Patents

Abstract

Device (10) to automatically monitor the level of the unconscious patient (13) during surgery on the patient (13), wherein the patient (13) has an inflatable installed a device (19) having a wall in contact with at least a portion of the pharynx the patient (13), and wherein the inflatable device (19) has a flexible tubular naphthenic feed (11) accessible from the outside patient (13). The device (10) comprises: a) a sensing means including a pressure sensor (P1, P2) removably connectable with an inflatable inlet to create an electrical output signal responsive to instantaneous sensing inflation pressure as a function of time during surgical intervention; b) means comprising an injection means having a front roller (26) adapted to be detachable a connection (11 ') with inflatable inlet, and a piston (27) in the cylinder (26) to define a substantially constant volume inflatable air inside the inflatable device (19), its inflatable inlet and the front of the cylinder (26), with the piston (27) is movable relative to the cylinder (26), the piston (27) is displaceable relative to the roll (26) for changing the ratio air volume between inflatable device (19) and the front of the cylinder (26); c) comparator means (40) for comparing the sensed pressure with the reference value and thus pro determining any deviation from the reference value; and d) a regulating means comprising reversibly actuating the drive means means (33) for moving the piston (27) in the cylinder (26) and thereby to restore the pressure to the reference value.

Description

Technical field

The present invention relates to a device useful for controlling and monitoring pressure within a laryngeal airway mask device (LMA device), and to a method and means for monitoring a patient's condition through changes in that pressure.

BACKGROUND OF THE INVENTION

LMA devices are well known and are extensively used in patient care both during and after surgery and during procedures involving maintenance of free airways. A description of such devices and their construction and use can be found in various patents, for example British Patent Specification No. 2,205,499 and US Patent Nos. 4,509,514; No. 5,303,697; No. 5,241,956; and No. 5,282,464.

That such LMA devices are well-accepted tools in patient care results from simple statistics. For example, it is estimated that such devices are used in approximately 50 percent of all surgical procedures requiring the use of general anesthetics in England, and their use is becoming increasingly accepted anywhere in Europe and the US.

Essentially, the LMA device comprises an air tube having a dimension and a curvature for general adaptation to the patient's airways; taking this. the air tube extends from the proximal end that is outside the patient to k

a distal end that carries a mask structure in the form of a dish or cover plate that faces and covers the patient's laryngeal inlet and is continuously surrounded by a resilient ring or cuff that is selectively inflatable to resiliently seal the body structure around the laryngeal inlet. In use, the LMA device is first completely drained to aid in its insertion and is then guided through the patient's mouth and neck to its correct position with the mask through the laryngeal opening. The inflatable cuff surrounding the mask structure is then inflated to form a seal between the mask and the laryngeal opening. The air pressure with which the cuff is inflated pushes the back of the mask dish against the solid tissue at the back of the neck to hold the device in place and form a seal. In this way, the device forms an open air path through which the patient's lungs can be ventilated.

It has been verified that these LMA devices are both solid in design and easy to use, even by ordinary medical professionals after the necessary training; however, if the mask is poorly inserted, a reliable air passage is not actually created and the patient's lungs are not properly ventilated. In addition, it has been found that the soft pliable silicone material of the cuff absorbs nitrous oxide from the anesthetic gas mixture, thereby increasing the pressure inside the cuff, and the cuff itself may occasionally create a leak which causes a reduction in its internal pressure. It has also been found that excessively high inflation pressure causes the cuff to restrict the blood supply to the mucosa covering the muscles around the laryngeal inlet, and long-term use of the LMA device may result in tissue death in such circumstances.

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Recently, in attempts to prevent the acquisition of consciousness during surgery, it has been proposed to monitor the patient's level of consciousness through a device capable of detecting and analyzing brain activity; however, the equipment required for such monitoring is very complex and expensive to manufacture. It has also been proposed to use an automatic device for monitoring the cuff internal pressure in a high volume, low pressure cuff associated with an endotracheal tube (EDT). It has been reported that such an EDT device is capable of measuring and regulating the cuff internal pressure with a tolerance of ± 3 mm of mercury column.

Muscle strain (tone) in the lower pharynx (hypopharynx - larynx) has been found to be related to the patient's apparent response to painful stimuli; it is thus possible to obtain information about the anesthetic state of the patient by monitoring the muscle tone in the hypopharynx. It has also been found that very small changes in this muscle tone are registered through the cuff of the LMA and are further registered through the volume of shared air so that pressure feedback sensing can be used to both automatically adjust the inflation pressure of the cuff of the LMA and to detect changes in the cuff. muscle tone in the hypopharynx. Of course, the detection of such changes is most preferably carried out without causing the patient's tissue to solidify, and in this context it has been found to be most convenient to inflate the cuff to pressures no greater than 60 cm of water column; for example, a 50 cm water column, and generally in the range of 25 cm water column to 100 cm water column. Accepting the use of pressures above 60 cm water column, it has been found that the pharynx is irritating, especially in long-lasting procedures, and therefore there is a risk of tissue damage.

SUMMARY OF THE INVENTION

The present invention has as its general object to provide a device that is capable of (a) monitoring, with gentle sensitivity, e.g. and (b) maintain a preset inflation pressure within narrow tolerances, for example ± 0.5 cm of water column.

It is also an object of the present invention to provide a device that can be reprogrammed to detect a plurality of different pressure variation patterns within the LMA device cuff and, if necessary, to provide a suitable range of different alerts to the operator in response to these patterns and to respond to anomalous operating conditions. threatening the integrity of LMA devices.

A specific object of the present invention is to provide a monitoring device of the above type in which, in the case of a patient who has already been anesthetized for surgery, monitoring the inflation pressure of the LMA device during surgery may include such automated analysis of changes in the inflation pressure of the LMA device to alert the surgeon the patient has just started to show an anomalous indication of the initial phase of awakening, alerting the anesthetist that the patient immediately needs additional anesthetics.

Another object is to provide a device that meets the foregoing objectives, is relatively inexpensive to manufacture, simple to set up, and reliable in operation and maintenance.

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Yet another object is to achieve the above-mentioned pressure control without the need for some other form of system whose components would introduce an additional time constant or hysteresis effect on the pressure monitoring function; as if it were caused by a container type system that is dependent on a container with pumped or otherwise increased pressure to restore the operating pressure of the device.

The present invention also aims to provide a method for maintaining a predetermined pressure in an LMA device and a method for monitoring pressure changes within an LMA device to detect changes in a patient's condition and to control the administration of anesthetics and / or muscle relaxants.

A preferred embodiment of the invention meets the above objectives by using an automatic pressure control device in a laryngeal airway mask device that has been installed in a patient, the LMA device comprising means that is inflatable to a predetermined pressure level to establish a sealed connection between the device interior and the laryngeal inlet. a patient, said device comprising:

(a) an injection means having a piston movable in the elongate cylinder with an outlet connection for supplying inflation air to the inflation means;

(b) a reciprocating actuating means for reciprocating the piston relative to the cylinder, thereby selectively shifting air to or from the inflation means;

(c) a control means comprising (i) a pressure responsive means connected to the output connection to respond to the instantaneous pressure, (ii) an adjustable means to select a set inflation pressure point value, (iii) a comparator means connected to respond to the selected point value To provide an electrical output signal representing the difference between the instantaneous pressure and the selected set point value; and (d) means connecting the electrical output signal for actuating the drive means for moving the piston relative to the cylinder in directional polarity to reduce the electrical output signal generated by the comparator means to zero or close to zero.

