JPH0441869Y2 - - Google Patents

Description

[Detailed description of the invention] "Industrial Application Field" This invention relates to an artificial lung device used to assist the lung function of patients with respiratory failure.

``Prior Art'' A blood pump for an artificial liver has been developed as an efficient device that causes less damage to the blood in order to extracorporeally circulate the blood of patients with respiratory failure and remove carbon dioxide components from the blood during the extracorporeal circulation. An extracorporeal circulation type lung support device using a dialyzer has been proposed. FIG. 10 is a block system diagram thereof. In the figure, the patient's blood is sent to the dialyzer 2 through the blood line;
Bicarbonate ions (HCO ₃
⁾ and dissolved carbon dioxide (CO ₂ ) move to the perfusate side, and the blood with reduced carbon dioxide components is returned to the patient's body via the drip chamber 3, blood diversion meter 6, and venous pressure regulator 4 in sequence. It can be done.

The perfusate supplied from the perfusate supply unit 10 to the diffusion tube 11 flows into the dialyzer 2 from the outlet of the diffusion tube 11 via the PH electrode 12, thermometer 13, pump, and flowmeter 15 in order. The irrigation fluid that flows out is returned to the diffusion tube 11 through the hydraulic pressure gauge 16, the fluid shortage detector 17, and the heater 18 in this order. In this way, a circulation path for the irrigation fluid is constructed.

The inert gas supplied from the gas supply section 20 is supplied to the dispersion tube 11 via a pressure regulator 21, a stop valve 22, a gas flow valve 23, a gas flow meter 24, and a check valve 25 in this order.

In the diffusion tube 11, hydrogen ions (H ⁺ ) in the perfusate combine with bicarbonate ions (HCO ₃ ^- ) to generate bicarbonate ions (H ₂ CO ₃ ), and this bicarbonate is added to the perfusate. It is converted to carbon dioxide by the catalytic action of carbonic anhydrase CA (carbonic anhydrase) contained in it. That is, HCO ₃ ^- +H ⁺ H ₂ CO ₃ C. A. It becomes H ₂ O + CO ₂ (1). The perfusate is brought into gas-liquid contact with an inert gas in the dispersion tube 11, and this newly converted carbon dioxide and the carbon dioxide already taken into the perfusate in the dialyzer are diffused as carbon dioxide gas.

A PH adjusting liquid is supplied from the PH adjusting liquid supply section 30 to the diffusion cylinder 11 via the pinch valve 31, and hydrogen ions (H ⁺ ) are replenished. The concentrations of bicarbonate ion and carbon dioxide in the perfusate are [HCO ₃ ^- ] and
Expressed in [CO ₂ ], the pH of the perfusate is the so-called Henderson-Hasselbach
is given by the equation. That is, PH=pK _A +log [HCO ₃ ^- ]/[CO ₂ ] (2) Here, pK _A is a constant and is 6.1. If the bicarbonate ion (HCO ₃ ^- ) increases, the pH will increase, and if a pH adjustment solution is given to promote the reaction of equation (1), the bicarbonate ion (HCO ₃ ^- ) will decrease and the carbon dioxide ( _CO2 )
increases, so PH decreases.

By the way, carbonic anhydrase, which is added to the perfusate to convert bicarbonate ions into carbon dioxide, has a pH range called an active region in which it can exert its catalytic action, and the pH is usually 7.3 to 7.6. In a healthy person, the pH of the blood is approximately equal to 7.4. The pH of the perfusate is preferably controlled within the range of 7.2 to 7.6, taking into consideration the active region of carbonic anhydrase and the pH of blood. For this reason, the control unit 40 monitors the data of the PH electrode 12 and controls the pinch valve 31 on and off so that the PH of the perfusate does not deviate from this range.
A conditioning liquid (for example, dilute hydrochloric acid solution) is supplied to the diffusion cylinder 11 .

