JP4505656B2 - Small animal ventilator - Google Patents

Description

  The present invention relates to a ventilator for sending fresh breathing gas into the lungs of an animal and exchanging it with waste gas. More specifically, the present invention relates to a small animal that can be used safely for a long time against a small animal such as a mouse. It relates to a mechanical ventilator.

Conventionally, two types of ventilators for small animals have been used. One is a so-called capacity regulating system in which a rotational movement of a motor is converted into a reciprocating movement by a crank mechanism, and a fixed volume of gas is sent to the lungs of a small animal by reciprocating a piston (Non-patent Document 1). reference). The other is a so-called pressure regulation system that measures the airway pressure and controls the gas flow so that the pressure is maintained at a preset pressure (see Non-Patent Document 2). In either case, the respiration rate can be used in the range of 5 to 400 times / minute in accordance with the normal respiratory physiology of a small animal such as a mouse.
Shinano Manufacturing Catalog CWE Inc. catalog

  However, in the capacity-restricted ventilator, the inspiratory time to expiratory time ratio (I / E ratio) is usually fixed at 1: 1. There are also ventilators designed to change the I / E ratio, but the structure becomes complicated and not only costs increase, but it is difficult to change the I / E ratio almost continuously. Met. Moreover, since a predetermined volume of gas is forcibly sent to the lungs, there is a risk that excessive pressure is applied to the lungs. Furthermore, in a small animal respirator, the respirator may be operated at a respiration rate of 400 times / min. Unlike a human respirator normally used at a respiration rate of 10-20 times / min, There was a problem in durability due to the early wear.

  On the other hand, the pressure-regulated ventilator is superior in terms of safety because there is no danger of excessive pressure on the lung, but there is a problem that the tidal volume is unknown and the lung becomes hard ( When lung compliance became small), the tidal volume was reduced, resulting in insufficient ventilation.

  In addition, the conventional ventilator cannot be used as it is while performing inhalation anesthesia, and it is necessary to provide a bellow-in chamber mechanism to separate the anesthetic gas from the ventilator, and the apparatus is extremely complicated. There was a problem of becoming.

  The present invention has been obtained as a result of earnest study in view of the above-described problems. That is, the present invention provides a breathing circuit through which a gas having a set constant flow rate flows, an exhalation valve attached to the most downstream of the breathing circuit, a pressure sensor for measuring the pressure in the breathing circuit, and the breathing circuit A means for supplying a constant flow of gas as inspiration to the small animal when the exhalation valve is closed when the branch valve is further branched and connected to the trachea of the small animal, or the pressure in the breathing circuit reaches or is set When the inhalation time is completed, the exhalation valve is opened, and the expiratory air of the small animal is exhausted to the atmosphere together with a constant flow of gas. When the set exhalation time is expired, the exhalation valve is closed and the inhalation is again delivered to the small animal. Means, and means for calculating and displaying the tidal volume sent to the small animal by integrating the constant gas flow rate value converted into an electric signal and the inspiratory time, and pressure regulation depending on use conditions About small animal ventilator, characterized in that can be converted freely in either of formula and capacity regulation scheme.

  The present invention further includes an air pump and a mass flow controller in order to supply a constant flow rate of air in the above-described ventilator for small animals.

  The present invention further includes a vaporizer unit for an anesthetic agent in order to perform artificial respiration while performing anesthesia in the above-described ventilator for small animals.

  The ventilator for small animals of the present invention is highly safe as a ventilator for small animals such as mice with a large number of breaths and a small tidal volume, and has a high breathing rate, an inspiratory time to expiratory time ratio, and a maximum inspiratory pressure. Can be used as either a volume regulation system or a pressure regulation system simply by adjusting the respiratory gas flow rate, making it possible to freely convert to either while taking advantage of both systems . By adding an air pump and a mass flow controller, artificial respiration can be performed independently. Furthermore, by adding a vaporizer unit, artificial respiration can be performed as it is while performing inhalation anesthesia. As described above, the ventilator for small animals of the present invention exhibits extremely significant effects and is highly practical.

  Hereinafter, embodiments of a ventilator for small animals according to the present invention will be specifically described with reference to the drawings.

  FIG. 1 is a piping system diagram for explaining an embodiment of the ventilator for small animals of the present invention, and FIG. 2 is a piping system diagram when an air pump, a mass flow controller and a vaporizer unit are incorporated. FIG. 3 shows the configuration of the vaporizer unit, and FIG. 4 shows the pressure in the expiration circuit and the operation timing of each solenoid valve.

