WO2020249209A1

WO2020249209A1 - Catheter pressure monitoring system

Info

Publication number: WO2020249209A1
Application number: PCT/EP2019/065390
Authority: WO
Inventors: Matteo Leonardi
Original assignee: Lightsens Medical Sa
Priority date: 2019-06-12
Filing date: 2019-06-12
Publication date: 2020-12-17

Abstract

It is disclosed a catheter pressure monitoring system(100) comprising a catheter (6) including a shaft (20) having a proximal end (20b) and a distal end (20a) opposed to the proximal end (20b) which, in use, enters the body of a patient, a probe (15) in the shaft (20), the probe (15) including a pressure sensor (50) at a terminal end (15a) thereof, and the pressure sensor (50) being at the distal end (20a)of the shaft (20)or projecting from the shaft (20), wherein a fluid may flowthrough the shaft (20) between the probe (15) and the shaft (20). A valve (23) is arranged in the catheter (6) to close the flow through the shaft (20).

Description

TITLE: Catheter pressure monitoring system

Field of application

The present invention relates to a catheter pressure monitoring system for monitoring a pressure of a body fluid.

Prior art

A known body fluid pressure monitoring system includes a pressure transducer to monitor blood pressure signals in a patient’s vein or artery or in another part of the body.

A pressure transducer is typically mounted near the patient and connected to the patient’s vein, artery or to another part of the body via a catheter and a fluid-filled tube, on one side, and to the patient monitor, on the other side. Pressure transducers are usually disposables. Patient monitors may employ sophisticated algorithm to derive important parameters such as volumetric and hemodynamic parameters from a pressure signal.

In particular, the pressure signal is generated and transmitted from the measurement site (e.g., vein, artery, etc.) via the catheter and the fluid- filled tube as fluid pressure to the pressure transducer where it is converted to an electrical pressure signal outputted to the patient monitor.

Invasive pressure measurement as the ones carried out with the pressure monitoring system mentioned above serves as a guide to therapeutic interventions in complex surgeries, intensive care patients and whenever the patient condition requires a strict and precise control of the vital parameters. In such pressure monitoring system, inaccurate measurement may lead to erroneous diagnosis or to inadequate, unnecessary or potentially dangerous interventions.

However, the performance of the pressure monitoring system is influenced by lots of parameters, including the biomechanical characteristics of the system transmitting the pressure to the transducer and in particular, the characteristic of the fluid-filled tube (compliance and length), fluid connections and stopcocks determine the response of the sensor to a pressure signal.

The response of the pressure monitoring system highly depends on the setup, as entrapped air bubbles, loose connections, squeezed/ kinked tube, additional stopcocks or tubing modify that.

For an adequate pressure signal, Gardner defined the dynamic response requirement of such a pressure monitoring system, i.e. the natural frequency F_n [Hz] and the damping coefficient z (zeta). Those parameters (F_n and z) can be measured with a square test, which consists in analyzing the response of the pressure monitoring system to a square wave [Gardner RM. Direct blood pressure measurement - dynamic response requirements. Anesthesiology 1981 ; 54:227-36] generated by a “fast flush” with automatic flushing system described below.

Clinical experience has demonstrated the difficulty to maintain high quality of measured arterial pulse waveform also due to minute leaks in the fluid connections or stopcocks, which allow a small amount of blood to enter the catheter tip where it clots and it damps the signal. Even with a leak-proof system, clots still form at the catheter tip due to the small volume of blood, which enters as a result of transducer’s gauge volume displacement (typically 0.04 mm³/ 100 mmHg) and any volume displacement due to minute entrapped air bubbles in the tubing [Gardner RM, Warner HR, Toronto AF, Gaisford WD. Catheter-flush system for continuous monitoring of central arterial pulse waveform. J. Appl. Physiol. 1970; 29:91 1-3]. Other effect that might influence fluid displacement is the tubing that might be pinched, kinked or twisted. This phenomenon causes a push out of locking solution and once the pressure is lifted, the same volume that has been pushed out will create a backflow of blood at the catheter tip by negative pressure. To solve this problem, a continuous flush system is added to the system. It consists in a pressurized saline bag that has to be kept at constant pressure (usually at 300 mmHg), which pushes saline thought a fluid resistance, creating a continuous flow of around 3 ml/ hour, which is considered sufficient to prevent blood entering the catheter tip and not too much to create a big bias in the signal. Pressure of the saline bag has to be periodically checked, as it is not rare that it is depressurized. In practice, it still happens that blood enters the catheter tip where it clots.

