WO2010066208A1

WO2010066208A1 - A catheter for measurement of electrochemical properties of bodily fluids

Info

Publication number: WO2010066208A1
Application number: PCT/CZ2009/000142
Authority: WO
Inventors: Jitka HANZALOVÁ
Original assignee: Hanzalova Jitka
Priority date: 2008-12-08
Filing date: 2009-11-30
Publication date: 2010-06-17
Also published as: CZ2008792A3; CZ302036B6

Abstract

A catheter for measurement of electrochemical properties of bodily fluids, mostly for measurement of impedance and pH. A catheter for impedance measurement consists of at least two electrodes in a shape of a hollow cylinder, where at least its one part has an electrically conductive surface (9), which is connected by means of a secondary conductor (3) with a measurement device (6) that is isolated from the liquid system, of which impedance is measured. An electrically conductive surface (9) is deposited onto a nonconductive underlay (1) by a method where a metal is evaporated under a vacuum - sputtering, magnetron sputtering, radiofrequency sputtering, diode plasma sputtering, cathodic arc evaporation, ion plating, ionization-assisted evaporation, ion implantation or laser alloying. A catheter for impedance measurement can also consist from at least one pH electrode of the same shape as the reference electrode (5), whereas measurement device (6) is conductivity-meter and voltmeter. ˙

Description

A catheter for measurement of electrochemical properties of bodily fluids

Technical field The invention relates to catheters for measurement of electrochemical properties chiefly in bodily fluids. Namely it is measurement of impedance and /or pH mainly in bodily fluids. In the case of measurement of gastroaesophageal reflux disease, the combination of impedance and pH electrodes ensures findings of both, acidic and alkalic reflux. The pH electrodes register changes in the case of stomach acidic fluids intrusion into esophagus and impedance electrodes register alkalic, duodenal reflux. In the case of several measuring electrodes placed one above each other, it is possible to measure reflux elevation and it is possible to quantify reflux that way. Also velocity and fluency of bolus passage during the swallowing can be detected by the help of impedance electrodes.

Present technical conditions

The construction of impedance catheters for conductivity measurement in the esophagus is described for example in patent US5833625. The metal rings are mounted outside of the catheter. Then material of these metal rings is gold or stainless steel. Another patent describing combined catheter measuring impedance, hydrostatic pressure, and contact pressure is US2006116564. In this patent there are electrodes also seated outside a catheter. Secondary conductors in current catheters are wire-guided inside of one long catheter and brought out through small perforations in its side wall. Then the wire secondary conductor is manually circumvoluted around the catheter body to make about 5 coils. An epoxyglue with silver addition is dropped on these coils and the innate electrode ring is pulled on and forced on this connection. There are some disadvantages of this construction:

1 ) Possible damaging of secondary wire conductors and a contact limitation of an electrode with a secondary conductor. Secondary conductors are pulled through small catheter perforations by small hook manually and it often happen that two or more wires are pulled out instead of one. Spare secondary conductors are then pushed back, they often crank / break and then do not have contact . Also - there is no pressure from the catheter body against the electrodes, which are mounted outside of a catheter. (It would not be possible to slip an electrode on a catheter) and contact is assured only by glue. So all electrodes may not to have positive contact with a secondary conductor.

2) It is impossible to check functionality of a catheter during construction

As it is said above - two or more secondary conductors can be pulled out and than pushed back in catheter tubings. Their cranking can happen during the operation. Functionality of these mechanically manipulated secondary conductors is not clear and it is checked after completion of catheter construction .

Preparation of current catheters for impedance measurement in bodily fluids is laborious and requires experienced manufacturers.

In reality a glass pH electrode is used for esophageal application only in a limited way because it is difficult to handle and difficult to manufacture.

