Medical gas distribution installation with gas network monitoring system

Abstract

Title of the Invention: Medical Gas Distribution System with Gas Network Monitoring System. The invention relates to a medical gas distribution system (100) comprising a gas distribution network (2, 3) arranged within a hospital, a gas source (1) comprising a gas tank (12) containing gas in liquid form, and a gas distribution network monitoring system (2, 3) comprising strain gauges (6, 6a, 6b) and a control unit (64). The gas tank (12) includes gas quantity measurement means (14) for measuring a residual quantity of gas in the gas tank (12) and a telemetry unit (13) for transmitting the residual gas quantity measurements to the control unit (64). Abstract Figure: Fig. 1

Description

Title of the invention: Medical gas distribution system with gas network monitoring system

[0001] The invention relates to a medical gas distribution installation comprising a non-invasive monitoring system for a gas distribution network in a hospital setting, enabling the provision of information relating to gas distribution within one or more departments of the hospital setting, in particular to alert in the event of localized overload, i.e. overpressure of a portion of the gas distribution network.

[0002] In hospital establishments, such as hospitals, clinics or others, it is necessary to bring medical gases, in particular medical-grade air and oxygen (O2), to the various points of use within these establishments, for example, resuscitation or emergency departments, operating rooms, etc., via gas pipes, lines or conduits, commonly called a "gas distribution network" or simply a "gas network", supplying hospital wall outlets, as described by EP-A-3922895.

[0003] Monitoring the distribution of medical gases in hospital establishments is essential to be able to know the specific consumption of the different departments and to manage restocking in order to avoid any disruption of gas supply which could compromise the safety of patients, in particular in the event of very high consumption, especially of oxygen (O2) such as during the Covid-19 pandemic, or in the event of high flow oxygenation or "HFOT" (for High Flow Oxygen Therapy).

[0004] Therefore, a gas network is usually designed and sized to guarantee a nominal gas pressure within a desired flow rate range, particularly according to the needs of each hospital department, which vary from one department to another. In general, the nominal operating pressure is in the range of 4 to 5 bar relative, according to ISO 7396-1.

[0005] However, it sometimes happens that in the event of a peak in consumption, the gas network cannot meet the demand for gas and therefore maintain the desired nominal pressure, which leads to a malfunction of medical devices connected to wall sockets since they are then "under-supplied" with gas.

[0006] To achieve this, EP1983251 proposes installing flowmeters at various locations in the medical gas network. However, this solution is not ideal because it requires interrupting, i.e., cutting, the network conduit to install the flowmeters, which can lead to the entry of dust or other pollutants. with risk of malfunction of downstream equipment, or of accident, (i.e. fire...) and requires operating an alternative gas supply to ensure continuity of patient treatment.

[0007] Therefore, a problem is to be able to operate an effective monitoring of a gas distribution network of a gas distribution installation arranged within a hospital establishment, including an existing network, without having to interrupt the network conduits and / or while ensuring continuity of gas supply to patients, including during the implementation of the solution, and this in such a way as to be able to measure the consumption of medical gases in different places of the gas network in question, without encountering the aforementioned disadvantages.

[0008] One solution of the invention relates to a medical gas distribution installation, in particular intended for a hospital, comprising: - a gas distribution network arranged within a hospital establishment, comprising a main gas pipe branching into several secondary gas pipes carrying gas, - a gas source comprising a gas reservoir containing gas in liquid form fluidly connected to the main gas conduit to supply it with gas from said gas reservoir, - and a monitoring system for said gas distribution network comprising: • strain gauges arranged on the main and / or secondary gas lines, and connected to a control unit to provide it with at least one resistivity (R) value for each strain gauge, and • the control unit configured to determine, from the resistivity value (R) provided by the strain gauges, at least one gas pressure reflecting the pressure of the gas exerted in the gas conduit on which the strain gauge in question is arranged, and, furthermore, to process said at least one gas pressure and deduce therefrom at least one gas flow rate circulating in the first secondary conduit and / or in the second secondary conduit.

[0009] Furthermore, in the medical gas distribution installation according to the invention: - the gas reservoir includes gas quantity measurement means configured to measure a residual quantity of gas in the gas reservoir and - a telemetry unit cooperates with the gas quantity measurement means to retrieve and transmit the residual gas quantity measurement(s) to the control unit.

[0010] Depending on the embodiment considered, the installation of the invention may include one or more of the following features: The control unit is configured to calculate a total volume (Vt) of gas, over a given period of time, from the determined gas flow rates having flowed through the first secondary conduit and / or the second secondary conduit, during said given period of time. the control unit is also configured to determine a volume of gas used (Vu) from the residual quantity of gas measurements taken by the gas quantity measuring means during said given period of time. The control unit is also configured to determine a volume ratio Vu / Vt from the total volume of gas (Vt) and the volume of gas used (Vu), and to compare the volume ratio Vu / Vt to a given threshold value (Vs). The control unit is further configured to use the volume ratio Vu / Vt to correct the gas flow rate(s) determined from the gas pressures within the first secondary conduit and / or the second secondary conduit, when the control unit determines that the volume ratio Vu / Vt is greater than the given threshold value (Vs), i.e. Vu / Vt > Vs. the given threshold value (Vs) is approximately 10%. the gas tank contains oxygen in liquid form (LOX). a pressure regulating device is arranged on the main gas line, the main gas line branching into several secondary gas lines, downstream of said pressure regulating device. Each strain gauge includes a deformable resistive track configured to deform proportionally to the gas pressure exerted in the gas conduit on which the strain gauge is arranged. The control unit is configured to determine the resistivity (R) of each strain gauge from the deformation of the resistive track of the strain gauge in question and a reference resistivity value (Ro). The control unit is configured to determine the gas pressure from the resistivity (R) of each strain gauge, each determined gas pressure reflecting the gas pressure exerted in the gas conduit on which the strain gauge in question is arranged. The strain gauges are arranged downstream of the pressure regulating device, on the main and / or secondary gas lines. The control unit cooperates with a telecommunications module. The control unit and the telecommunications module are configured to ensure data transmission via said telecommunications module. from the control unit to at least one remote data processing platform, preferably said data includes at least one gas pressure determined by the control unit.

