JP2001299704A - Method and instrument for measuring physical variable in organism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide system which is provided with an easily manufacturable and operable guide wire and used for examination of a physiological variable in an organism in a blood vessel. SOLUTION: The guide wire 10 used for measuring the physiological variable in the organism has a sensor 14 for forming the output signal characteristic of the value of the variable by monitoring a physical variable. The sensor 14 is connected to the first potential of an electronic unit through an electric wire 11 extended along the wire 10. An intracorporeal electrode 17 is connected to the sensor 14 and comes into contact with a humor around the sensor 14. When the guide wire 10 is inserted into the blood vessel, electric power is supplied to the sensor 14 through a part of the body of the organism due to the second potential of the electronic unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guide wire assembly for an intravascular examination.

[0002]

2. Description of the Related Art It is known that a sensor is mounted on a guide wire, and the sensor is disposed in a blood vessel in a living body via the guide wire to detect a physical parameter such as pressure or temperature. Sensors include elements that are directly or indirectly sensitive to parameters. For example, the temperature can be measured by observing the resistance of a conductor having a temperature-sensitive resistance, or by observing the length of an element having a known temperature-related elongation.

[0003] In order to monitor the state of the sensor in the body, some kind of communication means is required. In some cases,
Means for supplying power to the sensors and / or communication means are also needed. Thus, to power the sensor and communicate with the sensor, a plurality of cables that transmit the measurement signals are connected to the sensor, and the cables are connected to the guidewire to exit the vessel through the connector assembly to the external monitoring unit. Guided along. Further, the guidewire is typically provided with a central metal wire (core) that functions as a support for the sensor and a conductor for ground potential.

However, when using a large number of cables,
It is necessary to at least partially replace the core wire with a tubular section containing the cable. This section forms a fragile portion of the guidewire and presents risks such as bending and asymmetric movement during manipulation within the blood vessel.
Also, conventional guidewire assemblies present a problem in that they require very difficult manual assembly procedures. Extremely small components must be assembled under a microscope, which is tedious, tedious and labor intensive.

An improved guidewire addressing this problem is described in European Patent Application No. 0925803, which forms the basis of the preamble of the independent claims of the present application. European Patent Application No. 0925803 describes a guidewire which allows a generally tubular conductor to be coaxially arranged about a core wire, thereby simplifying the manufacturing process. However, the manufacture of such guidewires is still relatively time consuming, expensive, and requires complex connectors. Also, there remains a need for a guidewire that is easy to operate with a sensor.

[0006]

Accordingly, there is a continuing need for a wire communication system that is easy to operate, inexpensive, and easy to use, so there is still a need for a simplified guidewire assembly with physical property sensors. ing.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system for intravascular examination of physiological variables in a living body with a guidewire that is easy to manufacture and operate. This object is achieved with a system according to claim 1 and a guidewire according to claim 7.

According to the present invention, the number of electrical conductors of a guidewire provided with sensors for measuring physiological variables in a living body can be reduced, thereby providing a guidewire which is easy to manufacture and use. Is done. A method for measuring physiological variables using a guidewire and a system according to the invention is also provided according to claim 11.

[0009] Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. However, the detailed description and specific examples are given by way of illustration only, showing preferred embodiments of the present invention. From this detailed description, various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art. The present invention will become more fully understood from the detailed description, including the accompanying drawings, which are given by way of illustration only and not limitation.

DETAILED DESCRIPTION OF THE INVENTION First, a guidewire according to the present invention will be described. Generally, according to the present invention, a sensor that requires electrical energy for operation is connected to the far end of an insulated wire. In addition, the body electrode is directly connected to the sensor, or is connected to the sensor via an electronic circuit connected to the sensor. The body electrode is arranged to be in contact with a living tissue such as blood when inserted into the body. That is, the body electrode includes a portion for directly contacting body tissue when inserted into a patient.