  In FIG. 1, 1 is a supply gas connection port, 2 is a breathing circuit, 3 is an electromagnetic valve functioning as an exhalation valve, 4 is a pressure sensor, and 5 is for performing zero calibration of the pressure sensor. An electromagnetic valve, 6 is an electromagnetic valve for releasing excessive pressure, and 7 is a tracheal connection tube connected to a small animal, which is connected to the trachea of the small animal via a tracheal tube or a tracheostomy tube (not shown). The

  Next, a method for operating the ventilator for small animals according to the present invention will be described. When a gas supply source capable of flowing a constant flow of breathing gas is connected to the supply gas connection port 1, the breathing gas flows to the exhalation valve 3 via the breathing circuit 2. The exhalation-valve 3 is preferably a three-way solenoid valve that is open when not in operation, and has a fast operation time and excellent durability.

  When the exhalation valve 3 is activated and closed, the breathing gas flows toward the trachea of the small animal, and the pressure in the breathing circuit increases.

  The breathing circuit 2 branches before the exhalation valve 3 and is connected to the pressure sensor 4 through the zero calibration electromagnetic valve 5, and the pressure in the breathing circuit is constantly measured by the pressure sensor 4. The zero-calibration solenoid valve 5 is open when it is not in operation, and the breathing circuit 2 and the pressure sensor 4 are in communication. However, when it is in the actuating state, the breathing circuit 2 is closed and the pressure sensor 4 is in the atmosphere. And zero calibration will be performed. Normally, zero calibration is automatically performed when the power is turned on and thereafter once every four hours.

  The breathing circuit 2 branches near the supply gas connection port and is connected to the overpressure relief valve 6. The overpressure relief valve 6 is a two-way electromagnetic valve that is in a closed state when not in operation, and is opened when the pressure in the breathing circuit becomes excessive, and serves as a safety valve that releases pressure.

  In the present ventilator, the number of breaths and the I / E ratio are set, and the inspiratory time and expiratory time are calculated from both. In this ventilator, the maximum inspiratory pressure is set. During inspiration, the exhalation valve 3 is closed, and respiratory gas is sent to the trachea of a small animal via the respiratory circuit 2 and the trachea connection tube 7. At the same time, when the pressure in the breathing circuit reaches the set maximum inspiratory pressure or when the set inspiratory time ends, the exhalation valve 3 opens, and the exhaled gas is discharged into the atmosphere together with the gas flowing through the breathing circuit 2. .

Setting the maximum intake air pressure, for example setpoint + 2 cmH ₂ limit alarm value O, low alarm value is set to the setting value one 2 cmH ₂ O. When the pressure in the breathing circuit exceeds the upper limit alarm value, the high pressure alarm is activated and the overpressure relief valve 6 is opened. When the breathing circuit internal pressure falls below the lower limit alarm value, the low pressure alarm is activated. The upper / lower limit alarm set value should be set to ± ₂ cmH ₂ O or more according to the situation.

  By integrating the flow rate value converted into an electrical signal obtained from a gas supply source supplied at a constant flow rate and the inspiratory time, the tidal volume delivered to the small animal is calculated and displayed. If the inspiration ends when the pressure in the breathing circuit reaches the set maximum inspiratory pressure, the actual inspiratory time is reduced regardless of the inspiratory time calculated from the number of breaths and the I / E ratio setting. Used for calculation.

本発明による小動物用人工呼吸器は、最大吸気圧力を設定し、呼吸回路内圧が設定された最大吸気圧力に達すると吸気が終了して呼気に切換わるので、基本的には圧力規定方式をとっているが、定常流量値に吸気時間を積算することにより、１回換気量が計算され表示されており、設定された吸気時間中に呼吸回路内圧が最大吸気圧力に達しない場合は、１回換気量が一定に保たれることになり、容量規定方式となる。Ventilators can be broadly classified into volume regulation systems that regulate the intake volume and pressure regulation systems that regulate the pressure applied to the airway, and each has advantages and disadvantages as shown in the table below.

The ventilator for small animals according to the present invention sets the maximum inspiratory pressure, and when the inspiratory circuit pressure reaches the set maximum inspiratory pressure, the inspiration ends and switches to exhalation. However, by adding the inspiratory time to the steady flow rate value, the tidal volume is calculated and displayed, and if the respiratory circuit pressure does not reach the maximum inspiratory pressure during the set inspiratory time, The ventilation volume will be kept constant, which is the capacity regulation method.

