Medical gas distribution installation with network monitoring system

Abstract

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 the residual quantity of gas in the tank (12) and a telemetry unit (13) for transmitting the residual gas quantity measurements to the control unit (64).

Description

[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 settings, 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 referred to as 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 hospitals is essential to understand the specific consumption of different departments and manage replenishments to avoid any gas supply disruptions that could compromise patient safety, particularly in the event of very high consumption, especially of oxygen (O2), such as during the Covid-19 pandemic, or in the case of high-flow oxygen therapy or "HFOT" (for High Flow Oxygen Therapy ).

[0004] Therefore, gas networks are typically designed and sized to guarantee a nominal gas pressure within a desired flow rate range, taking into account the specific needs of each hospital department, which vary from one department to another. Generally, the nominal operating pressure is around 4 to 5 bar relative, according to ISO 7396-1.

[0005] However, in the event of a peak in consumption, the gas network may not be able to 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 flow meters at various locations within the medical gas network. However, this solution is not ideal because it requires interrupting, i.e., cutting, the network conduit to install the flow meters, which can lead to the entry of dust or other pollutants, with the risk of malfunction in downstream equipment or accidents (i.e., fire), and necessitates 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 system, particularly intended for a hospital, comprising: a gas distribution network configured for installation within a hospital facility, comprising a main gas line branching into several secondary gas lines carrying gas, a gas source comprising a gas reservoir containing gas in liquid form fluidly connected to the main gas line 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 associated with a control unit to provide it with at least one resistivity value (R) 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 gas pressure exerted in the gas line on which the strain gauge in question is arranged, and, furthermore,to process said gas pressure and deduce from it 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 tank includes gas quantity measurement means configured to measure a residual quantity of gas in the gas tank, and a telemetry unit cooperates with the gas quantity measurement means to retrieve and transmit the residual quantity measurement(s) of gas 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 time period, based on the determined gas flow rates that have passed through the first secondary duct and / or the second secondary duct during that time period. The control unit is also configured to determine a volume of gas used (Vu) from the residual gas quantity measurements taken by the gas quantity measurement means during that time period. Furthermore, the control unit is configured to determine a volume ratio Vu / Vt from the total gas volume (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 volumetric 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 volumetric ratio Vu / Vt exceeds the given threshold value (Vs), i.e., Vu / Vt > Vs. The given threshold value (Vs) is approximately 10%. The gas reservoir contains liquid oxygen (LOX). A pressure regulating device is arranged on the main gas conduit, which branches into several secondary gas conduits downstream of the pressure regulating device. Each strain gauge includes a deformable resistive track configured to deform proportionally to the gas pressure 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 based on the deformation of the strain gauge's resistive track and a reference resistivity value (Ro). The control unit is also configured to determine the gas pressure based on the resistivity (R) of each strain gauge, with each determined gas pressure reflecting the gas pressure in the gas line on which the strain gauge is installed. The strain gauges are installed downstream of the pressure regulator on the primary and / or secondary gas lines. The control unit communicates 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. The gas distribution network is arranged within the hospital establishment.

