WO2008145329A1

WO2008145329A1 - Device and method for detecting a pressure-dependent parameter

Info

Publication number: WO2008145329A1
Application number: PCT/EP2008/004182
Authority: WO
Inventors: Anton Grabmaier; Thomas Van Den Boom; Uta Dahmen; Olaf Dirsch; Gudrun Stockmanns; Reinhard Viga; Daniel Balzani; Dominik Brands
Original assignee: Fraunhofer Gesellschaft Zur Förderung Der Angewandten Forschung E. V.; Universität Duisburg-Essen
Priority date: 2007-05-31
Filing date: 2008-05-26
Publication date: 2008-12-04
Also published as: DE102007038402A1

Abstract

The invention relates to a device for detecting a pressure-dependent parameter for a line wall structure (18) of a medium-conducting line, comprising a sensor element (10) that is embedded in the line wall structure (18), separated from the medium (19) conducted in the line, and a transmission device (14). The sensor element (10) is designed to detect the pressure-dependent parameters and the transmission device (14) wirelessly supplies the pressure-dependent parameter that has been detected by the sensor element (10). The transmission device (14) is coupled to the sensor element (10).

Description

Device and method for detecting a pressure-dependent parameter

description

The present invention relates to an apparatus and method for detecting a pressure-dependent parameter, and more particularly to a method for locally determining pressure and pressure gradients in embedded, flexible, small-diameter, fluid-carrying conduits.

In medical applications, there is a need for a blood pressure measurement in blood vessels, which can be carried out continuously over longer periods of time and in which a corresponding pressure sensor is separated from the blood - that has no contact with the blood. Current measurement methods used in clinical routine are either invasive (by direct contact with the blood), pressure sensor-based or non-invasive using pressure cuffs.

In an invasive blood pressure measurement, a tube-bound pressure measuring system (catheter) is hydrostatically coupled to the arterial vascular system via an arterial approach. Thus, in this method, a wall penetration takes place and a line is embedded, for example, in a blood vessel in a body - a so-called catheter endometer. Thus, no direct wired access to the vessel is possible and the embedding material does not forward the pressure-dependent size. There is no access to the measurement area. Furthermore, the puncture site in the skin is a permanent and clinically relevant source of infection. Hose and cable systems between the transducer and the pressure transducer affect the patient and may cause injury, for example, by "getting stuck." The patient is mobilizing significantly reduced with the help of nursing staff and in his later independent mobility. Measuring errors caused by a dislocation of the pressure catheter make the method moreover susceptible to interference.

In the non-invasive blood pressure measurement, blood pressure parameters (systolic and diastolic blood pressure) are typically determined indirectly by means of an inflatable pressure cuff with a manometer placed around the upper arm. This is a standard method in medicine for extraluminal (non-vascular-invasive) blood pressure measurement and is also known as the Riva-Rocci method, and thus constitutes an indirect method of measuring blood pressure. It is disadvantageous in that it has a low accuracy, an integral value Provides large time ranges and no permanent measurement (long-term measurement) time-resolved allows. Mobile device embodiments of the method in a long-term monitoring also have the serious disadvantage that the inflation of the cuff is perceived as annoying, especially during resting phases. Furthermore, the method is susceptible to interference, for example as a result of a slipped-over arm sleeve, and the measurement is intermittent, so that it does not permit continuous pressure value detection.

In addition to the systems currently in practical clinical use, there are also systems based on an implantable into a vascular system pressure measuring capsules. In this method, the vessel wall is penetrated by the system during the implantation, which in turn entails the risk of thrombus formation and thus makes further complicated measures required.

Based on this prior art, the present invention has the object to provide a device and a method for pressure measurement by means of a sensor element in a medium, wherein the sensor element is separated from the medium and thus the pressure measurement is easy to handle and low in risk.

This object is achieved by a device according to claim 1, a monitoring system according to claim 12 and a method according to claim 18 or claim 22.

The present invention is based on the finding that the pressure in a medium can be determined by a pressure-dependent parameter of a conduit wall structure surrounding the medium when a sensor element is embedded in the conduit wall structure. The pressure-dependent parameter is detected by the sensor element and provided wirelessly by a transmission device. The pressure-dependent parameter may be, for example, a mechanical stress of the line structure or determined and wirelessly retrieved by means of an RFID (RFID = Radio Frequency Identification) technology (more details below).

