Apparatus and method for measuring physiological parameters

Abstract

The present invention relates to a measurement device (100) for measuring at least one physiological parameter, said measurement device (100) comprising a housing (101) comprising a measurement chamber (104) having an internal volume filled with a gas, a sensing cell (105) allowing at least a first physiological parameter to be measured and arranged in contact with said gas contained in said internal volume of said measurement chamber (104), and an inlet (107) for a physiological liquid of a patient, said inlet (107) being arranged such that said physiological liquid comes into contact with said gas, said gas being interposed between said sensing cell (105) and said physiological liquid of the patient, and creating an interface between said gas and said physiological liquid contained in said internal volume. The present invention further relates to a method for measuring at least one physiological parameter.

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for measuring at least one physiological parameter, and in particular to measuring the pressure of a physiological fluid taken from within a patient's body. More specifically, the present invention relates to an apparatus and method for measuring the pressure of a physiological fluid in contact with the central nervous system. The present invention relates to an apparatus and method for measuring the pressure of cerebrospinal fluid (CSF) taken, for example, by lumbar puncture.

[0002] Intracranial pressure corresponds to the pressure of the CSF inside the skull, in which the central nervous system is bathed. Quincke developed access to CSF ​​by lumbar puncture in 1891. The CSF pressure measured by lumbar puncture is also a measure of intracranial pressure (Non-Patent Document 1). Measurement of intracranial pressure by lumbar puncture has led to a major advance in neurology in understanding and identifying elevated intracranial pressure that threatens the central nervous system.

[0003] CSF pressure can be measured statically or dynamically: the static or hydrostatic approach is to measure the steady-state pressure and CSF pulsatility associated with the periodic oscillations of the heart and breath, and the dynamic or hydrodynamic approach is to apply a known stress to the intracranial fluid system, called a perfusion test, and analyze the system's response to this stress (Non-Patent Document 2).

[0004] The hydrostatic approach allows for the measurement of intracranial fluid pressure and the identification of normal pressure and elevated pressure, known as intracranial hypertension, which can cause headaches, nausea or vomiting, cognitive impairment, and in the most severe cases, coma.

[0005] The causes of intracranial hypertension syndrome are numerous and may include tumors, intracranial hematomas, space-occupying lesions such as hydrocephalus, and obstruction of the venous drainage system due to thrombophlebitis.

[0006] There are also "secondary" causes of increased intracranial pressure, such as endocrine disorders (Addison's disease, Cushing's disease, hypothyroidism, hyperparathyroidism), vitamin A deficiency which alters the structure of the arachnoid villi, drug intake (hormones, antibiotics, lithium, cimetidine), and various other conditions (sleep apnea, chronic renal failure, iron deficiency anemia).

[0007] The hydrodynamic approach can be achieved by injecting physiological serum into the CSF via lumbar puncture access. This injection of physiological serum stresses the intracranial fluid system. From the response of the intracranial system after the perfusion test, various relevant measurements can be extracted, including intracranial CSF flow measurements. An increase in flow resistance is an important parameter in clinical practice, as it can demonstrate objective changes in CSF circulation suggestive of hydrocephalus. [Background technology]

[0008] In the 1930s, Professor Henri Claude developed a manometer that included a flexible tube that connected directly to a lumbar puncture needle. The concept of the Claude manometer is to bring the cerebrospinal fluid into direct contact with the measuring part of the manometer. Claude's manometer is now banned for health reasons. Furthermore, Claude's manometer cannot measure the pulsatile nature of intracranial pressure.

[0009] Currently, there is no simple and reliable device on the market to quantify CSF pressure. Therefore, even in 2022, clinicians still measure CSF pressure by measuring the water column, as described by Quincke in 1891. For this, clinicians use a tailor's measuring tape manually along a disposable sterile flexible tube. In practice, the flexible tube is connected to a lumbar puncture needle. Although this primitive method may be sufficient to approximately measure the steady-state hydrostatic intracranial pressure, it does not allow accurate measurement of the mean and pulsatile intracranial pressure, nor does it allow recording or hydrodynamic exploration of the signal.

[0010] On the other hand, more complex solutions include the use of piezoelectric sensors, which are capable of converting the liquid pressure into an electrical signal that must be amplified, digitized and processed with specific software. In practice, the sensing cell of the piezoelectric sensor is placed in direct contact with the CSF in order to measure its pressure using a hydrostatic or hydrodynamic approach.

[0011] In general, the CSF pressure measured by the sensing cell of a piezoelectric sensor is the sum of two forces per unit area: the pressure transmitted by the fluid and the pressure related to the motion of the mass of the fluid. Specifically, this mass is subjected to acceleration, either directly or by gravity. In fact, the piezoelectric sensor not only measures the pressure transmitted by the CSF, but also the acceleration of the liquid mass, which constitutes an inappropriate result and impairs the quality of the CSF pressure signal. Thus, the liquid pressure sensor is subject to all physical accelerations related to the medical environment in which the pressure measurement is performed. For example, vibrations of the medical equipment generate artifacts in the signal measured by the pressure sensor, as do shocks to the patient's bed. This vibration and other artifacts disrupt sensitive measurements such as the pulsatility of the intracranial pressure.

[0012] A system called "ICM+®" was developed by the University of Cambridge (UK) to allow intracranial multimodal monitoring. The software allows, among other things, CSF pressure measurements to perform static and dynamic analysis of intracranial pressure. The ICM+ system allows for reliable measurement of intracranial pressure at the patient's bedside. However, the software was designed for clinical research and is not easily accessible to most clinicians at the patient's bedside. In particular, no specific sensors have been designed for the "ICM+®" system.

[0013] Patent document 1 discloses a system for measuring changes in CSF pressure while allowing the drainage of CSF. This system allows the CSF pressure to be measured remotely, regardless of whether the puncture site is lumbar or intracranial. In this document, a pressure sensor converts the measured liquid pressure into an electrical signal. For this, the sensing cell of the pressure sensor is placed in a measurement chamber that is first evacuated of air and filled by washing with physiological serum. The CSF is then in fluid communication with the measurement chamber filled with physiological serum. On the one hand, the sensing cell measures the acceleration of the mass of physiological liquid with the inappropriate consequence of the physical acceleration that affects the pressure sensor, and on the other hand, this system does not allow the measurement of the pulsatility of the CSF pressure using a hydrodynamic approach.