As a result, the measured signal may be inaccurate and unreliable due to an inappropriate setup.

For this reasons, operators are asked to periodically check the waveform quality to detect a possible over or under-damped signal and, if it is the case, try to identify possible cause (related to the parameters mentioned above) and fix the setup in order to restore an adequate dynamic response, which is essential.

In case of doubt, dynamic response can be tested with a square test, i.e. with a“fast flush”.

Such a pressure monitoring system, with tubing from catheter to the transducer and the flushing system with the pressurized saline bag is also cumbersome and uncomfortable.

The main features of the pressure monitoring system described above are schematically represented with reference to Figure 1.

The pressure transducer 2 generates electrical pressure signals and transmits them to the patient monitor 3, which is adapted to display graphics of the pressure over time or more complex graphics, for instance, derived from volumetric and hemodynamic parameters from the pressure signal.

The pressure transducer 2 is mounted near the patient on a holder 7 at the same height of patient’s heart and connected to a vein 4, artery or to another part of the body via the catheter 6 and the fluid-filled non- compliant tube 5 on one side. On the other side, the pressure transducer 2 is connected to a pressurized saline bag 9. A fluid resistance inside the pressure transducer’s housing 2 creates a continuous flow through the system. An automatic flushing system is also provided inside the pressure transducer’s housing 2. It consists of a silicone valve that can be pulled and opens the fluid resistance, therefore creating a fast flush. The holder 7 and pressurized saline bag are attached to an IV pole 10. During use, a pressure signal is generated and transmitted to the pressure transducer 2 from the measurement site 4 (e.g., vein, artery, etc.) via the catheter 6 and the fluid-filled tube 5, as a fluid pressure. The pressure transducer 2 converts the fluid pressure into an electrical pressure signal and transmits it to the patient monitor 3. A stopcock 8 adjacent to the transducer allows to selectively directing flow for priming and zeroing of the system as well as blood sampling. Another stopcock 1 1 adjacent to the catheter 6 allows for blood sampling.

As mentioned above, an appropriate setup of the pressure monitoring system is difficult to achieve and, when the system is not precisely set it may be difficult to use or the measured signal may be inaccurate and unreliable.

All these problems in the measurement are particularly undesirable for taking critical therapeutic decisions in complex surgeries, intensive care patients and whenever the patient condition requires a strict and precise control of the vital parameters.

At last, such a blood pressure monitoring system is cumbersome and not easy to be handled, due do several connections between the pressure bag 9 and the pressure transducer 2, between the pressure transducer 2, the non-compliant tube 5 and the electric device 3, as well as for the IV pole 10 which is necessary to transport and place the system near the patient.

It has also to be considered that appropriate placement of the support 7 with respect to the patient is necessary to avoid undesired biases in the measurement, due to a different height of the patient’s heart with respect to the pressure transducer 2.

To summarize, a blood pressure measurement made through the blood pressure monitoring system of the prior art may largely depend from uncontrollable factors and circumstances, which may cause danger for the patient or at least return wrong values misleading or affecting a cure (inaccurate and unreliable measurement). Moreover, the installation and positioning of the system is complicated and creates impediment for the movement of the healthcare professional (cumbersome and uncomfortable system) .

The problem at the base of the present invention is to provide a body fluid pressure monitoring system, which is easier to install and more precise in measuring the pressure and corresponding derived measures, substantially uninfluenced by external factors, therefore solving all the problems correctly affecting the prior art system.

