JPS6363472A - Anesthetic degree detector - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a device for detecting the depth of anesthesia in a living body.

Conventional technology When anesthetizing a living body during surgery, the appropriate anesthesia is generally determined based on the physiological information of the living body and the surgical situation, to avoid the inconvenience of awakening the living body due to excessively shallow anesthesia or the inconvenience caused by excessively deep anesthesia. In order to maintain a suitable depth of anesthesia, it is necessary for the anesthesiologist to precisely manually adjust the rate of anesthetic mixed into the inspired air. In such anesthetizing a living body, an anesthesia depth detection device that accurately detects the anesthesia depth of the living body is desired. Regarding this, the depth of anesthesia can be determined by measuring the brain waves of the living body,
Various devices for detecting blood pressure values, heart rate, etc. have been studied in the past.

Problems to be Solved by the Invention However, such conventional devices have problems such as insufficient accuracy in determining the depth of anesthesia. For example, when detecting the depth of anesthesia by analyzing brain waves, even if the depth of anesthesia based on brain waves is the same,
In some cases, the anesthetic concentration in the arterial blood varied by as much as 30%.

In addition, unless the accuracy of the depth of anesthesia as feedback information is sufficient, variations in control results are unavoidable when performing manual adjustment or automatic control of the depth of anesthesia.

Means for Solving the Problems The present invention has been made against the background of the above circumstances.
The gist thereof is to provide an anesthesia depth detection device for detecting the depth of anesthesia of a living body anesthetized by mixing an inhalation anesthetic into the breath of the living body, which includes fa) anesthetics contained in the breath of the living body; (b) an anesthetic concentration detection device that continuously detects the concentration of an inhalation anesthetic and outputs a signal that fluctuates in synchronization with respiration; and (b) a terminal period detection means that detects the terminal period of the exhalation period in respiration of the living body. and (C) an anesthesia depth that determines the concentration of the inhaled anesthetic at the terminal period or a value based thereon among the signals output from the anesthetic concentration detection device, and outputs this as a value indicating the anesthesia depth. and determining means.

Operation and Effect of the Invention With this structure, the anesthesia depth determining means detects the highest concentration peak of carbon dioxide gas detected by the carbon dioxide concentration detection device, and at the same time detects the signal output from the anesthetic concentration detection device. Since the concentration of the inhaled anesthetic in the end expiration corresponding to the peak value of carbon dioxide gas or a value based on this is output as a value indicating the depth of anesthesia, it is possible to grasp the depth of anesthesia more accurately than before. can. That is, end-expiration, which is the gas at the end of exhalation, can be considered as gas in the alveoli, and the concentration of the inhaled anesthetic contained therein corresponds to the concentration of the anesthetic in the arterial blood, and the concentration of the anesthetic in the blood corresponds to the concentration of the anesthetic in the blood. is the anesthetic concentration in brain cells, which is closely related to the depth of anesthesia in the living body (
This is because it corresponds to the anesthetic partial pressure).

Here, the terminal period detection means preferably continuously detects the carbon dioxide concentration contained in the exhaled breath of the living body, and outputs a signal indicating the carbon dioxide concentration that changes in synchronization with respiration. The device includes a detection device and a maximum carbon dioxide concentration time detection means for detecting the maximum time of carbon dioxide concentration based on a signal output from the carbon dioxide concentration detection device.

The terminal period detection means includes a thoracic impedance detection device that continuously detects changes in thoracic impedance of the living body, and a thoracic impedance detection device that detects a minimum period of thoracic impedance based on a signal output from the thoracic impedance detection device. The minimum impedance timing detection means may also be included.

Furthermore, the terminal period detection means may directly or indirectly detect the terminal period of the exhalation period of a ventilator that forces the living body to breathe, and output a signal indicating the terminal period. .

EXAMPLE Hereinafter, an example of the present invention will be described in detail based on the drawings.

Is the depth of anesthesia intransitive in Figure 1? 1) This shows the configuration of the device, and the patient 10 has an electric respirator 12 connected to the pipe 1.
), and operates according to the breathing rate and ventilation amount according to commands from the respiratory controller 14, and forcibly sends inhaled air corresponding to the ventilation amount to the patient 10, and expels exhaled air. The exhaled air from the patient 10 is sent exclusively to the carbon dioxide gas sensor 16 and the anesthetic agent concentration sensor 18 via the pipe 13 for sending out the exhaled air, and the carbon dioxide gas and the concentration of the inhaled anesthetic in the exhaled air are detected there. ing.