[0014] US Pat. No. 5,399,633 describes another CSF drainage system that draws liquid directly from the patient's skull. A tube drains the collected CSF at a first lower end of a vertical valve in which a float is placed. The valve has a second upper end connected to a guide tube equipped with a pressure sensor. The guide tube is filled with gas. The float thus constitutes a membrane that separates the CSF below the float from the gas above the float and in the guide tube. The purpose of this system is to prevent liquid from coming into contact with the pressure sensor, thus making it possible to eliminate the need to sterilize the pressure sensor. This system therefore measures the CSF pressure via the gas in the guide tube. When the CSF pressure exceeds a certain threshold, a solenoid valve causes the CSF to be drained into a collection bag. However, monitoring of CSF pressure changes is unreliable. In particular, the changes in CSF pressure are measured by measuring the gas pressure in the guide tube, even though the gas is not in direct contact with the CSF. Furthermore, the float separating the gas and CSF not only dampens changes in CSF pressure, but also can perturb measurements due to accelerations experienced by the float if the tubing or valves move. [Prior art documents] [Patent documents]

[0015] [Non-Patent Document 1] Lenfeldt N,Koskinen LO,Bergenheim AT,Malm J,Eklund A.CSF pressure assessed by lumbar puncture agrees with intracranial pressure.Neurology.2007;vol.68,No 2,pp.155-158 [Non-Patent Document 2] Czosnyka M,Pickard JD.Monitoring and interpretation of intracranial pressure.Journal of Neurology,Neurosurgery & Psychiatry,2004,vol.75,No 6,pp.813--821 [Patent Document 1] U.S. Pat. No. 4,858,619 [Patent Document 2] Chinese Patent No. 105641758 Summary of the Invention [Problem to be solved by the invention]

[0016] The present invention aims to overcome all or some of the above mentioned disadvantages.

[0017] The present invention aims to provide a reliable and cost-effective technical solution for measuring at least one physiological parameter, such as CSF pressure, by lumbar puncture.

[0018] The present invention aims to reliably measure at least one physiological parameter at the patient's bedside.

[0019] In particular, the present invention aims to provide a technical solution for reliably measuring changes in CSF pressure over time.

[0020] The present invention is particularly directed to reliably measuring steady-state or pulsatile CSF pressure. [Means for solving the problem]

[0021] To this end, a first aspect of the invention relates to a measurement device for measuring at least one physiological parameter, the measurement device comprising a housing extending longitudinally between a first end and a second end opposite the first end, the housing comprising three parts: a measurement chamber disposed within said housing, said measurement chamber having an internal volume filled with a gas. a sensing cell enabling at least a first physiological parameter to be measured, said sensing cell being arranged in contact with said gas contained in said internal volume of said measurement chamber. an inlet for introducing a physiological liquid of a patient into the measurement chamber, said inlet being positioned such that said physiological liquid is in contact with said gas and such that a volume of said gas is interposed between said sensing cell and said physiological liquid of the patient.

[0022] According to the invention, the measurement chamber is capable of generating two interfaces: a first interface between the gas contained in the internal volume and the physiological liquid of the patient entering through the inlet, and a second interface between the gas in the measurement chamber and the sensing cell.

[0023] The measuring device according to the invention allows reliable measurement of liquid physiological parameters, such as CSF pressure. Indeed, in a fluid, due to Pascal's principle, a pressure change at a point is perfectly transmitted to all points of this fluid. Thus, the pressure change of the physiological fluid is transmitted to the sensing cell via a gas bubble, which corresponds to an "oil-air pressure transmission interface" or a liquid / gas interface due to the action of the liquid and the gas.

[0024] Additionally, the device of the present invention can reduce nuisance results due to vibration of the sensor.

[0025] In an embodiment of the first aspect of the invention, the internal volume of the measurement chamber is not zero and must be equal to or less than 1 ml, in particular the internal volume must be less than 1 ml, preferably less than 0.7 ml. Thus, the internal volume of the measurement chamber can contain a gas volume that allows a controllable damping of the pulsatility of the pressure of the physiological liquid, in order to obtain a pulsatility damping that is acceptable in clinical practice.

[0026] In an embodiment, the gas contained in the internal volume of the measurement chamber may correspond to atmospheric air, in particular because the manufacturing method of the measurement device, e.g. plastic injection molding, is not performed under vacuum, so that the measurement chamber naturally fills with atmospheric air.

[0027] In an embodiment of the first aspect of the present invention, the internal volume of the measurement chamber may be between 0.2ml and 0.5ml.

[0028] In an embodiment of the first aspect of the present invention, the sensing cell may be a piezoelectric cell of a pressure sensor, and the liquid / gas interface serves to dampen the physical acceleration experienced by the pressure sensor, thereby improving the reliability of the measurement.

[0029] In an embodiment of the first aspect of the invention, the housing may include a sealing membrane interposed between the sensing cell and the internal volume of the measurement chamber, the sealing membrane protecting the sensing cell. The sensing cell of the sensor may be, for example, a piezoelectric cell of a pressure sensor. The sealing membrane may isolate the CSF, and more generally the patient's biological tissue, from highly toxic electronic components that the piezoelectric sensing cell may contain.

[0030] In an embodiment of the first aspect of the invention, the internal volume of the measurement chamber may be cylindrical. The cylindrical shape allows for the formation of a liquid / gas interface when the physiological liquid enters the measurement chamber.

[0031] In an embodiment of the first aspect of the invention, the measurement device may include a connector arranged at the inlet of the housing, which connector hermetically connects the measurement chamber to a connection device for connecting to a physiological fluid of the patient. The physiological fluid connection device may be a lumbar puncture needle. Preferably, the lumbar puncture needle is directly connected to the connector of the measurement device.

[0032] In an embodiment of the first aspect of the invention, the inlet may be openable and closable to control the flow of physiological fluid into the measurement chamber.

[0033] In an embodiment of the first aspect of the invention, the measurement device may comprise a transmitting means for transmitting the measurement value of the first physiological parameter to a remote digital terminal.

[0034] In an embodiment of the first aspect of the present invention, the sensing cell may be located at a first end of the housing and the inlet may be located at a second end of the housing.

[0035] A second aspect of the invention relates to a measuring method for measuring at least one physiological parameter of a patient, said method comprising, according to the invention: a connecting step of connecting a measuring chamber, filled with gas and including a sensing cell making it possible to measure at least one physiological parameter, to the physiological fluid of the patient. - creating a first interface between the gas in the measurement chamber and the physiological liquid from the patient, the gas being interposed between the physiological liquid and the sensing cell to form a second interface between the gas and the sensing cell. - measuring at least a first physiological parameter, the measurement being performed by the sensing cell through the gas interposed between the physiological liquid and the sensing cell;

[0036] The measurement method follows the same technical principle as the measurement device: a liquid / gas interface can be created in the measurement chamber, where the physiological liquid comes into contact with the gas. The physiological liquid then transmits the CSF pressure to the gas, which then transmits this pressure to the sensing cell of the measurement sensor.