Embodiments of the present invention relate to medical applications and in particular to a blood pressure measurement in a vessel or blood vessel having a vessel wall (conduit wall structure), wherein the sensor element is designed as a pressure measuring implant and is applied in a vessel wall. The pressure measuring implant detects pressure-sensor-based mechanical stress in the vessel wall, or a change in wall properties of the pipe or the vessel. The wall tension is functionally related to the blood pressure prevailing in the vessel. Namely, when the blood pressure within the vessel increases, he also exerts an increased pressure on the vessel wall, which then forms an increased mechanical stress. If the functional relationship between the vascular tension and the prevailing blood pressure is known, the blood pressure can be determined from the acquired measured variable (vascular tension) and then transmitted wirelessly. The transmission can be RFID-based, for example happen. There are various possibilities for this, which will be discussed in more detail below. One possibility is to utilize an inductive coupling of the transmission device to an extracorporeal receiving station (eg on the belt of a patient).

RFID technology is currently used in particular in the areas of automatic identification of goods, persons, goods and animals. The RFID technology is a radio-based, contactless identification method, which originally used radio frequencies in the radio frequency range (100 kH to some 10 MHz), but now also frequencies up to the microwave range are used. The RFID systems are advantageous in that they have high transmission capacities, are insensitive to environmental influences and soiling, and provide the possibility of reading out many transponders simultaneously in the case of a long range. Thus, this technology allows, for example, to carry out a blood pressure measurement at different points of the body or a vessel in parallel.

In RFID technology, a transponder is the actual label, which carries information and communicates with a stationary or mobile reader or a transceiver or generally communication device. Depending on the system configuration, this communication allows the transponder to be read and written, which gives the system additional flexibility. A subsequent change of stored data is thus easily possible. A particular advantage of RFID systems is the ability to use passive transponders that do not require their own power supply and therefore can be built compactly. This option makes RFID technology particularly attractive for medical applications. Before the medical applications are described, the RFID technology will be discussed in more detail. An RFID system typically has at least one reader or communication device and one or more transponders. Both the reader and the transponder each have an antenna that significantly affects a range of communication between the reader and transponder. If the transponder is in the vicinity of the antenna of the reader, both can exchange data (transponder and reader). The reader also transmits energy to the transponder in addition to the data. Inside the transponder there is an antenna coil for this purpose, which can be designed, for example, as a frame or ferrite antenna. To operate the transponder, the reader first generates a high-frequency alternating magnetic field by means of its antenna. The antenna also includes a multi-turn coil. Thus, the field of the reader generates an induction voltage in the coil of the transponder. This induction voltage is rectified and is ready to power the transponder. In parallel with an inductance of the transponder coil, a capacitance is generally connected, so that a parallel resonant circuit is formed. The resonant frequency of this resonant circuit corresponds to the transmission frequency of the RFID system. At the same time, the antenna coil of the reader is brought into resonance by an additional capacitor in series or parallel connection. From the, in the transponder induced AC voltage additionally a clock frequency is derived, which is a memory chip or a microprocessor of the transponder as a system clock available.

In the simplest case, the data transmission from the reading device to the transponder is effected by a so-called amplitude sampling, in which the high-frequency alternating magnetic field is switched on and off. The reverse data transfer from the transponder to the reader uses the characteristic of the transformer coupling between the reader antenna and the transponder antenna. In this case, the reader antenna is a primary coil and the transponder antenna is a secondary coil of a transformer formed by reader antenna and transponder antenna. This transfor- mation coupling between the primary coil and the secondary coil can now be exploited to transmit information from the transponder (for example by changing its inductance) to the primary coil of the reader.

The RFID technology is thus ideally suited for interrogating a measured value (for example blood pressure or a pressure-dependent parameter) from an implant with a sensor element or regularly (wirelessly) detecting it and optionally transmitting it regularly to a communication device.

Thus, in embodiments of the present invention, the pressure in conduits is measured without penetrating a conduit wall (medically extraluminal). This is possible by measuring a pressure-dependent parameter of the conduit wall, which can be, for example, a wall tension or another wall property and can be measured by a pressure sensor applied to the wall {medically: intraluminally). Information of the measured quantity (for example of the pressure) can be modulated onto a transport medium that penetrates the embedding medium of the conduit (the human body, for example). For example, an RFID-based system with an inductive transmission of measured variables can be used for this purpose. Outside the embedding medium, the measured quantity is derived from the transport medium and scaled to a print size. This can be, for example, by an inductive derivative of the measured variable impressed by laser modulation. This allows an intelligent transfer in a pressure reading.