The carbon dioxide sensor 16 detects the concentration using the absorption spectrum of carbon dioxide existing in the infrared region, and is composed of an infrared gas analyzer equipped with a heating tube, for example, as shown in FIG. In Figure 0, the infrared light emitted from the light source device 20 passes through the convex lens 22.
, the exhaled air passes through the glass cell 24, the infrared transmission filter 26, and the convex lens 28, and is detected by the photocell 30. The photocell 30 outputs a signal indicating the intensity of infrared rays having an absorption wavelength unique to carbon dioxide that has passed through the glass cell 24, and this signal is amplified by an amplifier 32. The magnitude of the infrared transmission signal SC output from this amplifier 32 is inversely proportional to the concentration of carbon dioxide contained in exhaled breath.
As shown in (a) of the figure, it changes in synchronization with breathing. In this figure, the vicinity of the upper peak indicates the initial expiration where the carbon dioxide concentration is low, and the vicinity of the lower peak indicates the final expiration where the carbon dioxide concentration is high. This is because during ventilation during ventilation, the same components as inhaled air remain in the dead space, which is a part of the mouth, nose, and trachea that does not participate in gas exchange in the alveoli, and are expelled at the beginning of exhalation. This is because it will be done.

The anesthetic concentration sensor 18 is equipped with an infrared gas analyzer equipped with a heating tube that detects the concentration using the absorption spectrum of the inhaled anesthetic in the infrared region, as described above. In FIG. 4, infrared rays emitted from a light source device 36 pass through a convex lens 38, a glass cell 40 through which exhaled air passes, an infrared transmission filter 42, and a convex lens 44, and pass through a photocell 4.
Detected by 6. The photocell 46 outputs a signal indicating the intensity of infrared rays having an absorption wavelength specific to the inhalation anesthetic that has passed through the glass cell 40, and this signal is amplified in an amplifier 48. The magnitude of the infrared transmission signal SM output from the amplifier 48 is inversely proportional to the concentration of the inhalation anesthetic contained in exhaled breath, and changes in synchronization with respiration, for example, as shown in FIG. 3(b).

On the other hand, a lower peak detection circuit 50 for detecting the lower peak of the infrared transmission signal SC;
A depth of anesthesia output circuit 54 is provided with a gate circuit 52 that is opened by a zero output signal. Since a signal indicating the lower peak value of the infrared transmission signal SM, that is, an anesthetic concentration signal SSM indicating the concentration of the inhaled anesthetic in the end expiration, is outputted through the gate circuit 52, in this embodiment, the lower peak detection circuit 50 corresponds to a carbon dioxide gas concentration maximum time detection means for detecting the maximum time of carbon dioxide gas concentration, the carbon dioxide gas sensor 16 and the lower peak detection circuit 50 correspond to a terminal time detection means, and the gate circuit 52 corresponds to an anesthesia depth determination means. do. The anesthetic concentration signal SSM is supplied to the anesthesia depth indicator 55, which determines the anesthesia depth determined based on the inhalation anesthetic concentration in the end expiration or the inhalation anesthetic concentration in the end expiration from a predetermined relationship. The index value represented is displayed. FIG. 3(d) shows the opening operation of the gate circuit 52, and the anesthetic concentration signal SSM indicates the concentration of the inhaled anesthetic during end expiration, which is the final period within the expiration period. The concentration of the inhaled anesthetic in the end expiration indicates the solubility of the inhaled anesthetic contained in the gas in the alveoli, and corresponds to the concentration of the anesthetic in the arterial blood. The concentration corresponds to the anesthetic concentration in brain cells, which is closely related to the depth of anesthesia in the living body. In addition, Fig. 3 (al and (
In bl, the infrared transmission signal SC and the infrared transmission signal SM are flat during the inhalation period, but this is because end exhalation remains in the pipe 13 that exclusively sends exhalation from the respirator 12. Further, when the carbon dioxide sensor 16 and the anesthetic concentration sensor 18 are provided in the pipe 1), the gate circuit 52 is opened only at the end of the exhalation period, as shown by the broken line in FIG. 3(d).

The anesthesia depth setting device 56 is manually set with an appropriate anesthesia depth determined from physiological information of the patient 10 and the surgical situation, that is, an anesthetic concentration (%) contained in the final exhalation. The anesthesia depth controller 58 is the anesthesia depth setting device 5
Depth of anesthesia set in step 6 and anesthetic concentration sensor 18
The drive circuit 60 compares the actual depth of anesthesia indicated by the anesthetic concentration signal SSM from
A control signal SS is output to the anesthetic mixing device 62 via the anesthetic mixing device 62. This control signal SS instructs the rate of anesthetic mixture in exhaled breath supplied to the patient 10, and specifically represents the drive rotation angle of the pulse motor 72, which will be described later. The anesthesia depth controller 58 adjusts the concentration of the inhalation anesthetic at the time of anesthesia induction to 3 to 10%, and to 2 to 3% when maintaining the anesthesia depth. In order to prevent excessive concentration in a transient state, the control equation is provided with a limiter that limits the value to about 10%.