[0037] In an embodiment of the second aspect of the present invention, the gas volume interposed between the sensing cell and the patient's physiological liquid may be non-zero and may be equal to or less than 1 ml, in particular the gas volume may be less than 1 ml, preferably the gas volume may be less than 0.7 ml. This gas volume interposed between the sensing cell and the patient's physiological liquid may control the attenuation of the pulsatility of the pressure of the physiological liquid, in order to obtain a pulsatility attenuation acceptable in clinical practice.

[0038] In an embodiment of the second aspect of the invention, the measuring chamber may be connected to a collection device for physiological fluid, which may consist of cerebrospinal fluid of the patient. In particular, the connection device may consist of a lumbar puncture needle. Preferably, the lumbar puncture needle is directly connected to the measuring chamber.

[0039] In an embodiment of the second aspect of the present invention, the first physiological parameter may correspond to a steady state or dynamic pressure of a physiological fluid of the patient.

[0040] In an embodiment of the second aspect of the present invention, the measurement method may comprise a determining step of determining at least a second physiological parameter through measurement of the first physiological parameter. [Brief description of the drawings]

[0041] Further characteristics and advantages of the invention will appear on reading the following description, which is purely exemplary and which must be read in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 shows diagrammatically a longitudinal section of a measuring device according to the invention, which is connected to a lumbar puncture needle. [Diagram 2] FIG. 2 shows a schematic representation of the measuring device of FIG. 1 and its medico-technical interactions. [Diagram 3] FIG. 3 shows diagrammatically a measuring device according to the invention. [Figure 4] FIG. 4 is a flow chart that illustrates the measurement method according to the present invention. [Diagram 5]Figure 5 shows a schematic of the experimental setup for carrying out a comparative study of hydrostatic pressure measurements using liquid interface sensors and liquid / air interface sensors. [Figure 6] FIG. 6 shows a graph of the recorded hydrostatic pressure signals during experiment 1 measured by the liquid interface sensor and the liquid / air interface sensor based on the apparatus of FIG. [Figure 7] FIG. 7 is an enlarged view of the trace of FIG. [Figure 8] FIG. 8 is a graph recording the hydrostatic pressure signal measured in experiment 2. The signal was measured by a liquid interface sensor and a liquid / air interface sensor based on the apparatus of FIG. [Figure 9] FIG. 9 is an enlarged view of cycle C8 of the recording graph of FIG. [Figure 10] FIG. 10 shows a Bland-Altman plot constructed from the data of experiment 2. [Figure 11] FIG. 11 is a graph recording the pressure signal measured in experiment 3 where the pressure was pulsatile, the signal being measured by the liquid interface sensor and the liquid / air interface sensor based on the apparatus of FIG. [Figure 12] FIG. 12 is an enlarged view of cycle C1 of the recording graph of FIG. [Figure 13] FIG. 13 is an enlarged view of cycle C7 of the recording graph of FIG. [Figure 14] FIG. 14 is a graph showing the results of experiment 4, performed using the apparatus of FIG. 5, showing the change in pressure pulsatility measured by the liquid / air interface sensor and the liquid interface sensor as a function of the amount of air at the liquid / air interface. [Figure 15] FIG. 15 shows the constitutive relationship of the damping of pressure pulsatility measured by a liquid / air interface sensor as a function of the amount of air at the liquid / air interface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] 1 to 3, the present invention relates to a measurement device 100 for measuring at least one physiological parameter. More specifically, the measurement device 100 is configured to measure the pressure of a physiological fluid taken from within a patient's body. For example, the present invention relates to a measurement device 100 for measuring CSF pressure, which is an indirect measure of the patient's intracranial pressure.

[0043] As shown in Figures 1 to 3, the measurement device 100 comprises a housing 101. The housing 101 defines an outer casing of the measurement device 100. The housing 101 extends longitudinally between a first end 102 and a second end 103 opposite the first end 102. The housing 101 comprises a measurement chamber 104. The measurement chamber 104 extends into the interior of the housing 101. In this example, the measurement chamber 104 extends between the first end 102 and the second end 103 of the housing 101. The measurement chamber 104 is filled by default with a gas G. For example, the measurement chamber 104 may be filled with air. However, the measurement chamber 104 can also be filled with other gases.

[0044] In this example, the volume of the measurement chamber 104 is not zero, but is equal to or less than 1 ml. In particular, the internal volume of the measurement chamber 104 may be less than 1 ml. Preferably, the internal volume of the measurement chamber 104 is less than 0.7 ml.

[0045] According to an embodiment of the present invention, the internal volume of the measurement chamber 104 may be between 0.2 ml and 0.5 ml. However, the internal volume may also be between 0.3 ml and 0.4 ml.

[0046] In this case, the internal volume of the measurement chamber 104 is cylindrical. The internal volume is bounded by the inner wall of the housing 101.

[0047] 1 to 3, the housing 101 includes a sensing cell 105 that allows for measuring at least one physiological parameter. The sensing cell 105 is arranged to be in contact with a gas G contained in an internal volume of a measurement chamber 104. In this example, the sensing cell 105 is arranged at a first end 102 of the housing 101. In particular, the sensing cell 105 may be of the piezoelectric type. A piezoelectric sensing cell is capable of converting a pressure measurement into an electrical signal.

[0048] 1 to 3, the housing 101 includes a sealing membrane 106. The sealing membrane 106 is interposed between the sensing cell 105 and the gas G contained in the internal volume of the measurement chamber 104. In this example, the sealing membrane 106 is disposed at the first end 102 of the housing 101. The sealing membrane 106 isolates the sensing cell 105. The sealing membrane 106 improves the safety of the device and isolates the electronic components from the internal volume of the measurement chamber 104. The sealing membrane may be made of an airtight and waterproof medical grade polymer, such as silicone or polyurethane.

[0049] In the example of Figs. 1 to 3, the housing 101 comprises an inlet 107 for taking in the physiological liquid LP of the patient. Preferably, the housing 101 has only one inlet 107, because, unlike the prior art, it is not intended to evacuate the gas present in the measurement chamber 104. In clinical practice, contact between air and the physiological liquid is usually avoided, and in fact, injecting a small amount of air into the blood system carries the risk of embolism with serious consequences. However, injecting the same small amount of air into the nervous system has no effect. Thus, the single inlet 107 allows to control the formation of a liquid / gas interface in the measurement chamber 104. The inlet 107 is arranged so that the physiological liquid LP comes into contact with the gas G, which is then interposed between the sensing cell 105 and the physiological liquid LP of the patient. For this reason, the inlet 107 may be arranged at the end of the housing 101 opposite the sensing cell 105. 1 to 3, the inlet 107 is located at the second end 103 of the housing 101 and the sensing cell 105 is located at the first end 102 of the housing 101. In this case, the inlet 107 is constituted by an opening in the housing 101, the outline of the inlet 107 being shown by a dotted line in Figures 1 to 3. However, other configurations and other housing shapes are also contemplated so that the gas G can be interposed between the physiological liquid LP and the sensing cell 105.