[0011] In various embodiments, the installation of the invention may further include one or more of the following features: The gas distribution network comprises gas pipes installed within the hospital, particularly along the hospital walls, i.e., walls, partitions, or similar structures. 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 comprises a storage tank or similar container holding liquid oxygen topped with gaseous oxygen, i.e., a gaseous oxygen ceiling. The pressure regulating device is configured to control the pressure and ensure a stable pressure between 3 and 7 bar relative, preferably between approximately 4 and 5 bar relative, advantageously around 4 bar. The strain gauges comprise a reference gauge and one or more additional or secondary gauges. Each additional strain gauge is matched to the reference strain gauge.The strain gauges are fixed to / on the outer peripheral surface of the gas ducts. Each control unit includes at least one (micro)processor, in particular a microcontroller. The (micro)processor or microcontroller of each control unit is arranged on (at least) one electronic board. The electronic board is arranged within the control unit. The control unit implements one or more algorithms or analogs. Each strain gauge includes a deformable resistive track arranged on a support comprising fastening means for attachment to the outer peripheral wall of a gas duct. Each strain gauge includes a resistive track arranged on a support, in particular a silicone or analogous support. Each strain gauge includes a resistive track capable of deforming, i.e., contracting or expanding, upon deformation of the wall of the gas duct to which the strain gauge is fixed.The remote data processing platform includes a computer server, preferably a cloud server. The telecommunications module is further configured to receive data from a graphical user interface (GUI) device configured to send data to the telecommunications module. The GUI device is a tablet, a multifunction phone, a laptop computer, or a similar device. The control unit is configured to determine, from the determined resistivity value R and a database providing a correlation between pressure and resistivity R, the gas pressure in the main and secondary gas lines carrying pressurized gas located downstream of the pressure regulator. 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 gas flow rate(s) in the first secondary conduit and / or the second secondary conduit carrying pressurized gas, located downstream of the pressure regulating device, based on at least one pressure measurement. The remote data processing platform is configured to display the gas flow rate(s) in the first secondary conduit and / or the second secondary conduit on a display screen. The strain gauges are electrically powered, specifically their resistive track. A telemetry unit is associated with the gas storage tank to determine the amount of residual gas in the gas storage tank, specifically the LOX level.The telemetry unit is configured to transmit, remotely via a telecommunications network, residual gas quantity measurements, specifically the LOX level, to a gas supplier. A gas vaporizer is arranged at the outlet, i.e., downstream of the gas storage tank and configured to convert the LOX to gaseous oxygen, notably by heating the LOX. The downstream end of the main conduit branches into at least one first section or first secondary conduit and a second section or second secondary conduit. The first secondary conduit comprises a plurality of first sub-branches. The second secondary conduit comprises a plurality of second sub-branches. At least some of the first sub-branches and / or the second sub-branches are connected to gas distribution wall outlets, specifically gaseous oxygen or air supply outlets.The resistive track of each strain gauge is configured so that its resistance or resistivity R is modified relative to a resting resistive value R0 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 (R0).<R 0 ) ou une tension (R> R0). The resistance or resistivity R value of the resistive track of each strain gauge is determined by the control unit, typically the processor or microcontroller. A power source supplies each control unit, specifically a battery (especially a rechargeable one) or mains power (110 / 220V). The power source also supplies power to the strain gauges and telecommunication modules. Each strain gauge is configured to be configurable (i.e.parameterization data) remotely via an independent device comprising a graphical interface and communication means, including a tablet, a multifunction phone, a computer, or similar device. The communication module of each strain gauge is configured to receive parameterization data from the independent device. The parameters of each strain gauge include a unique strain gauge identifier (ID), the diameter D of the gas duct on which the gauge is arranged, relative location information with respect to a reference strain gauge, pairing data, and / or time data (i.e., timestamp). In 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 branch site of the main duct.It includes additional strain gauges arranged on the first and second secondary ducts. Each strain gauge is configured to send data to the processing platform as sets or "packets" of data. Each set or packet of data includes at least one pressure value. Each set or packet of data includes one or more additional data points chosen from a time-based data point (i.e., timestamp), a gauge identifier (ID), a gas duct diameter, a reference strain gauge identifier, and the distance between the reference strain gauge and the strain gauge in question. The processing platform is configured to perform preprocessing on all or part of the data from the strain gauges, specifically resynchronizing the pressures measured by the strain gauges.The processing platform is configured to further process all or part of the data from the strain gauges to determine the gas flow rate(s) circulating in the gas pipe(s), in particular in the first secondary pipe and the second secondary pipe. The processing platform is configured to display 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 in question.

[0012] The invention will now be better understood through the following detailed description, given by way of illustration but not limitation, with reference to the attached figures, among which: Fig. 1 diagram shows a medical gas distribution installation in a hospital supplied by a gas source, including a monitoring system comprising strain gauges according to the invention. Fig. 2 diagram shows a connected strain gauge that allows for non-invasive measurement of the local pressure in a conduit delivering medical gas.

[0013] Fig. 1 diagram shows an embodiment of a gas distribution installation 100 supplying medical gas(s), in particular oxygen (of medical / medicinal grade), 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.

[0014] Installation 200 includes a gas source 1, namely a storage tank 11 for liquid oxygen (LOX) supplying 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. For the sake of simplicity, the gas supplied by gas source 1 is considered to be oxygen, but in other embodiments, it could be another medical-grade gas, such as nitrous oxide (N2O), air, etc.

[0015] 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 11. The measurement means 14 cooperates with the telemetry unit 13 to provide it with the LOX level measurements.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] The upstream portion 21 of the main supply line 2 has a first diameter D1 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 D1 is equal to several tens of millimeters, for example at least 40 mm.

[0020] 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 diesel fuel at a given pressure. In other words, the pressure regulator 23 guarantees, i.e., provides, a stable diesel fuel 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.

[0021] 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.

[0022] 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, approximately 15 mm. According to one embodiment, we have: D2 <D1 et D3<D1 (avec par exemple D2 = D3).

[0023] The first secondary conduit 31 itself has a plurality of sub-branches 311-31n, respectively, forming gas lines terminating at wall-mounted oxygen outlets 411 to 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.