In the anesthetic mixing device 62, as shown in FIG. The inhalation anesthetic is supplied to the mixer 70 through a flow control valve 74 and an inhalation anesthetic vaporizer 76 driven by the anesthetic agent. The mixer 70 mixes the mixed gas with a gas containing saturated vapor of the inhalation anesthetic from the inhalation anesthetic vaporizer 76 and supplies the mixed gas to the ventilator 12 as inspiratory air. The mixed gas of oxygen and laughing gas delivered from the oxygen cylinder 64 and the laughing gas cylinder 66 is mixed in advance at a ratio of about 4:2 by the manual control valves 78 and 80, but this is expected to have a secondary effect. Therefore, the inhalation anesthetic vaporizer 76 is configured to include, for example, a so-called C0pper kettle (a porous bronze sintered plate) and a container for storing the inhalation anesthetic. copper kett soaked in
This is to generate saturated vapor at the current liquid temperature of the inhalation anesthetic in the gas sent out through the inhalation anesthetic. Therefore, by controlling the flow rate of the flow rate control valve 74, the concentration of the inhalation anesthetic in the inspired air is adjusted. In this embodiment, sevoflurane is used as the inhalation anesthetic.

This sevoflurane is shown below.

Chemical formula: CHtP-0-CH(C)13) Chemical name: fluoromethyl-1+ L 1+3.3
．． 3-hexafluoro-isopropyl e
ther molecule 1:200 Boiling point: 58.5°C Liquid specific gravity: 1.505g/d Vapor pressure: 157 torr (20°C) Blood/gas partition coefficient 1.59 (37°C) MAC: 2.0 (monkey) The above sevoflurane As is clear from its blood/gas partition coefficient, it has superior anesthesia induction and wakefulness compared to conventional inhalation anesthetics, and it also has less variation in anesthesia depth, making it easier to adjust the depth of anesthesia. She is also excellent in terms of sex. This fact is shown in the experimental results shown in Table 1. This experiment compared the MAC values and their variations for multiple guinea pigs with the sevoflurane and the well-known enflurane (molecular weight = 185, boiling point: 56.5
℃ and blood/gas partition coefficient: 1.9).

Table 1 However, X is the average value of MAC, and σ is its standard deviation.

Returning to FIG. 1, the ventilation volume is set in the ventilation volume setting device 82. Since the ventilation volume required for the patient 10 is closely related to the carbon dioxide concentration in the end expiration, in this embodiment, the ventilation volume is set in the ventilation volume setting device 82. The carbon dioxide concentration (%) inside is set. The respiratory controller 14 determines whether carbon dioxide gas is present in end expiration based on the signal SC supplied from the carbon dioxide sensor 16. ll changes are determined. That is, the peak value, which is the maximum value of the periodically fluctuating carbon dioxide concentration, is detected. Then, the patient 10 is controlled for a certain period of time (for example, every minute) based on a control formula stored in advance so that the deviation between the end-expiratory carbon dioxide concentration set in the ventilation volume setting device 82 and the actual carbon dioxide concentration is eliminated. The amount of ventilation per unit (corresponding to the amount of oxygen injected per certain period of light) is determined. Since this ventilation amount is expressed as the product of the number of breaths and the amount of one breath, the respiratory controller 14 needs to determine the number of breaths per certain period of time and the amount of one breath.
When the number of breaths is set to a constant value, the amount of breath per breath is determined. Then, when a control signal for obtaining the ventilation volume determined in this manner is supplied from the respiratory controller 14 to the respirator 12 via the drive circuit 84, the respirator 12 receives the anesthetic mixture from the anesthetic mixing device 62. The intake air is forcibly delivered to the patient 10 at the ventilation amount.

According to the above embodiment, the concentration of the inhaled anesthetic in the end expiration is detected at the time when the carbon dioxide concentration in the exhaled breath is at its highest peak, so it can be accurately detected regardless of the concentration of the inhaled anesthetic mixed into the inspired air. You can know the depth of anesthesia. In other words, in an automatic control system for keeping the depth of anesthesia constant, if the depth of anesthesia becomes too deep relative to the target value, the inhalation anesthetic that is mixed into the inhaled air to eliminate the deviation at this time is lowered by 1 degree. As shown in Figure 3 (C1), the concentration in the initial exhalation may be lower than the concentration in the final exhalation. Simply determining the end expiration from the peak will detect the initial concentration of the inhaled anesthetic in exhalation.

