JPH0463707B2 - - Google Patents

Description

[Detailed description of the invention]

(Object of the Invention) The present invention relates to a liquid membrane type extracorporeal circulation type lung assist device that regenerates and circulates dialysate. For patients with malabsorption, membrane-type lung assist devices, which cause less damage to the blood, are being used as devices for extracorporeally circulating the blood of patients and removing carbon dioxide components from the blood during the extracorporeal circulation. Conventionally, in this type of device, the injected gas and blood flow through a polymer lung with good gas permeability, and the dissolved gas in the blood passes through the membrane.
Gas-liquid film types, excluding CO ₂ , have been used. However, most of the carbon dioxide component to be removed is dissolved CO ₂
Since dissolved CO2 is dissolved in the blood as HCO ^- ₃ (bicarbonate ion) rather than as CO2, conventional devices that only remove dissolved _CO2 were extremely inefficient. Therefore, recently, using a hemodialyzer for artificial kidneys, blood is passed through one side of the membrane and dialysate is passed through the other side, and dissolved _CO2 and _HCO3 in the blood are transferred to the dialysate, and these CO2 are removed from the dialysate. ^- Unexamined Japanese Patent Application Publication No. 1983-2017 - Regenerating and circulating dialysate by diffusing it out of the system as ₂
19265 "Hemodialysis membrane oxygenator" has been proposed. However, the device disclosed in Japanese Patent Application Laid-Open No. 58-19265 has the following unresolved practical problems. In other words, water movement occurs across the membrane between the patient's blood and the dialysate based on the pressure difference, and water enters the blood and the blood becomes thinner, which can lead to various adverse effects such as destruction of blood cell membranes. be. Furthermore, since the CO ₂ removal flow rate depends on several factors such as blood flow rate and dialysate flow rate, it is necessary to appropriately control these factors, but this is difficult with this device, and CO ₂ removal cannot be performed efficiently. Furthermore, if the dialysate is used for a long period of time, it is not possible to maintain the dialysate temperature at an appropriate temperature, and it is difficult to confirm whether each operation and operating condition is normal, so careful monitoring by the operator is required, and the operator must perform appropriate operation. This imposes a significant burden on the operator, such as having to carry out procedures. The object of the present invention is to solve the above-mentioned problems in a liquid membrane type extracorporeal circulation type lung assist device that regenerates and circulates dialysate. (Structure of the Invention) The structure of the invention will be explained below based on the drawings. FIG. 1 shows an example of a piping system diagram of an apparatus according to the present invention. In FIG. 1, a patient's blood is sent to a dialyzer 2 by a blood pump 1, venous pressure and flow rate are measured at a drip chamber 3, and the blood is extracorporeally circulated through a venous pressure regulator 4. On the other hand, the dialysate is passed through a flow meter 6 to the dialyzer 2 by a dialysate pump 5.
The dialysate pressure is measured by the dialysate pressure measuring device 7 in the outlet flow path, and the dialysate pressure is measured by the dialysate pressure measuring device 7 at the outlet flow path, and the dialysate pressure is measured by the dialysate pressure measuring device 7 at the outlet flow path.
through which it is introduced into the dissipation tube 10 and circulated through the PH and dialysate temperature measurement 11. in the blood
HCO ₃ ^- and dissolved CO ₂ move to the dialysate in contact with the dialyzer 2 through the membrane, and the dialysate flows into the diffusion column 1.
0, HOC ₃ ^- is converted to CO ₂ by the catalytic action of carbonic anhydrase contained in the dialysate, and the pressure regulator 12, stop valve 13, flow control valve 14, and flow meter 15. Gas-liquid contact with inert gas 17 such as O ₂ sent through check valve 16
Dissipated as _CO2 . The CO ₂ concentration in the emitted gas is
It is measured by a CO ₂ concentration meter 18. Further, a buffer solution 19 for adjusting the pH of the dialysate can be added to the diffusion tube 10 via a pinch valve 20. Now, the blood pressure is controlled by the venous pressure regulator 4, and the blood pump 1 and the dialysate pump 5.
The rotation of the drive motor is monitored by monitoring the rotation of a disk with equally spaced holes attached to the rotating shaft of the drive motor using a photo sensor, and each flow rate control is controlled by changing the supply voltage to the drive motor. Do it under control. Dialysate temperature and PH are measured in the measurement section 1.