[0011] According to various embodiments, the installation of the invention may further comprise one or more of the following features: - the gas distribution network includes gas pipes arranged in the hospital establishment, in particular on the walls of the hospital establishment, i.e. walls, partitions or the like. - the gas pipes have a diameter between 10 and 50 mm, preferably around 15 mm. - the gas pipes are made of copper alloy. - the gas source includes a storage tank or similar containing oxygen in liquid form surmounted by oxygen in gaseous form, i.e. a sky of gaseous oxygen. - the pressure regulating device is configured to control the pressure and ensure a stable pressure between 3 and 7 bar relative, preferably about 4 and 5 bar relative, advantageously equal to about 4 bar. - strain gauges include a reference gauge and one or more additional or secondary gauges. - Each additional strain gauge is paired with the reference strain gauge. - the strain gauges are fixed to / on the external peripheral surface of the gas pipes. - each control unit includes at least one (micro)processor, in particular a microcontroller. - the (microprocessor or microcontroller of each control unit is arranged on (at least) one electronic board. - the electronic board is arranged in the control unit. - each strain gauge comprises a deformable resistive track arranged on a support including fastening means allowing attachment to the external peripheral wall of a gas duct. - each strain gauge includes a resistive track arranged on a support, in particular a silicone or similar support. - each strain gauge includes a resistive track capable of deforming, i.e. contracting or expanding, when the wall of the gas conduit on which the strain gauge is fixed is deformed. - The remote data processing platform includes a computer server, preferably a "cloud" server. the telecommunications module is further configured to communicate in receive with an electronic device with a graphical interface configured to send data to the telecommunications module. The electronic device is a digital tablet, a multifunction phone or a laptop, or similar. The control unit is configured to determine, from the determined resistivity value R and a database giving a correspondence between pressure and resistivity R, the gas pressure prevailing in said main and secondary gas conduits carrying pressurized gas arranged downstream of the pressure regulating device. The control unit includes storage means for storing the reference resistivity value (Ro) and the database. The storage means include flash memory or similar; alternatively, the database is stored within the processor of each control unit. The control unit is configured to determine the flow rate(s) of gas flowing in the first secondary conduit and / or in the second secondary conduit carrying pressurized gas arranged downstream of the pressure regulating device, from at least one pressure measurement. The remote data processing platform is configured to control a display on a display screen, the gas flow rate(s) flowing in the first secondary conduit and / or in the second secondary conduit. Strain gauges are electrically powered, in particular their resistive track. a telemetry unit is associated with said gas storage tank in order to determine the quantity of residual gas in said gas storage tank, in particular a level of LOX. The telemetry unit is configured to transmit remotely, via a telecommunications network, to a gas supplier, measurements of residual gas quantity, in particular the LOX level. a gas vaporizer is arranged at the outlet, i.e. downstream, of said gas storage tank and configured to transform the LOX into gaseous oxygen, notably by heating the LOX. the downstream end of the main conduit branches at least into a first section or first secondary conduit and into a second section or second secondary conduit. the first secondary conduit comprises a plurality of initial sub-branches. the second secondary conduit comprises a plurality of secondary sub-branches. at least part of the first sub-branches and / or the second sub-branches are connected to wall outlets for gas distribution, in particular outlets for supplying gaseous oxygen or air. the resistive track of each strain gauge is configured so that its resistance or resistivity R is modified relative to a resting resistive value Ro proportionally to the deformation undergone by the resistive track in question. the resistive track of each strain gauge is configured to be modified in compression (R<R0) ou une tension (R> R0). The value of the resistance or resistivity R of the resistive track of each strain gauge is determined by the control unit, typically by the processor or microcontroller. an electrical power source supplies electrical current to each control unit, in particular a battery, especially rechargeable, or the mains (110 / 220V). The electrical power source also supplies electrical current to the strain gauges and telecommunication modules. Each strain gauge is configured to be configurable (i.e., parameter data) remotely via an independent device comprising a graphical interface and means of communication, including a digital tablet, a multifunction phone, a computer or similar. The communication module of each strain gauge is configured to receive parameter data from the independent device. The parameters of each strain gauge include a unique strain gauge identifier (ID), the diameter D of the gas conduit on which the gauge is arranged, relative location information with respect to a reference strain gauge, a pairing data and / or a time data (i.e. timestamp). According to another embodiment, the processor of the control unit is programmed to directly include the parameters of each gauge. It includes a reference strain gauge arranged in the region of the main conduit branching site. - it includes additional strain gauges arranged on the first and second secondary conduits. - Each strain gauge is configured to send data to the processing platform in the form of sets or "packets" of data. - each data set or packet includes at least one pressure value. - each data set or package includes one or more additional data points chosen from a time data point (i.e. timestamp), a gauge identifier (ID), a gas conduit diameter, a reference strain gauge identifier, and a distance separating the reference strain gauge from the strain gauge under consideration. - the processing platform is configured to perform preprocessing of all or part of the data from the strain gauges, in particular a resynchronization of the pressures measured by the strain gauges. - the processing platform is configured to also process all or part of the data from the strain gauges to determine the flow rate(s) of gas flowing in the gas duct(s), in particular in the first secondary duct and in the second secondary duct. - the processing platform is configured to command a display of at least the determined flow rate(s) on a display screen for a user, such as a network operator, responsible for the effective monitoring of the gas distribution network within the hospital establishment in question.

[0012] The invention will now be better understood with reference to the following detailed description, given by way of illustration but not limitation, with reference to the accompanying figures, among which:

[0013] [Fig-1] schematically represents a medical gas distribution installation of a hospital establishment supplied by a gas source, comprising a monitoring system including strain gauges according to the invention.

[0014] [Fig.2] schematically represents a connected strain gauge enabling non-invasive measurement of the local pressure prevailing in a conduit delivering medical gas.