Thus, embodiments of the present invention comprise a sensor element which is inserted into a conduit wall is embedded structure and is separated from the guided in the conduit medium and detects a pressure-dependent parameter. Furthermore, a transmission device for the wireless provision of the pressure-dependent parameter detected in the sensor element is coupled to the sensor element. In further embodiments, the sensor element detects a mechanical pressure, a mechanical stress or an expansion in the conduit wall structure as a pressure-dependent parameter. Furthermore, it is possible to detect a temperature (for example by means of a temperature sensor) and thus to detect or detect and interrogate fever or fever courses. The transmission device can have, for example, a transponder for transmitting the pressure-dependent parameter, wherein the transponder can either be read out inductively or is specifically queried by an interrogation signal, so that the transponder transmits the pressure-dependent parameter in a response signal.

In further exemplary embodiments, the transmission device has a transmission device, wherein the transmission device transmits the pressure-dependent parameter. Furthermore, a device according to the invention can have an energy storage medium, wherein the energy storage medium provides an energy supply to the sensor element and / or the transmission device. The energy storage medium may have, for example, a battery or a rechargeable battery.

Embodiments of the present invention are particularly applicable to conduit wall structures that include a flexible material and are embedded in a surrounding material. The conduit wall structure may further comprise a layer structure having a plurality of layers, wherein the pressure dependent parameter in different layers may have different dependencies of pressure so that measurements in different layers may be made. The flexible medium can be Ways a blood vessel in an organism, wherein the sensor element is implanted in the wall structure of the blood vessel.

Embodiments of the present invention further comprise a monitoring system for a medium-carrying line having a conduit wall structure, wherein the monitoring system comprises a device according to the invention for detecting a pressure-dependent parameter and further comprises a communication device which is designed to provide the information provided by the transmission device of the device according to the invention receive pressure-dependent parameters. In further embodiments, the communication device has a transmission unit for transmitting an interrogation signal, and the interrogation signal can be detected and answered by a transponder, the response signal having the pressure-dependent parameter. The communication device can also transmit the interrogation signal at prescribed time intervals (fixed or variable) so that the pressure-dependent parameter can be transmitted by the transponder at the predetermined time intervals. Thus, a continuous detection of the pressure, for example, in a blood vessel is possible and can thus be used for long-term studies (for example, blood pressure readings over several days).

The pressure-dependent parameter is in a certain relationship to the pressure, wherein the particular relationship, for example, depends on the material of the sidewall structure and can be determined experimentally. The parameters also include individual measured values recorded by the sensor or a series of measured values or also already prepared measured values. The specific relationship can be exploited by an evaluation unit in order to determine the pressure therefrom. The evaluation unit can furthermore be assigned to or arranged in a transponder or a communication device. Thus, for example, has a sensor system as components to be implanted a pressure sensor, an evaluation and an RFID telemetry unit (one of the RFID systems described above) with receiving coil on. As external components, for example, a reading station (reading device) with Meßwertekonstruktions-, evaluation and recording unit may be present.

Embodiments of the present invention also include a method of detecting a pressure dependent parameter in a conduit wall structure of a conduit carrying a medium, the method comprising disposing a sensor element in the conduit wall structure, and the sensor element being disposed separate from the medium pressure-dependent parameter and provision of the pressure-dependent parameter for a wireless transmission. The inventive method may further comprise arranging a sensor element in the wall structure of a blood vessel of an organism, and the pressure-dependent parameter may be transmitted in response to an interrogation signal.