[0024] 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.

[0025] 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 medical devices connected to wall outlets 411 to 41n, 321-32n malfunctioning and endangering patients.

[0026] 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 (e.g., 75% utilization), and the gas flow rate consumed through each of the operating wall outlets. 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, we can determine that a diameter D2 of 15mm should allow compliance with the requirements of the ISO 7396-1 standard, 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).

[0027] The same applies to the sizing of the second secondary conduit 32, which supplies 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.

[0028] Under unusual or exceptional conditions, such as an influx of COVID patients or other emergencies, the utilization rate of wall outlets 411-41n can reach 100%. Furthermore, 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 GOX flow rate in the first secondary conduit 31 of approximately 420 L / min, 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 proportionally to 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 of medical devices connected to the various wall-mounted O2 outlets 411-41n of the intensive care unit 4 considered.

[0029] We can then understand the importance of being able to operate effective monitoring of the gas distribution network 2, 3, in particular of the secondary conduits, 31, 32, namely here 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.

[0030] To achieve 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 .

[0031] Fig. 2 diagram shows an embodiment of such a non-invasive connected 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.

[0032] 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.

[0033] The strain gauge 6 includes 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 mechanical stress, particularly in the event of deformation of the wall 90 of the gas conduit 9 to which it is fixed.

[0034] Deformations of the resistive track 62 modify its resistivity R (also called resistance R) relative to a resting resistive value R0 depending on the deformation undergone, i.e., depending on whether the resistive track 62 undergoes compression (R<R 0 ) 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.

[0035] A telecommunications module 66 is also provided, arranged within 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 can be independent and configured to cooperate with the electronic board 64.1, particularly to retrieve the data to be transmitted.

[0036] 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.

[0037] The telecommunications module 66 is also capable of transmitting data, for example via cellular or other means, 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.

[0038] 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, 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.

[0039] 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.

[0040] 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 secured to the strain gauge 6 by gluing, welding or the like, in particular secured to the deformable support 61.1 carrying the resistive track 62.

[0041] Duct 9 is typically a copper alloy duct 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 ducts 31 and 32. Fig. 2 Indeed, the diameters of medical gas pipes are standardized (EN 13348) and there are therefore only a limited number of possible diameters, among which the 15 mm diameter is the most used for secondary pipes in hospital networks.

[0042] When the medical gas, here O2, flows at a given pressure P, for example 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 alloy (cf. Young's modulus and Poisson's ratio).

[0043] More specifically, the relationship linking the gas pressure P to a given conduit is given by the following formula: P = 8 . E . Δ Di . t Di 2 . 2 − v Or : P is the pressure in Pa E is Young's modulus in GPa Di is the internal diameter of the conduit in mm Δ Di is the deformation of the duct, 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.

[0044] As explained above, any gas distribution network in a hospital setting 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.

[0045] The Cu-DHP copper alloy is a deoxidized copper-phosphorus alloy ( Phosphorus-Deoxidized Copper (in English) which contains a phosphorus content usually between 0.013% and 0.040% by weight.

[0046] Thus, regarding the internal / external diameters and 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.

[0047] The external diameter and wall thickness information for 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.

[0048] These dimensional parameters (i.e. external and / or internal diameters and wall thickness) can be used when setting up strain gauges and stored within the control unit 64, for example within storage means of unit 64, in particular within its processor or a dedicated memory, such as a flash memory.

[0049] 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, notably 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.

[0050] 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 R0 of the resistive track 62, i.e., a reference resistance value R0.

[0051] 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.

[0052] Preferably, the database is obtained beforehand, for example during the manufacturing process of gauge 6 or subsequently via routine tests, by correlating resistive values ​​R of the resistive track 62 with different diameters of gas pipes subjected to different pressures, for example from 0 bar relative (i.e., atmospheric pressure) to 10 bar relative. R0 denotes the resistance value corresponding to a gas pipe subjected to atmospheric pressure (1 atm = 0 bar relative).

[0053] For example, all the conduits referenced in NF EN-13348, i.e. of different diameters and wall thicknesses, can be used to build the database and make it an exhaustive database.

[0054] We note 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 "elasticity").

[0055] However, the value of this coefficient depends on the alloy in question, 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 within the conduit.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] Advantageously, after being positioned on the gas pipe 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's or similar device's communication means to the communication module 66, as already explained.