Preferably, the reversible drive means comprises an electric motor coupled to reversely drive the lead screw nut screwed onto the lead screw, the nut means being guided longitudinally and secured against rotation and coupled for direct longitudinal displacement of the piston in the cylinder.

A preferred electric motor is an open-loop stepper motor that operates without slip error or hysteresis delay. The direction and speed of the motor rotation depends on the sequence and frequency of the phase of the connected excitation.

More specifically, the reversible drive means comprises a stepper motor in which the pressure responsive means produces a first digital signal output in which the set point value is in the form of a second digital signal output and wherein the comparator means comprises a microprocessor programmed to deliver digital control signals for motor control.

Preferably, a first normally closed solenoid valve is connected to the outlet connection of the injection means for insertion between the outlet connection and the inflation means, the solenoid of the valve having

an electrical connection with the control means for actuating the valve to the open state for at least the duration of the electrical output signal and until the electrical output signal is non-zero. A second normally closed solenoid valve is also connected to the injector outlet connection and, when actuated to the open state, the second valve provides access to the injector for ambient air to add or discharge air from or into the system while the first solenoid valve is in the closed state. .

Preferably, the cylinder has an opening but otherwise closed longitudinal end; and each of the two normally closed solenoid valves is engaged to operate the opening end of the cylinder. The first normally closed solenoid valve is also coupled to the inflation means of the LMA and is operable to exchange air between the inflation means and the cylinder in accordance with the direction of movement of the piston; and the second normally closed solenoid valve is operable, as described above, to inject ambient air into the cylinder or to expel air from the cylinder depending on the direction of movement of the piston. The first limit switch means provides an electrical signal for the sensed state of advancing the cylinder to a predetermined limit proximity to the closed end, and the microprocessor-containing means responds to the piston sensed proximity signal, the microprocessor being programmed (1) to disable the actuator and return the first solenoid valve to its normally closed position, then (ii) to actuate the second solenoid valve to the open state while actuating the drive means for a predetermined reverse stroke, which draws in a fresh dose

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(Iii) deactivating the second solenoid valve and allowing the comparator means to reset the set point pressure inside the cylinder before reactivating the first solenoid valve and returning the comparator means to its inflation control function pressure of the LMA device to its set point value.

According to another microprocessor-controlled feature of the presently preferred system of the invention, the mask inflation pressure is continuously monitored for a patient who has been anesthetized and is undergoing surgery. The instantaneous mask inflation pressure is monitored for possible exceedances of predetermined upper and / or lower thresholds of normal control; and upon finding that the observed value has exceeded one of these limits, the first audible warning signal is given, which is interpreted so that although the patient is still asleep and under sedation, an inadvertent indication of hypofarynx / larynx (larynx) ), with associated transient local compression of the inflated patient's LMA device. At the same time, further automatic monitoring is performed to determine if any speed related conditions occur beyond a predetermined value of the evaluated criterion. Such occurrences of velocity-related states are further described below and are detected by continuously monitoring the analyzes performed on the incoming sequence of several consecutive readings that are stored within the system; and the output of these analyzes is continuously displayed on the system monitor. This velocity-based analysis of the monitored inflation pressure provides an additional indication of starting *

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9 and advancing the process of awakening and provides verification of the first alert, while further alerting the anesthetist with a visual alert to verify the anesthesia.

The apparatus and methods of the present invention will be described in more detail below by way of example with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is an illustration of a control / monitoring system according to the invention associated with an LMA device installed in a patient;

Fig. 1A illustrates the first of two sensed outputs of the percent awakening feature, which may include part or all of the display screen;

Fig. 1B is a similar representation for the second and subsequent sensed output of the percent sign;

Fig. 2 is a diagram of the mechanical components of Fig. 1 with a schematic indication of the engine and steering components;

Giant. Fig. 3 includes two separate sheets indicated by Fig. 3 (part A) and Fig. 3 (part B) and is a schematic of a control means comprising a comparator component and a motor control circuit for the system of Fig. 2, wherein the measured pressure is evaluated against the set point SP for determining the drive for the air moving piston and is further evaluated against the thresholds to determine the state of the painful warnings • · 4 · • 4 44

stimuli; wherein the dashed line 3A of Figure 3 (part A) and the dashed line 3B of Figure 3 (part B) represent one with the same plane in which Figure 3 (parts 3A and B) is interconnected to the full Figure 3;

Giant. 4 is a schematic illustration of a means by which the system can switch between a starter, centering, and reset circuit;

Giant. 5 is a graphical representation of a system of pressure changes detected as a function of time in the sealing cuff of an LMA device that is installed in a patient who has been anesthetized and is currently undergoing surgery but has or has not had any painful stimulus;

Fig. 5A is a graphical representation as in Fig. 5 just before and after the system has responded to an illustrative anomaly that responds to a painful stimulus;

Fig. 6A and Fig. 6C are tables showing details of conventional calculations performed on sampled test data, which tables compare these values to a set point and perform speed alert calculations for each sample;

Fig. 6B and Fig. 6D are graphical representations of the values presented in Figs. 6A and 6C; and

Giant. 7 is a representation of the empirical data obtained during the patient awakening sequence;

This data provides an example of a response to a painful stimulus as determined by an analysis of the monitoring function of the system.

DETAILED DESCRIPTION OF THE INVENTION

A. Mechanical construction and operation

Fig. 1 shows the monitoring system or device 10 of Fig. 2 with various control buttons including system start / stop button 52, control star / stop button 53, alarm reset button 54., ENTER button 55, and rotary knob 56 to select , among other things, the set point or threshold.

The monitoring system 10 has an outlet connection with a flexible inflatable / deflated air intake 11 of the LMA device 12 installed in the patient 13. As can be seen, the LMA device 12 comprises an air tube 14 with a proximal end means 15 for external adaptation of the venting or anesthetic delivery to the lungs of the patient. via a mask structure 16 having a cover plate 17 connected at a location 18 to the distal end of the air tube 14, the cover plate being circumferentially surrounded by an inflatable / blown ring or a collar 19 of resiliently flexible material; wherein the cuff 19 is shown in an inflated (inflated) state in a circumferentially sealed relationship with the body structure that surrounds the patient's laryngeal inlet 20 and distally positioned relative to the patient's esophagus inlet 21 (hypopharynx - pharynx of the pharynx). Of course, the internal design of the mask will include known means (not shown) to prevent the patient's larynx 22 from interfering with airflow or airflow.

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φ φ

anesthetics through the mask in any direction between the air tube 14 and the laryngeal inlet 20.