[0015] [Fig.1] schematically illustrates an embodiment of a gas distribution installation 100 supplying medical gas(s), in particular oxygen (of medical / medicinal quality), to the medical gas distribution network 2, 3 of a hospital establishment, comprising a main gas line or conduit 2 and a secondary gas circuit 3 comprising secondary gas conduits 31, 32.

[0016] The installation 200 includes a gas source 1, namely a liquid oxygen (LOX) storage tank 11 supplying the network 2, 3. It can also contain gaseous oxygen (GOX) forming a "gaseous cloud" above the LOX in tank 11, i.e., GOX resulting from the vaporization of some of the LOX in tank 11. In the following description, for the sake of simplicity, the gas supplied by the gas source 1 is considered to be oxygen, but in other embodiments, it could be another medical-grade gas, such as N2O, air, etc.

[0017] Liquid O2 (LOX) level measurement means 14 measure, preferably continuously, the level of LOX in the internal volume 12 of the tank 11, for example a level sensor arranged in the tank IL. The measurement means 14 cooperates with the telemetry unit 13 to provide it with the LOX level measurements.

[0018] The telemetry unit 13, i.e. a data transmission device, transmits remotely, via a communication network, such as GSM, internet or other, the LOX level measurements to a remote site, for example to a gas supplier, where they are processed, for example compared to one or more thresholds, in order to alert the supplier when a predefined low threshold is reached, i.e. when the LOX level falls below this low threshold, and to allow the tank 11 to be refilled with LOX brought by tanker truck or similar.

[0019] The telemetry unit 13 also transmits, according to the invention, the LOX level measurements to the control unit 64 of a gas distribution network monitoring system 2, 3, as explained below.

[0020] In order to transform the LOX into GOX, a gas vaporizer 10 is used which is arranged downstream, i.e. at the outlet, of the storage tank 11. The outlet of the gas vaporizer 10 is fluidly connected (at 21a) to the upstream section or portion 21 of the main supply line 2, i.e. a gas pipeline or conduit, so as to supply it with GOX.

[0021] The upstream portion 21 of the main supply line 2 has a first diameter DI and supplies (at 21b) a pressure regulator 23, such as a gas pressure reducing device, arranged on the main supply line 2. Preferably, the first diameter DI is equal to several tens of millimeters, for example at least 40 mm.

[0022] The pressure regulator 23 is also connected (at 24a) to a downstream section or portion 24 of the main supply line 2 in order to supply it with GOX at a given pressure. In other words, the pressure regulator 23 guarantees, i.e., provides, a stable GOX pressure in the downstream portion 24 of the main supply line 2, referred to as the "nominal operating pressure". Advantageously, the nominal operating pressure is approximately between 4 and 5 bar, for example, approximately 4 bar.

[0023] The downstream portion 24 of the main conduit 2 branches (at 24b) into several sections or secondary conduits 31, 32, namely here into (at least) a first section or first secondary conduit 31 having a second diameter D2 and, furthermore, into a second section or second secondary conduit 32 having a third diameter D3.

[0024] The first and second secondary conduits 31, 32 are part of the secondary gas circuit 3, which is in fluidic communication with the main supply line 2. They preferably have equal diameters D2, D3 (i.e., D2 = D3), for example, on the order of approximately 15 mm. According to one embodiment, we have: D2 <D1 et D3<D1 (avec par exemple D2 = D3).

[0025] The first secondary conduit 31 itself has a plurality of sub-branches 311-31n, respectively, forming gas lines terminating at wall-mounted oxygen outlets 41-41n, respectively, located in a department 4 of the hospital, for example, an intensive care unit. The GOX circulating in the first secondary conduit 31 is therefore distributed to all or part of the sub-branches 311-31n depending on whether the wall outlets 411-41n distributing the GOX are in operation or at rest, for example, connected or not to medical devices using oxygen, such as flowmeters, mechanical ventilators, high-flow oxygen delivery devices, etc.

[0026] Similarly, the second secondary conduit 32 also supplies GOX, a plurality of sub-branches 321-32n, that is to say gas lines also leading to wall outlets 421-42n located in another department 5 of the hospital establishment, for example a light care department.

[0027] The gas pressure exerted at the wall outlets must not be less than 90% of the nominal service pressure (i.e. 4 bar relative), therefore here at least 3.6 bar relative, when the medical gas distribution network is operating within its operational range, in order to avoid the risk of the medical devices connected to the wall outlets 41 there 41n, 321-32n malfunctioning and endangering patients.

[0028] The operational range of the wall outlets is therefore determined by taking into account the type of service equipped with wall outlets (e.g., emergency, intensive care, minor care, etc.), the estimated utilization rate of the wall outlets (for example, 75% utilization), and the gas flow rate consumed through each of the wall outlets in operation. For example, for n (n>2) wall outlets 411-41n in an intensive care unit, it can be determined that 75% of the outlets are in use at any given time, for an average flow rate of 20 L / min. Thus, for 20 outlets (n=20), a total flow rate circulating in the first secondary conduit 31 of approximately 300 L / min maximum can be considered. Considering this maximum flow rate and the length of the first secondary conduit 31, for example, from several meters to several tens of meters, defined between the end 24b of the downstream portion 24 and the downstream end 31b of this first secondary conduit 31, it can be determined that a diameter D2 of 15mm should allow compliance with the requirements of ISO 7396-1, in particular a pressure prevailing at the downstream end 31b of the first secondary conduit 31 greater than 90% of the nominal service pressure (here 3.6 bar relative).

[0029] The same applies to the sizing of the second secondary conduit 32 supplying a light care service 5, for which it is determined that a maximum total flow rate of 320L / min can also be observed (i.e. 100 intakes at 80% at 4L / min for example) and this, for a diameter D3 of the second secondary conduit 32 also of 15 mm.