Since the concentration of the inhaled anesthetic in the end expiration determined as described above is used as information regarding the depth of anesthesia of the patient 10, the depth of anesthesia can be grasped more accurately than in the past. In other words, blood pressure values, pulse rate, brain waves, respiratory rate, electrocardiogram waves, etc. are physiological reactions that are influenced by factors other than the depth of anesthesia, and it is important to avoid variations in their appearance even with the same partial pressure of anesthetic in brain cells. do not have. On the other hand, end expiration is gas in the alveoli, and is there an inhaled anesthetic contained in it? This is because a6 corresponds to the anesthetic concentration in the arterial blood, and the anesthetic concentration in the blood corresponds to the anesthetic concentration (partial pressure) in the brain cells, which is closely related to the depth of anesthesia in the living body. For example, when general anesthesia is given to an elderly person who is thin and in poor general condition, circulatory depression is noticeable, especially when using halogenated anesthetics, and when the depth of anesthesia is monitored by blood pressure values etc., it may seem shallow even though it is actually shallow. It appears that the patient is under deep anesthesia, and when the surgery is performed at this time, the patient's body may move and his blood pressure may rise rapidly, making it appear that the anesthesia has suddenly become less intense. but,
This can be avoided if the depth of anesthesia is determined based on the concentration of inhaled anesthetic in the end expiration.

In addition, in the above-mentioned automatic depth of anesthesia control device, the inhalation anesthetic to be mixed into the inhaled air has a blood/gas partition coefficient of 1 or less at 37°C, so the concentration of the inhaled anesthetic to be mixed into the inhaled air changes. The stability of the control system is greatly improved because the depth of anesthesia changes quickly, and automatic control of the depth of anesthesia can be carried out suitably. In other words, it can be considered that the partial pressure of anesthetic within brain cells determines the depth of anesthesia, and the partial pressure of anesthetic within brain cells is determined by the concentration of inhaled anesthetic during inspiration, the effect of the second gas, and the alveoli. These factors include ventilation volume, alveolar/capillary permeability, cardiac output, blood properties, blood/brain barrier status, and physicochemical properties of anesthetics. When the blood properties are constant and there are no abnormalities in the blood/brain barrier, the factor that determines the depth of anesthesia is the anesthetic concentration in the inspired air.If the anesthetic concentration in the inspired air is changed, in the short term The lower the blood/gas partition coefficient, the easier it is to dissolve into the blood, and the partial pressure of the anesthetic in brain cells will react more sensitively.

Incidentally, halothane (If
Enflurane (blood/gas partition coefficient u2.4), enflurane (blood/gas partition coefficient 1.9), and isoflurane (blood/gas partition coefficient 1.48) are all good anesthetics, but The variation was not sufficient, and when they were used in an automatic depth of anesthesia control device, the stability of the control system was not sufficient for practical use, and the controlled depth of anesthesia also had large variations.

Although one embodiment of the present invention has been described above, the present invention is also applicable to other aspects.

For example, in the embodiment described above, the concentration of the inhaled anesthetic in the end exhalation is detected based on the infrared transmission signal SC supplied from the carbon dioxide sensor 16, but as shown in FIG. electrode 86 attached to the chest of
The minimum time of the thoracic impedance detected by the pre-fuji circuit 88 may be detected by the lower peak detection circuit 50, and the inhalation anesthetic concentration in the end expiration may be detected in synchronization with the minimum time. In this embodiment, the electrode 86 and the bridge circuit 88 correspond to a thoracic impedance ejection device, and the lower peak detection circuit 50 corresponds to a means for detecting the minimum thoracic impedance (3t)1. Further, as shown in FIG. 7, the gate circuit 52 is activated by a terminal signal SMT output from a switch 90 provided in the ventilator 12 and activated at the terminal stage of exhalation in conjunction with the movement of the piston or diaphragm. In this embodiment, the switch 90 corresponds to the terminal period detection means.

As shown in FIG. 8, instead of the signal SMT output from the switch 90 provided in the ventilator 12, one of the control signals or drive signals supplied from the respiratory controller 14 to the ventilator 12 may be used. A one-shot multi-bye break circuit 92 may be provided which opens the gate circuit 52 by outputting a pulse signal of a predetermined width triggered by the end of the exhalation period or the start of the inhalation period.