Typically, the inflatable / blowable ring or cuff 19 of the LMA device 12 is operated manually by a hand held injection means (not shown) that is detachably connected to the non-return valve means 11A that forms the outer end of the LMA device supply 11. When this injection means is disconnected, the non-return valve means 11A is in an operating state to retain the just inflated or deflated state of the LMA device 12. According to experience, the anaesthesiologist roughly knows how much pressure the cuff 19 can safely inflate once the LMA device 12 has been properly installed in the patient. Although a control system may be used to inflate the cuff 19 after it is installed in a patient, particularly in the case of a smaller cuff, the above-described manual inflating procedure is recommended prior to connecting the inflatable / deflated lead 11 of the LMA device with the control system of Fig. 2.

In Fig. 2, the air control input (V) includes, as is obvious, suitable means for detachably engaging the inflatable / blown air inlet 11 of Fig. 1, and the elongate flexible connection or extension 11B has (i) a system connection end (not) and (ii) an LMA connection end that is compatiblely connected to cooperate with the connection end of the non-return valve means 11A to maintain inlets 11 / 11B as a continuously open system connection with the inflatable means 19 (cuffed) LMA device 12 .. Device for fcfc ·· fc fcfc fcfc fc · • fc <

The air displacement comprises an injection means in the form of a rigid body 25 of a low friction material such as PTFE (teflon) with a cylindrical bore 26 having an open (or rear) end to cooperate with the piston means 27. The body 25 is secured to the frame member 28 and extends in the longitudinal direction to a closed (or front) end having an opening connection 29 with a direct conduit to the air control inlet 11 / LMA device; in this direct line, the first, normally closed, solenoid valve VI must be actuated to the open state if the inflatable air is to pass in any direction between the cylinder 26 and the inflatable / blowable means 19 of the LMA device.

The piston 27 is rigidly mounted to or formed with the front end of the longitudinal rod 30, the rear end of which is clamped to

5 of the sliding block 31. The block 31 forms a rigid transversely displaced arm for the longitudinally stabilized guide 32 and for reciprocating longitudinal displacement by means of a frame 33 of the electric stepper motor and its output shaft 34 with a lead screw; wherein the shaft 34 has a threaded engagement with the nut bore 34 in the rigid transversely displaced arm of the sliding block 31, and preferably the threaded bore 34 is formed in a PTFE body secured to the sliding block 31. The guide means 32 is to be understood as a schematic designation for a commercial longitudinal c _v linear bearing assembly (commonly known and obtainable under the name or trademark ROLLON) in which the elongated first guide member is attached to a frame member in which the elongated second guide member is attached to a sliding block 31, and wherein the bearing elements (friction reducing elements),

3®, such as bearing balls, guide and separate the guide surfaces of the respective guide elements. The described longitudinal holding and guide arrangement achieved by the means 32 naturally creates and ensures the possibility of precise longitudinal displacement of the piston 27 along the central longitudinal axis of the cylindrical bore 26, the block 31 and the piston 27 being effectively secured against rotation about the lead screw.

The motor means 33 has a step change, wherein precise directional control is achieved by varying the relative excitation of each of the four motor input terminals. The amount of rotation of the shaft 34 (and therefore the displacement of the piston 27) is controlled by the controller and the motor driver 47, as shown in FIG. 2.

Fig. 2 shows the total length L of the piston process in bore 26 for supplying the inflatable air from 15 'bore 26 to the inflatable / blowable ring or cuff 19 of the LMA device, as long as the first solenoid valve VI remains actuated to the open state; this same length may also be available for the return stroke of the piston 27, in which a controlled amount of inflatable air can be withdrawn from the cuff 19. The fixed mounted limit switches LS1 and LS2 are schematically indicated by the arrows in FIG. 2 to design a stop and / or return device. v.on each of the longitudinal limits of the total length L of the piston process. However, as shown in Fig. 2, the piston 27 is in displacement AL outside of the bore 25,25, wherein the arrow LSO identifies the point at which the cooperating contact or other switch triggering device 37 carried by the piston rod 30 (piston rod) cooperates with the piston. a limit switch LSO for electrical or other signaling of reaching the plunger retracted position shown, with simultaneous termination of the excitation pulses from the excitation circuit of Figure 3.

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Preferably, each of the limit switches is an optical device that relies on the contact or other triggering device 37 to be opaque and thus capable of interrupting the light beam from the source to the photocell at each of the respective locations where the limit switch is to act.

As further shown in Fig. 2, the front end of the piston rod 30 has a radial flange formation 38, circumferentially covered by a flexible housing 39 having an undercut bore that easily engages in a resiliently fastened engagement with the flange formation 38, for example in maintenance equipment by replacing the used housing 39 for the new cover 39.

Some pressure control operations may have the effect of causing interference with sensing pressure changes reflecting the patient's muscle reflexes. The system of the present invention has been designed to minimize such interference (interference) through a design concept as a substantially closed volume system in which cuff pressure variation settings 19 are made by displacement increments within the shared air volume, i.e. between (i) volume upstream of the piston 27 and within the front end of the cylinder 26; and (ii) the volume in the cuff 19.

This is superior to systems that regulate pressure by using a reservoir or reservoir with an elevated pressure to compensate for pressure changes in the cuff either by introducing air from such reservoir or by extracting air into the ambient atmosphere.

The intrinsic increase in system stability resulting from the use of the shared volume concept utilized by the system of the present invention makes it possible to achieve a high degree of accuracy without associated system monitoring or

BB5BSSB 0 0 • 0 · • 9 · nad nad nad ného ného 99 99 ného 99 99 99 99 99 More specifically, approximately 0.0005 ml (0.5 microlitres) of air is shifted with each step performed by the stepper motor 33. Such power is currently not achievable in a pressurized container type system.

Other elements of the apparatus of FIG. 2 include first and second pressure monitoring sensors P1 and P2 respectively. These pressure sensors, which indicate the total pressure in the device, are coupled to redundantly monitor the air pressure in the conduit between the cylinder opening connection 29 and normally closed by the first solenoid valve VI.

As shown, a second, normally closed, solenoid valve V2 is connected to the air duct between the cylinder opening connection 29 and the first solenoid valve VI. When actuated to the open state, the second solenoid valve V2 forms a path therefrom into the air open end 44 to the air duct from the cylinder opening 29 to the first solenoid valve VI so that with the first solenoid valve VI in its closed uncontrolled state and with the second solenoid valve V2 actuated to its open state, displacement of piston 27 from right to left in cylindrical bore 26 will cause fresh - (ambient) air to flow into the described system. Similarly, with two solenoid valves V1 and V2 in the same state (valve V2 in the open state and valve VI in its normally closed state), shifting the piston 27 from left to right in bore 26 will cause excess air or gas to be discharged from the system.

Similarly, with valve V2 in its normally closed state and with valve VI actuated to its open state, displacement of piston 28 from right to left will pull out more of Zr '··''' · '^> “* - * · - <-> ·: ·· - '<- ^κ + F-in YPS-inflatable air (and thus deflate) means 19 of the LMA device. And in the same condition with the valve V2 uncontrolled and with the valve VI controlled by the displacement of the piston 27 from left to right, inflated air is supplied to the means 19 of the LMA device.