1, the temperature is controlled by a heater 9, and the pH is controlled by a pinch valve 20. The flow rate of the additive gas is monitored by a flow meter 15 such as a hot wire flow meter, and the flow rate is controlled by controlling the voltage supplied to the flow control valve 14 and adjusting its opening degree. The movement of water between the blood and the dialysate through the membrane of the dialyzer depends on the pressure difference between the blood and the dialysate, that is, the overpressure of the dialyzer. When the overpressure is positive, water is removed from the blood, and when it is negative, water enters the blood. Therefore, if water is to be removed from the blood depending on the patient's condition, the overpressure is set to a certain high value, and on the other hand, if water is not to be removed, the overpressure is controlled to around 0. Further, the amount of CO ₂ removed by the diffusion tube 10 depends on the capacity of the dialyzer 2 and the diffusion tube, but also on the extracorporeal circulation blood flow rate, the dialysate flow rate, and the added gas flow rate. The larger each of these amounts is, the larger the CO ₂ removal flow rate becomes. Therefore, in order to efficiently remove CO ₂ under optimal conditions according to the patient's condition and to downsize the entire device, the extracorporeal circulation blood flow, dialysate flow rate, and inert gas flow rate are appropriately controlled. In this invention, these controls are realized using a microcomputer. FIG. 2 shows a block diagram of the control system in the apparatus of the present invention. In FIG. 2, extracorporeal circulation blood flow 21, venous pressure 22, dialysate flow rate 23, dialysate pressure 2
4. Signals from each sensor for patient temperature 25, dialysate pH 26, dialysate out 27, inert gas flow rate 28, and CO ₂ concentration in the diffused gas 29 are brought to a signal level that can be post-processed by the detection circuit 30. be adjusted. After that, multiplexer 31, sample hold circuit 3
2, it is converted into a digital signal by the A/D converter 33 and stored in the RAM 34. On the other hand, the operation section 35 includes a sequence switch for setting the operating mode of the apparatus as well as a digital switch for setting the physical quantity to be controlled. In addition, a display circuit 36 and a digital display section 3 are used to display each state quantity.
There are 7. In addition, the ROM38 stores a program that is in charge of overall control, and based on this program,
A CPU 39 controls each process. The other I/O40
Input of switch data, output of control signals, etc. are controlled. The control output signal from the I/O is a transistor, solid. State. In addition to the interface section 4 consisting of relays, etc., there are a blood pump control circuit 42, a vein control circuit 43, a dialysate pump control circuit 44, a heater control circuit 45, and a PH control circuit 46.
and an inert gas flow rate control circuit 47 through the blood pump 1, venous pressure regulator 4, dialysate pump 5, heater 9, and pinch valve 2, respectively.
0 and the flow rate control valve 14 to perform each control. By the way, control of overpressure in a dialyzer can be achieved by controlling either venous pressure or dialysate pressure.
In this figure and FIG. 2, a venous pressure regulator is used to control venous pressure. As the venous pressure regulator, a method is shown in which the degree of pressure closure of the venous blood tube is adjusted using a clamp head, but a double-pipe method in which a tube is provided outside the blood tube to increase or decrease the pressure inside the tube may also be used. The above-mentioned adjustment of the degree of closure is carried out by moving the clamp head forward, backward, and stopping, respectively, by rotating the motor forward, reverse, and stopping. FIG. 3 shows a flowchart of an algorithm for controlling overpressure using a microcomputer. That is, in step _S1 , venous pressure data a (mmHg)
Import the dialysate pressure data b in step _S2 .
(mmHg) and step _S3 c=a-b
is calculated, and in step _S4 it is determined whether C is negative or not.
If it is negative, step _S5 advances _the clamp head of the venous regulator to increase the degree of pressure closure of the venous blood tube, increasing the venous pressure. (mmHg)−
5}, and if it is "small", proceed to step _S5 , and if "not small", go to step _S7 to judge whether C is larger than d+5, and if "large", proceed to step S5. In step _S8 , the clamp head of the venous pressure regulator is retracted to reduce the degree of pressure occlusion of the venous blood tube as a retreat mode, which lowers the venous pressure, and when the venous pressure is not high, the stop mode stops the clamp head of the venous pressure regulator. Keep venous pressure current. Next, the amount of CO ₂ removed by the diffusion tube is determined by the product of the CO ₂ concentration in the diffused gas in the diffusion tube and the inert gas flow rate, so these two amounts are detected and processed by a microcomputer to eliminate CO 2. ₂ removal flow rate.