In use, with the proximal end of the wire connected to a power source, the sensor is inserted into the body, and the sensor and body electrodes are placed at sites within the body where measurements are taken. Therefore, the in-vivo electrode is placed in contact with the living body, specifically, with bodily tissue such as blood, and obtains electrical connection with the bodily tissue. To obtain a closed electrical circuit, a second electrode is connected to a power source and carried near the body electrode. The second electrode comprises a portion that is physically and electrically connected to the patient, either directly or via a conductive enhancement medium, as is well known in the art.

In one embodiment of the invention, this is done by placing the electrode on the patient's skin outside the measurement site, similar to the application of an ECG electrode. In this embodiment, the electrical circuit is closed through the patient's internal tissue and skin. In another embodiment of the present invention,
The distal end of the second electrode is placed near the measurement site and the electrical circuit is closed by also inserting the second electrode so as to contact the patient's body tissue. In this embodiment, the electrical circuit is closed internally through the patient's tissue, typically blood.

[0013] The sensors as well as the electrodes can be inserted at any suitable site in the body via a hollow tube, such as a suitable cannula or introducer. In a preferred embodiment, the sensor, additional electronics, internal electrodes, wires and a second electrode are mounted on a guidewire structure,
Typically, it is inserted through the femoral artery.

In a most preferred embodiment, the electric wire is integrated with the core of the guide wire. By using the core wire as the electric wire, an advantage of reducing the number of components can be obtained. This is because guide wires typically have such a metal core extending axially along the guide wire to provide the guide wire with appropriate stiffness. Thus, while the use of a guidewire having a core wire as an electrical wire is described herein for the sake of simplicity, the methods for communicating with the sensors described herein run along the guidewire or guide the wire. Obviously, it may be implemented using a separate wire separated from the wire.

The power supply used in the present invention is an electronic unit installed outside the patient's body. The electrical unit is capable of providing an appropriate current through an electrical circuit that partially includes the patient's body, as described below. further,
As described later, the electronic unit is preferably provided with an electronic circuit for interpreting and presenting an output signal from the sensor circuit.

Next, one embodiment of the guide wire of the present invention will be described with reference to FIG. FIG. 1 shows a cross section of the distal end of a guidewire 10 according to the present invention. A core wire 11, typically of stainless steel or a superelastic alloy such as Nitinol®, extends through the central axis of the guidewire. The core wire 11 is made of Parylene (registered trademark), silicon, Teflon (registered trademark), polyimide,
It is coated with an insulating layer 12, which is a polymer such as polyurethane or a ceramic coating.

The proximal coil section 13A and the distal coil section 13B cover the distal end of the core. Proximal coil section 13A functions to provide a smooth surface and adequate stiffness at the end of the guidewire, and is typically made of stainless steel. Distal coil section 13
B is similar to the proximal section except that it also provides X-ray opacity, and is typically manufactured from platinum. The coils work in combination to provide a uniform outer diameter for the guide and facilitate the introduction of the guidewire into the artery. When inserted into an artery, the coil can penetrate the blood surrounding the end of the guidewire. The distal end of the guidewire is closed with a soldered arc-shaped distal end 16.

The purpose of describing the configuration of the coil section is to show the shape of the distal end of a typical guidewire currently in use. However, the coil section is not required per se for the practice of this specification, but can be utilized as part of one embodiment of the present invention, as described below.

The sensor 14 is attached to the core wire and is electrically connected to the core wire via a connection point 15. The sensor comprises, in addition to components sensitive to the physical properties to be determined, any electronic circuits required to function properly and usefully as a sensor, as well as circuits for superimposing the sensor output signal on the carrier voltage signal . Circuits for such superimposition are known per se to those skilled in the art and include devices such as voltage / frequency converters, analog / digital converters, pulse width modulators and delta modulators.

