JP2001009035A - Respiration assistance method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the decrease of the respiration work done in spontaneous respiration and over pressure and to decrease the expiration work. SOLUTION: An air feed pipe is connected to one connecting port of a three- way connecting pipe 13 and a patient's mouth 3 is connected to the second connecting port of the three-way connecting pipe 13. Further, a variable resistor 12 which is controllable from outside is mounted ate the third connecting port. A means for passing the air feed gas of a stationary flow to a patient circuit opening the outlet of the variable resistor 12 to the atmosphere and measuring the internal pressure of the respiratory tract of the patient's mouth making respiration is provided. The waveforms of the internal pressure of the respiratory tract of the patient's mouth is controlled by changing the variable resistor so as to meet the purpose of treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a respiratory assist method for a respiratory disease patient who needs artificial respiration.

[0002]

2. Description of the Related Art In recent years, a pressure assisted breathing assist method called pressure support has become popular. In this method, the airway pressure to be assisted is determined in advance, and when it is detected that the patient has started inhaling, the air supply valve is opened and the insufflation gas is sent out immediately, while the pressure at the mouth of the patient is detected and the pressure to be assisted is detected. Control the flow rate to keep At this time, when to stop the air supply to the patient, 1. The flow rate inhaled by the patient has dropped below a certain level. 2. When the airway pressure cannot maintain the target assist pressure even if the flow rate is controlled and exceeds the value beyond a certain value; Generally, when any one of the conditions is satisfied when the intake time reaches a predetermined time.
This method has the effect of reducing the inspiratory work of the patient and suppressing excessive rise in the airway pressure, and has become widely used in the treatment of patients with severe respiratory disease. There are many in the market.

[0003]

However, the mechanism for performing such control attempts to provide feedback to keep the airway pressure at the patient's mouth constant by increasing or decreasing the flow rate of the insufflation gas delivered from the body of the ventilator. As described below, the realization is difficult and the device becomes complicated. That is, in a real device, the connection between the mouth of the patient and the body of the ventilator must be connected by a flexible coil, which usually has a length of about 2 m, which is a large delay element in the pressure control loop and is accurate. It is difficult to obtain a responsive control characteristic. Further, such control is performed only in the inspiratory phase, and is ineffective in the expiratory phase. However, in the expiratory phase, the resistance of the coiled tube and the exhalation valve on the exhalation side exists, and exhalation work is generated. When a patient performs spontaneous breathing while connected to the patient circuit, the resistance of the patient circuit, which is a closed circuit, will give the patient additional work of breathing in any of inspiration and expiration, and will add a compliant bag to the patient circuit. Method has compensated for the shortcomings, but when performing positive end-expiratory pressure (CPAP),
The resistance of the element for applying the CPAP pressure cannot be ignored, and there are problems such as the occurrence of exhalation work. The present invention relates to providing a pressure assisted breathing method which solves such a problem.

[0004]

In other words, instead of precisely controlling the flow rate of the insufflation gas in the inspiratory gas delivery system and performing pressure assist at the patient's mouth, the on-off control used in the conventional ventilator is used. Uses a variable resistance element in the controllable flow path instead of the exhalation valve to control the airway pressure at the mouth of the breathing patient in response to the treatment purpose with high-speed response. Is what makes it possible. The inventor of the present invention has previously filed a patent application for a respiratory assist method using a variable pressure limiter element (Heisei 4).
The present invention aims to improve the pressure-respiratory assistance of a patient in the same manner as the prior-art respiratory assist method. More specifically, the airway pressure at the mouth of the patient should be reduced to zero the amount of respiratory work required for the ventilator during inspiration and expiration of the patient, or in some The control is based on the pressure at which the flow of inspired gas occurs, so as to reduce the increased work of breathing due to lesions in the tube and the patient's respiratory tract. In the respiratory assist method of the prior application, the purpose is realized by using a passive circuit element as a pressure limiter having a non-linear concept as an exhalation valve in the conventional concept of a patient circuit, The present invention is different from the concept that the objective is achieved by performing negative feedback control using a variable resistance circuit element that performs a linear operation. Therefore, according to the method of the present invention, while the prior application was to maintain the airway pressure at the mouth constant regardless of the patient's respiration, precise and high-speed control is possible with an arbitrary pressure waveform according to the purpose of treatment. become. For example, if only the pressure drop with respect to the instantaneous flow rate of the endotracheal tube is given higher than zero pressure at the patient's mouth, it is possible to compensate only for the resistance loss of the endotracheal tube.
In addition, a proportional support type artificial respiration system (Japanese Unexamined Patent Application Publication No. 5-115554)
On October 18, 1991, the patient's respiratory system compliance with the instantaneous flow rate and the pressure loss due to the resistance were compensated by the airway pressure at the mouth of the patient, and this method of breathing was realized by applying the method of the present invention. It is also possible to do.