This CO ₂ removal flow rate is compared with a preset value, and if it differs from the set value, the extracorporeal circulation blood flow, dialysate flow rate, or inert gas flow rate is adjusted and controlled according to the patient's condition and treatment conditions. For example, if the patient's blood pressure is low and only a small amount of extracorporeal blood flow can be obtained, the dialysate flow rate is increased to promote the movement of HCO ₃ ^- and dissolved CO ₂ from the blood, and at the same time, the dialysate's HCO ₃ ^- and In order to further reduce the dissolved CO ₂ concentration, the inert gas flow rate is increased and CO ₂ removal is actively carried out within the diffusion cylinder, thereby increasing the efficiency of CO ₂ removal. Conversely, in the case of patients who can increase the extracorporeal circulation blood flow, the dialysate flow rate and inert gas flow rate do not need to be increased as in the previous case in order to increase the CO ₂ removal efficiency. Control it like that. FIG. 4 shows a flowchart for controlling the extracorporeal circulation blood flow, dialysate flow rate, and inert gas flow rate using a microcomputer to efficiently remove CO ₂ . That is, in step _S1 , the CO ₂ concentration data
Inert gas flow rate data y is acquired in _S2 , extracorporeal circulation blood flow data is acquired in step _S3 , dialysate flow rate data is acquired in step _S4 , and dialysate flow rate data is acquired in step _S5.
Calculate the CO ₂ removal flow rate z = x + y in step S ₆ , and determine whether z is smaller than the set value u.
If it is "small", it is determined in step _S7 whether or not the extracorporeal circulation blood flow can be increased, and if it is "increasable", the blood pump is controlled to increase the flow rate in step _S8 , and if it is determined that "increase is not possible". At step _S9 , the dialysate pump and flow control valve are controlled to increase the dialysate flow rate and inert gas flow rate. On the other hand, if z is "not smaller" than u, it is determined in step _S10 whether z is larger than u, and if it is "larger", it is determined in step _S11 whether or not the extracorporeal circulation blood flow can be reduced, If possible, the blood pump is controlled to reduce its flow rate in step _S12 ; if not, the dialysate pump and flow control are controlled to reduce the dialysate flow rate and inert gas flow rate in step _S13 . reduce On the other hand, if it is determined in step _S10 that it is not large, the process advances to step _S14 and the current state is maintained. Additionally, when carbon dioxide components are removed from the dialysate using a diffusion cylinder, its pH increases. Carbonic anhydrase, a catalyst that promotes the dehydration reaction that releases CO ₂ from carbonic acid, is contained in the dialysate, so it is necessary to control the pH of the dialysate to the active range of this enzyme. be. Therefore, in order to adjust the pH to a value close to the optimal value of 7.4 in living organisms, the amount of a pH adjustment buffer solution such as dilute hydrochloric acid solution added is controlled. FIG. 5 shows a flowchart of dialysate pH control. In other words, in step _S1 in Fig. 5, the dialysate
Take in the PH data, determine whether it is greater than the set value in step _S2 , and if it is "greater than", proceed to step _S3.
Open the pinch valve and add the buffer solution for pH adjustment, and if it is "not above" in step _S2 , close the pinch valve in step _S4 . Furthermore, the dialysate temperature is controlled in the same manner, and a flow chart thereof is shown in FIG. In other words, in FIG. 6, dialysate temperature data is taken in in step _S1 , and it is determined in step _S2 whether or not it is greater than or equal to the set value, and if it is, the heater is turned off in step _S3 .
If step _S2 shows "not above", turn on the heater in step _S4 . By the way, the control program stored in the ROM mentioned above consists of a main routine and an interrupt routine, which are shown in Figures 7 and 8, respectively.
The flowchart is shown in the figure. In Fig. 7, first, in step _S1 , initial settings such as clearing the RAM and clearing the I/O output port are performed, and then the state of the sequence setting switch is changed to the I/O output port.
Input from O, and in steps S ₂ to _{S 5} determine the mode of stop, power on, disinfection, preparation, and start.
In step _S6 and step _S10 , each predetermined control such as activating a buzzer when the power is turned on, rotating the dialysate pump at a constant speed in the preparation mode, and keeping the opening degree of the flow control valve constant, etc. Perform processing corresponding to the mode. It also performs alarm processing in the preparation and start modes as shown in Table 1.