FIG. 11 shows an example of an embodiment of a sensor having a related circuit. Here, the rectifier 501,
The sensor element 502 and the relaxation oscillator 503 are shown connected in series. The input of the rectifier 501 is the connection point 504
To the core wire of the guide wire. The output of relaxation oscillator 503 is connected to a body electrode via node 505. Further, the rectifier 501 and the sensor element 502 are connected to the body electrode. Relaxation oscillator 503 generates a square wave, as opposed to a sine wave oscillator. That is, the output signal is
Transition from minimum level (digital "zero") to maximum level (digital "1"). The oscillating period or pulse width of such an oscillator, also known in the literature as an "astable multivibrator", typically has one or several characteristic time constants R
It can be controlled by a resistance-capacitance circuit characterized by C (where R is a resistance value and C is a capacitance value).
Therefore, the period of the oscillator, that is, the pulse width can be controlled using the resistance sensor or the capacitance sensor.

Referring again to FIG. 1, the output signal from the sensor 14 is transmitted to the surrounding blood via the signal output electrode 17. The signal output electrode 17 is at least partially not insulated, is connected at one end to the sensor 14 to transmit output from the sensor circuit, and has the other end connected to the periphery between any of the coil sections 13A, 13B. Extend to the blood. Since the core is insulated, the electrode 17 is not affected by the potential of the core.

FIG. 2 shows an alternative embodiment 117 of the signal output electrode, wherein components different from those of FIG. 1 are numbered. According to FIG. 2, the signal output electrode 117 is connected to or forms part of one coil section 113B. At least a portion of the selected section should not be insulated while one of the coil sections is useful so that contact with surrounding bodily fluids is possible. With this alternative embodiment, a simple design is obtained that guarantees proper contact with the surrounding parts of the body.

The use of a guidewire 10 according to the present invention, such as the guidewire shown in FIG. 1, is schematically illustrated in FIG. The guidewire 10 is inserted into the femoral artery of the patient 25. Guide wire 10, sensor 14 and signal output electrode 1 in the body
The position of 7 is indicated by a dotted line.

An external electrode 21, similar to an ECG electrode, is attached to the skin of a patient 25 near the location of the sensor circuit 14. The external electrode 21 is connected to the electronic unit 2 via an electric wire 24.
2 is connected. The guidewire 10, and more particularly its core 11, is connected to a cable 26 connected to the core using any suitable connector means (not shown), such as an alligator type connector or any other known connector. Through,
Connected to electronic unit 22.

The electronic unit 22 provides voltage to the circuit including the wires 26, the core 11 of the guidewire 10, the sensor circuit 14, the signal output electrodes 17, the blood or other tissue 23 of the patient, the electrodes 21 and the cables 24.

In use, the sensor 14 is inserted into the patient, for example, as described above with reference to FIG. 3, and the electrode 21 is connected to the signal output electrode 1 via, for example, the patient's skin, as described above.
7 is provided approximately above. Those skilled in the art will know how to introduce a guidewire, as well as the methods necessary to properly conduct the electrodes provided on the patient's skin. The core wire 11 and the electrode 21 are an electronic unit 22
Connected to.

The current generated through the patient's tissue upon application of a voltage must be sufficiently low to be safely transmitted through the human body. International Standard IEC601-1 (199
8), it is preferable to select acceptable values according to Chapter 19. It is possible to use a weak DC voltage,
It is preferred to use an AC voltage to obtain a useful high current through the body, for example an AC voltage having a frequency higher than 1 kHz, allowing tolerating up to 10 mA without jeopardizing the health of the patient .

In a very simple embodiment, corresponding to the above description, and as shown schematically in FIG. 4, when measuring the temperature in the body, the sensor determines the known relationship between temperature and resistance. The temperature-sensitive resistor 214 has one end connected to the core wire 211 (corresponding to the connection point 15 in FIG. 1) and the other end connected to the signal output electrode 217. The sensor is inserted into the body, as indicated diagrammatically by dotted line 223. Electronic unit 232 outside the body
Are the cable 26, the core wire 211, the signal output electrode 217,
A voltage is provided to sensor 217 via body tissue 233 and electrodes 221 disposed on the skin of body 233.