[0005]

FIG. 1 shows an example of the configuration of a ventilator 1 for implementing a conventional pressure support method. When the pressure sensor 5 that measures the airway pressure in the mouth 3 via the introduction tube 4 detects that the patient 2 has started inhaling, the control unit 6 opens the main valve 7 and sends out the gas from the supply pressure source 8. At this time, the exhalation valve 9 is closed at the same time. In order to maintain the airway pressure at the mouth 3 of the patient 2 at a predetermined positive auxiliary pressure in the inspiratory phase, the control unit 6 continuously compares the pressure value obtained from the pressure sensor 5 with the set auxiliary pressure and increases the pressure value. For example, the main valve 7 is controlled to reduce the flow rate, and if it is low, the reverse control is performed. The main valve 7 and the mouth 3 are connected by a flexible flexible tube 10.
For this reason, a large time delay occurs in this control loop system, and it is difficult to realize a control system with good stability and responsiveness.
For this reason, it is difficult to obtain a flat assist pressure in the inspiratory phase for patients with various respiratory impedances, and even if a stable trapezoidal pressure waveform can be obtained in the standard state, If the resistance increases, an overshoot occurs at the rise or a vibration waveform occurs. Also, if the airway resistance is low and the compliance increases, the intake phase ends without reaching the target auxiliary pressure at all. A compromise in properties is required. Next, an embodiment of the present invention is shown in FIG. The difference from FIG. 1 is that a variable resistor 12 is used near one connection port of a three-way connection pipe 13 at the mouth of the patient 2 instead of the exhalation valve 9 in FIG. The operation will be described below. The main valve 7 is always open such that a constant flow of gas, which does not fall below the maximum instantaneous flow that the patient 2 may need, is poorly generated. When the patient 2 is not breathing, the variable resistor 12 controls the control unit 6 to apply the atmospheric pressure or the positive pressure end-expiratory pressure (PEEP) to the patient's mouth 3 when applying the pressure. Has decreased. When the patient 2 starts inhaling, the airway pressure at the patient's mouth 3 starts to decrease. The control unit 6 responds to the control signal, and the variable resistor 12 immediately increases the resistance and operates so that the pressure at the patient mouth 3 remains at a predetermined auxiliary pressure. In general, the inspiratory flow rate of the patient 2 greatly decreases at the beginning of inspiration, so that the variable resistor 12 changes the resistance value in accordance with the change to maintain the auxiliary pressure. So you will return to the state. In the pressure control loop according to the present invention, the variable resistor 1
Since 2 is disposed in close proximity to the patient's mouth 3 which is a pressure control point, the time delay is small and the loop setting can be set high, so that the system is dramatically improved as compared with the conventional system. The foregoing has described the superiority of the system according to the present invention over the conventional system for the intake phase. Next, the operation in the expiration phase will be described. When the patient 2 finishes inhaling, naturally the patient 2 starts to exhaust the gas that has been inhaled. When the expiration phase starts, a gas flow of the above-mentioned fixed flow rate plus the expiration gas discharged from the patient flows below the mouth 3 of the patient and is discharged to the atmosphere via the variable resistor 12. In the conventional system shown in FIG. 1, the exhaled gas of the patient is discharged via the intrinsic residual resistance when the exhalation valve 9 is opened. However, this resistance cannot be ignored. Stretching increases the mean airway pressure, adversely affecting the circulatory system, and induces expiratory effort to exert expiratory work. In the case of the present invention, the variable resistor 12 instead of the exhalation valve 9 operates also in the expiration phase, and maintains the airway pressure to be maintained in the expiration phase. That is, the resistance value is further reduced to prevent an increase in pressure in the expiration phase. However, in a state where there is some flow rate, it is actually impossible to make the resistance zero, and when the airway pressure is kept at zero, some pressure rise is inevitable. As described above, according to the present invention, it is possible to measure the airway pressure at the mouth 3 of a patient and control the variable resistance 12 over the entire time of inspiration and expiration, thereby giving a therapeutically desirable pressure pattern to each of the inspired and expired air. The pressure pattern includes a case where two pressure values in the conventional intermittent positive pressure breathing are alternately taken, and a case where a pattern for compensating for the pressure loss of the endotracheal tube is given. In the case of conventional pressure-supported breathing, measurement of the patient's inspiratory flow is indispensable in order to perform flow termination as a leading indicator of the end of inspiration, but this invention is desirable from the viewpoint of monitoring. Monitoring of patient flow with disadvantages is unnecessary from the viewpoint of the additional cost and cost. Next, a specific implementation example of the variable resistor 12 will be described. FIG. 3 shows a specific example of the variable resistor 12. This example has the same structure as a conventional diaphragm type exhalation valve, and changes the gap 107 between the diaphragm 101 and the valve seat 102 at the distal end surface of the cylinder, which is a gas outlet, from zero to several mm to form a gap 107. This is realized by giving a variable resistance to the gas flow 108 passing through. The distance between the gap 107 and the servo motor 10
The rotation of No. 3 is transmitted to the ball screw 104 whose axial direction is constrained, and the driving bar 106 attached to the nut 105 whose rotation is attached to the ball screw 104 performs a linear reciprocating motion. Diaphragm 1 at the end of drive bar 106
01 is attached. Diaphragm 101 and valve seat 1
When the end surface of the variable resistor 02 comes into contact, the resistance of the variable resistor 12 becomes infinite or in a closed state, which is the same as the state in which the exhalation valve 9 in the conventional system is closed. Diaphragm 101 and valve seat 1
FIG. 4 shows an example of a pressure drop, that is, a change in resistance with respect to the gap 107 of FIG. As is clear from this figure, in this method, the resistance change is large when the gap 107 is zero to 2 mm. This means that the gain is large as an element of the control loop, and better and more accurate control can be performed by appropriate tuning. FIG. 5 shows an embodiment of the present invention.
Changes in airway pressure and patient flow when spontaneous breathing was given by a simulator were added to the control system at PEEP values of 10 and 20 cm.
An example in which a target is provided and operated so as to maintain H ₂ O is shown. As is clear from this example, the airway pressure hardly fluctuates from the PEEP set pressure irrespective of the change in the flow rate due to inspiratory expiration. As described above, the control characteristic is improved by controlling the high-speed response variable resistor 12 with the patient's mouth 3,
In addition, pressure fluctuation due to resistance loss due to connection is eliminated, so that ideal pressure breathing assistance is possible. As a method of realizing the variable resistance, other than the above-described diaphragm driving method, any structure that can change the flow path resistance at high speed and does not give an excessive dead space to the circuit can be applied. Breathing assist methods using variable resistance are also within the scope of the present invention.

