JP2000210382A - Module for gas exchange - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve gas exchange efficiency and to eliminate blood stagnation parts by adopting the structure which is substantially the same in hollow fiber density and is higher in blood velocity toward an outlet side from a blood inlet side. SOLUTION: The blood velocity of a module for gas exchange in which the blood is passed to the outside surface of hollow fibers 1 and gas is passed to the inner side is made higher toward the outlet side from the inlet side, by which the laminar films are decreased from the blood inlet side toward the outlet side and even if the oxygen partial pressure difference between the venous blood and the gas is made smaller toward the outlet side from the blood inlet side, the oxygen moving resistance to the venous blood from the gas may be decreased. Namely, the gas exchange module is capable of preventing the decrease of the migration of the oxygen to the venous blood from the gas generated toward the outlet side from the blood inlet side and preventing the degradation in oxygenation efficiency. The means for increasing the blood flow velocity includes the adoption of a structure to diminish a blood flow passage area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas exchange module having a high gas exchange rate and having no blood stagnation, and more particularly to a heat exchanger for an artificial lung and an artificial heart-lung circuit.

[0002]

2. Description of the Related Art FIG. 1 is a view schematically showing a basic structure of a conventional gas exchange module in which blood flows on the outer surface of a hollow fiber 1 and gas flows on the inside of the hollow fiber 1. The yarn 1 is bundled and fixed by a potting adhesive layer 5.

Conventionally, in a membrane oxygenator using a gas exchange membrane having the above-described structure, oxygen is added to the blood with a blood-side membrane (formed on the contact surface between the blood and the hollow fiber). The blood layer with almost no flow) is the main cause of oxygen transfer resistance, and for the removal of carbon dioxide in the blood, the difference between the concentration of carbon dioxide in the blood and the concentration of carbon dioxide on the gas side becomes smaller, It is known to be the main cause of carbon dioxide migration resistance.

[0004] In order to solve the above-mentioned problems of the difference in the membrane resistance and the carbon dioxide concentration on the blood side and to improve the gas exchange performance, both the gas flow rate and the blood flow rate may be increased. However, as the gas flow rate and the blood flow rate are increased, the pressure loss also increases, and disadvantages such as hemolysis on the blood side and the generation of microbubbles on the gas side begin to appear. The upper limit is limited. Further, there is a problem that blood is difficult to flow around the boundary between the hollow fiber 1 and the potting adhesive layer 5 and blood is easily stagnated, so that a thrombus is easily generated.

[0005]

SUMMARY OF THE INVENTION The present invention does not cause inconveniences such as hemolysis on the blood side and generation of microbubbles on the gas side. It is an object of the present invention to provide a gas exchange module improved in gas exchange performance, in particular, an artificial lung, and a heat exchanger for an artificial heart-lung system circuit having the same structure as the gas exchange module.

[0006]

Means for Solving the Problems The gas exchange action will be described when the gas exchange module is used as an artificial lung. 1. Oxygen gas exchange action Venous blood with a low oxygen partial pressure flows into the oxygenator. On the other hand, pure oxygen is usually used for the replacement gas. Therefore, near the entrance of the artificial lung, the oxygen partial pressure difference between the two sides through the membrane is large, so that oxygen can be sufficiently transferred into the blood even if a small amount of the membrane exists. However, oxygen is added to the venous blood toward the outlet side, the oxygen partial pressure of the venous blood increases, the oxygen partial pressure difference between the venous blood and the gas decreases, and from the gas to the venous blood when a membrane exists. Oxygen transfer decreases.

[0007] 2. Carbon dioxide gas exchange effect Venous blood with a high carbon dioxide partial pressure flows into the oxygenator. Therefore, near the inlet of the artificial lung, there is a large difference between the carbon dioxide partial pressures on both sides through the membrane, so that even if the carbon dioxide partial pressure on the gas side is slightly high, the carbon dioxide can be sufficiently transferred to the replacement gas side. However, as it goes to the outlet side, carbon dioxide is gradually removed, the carbon dioxide partial pressure in the blood is low near the outlet side, and if the gas side flow rate is kept constant, the blood carbon dioxide is released to the gas side. Transitions are decreasing.