The voltage provided by the electronic unit 232 is A
It may be a C voltage or a DC voltage. Electronic unit 232 also includes means for recording the overall resistance of the circuit through the body. Such means are well known and will not be described herein. By measuring the total resistance and knowing the temperature-resistance relationship of the sensor, the temperature at the sensor can be easily calculated.

The main advantage of this embodiment is simplicity. However, it has the disadvantage of low accuracy and reliability. These disadvantages are the result of effects from other resistances in the monitoring circuit, for example, the coupling impedance of skin electrode 221. In general, when applying an AC voltage, the sensor is typically connected to a circuit that includes a rectifier that converts the AC voltage to a DC voltage to drive the sensor selected as being sensitive to the physical parameter being tested. One example used in such applications and useful for measuring cardiovascular pressure is Transducers '87 (The 4th international confere
H. Chau and KD Wise, “An ultraminiaturatur for cardiovascular catheters” (p. 344).
e solid-state pressure sensor for a cardiovascular
catherter) ".

As mentioned above, the output signal of the sensor is processed by a circuit connected to the sensor such that information representing the level of the monitored physical parameter is superimposed on the signal provided by the electronic unit. . The electronic unit includes a circuit that calculates the value of the inspected parameter based on the superimposed signal. One embodiment of such an electronic unit 332 is shown in FIG. 5, where a guide wire assembly is used to provide an electrical signal through a patient's tissue 326 with a core 321 and a sensor unit. 3
03 and an internal electrode 317.
The guidewire assembly is introduced to the patient (indicated by dashed line 325). The electronic unit 332 is connected to the core wire 321 via the cable 26 and outside the body via the tissue and the second cable 24.

The electronic unit 332 typically has 100
A drive oscillator 310 is provided that provides an AC voltage in the range of 2-10 V at a frequency in the range of kHz-1 MHz.
The drive oscillator 310 is connected to a drive amplifier 301 that drives a first transformer 302, which is connected to the circuit non-DC through the body to provide a supply voltage. A second transformer 304, which is connected to the circuit through the body in a non-DC manner, is used for detecting a superimposed signal. The signal is amplified by the amplifier 305 and the narrow band filter 3
06 to remove low frequency and high frequency interference. Bandpass filter 306 can be, for example, a so-called phase sensitive amplifier or synchronous amplifier.

Schmitt trigger (or comparator) 3
07 is connected to the output of bandpass filter 306 and triggers at the selected voltage threshold level (digital “1”)
Out). Digital microprocessor 308
Correlates the trigger pulse with the clock pulse generator 309 and counts the number of clock pulses between successive trigger pulses.

FIGS. 6A to 6E are interconnected with respect to the time axis and show the decoding operation of the measurement signal provided by the sensor unit 303 in the set-up according to FIG. The sensor unit 303 is a unit including an oscillator, and corresponds to the sensor circuit described above with reference to FIG.

FIG. 6A shows an oscillator output signal from the sensor unit 303. The measurement conditions, ie, the measured variables, determine the pulse widths T1, T2. FIG. 6B shows the power consumption of the sensor unit 303. Power consumption is essentially constant, with a peak superimposed in time with the transition of the sensor oscillator from "0" to "1" or vice versa.

FIG. 6C shows an output signal from the Schmitt trigger 307. The trigger threshold is shown as a horizontal dotted line in FIG. 6B. FIG. 6D shows a clock pulse from clock pulse generator 309 calculated by microprocessor 308 to determine time interval T1.

FIG. 6E shows a clock pulse from clock pulse generator 309 calculated by microprocessor 308 to determine time interval T2. Thus, by determining the time intervals encoded by the sensors and corresponding circuitry, information about the measured physiological variable can be obtained via electrical signals passing through body tissue.

