JPH0348812B2 - - Google Patents

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, methods for measuring pressure inside a living body include:
For example, as disclosed in Japanese Patent Application Laid-open No. 56-8033, it was common to measure biological pressure by guiding it to a pressure transducer outside the body using a catheter.
Therefore, the blood pressure waveform is distorted due to the compliance of the catheter, the viscosity of the blood, the inertia of the blood flow, etc., which hinders accurate measurement of cardiac function. In recent years, a pressure sensor with a small pressure transducer 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 at various parts of the living body without distortion, but there is still time. Many problems remained to be resolved, including the problem of zero drift, in which the zero point drifts over time, and antithrombotic properties during long-term monitoring.

[Purpose of the invention]

Therefore, the present inventors have developed various types of pressure sensors with a pressure transducing element at the tip, with the aim of obtaining a sensor for measuring in-vivo pressure that has excellent stability during measurement and has improved safety and antithrombotic properties. As a result of investigation, it was discovered that the cause of zero drift is the adhesive that adhered the diaphragm to the housing or pressure transducer element, and the swelling of the resin coated on the diaphragm due to moisture, leading to the completion of the present invention. It is something.

[Structure of the invention]

That is, the present invention has a pressure-receiving surface at the distal end, the side surface of the distal end, or in the middle of the catheter, and is composed of a diaphragm, a pressure transducing element, a housing, a catheter, etc., and an adhesive for bonding the diaphragm and the housing or pressure transducing element, and the vicinity thereof. The present invention relates to a sensor for measuring internal pressure in a living body, characterized in that the sensor is coated with a waterproof metal coat, the surface of the sensor is then coated with a resin, and the surface of the sensor is further coated with a metal.

Adhesives such as phenolic resin, epoxy resin, polyamide, and polyurethane are generally used to bond the diaphragm and the housing or the pressure transducer element, but these adhesives swell due to humidity and other factors, causing pressure-strain on the diaphragm. Characteristics may change. Therefore, in the present invention, a metal coating is applied to prevent the adhesive from swelling. However, the diaphragm of a pressure sensor is an important part of transmitting pressure, and applying more coating than necessary to this surface will increase compliance and distort the pressure waveform. Therefore,
Although it is preferable to limit this waterproof metal coat to the adhesive and its surrounding area, there is no problem in covering the entire pressure sensor except for the diaphragm. As for the type of metal, gold, silver, platinum, palladium, nickel, chromium, titanium, zinc, etc. can be used, and the thickness thereof is 0.005 μm to 0.3 μm.
A thickness of 0.03 .mu.m or more is preferable, but a thickness of 0.03 .mu.m or more is more desirable in order to reduce the probability of pinholes occurring. However, if it is less than 0.1 μm,
Even if metal is deposited on the diaphragm, it will not distort the waveform.

Further, in order to protect the diaphragm and to allow the catheter to be inserted into the body without damaging the body by the same operation as a normal catheter, it is preferable to further coat the waterproof metal coat with a resin. This plastic coat layer needs to have a thickness that does not distort the pressure waveform and does not damage the diaphragm or the living body during catheter operation, and preferably has a thickness in the range of 10 to 1000 μm. Since the diaphragm is also coated, a resin with low water absorption is desirable, and for example, polyvinyl chloride, polyvinylidene chloride, silicone resin, polyamide, polystyrene, polypropylene, polyester, etc. can be used. Further, since stainless steel is preferable as the material for the diaphragm and the housing, a primer may be required to strengthen the adhesive force of the plastic coating layer. As this primer,
Adhesives such as phenolic resin, epoxy resin, polyamide, polyurethane, etc. are preferable.

However, the aforementioned plastic coating resin
It is not necessarily good in terms of antithrombotic properties, and since it is a resin, it inevitably has some degree of water absorption. Therefore, by further coating this with a metal, water absorption can be reduced and antithrombotic properties can be increased. As for the type of metal, the same ones as the above-mentioned waterproof metal coat can be used, but gold, platinum, palladium, or silver are preferable in consideration of toxicity to living organisms and antithrombotic properties, and palladium and platinum are preferable in consideration of strength. Most desirable. The thickness of this metal thin film is preferably in the range of 0.005 .mu.m to 0.5 .mu.m, but for the purpose of preventing water permeability, a thickness of 0.03 .mu.m or more is more desirable. Furthermore, if the metal thin film is thin, the antithrombotic properties will be poor due to the influence of the underlying layer. Therefore, from the standpoint of antithrombotic properties, the thickness
It is desirable that the thickness be 0.05 μm or more. Furthermore, in terms of adhesion strength, it is better to be as thin as possible; if the thickness is 0.5 μm or more, there is a risk of peeling off when the catheter is bent or the like.

