NO supply facility to provide backup flow in case of flow sensor malfunction

Abstract

Title of the invention NO supply installation for providing an emergency flow rate in the event of a flow sensor malfunction The invention relates to an installation (100) for supplying a gas mixture containing NO comprising an NO delivery apparatus (1) connected to a breathing circuit (20; 21) with an injection device (24) and a flow sensor (25) for measuring the flow rate of breathing gas. The NO delivery apparatus (1) comprises a gas circuit (200) with flow control means (220, 221) for controlling the gas flow rate in the internal gas circuit (200), and control means (210) for determining a set flow rate of gas containing NO and controlling the flow control means (220, 221); and storage means (212) for storing successive set flow rates.In the event of an interruption in the transmission of the flow rate measurements carried out by the flow sensor (25), the control means (210) control the flow rate control means (220, 221) to supply the gas at an emergency flow rate calculated from the stored set flow rates. Abstract figure: Figure 2.

Description

Title of the invention: NO supply installation for providing an emergency flow rate in the event of a malfunction of the flow sensor

[0001] The invention relates to an installation for supplying a NO-based gas mixture to a patient, typically an NO / nitrogen (N2) mixture, comprising an NO delivery apparatus capable of delivering an emergency NO flow rate in the event of a malfunction resulting in an interruption of transmission by the flow sensor to the control means of the NO delivery apparatus, of any measurement of the flow rate of oxygen-based respiratory gas, such as air or an NO / N2 mixture, coming from a medical ventilator, typically a respiratory gas coming from a medical ventilator, i.e. in the event of loss of the flow rate signal.

[0002] Inhaled nitric oxide (NO or NOi) is a gaseous drug commonly used to treat patients suffering from acute pulmonary arterial hypertension, in particular pulmonary vasoconstrictions in adults or children, including newborns (PPHN), as described for example by EP-A-560928 or EP-A-1516639.

[0003] To implement inhaled NO therapy, a gas supply installation, also called a NO administration installation, is used, comprising an NO delivery device and a medical ventilator, i.e. a respiratory assistance device, supplying a patient circuit. The NO delivery device makes it possible to inject a gas mixture based on NO, typically an NO / nitrogen mixture, into the patient circuit also supplied with a gas flow containing oxygen (at least approximately 20% vol.), such as air or an oxygen / nitrogen mixture (O2 / N2), supplied by the medical ventilator. The patient circuit generally comprises one or more flexible conduits fluidically connected to a respiratory interface, such as a tracheal intubation tube or the like, used to deliver to the patient to be treated, a therapeutic gas mixture containing a given quantity or dose of NO, i.e. a dosage, typically between 5 and 40 ppmv of NO.

[0004] Such a gas supply installation is described for example by EP3821929. This type of installation is used in a hospital environment to administer NO treatment and thus treat patients who need to inhale NO to treat their pulmonary arterial hypertension.

[0005] Installations of this type are also described by EP4209243, EP4241817, EP4241812 and EP4295882.

[0006] In order to be able to provide a therapeutic gas mixture to patients containing an NO content corresponding to the desired dosage, the NO delivery apparatus must comprise means or a flow control system making it possible to control or adjust the flow rate of NO / N2 supplied, for example a system including one or more proportional or similar valves controlled by means of the device's control.

[0007] However, the flow rate of NO / N2 to be supplied depends in particular on the flow rate of respiratory gas (i.e. air or O2 / N2) coming from the medical ventilator.

[0008] Therefore, a flow sensor arranged in the respiratory circuit between the medical ventilator and the injection site of the NO / N2 mixture is usually used to carry out (quasi-)continuous measurements of the respiratory gas flow rate. These flow rate measurements are then transmitted to the control means which use them to calculate a set NO flow rate which is used to control the flow control means, typically one or more proportional valves, or others.

[0009] However, during the use of an NO supply installation, it happens that the measurement of the respiratory gas flow rate by the flow sensor is disturbed, defective or impossible to carry out, for example in the event of malfunction or accidental disconnection of the flow sensor, then causing an interruption in the transmission of the flow rate measurements by the flow sensor.