The control signals required to control valves V1 and V2 are provided by separate outputs, which are derived from the basic program sequence signals from the separate microprocessor means of the controller 60 for adjustment, centering, and reset.

A. 1. System Setup

For the purpose of system setup and centering operations, the control circuit of FIG. 3 is bypassed and the inputs of the stepper motor controller and drivers 47 are controlled by the controller 60 for the stepper motor.

2_5 setup, centering and reset. As shown in FIG. 4, bypassing the control circuit of FIG. 3 is accomplished by operating two single-pole two-position switches 42. Such operation of the switches 42 occurs when the unit is first energized, at which point the setting sequence is initiated. The operation of the stepper motor 33 is controlled during this adjustment sequence by the set, center, and reset controller 60.

Before proceeding with an illustrative description of the automated operation of the control system of Figures 1 and 2, it should be noted that, for practical purposes, the system must be compatible with suitably sized LMA devices for patients of all ages requiring cuff inflatable volumes of £ 9. vary up to 10: 1 between extreme extremes. The sizes currently available for the selection of an anaesthesiologist are as follows:

Velikost 1

Velikost 1,5

Velikost 2,0

Size 2.5 (small infant), 4 cc maximum inflated volume (larger infant), 6 cc maximum inflated volume (small child), 10 cc maximum inflated volume (larger child), 14 cc maximum inflated volume

Velikost 3,0

Velikost 4,0

Size 5.0 (smaller adult), 20 cc maximum inflated volume (average adult), 30 cc maximum inflated volume (larger adult), 40 cc maximum inflated volume.

At present, it is advantageous to design the displacement capacity in the injection molding bore 26 to be substantially 20 cc between the triggering of the limit switches LSI and LS2 at the respective extremes of the overall length L of the piston progression in the bore 26. a displacement capacity of 20 cc realized at full stroke - i.e. a total length L - of approximately 45 mm, which can be considered an illustrative useful displacement range of the system. In addition, also illustratively, for a stepper motor 33, designed to require 1600 pulse steps per revolution of its lead screw 34 and to lead a lead screw (i.e. shift per revolution) of 2 mm, the useful range - total length L - displacement of the piston 27 altogether 36000 discrete pulse increments · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Increments; wherein, for initialization adjustment purposes, the recommended rapid repetition rate of the pulse steps at 5000 Hz to produce a piston displacement rate of 6.25 mm / s. For normal pressure regulating displacement, the recommended slow repetition rate of the pulse steps at 500 Hz should be used to produce a piston displacement rate of 0.625 mm / s. It is explained below that any automatic pressure regulating correction is preferably achieved by a piston displacement increment starting from the center point of the useful total length range L, so that the indicated motor displacement control range is typically performed in the range of 18,000 pulses to the motor 33, a displacement of at least 10 cc in the inflation direction of the LMA device or in the blowing direction of the LMA device, as desired. For automated regulation of inflation (inflation) of the LMA device to the set point pressure, it has been found that this range limitation will serve any of the above LMA device sizes, even when the range of inflation volumes is approximately 10: 1.

C in the above, it was recommended that the system of FIG. 1 and FIG.

has been coupled (at the control port 11 ') to the inflatable means 19 of the LMA device only after carrying out a conventional procedure using a hand held injection means (not shown) to empty the inflatable means 19 for c to introduce the LMA device into the patient; using the same injection means to inflate to a value that the surgeon knows from his own experience to form a properly positioned inflatable seal around the laryngeal inlet and with distal contact engagement with the hypopharynx.

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A preferred method of initially inflating an inflatable ring or cuff 19 of an LMA device is to use an injection means for the anesthetist. Whether or not the inflatable cuff 19 of the LMA device is manually inflated, the system of Figs. 1, 2 and 3 is adapted to quickly take control of the inflatable cuff pressure monitoring to a predetermined point, which of course represents the set point value SP of the desired pressure (e.g. 50 cm water column) as part of display 49. Although the LMA control monitoring system 10 is capable of performing an initial cuff inflating task, such an initial inflation by system 10 may be practical only for cuffs with a smaller volume capacity and is not. currently considered advantageous.

With set pressure threshold .. point value

The SP, selected and created for the system of FIGS. 2 and 3, will begin programmed operation with the controller 60 (set, center, and reset) by controlling the initial setup sequence.

The controller 60, as shown in FIG. 4, includes an algorithm

Ω which actuates the solenoid valve V2 to the open state, leaving the solenoid valve VI in its uncontrolled (and therefore in its normally closed) state. Thereafter, pulses are transmitted at high speed (5000 Hz) through the stepper motor controller and driver 47, which control the motor 33 to move the piston by c, at a high speed from its stowed position, which is determined by the contact 37 cooperating with the limit switch LSO. The piston 27 quickly passes over the overall length L of the piston 27 in the bore 26 in a left-to-right movement. During this procedure, contact 37 controls the limit switch LSI, thereby initiating in the controller and motor driver 47 the counting of the number of pulses that SBHBB is required to move the piston as a function of total length L. This counting is terminated only when contact 37 controls limit switch LS2. at this point, the entire number is entered into the memory of the controller 60 and an operation divided automatically by two is performed, this half value being entered into the memory of the controller 60 and also entered into the memory of the controller and motor driver 47. Thereafter, the motor controller and driver 47 will follow each subsequent command that controls the motor 33 to independently maintain the position of the piston 27.

Then, a signal is sent by the controller 60 to start the procedure in the opposite direction at the same speed until the number of pulses is reached, indicating that the piston 27 has already reached its middle position (or L / 2). Then the solenoid valve V2 is deactivated, which returns it to its normally closed state.

The two switches 42 shown in Figure 4 then simultaneously move from the first (1) position to the second (2) position, allowing the fuzzy logic controller 46 (foggy set logic) shown in Figure 3 to take control engine

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33. The fuzzy logic controller 46 will operate according to the logic rules outlined below. in Table 1, which provide the signal needed to cause the piston 27 to continue to move from left to right until the pressure generated at the front end of the cylinder is equal to the pre-programmed limit point pressure, typically 20 cm of water column; once such a value has been reached, for reasons explained in the following description, the piston 27 is further controlled to continue its operation until the set point value SP is reached.

The controller 60 will then operate the solenoid valve VI, which will bring the solenoid valve VI to the open state.

If the controller 60 (for setting, centering, and reset) failed to receive an indication that the pre-programmed limit point pressure had already been reached, in a predetermined number of steps of the stepper motor 33 (e.g., the pre-programmed limit point pressure to be reached before the number passed) steps required for the piston 27 to advance by one eighth (1/8) of the total length L of the procedure), then an audible and visual alarm will be issued and the system will prevent the system from operating automatically.