【table】

[Table] In the interrupt routine shown in Figure 8, first, in step _S1 , the state of the CPU registers immediately before the main routine interrupt is saved and held, and then
In step _S2 , other interrupt generation is prohibited. Next, in step _S3 , data of each setting switch is taken in, and in step _S4 , analog signals from each sensor and detection circuit are A/D converted. After this step S ₅
Each mode is determined in steps S9 to _S8 , and processing in each mode is performed in steps _S9 to _S11 . That is, in the start mode of step _S9 , various displays are performed, the presence or absence of an alarm is checked, and the venous pressure regulator, blood and dialysate pump, heater, pinch valve, and flow control valve are controlled. Similarly, each display is performed in the stop mode of step _S10 , and each display is performed in the preparation mode of step _S11 , the presence or absence of an alarm is checked, and the venous pressure regulator and heater are controlled. After performing these steps, proceed to step _S12 .
Restore the contents of the CPU register and proceed to step _S13
After disabling interrupts with , return to the address of the next instruction where the main routine interrupt occurred. This interrupt routine also plays the role of a timer, so it occurs periodically, such as every 0.5 seconds or every 1 second.
Each of the control routines shown and described above in FIGS. 3 to 6 is included in this interrupt routine. Table 2 shows the input/output status in each mode detailed above.

【table】

[Table] (Experiment example) In the apparatus shown in Figure 1, the dialyzer was made of cellulose hollow fiber with a membrane area of 2.5 ^m2 , and the dissipation cylinder was a cylinder type with a side of 13 cm and a height of 20 cm. I conducted an experiment. As a blood substitute, a bicarbonate ion-rich solution obtained by adding bicarbonate ions to a general dialysate was used, while the dialysate was a standard dialysate with 1.6
was added with 16 mg of carbonic anhydrase. Furthermore, a 0.5N hydrochloric acid solution was used as the pH adjustment buffer, and 100% O ₂ was used as the inert gas. Overpressure, CO ₂ removal flow rate and dialysate PH were 0 mmHg and 50 ml/min, respectively.
and set it to 7.4. At this time, the extracorporeal circulation blood flow, dialysate flow rate, and inert gas flow rate are approximately 200 ml/min and 500 ml/min, respectively.
ml/min and 20/min, overpressure, CO ₂
Removal flow rate and dialysate pH are each 0~
It was controlled within the range of 5mmHg, 30-70ml/min and 7.2-7.5. Table 3 illustrates data on the CO ₂ partial pressure and HCO ₃ ^- concentration of the blood and dialysate at the inlet and outlet of the dialyzer in this experiment, as well as the CO ₂ removal flow rate from the diffusion cylinder.