[0006]

As described above, by using the present invention, it is possible to perform respiratory assist by pressure assist by precise control of the airway pressure at the mouth of a patient, and in particular, to shorten the weaning or weaning of the patient from a so-called ventilator. And prevention of reintubation can be expected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a ventilator that performs a conventional respiratory assist method.

FIG. 2 is a configuration diagram of a respirator that performs a respiratory assist method according to the present invention.

FIG. 3 shows a specific example of a diaphragm system for realizing a variable resistor required in the present invention.

FIG. 4 is a graph showing the relationship between the resistance and the gap between the diaphragm and the valve seat in a specific variable resistor.

FIG. 5 is a graph showing changes in airway pressure and flow rate when breathing assistance according to the present invention is performed at a constant pressure.

[Explanation of symbols]

1 is a ventilator, 2 is a patient, 3 is a patient mouth, 4 is a pressure introducing tube, 5 is a pressure transducer, 6 is a control unit,
7 is an air supply valve, 8 is a pressure source 9 is an exhalation valve, 10 is a flexible tube, 11
Is a flow sensor, 12 is a variable resistor, and 13 is a three-way connection pipe.

Claims (1)

[Claims] An air supply pipe is connected to one connection port of a three-way connection pipe, a patient mouth is connected to a second connection port of the three-way connection pipe, and a variable resistance which can be controlled from the outside is further connected to a third connection port. A ventilator equipped with a means for measuring the airway pressure at the mouth of a patient breathing a steady flow of insufflation gas in a patient circuit that opens the outlet of the variable resistance to the atmosphere,
A respiratory assist method for controlling the waveform of the airway pressure at the mouth of a patient by changing the variable resistance so as to match the purpose of treatment.