JPH04109956A - Hollow yarn type mechanical lung - Google Patents

Abstract

PURPOSE:To obtain a mechanical lung whose pressure loss is small even with a high average rate of filling and which would not cause channelling and whose gas exchange performance is high by filling substantially the whole inner space of a casing with a bundle of hollow yarn. CONSTITUTION:A bundle 1 of hollow yarn having one or plural films of hollow yarn gathered into a traverse roll and arranged as needed is enclosed in a casing 2 and fixed to near both ends of the casing by partition heads 3,4 each made of potting material while both ends of the film of hollow yarn are opened. Head caps 7,8 each communicated with the inner space of the film of hollow yarn and having an inlet 5 and an outlet 6 respectively for oxygen-contained gases are mounted to the respective partition walls 3,4 An inlet 9 and an outlet 10 for blood flow are attached to the center portion of one end of the casing and to near the partition wall at the other end, respectively. Blood is introduced from the blood inlet 9 through a blood port and allowed to flow through a space formed by the external wall of the film of hollow yarn and the inner wall of the casing and is discharged from the blood outlet 10. Since there is no possibility of the passage of the blood being blocked nor narrowed at near the blood inlet, loss of pressure can be minimized and channelling would not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hollow fiber membrane oxygenator that has low pressure loss, high gas exchange efficiency, is extremely compact, and has a small blood filling volume.

[Conventional technology and its problems]

TECHNICAL FIELD The present invention relates to a so-called external perfusion type hollow membrane oxygenator in which blood is circulated outside the hollow fiber membrane and oxygen-containing gas is circulated inside the hollow fiber membrane. Compared to the so-called internal perfusion system, which circulates blood inside a hollow fiber membrane, this type of oxygenator generally reduces pressure loss and prevents channeling (a phenomenon in which blood flows locally and unevenly). Furthermore, it is possible to achieve a well-balanced improvement in gas exchange efficiency.

Artificial lungs can be roughly divided into bubble type and membrane type oxygenators, but the bubble type and gas exchange type oxygenator, which uses a gas exchange membrane, are more physiological and have less undesirable effects on the blood. There are advantages.

Demolding oxygenators mainly use hollow fiber membranes to perform blood gas exchange through the hollow fiber membranes. In addition, as methods for blood to flow into the artificial lung, there are two methods: an internal perfusion method that allows blood to flow inside the hollow fiber membrane and gas to the outside, and an external perfusion method that allows blood to flow outside the hollow fiber membrane and gas to the inside. be. In the former case, since blood flows inside the extremely thin hollow fiber membrane of several tens to hundreds of micrometers, the pressure loss during blood circulation is large, which may cause damage to blood cells. In addition, in recent years, centrifugal pumps or pulsatile flow pumps have become popular, and when using these pumps for extracorporeal circulation, it is desirable that the pressure loss in the oxygenator lung be as small as possible. External perfusion is also preferred. The external perfusion method is more advantageous than the internal perfusion method in terms of pressure loss, blood cell damage, etc., but because the degree of freedom of the blood flow path is large, it is likely that blood will drift unbalanced. Furthermore, if an attempt is made to improve gas exchange efficiency or uneven flow by increasing the filling rate of the hollow fiber membrane, pressure loss will increase. In this case, if an attempt is made to solve the above problem by increasing the membrane area, the amount of blood filled in the oxygenator will increase, making it difficult to perform extracorporeal circulation without blood transfusion.

The above-mentioned problems are greatly affected by the state of the thread arrangement of the hollow membrane, the filling rate, the position of the blood inlet and outlet, the blood flow path, and the like. As a countermeasure, conventional methods include increasing the membrane area or increasing the flow path area to improve the gas exchange rate and pressure loss, and flowing blood from the side of the hollow fiber bundle to reduce pressure loss. Methods are known. However, although the former method has a low pressure drop, it has the disadvantage of a large blood filling volume, while the latter method has a low pressure drop compared to the internal perfusion method, but is difficult to adapt to pulsatile flow pumps, etc. be.

On the other hand, in order to prevent uneven flow of blood and obtain high gas exchange performance, a method in which a hollow fiber membrane is wound around a cylindrical object has been proposed, but in this case, blood suddenly flows into the hollow fiber bundle. ,or,
The flow path also becomes narrow rapidly, resulting in a large pressure loss. To prevent this, if the blood flow path is widened, the size of the artificial lung increases.

[Means to solve the problem]

An example of the membrane oxygenator of the present invention is shown in FIG.

