JPH0475664A - Model artificial lung - Google Patents

Abstract

PURPOSE:To obviate the generation of the drift of blood and an excessive increase in pressure drop with the model artificial lung which passes blood to the outer side of hollow yarn by consisting a hollow yarn bundle of a bundle formed by disposing the hollow yarn in twill winding and a bundle formed by disposing the hollow yarn in substantially the same direction as the longitudinal direction of an inside cylinder and outside cylinder. CONSTITUTION:The blood is introduced from a blood inlet part 5, flows in a blood introducing part 6 to the hollow yarn bundles, flows in the hollow yarn bundle 3 consisting of the twill winding part and the hollow yarn bundle 4 consisting of the straight disposed yarn part and is discharged from a blood outlet part 7 provided at the end on the side opposite from the side of the outside cylinder 1 where the blood is introduced. On the other hand, the gas is introduced from a gas inlet part 8, flows in the hollow yarn bundles and is discharged from a gas outlet part 9 provided at the other end. The gas diffusible hollow yarn is previously disposed in the cylinder larger in diameter by several mm than the inside cylinder. The hollow yarn is first disposed at a twill angle, i.e., 125 deg. angle with the axial direction of the cylinder on the front surface of the cylinder until the thickness about half the thickness of the entire hollow yarn bundle is attained. Then, the yarn is disposed around this bundle in the direction same as the direction of the axis of the cylinder. The aggregated hollow yarn bundle is then disposed in the space between the inside cylinder and the outside cylinder and both ends are fixed by a potting material. The drift of the blood is prevented in this way and the pressure drop is suppressed to a lower level.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a membrane oxygenator that performs gas exchange of blood using gas-permeable hollow fibers during extracorporeal blood circulation, and particularly relates to a method for arranging the fibers. It is something.

[Conventional technology]

An artificial lung is used as a means of blood gas exchange during the surgical procedure. Artificial lungs can be roughly divided into bubble-type and de-type. Bubble oxygenators inject gas into the blood, and because the blood and gas come into direct contact, problems have been pointed out, such as damage to blood cells, ie, hemolysis. On the other hand, the membrane oxygenator performs blood gas exchange through a gas-permeable membrane, so it is a more physiological method than the bubble oxygenator, and is widely used clinically. Gas-permeable hollow fibers are mainly used in this membrane oxygenator, and there are two types: an internal perfusion system in which blood flows inside the hollow fibers, and an external perfusion system in which blood flows outside the hollow fibers.

In the internal perfusion method, blood flows inside hollow fibers with an inner diameter of several hundred microns, which increases pressure loss.
It is likely to cause damage to blood cells, ie hemolysis. In addition, since blood flows in a laminar flow, it is difficult to oxygenate blood other than blood flowing near the membrane surface, and a large membrane area is required to improve gas exchange ability, resulting in a reduction in blood filling volume. That is, there are also drawbacks such as an increase in the amount of extracorporeally circulating blood.

[Problem to be solved H] In the external perfusion system, blood flows outside the hollow fibers. Therefore, the disadvantages of the above-mentioned internal perfusion system are eliminated. However, when an external perfusion method is adopted, blood can freely flow through the spaces between each hollow fiber, so if there is a flow path with even the slightest resistance, the blood will flow biased toward that part (
(so-called channeling), the gas exchange ability of the oxygenator is significantly reduced. Therefore, for the purpose of preventing blood drift, products in which hollow fibers are wound in a twill pattern, knitted hollow fibers, and the like have been developed. There are also products in which the threads are arranged in a straight line, but great care is required to arrange the threads evenly. Blood flow becomes complicated when hollow fibers are twisted or twisted. This increases the resistance to blood flow and causes considerable pressure loss. - On the other hand, there is a limit to the uniformity of the yarns with linear yarns, so in order to improve gas exchange ability, it is necessary to increase the membrane area, which inevitably increases the amount of extracorporeal blood circulation. It also increases, which is not desirable.

[Means to solve the problem]

In the membrane oxygenator of the present invention, we focused on the fact that when blood flows into the space between each hollow fiber, uneven flow occurs due to the non-uniformity of the flow path. The fiber bundle prevents drifting flow7, and the outer periphery of the hollow fiber bundle is arranged in a straight line to prevent an increase in pressure loss. - A structure consisting of at least two layers of hollow fiber bundles. The problem was solved by doing this.