[0030] Under unusual or exceptional conditions, for example, an influx of COVID patients or other patients, the utilization rate of the wall outlets 411-41n may reach 100%, and to optimize patient care, their oxygenation must be ensured by high-flow oxygen delivery devices that consume a significant amount of O2, for example, using 60 L / min or more. This results in a total flow rate of GOX circulating in the first secondary conduit 31 of approximately 420 L / min, which is well above the initially expected maximum flow rate. However, the pressure drop between the downstream end 2b of the portion 24 and the downstream end 31b of the first secondary conduit 31 varies with the square of the flow rate between these two points. It therefore becomes much lower than the minimum pressure of 3.6 bar, which causes malfunctions in the medical devices connected to the various wall-mounted O2 outlets 411-41n in the intensive care unit 4 under consideration.

[0031] We can then understand the importance of being able to operate an effective monitoring of the gas distribution network 2, 3, in particular of the secondary conduits, 31, 32, namely here of the first secondary conduit 31 and the second secondary conduit 32, in order to detect any saturation of the secondary conduits 31, 32 and to warn, if necessary, an operator, for example the technical manager supervising the medical gas distribution network, of the imminence of such saturation of one and / or the other of these conduits.

[0032] To do this, a gas distribution network monitoring system 2, 3 is implemented, comprising the control unit 64 and non-invasive sensors 61 including strain gauges 6, 6a, 6b, arranged on the external wall of the sections or conduits 24, 31, 32, as illustrated in [Fig.1].

[0033] [Fig.2] schematically illustrates an embodiment of such a connected non-invasive sensor 61 comprising a strain gauge 6, arranged on a gas conduit 9, for example a gas conduit of a gas network ensuring the delivery of gas, such as oxygen, within a hospital establishment.

[0034] As can be seen, the strain gauge 6 is electrically connected to the control unit 64, in particular one (or more) electronic card 64.1 with microprocessor 65, such as a microcontroller, of the control unit 64, via an electrically connected cable 63.

[0035] The strain gauge 6 comprises a support 61.1, such as a silicone substrate, or similar material, carrying a deformable resistive track 62. This resistive track 62 is capable of deforming, i.e., contracting or expanding, under the action of a mechanical stress, in particular in the event of deformation of the wall 90 of the gas conduit 9 to which it is fixed.

[0036] Deformations of the resistive track 62 modify its resistivity R (also called resistance R) relative to a resting resistive value Ro depending on the deformation undergone, i.e., depending on whether the resistive track 62 undergoes compression (R<R0) ou une tension (R> R0). The resistivity value R of the resistive track 62 is determined by the control unit 64, typically by its processor 65 or microcontroller. The determination of the resistivity value R of the resistive track 62 is usually carried out using a Wheatstone bridge (https: / / en.wikipedia.org / wiki / Wheatstone_bridge) driven by the microprocessor 65 and the electronic board 64.1.

[0037] A telecommunications module 66 is also provided, arranged in the control unit 64 and configured to transmit and / or receive data, i.e., information or other data. It is preferably integrated into the electronic board 64.1 of the control unit 64; however, according to another embodiment, it may be independent and configured to cooperate with the electronic board 64.1, in particular to retrieve the data to be transmitted.

[0038] More specifically, the telecommunications module 66 is configured to receive communication with an independent electronic device 7 comprising a graphical interface 71, such as a digital tablet, a multifunction phone (smartphone), a laptop or similar device, which electronic device 7 is configured to send data to the telecommunications module 66. When the telecommunications module 66 receives data, it retransmits or transfers it to the control unit 64 which processes it, in particular within the microprocessor 65.

[0039] The telecommunications module 66 is also capable of transmitting data, for example by cellular means or otherwise, for example via a LoRa or similar type communication protocol, which data can then be captured for example by a receiving terminal (not shown) acting as a communication relay.

[0040] As illustrated in [Fig. 1], the data can be processed by a remote data processing platform 8, such as a cloud-type computer server or similar, and then provided, once processed, for example aggregated, to an operator, by for example the technical manager of the medical gas distribution network in question, in particular displayed on a display screen for the operator's attention.

[0041] The electronic board 64.1 of the control unit 64 is powered by a battery or by mains (110 / 220V), which allows the various components requiring power to be powered and controlled, in particular the strain gauge 61, the control unit 65 and the telecommunications module 66.

[0042] The strain gauge 6 of [Fig.2] is fixed to the external peripheral surface 91 of the gas conduit 9 by a suitable device or fastening means 61.2, for example a collar, clips or the like, which are attached to the strain gauge 6 by gluing, welding or the like, in particular attached to the deformable support 61.1 carrying the resistive track 62.

[0043] Conduit 9 is typically a copper conduit carrying a medical gas, such as O2. For example, it has an external diameter of approximately 15 mm and a wall thickness of approximately 1 mm. The same applies to secondary conduits 31 and 32 in [Fig. 2]. Indeed, the diameters of medical gas conduits are standardized (EN 13348), and therefore there are only a limited number of possible diameters, among which the 15 mm diameter is the most commonly used for secondary conduits in hospital networks.

[0044] When the medical gas, here O2, flows at a given pressure P, for example of several relative bars, in the internal conduit 92 or lumen of the conduit 9, the wall 90 of the conduit 9 will deform proportionally to the pressure of the gas it carries, that is to say that the diameter D of the conduit 9 will grow, i.e. increase, proportionally to the gas pressure P prevailing in the internal passage or lumen 92 of the conduit 9. The rate of deformation depends not only on the gas pressure P in the conduit 9 but also on the diameter D and the thickness E of the wall 90 of the conduit 9, as well as on the mechanical properties of the material of the conduit 9, e.g. copper (cf. Young's modulus and Poisson's ratio).

[0045] More specifically, the relationship linking the gas pressure P to a given conduit corresponds to the following formula:

[0046] Dri^-v)

[0047] where: • P is the pressure in Pa • E is Young's modulus in GPa • Di is the internal diameter of the conduit in mm • A Di is the deformation of the conduit, measured by the gauges • t is the wall thickness of the duct in mm • v is Poisson's ratio, i.e. constant at 0.34 for copper alloys.

[0048] As explained above, any gas distribution network in a hospital establishment must meet specific standards, such as the NF EN-13348 standard which requires the use of tubes of different diameters and tube wall thicknesses, as well as a specific copper alloy, typically a Cu-DHP type alloy for hospital network conduits.

