JPS6274327A - Sensor for measuring pressure in living body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pressure sensor that measures pressure at any location within a living body, such as blood pressure, intracranial pressure, and intrauterine pressure.

[Prior art]

Conventionally, as a method for measuring pressure inside a living body, it has been common to measure the pressure inside a living body by guiding the living body pressure through a catheter to a pressure transducer outside the body, as disclosed in Japanese Patent Application Laid-Open No. 56-8033. there were.

Therefore, catheter compliance, blood viscosity,
Blood pressure waveforms were distorted due to inertia of blood flow, which hindered accurate pressure measurement.

In recent years, a pressure sensor in which a small pressure transducer element is provided at the tip of a catheter has been developed, as disclosed in Japanese Patent Application Laid-Open No. 53-38196, and it has become possible to directly measure the pressure inside a living body without distortion. However, this sensor still had many problems that needed to be resolved, such as zero drift, where the zero point fluctuates over time, and antithrombotic properties during long-term monitoring.

The sensor for measuring internal pressure in a living body according to the present invention also belongs to this type, and an example of its internal structure will be explained with reference to FIG. The pressure transmission mechanism of the pressure sensor is such that the pressure receiving surface, ie, the diaphragm, which is fixed to the housing with adhesive ■, is displaced in response to changes in external pressure, and this is a pressure transducer fixed within the housing via the connecting body. The signal is transmitted to element (2), where it is converted into an electrical signal and a measured value is obtained. Piezoresistance elements are often used as pressure transducing elements, and stainless steel is usually used as the material for the housing and diaphragm. As mentioned earlier, the problem with this type of pressure sensor is that it tends to have zero drift, or the zero point changes over time. This tendency is particularly remarkable in water or in a high-humidity atmosphere, and for this reason, the problem of zero drift in blood and body fluids in living organisms has become a fatal flaw in measuring delicate internal pressures in living organisms. .

[Purpose of the invention]

The purpose of the present invention is to solve the problems of pressure sensors that have a pressure transducer at the tip of a catheter. The present invention aims to provide a sensor for measuring in-vivo pressure with improved thrombogenicity.

[Structure of the invention]

The inventors of the present invention first investigated the cause of the zero drift and found that the cause was swelling due to water absorption of the adhesive used to fix the diaphragm. Adhesives traditionally used are
Mainly phenolic resin, epoxy resin, polyamide resin,
These include polyester resin, polyurethane resin, silicone resin, etc. All of these have excellent adhesive properties, but also have water absorbing properties, and at the same time, they have the property of swelling as they absorb water. Although the degree of this swelling is very small, it is considered to have an extremely large effect on the zero drift of the pressure sensor, which is the object of the present invention. Based on this knowledge, the present inventors investigated various metal layers as materials that prevent water penetration, and as a result, it was found that certain metal layers have good waterproof and antithrombotic properties. The present invention was discovered through further intensive research.

That is, the present invention provides a pressure sensor that is located at the distal end and/or intermediate portion of a catheter and is composed of a pressure-receiving surface, a pressure transducer, and a housing, and the present invention provides a pressure sensor that is located at the tip and/or intermediate portion of a catheter and includes a pressure-receiving surface, a pressure transducing element, and a housing. This is a sensor for measuring internal pressure in a living body, characterized in that it is provided with a layer of tantalum and /''t! or tantalum pentoxide.

The tantalum and/or tantalum pentoxide layer can be formed by vacuum evaporation or sputtering, but sputtering is preferably used in view of the effects of radiant heat and adhesion strength. The thickness of the layer is not particularly limited, but from 200 people
In the range of 1μ, it is effective in improving the targeted waterproof function and antithrombotic properties. If the thickness is less than 200 Å, the film is in an intermediate state between an island-like structure and a continuous film, so it is likely to have pinholes, making it difficult to obtain a complete waterproof effect. On the other hand, if the thickness is 1 μm or more, the adhesion strength of the layer decreases due to internal stress, increasing the risk of cracks or layer peeling. Therefore, from the standpoint of safety, the layer thickness should be 500 mm.
A range of 5,000 to 5,000 people is more desirable.

Further, it is also possible to provide an intermediate layer made of a different metal layer or a resin layer between the pressure sensor main body and the outermost layer of tantalum and/or tantalum pentoxide, if necessary.

That is, in order to further increase the adhesion strength of the outermost tantalum and/or tantalum pentoxide layer, gold, gold,
Gold IAt such as silver, platinum, radium, titanium, chromium, etc.
Coating with oxide of bamboo shoots is also effective, and alloys of the metals 281 or more mentioned above may be used, or multilayer coating may be used. In this case, vacuum deposition or sputtering is mainly used as a coating method.