Summary of the invention

The idea at the base of the present invention is that of providing a catheter pressure monitoring system wherein a body fluid pressure value is measured through a probe, in particular a probe running inside a catheter and including a pressure sensor at a tip, the pressure sensor being arranged at an opening of the catheter which, in use, is in a vein, artery or another body part of the patient, where the pressure value is to be measured or being arranged projecting from said opening of the catheter. A valve is arranged in the catheter to close a flow of a fluid through the catheter, the fluid flow being allowed when the valve is open.

According to the solution idea above, the technical problem at the base of the present invention is solved by a catheter pressure monitoring system comprising

-a catheter including a shaft having a proximal end and a distal end opposed to the proximal end which, in use, enters the body of a patient,

-a probe in the shaft, the probe including a pressure sensor at a terminal end thereof, and the pressure sensor being at the distal end of the shaft or projecting from the distal end to measure a pressure, in use, wherein a fluid may flow through the shaft in a space between the probe and the shaft and wherein

- a valve is provided in the catheter to close the flow through the shaft.

The probe is also indicated in the description below as sensor probe. The probe is connected to the catheter, for instance with a Luer-lock connection.

In use, the probe may be connected to the catheter after the catheter has been inserted in the body.

A section of the probe is therefore minor that a section of the catheter.

More particularly, a space between the sensor probe and the shaft of the catheter is provided to allow fluid sampling (e.g. blood) and fluid injection (e.g. saline flush) also when the probe is in the catheter, provided that the valve is open.

In this respect, the valve is opened each time a blood sampling or a fluid injection is needed.

A saline flush is performed to clear the catheter before closing the valve.

The closure of the valve avoids blood influx in the catheter, so preventing the patency of the catheter due to creation of a clot making blood sampling impossible, without the need of a continuous flush system.

To the contrary, in the system of the prior art, a continuous flush system is required and with a depressurization of saline bag that has to maintain the continuous flush small volume of blood can enter the catheter as a result of loose connections, transducer’s gauge volume displacement, any volume displacement due to minute entrapped air bubbles in the tubing or the latter that might be pinched, kinked or twisted.

All these problems are solved by the catheter pressure monitoring system of the present invention.

Advantageously, body fluid pressure values measured at the catheter opening by the sensor probe are very accurate and therefore prevents from leading to erroneous diagnosis or to inadequate, unnecessary or potentially dangerous interventions.

Indeed, the measurement of the pressure value is not influenced by parameters such as biomechanical characteristics of the pressure measurement system or setup. In particular, the pressure has not to be transmitted to a transducer distanced from the catheter opening via a fluid-filled tube, but it is taken directly inside a vein, artery or in another body part of the patient.

The fluid-filled tube for transmission of pressure according to the prior art system is replaced by a sensor probe transmitting the pressure value via a cable, for instance an optical fiber, in the case of a fiber optic pressure sensor is used, or an electrical cable, in the case of a piezo- resistive pressure sensor is used, which is completely uninfluenced and independent from tubing, fluid connections and stopcocks to which the catheter is connected. In other words, in the catheter pressure measurement system of the invention, there is no mechanical characteristic influencing the measure of the pressure or the transmission thereof to a remote device (patient monitor).

Advantageously, the setup of the catheter of the present invention is considerably simplified with respect to the system of the prior art.

No control are required after setup as to formation of air bubbles, loose connection, squeezed tube, kinked catheter or tubing, additional stopcocks or tubing, the measure of the pressure values and its transmission being completely independent from such conditions. Therefore, operators are also free from checking parameters such as natural frequency F_n [Hz] and the damping coefficient z (zeta), or to restore them, and may fully trust on the signal detected and transmitted from the pressure measurement system including the catheter of the present invention.

Moreover, and advantageously, the valve closes with a neutral or preferably a positive displacement of fluid, meaning that fluid is not moved (neutral displacement) along the catheter during closure or is pushed out (positive displacement) of the catheter during closure.