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A. 2 Fail-safe mode

The fail-safe mode can be started during normal system operation with a substantial deviation between the redundant pressure sensors. The pressure is redundantly sensed by the pressure transducers P1 and P1, from which the independently measured value of the measured pressure is continuously compared by means of a comparator 40A. A hardware failure alarm will be generated when a difference other than a substantially zero difference is detected between P1 and P2 sensors. This hardware error alert is issued in the form of an audible and visual indication to alert the anaesthesiologist to take manual control of the inflation of the LMA device. Then, within a short period of time after this hardware error warning is issued, the comparator means 40A enters a fault-safe mode in which it closes the solenoid valves V1 and V2 to maintain the pressure ²⁵ within the LMA device cuff.

B. Normal system control

The operation of the fuzzy controller (with fog-based logic) is described by the logic rules below in Table 1. The first two columns in Table 1 • · · www?

Odráž— reflect the previous pressure and the current pressure, each relative to the SP point value. As indicated in Fig. 3B, the time delay between the first and second columns is half a second (1/2 s). The last columns in Table 1 reflect the command that would normally be sent by the fuzzy logic controller 46 to the controller and motor driver 47. Since the stepper motor 33 only operates at low speeds during normal operation, the fuzzy command is sent according to the direction and number (N) of steps. The described pressure regulating process, which is performed by the fuzzy logic controller, preferably performs its role within the range of action defined by the insensitivity range of 0.5 cm water column on each side of the set point value SP.

Table 1

Operation of controller 46 with fuzzy logic

Previous Present current The decision in steps current pressure in pressure in relation to (N) and direction relationship to the set set point point value value high high high number of steps, back medium high high number of steps, back high medium Low number of steps back medium medium minimum number steps, two-way low medium Low number of steps forward

low low high number of steps, forward medium low high number of steps, forward

C. Typical course for anesthetized patient

Giant. 5 illustrates the respiratory pattern that the system of the present invention used for both pressure control. the cuffs 19 of the LMA device as well as for monitoring the inflation pressure of the LMA device. In this example, the patient is subjected to surgery and is mechanically ventilated, i.e., patient ventilation is a result of the overpressure exerted by the air tube 14, also referred to as intermittent overpressure ventilation or IPPV. Giant. 5 illustrates the ability of the device of the present invention to monitor oscillations (fluctuations) around a set point SP value (50 cm water column in this example), such oscillations occurring at a rate of about 12 cycles per minute, the usual respiratory cycle of a normal anesthetized adult patient.

It has been found that such respiratory flow through the air tube 14, whether spontaneous or through IPPV, will have the effect of causing the LMA device cuff 19 to undergo regular compression / expansion cycles. One of the objectives of the system of the present invention is both to measure the size of the compression / expansion cycles and to detect deviations from these compression / expansion cycles that can be detected to indicate a painful stimulus. Although there is an overall stretch in Figure 5

The signal envelope shown (as shown in Fig. 5 and as will be explained in more detail below in describing the automatic scaling) is not yet any indication of the painful stimulus in Fig. 5. 5A provides an example of a patient experiencing a pain stimulus that the system of the present invention will detect and alert to through the alert procedures discussed in more detail below.

The graph depicted in FIG. 5A is an illustration of the interacting forces in the agitation movement in response to a painful stimulus of this nature. First of all, it should be noted that the system of the invention will be in its normal control mode in which it does what it can by sampling (at 0.5 second intervals) the measured pressure (e.g., pressure sensor P1) relative to the set point value. SP, utilizing these values to determine and perform correct piston displacement 27. A pattern of neuromuscular pressure deviations following a painful stimulus and piston displacement that will be induced and may not be within the capability of the described mechanism may therefore create a distorted pattern of measured pressures, while the control mode is trying to reset itself. Still further, the conventional regulatory regimen and neuromuscular system of a patient will attempt to adapt to changing and changing conditions that may result from the patient's neuromuscular response to a deepening (ripping) additional dose of anesthetics. Monitoring functions

Giant. 3, 5 and 5A and the graphs and tables of FIG.

6A, 6B, 6C, and 6D serve to illustrate two automatic techniques in which the apparatus of FIG. 1, FIG.

and Fig. 3 may alert the anesthetist that during an anesthetic patient's surgical procedure, the patient issued an early neuromuscular indication of a painful stimulus that the patient's current level of anesthesia was unable to unblock, even though the patient is still quiet enough to be unconscious or otherwise insensitive to painful stimuli. Such neuromuscular indication demonstrates to the operating anesthesiologist that the patient is contracting the larynx or hypopharynx muscles, a phenomenon indicating the initial phase of the patient's awakening process with potentially serious consequences if surgery is not yet complete.

Although it is known that patients under the influence of general anesthetics become insensitive to painful stimuli, it has been found that such sensitivity is particularly active and traceable in the muscular systems surrounding the laryngeal entry and the hypopharynx region. Furthermore, it has been found that such activity of these muscle systems will vary with the depth of anesthesia and can be monitored by pressure fluctuations in the inflated cuff 19 of the LMA device having elastically loaded continuous contact with these muscle systems. More precisely, the anomalous pressure values detected in the output of comparator 40A are recognized by comparators 57B, 58C, and 59D in Figure 3 to generate output alerts A1 and A2. Inflated ring or cuff 19.

5 of the installed LMA device is therefore a means of early detection of the localized neuromuscular response, which is deducible from the sudden response of the regulatory function of the described system, since the same can be observed to occur in the disturbed and irregular pattern of pressure measurements of FIG. 9 9 • 9 9 9 «99 9 · 99 brackets and description identify the period of painful stimulus due to an event occurring during surgery.

Giant. 7 shows empirical values of varying pressure fluctuations that have been observed to occur as c

the anesthesiologist intentionally allowed the patient to partially awaken from the depth of anesthesia, and it should be understood that the graph similar to the graph of Fig. 7 was available in real time on display 49 during the surgical procedure. Pressure changes are displayed on the ordinate in cm of water column with the set point value SP selected for 60 cm of water column. Giant. 7 depicts events that took place (in the temporal sense) toward the conclusion of a surgical procedure in which a patient (patient 5) was anesthetized with a continuous supply of propofol, a common and popular anesthetic.

In Fig. 7, three specific time periods are discernible, each of these intervals corresponding to the initiation of a change in the amount of anesthetic administered to the patient 5. In the first of these time periods, starting at 68 minutes, continuous administration of propofol was stopped.

And in the following remainder of this first period, it is easy to observe the area that is in contact with the cuff. 19 LMA device, a significant increase in larynx / pharynx muscle activity (larynx / pharynx).

The correlation of increased muscle activity (in the larynx / pharynx region) with the depth of anesthesia of the patient has been found to be an important advantage in maintaining the correct levels of anesthetics during surgical and other interventions. The use of LMA equipment and monitoring equipment provides

The means by which such observations can be easily performed with the added benefit of not exposing the patient to another invasive device.

During the second period indicated in Fig. 7, which begins at approximately 72 minutes, the anesthetist resumes administration of propofol. The third period, shown in FIG. 7, starts at approximately 73 minutes and identifies the point at which propofol administration was stopped again and the patient was then allowed to fully awake. Note that there are no additional readings after approximately 82 minutes, since the LMA device was removed from the patient's laryngeal area at this time.

The events shown in Fig. 7 provide conclusive evidence that the monitoring system of the present invention operates at a level of sensitivity that allows the detection of muscle activity.

indicating the awakening sequence.