[0050] 1 to 3, the measurement device 100 includes a connector 108. The connector 108 is disposed at the inlet 107 of the housing 101. In this example, the connector 108 tightly connects the measurement chamber 104 to a connection device 200 for the patient's physiological fluid LP. In this example, the connector 108 is in the form of a male cone-shaped portion configured to connect with a female cone-shaped end 109 of the connection device 200.

[0051] 1 and 3, the female cone end 109 of the connection device 200 connects directly to the cone connector 108 of the housing 101. As shown in FIGS.

[0052] Preferably, the connection device 200 comprises a lumbar puncture needle 201. In this configuration, the measurement device 100 is directly connected to the lumbar puncture needle 201. This makes the measurement device 100 easier for the clinician to use.

[0053] Alternatively, the connector 108 may be connected to the cone end 109 of the lumbar puncture needle 201 via a three-way stopcock.

[0054] As an alternative option (not shown) for use with the present invention, the connector 108 may be connected to a tube interposed between the measurement device 100 and the lumbar puncture needle 201 .

[0055] A lumbar puncture consists of inserting a needle through the patient's skin into the lumbar pouch to access the CSF. Typically, a lumbar puncture is performed to obtain CSF for biochemical or biological analysis. Thus, a lumbar puncture is commonly used in cases where meningitis, inflammatory or neurodegenerative diseases are suspected.

[0056] In addition to providing an access to the nervous system for biochemical analysis, lumbar puncture also provides an access to the nervous system for biomechanical analysis through the measurement of CSF pressure. Lumbar puncture is currently the least traumatic technique for accessing cerebrospinal fluid. Specifically, in the context of the present invention, lumbar puncture constitutes the preferred means for accessing CSF, which constitutes the physiological liquid LP in the sense of the present invention. And, through the pressure of CSF, it is possible to measure intracranial pressure. However, the measuring device 100 can also function with other CSF access methods, such as intraventricular drains.

[0057] According to an embodiment of the present invention, the inlet 107 may be openable and closable. To this end, the inlet 107 may be connected via a connector 108 to at least a two-way stopcock.

[0058] As shown in Figures 1 to 3, the measurement chamber 104 according to the invention is capable of generating a first interface between the gas G contained in the internal volume of the measurement chamber 104 and the patient's physiological liquid LP entering the measurement chamber 104 through the inlet 107. When the physiological liquid LP enters the measurement chamber 104, the gas G is interposed between the sensing cell 105 and the patient's physiological liquid LP, generating a second interface between the gas G and the sensing cell 105. The liquid / gas interface and the gas / sensing cell 105 interface are formed by the shape of the measurement chamber 104. However, the positioning of the sensing cell 105 relative to the inlet 107 may also contribute to the generation of said interfaces. In the example shown in Figures 1 to 3, the liquid / gas interface has a half-moon shape. This is partly due to the cylindrical shape of the measurement chamber 104. However, the physicochemical properties of the gas G and the physiological liquid LP also contribute to the establishment of a particular shape of the meniscus at the measurement interface.

[0059] As shown in Figures 1 to 3, the measuring device 100 includes a transmitting means 110. The transmitting means 110 transmits the measured values ​​of the physiological parameters to a digital terminal 300 remote from the measuring device 100.

[0060] 1 and 2, the transmitting means 110 are arranged in an electronic compartment 111 arranged in the extension of the first end 102 of the housing 101. The electronic compartment 111 contains an electronic board 112 connected on the one hand to the transmitting means 110 and on the other hand to the sensing cell 105. The data measured by the sensing cell 105 are transmitted to the transmitting means 110, which relays them to a remote digital terminal 300. In the case of a piezoelectric sensing cell of the pressure sensor, the measured data are transmitted to the transmitting means in the form of an electrical signal.

[0061] In the examples of Figures 1 to 3, the transmitting means 110 is wireless. For example, the transmitting means 110 may be a transceiver of electromagnetic waves such as radio waves, Bluetooth, WIFI, etc. Under certain conditions, the transmitting means 110 may be wired.

[0062] The electronics compartment 111 may also contain a battery that powers the electronics board 112 and the electronic components connected thereto. The battery may be rechargeable or disposable.

[0063] 3, the electronic compartment 111 is provided separate from the housing 101. In this configuration, the measurement device 100 includes an external electrical cable 113 that detachably connects the sensing cell 105 to the electronic board 112. For hygiene reasons, the housing 101 is a disposable housing, so having the electronic compartment 111 separate from the housing 101 allows the electronic compartment 111 to be used for multiple patients.

[0064] The digital terminal 300 may be a smartphone, tablet, computer, or other device capable of receiving data and analyzing the data using algorithms stored in memory or on a remote server accessible via a telecommunications network.

[0065] As shown in FIG. 4, the present invention also relates to a measurement method 400 for measuring at least one physiological parameter of a patient.

[0066] The measuring method 400 includes a connecting step 401 for connecting a measuring chamber to the physiological fluid of the patient. For example, the measuring chamber may be connected to the physiological fluid of the patient via a connecting device 200. The connecting device 200 may include a lumbar puncture needle, which allows access to the cerebrospinal fluid for measuring the intracranial pressure.

[0067] In the example shown in FIG. 2, the lumbar puncture needle 201 connected to the patient may also be connected to tubing using a three-way stopcock for injection to perform dynamic testing.

[0068] According to the invention, during the connecting step 401, the measurement chamber is filled by default with gas G and contains a sensing cell that allows for measuring at least one physiological parameter. For example, the housing contains a piezoelectric sensing cell to measure CSF pressure.

[0069] As shown in Fig. 4, the measurement method 400 includes a generating step 402 of generating a first interface between a gas in a measurement chamber and a physiological liquid from a patient. As shown in Figs. 1 to 3, the gas is interposed between the physiological liquid of the patient and a sensing cell, forming a second interface between the gas and the sensing cell. For this purpose, the measurement chamber may be directly fluidly connected to a connection device 200 consisting of a lumbar puncture needle 201.

[0070] The measurement chamber may be connected to the lumbar puncture needle 201 and tubing to perform dynamic testing.

[0071] In this example, the gas interposed between the sensing cell 105 and the physiological liquid of the patient has a volume that is not zero but is equal to or less than 1 ml. Also, the volume of the gas interposed between the physiological liquid and the sensing cell may be less than 1 ml. In particular, the volume of the gas interposed between the physiological liquid and the sensing cell 105 may be less than 0.7 ml.

[0072] According to an embodiment of the present invention, the volume of gas interposed between the physiological liquid and the sensing cell 105 may be between 0.2 ml and 0.5 ml, although the volume of gas interposed between the physiological liquid and the sensing cell 105 may be between 0.3 ml and 0.4 ml.