Generalities of commercially used devices for esophageal pH measurement in last 25 years use a system based on principle of oxidation reduction metal pH electrode, whose measuring part consists of pH sensitive metal and its oxide, mostly antimony. Although the structural design of measuring probes differs from manufacturer to manufacturer, its principle remains the same. The potential between pH sensitive metal (mostly antimony) and a reference electrode - placed either in the same catheter or separately on the body surface- is measured by means of an operational amplifier. The typical example of construction is an electrode consisting of an antimony cylinder. This is a piece of polycrystalline antimony of approximately 1mm diameter x 1mm thickness, which is either glued by conductive glue or soldered to a secondary conductor coming through a catheter. There are some disadvantages of this electrode including, laborious manufacturing and inaccuracy of measurement during the life of the sensor. Another known measured electrode consists of metal - a primary copper cylinder galvanically plated by antimony. The disadvantage of this electrode is difficult reproducibility during its manufacturing. An electrode consists of two conductive metals - copper as a base and an upper layer of antimony. During the contact with digestion fluids the antimony layer is slowly etched down to copper. This happens mostly by microscopic erosions developing around impurities or other irregularities on the surface of conductive layer. There is a mixture potential between exposed copper and surface antimony, which results in an uncontrollable and unpredictable change of resulting potential of electrodes even with constant pH of the measured solution. Measured and displayed pH value drifts - even in identical pH solutions. The electrode produces a lower slope and therefore shows smaller change of potential per pH unit.

Another sensing electrode is an electrode from Japanese authors JP 5023360, US 5573798, US 5480534, EP 0472398 and EP 0472396. A sensing electrode consists of electrically conductive material with a nonconductive film thereonto. A part of the nonconductive film is removed leaving a layer of pH sensitive film (a mixture of metal, primarily iridium and its oxide) deposited on the exposed surface. Indium and its oxide are in contact with electrically conductive material. In addition, the metal oxide layer could be covered by porous, nonconductive material to protect the oxide layer. Also iridium and its oxide are in some cases deposited directly on nonconductive base, sapphire or ceramics.

There is iridium oxide used in these patents as a pH sensitive layer. The price of iridium is approx. 55 times more expensive than the price of antimony. Sputtering of iridium is problematic because of its non-reactivity. Pure oxygen is blasted into the evacuated chamber under a controlled pressure to make a coat of metal and metal oxide at the same time and in a specified narrow ratio. A change in the ratio influences the performance of the electrode. A coat of porous, nonconductive material can make the access of the measured liquid to the electrode worse. It also worsens the out-washing of measured solution from porous material and slows down the H+ response. The fast time response is important for the esophageal application, because evaluation of the procedure is based on the time ratio when pH in the esophagus is over or below pH level of 4.

It is not suitable to use a ceramic nonconductive underlay for pH measurement in bodily fluids because of possible chipping of the underlay which is a health hazard to the patient.

In CZ patent 299305 is described a sensing electrode for pH measurement mostly in bodily fluids consisting of electrically nonconductive polymeric substance selected from a group consisting of polycarbonate, polyethylene, polypropylene, polystyrene or their copolymers or modified cellulose. A pH sensitive antimony layer connected by means of a secondary conductor with a measurement device isolated from the liquid system, in which pH is measured, whereas an nonconductive underlay has a shape of hollow cylinder thickened in its part into a shape of a ring or a sphere.

Fundamentals of the invention

The above mentioned disadvantages are eliminated by a catheter for measurement of bodily fluid properties, distinguishing itself as a catheter employing impedance measurement consisting of at least two electrodes in a shape of hollow cylinder, where at least its one part has an electrically conductive surface, which is connected by means of a secondary conductor with a measurement device isolated from the liquid system, in which impedance is measured, whereas in the case of using more electrodes for impedance measurement these electrodes are placed above each other and they are connected with each other by tubing, whereas the secondary conductors are carried out through the cylinder hollow and through the tubing. An electrode for impedance measurement can consist of a body in the shape of hollow cylinder of electrically conductive materials selected from the group consisting of metals such as Sn, Ni, Cu, Al, Ag, or its conductive compounds or from the composite polymer materials with electrically conductive - metal or a graphite mixture.

A catheter for measurement of bodily fluid properties, especially a catheter using impedance for pH measurement consists of at least two electrodes for impedance measurement in a shape of hollow cylinder, where at least its one part has electrically conductive surface, which is connected by means of a secondary conductor with measurement device isolated from the liquid system in which impedance is measured; and from at least one pH electrode consisting from electrically nonconductive underlay in a shape of hollow cylinder with pH sensitive layer deposited onto, which is connected by means of a secondary conductor with the measurement isolated from the liquid system in which impedance and pH is measured, where measurement device is a combined conductivity-meter and voltmeter to which one reference electrode is connected, whereas measurement electrodes are placed above each other and they are connected with each other by tubing, whereas the secondary conductors are carried out through the cylinder hollow and through the tubing.