D.1 Automated Alerts

Two techniques recommended for the automated interpretation of the anomaly described in Figure 5A are described in more detail below.

These alerts can be monitored by an anaesthesiologist for immediate or early detection of a pressure anomaly that has been traced as a symptom caused by the early phase of consciousness during the patient awakening process.

Both techniques rely on creating fluctuation limits (thresholds) on each side of the normal respiratory pattern and comparing the pressure in the LMA device (cuff 19) with these limits; these limits are shown as the upper and lower thresholds E1 and E2 respectively in FIGS. 5 and 5A, and are referred to as the anesthesia check window. As shown in Fig. 3, the thresholds are * · • · • ·

E1 and E2 values automatically compared to each pressure signal fluctuation to determine anesthesia level A1 and A2 warnings. The serving anesthesiologist is able to individually select, i.e. change, the thresholds E1 and E2 via the monitoring device 10. Alert Al is an immediate type alert that is triggered whenever the respiratory pattern deviates above or below the alert window to control anesthesia that is bounded by the thresholds El and E2. The initial Alert Alert is triggered by one deviation from the Alert Anesthesia Alert window. The Al warning will be presented to the anesthetist in audio form. Once alerted, the anesthetist is prompted to perform an immediate corrective response, such as by increasing the strength of the anesthetic being administered to the patient.

Alert A2 is a velocity-based alert that is determined by (i) the ET value relative to the alert window (explained below) and (ii) by the calculated average (Y) based on consecutive samples of the detected LMA device inflation pressure waveforms, wherein samples are taken for each successive 0.1 second sampling interval and are integrated and stored at an absolute value in the perimeter of the word count field as shown in Figure 3; wherein each of the 25 absolute values is considered in its sampled size relative to a stable base, which is preferably a set point value, as shown in Figures 6A and 6B. If the mean value, ie the sum of the last consecutive thirty-two integrated samples, divided by 32 (see block £ 1 for

2Ω of Fig. 3A), exceeds the ET value, as further explained below, ·· · 4 4 · · 4444

4 4444

44 4 44444 * · 4 4 4 44 4 4

444 44 444 444 44 ·· A A2 alert, such as CHECK ANESTHESIS, will be issued to the anesthetist through a combination of visual and / or audible signals. The anaesthesiologist is further advised to perform an immediate corrective response, such as by increasing the strength of the anesthetic being administered to the patient.

The ET value is calculated by adding the absolute values of the threshold values E1 and E2 and dividing this sum by the chosen constant k, ie:

ET = 1 / k [| E11 + | E2 |] where k is a selected value in the range of 3 to 6 (and preferably 4), where k = 4, ie divided by 4, creates a practical safety factor through which the CHECK ANESTHESIS alert is reliably issued, even if the immediate type Al alert may not be issued.

As shown in Fig. 3, at the end of each 3.2 second sampling period, the oldest sample is discarded and the last sample is included in the new mean value calculation for the subsequent comparison of 32 samples with the ET value.

For example, in the anomaly shown in Figure 5A, which is an illustrative example of a pain stimulus event observed during surgery, findings that are the major deviations from the normal situation shown in Figure 5 will be evident. If the initial sample exceeds one of the alert window limits, the first alert A1 will be triggered, and the second alert A2 may not be immediately triggered.

Creating integration and median values as above fcfc fcfc fcfc fcfc fcfcfcfc fcfc fcfcfc description may result in an alert A2 CHECK ANESTHESIS, even although the threshold transition needed to issue the first Al alert has not occurred. In addition to these two warnings, the anesthesiologist can follow the ongoing development in the form of a percentage count, which can be displayed as shown in Fig. 1B, which will be discussed in more detail below under the heading Characters of the Display.

Although the graph in Fig. 5A reflects the interaction of different responses, it should be explicitly noted that once 1 Ω of such responses are detected, major transient deviations from the set point SP value are eliminated at approximately 30 seconds interval by prompt administration of an additional anesthetic.

D.2 Display features

The display 49 includes a time window through which a continuously varying signal, such as that shown in Fig. 5, Fig. 5A, Fig. 6B, Fig. 6D, and Fig. 7, shows the last one full minute of regulated pressure

2Q changes entering the window at its left edge and exiting the visible field of the window at the right edge.

An additional method for displaying the results of the above-described integration / summation process (mean) is shown in Figures 1A and 1B, wherein the two displays over time indicate progression from the deeper level of anesthesia shown in the first example of Figure 1A to an initial level of awakening approximation, as shown in the second example of FIG. 1B. The display preferably consists of a bar chart which illustrates, for example, in percent, the output of the progressively integrated function described above. Initial · 0 * · 0 0 0 «00 ·· 0 · · · · · 0 0 ·

0 0 «0 000 • 00 0 000000 000 0 · 0000

The value of this continuously updated display is created for each individual patient, preferably after the anesthetized patient is placed on the operating table by the surgeon in a ready position for surgery. A parameter equivalent to 100% of the reading displayed on the display will be equal to the full ET value, at which time the CHECK ANESTHESIS warning will be issued.

For use by an anaesthesiologist and / or other person observing a surgical procedure, the ability to connect a separate microprocessor or other data presentation means to the computer interface 41 is also provided, ensuring monitoring, recording and analysis of indicators in the system on a separate electronic medium, for example when much more complex records and analysis required.

D.3 Scaling the alert window automatically

It has been found that the monitoring function of the system of the present invention can be made much more efficient by allowing automatic reduction

2q (or automatic scaling) of the alert window size control anesthesia, which provides the advantage of setting a threshold value (i.e., thresholds E1 and E2) for a faster alert and thus the advantage of more accurate anesthesia level monitoring. To perform such automatic scaling of the anesthesia check window, both upper and lower peak amplitudes are sampled from at least eight consecutive waveforms, these samples are averaged, and mean values for the upper and lower peaks are determined. Two are used to verify these peak values

3Q controls; whereas all eight upper and lower limits that are sampled must be obtained within the same two-minute tititi • titi • three • three titi • titi

f • The three titers The three titers of the three sample periods and small oscillations that otherwise can be identified as peaks can be eliminated through operator input with a preset minimum amplitude.

These upper and lower peak amplitudes define essentially an envelope that usually shrinks as the patient undergoes active pressure ventilation (IPPV) as the patient sinks into increasingly deep anesthesia. Considering the usefulness of adjusting the alert thresholds in terms of monitoring the envelope of decreasing amplitude (or size), it must be remembered that the patient's respiratory pressure is usually lowered as the patient is increasingly undergoing anesthesia. Limiting thresholds (i.e., thresholds E1 and E2) of the alert has been found to be an effective and desirable procedure for automatically adjusting the sensitivity of the monitoring device so that the detection of pain response continues regardless of envelope size reduction.

As a safety measure, the preferred device according to the invention allows the automatic scaling feature only to reduce and not to automatically enlarge the anesthesia warning window. The amount by which the automatic scaling can change the thresholds E1 and E2 is fully adjustable between zero and one hundred percent, with the default setting being fifty percent. Interestingly, such automatic scaling often causes the thresholds E1 and E2 to no longer be symmetrical about the set point value SP, as is the case, for example, in the alert window shown in FIG. 6B.