FIG. 9 shows one embodiment of the present invention including an acoustic sensor. As shown with the previous embodiment, the guide wire 410 includes the core wire 401 covered with the insulating layer 402. The distal end of the guidewire has a rounded tip 404 and a coil 403 acting as a signal output electrode according to the present invention, similar to that described above. A piezoelectric ceramic plate 407 such as a PZT (zirconate titanate) plate is provided on the core wire and the signal output electrode 4.
03 is connected. Micro mechanical acoustic resonator 406
Is attached to the piezoelectric ceramic plate 407. The resonator should be chosen such that the resonance frequency depends on the physiological change to be measured. An example of a useful micro-mechanical acoustic resonator is the “Polysilicon Resonant Beam Transducer and Its Manufacturing Method (PoPo) given to H. Guckel et al.
lysilicon resonating beam transducers and methods
of producing the same) in U.S. Patent No. 5,188,983.

As described above, the piezoelectric ceramic plate 40
7 responds with mechanical vibration transferred to resonator 406 when energized by an alternating voltage provided through body tissue. As shown in FIG. 10, at the resonance frequency f1 or f2 (corresponding to series resonance or parallel resonance), the peak point and the valley bottom point respectively appear in the electrical impedance.
The electrical impedance is detected by an external electronic unit, which corresponds to the unit described above with reference to FIG. 5, so that the physiological variable sought can be calculated.

Thus, in a guidewire assembly and communication system according to the present invention for determining a physical parameter within a patient's body, a guidewire provided on a guidewire is provided.
The wires can be used to transfer information about physiological variables detected by sensors in the body. This is obtained, according to the invention, by using the tissue of the patient, such as blood and skin, which acts as a conductor in cooperation with the guidewire according to the invention.

A guidewire assembly according to the present invention is very simply manufactured using a small number of components. The sensor circuit is easily connected to the exposed section of the core at the distal end of the guidewire using any suitable conventional method, such as soldering, with the associated body electrodes. The core wire can be connected to the electronic unit using any suitable connector means without the need for additional cables. Further, as shown in the above embodiment, the present invention, since there is no conductor other than the core wire, during the period of arranging the guide wire in the blood vessel, to enable good operability,
Enables sensor guidewire designs that provide adequate flexibility and symmetry.

Another embodiment of the present invention, called the double line embodiment, is shown in the schematic diagram of FIG. According to FIG. 7, the guidewire 210 is similar to the guidewire 10 of FIG. 1, for example, in that it comprises an insulated core 11, but additionally comprises an insulated second conductor 31. . At the distal portion, near the distal end of the guidewire, the insulation is removed from the second conductor 31 to expose the conductor and form the electrode 32.

As shown in FIG. 8, when inserted into the patient's body 25, the core wire 11 of the guide wire 210 is connected to the electronic unit 22 similar to the electronic unit 22 of the first embodiment.
2 is connected. The second conductor 31 is also an electronic unit 222
Connected to. At the same time, the insulated second conductor electrode 3
2 is inserted into the body together with the guide wire and comes into contact with the body fluid of the patient. In use, the core 11, sensor (and any additional electronics) 14, signal output electrode 17, conductor 31, electrode 32, connecting leads 24, 26 and electronic unit 222.
Is closed via the body tissue 23, ie, the blood of the patient.

Thus, as described for the previous embodiment, the electrical circuit includes the body tissue of the patient. However, in the double wire embodiment, no electricity is transmitted through the patient's skin and no electrodes are provided on the patient's skin. Instead, the electric signal that has exited the signal output electrode 17 propagates through the surrounding blood to the second electric wire 31.

Therefore, when using the double wire embodiment, it is not necessary to provide electrodes on the patient's skin. this is,
Obtained at the expense of more complex and difficult operation of the guidewire.

According to the second embodiment, it is necessary to connect the guide wire using two connectors, but any of these connectors can be any suitable one such as a simple and low-cost alligator type connector. Connector.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of the distal end of a guidewire according to the present invention.

FIG. 2 is a cross-sectional view of the distal end of a guidewire according to another embodiment of the present invention.

FIG. 3 is a schematic diagram showing a system according to the invention being used on a patient.

FIG. 4 is a schematic diagram of a simple embodiment of the present invention.

FIG. 5 is a block diagram of one embodiment of an electronic unit used in conjunction with the present invention.