Thus, embodiments of the present invention have a number of advantages. Significant therapeutic advances include the use of a blood pressure measurement system that eliminates the risk of catheter infection, blood pressure cuff (dislocation risk), and tubing (immobility, risk of injury). This allows, for example, differentiated radiovascular therapies to be performed outside of the expensive intensive care unit under "normal conditions" and longer term, in particular the need for a blood pressure transducer connected to a portable monitoring device, which can be attached to a patient's belt, for example This is because a once-implanted system, unlike external measurement methods such as the automatically-actuated blood pressure cuff, does not make a noticeable difference in quality of life and mobility the long-term use is not affected. On the other hand, the risk of thrombus formation is reduced, so that there is no reason for preventive administration of drugs and their prevention, and thus additional procedures and the effort for the patient can be avoided. Thus, the present invention provides a method and apparatus for a sensor system that allows for non-vasospasm (extraluminal) detection of instantaneous blood pressure even in long-term mobile use, and thus allows long-term measurement of cardiovascular parameters - such as blood pressure measurement for intermittent detection and / or spontaneous hypertension.

With correspondingly high sampling of the pressure values (or voltage values), which is fundamentally possible with the method according to the invention, it is also possible, for example, to image a pulse curve, since each pulse beat is accompanied by increased vascular tension (blood pressure). Thus conclusions about cardiac arrhythmias, for example about the training state and about the cardiac rhythm, are possible via the heart rate conclusions. On the other hand, not only the quality of hypertension but also of hypotension can be deduced from the pressure course. Likewise, it is possible to determine the elastic modulus of the blood vessel during scans of the pressure values / voltage values, for example in the millisecond range. This makes it possible to draw conclusions about the extent of vasoconstriction (vascular constriction) and wall changes.

Embodiments of the present invention will be explained below with reference to the accompanying drawings. Show it:

Fig. Ia, b are two schematic sectional views of a

Apparatus of an embodiment of the present invention; FIG. 2 shows a schematic illustration of a pressure measuring system according to an embodiment; FIG. and

3 is a detailed cross-sectional view of a pressure measuring system.

With regard to the following description, it should be noted that in the different embodiments, identical or equivalent functional elements have the same reference numerals and thus the description of these functional elements in the various embodiments shown below are interchangeable.

Fig. Ia and Ib show cross-sectional views of a medium-carrying line. 1 a shows a cross-sectional view perpendicular to a flow direction of the medium 19 in the line, and FIG. 1 b shows a cross-sectional view with a sectional plane in the direction of flow of the medium in the line.

1 a shows the medium-carrying line with a line wall structure 18, in which a sensor element 10 is implanted and a transmission device 14 is arranged on the line wall structure 18. The sensor element 10 is connected to the transmission device 14 (connection is not shown in this cross-sectional view).

FIG. 1b shows a further cross-sectional view, wherein the cross-sectional plane is perpendicular to the cross-sectional plane of FIG. 1a. This cross-sectional view in turn shows the medium-carrying line with the conduit wall structure 18 and a medium 19 within the conduit wall structure 18. In the conduit wall structure 18, the sensor element 10 is implanted, which is connected to the transmission device 14, wherein the transmission means 14 on a surface of the conduit wall structure 18 is arranged. In this case, the sensor element 10 is separated from the medium 19 within the conduit wall structure 18 and, if the conduit wall structure 18 consists of a layer sequence, can be implanted in one or more of the layers of the layer sequence.

The sensor element 10 is designed to detect a mechanical stress in the conduit wall structure 18, wherein the mechanical stress in the conduit wall structure

18 is a consequence of the pressure of the medium 19 within the conduit. The mechanical stress can alternatively be detected by stretching the conduit wall structure 18. For this example, the sensor element 10 may have a voltage or strain-dependent capacitance or resistance element that allows electrical detection of the mechanical stress. Furthermore, the transmission unit may include a transponder having a coil and an antenna, and the coil and antenna may be disposed on an outer wall of the line structure 18, for example.

2 shows a schematic illustration of a monitoring system 30. The monitoring system 30 has a communication device 1, a sensor device 10, which is located in a side wall structure 18 of a line which is a medium

19 performs, implanted, and further a transmission device 14 which is arranged on the conduit wall structure 18. As described in FIG. 1, a pressure measurement of the medium 19 within the conduit wall structure 18 takes place, for example, by means of a measurement of a mechanical tension of the conduit wall structure 18 by the sensor belt 10. The sensor element 10 is coupled to the transmission device 14, which controls the pressure-dependent parameter exemplary stress of the conduit wall structure 18 - provides. The transmission of the pressure-dependent parameter from the transmission device 14 to the communication device 1 can take place, for example, by means of a wireless transmission, wherein an electromagnetic signal can be taken as the propagation medium. There are various possibilities for this. On the one hand, the transmission of the pressure-dependent parameter can take place by means of an inductive coupling in which, for example, a coil of the transmission device 14 is inductively coupled to a coil in the communication device 1 and in which the inductance of the coil in the transmission device 14 can be changed in accordance with the pressure-dependent parameter is. The inductive coupling of the coil in the transmission device 14 to the coil in the communication device 1 now causes that in the communication device 1, the pressure-dependent parameter can be detected.