Therefore, a first feature of the present invention is that in a gas exchange module in which blood flows on the outer surface of a hollow fiber and gas flows inward, the blood flow velocity in the gas exchange module goes from the inlet side to the outlet side. The blood pressure decreases from the blood inlet side to the outlet side, and the oxygen partial pressure difference between venous blood and gas decreases from the blood inlet side to the outlet side. Even providing a gas exchange module that can reduce the resistance of oxygen transfer from gas to venous blood,
It is to solve the above problem. That is, the gas exchange module of the present invention can prevent a decrease in the transfer of oxygen from gas to venous blood, which occurs from the blood inlet side to the blood outlet side, and can prevent a decrease in oxygenation efficiency.

As means for increasing the blood flow rate from the inlet side to the outlet side of the gas exchange module, as shown in FIG. 2, the blood flow area increases from the blood inlet (upper) side to the outlet side. Therefore, a structure having a smaller size can be given.

As means for increasing the blood flow rate from the inlet side to the outlet side of the gas exchange module, the density of the hollow fibers in the gas exchange chamber of the gas exchange module is low at the blood inlet side and high at the outlet side. However, the structure becomes complicated, and the assembly takes time. In other words, the gas exchange module of the present invention does not change the density of the hollow fibers in the gas exchange chamber of the gas exchange module so that the density is low on the blood inlet side and dense on the outlet side. Even at substantially the same density, the blood flow velocity in the gas exchange chamber can be increased from the entrance side to the exit side. For example, as described above, when assembling the gas exchange module, a hollow fiber for a commercially available gas exchange module is used.
It may be simply arranged in the gas exchange chamber as a shorter structure from the blood inlet side to the outlet side, in this case,
Assembly of the gas exchange module is extremely simple.

A second feature of the present invention is that in a gas exchange module in which blood flows on the outer surface of a hollow fiber and gas flows on the inner side, the gas flow rate per unit time increases from the blood inlet side to the blood outlet side. The present invention relates to a gas exchange module having a larger structure.

As a structure in which the gas flow per unit time flowing inside the hollow fiber increases from the blood inlet side toward the outlet side, for example, as shown in FIG. This can be achieved by adopting a structure in which the length is reduced from the blood inlet side to the blood outlet side.

In the conventional gas exchange module, the partial pressure of the carbon dioxide in the blood is low near the outlet side, and the transfer of the carbon dioxide in the blood to the gas side decreases when the gas-side flow rate remains constant. However, as described above, the gas exchange module of the present invention has a structure in which the length of the hollow fiber in the gas exchange chamber of the gas exchange module is reduced from the blood inlet side to the blood outlet side. In the case of the hollow fiber on the outlet side, the flow resistance of the gas flowing through the hollow fiber is reduced as compared with the hollow fiber on the inlet side, the gas flow rate flowing through the hollow fiber is increased, and the gas flow rate per unit time is increased. Therefore, it is possible to prevent a decrease in the transfer of blood carbon dioxide to the gas side as approaching the outlet side of the gas exchange module.

A third feature of the present invention is that, as shown in FIG. 2, the boundary portion 6 formed by the hollow fiber and the potting adhesive layer 5 in the gas exchange chamber has a tapered shape. For the module. The tapered shape of the boundary part 6 may be configured to have a curved part instead of a straight part.

The gas exchange module as described above is similar to the conventionally known oxygenator module in that the boundary 6
However, in the case of a vertical boundary portion, blood is difficult to flow (easily stagnates) around the boundary portion between the hollow fiber and the adhesive for bundling and fixing the hollow fiber, and thrombus is likely to be generated. In the case of a tapered boundary as described above, the effect of washing out the stagnant blood is produced at the boundary, and the effect of reducing the formation of thrombus around the boundary between the hollow fiber and the adhesive that binds and fixes the hollow fiber. Can be played.

Although the gas exchange module of the present invention can provide excellent effects even when each of the structures based on the requirements of the first to third features is independently employed, the first to third features can be obtained. A gas exchange module (for example, having the configuration shown in FIG. 2) employing a combination of structures based on the characteristic requirements can provide significantly superior effects as compared with conventionally known gas exchange modules.

The hollow fibers used in the gas exchange module of the present invention include cellulose acetate, cuprammonium cellulose, polyacrylonitrile, trimethyl methacrylate, polyethylene, polyvinyl alcohol,
A porous film made of polypropylene or the like, a porous film made of silicone or the like, or a film formed of the former two composite films can be used.

In the above description, the artificial lung is described as the gas exchange module. However, the configuration of the gas exchange module of the present invention is different from that of another fluid treatment apparatus using a porous hollow fiber having permselectivity. For example, dialysis, ultrafiltration,
The present invention can be applied to a fluid treatment apparatus using hollow fibers such as reverse osmosis dialysis.