····· · * ·· · ♦

9 · · φ φ φ φ φ φ φ φ · · · · · · · · · · · · · · · »

D. 4 Re-centering control system

As described above, the system of the present invention will automatically compensate for leaks and increments in the monitored inflatable-air. Since the stepper motor controller and driver 47 maintains the number of directional commands given to the stepper motor 33, the controller and motor driver 47 are able to indicate and will also indicate when the piston 27 has already reached the end of its travel. Such indications will actuate switches 42 to position 1 and initiate the reset, control, centering, and reset reset function. Depending on the reset command sent by the controller and motor driver 47, i.e., when the anomaly condition requires replenishment or exhaust of the piston air, appropriate action will be taken by controller 60. For example, when the reset function requires air to be added to the system, controller 60 will be deactivate the solenoid valve VI, which returns it to its normally closed state; (ii) activate solenoid valve V2 to the open state; and (iii) sending appropriate signals to the stepper motor controller and driver 47, causing the piston 27 to be driven by the high speed stepper motor 33 to discharge excess air (or, where appropriate, to take additional fresh air) through the end 44. The memory of the controller 60 will maintain, from the system start-up procedure described above, the number of pulses required to move the piston 27 to its center position (L / 2).

In the normal monitoring and control operation of the disclosed system, there will be few challenges for large displacements of the piston 27. However, large displacements may, of course, occur, for example by contacting the surgical knife with the inflated cuff 19 of the LMA device. This condition will be detected by the system, requiring the continued supply of either additional or limited inflatable air depending on whether the contact 37 cooperates with either end switch LS1 or end switch LS2, indicating that the piston 27 has already reached the end of its travel. Such a limit switch signal causes: (i) a bypass of the control circuit of FIG. 3 to the switch 42; (ii) sending an alert to the anesthetist, for example in the form of an audible alert with 10 visual displays of the message to check for leaks; and (iii) initiating a reset function of the controller 60 as described above.

The above description emphasizes the added advantage of an automated device in which, as described, the air volume in the cylinder 26 will be restored at an interval of approximately 3.6 seconds, which is considerably faster than is normally possible with manual operation. Despite this advantageous automatic refresh time, the pressure settings made by the system are sufficiently discrete to allow pressure control

0 the smallest cuffs of the LMA device without causing undesired excess pressure inside the small volume.

All of these activities are automatic, such as alerts or warnings that are part of providing a set point pressure value that circumstances 25 may require for a given patient or that is foreseen for a patient with a given size of LMA device.

Conclusion

It is evident that the device described and the method of its use achieve all the objectives set and operate * 4

444 4 4 4 444

444 44 444 444 44 44 as a LMA cuff pressure controller, as a leak monitoring and remedy device, as a monitor for any painful stimuli to the patient's neuromuscular system when the patient is anesthetized during surgery, and as a monitor to prevent the patient from getting out z under the effect of muscle relaxation while not adequately anesthetized. More precisely:

1. The equipment is controlled by a microprocessor unit that performs, but is not limited to, all tasks, including diagnostic, engine and valve control and control, and pressure measurement.

2. The device includes a graphical display and control unit, as well as an interface for advanced monitoring and control, allowing data evaluation through 15 [different commercial software packages].

3. The device provides instantaneous cuff pressure values of the LMA device via redundant pressure sensors that are pneumatically coupled to the inflation line of the LMA device cuff. For safety reasons, the pressure measurement is carried out by means of redundant sensors, and their automatic comparison is carried out continuously.

4. The device typically operates with the same volume of air, trying to maintain a set point pressure value for inflating the LMA device cuff, and for each LMA device cuff pressure measurement, a deviation from the set point value causes the piston to move in the down direction to zero (or 0) deviation of the measured pressure from the set point pressure value.

• 9 • 9

999 9 99 99 99 • »» ··

9 · 9

9

Thus, the device is detachably coupled to the inflatable / deflated air lines of the LMA device to allow normal LMA device installation procedures to the patient, without relying on any of the automatic features of the device. As a result, the patient can be prepared for operation by installing an LMA device with an inflated cuff and fully checked to ensure that it has been properly installed before the patient enters the operating room, by relying on a non-return valve to maintain the inflation pressure before connecting the patient and the inflated cuff of the LMA device.

6. If for any reason the system is not working or is not working properly, the system will be put into a fail-safe mode with the working valves reset to their normally closed condition, maintaining the inflation pressure of the LMA device.

7. In the normal control mode of the device, the system pressure is sampled every one-tenth (1/10) of a second with sufficient time to perform the evaluation with respect to the set point pressure value and to deliver a series of pulses to move the piston to achieve a measured pressure correction a basically set point pressure value. Normal control occurs when the pressure sample evaluation exceeds the ± 0.5 cm water column threshold from the set point value.

8. It is important to emphasize that the normal operation of the described system with LMA equipment exhibits significant advantages resulting from the fact that the system operates in

3q by substantially enclosed air volume. Increasing the measured pressure quickly causes a shifting of a portion of the air volume from the LMA cuff

Č '.- Č- ·.

• * 000 • 00 * 0 »0 0 • · • · • 0 0 0 • * 0 0 0 0 0 0 • »0 • • «0 t 0 0 • 0 · • • 0 0 • 0 • 0 0 ·· t. · · • 0 00

the device and to the volume defined between the piston with the front end of the cylinder; and this volume of air will be returned to the cuff of the LMA device substantially as soon as it is determined that the measured pressure has dropped. This sharing of the same air volume always applies to moments when, due to a leak or some other unexpected event, the piston reaches the end of its travel, as monitored, for example, by the operation of a position counter maintained in the controller and the stepper driver. at this point the piston will be displaced with the air vent or fresh air as required by the situation, all of which means that the LMA device cuff can maintain its inflation pressure.

9. Once stabilized, the described 1C system is found to be very sensitive to very small pressure changes (in-line 1/16 cm water column) and can be fast and accurate in its response without loading the monitoring function with a time constant or hysteresis error. It can be assumed that such a response is achieved due to the described stepper motor and on.

guide screw in combination with conventional control displacements within a substantially enclosed air volume. Relying on a substantially enclosed volume of air is converted to incorporate only one time constant when increasing or decreasing the internal pressure in the cuff of the LMA device.

'25

10. As an aid to the anesthesiologist and during patient surgery, the system described allows several concurrent algorithms to process, in real time or near real time, an anesthetic patient initial, beginning and totally independent of the will, muscle signs of waking from induced

4444 • 4 4 • 4 44 44

• 4 4 · · 4 4

444 44 44 sleeping and / or paralyzed conditions, through a sensitive response to muscle activity observed around the patient's laryngeal entry and / or in contact with the patient's hypopharynx. In doing so, the anesthetist's audible and visual warnings are provided to detect the onset of the patient's awakening, at the appropriate time to control the anesthesia and to take corrective action without the patient's awakening. In addition, the present system has an inherent adaptation capability to improve the accuracy of anesthesia depth loss detection as it gradually narrows its focus to a predetermined safety margin when evaluating monitored fluctuations in the inflation pressure of an LMA device.