In addition, for the same purpose, polyvinyl chloride, polyvinylidene chloride, vinylidene ifluoride, silicone resin,
It is also possible to provide a resin layer of polyamide, polyester, polyurethane, polybutadiene, polystyrene, etc. as an intermediate layer. In this case as well, a blend of two or more of the resins mentioned above may be used, or a multilayer coating may be used.

A dipping method is mainly used as a resin coating method.

It is also effective to use a combination of a resin coating and a metal coating as the intermediate layer, that is, to stack one or more resin layers and one or more metal layers to form a multilayer coating.

〔Effect of the invention〕

As described above, in the sensor for measuring internal pressure of the present invention, by providing a layer of tantalum and/or tantalum pentoxide on the outermost layer surface, it is possible to suppress water penetration to an extremely low level. As a result, in-vivo pressure measurements have become extremely stable, and in particular zero drift has become negligible compared to conventional methods. Furthermore,
Both tantalum and tantalum pentoxide have excellent antithrombotic properties and are extremely chemically stable, so they are sufficiently safe for this purpose, which requires long-term insertion into the living body. It is extremely useful medically.

The present invention will be further explained with reference to Examples below.

[Example 1] Epoxy resin was applied to the adhesive surface (3) in FIG. 1 to fix the diaphragm. The thickness of the adhesive layer at this time is approximately 20μ
Met. Next, add tantalum to the tin xx
It was coated with a thickness of ooA. A high frequency sputtering method was used for sputtering.

The obtained pressure sensor was immersed in hot water at 37° C., and the measured value at atmospheric pressure, that is, the change in the zero point over time was measured. As a result, as shown in FIG. 2, the fluctuation of the zero point was stable at less than ±5 wHg over 24 hours.

Next, using an adult mongrel dog weighing 10 to 15 days, the carotid artery and jugular vein were ligated cranially, and a pressure sensor was inserted from the side of each blood vessel toward the heart, so that the pressure receiving part of the sensor was located at the origin of the aorta and the jugular vein, respectively. It was placed in the central vein. Arterial pressure waveforms and right atrial pressure waveforms were measured on the 1st, 3rd, and 5th days after placement, and there was no slowing of the waveforms, which was thought to be due to thrombus, and the blood pressure showed reasonable values. In addition, autopsy findings on the 5th day after indwelling showed that although a slight thrombus was observed in the catheter section, no thrombus was found in the pressure-sensitive area, and good results were obtained regarding antithrombotic properties. Reliability was also maintained.

Hereinafter, unless otherwise specified, the production of the pressure sensor and the evaluation of performance will be performed in the same manner as in Example 1.

[Example 2] Tantalum pentoxide was sputter coated to a thickness of 12,001 mm. Figure 3 shows the fluctuation of the zero point of the obtained pressure sensor in 37°C hot water. In addition, good results were obtained in animal experiments, with almost no blood clots observed.

[Comparative Example 1.2] The pressure sensors prepared in Examples 1 and 2 were subjected to zero drift measurement without being coated with tantalum and tantalum pentoxide by double-sided coating. As shown in FIGS. 4 and 5, the results showed large fluctuations in time. Furthermore, in animal experiments, the arterial pressure waveform slowed from the beginning to the third day after placement, and became more pronounced with time thereafter, and thrombus was observed throughout the pressure-sensitive area in the wound findings on the 5th day after placement.

[Example 3.4] Polyurethane was used as the adhesive (2) in FIG.

The thickness of the adhesive layer was approximately 30μ. A tantalum layer was provided on the surface (Example 3), and a vinyl chloride layer was provided between the pressure sensor and the mental layer by dipping (Example 4). The thickness of each layer and the evaluation results were as shown in Table 1, and all results were good.

[Comparative Example 3.4] Example 3.4 was carried out in the same manner, but the surface was not coated with tantalum. The layer thickness and evaluation results are as shown in Table 1, and the zero drift was large and the antithrombotic properties were insufficient.

[Example 5] The same procedure as Example 3 was carried out, but the thickness of the tantalum layer was 5mm.
I gave it an A. The evaluation results were good as shown in Table 1.

[Comparative Example 5] In Example 5, the thickness of the tantalum layer was set to 200. The evaluation results are shown in Table 1, and no thrombus formation was observed, but the fluctuation of the zero point was somewhat large.

Chapter 1 Table

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the internal structure of a pressure sensor used in the present invention. FIGS. 2 and 3 are graphs showing changes in zero point pressure over time in Example 1.2, respectively, and FIGS. 4 and 5 are graphs showing changes in zero point pressure in Comparative Example 1.2, respectively.

Claims (1)

[Claims] A pressure sensor located at the distal end and/or intermediate portion of a catheter and consisting of a pressure receiving surface, a pressure transducing element, and a casing, characterized in that a layer of tantalum and/or tantalum pentoxide is provided on the outermost surface of the pressure sensor. A sensor for measuring internal pressure in a living body.