In the dialyzer 2, at the same time that the carbon dioxide component is transferred from the blood to the perfusate, water is also transferred. That is, when the pressure difference between the blood and the perfusate, the so-called dialyzer overpressure, is positive, water is removed from the blood,
Conversely, when it is negative, water enters the blood. Furthermore, if the overpressure is zero, there is no movement of moisture. Therefore, it is necessary to control overpressure as necessary. Therefore, the control unit 40 calculates the difference between the data of the hydraulic pressure gauge 16 and the data of the venous pressure gauge 5, that is, the overpressure, and controls the venous pressure regulator 4 as necessary.

The control unit 40 is provided in the radiation path of the radiation cylinder 11.
Based on the data x of the CO ₂ concentration meter 19 and the data y of the flow meter 15 of the perfusate inflow passage, the carbon dioxide removal flow rate z
= xy, and if the blood flow rate (data from the blood flow meter 6) is within the allowable range and can be varied, the blood pump 1 is adjusted so that this value is equal to the set value.
If it is not possible to change the gas flow rate valve 2.
3 to adjust the flow rate of the inert gas, and also control the pump 14 of the irrigation fluid inflow passage to adjust the flow rate of the circulating irrigation fluid. Control to adjust the carbon dioxide removal flow rate z to the set value is performed immediately after the lung assist device is activated.

The control unit 40 also displays various data on the display 41, such as the temperature, fluid pressure, PH, flow rate, liquid shortage, blood flow rate, venous pressure, inert gas flow rate, and carbon dioxide concentration of the perfusate.

Setting values such as the carbon dioxide removal flow rate, PH and temperature of the perfusate are stored in the storage circuit of the control unit 40 from the operation unit 42.

``Problem that the invention aims to solve'' If the pH of the perfusate is kept constant, the amount of bicarbonate ions (HCO ₃ ^- ) that moves from the blood side to the perfusate side through the membrane of the dialyzer is the initial value. decreases exponentially. Therefore, the replenishment of hydrogen ions (H ⁺ ) must be carried out minutely in accordance with the amount of bicarbonate ions (HCO ₃ ^- ) transferred. However, the conventional supply control of the PH adjustment liquid is an on/off control using a pinch valve, and is not a control that continuously varies the supply flow rate. As shown in Fig. 11, the PH is compared with the control center value according to a certain timing (A in the figure), and if it exceeds this value, the pinch valve is turned on (opened), and if it is below the reference value, it is turned off ( closed). The closer to the start of treatment, the larger the injection amount of the PH adjustment solution is. In order to satisfy this initial supply capacity, the time required to keep the pinch valve on will naturally be longer, but this alone is not sufficient and the inner diameter of the PH adjustment liquid injection line must be increased to some extent. The proportion of time that the pinch valve is kept on is large immediately after the start of treatment and decreases over time. (Figure 11B).

Flush the pinch valve once and inject.
The minimum unit of PH adjustment liquid is determined by the inner diameter of the PH adjustment liquid injection line and flushing time. This flushing time depends on the pinch valve, but it is mechanically difficult to reduce it too much. Furthermore, as described above, the inner diameter of the injection line cannot be made very small, so the minimum unit of pH adjustment liquid produced by one flushing process becomes large to some extent. The PH of the perfusate can be controlled by on/off control of such a pinch valve.
As shown in FIG. 11C, the curve has a characteristic that undulates above and below the control center value. As the amount of bicarbonate ion (HCO ₃ ^- ) migrating becomes smaller and slower over time, a single flush of the pinch valve will inject too much buffer, causing pH adjustment. PH of the perfusate after the fluid is injected
becomes too small, and the trough of the wave-like change gradually becomes larger. Therefore, carbonic anhydrase contained in the perfusate
The lower limit of CA's PH active range is exceeded, and not only is the conversion from hydrogen bicarbonate to carbon dioxide according to equation (1) not performed efficiently, but blood is
It is also undesirable as it causes the pH to fluctuate.