11. The monitoring function of the disclosed system may be useful in detecting and securing a means of securing against a situation in which a patient receiving both anesthetic and a separate muscle relaxant (e.g. atracurim or vecuronium) has an anesthetic consumed while remaining immobile due to the overwhelming effect of only the muscle relaxant. Such a situation is, of course, known to be considerably unpleasant due to the inability of the patient to demonstrate that the patient is experiencing the full effect of surgical procedures. A monitoring system with an LMA device may be useful as a safeguard against such an event due to the more limited effect of some muscle relaxants on the pharyngeal sphincter muscles with which the LMA device cuff 19 is necessarily in contact while having the ability to monitor muscle activity. the contraction of the pharyngeal sphincter muscles does not change during partial paralysis caused by the conventional muscle relaxant. See Ericsson et al., Determining Pharyngeal Function at Rest and during Swallowing in Partially Paralyzed Persons; Anesthesiology, Volume 87, Number 5, November 1997.

12. It should be further noted that although the monitoring and other detection functions of the disclosed system are described

In conjunction with the LMA device inflation response, this association with the LMA device is merely illustrative of the use of a suitable inflated device within the pharyngeal cavity to respond to changes and to provide a suitable muscle activity alert in the area of contact ^; inflated material with one or more areas of muscle activity.

13. It should also be noted that advantageous

numerical values given in this description, such as 4, 8, and the like, are merely illustrative values that have been selected as integer multiples of 2 due to the advantageous association with the 15 operation of the digital system.

Claims (14)

PATENT CLAIMS An apparatus (10) for automatically monitoring the level of unconsciousness of a patient (13) during surgery on a patient, the patient having an inflatable device (19) having a wall in contact with at least a portion of the pharynx of the patient, and wherein the inflatable device has a flexible tubular inflatable (11) accessible from the outside of the patient, comprising: a) sensing means comprising a pressure sensor (P1, P2) detachably connectable to an inflatable lead to produce an electrical output signal responsive to instantaneous sensed inflatable pressure as a function of time during surgery; b) means comprising injection means having a cylinder (26) with a front adapted to detachably connect (11 ') to the inflatable inlet and a piston (27) in the cylinder to define a substantially constant volume of inflatable air within the inflatable device, inflatable inlet and front thereof a cylinder, wherein the piston is movable relative to the cylinder to change the air volume ratio between the inflatable device and the front of the cylinder; c) comparator means for comparing the sensed pressure to a reference value and thereby determining any deviation from the reference value; and d) regulating means comprising a reversible actuating means (33) for moving the piston in the cylinder and thereby restoring the pressure to a reference value. • · · · · · · · · · · · · · Device according to claim 1, characterized in that the installed device is an LMA device (12) comprising an air tube (14) with a mask (16) and an inflatable cuff (19 at its distal end for sealing engagement around the laryngeal inlet (21). ) of the patient, with a connection to the patient's lungs through the air tube and through the mask, a flexible inflatable connection to the inflatable cuff. The apparatus of claim 2, comprising microprocessor means (60) programmed to form separate upper and lower tolerable sensed air pressure limits, and to provide an output pressure alert alarm that exceeds one of these limits. The apparatus of any one of claims 1 to 3, further comprising a display means operatively coupled to the sensing means to produce an image of the sensed inflation pressure as a function of time. The apparatus of claim 4, wherein the display means comprises a visual output that displays, for a predetermined time interval, the pressure amplitude as a changing ordinate continuously passing from one to the other end of the time interval with the current and nearest past pressure detected at one edge. and with a predetermined upper and lower tolerable limits as separate horizontal lines above and below the sensed inflation pressure display. Apparatus according to any one of claims 1 to 5, characterized in that the reversible drive means comprises a motor (33) coupled to reversely drive the lead screw (34) and nut means (34 ') screwed onto the lead screw and guided longitudinally. and secured against rotation and coupled for direct longitudinal displacement of the piston within the cylinder. The apparatus of any one of claims 1 to 5, wherein the reversible drive means comprises a digitally controlled stepper motor (33), wherein the pressure responsive output is in the form of a first digital signal, the reference value is in the form of a second digital signal, and the comparator means comprising a microprocessor programmed to supply digital signals to control the motor. Device according to any one of claims 1 to 7, characterized in that the front of the cylinder is removably connectable to the inflatable inlet via a valve (VI) controllable between an open state to allow the connection between the inflatable device and the cylinder front and closed condition. Apparatus according to claim 8, characterized in that it also comprises a second valve means (V2) operatively connected to the front of the cylinder and operable between the open state to allow communication with the ambient air and the closed state. The apparatus of claim 9, wherein each valve is a normally closed solenoid valve, wherein the first valve has an electrical connection to the control means to enable pressure control of the inflatable device and the second valve has an electrical connection to the control means to enable automatic discharge. or supplying air while maintaining a substantially constant shared common air volume within the inflatable device and the front of the cylinder. I · · The apparatus of claim 10 comprising air supply means for injecting a predetermined amount of ambient air into the cylinder, the air supply means comprising: limit switch means (LS2) generating an electrical signal for the sensed condition indicating a displacement of the piston to a predetermined proximity to the front of the cylinder and corresponding to the forward limit of the permissible piston travel; and means comprising a microprocessor responsive to a signal sensed proximity to the piston, the microprocessor being programmed to: (i) to return the first solenoid valve (VI) to its normally closed state; (ii) to operate the second solenoid valve (V2). into the open. a condition and then for actuating the drive means for a predetermined return stroke, which brings a fresh dose of ambient air to the cylinder; and (iii) to deactivate the second solenoid valve and allow the comparator means to reset the set point pressure value within the cylinder before reactivating the first solenoid valve and returning the comparator means to its inflation pressure control function to its set point value. * · The apparatus of claim 10 or 11, comprising an air ejection means for expelling a predetermined amount of air from the cylinder, the air ejection means comprising: limit switch means (LSI) generating an electrical sensed condition signal indicative of moving the piston to a predetermined proximity to the rear end of the permissible piston travel; and means comprising a microprocessor responsive to a signal sensed proximity to the piston, the microprocessor being programmed to:. (i) to return the first solenoid valve (VI) to its normally closed state; (ii) for actuating the second solenoid valve (V2) to the open state and then actuating the drive means for a predetermined forward stroke, causing a predetermined displacement of air from the cylinder; and (iii) to deactivate the second solenoid valve and allow the comparator means to reset the set point pressure value within the cylinder before reactivating the first solenoid valve and returning the comparator means to its inflation pressure control function to its set point value. 0 Device according to any one of claims 1 to 12, characterized in that the displacement volume in the cylinder is of the order of 20 cc. 14. A method of monitoring a patient's unconscious level during 5 '. from a surgical procedure on a patient, wherein the patient has an inflatable device (19) having a wall in contact with at least a portion of the pharynx of the patient, using the device of any one of claims 1 to 13.