[0010] This interruption in the transmission of flow measurements poses a major safety problem for the patient because in the absence of flow measurement, the control means can no longer calculate the set NO flow rate which is used to control the flow control means, therefore the delivery of NO is done incorrectly or may even be interrupted.

[0011] To avoid this, the device must be able to supply NO to the patient at the desired dosage, by switching to a so-called "emergency" or "emergency dosage" supply mode, in which the set NO flow rate is calculated even in the absence of flow rate measurement, i.e. even in the event of interruption of the transmission of flow rate measurements by the flow sensor to the control means.

[0012] Thus, EP3233171 proposes to provide a predetermined fixed flow rate of NO / N2 mixture in the event of detection of an interruption in the transmission of the flow measurements by the flow sensor. This is not precise and leads to significant fluctuations in the NO content of the combined gas mixture since the flow rate of NO / N2 is fixed while that of the respiratory gas flow, into which the flow rate of NO / N2 is injected to form the combined gas mixture, varies over time.

[0013] Furthermore, EP3410927 proposes storing a history of flow measurement values ​​operated by the flow sensor and using this history of stored values ​​to calculate the set NO / N2 flow rate, in the event of an interruption in the transmission of the flow measurements. This solution is not ideal because the stored “raw” flow values ​​may be erroneous, in particular in the event of an intermittent malfunction of the flow sensor which may, for example, result from untimely electrostatic discharges on the sensor, leading to incorrect breathing gas flow values ​​being stored. Since the flow values ​​are incorrect, the flow calculations using them are also incorrect, resulting in the supply of an inadequate quantity of NO / N2.

[0014] Furthermore, EP3410927 proposes using an additional NO sensor to measure the flow rate of NO / N2 supplied by the device over time and to store a history of the NO flow rate measurements made by the additional NO sensor. In the event of an interruption in the transmission of the respiratory gas flow rate measurements by the respiratory gas sensor, the device uses the history of stored NO flow rate values ​​to set the set NO / N2 flow rate. Here again, the solution is not ideal because it complicates the overall architecture of the device by requiring the incorporation of an additional sensor. In addition, working on the historical values ​​of delivered NO has disadvantages since these flow rate values ​​may be erroneous, due for example to a signal / noise ratio of measurement that is too high, in particular for delivered NO values ​​that are very low (i.e. ppmv).

[0015] A problem is therefore to propose an improved NO delivery installation, making it possible to determine a set NO flow rate, in the absence of a respiratory gas flow rate measurement, i.e. in the event of interruption of the transmission to the control means (i.e. loss of the respiratory flow rate signal), of the respiratory gas flow rate measurements carried out by the flow sensor, so as to be able to supply a final NO-based gas mixture to the patient containing a proportion of NO equal to or close to a dosage set by a healthcare personnel, i.e. a doctor or the like.

[0016] A solution of the invention relates to an installation for supplying a gas mixture containing NO to a patient comprising: - an NO delivery device supplied with a gas containing NO in a given initial proportion, typically an NO / N2 mixture, and configured to supply the gas containing NO, - a breathing circuit comprising an injection device configured to operate a mixture of the gas containing NO coming from the NO delivery device with a flow of breathing gas containing O2 conveyed by the breathing circuit, and to obtain a combined gas mixture containing NO and oxygen, and - a flow sensor configured to measure at least one respiratory gas flow rate within the breathing circuit and provide at least one respiratory gas flow rate measurement,

[0017] and wherein the NO delivery apparatus comprises: - an internal gas circuit to convey gas containing NO, - primary and secondary flow control means configured to control (i.e. authorize, prevent / prohibit, adjust, etc.) the flow of gas containing NO conveyed by the internal gas circuit, - (micro)processor control means configured for: • determine at least one set flow rate of gas containing NO to be supplied to the injection device, from at least one measurement of respiratory gas flow rate carried out by the flow sensor, and • control at least part of the main and secondary flow control means to supply the gas containing NO at the set flow rate having been determined, - and storage means.