A hollow fiber bundle 1 in which one or more hollow fiber membranes are bundled and arranged in a cross-wound pattern is housed in a casing 2, and the hollow fiber bundle is placed near both ends of the casing with both ends of the hollow fiber membranes open. It is fixed by a partition wall 3.4 made of potting material. Bulkhead 3
．． 4 is fitted with a head cap 7.8 having an inlet 5 and an outlet 6 for oxygen-containing gas, communicating with the interior space of the hollow fiber membrane. On the other hand, a blood inlet 9 and an outlet 10 are installed at the center of one end of the casing and near the partition wall at the other end.

In FIG. 1, blood is introduced from a blood port 9 through a blood port, flows through a space formed by the outer wall of the hollow fiber membrane and the inner wall of the casing, and is discharged from a blood outlet 10. Since there is a space in the vicinity of the blood inlet where no hollow fiber membrane exists, this is very preferable from the viewpoint of reducing pressure loss and preventing uneven flow. That is, the flow path of blood is not sharply bent or narrowed near the blood inlet, so pressure loss can be minimized.
Moreover, channeling does not occur.

The hollow fiber membrane may be bundled and distributed substantially parallel to the casing, or may be bundled and distributed in a twill shape,
In order to prevent uneven flow (channeling) of blood, it is preferable that the threads are bundled and distributed in a cross-wound manner.

In the example shown in Fig. 1, there is a space near the blood inlet where no hollow fiber membrane exists, but the filling rate of the hollow fiber membrane is
The structure may have a sparse to dense distribution from the center of the hollow fiber bundle toward the inner wall of the casing, or the filling rate of the hollow fiber membrane may vary from the blood inlet side to the other side.
The hollow fiber bundle may have a sparse to dense distribution in the fiber length direction. Regardless of the structure, the same effects of reducing pressure loss and preventing channeling can be obtained.

Considering the average filling rate of the entire hollow fiber bundle,
At a low filling rate, the pressure loss is low even at a high blood flow rate (3 to 5!/min), but because the blood flow path area becomes large, the blood does not spread throughout the hollow fiber bundle, and channeling This tends to result in poor gas exchange performance. On the other hand, when the filling factor is increased (for example, 0.55 to 0.6 or more), the gas exchange ability is improved, but the blood flow path area becomes small, resulting in a large pressure loss. The artificial lung of the present invention solves the above problems by having the above-described structure, and has a small pressure loss despite having a high average filling rate.
Does not cause channeling and has high gas exchange ability.

Next, a method for bundling and distributing the hollow fibers will be explained.

The hollow fiber membranes are fed at an angle that forms the surface of the focusing rod to form a cheese-like hollow fiber bundle on the focusing rod. Although one hollow fiber membrane may be supplied, a plurality of belt-shaped hollow fiber membranes may be supplied. In the case of multiple pieces, 2 to 10 pieces, preferably 4 pieces
~6 pieces are supplied in a strip. If the number exceeds 10, the band-like arrangement becomes disordered, which is not preferable. Also, the angle of twill is 10
A range of 0 to 170°, preferably 120 to 150° is suitable. When bundling and arranging yarn, usually 10~
Apply a tension of 200 g, preferably 50-150 g.

If the tension is too high, the hollow fiber bundle cannot move on the focusing rod, and even if it can move, there is a risk of damaging the hollow fiber membrane, which is not preferable. The tension applied to the hollow fiber membrane can be adjusted, and the filling rate of a specific portion of the hollow fiber bundle can be increased or decreased. The filling rate can also be partially changed by changing the angle at which the hollow fiber membranes are fed onto the focusing rod. That is, if the angle is made smaller, the filling rate becomes larger in that part, and if the angle is made larger, the filling factor becomes smaller. By appropriately combining these tensions, angles, and the shape of the focusing rod, the filling rate of the hollow fiber bundle can be controlled, and a hollow fiber bundle with an optimal configuration can be obtained. After bundling and arranging, the bundling rod is removed from the hollow fiber bundle. A cylindrical space is created at the center of the hollow fiber bundle, but if a focusing rod with a diameter that is relatively small compared to the diameter of the hollow fiber bundle is used, that space can be easily closed by a slight external force. Filled with hollow fiber membranes.

The diameter of the focusing rod is not particularly limited as long as it has enough strength to withstand the focusing operation. In order to change the filling rate depending on the portion of the hollow fiber bundle, a tapered focusing rod or a focusing rod with partially different diameters may be used. In addition, after focusing and distributing, it is necessary to transfer the hollow fiber bundle from the focusing rod into the housing. The surface of the rod is preferably coated with fluororesin or the like.