A further possibility consists in that the transmission device 14 has a transponder, so that upon interrogation of the communication device 1, the transponder transmits a signal, wherein the signal can contain the pressure-dependent parameter. In this exemplary embodiment, the interrogation signal of the communication device 1 can be taken simultaneously to the current or voltage supply of the transmission device 14 as well as to an electrical detection of the pressure-dependent parameter in the sensor element 10.

Another possibility is that the transmission device 14 has a power supply and an active transmitter, so that the pressure-dependent parameter can be transmitted in the presence of an interrogation pulse or interrogation signal from the transmission device 14 or independently of it, for example, at predetermined intervals / intervals, so that the communication device 1 only needs to have a receiving part which detects the pressure-dependent parameter. The power supply of the transmission device 14 may, for example, by means of done by a battery or by means of an energy generation, eg from the environment (as a result of temperature, movement, etc.).

Fig. 3 shows a detailed cross-sectional view with the same cross-sectional plane as in Fig. Ia, i. the cross section is executed perpendicular to a direction of movement of the medium 19.

The exemplary embodiment from FIG. 3 shows, on the one hand, remote "outer" system components (communication device 1) and "inner" system components 9 near the line. The remote "outer" system components 1 have a control unit 2 for all system components, a measurement signal demodulation / reception unit 3, a measuring signal propagation unit 4, an interface to the operating and display unit 5, an output unit 6 (for the pressure measurement values) and optionally or optionally a power supply unit 7. The line-related "inner" system components 9 have a sensor 10 or sensor element, or identical or different sensors, measuring electronics 11, central electronics 12, a transmission unit 13 and an energy storage / reception / generator unit 14. The "internal" system components 9 close to the line are embedded in the conduit wall (conduit wall structure) 18 and / or in a conduit embedding material 20.

The line wall 18 may, for example, have a layer sequence with a first layer 15 with a first material, a second layer 16 with a second material up to a last layer 17 with a last material. Thus, the conduit wall 18 has n layers, wherein the n layers can have materials with different or the same material parameters. The medium 19 includes a lumen of pressurized fluid, and the embedding material 20 may be, for example, biological material in which a blood vessel is embedded. The communication between the remote "outer" system component 1 and the "inner" system component 9 close to the line takes place, for example, by a transport medium 8 which is used for energy and / or measured variable transmission.

In other embodiments, the pressure dependent parameter may also be another physical parameter (e.g., a temperature), chemical (e.g., pH), or medical parameter (e.g., oxygen saturation in tissue or other cardiovascular parameter). The pressure can also be measured absolutely or relatively - for example as pressure changes as a function of time (at regular time intervals or continuously borrowed). Furthermore, the pressure may also be detected as a function of location, e.g. using multiple sensor elements. According to embodiments of the present invention, this is easy to realize because a communication device 1 can query several transponders simultaneously or one after the other. Thus, the blood pressure in different blood vessels can be detected or along a blood vessel. As before, the transponders can be operated passively or actively and, alternatively, the transmission device 14 can have a transmitter, so that information can be transmitted continuously or at intervals of time (without the need for an interrogation signal). The transmitter can be operated, for example, pulsed, so that a transmission at certain times (time intervals) takes place. By a combination of the location and time-dependent pressure, it is also possible to determine a flow velocity of the blood.

In further embodiments, a detection of the blood pressure is controlled by a threshold value, ie only when a threshold value (upper or lower) is violated is a transmission of a warning signal and as long as the pressure-dependent parameter within a tolerance range is, can be dispensed with the transmission of the pressure-dependent parameter.

Claims

claims

1. Device for detecting a pressure-dependent parameter of a line wall structure (18) of a medium-carrying line, having the following features:

a sensor element (10) for embedding in the conduit wall structure (18) separate from the medium (19) carried in the conduit and for detecting the pressure dependent parameter; and

a transmission device (14) for wirelessly providing the pressure-dependent parameters detected by the sensor element (10), wherein the transmission device (14) is coupled to the sensor element (10).