In the membrane oxygenator of the present invention, blood is uniformly introduced into the flow path between each hollow fiber in the circumferential direction from the blood inflow portion, first flows into the twilled portion, and then flows unevenly into the flow path between each hollow fiber. It will flow in a uniformly dispersed manner without causing any turbulence. Here, twilling means arranging the yarn at an angle to the longitudinal direction of the inner cylinder or outer cylinder.

The angle is not particularly limited, but in practice it is 6
It may be within a range of about 0 to 150 degrees. In the membrane oxygenator of the present invention, 90 to 140°, particularly 100° or more and 130°
It is preferable that the range is less than The blood flow that has been uniformly dispersed in the twill portion flows directly into the linear thread portion and flows to the outlet of the oxygenator with low pressure loss. Here, the term "linear yarn arrangement" refers not only to yarns arranged parallel to the longitudinal direction of the inner cylinder or outer cylinder, but also includes yarns wound in a cheese pattern at an acute angle to that direction. It is something that Further, although the ratio of the thickness of the hollow fiber bundle between the twill portion and the linear yarn distribution portion is not particularly limited, it is preferable that the thickness of the hollow fiber bundle in the linear yarn distribution portion is relatively thick.

Furthermore, in the membrane oxygenator of the present invention, the hollow fibers may be wound directly onto the surface of the inner cylinder, or after being wound around the surface of a cylinder having an outer diameter larger than the outer diameter of the inner cylinder, the hollow fiber bundle may be wound from the cylinder. Pull out,
The obtained hollow fiber bundle may be arranged between the inner and outer cylinders.If the bundle is wound directly on the surface of the inner cylinder, if the winding density is too high, the cross-sectional area of the blood flow path at the blood inflow part will suddenly increase. This is not preferable because the pressure loss increases due to the decrease in . Such a situation can be prevented by providing a gap between the inner cylinder surface and the hollow prefecture east inner surface.

[Effect]

Since the membrane oxygenator of the present invention includes a hollow fiber bundle in which gas-permeable hollow fibers are cross-wound and a hollow fiber bundle in which the fibers are arranged in a straight line, there is no uneven flow of blood, and It also does not cause an excessive increase in pressure loss. In addition, by providing a gap between the outer surface of the inner cylinder and the innermost surface of the hollow fiber bundle, a sudden decrease in the cross-sectional area of the blood flow path at the inlet portion where blood is introduced into the hollow fiber bundle is prevented. In addition, it is possible to prevent an excessive increase in pressure loss, and furthermore, it is possible to uniformly circulate blood in the circumferential direction of the hollow fiber bundle.

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

(Example) FIG. 1 shows an example of a cross section of the membrane oxygenator of the present invention.

The membrane oxygenator of the present invention consists of a cylindrical outer cylinder 1, an inner cylinder 2 whose lower end is closed, a hollow fiber bundle 3 consisting of a twilled part disposed in the gap, and a linear yarn part. It is composed of a hollow fiber bundle 4 and a potting part 10.10 degrees fixed at both ends of the hollow fiber bundle with the hollow fibers open.

Blood is introduced from the blood inlet section 5, passes through the blood introduction section 6 into the hollow fiber bundle, flows through the hollow fiber bundle 3 consisting of a twilled section, then through the hollow fiber bundle 4 consisting of a straight yarn section, and flows through the outer tube. Blood is discharged from the blood outlet section 7 provided at the end opposite to the side into which the blood of No. 1 is introduced.

On the other hand, gas is introduced from the gas inlet 8, flows inside the hollow fiber, and is discharged from the gas outlet 9 provided at the other end.

The gas-permeable hollow fibers are arranged in advance in a cylinder whose diameter is several orders of magnitude larger than the inner cylinder. First, the fibers are arranged on the cylinder surface at a winding angle (angle with respect to the axial direction of the cylinder) of 125° to a thickness of about half of the total hollow fiber bundle, and then around the hollow fibers are arranged in the same direction as the axial direction of the cylinder. Thread. Thereafter, this bundle of hollow fibers is placed in the gap between the inner tube and the outer tube, and both ends are fixed with potting material. Channeling is prevented by the twill portion near the inner cylinder. The filling rate of hollow fibers in the twill portion (the ratio of the area where hollow fibers exist to the total cross-sectional area) is 0°4 to 0.7
The degree, particularly, is preferably about 0.55 to 0.6, and in this example, it is about 0.6. Further, the filling rate of the linear yarn distribution portion is also not particularly limited, but in the case of this example, it is 0.6 as in the twill portion.