A continuous flush system is not required. This is a considerable advantage. Indeed, the catheter pressure measurement system of the present invention may be free from pressurized saline bag, since it does not require a continuous flow to prevent blood entering the catheter. This, further simplify controls of the system, such as continuous checks of the pressure of the saline bag, to prevent its depressurization, as instead required according to the prior art. Taking advantage from removal of the pressurized saline bag, the catheter pressure measurement system of the present invention is therefore less cumbersome and more comfortable than the system according to the prior art.

When a continuous infusion is needed, for instance to instill a drug or because it is a medical procedure requirement in a specific setting, the valve is kept open.

In one embodiment, a first end of the probe at the opening of the catheter or projecting from the opening of the catheter incorporates the pressure sensor. Advantageously, the pressure sensor is in direct contact with the body fluid to be measured, outside a distal opening of the catheter, in close proximity to such opening and precisely measures the pressure.

A probe-hub connected to the catheter includes a fluid connection port. A port is provided to take blood from the vein, artery, etc ... or to inject a liquid into said vein, artery, etc, through the catheter. The blood/ fluid so taken from (or injected into) the catheter is delivered to (or is taken from) a tube, a syringe, ... attached to the port, for instance with a Luer- lock connection.

A second end of the probe opposite to the first end at which the sensor is attached, is adapted to be connected to an electronic device, for instance to a control unit and then to a patient monitor or directly to a patient monitor, the control unit being integrated in the patient monitor.

Different height between measurement site (cannulation site) and patient’s heart can be set in the control unit or in the patient monitor, so that a software compensate the possible bias in the measurement.

In an embodiment, the probe is in a tube. The tube includes a rounded tip to avoid hurting body tissues, for instance a curved portion at an end of the tube delimiting an opening of the tube for the sensor with a section minor than a section of the remaining portion of the tube. The rounded tip may be integral with the tube or attached thereto. The pressure sensor is located close to the opening inside the probe tube, so that it is protected when the probe is manipulated, e.g. when it inserted in the catheter. Preferably, a covering layer is provided for protecting a membrane of the sensor from body fluid, for instance, a silicone gel.

The pressure sensor can be at the tip of the probe or on a side surface of the probe close to the tip.

The sensor probe is flexible in order to be easily inserted in the shaft of the catheter and to follow possible curvatures of the catheter inserted in the body, for instance in an artery.

Different materials may be employed for the tube of the probe in order to cover and protect the probe, i.e. the sensor and its cable. In a preferred embodiment, the tube is in polyimide, flexible and biocompatible.

Preferred embodiment of the catheter pressure monitoring system according to the present invention are given in the dependent claims.

Further advantages of the catheter pressure monitoring system according to the present invention will be apparent from the following description given with reference to the attached drawings only for exemplificative and not limitative purpose.

Further, a catheter pressure monitoring system including a probe at the opening of the catheter or projecting from the opening is disclosed, wherein the catheter, however, does not include a valve. This system may be used to monitor pressure of a body fluid. The catheter according to this disclosure has same features as the catheter according to the present invention (except the valve), accordingly not repeated.

Brief description of the drawings

Figure 1 is a schematic representation of a body fluid pressure monitoring system according to the prior art. Figure 2a and 2b are schematic representations of a catheter pressure monitoring system in an open and respectively in a closed position, according to the present invention.

Figure 3a and 3b are schematic representations of a catheter pressure monitoring system in an open and respectively in a closed position, in a different embodiment of the present invention.

Figure 4 is a schematic exploded representation of a catheter pressure monitoring system according to the present invention.

Detailed description

With reference to figures 2a and 2b it is disclosed a catheter pressure monitoring system 100 according to the present invention, in particular a catheter pressure monitoring system 100 for monitoring pressure signals in a patient’s vein or artery or another part of the body.

The catheter pressure monitoring system 100 includes a catheter 6 with a sensor probe 15, represented separately in figure 4.