[0018] Furthermore, in said installation for supplying a gas mixture containing NO (i.e. nitrogen monoxide), such as a NO / N2 mixture: - the storage means are configured to store successive set flow rates of gas containing NO having been determined by the control means, and - in the event of an interruption in transmission to the control means of any measurement of respiratory gas flow rate by the flow sensor (i.e. in the event of loss of the respiratory flow rate signal), the control means are configured to control the main and / or secondary flow rate control means to supply the gas containing NO at an emergency flow rate obtained or calculated from one or more set flow rates of gas containing NO having been determined by the control means and stored by the storage means, before said interruption in transmission.

[0019] Depending on the embodiment considered, the installation of the invention may comprise one or more of the following characteristics: - the control means are configured to determine successive set flow rates of gas containing NO from several successive respiratory gas flow measurements carried out by the flow sensor and supplied to said control means. - the storage means are configured to store the successive NO-containing gas set flow rates determined by the control means. - the emergency flow rate is obtained or calculated from several set flow rates having been determined by the control means for a given duration (dt), before said transmission interruption, i.e. successive flow rates determined during normal operation of the device. the emergency flow rate is calculated by taking an average of the set flow rates stored during the given duration (dt). the given duration (dt) is less than or equal to 30 seconds, preferably less than or equal to 20 seconds, more preferably less than or equal to 10 seconds. the given duration (dt) is fixed or, according to another embodiment, modifiable. the given duration (dt) is stored. the control means are configured to determine said at least one set flow rate of gas containing NO to be supplied to the injection device, from at least one measurement of respiratory gas flow rate carried out and supplied by the flow sensor, from a set NO content corresponding to the final proportion of NO desired (i.e. a dosage) in the combined gas mixture, and from the initial proportion of NO in the gas containing NO supplying the NO delivery device. the initial proportion of NO in the NO-containing gas supplying the NO delivery device is stored in the storage means. in the event of interruption of transmission to the control means of any measurement of respiratory gas flow rate by the flow sensor (i.e. in the event of loss of the respiratory flow rate signal), the control means are configured to control the main flow rate control means (i.e. which remain operational, i.e. the main flow rate control means which do not malfunction) to supply the gas containing NO at said emergency flow rate. when the main flow control means continue to operate normally (i.e. do not malfunction), despite the interruption of transmission of the flow measurements (i.e. in the event of loss of the respiratory flow signal), the gas containing NO passes through the main line comprising the main flow control means which are controlled by the control means in order to supply the gas containing NO at said emergency flow. conversely, in the event of an interruption in the transmission to the control means of any measurement of the respiratory gas flow rate by the flow sensor and, furthermore, of a malfunction of the main flow control means (therefore of the main flow control means being non-operational or out of service), the control means are configured to control the control means secondary flow rates (to make them operational) to supply the gas containing NO to said emergency flow rate. when the main flow control means are not operating normally, i.e. are malfunctioning, with further interruption of transmission of flow measurements (i.e. in the event of loss of the respiratory flow signal), the gas containing NO passes through the secondary line (and no longer through the main line) comprising the secondary flow control means which are controlled by the control means in order to supply the gas containing NO at said emergency flow. the flow sensor is arranged within the respiratory circuit, upstream of the injection device. the NO delivery apparatus is supplied with a gas containing an initial proportion of NO of between 100 and 1500 ppmv, typically between 200 and 1000 ppmv. The NO delivery device is supplied with a gas mixture of nitrogen and NO. the NO delivery apparatus comprises dose adjustment means configured to allow a user to set or select the NO content setpoint corresponding to the final proportion of NO desired in the combined gas mixture, i.e. a dosage. The dose adjustment means are part of an HMI (human-machine interface) or GUI (graphical user interface). the dose adjustment means comprise one or more touch keys, operable by the user, displayed on a digital touch screen of the HMI The HMI screen is of the color display type. the NO content setpoint is between 1 and 80 ppmv, typically between 5 and 40 ppmv. it comprises a medical ventilator configured to supply the flow of respiratory gas containing O2 to said breathing circuit. the medical ventilator is configured to provide a flow of breathing gas containing at least about 20% vol. O2, typically an NO / N2 mixture or air. The NO delivery device and the medical