[0073] Thus, the sensing cell 105 performs measurements via an oil-air pressure transmission interface, which has the advantage of dampening physical accelerations, such as patient movement or vibrations induced by the medical environment (e.g., monitoring equipment), induced at the sensing cell 105 while still providing a more reliable measurement of CSF pressure and pulsatility.

[0074] As shown in Fig. 4, the measurement method 400 includes a measuring step 403 of measuring at least a first physiological parameter. The measurement of the first physiological parameter is performed using a sensing cell while a gas G contained in a measurement chamber is interposed between the physiological liquid and the sensing cell. For example, CSF pressure is a physiological parameter measurable by the measurement method 400. In this case, the CSF pressure may constitute the first physiological parameter. A piezoelectric sensing cell may be used to measure the steady-state or pulsatile pressure of the CSF.

[0075] In the example of FIG. 4, the measurement method 400 may include a determining step 404 of determining at least a second physiological parameter through the measurement of the first physiological parameter.

[0076] According to a first example, a mean value of the patient's intracranial pressure can be determined, said mean value of the intracranial pressure then constituting the second physiological parameter.

[0077] According to a second example, the pulsatility of the patient's intracranial pressure can be determined, the value of the intracranial pulsatility then constituting a third physiological parameter.

[0078] Within the framework of the fluid dynamic approach, the method of the invention allows the determination of other physiological parameters such as the frequency of the respiratory cycle, the compliance of the brain, the resistance to CSF ​​flow, etc.

[0079] 3 and 4, the measurement method 400 may include a transmitting step 405 of transmitting the data measured by the sensing cell to a digital terminal 300 remote from the sensing cell. The transmitting step 405 may be performed in an analog manner by Bluetooth or WIFI type protocols or by a wired connection.

[0080] Upon receiving the measurement data, the digital terminal 300 may execute step 404 to process the signals to extract at least one physiological parameter. The patient's intracranial pressure is a parameter that can be determined directly by measuring the CSF pressure.

[0081] According to the invention, the measurement device 100 is particularly suitable for carrying out the measurement method 400 .

[0082] The measuring device 100 and the measuring method 400 allow reliable and accurate measurement of CSF pressure in both hydrostatic and hydrodynamic approaches. The hydrostatic approach consists in measuring the steady or pulsatile pressure of the CSF secondary to the periodic oscillations of the heart and breath. The hydrodynamic approach consists in applying a known stress to the intracranial fluid system, called a perfusion test, and analyzing the response of the system to this stress.

[0083] To assess the hydrostatic component of the CSF pressure, the measuring chamber 104 is connected to a connection device 200 that is fluidly connected to the nervous system, for example by lumbar puncture. Changes in the electrical signal measured by the sensing cell 105 reflect changes in the CSF pressure.

[0084] To explore the hydrodynamic components of CSF pressure, the CSF is fluidically stressed by injecting physiological serum at a constant flow rate through an inlet port at the lumbar puncture site. This perfusion test is performed through an inlet port created in parallel with a first port to which a connection device 200 is connected, which places the measurement device 100 in fluid contact with the CSF. [Experimental Results]

[0085] In order to address the technical problems stated in this document, the inventors performed a comparative experimental study between pressure measurements obtained by a sensor with a liquid / sensing cell interface, called "fluid sensor" 501, and a sensor with two liquid / gas / sensing cell interfaces, called "oil-pneumatic transmission sensor" 502. The study was performed in the same experimental setup 500 using physiological serum S instead of the patient's physiological fluid.

[0086] FIG. 5 shows a schematic of the experimental setup 500. The two sensors 501, 502 are of the piezoelectric type for invasive blood pressure measurement, of the brand "Transpac®" sold by the company ICUMED. The pressure measuring device includes a measuring chamber 503 with an internal volume of 0.2 ml. In addition, the measuring device includes a fluid inlet 504 connected to a tube 600 filled with physiological serum S. The fluid inlet 504 is equipped with a three-way stopcock 504, which controls the connection or disconnection of the sensor to the physiological serum S. The measuring device used includes a sensing cell of a piezoelectric sensor 505 in the end wall opposite the inlet 504. In the side wall of the measuring chamber 503 near the piezoelectric sensor 505, there is a wash opening 506, the opening and closing of which is controlled by a manual valve or stopcock. The piezoelectric sensor is designed with a sensitivity of ±1% and a linearity of 1%. Finally, the piezoelectric sensor is designed to measure pressure changes between -20 mmHg and 300 mmHg.

[0087] In the experimental setup 500 shown in Fig. 5, two sensors 501 and 502 are attached to a support and held horizontally on the same plane. In this case, the two sensors 501, 502 are connected in parallel to a tube 600. The tube 600 includes a three-way stopcock 601 at each junction between the tube 600 and a connecting tube 602 that connects the sensors 501 and 502.

[0088] The sensing cells of each piezoelectric sensor 501 and 502 are independently connected by electrical cables 507 to an amplifier, which is then connected to a transducer and then recorded on a computer using "ICM+" software.

[0089] In the experimental setup 500 of Fig. 5, the washing opening 506 of the oil-pneumatic transmission sensor 502 is connected to a syringe 508 containing air. The syringe 508 is graduated so that the amount of air in the measurement chamber 503, i.e., the amount of air interposed between the sensing cell of the piezoelectric sensor 505 and the physiological serum S, can be controlled.

[0090] The experimental setup 500 also includes a graduated column 603 that is held vertically. The graduated column 603 includes a fluid connection at its lower end. The graduated column 603 allows the inventors to visualize the pressure applied to the sensors 501, 502 by measuring the water column in the graduated column 603. For this purpose, the sensors 501, 502 are positioned so that their piezoelectric sensing cells 505 are located in a horizontal plane P that passes through the zero level defined by the graduated column. In the example of FIG. 5, the graduated column 603 is placed at one end of a first branch of a tube 600. A second branch of the tube 600 is mounted in parallel with the first branch and supplies the sensors 501, 502 via a connecting stopcock 601 placed at each junction with the connecting tube 602.

[0091] The tube 600 filled with physiological serum S is connected to an electric syringe pump 604. The syringe pump 604 is configured to apply static pressures between -20 mmHg and 50 mmHg in steps. These values ​​correspond to CSF ​​pressures that can be measured in patients under both physiological and pathological conditions. The electric syringe pump 604 used in this experiment is a FRESENIUS® syringe pump.

[0092] A connecting stopcock 601 allows an oscillator 605 to be connected to the tube 600 as required in order to generate dynamic wave pressure at 1 Hz and with an adjustable amplitude between 0.1 mmHg and 10 mmHg. These amplitude values ​​correspond to the intracranial pressure of the patient in both physiological and pathological conditions. The oscillating pressure oscillator 605 used in this experiment is of the RADOMEDIC® type.