[0049] The Cu-DHP copper alloy is a deoxidized phosphorus copper alloy which usually contains a phosphorus content between 0.013% and 0.040% by weight.

[0050] Thus, concerning the internal / external diameters and the wall thickness of the conduit considered, for a tube with an external diameter of 15 mm, the wall thickness can be equal, according to NF EN-13348, to 0.7 mm, 1 mm or 1.2 mm, which corresponds to an internal diameter Di of 13.6 mm, 13 mm or 12.6 mm, respectively.

[0051] The external diameter and wall thickness information of a hospital network duct is standardly indicated on its external surface (see EN-13348). The internal diameter Di can therefore be easily deduced from this.

[0052] These dimensional parameters (i.e. external and / or internal diameters and wall thickness) can be used when setting up the strain gauges and stored within the control unit 64, for example within storage means of the unit 64, in particular within its processor or a dedicated memory, such as a flash memory.

[0053] When subjected to pressure variations, the conduit 9 (i.e. its wall 90) deforms, in compression or tension, and these deformations propagate, in a (quasi-) instantaneous manner, to the resistive track 62 of the strain gauge 6, in particular through the wall 90 of the conduit 9 and the fixing means 61.2, which resistive track 62 then also deforms in correlation with these pressure variations.

[0054] In other words, as soon as the strain gauge 6 is installed on the conduit 9 and the latter is subjected to internal gas pressure, the resistive track 62 of the strain gauge 6 is energized due to the expansion of the conduit 9 under the effect of the pressure. The control unit 64, in particular the processor 65, will then be able to determine its resistive value R, which is greater than the resting resistive value Ro of the resistive track 62, i.e., a reference resistance value Ro.

[0055] Then, the control unit 64 determines, from the determined resistance value R and a stored database, the gas pressure P prevailing in the gas conduit 9, for example carrying medical oxygen.

[0056] Preferably, the database is obtained beforehand, for example during the manufacturing process of gauge 6 or subsequently via routine tests, by establishing a correlation between resistive values ​​R of resistive track 62 and different diameters of gas pipes subjected to different pressures, for example pressures from 0 bar relative (i.e. atmospheric pressure) to 10 bar relative. Ro denotes the resistance value corresponding to a gas pipe subjected to atmospheric pressure (1 atm = 0 bar relative).

[0057] For example, all the conduits referenced in NF EN-13348, i.e. of different diameters and wall thicknesses, can be used to constitute the database and make it an exhaustive database.

[0058] It is noted that, in addition to the dimensional data of the conduit, i.e. internal diameter Di and wall thickness t, the calculation formula above includes Young's modulus, which represents the rigidity of a material under elongation (which is similar to an "elasticity").

[0059] However, the value of this coefficient depends on the alloy considered, for example a copper alloy. For example, the Cu-DHP alloy, which is generally used for hospital conduits, has a Young's modulus of approximately 130 GPa at 20°C, while the CW114C alloy has a Young's modulus of approximately 120 GPa at 20°C, which can result in a pressure error of 10% on the pressure measurement prevailing in the conduit.

[0060] Therefore, it is necessary that the database be made on conduits having the alloy specified in NF EN-13348, i.e. CuDHP, so that the relationship between the deformation under pressure of a given conduit is as accurate as possible.

[0061] In other words, for a given conduit (i.e. internal diameter Di and wall thickness t), at a given control temperature T0, the database can link a deformation measurement of the conduit considered (being represented by the measured resistive value R) to the pressure P prevailing in this conduit.

[0062] The database is preferably integrated, i.e. stored, directly within the processor 65 of the control unit 64, or, as appropriate, in a dedicated memory, such as a flash memory, cooperating with the processor 65.

[0063] Advantageously, after being positioned on the gas conduit 9, the connected strain gauge 6, i.e., the (tele)communicating strain gauge, is preferably configured via the graphical interface 71 of the independent device 7, such as a digital tablet or similar device. The configuration data is then transmitted remotely via the tablet or similar device's communication means to the communication module 66, as already explained.

[0064] The aforementioned database is created at a given control temperature T0. However, under real-world conditions, the temperature T prevailing at the level of a given duct may differ from this control temperature T0, which can introduce bias in the measurement results. Indeed, all materials naturally tend to to lengthen or contract under the effect of temperature (i.e., thermal expansion). Therefore, according to one embodiment, a temperature sensor can be added to the various strain gauges in order to correct for the effect of ambient temperature (relative to the control temperature TO) in order to improve the accuracy of the measurements provided.

[0065] The strain gauges 6, 6a, 6b of [Fig.1], which operate as described above in relation to [Fig.2], allow monitoring of different points of the gas network 2, 3. Typically, strain gauge 6 serves as a reference gauge.

[0066] According to one embodiment, the parameters of each strain gauge 6, 6a, 6b, i.e. their parameterization data, originating for example from a digital tablet type device 7 or similar, can be fixed or selected by an operator and include a unique identifier (ID) of each strain gauge 6, 6a, 6b, the diameter Di of the gas conduit on which they are installed, relative location information of the reference strain gauge 6 and additional strain gauges 6a, 6b, strain gauge pairing data, and even other useful information, in particular time data, i.e. a timestamp.

[0067] According to another embodiment, the processor 65 of the control unit 64 is programmed to directly include the parameters of each gauge, such as its unique identifier (ID), the internal diameter Di of the gas conduit to which the strain gauge(s) is attached, and / or other parameters.

[0068] Generally, once the pressure value P has been determined, the control unit 64 is configured to transmit this pressure, for example by teletransmission, along with the timestamp and unique identifier of the gauge in question, the diameter D of the gas conduit 9, the pairing with other strain gauges and the location information, to the remote computer platform 8 for further processing and exploitation of the information.

[0069] Data transmission can be done at a given frequency, for example every 10 milliseconds or at another suitable frequency.

[0070] In [Fig. 1], a schematic representation shows the integration of three strain gauges 6, 6a, 6b on the secondary circuit 3 of the medical gas distribution network 2, 3, as described above. Of course, more than three gauges could be used, or conversely, fewer than three gauges, depending, for example, on the number of pipes to be monitored.