The accuracy and reliability of the pressure signal transmitted from a measurement site (e.g., vein, artery, etc.) via the catheter pressure monitoring system 100 is particularly important. Indeed, pressure measurement carried out with the catheter pressure monitoring system 100 of the present invention serves as a guide to therapeutic interventions in complex surgeries, intensive care patients, and whenever the patient condition requires a strict and precise control of the vital parameters, wherein inaccurate measurement may lead to erroneous diagnosis or to inadequate, unnecessary or potentially dangerous interventions.

Furthermore, patient monitor may employ sophisticated algorithm to derive important parameters such as volumetric and hemodynamic parameters from the pressure signal, which need an accurate and reliable signal.

The catheter pressure monitoring system 100 of the present invention aims to provide very precise measurements and therefore to improve the performance, without being influenced by external parameters such as biomechanical characteristics of the system transmitting the pressure.

The catheter 6 of figure 4 includes a shaft 20, having a proximal end 20b and a distal end 20a opposed to the proximal end 20b which, in use, is adapted to enter the body of a patient.

The catheter 6 includes a catheter-hub 60 adapted for connection with the probe 15. The catheter 6 has a predetermined length C, comprising a length of the catheter-hub 60 and a length of the shaft 20. The shaft 20 has a section Ai and it is flexible.

For instance, the catheter 6 is a standard catheter of the type used for vessel cannulation.

The probe 15 is running inside the catheter 6. The probe 15 is flexible in order to be easily inserted in the shaft 20 of the catheter 6 and to follow possible curvatures of the shaft 20 when it is inserted in the body, for instance in an artery or a vein.

A pressure sensor 50 is at an end 15a of the probe 15, for instance on the tip of the probe. The pressure sensor 50 is adapted to measure a pressure value in direct contact with a body fluid to be measured.

A section A2 of the probe 15 is minor than the section Ai of the shaft 20.

According to an aspect of the present invention, the catheter 6 of length C and section Ai has to be paired with a probe 15 adapted to be correctly fitted in it, in particular a probe 15 with a section A2 minor of the section Ai of the shaft 20, also adapted to let the fluid, in use, to flow in a space between the shaft 20 and the probe 15. Moreover, the probe 15 has a length L, comprising the length of its hub 16, adapted to place the pressure sensor at the distal end 20a of the shaft or projecting from the distal end 20a of the shaft 20, when the probe 15 is connected to the catheter 6.

The probe 15 includes a cable 30 connected to the pressure sensor 50, for instance an optical fiber 30 in the case of a fiber optic pressure sensor 50 or an electrical cable 30 in the case of a piezo-resistive pressure sensor 50.

The pressure sensor 50 is mounted and connected to an end 30a of the cable which transmits the pressure value.

A second end 30b of the optical fiber or electrical cable opposite to the first end 30a, is adapted to be connected to an external electronic device, for instance to a control unit and then to a patient monitor or directly to a patient monitor, the control unit being integrated in the patient monitor.

According to an embodiment of the invention, the optical fiber or electrical cable 30 is inside a tube 18 of the probe 15. The tube 18 is flexible. In a preferred embodiment, the tube is in polyimide flexible and biocompatible.

The tube includes an opening at an end, where the pressure sensor 50 is located. The opening of the tube is at the first end 15a of the probe. The opening can be at the tip of the probe or on a side of the probe, close to the tip.

The tube 18 provides a protection for the optical fiber 30 or the electrical cable 30 and the sensor 50. In a preferred embodiment, the tip of the probe 15a is rounded in order to avoid hurting body tissues.

According to the present invention, the catheter pressure monitoring system 100 includes a valve 23 in the catheter adapted to closes the flow of fluid through the shaft 20.

The pressure measurement is not affected, for instance by the closure of the flow, as in the prior art system because the probe 15 is at the opening of the shaft 20 of the catheter 6 or protruding therefrom. The closure of the flow as provided by the present invention avoids blood influx in the catheter, so preventing the patency of the catheter 6 due to creation of a clot making blood sampling impossible, without the need of a continuous flush system.

According to different embodiments of the present invention, the valve closes a fluid path at different portion of the catheter. Only for exemplificative purpose, two different embodiments are given below with reference, respectively, to figure 2a-2b and 3a-3b.