[0093] It should be noted that upon delivery, sensors 501 and 502 naturally contain air within their measurement chambers 503 .

[0094] For the fluid sensor 501, air washing is performed by washing air through the opening 506 of the measurement chamber 503 and filling it with physiological serum. Thus, the sensing cell is in direct contact with the fluid in the measurement chamber. This air washing protocol is the operating procedure usually recommended for measuring fluid pressure with this type of sensor in clinical practice, especially for invasive measurement of arterial or venous blood pressure.

[0095] Once the fluid sensor 501 is cleared of air, the fluid sensor 501 is fluidly connected with the physiological serum S.

[0096] For the hydro-pneumatic sensor 502, no air washing is performed. Since the measurement chamber 503 has a volume of 0.2 ml, it contains 0.2 ml of air. This volume of air is therefore interposed between the sensing cell 505 and the inlet 504. The hydro-pneumatic sensor is then connected to the physiological serum by a connection 602. A controlled volume of air is thus added between the piezoelectric sensor 505 and the physiological serum S. According to the invention, the inventors create in the measurement chamber a liquid / gas measurement interface that corresponds to the principle of hydro-pneumatic transmission.

[0097] Both the fluid sensor 501 and the hydro-pneumatic transmission sensor 502 are fluidly connected to a graduated column 603, an electric syringe pump 604, and a dynamic pressure oscillator 605 via physiological serum S. [Experiment 1]

[0098] Experiment 1 consisted of simultaneously recording, using the "ICM+" software, the pressure measurements obtained by the fluid sensor 501 and the pressure measurements obtained by the oil-pneumatic transmission sensor 502. To be sure, the air volume of the oil-pneumatic transmission sensor 502 is the internal volume of the measurement chamber 503, i.e. 0.2 ml.

[0099] The measurements of the steady hydrostatic pressure were taken at 100 Hz with a recording time of 5 minutes. The hydrostatic pressure of the two sensors 501 and 502 could be gradually increased by injecting physiological serum. Figure 6 corresponds to the recording of this experiment. In this figure, the grey signal corresponds to the fluid sensor 501 and the black signal corresponds to the oil-pneumatic transmission sensor 502.

[0100] In experiment 1, the electric syringe pump 604 is placed on the table where the experimental apparatus 500 is installed. In the baseline state, the values ​​measured by the fluid sensor 501 and the hydraulic-pneumatic transmission sensor 502 are identical. In FIG. 6, two lines representing the two sensors are overlapped. Arrow D indicates that the electric syringe pump 604 is switched on at 16:53:30. Once switched on, the pressure gradually increases from 0 mmHg to approximately 25 mmHg, and at the recording time of 16:56:18, the electric syringe pump 604 is stopped (arrow ST).

[0101] The electrical cables of sensors 501 and 502 were separately connected to a computer running the "ICM+" software, so that the inventors could study and compare the signals of the fluid sensor 501 and the hydraulic-pneumatic transmission sensor 502, as they would in subsequent experiments.

[0102] In the recording of FIG. 6, the inventors noticed that the signals of the two sensors 501, 502 overlap until the switch D of the electric syringe pump 604 is turned on. When the two signals overlap, only the black signal is visible. When the electric syringe pump is turned on at D, on the one hand, the hydrostatic pressure of the two signals rises along a similar curve, and on the other hand, the grey signal recorded by the fluid sensor 501 oscillates. FIG. 7 is an enlarged view of FIG. 6, and it can be seen that the signal of the oil-pneumatic transmission sensor 502 (black) also shows oscillations, but its amplitude is much smaller than that of the fluid sensor 501 (grey). As soon as the electric syringe pump 604 stops, the oscillations disappear. And the two signals of the fluid sensor 501 and the oil-pneumatic transmission sensor 502 can be superimposed.

[0103] This vibration was not induced by the pulse generator 607, which was off. This vibration appeared the moment the electric syringe pump 604 was switched on, and stopped the moment it was switched off. Therefore, the inventors concluded that the mechanical vibration of the electric syringe pump 604 placed on the table was transmitted to the fluid sensor 501, while the oil-pneumatic transmission sensor 502 damped this vibration. The density of air is 1.29 kg / m 3 whereas the density of a liquid like water is 1000 kg / m 3 Therefore, water has a density about 1000 times that of air. The 0.2 ml measuring chamber of the fluid sensor has a mass of about 0.2 g, whereas the 0.2 ml measuring chamber of the oil-pneumatic transmission sensor has a mass of only about 0.26 μg. During the acceleration of the fluid sensor induced by the vibration wave, the mass of water (about 0.2 g) in the measuring chamber generates a mechanical stress on the sensing cell 505, which leads to an inappropriate measurement result, whereas the low mass of air (about 0.26 μg) in the measuring chamber of the oil-pneumatic transmission sensor generates a very low mechanical stress on the sensing cell, thus damping the vibration wave.

[0104] This experiment shows that the hydro-pneumatic transmission sensor 502 dampens the physical acceleration transmitted to the measurement device during vibration. From a practical standpoint, this leads to improved accuracy of CSF pressure measurements.

[0105] During this experiment 1, we also compared the two sensors from an arithmetic point of view. The mean ± standard deviation of the absolute difference between the fluid sensor and the oil-pneumatic transmission sensor is 0.19 ± 0.21 mmHg, and the 95% confidence interval of the absolute difference is 0.41 mmHg. That is, 95% of the difference values ​​between the fluid sensor and the oil-pneumatic transmission sensor are within the range of ± 0.41 mmHg.

[0106] During experiments 2, 3, and 4, the motorized syringe pump 604 is moved away from the operator table so that the physical vibrations it generates are not directly transmitted to the sensor and produce inappropriate results. [Experiment 2]

[0107] In experiment 2, the experimental setup 500 is used to investigate the effect of the amount of air in the measurement chamber on the accuracy of the static pressure measurement of the oil-pneumatic transmission sensor.

[0108] The pressure of the physiological serum rises in successive static phases lasting about 10 seconds and then returns to zero. The signals of the fluid sensor 501 and the hydro-pneumatic transmission sensor 502 are recorded simultaneously at 100 Hz. Several pressure rise cycles are performed varying the amount of air in the measurement chamber of the hydro-pneumatic transmission sensor by adding air at room temperature and atmospheric pressure using a syringe 508. Figure 8 reproduces the recording with a recording time of 23 minutes. The first pressure rise cycle C0 is performed without the addition of air. The amount of air in the measurement chamber is therefore 0.2 ml. The two curves are completely superimposable. Then, 0.1 ml of air is added to the measurement chamber of the hydro-pneumatic transmission sensor. Cycle C1 corresponds to the various pressure steps with the addition of 0.1 ml of air. The two curves are completely superimposable. Cycles C0 to C8 are performed with increasing amounts of air as listed in table 1. [Table 1]

[0109] Looking at the curves for the various cycles, it can be seen that the signals measured by the fluid sensor 501 and the oil-pneumatic transmission sensor 502 overlap, regardless of the amount of air interposed between the sensing cell of the piezoelectric sensor 505 and the physiological serum S.