Furthermore, if a large amount of PH adjustment liquid is injected in one flushing due to a failure of the pinch valve, the PH of the blood may fluctuate, which may have a negative impact on the patient.

The purpose of this invention is to eliminate the above-mentioned drawbacks, suppress fluctuations in the PH of the perfusate, and improve the safety of the device by preventing blood PH from fluctuating even if the PH deviates significantly from the set range. This is what I am trying to do.

``Means for solving the problem'' In this invention, instead of the pinch valve that turns on and off the injection of the PH adjustment fluid in the conventional lung assist device, an injection flow rate adjustment section is provided to adjust the PH of the perfusate. In addition to improving the ability to continuously and finely adjust the injection flow rate of the PH adjustment solution to a predetermined range, this injection system also stops the injection of the PH adjustment solution in the event that the PH of the perfusate reaches the alarm range. Provide a stop. At the same time as this infusion is stopped, a bypass is made between the inflow passage of the perfusate to the dialyzer and the outflow passage from the dialyzer between the diffusion tube and the dialyzer, and the perfusate is circulated without passing through the dialyzer. and means for blocking the perfusate inflow and outflow passages of the dialyzer at the same time as the bypass means is turned on. Control of the injection flow rate adjustment section, injection stop section, bypass means, and closure means described above is performed by the control section.

Embodiment FIG. 1 is a block system diagram showing the main parts of an embodiment of the extracorporeal circulation type lung assist device of this invention, and the parts not shown are the same as the conventional example shown in FIG.
An injection flow rate adjustment section 50 and an injection stop section 51 are inserted into the injection passage for the PH adjustment liquid.

On-off valves 53 and 54 are inserted into the inflow and outflow passages connected to the inflow and outflow ports of the dialyzer 2, respectively, and the on-off valves 53 and 54 are inserted between the inflow and outflow passages on the side other than the dialyzer side. A bypass 55 having 54 is provided.

Control of these improved or added devices is performed in the control section 40 in parallel with control of other devices.

A microcomputer is used for the control unit 40, and its central processing unit (CPU) 60 performs control by sequentially decoding and executing programs stored in a read-only memory (ROM) 61. A control program for the entire lung assist device is stored in the ROM 61, and a perfusate PH control program is also included therein. The control center value of PH (for example, 7.4), the control width (for example, ±0.2), and the alarm setting width (for example, ±0.3) are set by the setting switch 62. The CPU 60 sends these setting values to a setting circuit 63 and an input/output circuit (I/O circuit).
O) Automatically read the data through the RAM 64, calculate the upper limit value and the lower limit value, and store them in the RAM 65. The PH detection value from the PH electrode 12 is converted to a level that can be post-processed by the PH signal processing circuit 66 and sent to the A/D.
It is converted into a digital signal by a converter 67,
It is stored in RAM65. The CPU 60 sends control signals via the I/O 64 and the drive circuit 68 to the injection flow rate adjustment section 50, the injection stop section 51, the on-off valves 52, 53, and so on.
Give to 54.

The control program stored in the ROM 61 includes a background routine and a timer 69.
It is distinguished from an interrupt routine that occurs every second. The same applies to the control program for the perfusate PH.
FIG. 2 is a flowchart showing the perfusate PH control interrupt routine. In a timer interrupt routine that occurs every 0.5 seconds, the value of the perfusate PH is A/D converted (S ₁ ) and stored in the RAM 65 as digital data. ( _S2 ).

After this, the CPU 60 inputs the A/D converted perfusate PH.
The value is compared with the alarm upper limit, and if PH data > alarm upper limit (7.7) (S ₃ ), the upper limit alarm flag is set (S ₄ ). If not, reset the upper limit alarm flag ( _S5 ).

Also, if PH data < alarm lower limit (7.1) (S ₆ )
A lower limit alarm flag is set ( _S7 ). If not, the PH is considered normal and the lower limit alarm flag is reset ( _S8 ). These are routines that check for alarms.