An electrode for impedance measurement can consist of electrically nonconductive polymeric underlay with electrically active surface, which is selected from the group consisting of metals such as Sn, Ni, Cu, Al, Ag₁ or its conductive compounds such as silverchloride (AgCI). An electrically active surface can be also an electric conductor from the group of doped conjugated polymers such as polythiofene, polyaniline, polypyrrole, polyfenylene or poly(p-fenylenvinylene).

An underlay of electrode for impedance measurement can be completelly electrically conductive as a whole, and can consist of acrylonitril/butadiene/styrene with graphite admixture.

An underlay of an electrode for impedance or pH measurement is preferably from electrically nonconductive polymeric substance and it is selected from the group consisting of polycarbonate, acrylonitril/butadiene/styrene, polyethylene, polypropylene, polystyrene or their copolymers or polymeric gells or modified cellulose.

An underlay of electrode for impedance or pH measurement preferably a hollow cylinder shape where its central part is widened into a shape of a ring or a sphere.

An underlay body of the electrode for impedance measurement, or an electrically active surface on the underlay, or a pH sensitive layer on the underlay are connected with a secondary conductor in a place, which is distal to the measured liquid, by means of pressure from a conductive spring, adhered by conductive glue, by metal plating or by a combination of tese methods.

A pH sensitive layer or an electrically active surface is preferably placed on a widened part of underlay. A pH sensitive layer or electrically active surface is deposited onto nonconductive underlay by a metal deposition method, where a metal is evaporated under a vacuum - sputtering, magnetron sputtering, radiofrequency sputtering, diode plasma sputtering, cathodic arc evaporation, ion plating, ionization-assisted evaporation, ion implantation, or laser alloying.

A pH sensitive layer and/ or electrically active surface of a thickness greater than 1 micrometer is deposited by magnetron sputtering onto the underlay in vacuum in an inert gas environment consisting mostly of argon. An electrically active surface is deposited onto conductive underlay electrochemically or by a metal deposition method, where a metal is evaporated under a vacuum - sputtering, magnetron sputtering, radiofrequency sputtering, diode plasma sputtering, cathodic arc evaporation, ion plating, ionization-assisted evaporation, ion implantation, or laser alloying. An electrically active surface consisting from electrically conductive doped conjugated polymer is deposited on the underlay from water colloid dispersion. A secondary conductor is selected from electrically conductive materials selected from the group consisting of Cu, Al₁ Ni, Ag₁ Au, Pt in the shape of an insulated wire, or by an insulated carbon fiber.

The catheter according to the invention enables measuring of impedance, or combined impedance and pH of the bodily fluids simultaneously. Impedance and pH electrodes preferably have the same shape while combined into one catheter. They consist from an underlay in a shape of a hollow cylinder, where its central part is preferably widened into a shape of a ring or a sphere. The material of an underlay can be either polymeric nonconductor analogous to the pH electrode, or it can be composite conductive plastic such as ABS (acrylonitril/butadiene/styrene) with graphite admixture, or the impedance electrode can form a hollow cylinder shaped body created directly from the electrically conductive metal. The impedance electrode is provided by electrically active surface from noble, rustproof metal in the case of polymeric underlay either conductive or nonconductive. This metal can be. Sn, Ni, Cu, Ag, R, Al or its conductive compounds e.g. silver chloride (AgCI). The electrically active surface of a conductor can be also formed by doped conjugated polymers, such as doped polythiofene, polyaniline, polypyrrole, polyfenylene or poly(p- fenylenvinylene).

A secondary conductor is carried out through the hollow center of the cylinder. The first end of a secondary conductor is connected with electrically active surface of an underlay and the second end goes through the underlay hollow and up the tubing towards the measurement device. An electrically active surface of the underlay is either a directly conductive underlay body, or it is an active coating deposited on the underlay surface.

The outer part of an underlay with an electrically active surface is covered by flexible elastic tubing. This covering prevents penetration of measured liquid to contact area of secondary conductor and electrically active surface of an underlay. The part of electrically active surface, which is in contact with measured liquid preferably on the widened part of an underlay. The second end of a secondary conductor going through the underlay hollow is together with the end of the underlay in the shape of cylinder compressed in another flexible elastic tube. A secondary conductor is then carried inside of this flexible elastic tube towards the measurement device or.conductivity-meter.in the case of impedance measurement.