[0060] The aforementioned database is generated at a given control temperature T0. However, in real-world conditions, the temperature T prevailing in a given conduit may differ from this control temperature T0, which can introduce bias into the measurement results. Indeed, all materials naturally tend to expand or contract under the effect of temperature (i.e., thermal expansion). Therefore, in one embodiment, a temperature sensor can be added to the various strain gauges to correct for the effect of ambient temperature (relative to the control temperature T0) in order to improve the accuracy of the measurements.

[0061] Strain gauges 6, 6a, 6b of Fig. 1 , which function as described above in connection with Fig. 2 , allow monitoring of different points of the gas network 2, 3. Typically, strain gauge 6 serves as a reference gauge.

[0062] 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 7 or similar device, 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 possibly other useful information, in particular time data, i.e. a timestamp.

[0063] 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.

[0064] In general, 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.

[0065] Data transmission can be done at a given frequency, for example every 10 milliseconds or at another suitable frequency.

[0066] On Fig. 1 We have schematically represented 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 on the number of pipes to be monitored, for example.

[0067] In Fig. 1 The connected strain gauges 6, 6a, 6b are arranged here as an example in the region of branch site 24b of the main conduit 2 (i.e., strain gauge 6) and also on the first and second secondary conduits 31, 32 (i.e., strain 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, with 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.

[0068] These strain gauges 6, 6a, 6b, and 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 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.

[0069] As an example, the data relating to each of the connected strain gauges 6, 6a, 6b to the processing platform 8 can be sent in the form of data packets: Reference gauge 6: [T, J1, Di1, P1, 0, 0] First additional gauge 6a: [T, J2, Di2, P2, RefJ1, L1] Second additional gauge 6b: [T, J3, Di3, P3, RefJ1, L2] Or : T is a time value, i.e., a timestamp, for example in the form DD / MM / YY XXhXXminXXsXXms. J1, J2, J3 are the unique identifiers (IDs) of gauges 6, 6a, 6b. Di1, Di2, Di3 are the diameters of the medical gas lines on which gauges 6, 6a, 6b are installed. P1, P2, P3 are the local pressures in the lines at the level of the gauges 6, 6a, 6b under consideration. RefJ1 is the identifier of the reference strain gauge 6 (ID = J1) to which the additional strain gauges 6a, 6b are paired. L1, L2 are the distances (in meters) between the additional strain gauges 6a, 6b and the reference gauge 6.

[0070] Since the reference strain gauge 6 is preferentially a reference gauge for other strain gauges, i.e. here the additional strain gauges 6a, 6b, it is not paired with any other connected strain gauge, therefore its pairing is designated by "0" and its relative location is also designated by "0" in the data packet that concerns it.

[0071] As an illustrative example, the pressure at the reference strain gauge 6, i.e. at the downstream end 24b of the downstream portion 24, is considered to be 4.5 bar, while the pressure in the first secondary conduit 31 at the strain gauge 6a is 4.2 bar, and that in the second secondary circuit 32 at the strain gauge 6b is 3.8 bar.

[0072] The resistive track 62 of 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: 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.

[0073] 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. Tab. 1 Jauge Horodatage ID Di (mm) P (bar) Réf. L (m) 6 14 / 4 / 2000 J1 13 4.5 0 0 10h40mn37s150ms 6a 14 / 4 / 2000 J2 13 4.2 J1 50 10h40mn37s150ms 6b 14 / 4 / 2000 J3 13 3.8 J1 30 10h40mn37s150ms

[0074] 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 circulating in the internal diameter Di of a given conduit causes a pressure loss which is a function of the nature of the medium (in the example here of gaseous O2), the diameter of the conduit, the length of the conduit and the flow rate circulating in the conduit considered.

[0075] 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 instance, the Wikipedia article on this equation: https: / / en.wikipedia.org / wiki / Darcy%E2%80%93Weisbach_equation.

[0076] Advantageously, preprocessing can be performed on the processing platform 8 by resynchronizing the pressures measured by the connected strain gauges 6 and 6a. Indeed, under the influence 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 and 6a. Since the distance separating these gauges is 30 meters and the speed of sound is approximately 330 m / s, the pressure at the connected strain gauge 6a is established after a latency 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 not to return erroneous flow values ​​circulating in the medical gas distribution network.

[0077] By exploiting the data returned by strain gauges 6, 6a, 6b, it is possible to determine, in 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.

[0078] Estimating flow rates in sections of the medical gas distribution network is not limited to straight, i.e., linear, sections. Indeed, the equation that transforms pressure loss into flow rate can take into account potential changes in cross-section, the presence of bends, etc.

[0079] Using strain gauges attached to the gas lines of the network is advantageous because their installation on existing networks does not require interrupting the lines of the hospital installation network, regardless of the network sites chosen for their installation, and therefore ensures continuity of gas supply, in particular oxygen supply to patients who need it.