ventilator are fluidically connected to the breathing circuit. The flow sensor is arranged in the breathing circuit between the medical ventilator and the injection device. the injection device comprises a first gas inlet supplied with a flow of respiratory gas containing O2, i.e. coming from the medical ventilator. the injection device further comprises a second gas inlet supplied with gas containing NO at said set flow rate, i.e. coming from the NO delivery device. the injection device further comprises a gas outlet providing the combined gas mixture containing NO and oxygen, obtained by mixing, within the injection device, the gas containing NO (eg NO / N2 mixture) with the flow of respiratory gas containing O2 (eg air or O2 / N2 mixture). the storage means include computer memory, such as flash memory, RAM or the like. the control means are configured to detect any interruption in the transmission of respiratory gas flow measurements by the flow sensor to the control means. the control means are configured to detect any interruption in the transmission of the respiratory gas flow measurements made by the flow sensor, i.e. any loss of the respiratory flow signal. the NO delivery apparatus operates in at least two operating modes comprising a normal operating mode and an emergency operating mode, i.e. an emergency mode. the NO delivery device is configured to automatically switch from normal operating mode to emergency mode in response to an interruption in the transmission of respiratory gas flow measurements made by the flow sensor (i.e. in the event of loss of the respiratory flow signal), with or without malfunction of the main flow control means, in particular the main valve means. detection by the control means are configured to detect any interruption in the transmission of respiratory gas flow measurements and / or any malfunction of the main flow control means the control means are configured to activate the emergency mode in the event of interruption of transmission of respiratory gas flow measurements (i.e. in the event of loss of the respiratory flow signal). the control means are configured to determine successive set flow rates of gas containing NO from successive respiratory gas flow measurements carried out by the flow sensor during normal operation of the NO delivery device, i.e. when it operates in the normal operating mode. the control means are configured to control the main and / or secondary flow control means to supply the gas containing NO at the emergency flow rate, during operation of the NO delivery apparatus in emergency mode. the control means are configured to determine and store the successive set flow rates of gas containing NO during normal operation of the NO delivery device. the internal gas circuit comprises two gas sections arranged in parallel comprising a main section and a secondary or emergency section. the main and secondary sections include main and secondary flow control means, typically main and secondary valve means, such as solenoid valves or the like. the control means are configured to control the main and secondary flow control means to authorize or prevent the passage of the NO / N2 flow in one or other of the main and secondary sections, in particular depending on the operating mode of the NO delivery device. in normal operating mode, the control means are configured to control the main and / or secondary flow control means so that the NO / N2 flow passes only through the main section. in emergency mode, the control means are configured to control the main and / or secondary flow control means so that the NO / N2 flow passes through the main section or, as the case may be, through the emergency section depending on whether the main flow control means are operating or, on the contrary, are malfunctioning, respectively. the primary and secondary flow control means include primary and secondary valve means, such as solenoid valves. The main flow control means include a proportional solenoid valve. the secondary flow control means comprise an on / off solenoid valve, preferably piloted in pulsed mode. The main means of flow control include a mass flow controller. - the mass flow controller (MFC) comprises at least one proportional solenoid valve controlled by the control means and a main flow sensor. - the main flow sensor is integrated into the structure of the MFC proportional solenoid valve. - the MFC solenoid valve also has an electronic microprocessor card implementing at least one algorithm. - the secondary section, i.e. the emergency section, includes a device with a calibrated orifice used to control the flow of gas circulating in the secondary section, in particular in emergency mode. - the calibrated orifice device is arranged downstream of secondary flow control means of the secondary section. - the secondary flow control means of the secondary section comprise secondary valve means, typically a solenoid valve, preferably of the all-or-nothing (ONT) type. - the all-or-nothing (TOR) solenoid valve is controlled by the control means, preferably in pulsed mode. - the main section includes one (or more) proportional solenoid valves and the secondary section includes one (or more) all-or-nothing (ON) type solenoid valves. - the main section includes one (or more) proportional solenoid valves which are normally closed. - in normal operation, the proportional solenoid valve is controlled to be at least partially open (i.e. proportional opening) and allow gas containing NO to pass through.