[0110] Figure 9 is a close-up of the graph of experimental cycle C8, i.e. a cycle in which a volume of 64 ml of air is interposed between the sensing cell of the piezoelectric sensor 505 and the physiological serum S. The volume of 64 ml of air is the maximum value in the context of experiment 2. Two signals can be distinguished in this graph: the fluid sensor 501 (grey) and the hydro-pneumatic transmission sensor 502 (black). The two signals completely overlap in most parts of the recording.

[0111] FIG. 10 is a Bland-Altman plot created from the experimental data of experiment 2. The X-axis of the graph corresponds to the average pressure measurement value, expressed in mmHg, of the fluid sensor 501 and the hydraulic-pneumatic transmission sensor 502. The Y-axis of the graph corresponds to the difference, expressed in mmHg, between the pressure measurement values, expressed in mmHg, of the fluid sensor 501 and the hydraulic-pneumatic transmission sensor 502. A linear regression is then performed.

[0112] The mean ± standard deviation of the absolute difference between the fluid sensor and the oil-pneumatic transmission sensor was 0.24 mmHg ± 0.17 mmHg, and the 95% confidence interval of the absolute difference was 0.33 mmHg. In other words, 95% of the difference values ​​between the fluid sensor and the oil-pneumatic transmission sensor were within the range of ± 0.33 mmHg.

[0113] In experiment 2, the pressure varied between values ​​of -10 and +30 mmHg, which correspond to values ​​found in clinical practice. 0.33 mmHg represents a maximum of approximately 1% of the pressure measurement. This measurement variation is acceptable in clinical practice. It should be noted that 1% also corresponds to the sensitivity of the sensor.

[0114] The scientific literature specifies that a blood pressure sensor is reliable if it provides a 5% error rate in measurements compared to the patient's actual blood pressure.

[0115] Experiment 2 shows that interposing an air volume between 0.2 ml and 64 ml in the measurement chamber of the oil-pneumatic transmission sensor 502 allows for more reliable measurement of pressure compared to the fluid sensor 501 . [Experiment 3]

[0116] In experiment 3, the experimental setup 500 is used to investigate the effect of the amount of air in the measurement chamber on the accuracy of the dynamic pressure measurement of the oil-pneumatic transmission sensor 502.

[0117] For this purpose, a dynamic wave pressure with a frequency of 1 Hz and an amplitude adjustable between 0.1 and 10 mmHg can be generated by an oscillator 605. The signals of the fluid sensor 501 and the hydraulic-pneumatic transmission sensor 502 are recorded simultaneously at 100 Hz. The recording time is 8 minutes.

[0118] In this experiment, the static pressure is stable and there are no fluctuations in the mean pressure. Only the dynamic pressure is modified by the oscillator 605 to observe the effect of the air volume on the pulsatility of the pressure measured by the oil-pneumatic transmission sensor 502. Several recordings are made at various pulsatility levels. For each pulsatility level, the air volume in the measurement chamber of the oil-pneumatic transmission sensor is gradually increased by adding air using the syringe 508. Figure 11 reproduces one of the recordings. The black line corresponds to the oil-pneumatic transmission sensor 502, which shows a decay with each cycle of increasing air volume. Conversely, the grey line, corresponding to the fluid sensor 501, does not change from cycle to cycle. Cycles C1 to C7 are performed with increasing air volumes as listed in Table 2. [Table 2]

[0119] Each time air is added to the measurement chamber, the pulsatility of the signal measured by the oil-pneumatic transmission sensor 502 decreases in proportion to the attenuation.

[0120] Figure 12 is a close-up of cycle C1. In this recording, it is not possible to distinguish the grey signal of the fluid sensor 501 superimposed on the black signal of the oil-pneumatic transfer sensor 502. With very small amounts of air, the attenuation of the signal is minimal.

[0121] Figure 13 is a close-up of cycle C7. At the beginning of this recording, the grey signal of the fluid sensor 501 shows the pulsatility generated by the waveform generator 605. As soon as the oil-pneumatic transmission sensor is connected with 20 ml of air, a decay of the grey signal of the fluid sensor (502) occurs instantly in sync with the black signal of the oil-pneumatic transmission sensor 502, since these two sensors are connected in parallel.

[0122] Experiment 3 shows that in the case of pulsatile pressure, the air volume of the oil-pneumatic transmission sensor 502 changes the dynamic measurement of pressure, thus affecting the accuracy of the measurement. [Experiment 4]

[0123] Experiment 4 aims to determine the amount of air in the measurement chamber of the oil-pneumatic transmission sensor 502 to provide an accurate and clinically acceptable measurement of pulsatility.

[0124] Experiment 4 consists of performing a series of eight operations at various pulsatility levels, gradually increasing the air volume of the hydropneumatic transmission sensor 502 by gradually adding air using the syringe 508 at room temperature and atmospheric pressure. The experiment is performed over a period of 10 minutes with a pulsatility of 1 Hz generated by the oscillator 605, whose oscillations are adjustable. Recordings are performed using the "ICM+" software and acquisition at 100 Hz. For each air volume (cycles C1 to C7), the pulsatility is calculated by a Fourier transformation, which measures the power of the fundamental harmonic in the frequency range of the signal pulse, rather than the difference between the maximum and minimum values. This gives a numerical value of the pulsatility for each air volume from 0.2 ml to 20 ml. A graphical representation characterizing the decay of the pulsatility is obtained using the XL software. An exponential regression analysis is performed, yielding its mathematical equation and the Pearson coefficient. For each oscillation condition, an exponential curve can be obtained, which describes the constitutive relationship of the decay of the pulsatility as a function of the air volume.

[0125] FIG. 14 shows eight experiments. Each point corresponds to a pulsatility value for different air volumes of the oil-pneumatic transmission sensor 502. Each curve corresponds to the change in the measured pulsatility value during different maneuvers. By transferring this data onto this one graph, the inventors were able to plot an exponential regression curve for each maneuver.

[0126] From the exponential regression equation of the data from the eight runs of experiment 4, the inventors calculated the theoretical variation in pulsatility attenuation (Δ pulsatility) induced by each addition of a basal volume of 0.1 ml of air to the oil-pneumatic transduction sensor 502. The results are expressed as a percentage of pulsatility attenuation per basal volume of air. These results allow the establishment of the mean and standard deviation of the pulsatility attenuation of the oil-pneumatic transduction sensor 502 as a function of the volume of air in the measurement chamber. The results are shown in Table 3 below. [Table 3]

[0127] As shown in Table 3, the average pulsatility attenuation of the oil-pneumatic transmission sensor 502 is less than 6.55% for air volumes less than 1 ml. Therefore, based on the accuracy of blood pressure measurement, the inventors concluded that the air volume of the oil-pneumatic transmission sensor should be less than 0.7 ml to ensure reliable measurement of CSF pulsatility (<5%).