Further, a module having the same structure as the gas exchange module of the present invention, that is, the first
In the module having the structure of the above-described (1) to (3), if a tube for a heat exchange module, for example, a metal needle tube or a plastic tube is used instead of the hollow fiber, and if a cooling medium is used instead of the gas, heat exchange can be performed. Module, ie
It can also be used as a heat exchanger, and in this case, the same effect as when it is used with the gas exchange module can be obtained.

In particular, as shown in FIG. 4, if this type of heat exchanger is used integrally with the gas exchange module of the present invention, the heat exchanger of the present invention has the advantages described in the first to third aspects. Since it is not necessary to separately provide a heat exchanger for the cardiopulmonary circuit, the circuit can be downsized. However, in the apparatus shown in FIG. 4, the heat exchanger is provided integrally with the upper part of the gas exchange module, but the heat exchanger may be provided integrally with the lower part of the gas exchange module. Alternatively, the gas exchange module does not necessarily have to be used integrally with the gas exchange module, and may be used in combination with a conventionally known gas exchange module.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIGS. 2 and 3 show a gas exchange module having a trapezoidal gas exchange structure in which the length of a hollow fiber 1 in a gas exchange chamber 2 decreases from the blood inlet side to the blood outlet side. Module. In the trapezoidal gas exchange module, both the upper surface and the lower surface are rectangular. However, the shapes of the upper surface portion and the lower surface portion are not limited to rectangular shapes, and may be arbitrary shapes. Further, the number of hollow fibers per unit area of the cross section of the portion is substantially the same regardless of the portion of the cross section.

Embodiment 2 FIG. 4 shows that the gas exchange module and the heat exchanger are arranged from the inlet side of the heat exchanger to the outlet side of the gas exchange module. It is integrated so as to have a structure in which the length of 1 is short.

[0024]

According to the present invention, a gas exchange module having a good gas exchange rate and having no blood stagnation portion, in particular, an artificial lung can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a conventional gas exchange module and a gas exchange action of the module. (A) It is the schematic diagram explaining the gas exchange action of the whole module. (B) It is the schematic diagram explaining the gas exchange action per one hollow fiber.

FIG. 2 is a schematic diagram illustrating a gas exchange module of the present invention and a gas exchange action of the module.

FIG. 3 is a sectional view taken along line AA of the gas exchange module of FIG. 2;

FIG. 4 is a diagram in which the gas exchange module of FIG. 3 is integrated with a heat exchanger.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Hollow fiber 2 Gas exchange room 3 Needle tube of heat exchanger 4 Room of heat exchanger 5 Potting adhesive layer 6 Boundary part formed by hollow fiber and potting adhesive layer 5

Claims (10)

[Claims] 1. A gas exchange module in which blood flows on the outer surface of a hollow fiber and gas flows on the inner side, wherein the density of the hollow fibers is substantially the same, and the blood flows from the blood inlet side to the blood outlet side. A gas exchange module with a structure that increases the flow rate. 2. A gas exchange module in which blood flows on the outer surface of a hollow fiber and gas flows on the inside, wherein the gas flow per unit time increases from the blood inlet side to the blood outlet side. Module. 3. A gas exchange module in which blood flows on the outer surface of a hollow fiber and gas flows on the inner side, wherein the blood flow speed increases and the gas flow rate increases from the blood inlet side to the blood outlet side. Gas exchange module. 4. The structure according to claim 1, wherein the blood flow speed increases from the blood inlet side to the outlet side, and the blood flow area decreases from the blood inlet side to the blood outlet side. Gas exchange module. 5. A structure in which the gas flow rate increases from the blood inlet side to the blood outlet side is such that the length of the hollow fiber is
The gas exchange module according to any one of claims 2 to 4, wherein the gas exchange module has a structure that becomes shorter from the blood inlet side to the blood outlet side. 6. A structure in which the length of the hollow fiber is gradually reduced from the blood inlet side to the blood outlet side.
A gas exchange module as described. 7. The gas exchange module according to claim 2, wherein the hollow fibers have substantially the same density. 8. The gas exchange module according to claim 1, wherein a boundary surface between the gas exchange chamber and the adhesive layer of the hollow fiber is tapered. 9. A heat exchanger for a cardiopulmonary bypass circuit having a configuration similar to that of the gas exchange module according to claim 1, wherein the hollow fiber is a needle tube or a plastic tube. 10. A heat exchanger, wherein the gas exchange module according to any one of claims 1 to 8 and the heat exchanger according to claim 9 are integrated. Integrated gas exchange module.