[0020] in normal operation, the TOR solenoid valve is closed or controlled by the control means to be closed, and to prevent any passage of gas containing NO, i.e. to prevent the circulation of gas. - in the event of a malfunction of the main flow control means, typically the MFC, the proportional solenoid valve closes automatically or, as the case may be, is controlled to close, so as to prohibit, stop or prevent any flow of gas. - in the event of a malfunction of the main flow control means, typically the MFC, the TOR solenoid valve opens automatically or is controlled to be opened (i.e. to open), so as to authorize or permit a passage of gas (eg NO / N2) in the secondary section. - the control means include a (micro)controller or similar. - the control means comprise one (or more) (micro)processors arranged on one (or more) electronic card. - the control means comprise one (or more) (micro)processors implementing one or more algorithms, in particular one (or more) algorithms for controlling the main and / or secondary flow control means, one (or more) algorithms for processing the respiratory gas flow measurements.... - the storage means are arranged on the electronic card.

[0021] Furthermore, depending on the embodiment considered, the gas supply installation of the invention may comprise one or more of the following additional features: - the medical ventilator delivers air or an oxygen / nitrogen mixture, i.e. as a breathing gas containing at least approximately 20% vol. of oxygen, preferably at least approximately 21% vol. of oxygen. - the medical ventilator comprises a motorized blower (i.e. turbine, compressor or the like) delivering the respiratory gas, typically air or an oxygen / nitrogen mixture or, according to another embodiment, an internal gas circuit comprising one or more proportional valves for conveying the gas and controlling its supply, in particular its flow rate. Such a ventilator is generally supplied with respiratory gas by one or more wall outlets supplied with gas by a network of pipes in a hospital establishment or building, typically air or an oxygen / nitrogen mixture. - the medical ventilator comprises control means or a device, such as one or more electronic control cards. Preferably, the control means of the medical ventilator control or operate the motorized blower or, as the case may be, the proportional valves of the medical ventilator. - the medical ventilator is of the HFO type or includes an HFO function, i.e. it is capable of producing high-frequency oscillations. - the NO source contains a NO / N2 gas mixture containing between 100 and 2000 ppmv of NO, the remainder being nitrogen (N2), preferably between 100 and 1000 ppmv of NO, conditioned at a pressure between 10 and 250 bar abs, typically at more than 100 bar abs (before the start of withdrawal). - the source of NO is or includes one (or more) gas cylinders with a capacity of between 0.5 and 50 L (water equivalent). - the gas cylinder(s) comprises a cylindrical body made of steel or aluminium alloy and is equipped with a simple valve (without regulator) or with an integrated regulator or RDI, preferably an RDI, protected by a protective cover, for example made of metal or polymer. - the breathing circuit of the installation comprises an inspiratory branch and an expiratory branch, typically flexible pipes forming the inspiratory branch and the expiratory branch, for example polymer pipes. - the inspiratory branch and the expiratory branch, e.g. flexible pipes, are connected to a junction piece, such as a Y piece. - the inspiratory branch and / or the expiratory branch are fluidically connected to a patient respiratory interface, preferably via the junction piece. - the patient respiratory interface includes a tracheal intubation tube or respiratory mask, or other. - the inspiratory branch and the expiratory branch are further fluidically connected to, respectively, outlet and inlet ports of the medical ventilator. - the respiratory circuit, in particular the inspiratory branch, may include a gas humidifier. - the gas humidifier is arranged downstream of the injection device, for example an NO injection module, so as to be able to humidify the gas before its administration by inhalation to the patient. - the ventilator and the NO delivery device are electrically powered by one or more electrical current sources, typically the mains (110 / 220V) and / or one or more rechargeable batteries.