Furthermore, as shown in FIG. 9, the exhalation flow rate in the pipe 13 is detected by the flow meter 94, and when the lower peak detection circuit 50 detects that the exhalation flow rate has reached the minimum, a gate is gated in the same manner as described above. The circuit 52 may output an anesthetic concentration signal SSM indicating the concentration of the inhaled anesthetic in end expiration. In this embodiment, the flow meter 94 and the lower peak detection circuit 50 correspond to the terminal period detection means. In short, the lower peak detection circuit 5 in FIGS. 4, 6, and 9
0, the output signal of switch 90 in FIG.
The concentration of the inhaled anesthetic during end expiration may be detected based on a respiration synchronized wave indicating the end of exhalation of the patient 10, such as the output signal of the one-shot multivibrator circuit 92 shown in the figure.

Further, the gate circuit 52, lower peak detection circuit 50, etc. in the above-described embodiments may also be configured by a program of the EN microcomputer that configures the breathing controller 14 and the anesthesia depth controller 58. In this case, the infrared transmission signals SC and SM are provided directly to the anesthesia depth controller 58.

In addition, instead of the infrared gas analyzer with a heating tube included in the anesthetic concentration sensor 18 of the above-mentioned embodiment, the crystal adsorbs the halogenated anesthetic and its mass changes, and it responds to the change in mass. A crystal oscillation type gas concentration meter that utilizes the phenomenon in which the oscillation frequency changes may be provided.

In addition, although the infrared transmission signals SC and SM output from the carbon dioxide sensor 16 and the anesthetic concentration sensor 18 have a magnitude inversely proportional to the concentration, an inverting circuit may be provided as appropriate to make the magnitude proportional to the concentration. No problem.

It should be noted that the above-mentioned example is just one embodiment of the present invention, and various modifications may be made to the present invention without departing from the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a block diagram illustrating the configuration of an embodiment of the present invention. FIG. 2 is a diagram illustrating the configuration of the carbon dioxide sensor shown in FIG. 1. FIG. 3 is a timing chart explaining the operation of the embodiment shown in FIG. 1, in which (al) indicates the infrared transmission signal SC, (false) indicates the infrared transmission signal SM, and (C) indicates the anesthetic concentration in the inspired air. Infrared transmission signal S when low
FIG. 3D is a diagram showing the operation of the gate circuit. FIG. 4 is a diagram illustrating the configuration of the anesthetic concentration sensor shown in FIG. 1. FIG. 5 is a diagram illustrating the configuration of the anesthetic mixing device shown in FIG. 1. Figures 6, 7, 8 and 9
The figures are diagrams showing other embodiments of the present invention. 16: Carbon dioxide sensor (carbon dioxide concentration detection device) 18:
Anesthetic 1 degree sensor (anesthetic concentration detection device) 50: Lower peak detection circuit (maximum carbon dioxide concentration time detection means) 52: Gate circuit (anesthesia depth determination means) 90: Swift (end time detection means) 92: One Schott multi-vibrator circuit (terminus detection means) Applicant Nippon Kolin Co., Ltd. Figure 4 Figure 5 Tube 6 IP! “Figure 7

Claims (4)

[Claims] (1) An anesthesia depth detection device for detecting the depth of anesthesia of a living body anesthetized by mixing an inhalation anesthetic into the breath of the living body, which detects the concentration of the inhalation anesthetic contained in the breath of the living body. an anesthetic concentration detection device that continuously detects and outputs a signal that fluctuates in synchronization with respiration; an end time detection means that detects the end time of an exhalation period in respiration of the living body; and from the anesthetic concentration detection device. Anesthetic depth determining means for determining the concentration of the inhalation anesthetic at the terminal stage or a value based thereon among the output signals, and outputting this as a value indicating the depth of anesthesia. Depth detection device. (2) the end-of-life period detection means includes a carbon dioxide concentration detection device that continuously detects the concentration of carbon dioxide contained in the exhaled breath of the living body and outputs a signal indicating the concentration of carbon dioxide that changes in synchronization with respiration; 2. The depth of anesthesia detection device according to claim 1, further comprising maximum carbon dioxide concentration time detection means for detecting the maximum time of carbon dioxide concentration based on the signal output from the carbon dioxide concentration detection device. (3) The terminal period detection means detects a minimum period of thoracic impedance based on a thoracic impedance detection device that continuously detects changes in thoracic impedance of the living body and a signal output from the thoracic impedance detection device. The depth of anesthesia detection device according to claim 1, further comprising: thoracic impedance minimum time detection means. (4) The terminal period detection means directly or indirectly detects the terminal period of the exhalation period of the artificial respirator that forces the living body to breathe, and outputs a signal indicating the terminal period. The anesthesia depth detection device according to item 1.