[0080] Based on 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 under consideration, in order to warn of the imminence of network saturation and thus allow the operator to take appropriate protective measures.

[0081] 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 pipes 31, 32, 24 of the hospital gas network in order to estimate the pressure prevailing in these pipes 31, 32, 24.

[0082] 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 consumption of medical gases at different places in the gas distribution network, that is to say to obtain an approximation of the flow rate(s) circulating in the network.

[0083] 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 resting resistive value R 0 corresponding to a conduit of similar diameter at rest (e.g. at atmospheric pressure), which resting resistive value R 0 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.

[0084] As previously mentioned, all ducts referenced in NF EN-13348, i.e., those of various diameters and wall thicknesses, can be used to build the database and make it comprehensive. For example, diameters between 6 and 108 mm and thicknesses between 0.7 and 2.5 mm.

[0085] However, even minor variations may exist between the samples considered (i.e., test ducts) during the database creation process, and between the gas ducts in the gas network on which the strain gauges are placed. Such variations occur during the manufacturing process of the pipes and result in "tolerances" (i.e., small variations) around, in particular, the internal diameter and wall thickness of the ducts in question.

[0086] Thus, the pressure value returned by a given strain gauge 6, 6a, 6b, although close to the "real" pressure value in the conduit, is tainted by an error, for example a measurement of 3.9 bar instead of the 4 bar actually present.

[0087] 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.

[0088] 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 pipe (i.e., identical properties at both pipe locations), the second gauge 6a might 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.

[0089] However, the calculation of the flow rate in the gas pipe(s) depends on the absolute pressure values. The reported flow rate, although representative of the actual flow rate, may contain an error.

[0090] 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.

[0091] As already mentioned, LOX quantity measurement means 14 determine, preferably continuously, the LOX level (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.

[0092] After installation of the various strain gauges 6, 6a, 6b and receipt of the first data / measurements, a first calibration phase is carried out.

[0093] 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 around 8 hours.

[0094] During this analysis, the algorithm of control unit 64 performs various operations during the considered time period. In particular, the algorithm determines the volume of O2 injected into the medical gas piping network by considering the difference in LOX (i.e., gas in liquid form) level over the considered time period (using as a reference the dimensions of tank 11, which are also transmitted to control unit 64).

[0095] 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 around 2% of the useful volume, i.e. injected into the medical gas pipeline network.

[0096] 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 gas consumption, e.g. GOX, by all services consuming medical gases.

[0097] Adding the flow rates over the given period of time allows us to determine the total volume of gas delivered to the hospital's wall distribution outlets via the various gas lines of the hospital network.

[0098] 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 vaporizing LOX, during the given period of time.

[0099] Any significant difference, i.e. greater than a given threshold, for example at least 10%, triggers the implementation of a correction corresponding to the difference that has been determined.

[0100] 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 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.

[0101] The algorithm implemented by 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.

[0102] 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 them an overview of gas consumption within the gas network in question.

[0103] Such a calibration phase may optionally be repeated after a given period of time, for example every week, to ensure that the gauges have not suffered measurement deviation or 'sensor drift', for example after a few weeks or months of use.

[0104] 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 this network, that is to say that the installation of the strain gauges is carried out on gas pipes which can remain under pressure and continue to carry gas, such as oxygen, due to the lack of need to interrupt the gas supply to patients.

[0105] 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. Medical gas distribution system (100) comprising: - a gas distribution network (2, 3) configured for installation within a hospital, comprising a main gas line (2) branching into several secondary gas lines (3; 31, 32) carrying gas, - a gas source (1) comprising a gas reservoir (12) containing gas in liquid form fluidly connected to the main gas line (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) considered 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).

2. Installation according to claim 1, characterized in thatThe 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 flowed in the first secondary conduit (31) and / or in the second secondary conduit (32), during 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 that have been measured by the gas quantity measuring means (14) during said given period of time.

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 claim 4 or 5, characterized in that the given threshold value (Vs) is 10%.

7. Installation according to claim 1, characterized in that the gas tank (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) includes 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.

11. Installation according to claim 1, characterized in that The gas pipes have a diameter between 10 and 50 mm, preferably around 15 mm.

12. Installation according to claim 1 or 11, characterized in that The gas pipes are made of copper alloy.

13. Installation according to claim 1, characterized in that the control unit (64) includes at least one (micro)processor.

14. Installation according to claim 1, characterized in that The control unit (64) cooperates with a telecommunications module to ensure data transmission to at least one remote data processing platform.

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

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