The material for the hollow fiber membrane used in the oxygenator of the present invention is preferably polypropylene, but other synthetic resins such as polyethylene, polytetrafluoroethylene, polysulfone, polyacrylonitrile, polyurethane, and silicone can also be used.

The hollow fiber membrane may be porous or nonporous. In the case of a porous hollow fiber membrane, the average pore diameter of the micropores in the peripheral wall is preferably about 0.01 to 1 μm.

Furthermore, the porosity should generally be about 20 to 80%.

Further, it is sufficient that the membrane area of the hollow fiber membrane filled in the housing is about 3 or less.

The present invention will be explained in more detail below with reference to Examples.

Example 1 A fluororesin was coated on the surface of a focusing rod having an outer diameter of 4 mm, and a hollow fiber membrane was focused thereon. After convergence, the hollow fiber bundle was moved on a converging rod and extracted, and at the same time, the hollow fiber bundle was housed in a housing to produce an oxygenator having the following dimensions and the configuration shown in FIG. 1. In addition, the tension at the time of convergence of the hollow fiber membrane was 100 g in the first half and 150 g in the second half.

Focusing rod: length 350mm outer diameter
4-surface fluororesin coating housing: outer diameter 640 length
200mm porous hollow fiber membrane: inner diameter approximately 300μm outer diameter
Approximately 400μm Average micropore diameter 0.22 Anal porosity 65-70% Material Polypropylene hollow fiber bundle: Length 280mm twill, angle 130° Filling rate 0.59 Blood filling volume 170cc Potting material Artificial with composition and specifications greater than polyurethane Performance tests were conducted using lungs and fresh blood. AAM I (Association for
Advance of Medical Instr.
Standard venous blood was prepared according to the guidelines for the blood test, and then introduced into the oxygenator.

Gas exchange capacity test blood flow rate if/min, 31/min and 5N
I followed / minute. Also, regarding pressure loss, the blood flow rate is 1.3.5! /min. Blood sampling and pressure measurements were performed near the blood inlet and blood outlet of the artificial lung. The collected blood is measured with a gas analyzer to obtain oxygen partial pressure, saturation, carbon dioxide partial pressure, carbon dioxide amount, PH, etc.
The amount of oxygen transfer and carbon dioxide transfer was determined by calculation.

Oxygen gas was supplied to the artificial lung with the ratio of blood flow rate to flow rate adjusted to 1:1.

The pressure drop, oxygen transfer and carbon dioxide transfer are respectively 30.90.14 for 7 minutes with blood flow 11.3.5
0 KakuHg, 60.190.310mj! /min and 60.
150.200++f! /minute.

As can be understood from these values, the oxygenator of the present invention has excellent gas exchange ability despite its low pressure loss.

〔Effect of the invention〕

The demolding oxygenator of the present invention has the entire internal space within the casing filled almost only with hollow fiber membranes, and due to the specific structure and configuration near the blood inflow part, it is small and the amount of blood filled is small. Despite this, it has low pressure loss and excellent gas exchange ability.

[Brief explanation of drawings]

FIG. 1 shows an example of the cross section of the hollow fiber membrane type oxygenator of the present invention. 1: Hollow fiber bundle 2: Casing 3.4: Partition wall made of potting material 5: Oxygen-containing gas inlet 6: Oxygen-containing gas outlet A, 8: Herad cap 9: Blood inlet 10: Blood outlet

Claims (3)

[Claims] (1) A hollow fiber bundle is housed in a casing, and the hollow fiber bundle is supported and fixed near both ends of the casing by potting material with both ends of the hollow fiber membrane open, and the hollow fiber bundle is supported and fixed in the interior space of the hollow fiber membrane. In an oxygenator in which oxygen-containing gas flows and blood flows through the space formed by the outer wall of the hollow fiber membrane and the inner wall of the casing, substantially the entire inner space of the casing is filled with hollow fiber bundles. A hollow fiber membrane oxygenator characterized by: (2) The hollow fiber membrane oxygenator according to claim 1, wherein the filling rate of the hollow fiber membranes has a sparse to dense distribution from the center of the hollow fiber bundle toward the inner wall of the casing. (3) The hollow fiber membrane type oxygenator according to claim (1), wherein the filling rate of the hollow fiber membranes has a distribution from sparse to dense in the fiber length direction of the hollow fiber bundle.