Following the above routine, an aperture section control routine (S ₁₀ ) is executed. This will be explained next. In this embodiment, the injection flow rate of the PH adjustment liquid is controlled by adjusting the degree of restriction of the injection flow rate adjustment section 50 of the injection passage.

In the aperture section control routine shown in FIG. 3, first, the current PH data and the control upper limit value are compared. If PH data>control upper limit value (S ₁ ), the motor of the aperture section is rotated forward (S ₂ ) to increase the aperture degree. This is done by operating the drive circuit by setting a certain bit of the I/O to 1. If not, compare the PH data with the control lower limit value,
If the PH data is less than the control lower limit value (S ₃ ), the motor of the aperture section is reversed (S ₄ ), and the degree of aperture is lowered. If not, it is determined that the PH is in the stable region and the motor is stopped ( _S5 ). As the degree of throttling increases, the injection flow rate of the PH adjustment solution decreases, resulting in a decrease in the amount of CO ₂ produced and a decrease in the PH of the perfusate. Furthermore, when the degree of restriction is decreased, the injection flow rate increases, so the amount of CO ₂ increases and the PH of the perfusate increases. The aperture control routine described above is performed every 0.5 seconds like the alarm check routine, so it is possible to perform fine control so that the perfusate PH always falls within the set range.

Next, in the background routine shown in FIG. 4, alarm processing is performed. This checks whether there is an upper limit alarm flag created in the timer interrupt routine (S ₁ ), and if there is an upper limit alarm flag (in this example, if flag = 0, there is no flag, otherwise As an alarm process (with a flag), the alarm buzzer is activated, and the on-off valves 52 and 53 are closed in FIG.
The on-off valve 54 is opened to bypass the perfusate to the dialyzer 2, and to indicate the bypass state, the bypass LED is turned on and the perfusate PH display is blinked ( _S2 ).

The side passage 55 and the on-off valve 54 constitute a side passage means,
The on-off valves 52 and 53 each constitute a closing means for closing the inflow or outflow passage of the dialyzer.

Furthermore, if there is no upper limit alarm flag, the presence or absence of an alarm flag is checked (S ₃ ), and if there is a lower limit alarm flag, in addition to the operation in S ₂ , the injection stop section 51 is operated and the PH adjustment liquid is injected. ( _S4 ).

If there is no lower limit alarm flag, turn off the alarm buzzer and release the irrigation fluid bypass (open/close valve 5
2, 53 and close the on-off valve 54). Also, turn off both the bypass LED and the injection stop section (S ₅ ).

When the PH of the perfusate exceeds the alarm upper limit value, the injection amount of the PH adjustment liquid is adjusted via the injection flow rate adjustment unit 50 in accordance with the difference from the PH control center value, and control to lower the PH is performed. Swells. When the PH of the perfusate is out of the lower alarm limit value, the on-off valves 52 and 53 are closed and there are no bicarbonate ions (HCO ₃ ^- ) migrating from the blood, so the PH of the perfusate remains unchanged.
does not recover. In this case, part of the irrigation fluid is replaced by controlling the on-off valve 7 for supplying the irrigation fluid to the diffusion tube 11 and the on-off valve 8 for discarding the irrigation fluid, and the pH gradually falls within the control range. be returned. At this time, a basic pH adjustment liquid such as a NaOH solution may be injected from the perfusion liquid supply section 10 instead of a new perfusion liquid. When the PH returns to the control range in this way, the bypass state is automatically canceled and the supply of perfusate to the dialyzer 2 is restarted.