  In the normal pressure regulation method, generally, when the pressure in the breathing circuit reaches the set maximum inspiratory pressure, the pressure is maintained as it is, and when the set inspiratory time ends, the breath is switched to exhalation. . For this purpose, it is necessary to use an electropneumatic valve capable of continuously adjusting the opening rather than an electromagnetic valve that simply opens and closes as an exhalation valve, and the electropneumatic valve is very expensive. In order to maintain the pressure, an automatic feedback control means is necessary. However, the ventilator according to the present invention is limited to small animals and is normally used in the range of 60 to 200 breaths / minute, so the inspiratory time is 0.5 seconds or less, Does not make sense to maintain the maximum intake pressure. In view of this situation, as soon as the breathing circuit internal pressure reaches the set maximum inspiratory pressure, the inspiration is terminated and switched to exhalation, so that an inexpensive solenoid valve can be used and a steady flow rate value can be obtained. It was possible to obtain the merit that the tidal volume can be calculated by integrating the intake time. In the conventional pressure regulation system, a part of the breathing gas is leaked from the exhalation valve in order to maintain the breathing circuit internal pressure at the maximum inspiratory pressure, so that an accurate tidal volume is shown even if the inspiratory time is multiplied by the steady flow rate value. I can't.

In actual use, settings are made in the following procedure.
(1) The tip of the tracheal connection tube 7 is closed.
(2) Set the number of breaths and the I / E ratio.
(3) Set the maximum intake pressure.
(4) If the high pressure alarm is activated, reduce the steady flow rate. When the low pressure alarm is activated, the steady flow rate is increased.
(5) Confirm that the breathing circuit internal pressure is within the maximum inspiratory pressure ± ₂ cmH ₂ O and confirm that the value of the tidal volume display is appropriate.
(6) The trachea connecting tube 7 is connected to a small animal via a tracheal tube or the like.
(7) If the high pressure alarm is activated, reduce the steady flow rate. When the low pressure alarm is activated, the steady flow rate is increased.
(8) Confirm that the breathing circuit internal pressure is within the maximum inspiratory pressure ± ₂ cmH ₂ O and that the value of the tidal volume display is appropriate.
(9) To change to the capacity regulation system when operating in the pressure regulation system, reduce the steady flow rate or increase the maximum intake pressure setting.
(10) To change to the pressure regulation system when operating in the capacity regulation system, increase the steady flow rate or lower the maximum intake pressure setting.

  If the breathing circuit internal pressure does not reach the set maximum inspiratory pressure, a constant tidal volume is delivered unless the lung compliance changes, so this is a capacity regulating method. In addition, when the breathing circuit internal pressure reaches the set maximum inspiratory pressure and switches from inspiration to expiration, the pressure regulation method is used, but even in this case, the calculated value of the tidal volume is displayed. Even when operating in the volume regulation method, when the state of the lungs of the small animal changes and the compliance becomes smaller, the pressure in the respiratory circuit reaches the set maximum inspiratory pressure and is converted to the pressure regulation method. At this time, the maximum intake pressure can be set higher or the steady flow rate can be reduced to return to the capacity regulating method.

  FIG. 2 is a piping system diagram when the gas supply means and the vaporizer unit are attached to FIG. 1. Portions common to FIG. 1 are given the same numbers. 8 is an air pump, 9 is a mass flow controller, and 10 is a vaporizer unit.

  The air pump 8 is for supplying clean air to a small animal, has a quiet operation sound, and is preferably an oilless diaphragm pump. The mass flow controller 9 adjusts the steady air flow rate to be supplied to the small animal, and the tidal volume is calculated by adding the inspiratory time to the flow rate value output therefrom.

  The vaporizer unit 10 is located downstream of the mass flow controller 9, vaporizes a volatile anesthetic such as sevoflurane, turns it into a gas, and sends it to a small animal together with a breathing gas, thereby performing artificial respiration while performing anesthesia. It can be performed. Anesthesia gas also flows in the expiratory phase and is thrown away into the atmosphere. However, in the case of a small animal respirator, the minute ventilation is extremely small, which is not a problem.