Flexible elastic tubes are preferably glued to an underlay. Individual electrodes can be linked by flexible elastic tubes. Separated secondary conductors go through these tubes towards the measurement device. A combined voltmeter and conductivity-meter is preferred for combined monitoring of pH and impedance. Each meter is then connected to its data logger.

A catheter for measurement of electrochemical properties, mainly the impedance and pH of bodily fluids according to the invention consists of any number of measuring electrodes placed sequencialy where each of them is connected to a measuring device by means of a secondary conductor. This modular solution greatly simplifies catheter assembly and reduces manufacturing cost when compared to current technologies.

The advantage of these catheters according to this invention, is ease in manufacturing plus the allowance of continuous functionality checks of a catheter during manufacturing with more reliable and more durable connection of a secondary conductor to the electrode.

Electrodes are not placed outside of one long catheter, but on the contrary, partly inside. A catheter consisting of of flexible elastic tubing, is placed outside on the narrowed ends of measuring electrodes. A flexible body of a catheter is pulled over a contact part of an electrode and one end of a secondary conductor, and presses on this contact. A contact is secured not only by means of a conductive glue, but also by the pressure of an electrode against a flexible elastic tube on the catheter. pH and/or impedance electrodes are added in successive steps at the end of a catheter. One secondary conductor, going through inside of a catheter, is easily pulled out of a catheter. An advantage is easy manipulation with secondary conductors without breaking. Secondary conductors are easily taken out in the lenghtwise direction of a catheter through the length of the inside diameter, which is much bigger than traditional small perforations placed upright on the side wall of current catheters. This prevents possible twisting of a secondary conductor, or possible accidental removal of two or more secondary conductors and their back pushing in a catheter. Drastic bending of a secondary conductor in a small area is eliminated . Also a secondary conductor can be easily pulled out of a catheter in its longitudinal axis when the functionality of the secondary conductor is in question without bending or jepordizing the functionality of other secondary conductors placed inside of a catheter. Also, if the level of conductivity in a secondary conductor is questioned, it can be measured and verified without re-measuring other secondary conductors. Secondary conductors are not at risk of damage by abusive manipulation used in current manufacturing methods. A questionabledoubtful secondary conductor does not have to be measured at all, and it can be pulled out and disposed of easily.

Manufacturing of catheters according to this invention is, in comparison with current methods, simplified,, easily reproduced and economical. It enables miniaturization of an electrode. Conductive and nonconductive underlay from plastic can be easily molded in molds of a desired shape. A conductive metal can be deposited on a small plastic pressing/casting by a method such as vacuum sputtering, where each sputtering batche can be over a hundred thousand pieces.

This method also allows ease in automatization of other manufacturing steps. High reproducibility in important parameters (offset, gain, drift and lifetime) eliminates cumbersome and expensive calibration. Calibration is currently performed with all existing pH electrodes by the clinician during set up. This calibration takes up to 70% of the procedure time with current measuring systems. Calibration during set up is difficult and problematic, requiring the training of medical staff. Also the buffer used is unstable due to lack of temperature control. Experience shows, that these variables can cause error of up to one pH, which can negatively influence the result of an examination. If we add also drift during tens of hours of use, these results in high inaccuracy. Some companies consider it necessary to calibrate their devices again after patient use, to eliminate at least some of errors of measurement. An advantage of sensing electrodes according to this invention is, that calibration of each single electrode is not required.

Electrodes manufactured according to the method of this invention are intended for single use, which is more hygienic. Contemporary catheter sterilization is done because of their high price. If the disposable electrodes/catheters are more affordable, multiple use catheters will not be necessary. Nevertheless re-sterilization and multiple use of impedance electrodes manufactured from one piece conductors, such as metal, is made possible. The durability of the catheter, not the electrodes, will be the limiting factor in how many times a catheter is used. Electrodes will not be considered spentby conductivity changes. Conductivity will remain constant. Re=sterilization and catheter reuse is possible also with electrodes havingplastic underlay with deposited electrically active surfaces. The thickness of the electrically active surface is important in this case. By controlling the thickness of electrically active surface on an underlay it is possible to limit the active lifetime of the electrode. This is important particularly from a hygienic and safety point of view. A thin active surface prevents multiple use of an electrode.

A catheter in accordance with this invention is capable of measuring impedance and pH both separetely and simultaneously.