Injection flow rate adjustment unit Injection flow rate adjustment unit 50 used in the embodiment shown in Fig. 1
An example is shown in FIG. An injection line tube 72 is fixed between a fixed head 70 and a movable head 71, and the forward and reverse rotations of the DC motor 73 are converted into forward and backward movements of the movable head 71 in the aperture direction, respectively, to adjust the degree of aperture. . That is, DC motor 7
3 and the movable head 71 are connected via a threaded portion 74 and a spring or bellows type coupling 75.
The threaded portion 74 is supported by a box portion 76, which is a fixed portion of the device, in engagement with a female thread cut therein. The threaded part 74 is the movable head 71
Although the front and back directions are restricted, rotation and sliding are freely connected. Therefore, the DC motor 7
3, the threaded portion 74 rotates and moves back and forth, and the movable head 71 follows this. The longitudinal displacement of the threaded portion 74 due to the rotation of the DC motor 73 is caused by the elastic coupling 75.
absorbed by.

FIG. 6 shows another embodiment of the injection flow rate adjusting section 50, in which a movable head 71 is connected to a female threaded section 78 by an arm 77. The rotation of the motor 73 is transmitted to the male threaded portion 79 by the coupling ring 75, and when the male threaded portion 79 rotates (the position of the male threaded portion remains unchanged), the female threaded portion 78 moves. The movement of the female threaded portion 78 is carried out by the arm 77 on the movable head 7.
1, but since it is centered around the fulcrum 80, when the female threaded portion 78 moves to the right (in the figure), the movable head 71 moves to the left, releasing the aperture of the tube 72. In the opposite case, close the tube.

FIG. 7 is a diagram showing still another embodiment of the injection flow rate adjustment section 50, in which, unlike FIG. 5, the movable head 71 moves parallel to the tube 72 rather than at right angles. By doing so, the tube is compressed and closed (other points are the same as in FIG. 5).

Second Embodiment FIG. 8 shows a block system diagram of the main parts of a second embodiment of this invention. Components that are the same as those in the embodiment shown in FIG. 1 are given the same reference numerals and redundant explanations will be omitted.
The parts omitted in this figure are the same as the conventional example shown in FIG.

In the case of this embodiment, the injection flow rate of the PH adjustment liquid is controlled by controlling the rotational speed of the tubing pump.

In this case, the control unit 40 has a D/A converter 9
0 is added. This part will be explained.

If PH data>control upper limit value, a value corresponding to the difference is output to the D/A converter 90. In other words, D/ when the PH data is within the control range.
In order to provide the D/A converter with a value obtained by subtracting this difference from the data provided to the A converter 90, the voltage supplied to the motor of the tubing pump, which is the injection flow rate adjustment section, is decreased, the rotation speed of the pump is decreased, and the PH The injection flow rate of adjustment fluid decreases.

Conversely, if the PH data < the control lower limit, the value corresponding to this difference is within the control range.
In order to provide the D/A converter with the value added to the value output to the A converter 90, the supply voltage of the tubing pump increases, the rotation speed of the pump increases, and the injection flow rate of the PH adjustment liquid increases.

Regarding the rotation speed control of the tubing pump,
It goes without saying that in addition to voltage control as in this embodiment, frequency control and phase control using a pulse motor are also possible.

Example Next, an example of controlling the perfusate PH according to the first example will be described.

The experiment was conducted using the apparatus shown in FIG. 1, and the dialyzer used was a cellulose hollow fiber type with a membrane area of 2.5 m ² . As the simulated blood, 30 perfusion fluids were used, and the HCO ₃ ^- concentration was 35.4 mEq/.
In this case, the carbon dioxide partial pressure PCO ₂ is 28.4 mmHg and the PH
is 7.73.

The pH adjustment liquid is 0.5NHC, and the blood pump flow rate is
200ml/min, irrigation fluid flow rate 500ml/min, added O ₂
The gas flow rate was 20 ml/min.

Further, the volume of the diffusion tube was 2.2, the injection flow rate adjusting section had the structure shown in FIG. 5, and the control program was in accordance with FIGS. 2 to 4. In addition, the control center value of PH was set to 7.55, and the control width was set to ±0.2. Note that the experiment time was 1 hour.