[0022] According to another aspect, the invention also relates to a method for the therapeutic treatment of a person, i.e. a human patient (i.e. adult, child, adolescent or newborn), suffering from pulmonary hypertension and / or hypoxia, causing pulmonary vasoconstrictions or the like, comprising administration by inhalation to the person in need thereof, of a gas mixture comprising from 1 to 80 ppmv of NO and at least approximately 20% vol. of oxygen, preferably at least approximately 21% vol. of oxygen, by means of a gas supply installation, such as that described above according to the invention, comprising an NO delivery apparatus ensuring delivery of NO at an emergency flow rate compatible with the desired dosage, even in the event of a malfunction preventing any exchange of measurements between the flow sensor measuring the flow rate of the oxygen-based respiratory gas supplied by the medical ventilator (egair or N2 / O2) and the means for controlling the NO delivery device, so as to treat (at least partially) said pulmonary hypertension and / or said hypoxia, which may be caused by one (or more) pathology or other pulmonary disorders typically of the PPHN type (persistent pulmonary hypertension of the newborn) or ARDS (distress syndrome). acute respiratory), or caused by cardiac surgery with the patient being placed on extracorporeal circulation (ECC).

[0023] Definitions

[0024] Generally speaking, within the framework of the invention: - “ppmv” means parts per million by volume, - “%vol.” means percentage by volume. - “NO” means nitrogen monoxide. - “NO2” means nitrogen dioxide. - “N2” means nitrogen. - “O2” means oxygen. - the terms “concentration”, “quantity”, “proportion”, “dose” and “content” are considered equivalent. - the terms "means of / to / for" are considered to be completely equivalent and substitutable by the terms "device of / to / for", for example the terms "control means" can be replaced by "control device", the terms "valve means" can be replaced by "valve device", the "memorization means" can be replaced by "memorization device" ... - by "normal operation" or "normal operating mode" is meant normal operation of the NO delivery device in the absence of any malfunction hindering or preventing a supply (i.e. interruption of transmission or loss of flow signal) to the means of controlling the NO delivery device, of flow measurements (i.e. values ​​or signals) by the flow sensor measuring the flow of the respiratory gas (i.e. air or N2 / O2) conveyed by the respiratory circuit, typically coming from the medical ventilator. - “malfunction” means a breakdown, anomaly, a problem, a defect, an accidental disconnection or any technical problem, such as electromagnetic disturbances, affecting the normal operation of the NO delivery device by preventing the supply to the control means and / or the reception by said control means (i.e. interruption of signal transmission or loss of flow signal), of the flow measurements made by the flow sensor measuring the flow of the respiratory gas (i.e. air or N2 / O2) conveyed by the respiratory circuit, typically coming from the medical ventilator. - by "flow measurement" we mean a flow value (e.g. a digital value) or a signal representative of such a flow value reflecting or corresponding to a gas flow rate measured by a flow sensor, such as a mass flow sensor. - by “pressure measurement” we mean a pressure value (e.g. a digital value) or a signal representative of such a pressure value reflecting or corresponding to the gas pressure measured by a pressure sensor (regardless of the operating mode of this sensor). - by "operation in emergency mode" is meant operation of the NO delivery device in the event of a malfunction hindering or preventing the supply (i.e. interruption of transmission of the flow signal or loss of the flow signal) to the control means of the NO delivery device, of the flow rate measurements of the respiratory gas flow (i.e. air or O2 / N2 mixture) carried out by the flow sensor, with or without any concomitant malfunction of the main flow control means (e.g. the proportional solenoid valve of the MFC) located on the main gas section.

[0025] The invention will now be better understood thanks to the following detailed description, given for illustrative but non-limiting purposes, with reference to the appended figures among which:

[0026] [Fig.l] shows schematically an embodiment of a gas administration installation according to the invention.