The gas permeable hollow fiber is not particularly limited as long as it is gas permeable and has excellent biocompatibility, and examples include polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene, polysulfone, and silicone rubber. Porous or homogeneous hollow fibers made of, for example, can be used. In this example, porous polypropylene hollow fibers are used.

The main specifications of this embodiment are shown below.

Inner diameter of hollow fiber 320μ Outer diameter of hollow fiber 400μ Outer diameter of twill portion
42mm Outer diameter of linear thread part 5
8mm Hollow fiber filling rate 0.6Twill angle 125゜Gap between hollow fiber bundle inner diameter and inner cylinder outer diameter Approximately 2 mm effective length
180 Effective membrane area: 1.7 or less The following is an experiment in which gas exchange ability was evaluated using the membrane oxygenator of the present invention and its results.

(Experiment example) The experiment was conducted using fresh blood. For fresh blood, standard venous blood with the properties shown below is prepared in an oxygenator for adjustment, and this standard venous blood is perfused into the test oxygenator, blood is collected from the inlet and outlet of the oxygenator, and the blood is placed in a blood gas analyzer. Items such as pH 1 oxygen gas partial pressure and carbon dioxide gas partial pressure were measured at pH 1, and the amount of oxygen and carbon dioxide gas transferred was derived.

Standard venous blood properties Oxygen saturation 65±5% Hemoglobin amount 12±Ig/di Carbon dioxide partial pressure 45±5mmHg Blood temperature 3
7±2℃ BE (Pace Effects) 0±5 meq/i.

Oxygen gas was flowed into the artificial lung such that the flow rate ratio of blood to gas was 1=1. The experimental results are shown below.

(Results) The oxygen transfer amount and carbon dioxide transfer amount in the artificial lung of the present invention calculated from the results of blood gas analysis are as follows: Blood flow II 12
/min time respectively 65 m1/min and 50 m1/min, blood flow rate 3
f/min time 195 m1/min and 140 m1/min respectively, blood flow rate 5 f/min time 3201 I+1/min and 240 m1 respectively
/minute. Also, the pressure loss is the blood flow rate 1.3.51/
The minutes were 2o, 7o, and 130o+mHg, respectively.

〔Effect of the invention〕

The membrane type oxygenator of the present invention can prevent the uneven flow of blood, which has been a problem with external perfusion type oxygenators, and can also keep pressure loss low. Although it is small, it has excellent gas exchange ability, and the amount of extracorporeal blood circulation is small, so it can be applied to children. It is also possible to use a pulsatile flow pump, and the amount of blood transfused can be minimal, significantly reducing the burden on the patient.

[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: Cylindrical outer tube 2: Inner tube with a closed lower end 3: Hollow fiber bundle consisting of a twill portion 4: Hollow fiber bundle consisting of a straight yarn portion 5: Blood inlet portion 6: To the hollow fiber bundle Blood introduction part 7: Blood outlet part 8: Gas inlet part 9: Gas outlet part 10.10゛: Botting part

Claims (2)

[Claims] (1) The space formed by the inner cylinder and the outer cylinder is filled with gas-permeable hollow fibers to form a hollow fiber bundle, oxygen-containing gas is circulated in the hollow part of the hollow fibers, and blood flows outside the hollow fibers. In a membrane-type oxygenator that flows through a membrane oxygenator, the hollow fiber bundle is formed by arranging hollow fibers in a twill manner, and the hollow fibers are arranged in substantially the same longitudinal direction as the longitudinal direction of the inner cylinder and the outer cylinder. A membrane oxygenator characterized by comprising a bundle formed by arranging threads into a membrane. (2) The membrane oxygenator according to claim (1), wherein a gap exists between the outer surface of the inner cylinder and the innermost surface of the hollow fiber bundle.