Figures summary

Fig. 1- illustrates design of a catheter, which consists from two types of shape identical electrodes in a shape of a hollow cylinder for impedance measuring. Two electrodes consist of an underlay with electrically active surface and one is made from a body of an electrically active material. Fig. 2 - illustrates design of a combined catheter which consists from one pH electrode and multiple electrodes for impedance measurement manufactured from nonconductive and/or conductive plastic underlays with electrically active surface.

Design examples Fig. 1- design of a catheter, which consists of three electrodes for impedance measuring. Two electrodes consist of an electrically nonconductive underlay 1, in form of a hollow polycarbonate cylinder 7 mm long. The cylinder is wider in the middle. The diameter of this middle section is 2 mm and length is 3 mm and represents about 1/3 of the total cylinder length. There is an electrically active surface 9 of tin (Sn), for impedance measuring. The third electrode consists of a body 10 of the same shape made from copper, Cu.

The thicker middle part in the shape of cylinder or sphere has the best surface to volume ratio. A current density is higher, which results in a stable reading at measuring device 6.

An electrode with a thicker middle part in the shape of a sphere does not suffer from false reading due to an attachment to an esophagus wall, which an electrode with flat sensitive area may exhibit, when a measured liquid cannot reach the sensitive surface. An electrically active surface 9 is connected - clamped and glued - to a secondary wire conductor 3, which goes down through an underlay hollow 1 and its non-insulated tip touches on distal, narrowed part of an underlay 1 with an electrically active surface 9^ A flexible polyurethane tube 4J. of outer diameter 2mm is pulled over this underlay 1 end and presses a secondary conductor 3 against an electrically active surface 9. The flexible polyurethane tube 4,3 is connected to a proximal (close to the measuring device 6) end of an underlay 1. A secondary conductor 3 goes through this flexible polyurethane tube 4^3 towards a measuring device 6. An electrically active surface 9_j_on the thicker part of an underlay 1 in a ring shape, is in contact with the measured solution. Tubes AA_x A_2 and 4J3 are glued to an underlay %. Another impedance electrode consisting of an underlay 1 and an electrically active surface 9_is connected to the bottom end of the first flexible elastic tube 4J^. Another impedance electrode consisting only from a body 10 from Cu is connected to the bottom end of this flexible elastic tube AΛ_. A secondary conductor 3 is connected/ glued to a surface of body Ij) and this connection is secured by tube 4^2, with dead end, which prevents of access of measured liquid inside of a catheter. All secondary conductors are made of insulated wire such as copper.

Fig. 2 - pictures the design of a combined catheter enabling simultaneous measurement of impedance and pH. Underlays 1 of impedance electrodes are made from polymeric substances either electrically nonconductive or conductive. An underlay 1 of a pH electrode is made from polymeric electrically nonconductive material, polycarbonate.

The first underlay 1 of pH electrode (in the picture at the top part under measuring devices 6) is equipped with pH sensitive layer 2. Four secondary conductors 3 and one conductor 7 from reference electrode come through an underlay 1 hollow. One secondary conductor 3 is taken out of an underlay 1 hollow and it is connected with a part of pH sensitive layer 2j on the surface of an underiay_J.. This contact area of underlay 1 is covered by the first flexible elastic tube 4J., which prevents of penetration of measured liquid to junction of secondary conductor 3 and pH sensitive layer 2. The upper end of underlay 1 hollow of pH electrode is covered by third flexible elastic tube 4^3 going to measurement device 6. The lower end of the first tube 4J. is pulled over another end of underlay 1 of impedance electrode. Lower part of this underlay 1 is compressed by another first flexible elastic tube 4J., which prevents penetration of measured liquid to junction of secondary conductor 3 and an electrically active surface 9, which is deposited on this underlay 1 of impedance electrode. Another pH electrode is attached to the lower end of this first flexible elastic tubing 4J.. There is another first flexible elastic tube 4J. pulled over the lower end of this pH electrode and connecting this lower end of this pH electrode and upper end of the second impedance electrode. The second flexible elastic tube 42 is pulled over the lower end of this impedance electrode. This secondary flexible elastic tube 42 is closed and contains an Ag/AgCI reference electrode preferably of the same shape as the pH and impedance electrodes, but it can have any shape. Secondary conductors 3 and reference electrode conductor 7 are pulled through all tubes and electrode hollow centers. The second ends of secondary conductors 3, connected with impedance electrodes, are linked to conductivity-meter. A secondary conductor 3 of pH electrode and reference electrode conductor 7 are connected to a voltmeter. A reference electrode 5 can be an external one - placed entirely outside of a catheter.