  FIG. 3 shows an example of a vaporizer unit, 10a is an anesthetic bottle, 10b is an anesthetic injection pump, 10c is a vaporization chamber, 10d is an anesthetic gas concentration monitor, and 10e is It is a vaporizer unit inlet and 10f is a vaporizer unit outlet.

  When the concentration of the volatile anesthetic such as sevoflurane is set, the amount of the volatile anesthetic to be injected with respect to the gas flow rate controlled by the mass flow controller 9 can be calculated, so the anesthetic injection pump 10b sucks the calculated amount from the anesthetic bottle 10a and injects it into the vaporizing chamber 10c. Since vaporization is performed in the vaporization chamber 10c, it is necessary to be made of a metal material with good heat conductivity and to be heated with a heater in order to prevent the vaporization heat from lowering the temperature and lowering the vaporization efficiency. . Although it can be confirmed whether the anesthetic concentration is correctly maintained by the anesthetic gas concentration monitor 10d, it is not always necessary.

  FIG. 4 shows the relationship between the open / close state of the solenoid valve and the internal pressure of the breathing circuit. The horizontal axis represents time, Ti represents inspiration time, Te represents expiration time, Ti + Te represents one breathing time, and the number of breaths is RR (times / minute), which is represented by 60 / RR. The vertical axis represents the breathing circuit internal pressure, and the maximum inspiratory pressure line represents the set maximum inspiratory pressure.

  In FIG. 4, the leftmost pressure waveform is the case where the pressure in the breathing circuit does not reach the maximum inspiratory pressure set during the inspiratory time, and the ventilator is operating in a capacity defining manner. The next pressure waveform is when the pressure in the breathing circuit reaches the maximum inspiratory pressure set during the inspiratory time and the exhalation valve opens, and the ventilator is operating in a pressure regulating manner. The next pressure waveform shows a case where the pressure in the breathing circuit becomes equal to or higher than the maximum inspiratory pressure set during the inspiratory time, reaches the set maximum inspiratory pressure +2 cmH2O which is the upper limit alarm value, and the safety valve is opened. At this time, the high pressure alarm is activated. The rightmost pressure waveform is a case where the pressure in the breathing circuit does not reach the set maximum inspiratory pressure −2 cmH 2 O which is the lower limit alarm value during the inhalation time, and at this time, the low pressure alarm is activated.

  The ventilator for small animals of the present invention can safely ventilate a small animal such as a mouse over a long period of time, and further, as a ventilator for conducting various experiments while performing inhalation anesthesia. It can be used suitably.

  It is a piping system diagram for demonstrating embodiment of the ventilator for small animals of this invention.   It is a piping system diagram at the time of incorporating an air pump, a mass flow controller, and a vaporizer unit.   The structure of a vaporizer unit is shown.   The pressure in the expiration circuit and the operation timing of each solenoid valve are shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Supply gas connection port 2 Breathing circuit 3 Expiratory valve 4 Pressure sensor 5 Solenoid valve for zero calibration 6 Overpressure relief valve 7 Tracheal connection tube 8 Air pump 9 Mass flow controller 10 Evaporation unit 10a Anesthetic drug bottle 10b Anesthetic drug injection pump 10c Vaporization chamber 10d Anesthetic gas concentration monitor 10e Vaporizer unit inlet 10f Vaporizer unit outlet

Claims (3)

A breathing circuit through which a gas having a predetermined flow rate flows, an exhalation valve attached at the most downstream of the breathing circuit, a pressure sensor for measuring the pressure in the breathing circuit, and a branch of the small animal from the breathing circuit Means for delivering a constant flow of gas as inspiration to a small animal when connected to the trachea and the exhalation valve is closed, the pressure in the breathing circuit reaches a set pressure or the set inspiratory time ends Then, the exhalation valve is opened, the exhalation of the small animal is exhausted to the atmosphere together with a constant flow of gas, the exhalation valve is closed when the set exhalation time is over, and the inhalation is again delivered to the small animal, and the electric signal Means for calculating and displaying the tidal volume sent to the small animal by multiplying the converted constant gas flow rate value and the inspiratory time, and a pressure regulation system and a capacity regulation system depending on the use conditions Small animal ventilator, characterized in that can be converted freely in either. The artificial respirator for small animals according to claim 1, further comprising an air pump and a mass flow controller for supplying a constant flow rate of air. The artificial respirator for small animals according to claim 1, further comprising a vaporizer unit for anesthetic to perform artificial respiration while performing anesthesia.

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