〔Effect of the invention〕

As described above, the present invention suppresses swelling and obtains high stability, safety, and antithrombotic properties by coating the surfaces of the plastic coat and adhesive of a sensor for measuring in-vivo pressure with a metal thin film. It is extremely useful medically.

〔Example〕

Next, the pressure sensor according to the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a schematic diagram of a pressure sensor according to an embodiment of the present invention.

Metal thin film 13 and plastic coat layer 12
When pressure is transmitted to the diaphragm 1 through the diaphragm 1, the connecting rod 10 connected thereto transmits the pressure to the metal plate 9,
Causes distortion proportional to pressure. Four piezo elements 2, 3, 4, and 5 are bonded to the top and bottom of the metal plate 9, forming a bridge circuit as shown in FIG. 2. When pressure is applied, the piezo elements 2 and 3 on the metal plate 9 expand, and the piezo elements 4 and 5 on the opposite side contract, so the resistance value of each piezo element changes, and the resistance value in the bridge is proportional to the resistance change. A current flows. This output current is passed through the catheter to an amplifier system and the pressure is measured. One piezo element may be provided at each of the upper and lower ends of the metal plate 9, and in this case, for example, 2 and 4 in FIG. 2 are fixed resistors. Of course, the present invention can also be applied to a type of pressure sensor in which a pressure transducer is directly bonded to a diaphragm.

The waterproof metal coat 8 covers the diaphragm 1 and the housing 1.
The adhesive 6 that adhered 1 and 1 swells due to humidity, etc.
While preventing changes in the pressure-strain characteristics of the diaphragm 1, the housing 11 and the catheter body 1
This is to prevent moisture from entering from the joint with the diaphragm 1. In this example, the area near the center of the diaphragm 1 is masked and palladium is coated with a thickness of 500 mm.
Deposited twice. For the waterproof coat 7, thiokol rubber was used in this example. Although this is not essential in the present invention, it functions to waterproof the cushion between the housing 11 and the waterproof metal coat 8 or the joint between the housing 11 and the catheter body 14, and in addition to thiocol rubber, phenol Adhesives such as resins, epoxy resins, polyamides, polyurethanes, etc. can also be used. In this embodiment, in order to improve the sensitivity of the sensor, the waterproof coat 7 and the waterproof metal coat 8 are not applied over the center of the diaphragm 1.

Furthermore, the diaphragm 1 was also coated with polyvinylidene chloride of 200 μm as a plastic coat 12. However, the antithrombotic properties of polyvinylidene chloride were found to be on the same level as polyvinyl chloride in experiments using the Imai method, making it unsuitable for long-term implantation in the body. . Palladium was vapor-deposited twice at 500° to ensure there were no pinholes.

Blood pressure was actually measured using the pressure sensor produced as described above. Using an adult mongrel dog weighing 10 to 15 kg, the head of the carotid artery and jugular vein is ligated.
The sensor was inserted toward the heart from the side of each blood vessel, and placed so that the pressure-receiving part of the sensor was located at the aortic root and central vein, respectively. 1 day after detention
Arterial pressure waveforms and right atrial pressure waveforms were measured on the 3rd and 5th days, but there was no slowing of the waveforms, which was thought to be due to thrombus, and the blood pressures showed reasonable values. Also, detention 5
The autopsy findings on the same day revealed a slight thrombus in the catheter area, but no thrombi at all in the pressure-sensitive part, and good results were obtained regarding antithrombotic properties, and the reliability of the measured values was maintained. It was drooping.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a pressure sensor according to an embodiment of the present invention, and FIG. 2 is a bridge circuit diagram thereof. In the figure, 1 is a diaphragm, 2, 3, 4, 5 are piezo elements, 6 is an adhesive, 7 is a waterproof coat, 8 is a waterproof metal coat, 9 is a metal plate, 10 is a connecting rod, 11
12 is a plastic coat layer, 13 is a metal thin film, and 14 is a catheter body.

Claims (1)

[Claims] 1. It has a pressure receiving surface at the tip, the side of the tip, or in the middle of the catheter, and consists of a diaphragm, a pressure conversion element, a housing, a catheter, etc., and an adhesive that adheres the diaphragm and the housing or pressure conversion element, and a waterproof metal coating in the vicinity. Then, the surface of the sensor is coated with resin,
A sensor for measuring internal pressure in a living body that is further coated with metal.