2. Device according to claim 1, wherein the sensor element (10) is designed to provide a mechanical

Pressure to detect a mechanical stress or strain in the conduit wall structure (18) as the pressure-dependent parameter.

3. Apparatus according to claim 1 or 2, wherein the transmission means (14) comprises a transponder for transmitting the pressure-dependent parameter.

4. The device according to claim 3, wherein the transponder is the inductively readable.

5. The device according to claim 3, wherein the transponder is configured to detect an interrogation signal and to transmit in response to the pressure-dependent parameter.

6. Apparatus according to claim 1 or 2, wherein the transmission device (14) as a transmitting device to convey the pressure-dependent parameter.

7. Device according to one of the preceding claims, further comprising an energy storage medium, wherein the energy storage medium provides a power supply of the sensor element (10) and / or the transmission device (14).

8. The device according to claim 7, wherein the energy storage medium comprises a battery.

9. Device according to one of the preceding claims, wherein the conduit wall structure (18) has a flexible material and is embedded in a surrounding material (20).

10. Device according to one of the preceding claims, wherein the conduit wall structure (18) has a layer structure with a plurality of layers (15, 16, 17), wherein the pressure-dependent parameter in different layers (15, 16, 17) have different dependencies from the pressure or pressure curve.

A device according to any one of the preceding claims, wherein the medium-carrying conduit is a blood vessel in an organism, and wherein the sensor element (10) is implantable in the wall structure (18) of the blood vessel.

12. monitoring system (30) for a medium-carrying line with a conduit wall structure (18), having the following features:

Device for detecting a pressure-dependent parameter according to one of the preceding claims, comprising a sensor element (10) for embedding in the conduit wall structure (18), separate from that in the conduit. medium (19) and for detecting a pressure-dependent parameter, and with a transmission device (14) for wirelessly providing the pressure-dependent parameters detected by the sensor element (10), wherein the transmission device (14) is coupled to the sensor element (10) ; and

a communication device (1) which is designed to receive the pressure-dependent parameter provided by the transmission device (14).

13. Monitoring system (30) according to claim 12, wherein the communication device (1) has a transmitting unit for transmitting an interrogation signal.

14. Monitoring system (30) according to claim 13, wherein the transmission device (14) has a transponder, wherein the transponder is designed to detect the interrogation signal and to transmit in response to the pressure-dependent parameter.

A monitoring system (30) according to claim 13 or 14, wherein the communication means (1) is arranged to transmit the interrogation signal at predetermined time intervals.

16. monitoring system (30) according to one of claims 12 to 14, further comprising an evaluation device, wherein the evaluation device is designed to determine from the pressure-dependent parameter, a pressure or pressure profile of the medium (19) in the medium-carrying line.

17. Monitoring system (30) according to claim 15, wherein the evaluation device is associated with the transponder or the communication device (1).

18. A method for detecting a pressure-dependent parameter in a conduit wall structure (18) of a medium-carrying line, comprising the following steps:

Disposing a sensor element (10) in the conduit wall structure (18) separate from a medium (19) carried in the conduit;

Detecting the pressure-dependent parameter; and

Provide the pressure-dependent parameter for a wireless transmission.

19. The method of claim 18, wherein in arranging the sensor element (10) in the wall structure (18) of a

Blood vessel is embedded in an organism.

20. The method of claim 18, wherein in providing the pressure-dependent parameter is transmitted in response to a query signal.

21. The method according to any one of claims 18 to 20, further comprising the following step:

Evaluation of the pressure-dependent parameter in order to determine a pressure or pressure profile of the medium (19) in the medium-conducting line.

22. A method for extraluminal monitoring of cardiovascular parameters of an organism, comprising

steps:

Embedding a sensor element (10) in the vessel wall structure (18) of a blood vessel in the organism;

Detecting a cardiovascular parameter; and Providing the cardiovascular parameter for wireless transmission.

23. The method of claim 22, further comprising the step of:

Transmitting the cardiovascular parameter to an external evaluation device.

24. The method of claim 23, further comprising the step of:

Evaluation of the cardiovascular parameter in the external evaluation device for blood pressure monitoring.