The whole surface of an underlay 1 for pH measurement is covered by an electrically conductive, pH sensitive layer 2 of antimony. The antimony layer of 99.99% purity and 9 micrometer thickness is sputtered in a planar magnetron with double rotation in argon inert atmosphere of pressure 100 militorr and cathode potential -1kV. The pH sensitive layer 2 of antimony forms metal/oxide equilibrium spontaneously after the deposition when placed in free air or during the first minutes of measurement in a solution.

A layer of Sn, was sputtered on an underlay 1, for impedance measurement, made of acrylonitril/butadiene/styrene (ABS) with a graphite mixture in the same way.

Contact areas between an underlay 1 and flexible elastic tubes 4.1. 4.2 and 4.3 are glued by UV curable epoxy in such a way that there is no leak in the vicinity of an underlay 1, so no measured liquid could exist here. Liquid in such a cavity would lead to faulty wash out of a liquid and slowing down the pH response. Another reason is to protect accidental intrusion of a liquid to a secondary conductor 3 and also to increase catheter's tensile strength. An pH electrode constructed in this manner sustained in buffer pH=7 more than 24 hours had a drift of less than 5mV/24 hours. By contrast, pH electrodes manufactured by an electrochemical deposition on the copper base have drift from 15 to 2OmV during one hour and antimony casted electrodes have drift from 15 to 25 mV/24 hours. Unlike contemporary manufacturing technologies of sensing electrodes, this system of modular catheter allows the important advantage of easy assembly and a price for a multiple-electrode catheter that is similar to the price of a single-electrode catheter. It will also be possible to make special catheters fitted to a patient from prepared modules - electrodes, easily connected linked together, according to a doctor's specifications. One benefit for the patient is the use of a low-costmodular multiple- electrode catheter within the first 24 hours. Presently the basic 24 hours measurement of esophageal reflux is carried on by a catheter with one pH electrode placed 5 cm above the esophageal sphincter, because of its lower price. If it is verified that a patients problems are caused by insufficient closing of lower esophageal sphincter characterized by regurgitation of HCI into esophagus, there is a need to know a reflux volume i.e. height level, by 24 hour surveying with a more expensive, multiple-electrode catheter. An adult human esophagus is from 20 to 24 cm long, which means a catheter with four sensors placed 4-5 from each other is chosen. This spot is specified in accordance with patients needs by other catheters tailored to a patient. Multiple measurement is uncomfortable for the patient - the catheter is inserted into the esophagus through the nose, from which it connects to an external portable voltmeter with recording system and remains during the entire recording time. As for the medical staff - there are necessary repetitive patient's visits and treatment is more expensive. Manufacturing and use of a multiple-electrode catheter according to this invention will be similar in cost to a simple single one, so its application can be placed during the first patients visit. To prepare custom-made catheter will be similarly easy as the basic catheter. This modular system is easily personalized to the particular demands of a patient. In the case of a child with a shorter esophagus, all measured electrodes could be placed along the length of 8 cm, for example. It is possible to easily manufacture a custom-made catheter made-to-measure a patient with anomalies in a certain part of esophagus. An advantage of contemporary measurement of pH and impedance is monitoring of both acidic and alkalic (duodenal ) reflux at the same time, during one monitoring session.

Utility of the patent

An electrode according to invention can be used mainly for continuous measurement of pH and impedance in the case of esophageal reflux. In light of its possible miniaturization and possibility to building-in catheters, it is suitable for using in medicine, for pH and impedance measurement of bodily fluids.

Claims

1. A catheter for measurement of bodily fluids properties, distinguishing itself that catheter for impedance measurement consists of at least two electrodes in a shape of hollow cylinder, where at least its one part has an electrically conductive surface, which is connected by means of a secondary conductor (3) with measurement device (6) isolated from the liquid system, of which impedance is measured, whereas in the case of using more electrodes for impedance measurement these electrodes are placed sequentially and connected by tubes (4.1 , 4.2..), whereas the secondary conductors (3) are carried out through the cylinder hollow center and through the tubes (4.1, 4.2..).