[0071] In [Fig. 1], the connected strain gauges 6, 6a, 6b are arranged here as an example in the region of the branch site 24b of the main conduit 2 (i.e., gauge 6) and elsewhere on the first and second secondary conduits 31, 32 (i.e., gauges 6a, 6b), in order to measure the distribution of gas flow rates; however, they could be arranged at other locations in the network. They operate as described above, in reference to [Fig.2]. More specifically, the first additional strain gauge 6a is arranged at the downstream end 31b of the first secondary conduit 31, and the second additional strain gauge 6b is installed at the downstream end 32b of the second secondary conduit 32. In other words, the main strain gauge 6 is arranged here between the additional strain gauges 6a, 6b.

[0072] These strain gauges 6, 6a, 6b, in particular the processors 65 of the control unit 64 associated with these strain gauges 6, 6a, and 6b, have been configured, for example, via the graphical interface device 71, such as a digital tablet or similar device. These strain gauges 6, 6a, 6b, or more precisely the processor(s) 65 of the control unit 64, each send all the aforementioned data to the data processing computer platform 8, as already explained. Thus, when setting up strain gauges 6, 6a, 6b, the diameters Di2, Di3, which are identical, for example of the order of 13 mm, are entered (in addition to the wall thickness of the conduits on which they are placed) via the digital tablet or any similar device 7, which makes it possible to determine the local pressure prevailing in the secondary conduit 3 at the location sites of strain gauges 6, 6a, 6b.

[0073] By way of example, the data relating to each of the connected strain gauges 6, 6a, 6b can be sent to the processing platform 8 in the form of data packets: - Reference gauge 6: [T, Jl, Dil, PI, 0, 0] - First additional gauge 6a: [T, J2, Di2, P2, RefJl, Ll] - Second additional gauge 6b: [T, J3, Di3, P3, RefJl, L2]

[0074] where: - T is a time data, i.e. a timestamp, for example of the form DD / MM / YY XXhXXminXXsXXms. - Jl, J2, J3 are the unique identifiers (ID) of gauges 6, 6a, 6b. - Dil, Di2, Di3 are the diameters of the medical gas pipes on which the gauges ô, 6a, 6b are installed. - PI, P2, P3 are the local pressures prevailing in the conduits at the level of the gauges 6, 6a, 6b considered. - RefJl is the identifier of the reference strain gauge 6 (ID = Jl) to which the additional strain gauges 6a, 6b are matched. - L1, L2 are the distances (in meters) separating the additional strain gauges 6a, 6b from the reference gauge 6.

[0075] The reference strain gauge 6 being preferably a reference gauge for the other strain gauges, i.e. here the additional strain gauges 6a, 6b, it is not paired with any other connected strain gauge, so its pairing is designated by "0" and its relative location is also designated by "0" in the data packet that concerns it.

[0076] By way of illustrative example, it is considered that the pressure at the level of the reference strain gauge 6, i.e. prevailing at the downstream end 24b of the downstream portion 24, is 4.5 bar, while the pressure prevailing in the first secondary conduit 31 at the level of the strain gauge 6a is 4.2 bar, and that prevailing in the second secondary circuit 32 at the level of the strain gauge 6b is 3.8 bar.

[0077] The resistive track 62 of the strain gauges 6, 6a, and 6b will reflect a resistive value corresponding to the pressure-induced deformation of the various conduits on which the strain gauges 6, 6a, and 6b are arranged. The processors 65 of the control unit 64 associated with the various strain gauges 6, 6a, and 6b are then able to convert the different resistive values ​​of the resistive tracks 62 into pressure, namely a pressure of 4.5 bar for strain gauge 6, a pressure of 4.2 bar for strain gauge 6a, and a pressure of 3.8 bar for strain gauge 6b.

[0078] If the distance between the reference strain gauge 6 and the first strain gauge 6a is 50 meters, and that between the second strain gauge 6 and the strain gauge 6b is 30 meters, the electronics, i.e. processors 65 of the control units 64, of the strain gauges 6, 6a and 6b will send at a given frequency, for example every 10ms, "packets" or sets of data to the processing platform 8, like a remote computer server, as illustrated in [Table 1] below.

[0079] [Table 1] Gauge Time Stamp ID Di (mm) P (bar) Ref. L (m) 6 14 / 4 / 2000 10:40:37 150ms J1 13 4.5 0 0 6a 14 / 4 / 2000 10:40:37 150ms J2 13 4.2 J1 50 6b 14 / 4 / 2000 10:40:37 150ms J3 13 3.8 J1 30

[0080] Upon receipt of these data sets at the processing platform 8, it is possible to extract the flow rates circulating respectively in the first and second secondary conduits 31, 32. Indeed, any flow rate circulating in the internal diameter Di of a given conduit results in a pressure drop which is a function of the nature of the medium (in this example gaseous O2), the diameter of the conduit, the length of the conduit and the flow rate circulating in the conduit considered.

[0081] Thus, knowing the nature of the gas (i.e., oxygen) flowing in the first secondary conduit 31, the pressure difference between the connected strain gauges 6 and 6a, the diameter Di2 of the first secondary conduit 31, and the length separating the connected strain gauges 6 and 6a, it is possible to determine the flow rate in the first secondary conduit 31 by applying the Darcy-Weisbach equation, for example. See, for example, the Wikipedia page which provides this equation: https: / / en.wikipedia.org / wiki / Darcy%E2%80%93Weisbach_equation).

[0082] Advantageously, preprocessing can be performed on the processing platform 8 by resynchronizing the pressures measured by the connected strain gauges 6, 6a. Indeed, under the action of an instantaneous flow rate, the propagation of the pressure wave from point A to point B occurs only at the speed of sound. If a fixed instantaneous flow rate, for example 100 L / min, appears at the reference connected strain gauge 6, the pressure drops at the additional strain gauge 6a to reach a stable value, after the sound wave has traveled between the strain gauges 6, 6a considered. The distance separating these gauges being here 30 meters and the speed of sound being approximately 330 m / s, the pressure at the connected strain gauge 6a is established after a latency time of approximately 90 milliseconds (msec).During pressure resynchronization, the processing algorithm(s) deployed on the processing platform 8 take into account this latency time between the paired strain gauges in order to avoid returning erroneous flow values ​​circulating in the medical gas distribution network.