6A to 6E are interconnected time charts illustrating the decoding operation of a measurement signal provided by a sensor unit configured in accordance with the present invention.

FIG. 7 is a diagram of a double wire embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating the embodiment of FIG. 7 being used on a patient.

FIG. 9 shows one embodiment of the invention with an acoustic sensor.

FIG. 10 is a chart of impedance versus frequency for one embodiment with an acoustic sensor.

FIG. 11 is a block diagram showing one embodiment of a sensor and related circuits.

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Leif Smith Sweden-756 45 Uppsala, Marma Skogsweig 11

Claims (13)

[Claims] 1. A power supply electronic unit (22, 222,
332), an electric wire (11) having a distal end for insertion into a living body and a proximal end for electrical connection to the electronic unit (22, 222, 332), and is connected to the proximal end of the electric wire (11). CLAIMS 1. A system for measuring a physiological variable in a living body in a blood vessel, comprising: a sensor (14, 502, 406), wherein a body electrode (17; 117) connected to the sensor (14, 502, 406). , 113B; 317; 405), which, when placed at the measurement site, have a portion for making physical and electrical contact with body tissue, and to the electronic unit (22, 222, 332). Second electrode (21, 24; 221; 32) for electrical connection of
A second electrode having a portion for making electrical contact with the second portion of the living body, and transmitting an electrical signal through the body tissue and the electrode. And the system. 2. The system according to claim 1, wherein the body insertion wire is a core extending through a guide wire. 3. The electric unit (22, 222, 33).
The system of claim 1 or 2, wherein 2) includes AC power to power the sensor (14) with an AC voltage through the body tissue. 4. The system of claim 3, wherein said AC voltage is in a range of 2-10 V and a frequency is in a range of 100 kHz-1 MHz. 5. The electronic unit (22, 222, 33)
3. The system according to claim 1, wherein 2) includes a DC power supply. 6. The method according to claim 1, wherein the second electrode is a second electric wire having an electrode portion at a distal end for insertion into the body. System. 7. An electric wire (11) extending along a guide wire (210) and a sensor (14, 50) connected to the electric wire (11) at a distal end of the guide wire (210).
A guide wire (210) for measuring a physiological variable in a living body in a blood vessel, comprising: a body electrode (17; 117, 113B; 317; 405).
Are connected to the sensors (14, 502, 406) and the body electrodes (17; 117, 113B; 317; 405)
Has a portion for making physical and electrical contact with body tissue when placed at a measurement site. 8. The guidewire according to claim 7, wherein the electric wire (11) is a core extending through the guidewire (210). 9. The guidewire according to claim 7, wherein a coil (113B) arranged around a distal end of the guidewire (210) is connected to the sensor and functions as the body electrode. 10. A second electric wire (31) extending along said guide wire (210) is attached, said second electric wire (31) being close to the body tissue near the distal end of said guide wire (31). Guidewire according to claim 7 or 9, characterized in that it has an electrode part (32) for making physical and electrical contact with it. 11. A guidewire with a sensor (14, 502, 406) responsive to a physiological variable at a far end is inserted into the body and said sensor (14, 502, 40).
6) is placed at the measurement site and the sensors (14, 50)
2, 406) are electric wires (1) having a proximal end outside the body.
10. A method for measuring a physiological variable in a living body in a blood vessel, connected to 1), comprising: selecting a guidewire according to any one of claims 7 to 9; Electrically connecting a second electrode to the body; said wire (11) and said second electrode (21, 24; 2).
21) is connected to an electrical unit (22, 222) and the sensors (14, 502, 4) are passed through the patient's body tissue.
06) powering the sensor (14, 502, 406) via the electrode
Recording a signal representative of said physiological variable from. 12. The method of claim 11, wherein connecting the second electrode comprises placing the electrode on the patient's skin. 13. The method of claim 11, wherein connecting the second electrode comprises placing the electrode along the sensor (14, 502, 406) in the patient's body.