In all the embodiments, the probe-hub 16 includes a fluid connection port 22 to take blood from the vein, artery, etc ... or to inject a liquid into said vein, artery, etc, through the catheter, when the valve is open.

Still in all the embodiments, the catheter 6 includes a catheter-hub 60 and the probe 15 includes a probe-hub 16, wherein the catheter-hub 60 and the probe-hub 16 are coupled one to the other by connection means 19, preferably releasable, for instance a Luer-lock connection.

In the embodiment of figure 2a-2b, the valve 23 is in the catheter-hub 60 and closes a fluid path between the shaft 20 and the catheter-hub 60. In use, the fluid present between the probe 15 and the shaft 20 before closure of the valve 23 prevents flow of a body fluid into the shaft 20 after closure of the valve 23.

Still according to this embodiment, the probe 15 is movable towards the distal end 20a in an axial direction of the shaft 20 and is movable backwards from the distal end 20a in the axial direction of the shaft 20. In particular, the valve 23 is a shutter arranged on a portion of the probe 15 in the catheter-hub 60. The shutter has a cross section greater than a cross section of the shaft 20, and closes the fluid path by contacting the catheter hub 60, on an internal surface thereof, when the probe 15 is towards the distal end 20a. The shutter opens the fluid path when distanced from the catheter-hub 60, with the probe 15 retracted backward in the axial direction of the shaft from the distal end.

Means 70 are arranged between the catheter-hub 60 and probe-hub 16 to support the movement of the probe towards or backwards the distal end 20a. The means 70 to support the movement are further configured to keep the probe 15 towards the distal end 20a, when the flow has to be closed, or to keep the probe 15 backwards from the distal end 20a, when the flow has to be opened.

In one embodiment, the means 70 are elastic means 70, for instance spring means, arranged between the catheter-hub 60 and probe-hub 16. For instance, the elastic means 70 are compressed when the probe 15 is towards the distal end 20a or released when the probe 15 is backward from the distal end 20a. In this embodiment, releasable fastening means are provided to keep the probe 15 towards the distal end 20a with the elastic means compressed, in closure.

Any other mechanic or hydraulic mean (for instance a sliding or a screw mechanism) may be adopted in replacement of the means 70 with a same function, i.e. moving backward and forward and keep and fasten the shutter in the axial direction of the shaft 20.

Advantageously, according to the embodiment disclosed above, the closure of the valve makes a positive flush, i.e. it discharges portion of the fluid present between the probe 15 and the shaft 20 outside the catheter 6, therefore clearing the catheter 6.

The valve 23 may be opened, sliding the probe 15 of a distance dx in a direction (i.e. moving the probe 15 along the shaft 20 from the closed position represented in figure 2b to the opened position represented in figure 2a). On the other hand, the valve 23 may be closed, sliding the probe 15 of a distance dx in an opposite direction (i.e. moving the probe 15 along the shaft 20 from the opened position represented in figure 2a to the closed position represented in figure 2b). The probe 15 is at the opening of the catheter 6 or protrudes from the opening of the catheter 6.

In particular, according to different aspects of this embodiment of the present invention, the tip of the probe 15 may be retracted inside the shaft 20 when the valve is open and placed-at or projecting-from the opening of the shaft when the valve is closed (one aspect) or the tip of the probe 15 may be placed-at or projecting-from the opening of the shaft both when the valve is open or closed (second aspect). According to this embodiment, the valve 23 may for instance comprise a body 17 at an end 15b of the probe 15.

The body 17 has a section 17b greater than a section Ai of the shaft 20 and is adapted to close the proximal end 20b of the shaft 20. In particular, to close the proximal end 20b, the body 17 is placed or moved forward to abut against the catheter-hut 60 and, to open the proximal end 20b, is placed or retracted backward, leaving the proximal end 20b free.

The body 17 is enclosed between the catheter-hub 60 and the probe- hub 16.