[0083] By exploiting the data returned by strain gauges 6, 6a, 6b, it is possible to determine, in the platform 8, the flow rates circulating in the first secondary conduit 31 and in the second secondary conduit 32. These flow rates and other data (IDs, pressure...) can then be displayed on a display screen for a user, such as a network operator, responsible for the effective monitoring of the gas distribution network within the hospital establishment in question.

[0084] Estimating the flow rates in sections of the medical gas distribution network is not limited to straight, i.e., linear sections. Indeed, the equation transforming a pressure drop into a flow rate can take into account possible changes in cross-section, the presence of bends, etc.

[0085] Using strain gauges attached to the gas pipes of the network is advantageous because their installation on existing networks does not require interrupting the pipes of the hospital facility's network, regardless of the network sites chosen for their installation, and therefore ensures continuity gas supply, in particular the supply of oxygen to patients in need.

[0086] From the information / data collected and / or calculated, it is possible to determine and display a score, for example a saturation rate of each of the portions of a medical gas distribution network considered, in order to warn of the imminence of network saturation and thus allow the operator to take appropriate protective measures.

[0087] In summary, according to the invention, a monitoring system is used implementing strain gauges 6, 6a, 6b placed on the external surface of the gas conduits 31, 32, 24 of the hospital gas network in order to estimate the pressure prevailing in these conduits 31, 32, 24.

[0088] Indeed, by placing (at least) two strain gauges (6, 6a or 6, 6b) on the same gas conduit (31 or 32) having a given internal diameter, which are spaced apart from each other, it is possible to estimate a gas flow rate passing through the conduit in question due to the deformation of the conduit taking place under the effect of the gas pressure (GOX for example) exerted in the conduit, which is measured by the gauges 6, 6a, 6b, and then to determine the medical gas consumption at different locations in the gas distribution network, that is to say, to obtain an approximation of the flow rate(s) circulating in the network.

[0089] The determination of the pressure P prevailing locally in the conduit, i.e. at the location of the strain gauge 6, 6a, 6b, is determined by the measurement of a resistive value R which is greater than the rest resistive value Ro corresponding to a conduit of similar diameter at rest (e.g. at atmospheric pressure), which rest resistive value Ro is stored in a database within storage means, such as a flash memory or similar, or directly within the (micro)processor 65 of the control unit 64.

[0090] As previously stated, all conduits referenced in NF EN-13348, i.e., of various diameters and wall thicknesses, can be used to create the database and make it exhaustive. For example, diameters between 6 and 108 mm and thicknesses between 0.7 and 2.5 mm.

[0091] However, there may be variations, even minimal ones, between the samples considered (i.e., test ducts) during the creation of the database, and between the gas ducts in the gas network on which the strain gauges are placed. Such variations appear during the manufacturing process of the tubes, i.e., ducts, and result in "tolerances" (i.e., small variations) around, in particular, the internal diameter and wall thickness of the ducts considered.

[0092] Thus, the pressure value returned by a given strain gauge 6, 6a, 6b, although close to the "real" pressure value prevailing in the conduit, is tainted by an error, for example a measurement of 3.9 bar instead of 4 bar actually present.

[0093] By using two strain gauges 6, 6a, 6b arranged on the same gas conduit of a given diameter and spaced apart from each other, it is possible to estimate the pressure loss, e.g. the pressure difference between the two measurement points operated by the strain gauges 6, 6a, 6b and to deduce a gas flow rate passing through said conduit.

[0094] For example, considering that the first strain gauge 6 measures a pressure of 3.9 bar instead of the actual 4 bar, and that the second strain gauge 6 is placed on the same conduit (i.e., identical properties at both conduit sites), the second gauge 6a may measure a value of 3.5 bar, for example, while the actual pressure is 3.6 bar, a difference of 0.1 bar. Therefore, if the value of the pressure variation (i.e., pressure drop) is correct, namely 0.4 bar, the absolute value, i.e., the pressure level, is incorrect by 0.1 bar.

[0095] However, the calculation of the flow rate circulating in the gas conduit(s) depends on the absolute pressure values. The delivered flow rate, although representative of the actual flow rate, may be subject to error.

[0096] Therefore, when it is desired to improve the accuracy of flow rate determination, it is proposed, according to the invention, to carry out a calibration of the flow rate, or more generally of the flow rates circulating in the different gas conduits equipped with strain gauges, as described below.

[0097] As already stated, LOX quantity measurement means 14 determine, preferably continuously, the level of LOX (i.e. residual quantity) in the tank 11 and the telemetry unit 13 of [Fig.1] transmits, remotely, the LOX level measurements (i.e. the residual quantity of LOX) to the control unit 64, which receives and processes them, as well as the data emitted by the various strain gauges 6, 6a, 6b.

[0098] After installation of the various strain gauges 6, 6a, 6b and receipt of the first data / measurements, a first calibration phase is carried out.

[0099] This first calibration phase implements a dedicated algorithm that analyzes the data received by the control unit 64 over a predefined period of time, typically several hours, generally at least 4 hours, for example on the order of 8 hours.

[0100] During this analysis, the algorithm of the control unit 64 performs various operations during the time period considered. In particular, the algorithm determines the volume of O2 injected into the medical gas piping network by considering the difference in the level of LOX (i.e., gas in liquid form) over the time period considered (using as a reference, the dimensions of the tank 11, which are also transmitted to the control unit 64).

[0101] This volume of injected O2 can be compensated for the rate of evaporation of LOX (which escapes to the atmosphere via a degassing device, it is usually on the order of 2% of the useful volume, i.e. injected into the medical gas pipeline network.