[0128] The inventors have determined a constitutive relationship that allows determining the pulsatility decay rate {1}ΔP{2} as a function of air volume V (in ml). This law is expressed according to the following equation:

number

[0129] As shown in FIG. 15, this linear law allows defining an air volume strictly below 0.7 ml that allows measuring the pressure pulsatility of physiological fluids such as CSF using an oil-pneumatic transmission sensor with measurement variability of less than 5%.

[0130] According to these experimental results it is possible to determine the volume of the measurement chamber of the measurement device to be not zero but less than 1 ml. In the case of CSF, when establishing the liquid / gas interface, the possible physiological values ​​of the CSF pressure are likely to only slightly change the volume of gas initially contained in the measurement chamber at atmospheric pressure, which still has a non-zero volume of not more than 1 ml.

[0131] This observation applies in the context of the measurement method defined according to the invention to the volume of gas interposed between the CSF and the sensing cell.

[0132] These experimental results show that it is possible to measure the pressure of a biological liquid, either steady-state or pulsatile, through an oil-air pressure transmission interface. The present invention can therefore be used to measure other physiological parameters, such as bladder pressure, arterial pressure, venous pressure, interstitial tissue pressure in the context of compartment syndrome, intraocular pressure, upper airway pressure, gastrointestinal pressure, and other biological liquid pressures. For each of these applications, as described above, the biological liquid of interest can be contacted with the measurement device 100 and, depending on its nature, the biological liquid of interest can be sensed or extracted in a known manner. [Explanation of symbols]

[0133] 100 Measuring Equipment 101 Housing 102 First end 103 Second end 104 Measurement chamber 105 Sensing Cell 106 Sealing membrane 107 Entrance 108 Cone Connector 109 Female cone end 109 Cone End 110 Transmission means 111 Electronic Compartment 112 Electronic Board 113 External Electrical Cable 200 Connection Device 201 Lumbar puncture needle 300 Digital Terminals 500 Experimental Equipment 501 Fluid Sensor 502 Oil-pneumatic transmission sensor 503 Measurement chamber 504 Fluid Inlet 505 Piezoelectric Sensor 506 Cleaning opening 507 Electrical Cable 508 Syringe 600 tubes 601 Stopcock 602 Connection tube 603 Column 604 Electric Syringe Pump 604 Syringe Pump 605 Oscillator 607 Pulse Generator

Claims

1. A measurement device (100) for measuring at least one physiological parameter, the measurement device (100) comprising a housing (101) extending longitudinally between a first end (102) and a second end (103) opposite the first end (102); The housing (101) comprises: - a measuring chamber (104) arranged in said housing (101), said measuring chamber (104) having an internal volume filled with gas; a sensing cell (105) making it possible to measure at least a first physiological parameter, said sensing cell (105) being arranged in contact with said gas contained in said internal volume of said measuring chamber (104); an inlet (107) for introducing a physiological fluid of the patient into said measuring chamber (104); the inlet (107) is positioned such that the physiological liquid is in contact with the gas and the gas is interposed between the sensing cell (105) and the physiological liquid of the patient; The measuring chamber (104) allows for the creation of two interfaces: a first interface between the gas contained in the internal volume and the physiological liquid of the patient entering the measuring chamber (101) through the inlet (107), and a second interface between the gas in the measuring chamber (104) and the sensing cell (105).

2. 2. The measuring device (100) according to claim 1, wherein the internal volume of the measuring chamber (104) is not zero and is equal to or less than 1 ml, in particular the internal volume is less than 1 ml, preferably the internal volume is less than 0.7 ml.

3. The measuring device (100) of claim 1 or 2, wherein the internal volume of the measuring chamber (104) is between 0.2 ml and 0.5 ml.

4. The measuring device (100) according to any one of claims 1 to 3, wherein the sensing cell (105) is a piezoelectric cell of a pressure sensor.

5. The measuring device (100) of any one of claims 1 to 4, wherein the housing (101) includes a sealing membrane (106) interposed between the sensing cell (105) and the internal volume of the measuring chamber (104), the sealing membrane (106) protecting the sensing cell (105).

6. The measuring device (100) of any one of claims 1 to 5, wherein the internal volume of the measuring chamber (104) is cylindrical.

7. 7. The measuring device (100) of claim 1, further comprising a connector (108) arranged at the inlet (107) of the housing (101), the connector (108) hermetically connecting the measuring chamber (104) to a connection device (200) for connecting to the physiological fluid of the patient.

8. The measuring device (100) according to any one of claims 1 to 7, wherein the inlet (107) is openable and closable.

9. 9. The measuring device (100) according to any one of the preceding claims, comprising transmitting means (110) for transmitting the measured value of the first physiological parameter to a remote digital terminal.

10. The measurement device (100) of any one of claims 1 to 9, wherein the gas in the measurement chamber (104) consists of atmospheric air.

11. The measuring device (100) of any one of claims 1 to 10, wherein the sensing cell (105) is disposed at the first end (102) of the housing (101) and the inlet (107) is disposed at the second end (103) of the housing (101).

12. A measuring method (400) for measuring at least one physiological parameter of a patient, comprising: a connecting step (401) for connecting a measuring chamber connection device, filled with gas and including a sensing cell allowing to measure at least one physiological parameter, to the physiological fluid of the patient; - creating (402) a first interface between the gas in the measurement chamber and the physiological liquid from the patient, the gas being interposed between the physiological liquid and the sensing cell to form a second interface between the gas and the sensing cell; - a measuring step (403) of at least a first physiological parameter, the measurement being performed by the sensing cell through the gas interposed between the physiological liquid and the sensing cell.

13. 13. The measuring method (400) according to claim 12, wherein the volume of the gas interposed between the sensing cell and the physiological fluid of the patient is not zero and is equal to or less than 1 ml, in particular the volume of the gas is less than 1 ml, preferably the volume of the gas is less than 0.7 ml.

14. 14. The measuring method (400) according to claim 12 or 13, wherein the measuring chamber is connected to a connection device to the physiological fluid consisting of the cerebrospinal fluid of the patient.

15. 15. The method of claim 12, wherein the first physiological parameter corresponds to a pressure of the physiological fluid of the patient.

16. 16. The measuring method (400) according to any one of claims 12 to 15, comprising a determining step (404) of determining at least a second physiological parameter through the measurement of the first physiological parameter.

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