[Table] (Clinical example) The clinical trial was conducted using the same equipment as in the previous example. The patient's preclinical blood _CO2 partial pressure was 66.8 mmHg, and the _HCO3 ^- concentration was
PH was calculated to be 7.390 at 39.1 mEq/. The dialysate used was a standard dialysate 1.6 with 20mg of carbonic anhydrase added, the pH adjustment buffer was a 0.5N hydrochloric acid solution, and the inert gas was 100% _O2. there was. and overpressure, _CO2 removal flow rate and dialysate PH, respectively.
It was set at 0mmHg, 20ml/min and 7.4. At this time, the extracorporeal circulation blood flow is 30ml/
min, maximum 80ml/min, average approximately 50ml/min,
Dialysate flow rate and inert gas flow rate are approximately
They were 500ml/min and 25/min. And the overpressure and dialysate PH are controlled to 0-5mmHg and 7.2-7.6, respectively, and the _CO2 removal flow rate is maximum
It was 24.3ml/min. After one hour of clinical treatment, the _partial pressure of CO2 in the patient's blood and
HCO ₃ ^- concentration is 43.6 mmHg and
It decreased to 26.0mEq/. The blood pH at this time was calculated to be 7.398, which was extremely close to the ideal value. (Effects of the Invention) As described in detail above, according to the present invention, in a liquid membrane type extracorporeal circulation pulmonary assist device that regenerates and circulates dialysate, venous pressure, extracorporeal circulation blood flow, By controlling the liquid flow rate and inert gas flow rate to the optimal state according to the condition of the patient, etc., it is possible to control overpressure and CO ₂ removal flow rate.
Dialysate temperature and PH can also be controlled with precision.
Safe and efficient operation and management of the device can be extremely facilitated, and the burden on operators and patients in hospitals can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a piping system diagram of the device according to the present invention, Fig. 2 is a block diagram of its control system, Fig. 3 is a flowchart of overpressure control, and Fig. 4 corresponds to the set value of the CO ₂ removal flow rate. Flow chart for controlling extracorporeal circulation blood flow, dialysate flow rate and inert gas flow rate,
5 and 6 are flowcharts for controlling the dialysate PH and temperature, respectively, and FIGS. 7 and 8 are flowcharts for the main routine and interrupt routine of the control program, respectively. 1... Blood pump, 2... Dialyzer, 3... Drip chamber, 4... Venous pressure regulator, 5... Dialysate pump, 6... Flowmeter (dialysate), 10... Diffusion barrel, 14... ...Flow rate control valve, 15...Flow meter (inert gas), 17...Inert gas, 18...CO ₂
Densitometer, 34...RAM, 38...ROM, 39
... CPU, 40 ... I/O, 41 ... Interface section, 42 ... Blood pump control circuit, 43
... venous pressure control circuit, 44 ... dialysate pump control circuit, 47 ... inert gas flow rate control circuit.

Claims (1)

[Claims] 1. The patient's extracorporeally circulating blood and dialysate are brought into contact with each other through a membrane in the dialyzer, and the carbon dioxide component in the blood is moved into the dialysate, and this is transferred to the dialysate using an inert gas in a diffusion tube. It is removed by bringing it into gas-liquid contact with and dissipating it as CO ₂ .
A pulmonary auxiliary device that regenerates and circulates dialysate includes a means for controlling the filtration pressure of the dialyzer, and a means for controlling the filtration pressure by the means, and for removing CO ₂ components transferred from the patient's blood in a diffusion cylinder. An extracorporeal circulation type lung support device, comprising: means for controlling the flow rate of CO ₂ removal during removal;