The length C of the shaft 20 and the length L of the probe 15 are such that the pressure sensor 50 is at the distal end 20a of the shaft 20 or projects from the distal end 20a of a predetermined measure Ti, when the valve is closed.

A base of the body 17 may be attached to a base portion of the probe hub 16.

The base portion of the probe-hub may move towards the top portion of a distance dx under actuation of means 70 (for instance compression of the spring means 70), therefore moving the body 17 and the probe 15 towards the distal end 20a of the shaft, and closing the shaft 20 with the body 17 in abutment against the proximal end 20b; fastening means keep the probe 15 forward towards the distal end 20a of the shaft 20 with the spring means compressed.

The body 17 and the catheter-hub 60 may be shaped to improve closure. For instance, the body 17 includes a tapered portion 17a that match a tapered and enlarged portion of the catheter-hub 60. The tapered portion 17a of the body 17 is adapted to abut against the catheter-hub 60 to close the shaft 20. The tapered and enlarged portion of the catheter-hub 60 has a surface preferably parallel to a surface of the tapered portion of the body 17 in the region of abutment. Moreover, in order to improve closure, the body 17 is for instance made of a material (e.g. silicone) softer than a material of the catheter-hub 60.

In another embodiment represented in figure 3a-3b, the catheter pressure monitoring system 100 has a catheter including a valve 23 in the shaft 20. The valve 23 closes a fluid path between a first shaft portion placed upstream the valve 23 and a second shaft portion placed downstream the valve 23. The valve 23 is expandable from a first volume to a second volume, to close the fluid path, and is collapsible from the second volume to the first volume, to open the fluid path.

For instance, the valve 23 is an expandable and collapsible balloon, and the probe-hub 16 comprises an air duct in communication with the balloon, for insufflating air into or drawing air from the balloon. The probe-hub 16 includes a second via port 24 to connect means for air insufflation or suction through the air duct.

The valve 23 in the form of an expandable and collapsible balloon is arranged at a portion P of the probe 15 between the proximal end 20b and distal end 20a of the shaft 20, preferably at the distal end. The balloon is inflatable to close the space between the probe 15 and internal wall of catheter shaft 20 or debatable to open the fluid path between the probe 15 and the shaft 20, inside the catheter 6. Also according to this embodiment, however, the pressure sensor 50 is preferably arranged protruding from the distal end of the shaft 20 or at the distal end 20a.

Advantageously, according to this embodiment, the closure of the valve 23 creates a positive flush, therefore clearing the catheter 6, because the volume taken from the expanded valve 23 in the shaft 20 pushes out an equal volume of fluid from the shaft 20.

In all the embodiments of the present invention, the valve 23 closes with a neutral or preferably a positive displacement of liquid, meaning that liquid is not moved (neutral displacement) along the catheter during closure or is pushed out (positive displacement) of the catheter during closure.

The valve is opened each time a blood sampling or a fluid injection is needed.

Claims

1. Catheter pressure monitoring system (100) comprising

-a catheter (6) including a shaft (20) having a proximal end (20b) and a distal end (20a) opposed to the proximal end (20b) which, in use, enters the body of a patient, characterized by comprising

-a probe (15) in the shaft (20), the probe (15) including a pressure sensor (50) at a terminal end (15a) thereof, and the pressure sensor (50) being at the distal end (20a) of the shaft (20) or projecting from the distal end (20a) to measure a pressure, in use, wherein a fluid may flow through the shaft (20) in a space between the probe (15) and the shaft (20)

- a valve (23) in the catheter (6) to close said flow through the shaft (20).

2. Catheter pressure monitoring system (100) according to claim 1 , characterized by the fact that the catheter (6) includes a catheter-hub (60) and the probe (15) includes a probe-hub (16), the catheter-hub (60) and the probe hub (16) being coupled one to the other by connection means, preferably releasable.

3. Catheter pressure monitoring system (100) according to claim 2, characterized by the fact that said connection means is a Luer-lock connection.