FIG. 9 shows the perfusate PH value every 5 minutes.

From FIG. 9, it can be seen that the PH value is 7.32 to 7.76, and is controlled almost within the control range.

"Effect of the invention" According to this invention, the PH of the perfusate can be controlled within the desired control range, so carbonic anhydrase does not deviate from its active region and carbon dioxide components in the blood are efficiently removed. In addition, there is no fear that the PH of the blood will fluctuate through the dialyzer.

In the event that the PH of the perfusate greatly deviates from the control range, an alarm will be issued and the perfusate passage will be bypassed in front of the dialyzer, and the inflow and outflow channels of the dialyzer will be blocked. It does not cause PH fluctuations and has no adverse effects on patients. Thus, this invention can significantly improve the safety of the lung assist device.

[Brief explanation of drawings]

FIG. 1 is a block system diagram showing the main parts of an embodiment of the lung assist device of this invention, FIG. 2 is a flowchart showing the perfusate PH control interrupt routine of the embodiment of FIG. 1, and FIG. 1 is a flowchart showing the control routine of the injection flow rate adjusting section of the embodiment, FIG. 4 is a flowchart showing the perfusate PH control background routine of the embodiment of FIG. 1, and FIGS. 5 to 7 are respectively Fig. 8 is a block system diagram showing the main parts of another embodiment of this invention, and Fig. 9 is a diagram showing the perfusion flow rate adjustment section of the embodiment shown in Fig. 1. Diagram showing experimental results of liquid PH control, No. 10
The figure is a block system diagram showing a conventional external circulation type lung assist device, and FIG. 11 is a waveform diagram showing the fluctuation characteristics of the perfusate PH in the conventional device shown in FIG. 2... Dialyzer, 7, 8... Open/close valve, 10... Irrigation fluid supply section, 11... Diffusion tube, 12... PH electrode,
19... CO ₂ concentration meter, 30... PH adjustment liquid supply section,
31...Pinch valve, 40...Control unit, 41...
... Display section, 42 ... Operation section, 50 ... Injection flow rate adjustment section, 51 ... Injection stop section, 52, 53, 54 ...
...Opening/closing valve, 55... Side channel, 60... Central processing section,
61... Read-only memory, 62... Setting switch, 63... Setting circuit, 64... Input/output circuit, 6
5... Read/write memory at any time, 66... PH signal processing circuit, 67... A/D converter, 68, 6
8'...Drive circuit, 69...Timer, 90...
D/A converter.

Claims (1)

[Scope of claim for utility model registration] The patient's extracorporeally circulating blood and perfusate are brought into contact with each other through a membrane within the dialyzer, and carbon dioxide components (bicarbonate ions and dissolved carbon dioxide) in the blood are transferred into the perfusate. After injecting the PH adjustment liquid into this perfusate, it is guided to the diffusion tube, and brought into gas-liquid contact with an inert gas to diffuse the carbon dioxide component as carbon dioxide gas, and the perfusate from which carbon dioxide gas has been removed is passed through the diffusion tube. and the above-mentioned dialyzer, an injection flow rate adjusting section for continuously adjusting the injection flow rate of the above-mentioned PH adjusting solution; an injection stop part that stops the injection of the pH adjustment liquid when the pH of the perfusate is substantially out of the pH range that can act as a catalyst to convert carbon dioxide into carbon dioxide; a bypass means for opening a valve inserted in a passage connecting the inflow passage of perfusate to the dialyzer and the outflow passage from the dialyzer, and simultaneously with the stop of the infusion, the connecting passage; On the dialysis side, a closing means for closing both the inflow passage and the outflow passage of the perfusate to the dialyzer, and the injection flow rate adjustment section, the injection stop section, the bypass means, and the closing means are controlled. 1. An extracorporeal circulation type lung assist device, characterized in that it is provided with a control means for.