[0102] At the same time, the algorithm performs the accumulation (i.e. addition) of the flow rates circulating in the different gas conduits equipped with strain gauges 6, 6a, 6b which cover the consumption of gas, e.g. GOX, by all services consuming medical gases.

[0103] The summation of the flow rates, during the given period of time, makes it possible to determine the total volume of gas that has been delivered to the wall distribution outlets of the hospital, via the various gas conduits of the hospital network.

[0104] Therefore, the sum of the different volumes should be identical, or (very) close, to the volume of O2 injected into the medical gas conduit network obtained by vaporization of LOX, during the given period of time.

[0105] Any significant difference, i.e. greater than a given threshold, for example of at least 10%, entails the implementation of a correction corresponding to the difference that has been determined.

[0106] Thus, if the volume of O2 injected (i.e. volume used Vu) into the medical gas duct network is determined to be equal to 80 m3 for example, while the sum of the gas volumes (i.e. a total volume Vt) having been delivered through the different gas ducts is only 70 m3, the algorithm of the control unit 64 (i.e. including processor means implementing the algorithm) then determines that there is more than 10% (threshold exceeded) of volume difference of about 1.14, namely a ratio of 80 / 70.

[0107] The algorithm of the control unit 64 then applies, i.e. assigns, to each of the medical gas conduits allowing the determination of a flow rate, i.e. the conduits equipped with strain gauges 6, 6a, 6b, a correction factor of 1.14.

[0108] Once the correction factor has been determined, the flow information can be corrected in real time by the control unit 64, before being returned to the user to give him an overview of the gas consumption within the gas network in question.

[0109] Such a calibration phase may optionally be repeated after a given period of time, for example every week, in order to ensure that the gauges have not undergone measurement deviation or 'sensor drift', for example after a few weeks or months of use.

[0110] The installation of the invention has the advantage of being able to be implemented on existing gas networks without having to interrupt the gas supply by that network, i.e., the installation of the strain gauges is carried out on gas lines which can remain under pressure and continue to carry gas, such as oxygen, because there is no need to interrupt the gas supply to patients.

[0111] In general, the present invention is applicable to any gas distribution network within a hospital building, in particular the medical oxygen (GOX) distribution network and the medical air distribution network, supplying the wall gas supply outlets to which medical devices are connected, provided that these networks are identical or similar in terms of construction and are otherwise subject to the same normative requirements, in particular in terms of nominal distribution pressure and / or minimum supply pressure of the wall outlets.

Claims

1.

2. Demands Medical gas distribution installation (100) comprising: - a gas distribution network (2, 3) arranged within a hospital establishment, comprising a main gas conduit (2) branching into several secondary gas conduits (3; 31, 32) conveying gas, - a gas source (1) comprising a gas reservoir (12) containing gas in liquid form fluidly connected to the main gas conduit (2) to supply it with gas from said gas reservoir (12), - and a monitoring system for said gas distribution network (2, 3) comprising: • strain gauges (6, 6a, 6b) arranged on the main (2) and / or secondary (31, 32) gas lines, and associated with a control unit (64) to provide it with at least one resistivity (R) value for each strain gauge (6, 6a, 6b), and • the control unit (64) configured to determine, from the resistivity value (R) provided by the strain gauges (6, 6a, 6b), at least one gas pressure reflecting the gas pressure exerted in the gas conduit (2, 31, 32) on which the strain gauge (6, 6a, 6b) in question is arranged, and, furthermore, to process said at least one gas pressure and deduce therefrom at least one gas flow rate circulating in the first secondary conduit (31) and / or in the second secondary conduit (32), characterized in that the gas tank (12) includes gas quantity measurement means (14) configured to measure a residual quantity of gas in the gas tank (12) and a telemetry unit (13) cooperates with the gas quantity measurement means (14) to retrieve and transmit the residual quantity measurement(s) of gas to the control unit (64). Installation according to claim 1, characterized in that the control unit (64) is configured to calculate a total volume (Vt) of gas, over a given period of time, from the determined gas flow rates having circulated in the first secondary conduit (31) and / or in the second secondary conduit (32), during the said given period of time.

3. Installation according to claim 1, characterized in that the control unit (64) is further configured to determine a volume of gas used (Vu) from the residual quantity of gas measurements having been measured by the gas quantity measuring means (14) during said given time period.

4. Installation according to claims 2 and 3, characterized in that the control unit (64) is further configured to determine a volume ratio Vu / Vt from the total volume of gas (Vt) and the volume of gas used (Vu), and to compare the volume ratio Vu / Vt to a given threshold value (Vs).

5. Installation according to claims 1 and 4, characterized in that the control unit (64) is further configured to use the volume ratio Vu / Vt to correct the gas flow rate(s) determined from the gas pressures within the first secondary conduit (31) and / or the second secondary conduit (32), when the control unit (64) determines that the volume ratio Vu / Vt is greater than the given threshold value (Vs), i.e. Vu / Vt > Vs.

6. Installation according to one of claims 4 or 5, characterized in that the given threshold value (Vs) is 10%.

7. Installation according to claim 1, characterized in that the gas reservoir (12) contains oxygen in liquid form (LOX).

8. Installation according to claim 1, characterized in that a pressure regulating device (23) is arranged on the main gas conduit (2), the main gas conduit (2) branching into several secondary gas conduits (31, 32), downstream of said pressure regulating device (23).

9. Installation according to claim 1, characterized in that each strain gauge (6, 6a, 6b) comprises a deformable resistive track (62) configured to deform proportionally to the gas pressure exerted in the gas conduit (2, 31, 32) on which the strain gauge (6, 6a, 6b) in question is arranged.

10. Installation according to claims 1 and 9, characterized in that the control unit (64) is configured to: determine the resistivity (R) of each strain gauge (6, 6a, 6b) from the deformation of the resistive track (62) of the strain gauge (6, 6a, 6b) considered and a reference resistivity value (Ro), and determine the gas pressure from the resistivity (R) of each strain gauge (6, 6a, 6b), each determined gas pressure reflecting the gas pressure exerted in the gas conduit (2, 31, 32) on which the strain gauge (6, 6a, 6b) considered is arranged.

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