4. Catheter pressure monitoring system (100) according to claim 2 or 3, characterized by the fact that the pressure sensor (50) is distanced from the probe-hub (16) by a predetermined distance (L), said distance (L) being set on a length (C) of the catheter (6), so as the pressure sensor (50) is at the distal end (20a) of the shaft (20) or projects from the distal end (20a) of a predetermined measure (Tl) with the valve (23) closed.

5. Catheter pressure monitoring system (100) according to claim 1 , characterized by the fact that the valve (23) is in the catheter-hub (60) and closes a fluid path between the shaft (20) and the catheter-hub (60), wherein, in use, said fluid present between the probe (15) and the shaft (20) before closure of the valve (23) prevents flow of a body fluid into the shaft (20) after closure of the valve (23).

6. Catheter pressure monitoring system (100) according to claim 5, characterized by the fact that the probe (15) is movable towards the distal end (20a) in an axial direction of the shaft (20) and is movable backwards from the distal end (20a) in the axial direction of the shaft (20), the valve (23) is a shutter arranged on a portion of the probe (15) in the catheter-hub (60), the shutter having a cross section greater than a cross section of the shaft (20), the shutter closes the fluid path by contacting the catheter hub (60) when the probe (15) is towards the distal end (20a) and opens the fluid path being distanced from the catheter-hub (60) when the probe (15) is backward.

7. Catheter according to claim 6, characterized by the fact that means (70), preferably elastic means, are arranged between the catheter-hub (60) and probe-hub (16) to support said movement of the probe towards or backwards the distal end (20a), wherein said means (70) to support the movement may be configured to keep the probe (15) towards the distal end (20a) in closure of the flow or keep the probe (15) backwards from the distal end (20a) in aperture of the flow.

8. Catheter pressure monitoring system (100) according to claim 1 , characterized by the fact that the valve (23) is in the shaft (20) and closes a fluid path between a shaft portion placed upstream the valve (23) and a shaft portion placed downstream the valve (23), wherein the valve (23) is expandable from a first volume to a second volume to close the fluid path and is collapsible from the second volume to the first volume to open the fluid path.

9. Catheter pressure monitoring system (100) according to claim 8, characterized by the fact that the valve (23) is an expandable and collapsible balloon, and wherein the probe-hub (16) comprises an air duct in communication with the balloon, for insufflating air into or drawing air from the balloon.

10. Catheter pressure monitoring system (100) according to claim 9, characterized by the fact that said probe-hub (16) includes a second via port (24) to connect means for air insufflation or suction through the air duct.

1 1. Catheter pressure monitoring system (100) according to claim 2 or 3, characterized by the fact that said probe-hub (16) includes a first via port (22) to connect means for blood sampling or an injection of fluid.

12. Catheter pressure monitoring system (100) according to claim 1 , characterized by including means for blocking the valve (23) in at least among an open or closed position.

13. Catheter pressure monitoring system (100) according to claim 1 , characterized by the fact that the pressure sensor (50) is a fiber optic pressure sensor (50) and said probe (15) includes an optical fiber (30) to transmit an optical signal from the pressure sensor (50).

14. Catheter pressure monitoring system (100) according to claim 1 , characterized by the fact that the pressure sensor (50) is a piezo- resistive pressure sensor (50) and said probe (15) includes an electrical cable (30) to transmit an electrical signal from the pressure sensor (50).

15. Catheter pressure monitoring system (100) according to claim 13 or 14, characterized by the fact that the probe (15) includes a flexible tube (18) around the optical fiber (30) or electrical cable (30), to protect the pressure sensor (50) and to prevent contacts of the pressure sensor (50) other than those with fluid(s), wherein the flexible tube (18) has an opened distal end.

16. Catheter pressure monitoring system (100) according to claim 15, characterized by the fact that said flexible tubular element (18) comprises polyimide around the optical fiber (30) or electrical cable (30).

17. Catheter pressure monitoring system (100) according to claim 1 , characterized by the fact that a proximal end (30b) of the probe (15) is configured to be connected to an electronic apparatus.

18. Catheter pressure monitoring system (100) according to claim 1 wherein a tip of the probe (15a) is rounded.