2. A catheter according to claim 1 , is unique by virtue of an electrode for impedance measurement that consists of a body (10) in a shape of hollow cylinder which is made of electrically conductive materials selected from the group consisting of metals such as Sn, Ni, Cu, Al, Ag, or its conductive compounds or from the composite polymer materials with electrically conductive - metal or a graphite mixture. 3. A catheter for measurement of bodily fluid properties, unique by virtue of the fact that the catheter measures both impedance and pH, consisting of at least two electrodes for impedance measurement in a shape of hollow cylinder, where at least its one part has electrically conductive surface, which is connected by means of a secondary conductor (3) with a measurement device (6) in a place, which is isolated from the liquid system, of which impedance is measured, and from at least one pH electrode consisting from electrically nonconductive underlay (1) in a shape of hollow cylinder with a deposited pH sensitive layer (2), which is connected by means of a secondary conductor (3) with measurement device (6) isolated from the liquid system, of which impedance and pH is measured, where measurement device (6) is combined conductivity-meter and voltmeter to which one reference electrode (5) is connected, whereas measurements electrodes are sequentially connected with each other by tubes (4.1 , 4.2..), whereas the secondary conductors (3) are carried out through the hollow center of the electrode and through the tubes (4.1 , 4.2, 4.

3).

4. A catheter according to claims 1 and 3, unique in that the electrode for impedance measurement consists of electrically nonconductive polymeric underlay (1) with electrically active surface (9), which is selected from the group consisting of metals such as Sn, Ni, Cu, Al, Ag, or its conductive compounds such as silverchloride

(AgCI), or from the electric conductor from the group of doped conjugated polymers.

5. A catheter according to claims 1 and 3, unique in that underlay (1) of electrode for impedance measurement is electrically conductive and consists of acrylonitril/butadiene/styrene with graphite admixture.

6. A catheter according to claims 1 and 3, unique in that underlay (1) of electrode for impedance or pH measurement is from electrically nonconductive polymeric material selected from the group consisting of polycarbonate, acrylonitril/butadiene/styrene, polyethylene, polypropylene, or their copolymers or modified cellulose.

7. A catheter according to claims 1 to 6, unique in that underlay (1) of electrode for impedance or pH measurement has a shape of hollow cylinder where its central part is widened into a shape of a ring or a sphere.

8. A catheter according to claims 1 to 7, unique in that underlay (10) of electrode for impedance measurement, or electrically active surface (9) on underlay (1), or pH sensitive layer (2) on underlay (1 ) are connected with a secondary conductor (3) in a place, which is distal to the measured liquid by means of pressing, by conductive spring, by gluing by conductive glue, by metal plating or their combination.

9. A catheter according to claims 1 and 3 to 8, unique in that pH sensitive layer (2) or electrically active surface (9) is placed on widened part of underlay (1 ).

10. A catheter according to claims 1 and 3 to 9, unique in that pH sensitive layer (2) or electrically active surface (9) are deposited onto nonconductive underlay (1) by method, where a deposited metal is evaporated under a vacuum - sputtering, magnetron sputtering, radiofrequency sputtering, diode plasma sputtering, cathodic arc evaporation, ion plating, ionization-assisted evaporation, ion implantation, or laser alloying.

11. A catheter according to claims 1 and 3 to 10, distinguishing itself that pH sensitive layer (2) and/ or electrically active surface (9) of thickness bigger than 1 micrometer is deposited by magnetron sputtering onto the underlay (1) in vacuum in an atmosphere of an inert gas, mostly argon.

12. A catheter for measurement of bodily fluid properties according to claims 1 and 3 to 9, unique in that electrically active surface (9) is deposited onto electricaly conductive underlay (1) electrochemically or by method, where a metal is evaporated under a vacuum - sputtering, magnetron sputtering, radiofrequency sputtering, diode plasma sputtering, cathodic arc evaporation, ion plating, ionization-assisted evaporation, ion implantation, or laser alloying.

13. A catheter according to claims 1 and 3 to 9, unique in that electrically active surface (9) consisting from electrically conductive doped conjugated polymer is deposited on underlay (1) from water colloid dispersion.

14. A catheter for measurement of bodily fluid properties according to claims 1 to 11 , unique in that secondary conductor (3) is selected from electrically conductive materials selected from the group consisting of Cu, Al, Ni, Ag, Au, Pt in a shape of an insulated wire, by an insulated carbon fiber.