[0027] [Fig.2] shows a diagram of an embodiment of the internal architecture of the device NO delivery system of a gas administration installation according to the invention, in particular a gas administration installation according to [Fig.l].

[0028] [Fig.l] schematizes an embodiment of a gas administration installation 100 according to the invention comprising an NO 1 supply apparatus providing a gas mixture based on nitrogen monoxide (NO), and a medical ventilator 50 providing a gas containing at least 20% vol. of oxygen, such as air or other.

[0029] The installation 100 here comprises two pressurized gas cylinders 10 each containing a NO / N2 gas mixture, namely here a NO / N2 gas mixture containing between 100 and 1000 ppmv of NO (N2 remainder), for example 450 or 800 ppm vol. of NO (N2 remainder), or any other suitable concentration, which supply the NO / N2 mixture to the device or apparatus 1 for delivering or supplying NO, making it possible to monitor and control the supply of the NO / N2 gas mixture.

[0030] The gas bottles 10 are fluidically connected to the NO supply apparatus 1, via gas supply lines 12, such as flexible pipes or conduits or the like, which may be equipped with gas pressure regulating and / or monitoring devices, such as a gas regulator 13, pressure gauges, etc. The gas supply lines 12 are connected to one or more gas inlets 2 of the delivery apparatus of NO 1 which supply an internal gas circuit 200, as shown diagrammatically in [Fig.2], used to convey the gas within the NO 1 supply device, that is to say in the external housing or casing 1.1 of the device 1.

[0031] In the embodiment of [Fig.2], the internal gas circuit 200 is connected to two gas inlets 2 arranged in parallel and each supplying a dedicated inlet section 200.3 of the internal gas circuit 200. Control valves 222 or the like control the passage of the NO / N2 flow in these inlet sections 200.3.

[0032] The NO 1 delivery apparatus further comprises an oxygen inlet 3 fluidically connected, via an oxygen supply line 11, such as a flexible hose or the like, to an oxygen source (not shown), for example a pressurized oxygen cylinder or a hospital network, i.e. an oxygen supply pipe arranged in a hospital building. This makes it possible to supply the internal gas circuit 200 with oxygen when necessary.

[0033] The medical ventilator 50, i.e. a respiratory assistance device, provides a flow of oxygen-based respiratory gas, i.e. containing at least approximately 20% by volume of oxygen, preferably at least approximately 21% by volume of oxygen, such as air or an oxygen / nitrogen mixture (N2 / O2).

[0034] The medical ventilator 50 and the NO 1 supply apparatus of the installation 100 are in fluid communication with a respiratory circuit 20, also called a patient circuit, in particular with a gas supply line or inspiratory branch 21 of the respiratory circuit 20, which is used to convey the gas flow to the respiratory interface 40 supplying the therapeutic gas flow to the patient, i.e. a final gas mixture containing the desired NO dosage.

[0035] More precisely, the final gas mixture to be administered to the patient is formed by mixing the oxygen-based flow (e.g. air or NO / N2 mixture) coming from the medical ventilator 50 and the flow containing NO, i.e. the NO / N2 gas mixture, delivered by the NO 1 delivery device.

[0036] To do this, the NO 1 delivery device supplies or injects the NO / N2 mixture into the respiratory circuit 20, typically into the inspiratory branch 21, via a conduit or an injection line 23, fluidically connecting the internal gas circuit of the NO 1 delivery device to an injection device 24 arranged on the gas supply line 21.

[0037] The injection device 24 is configured to operate a mixture of the gas containing NO coming from the NO 1 delivery apparatus with the flow of respiratory gas containing O2 coming from the ventilator 50 and conveyed by the inspiratory branch 21 of the respiratory circuit 20, and to obtain a combined gas mixture containing NO and oxygen, that is to say the final gas mixture administered to the patient.

[0038] More specifically, the injection device 24 comprises a first gas inlet supplied with a flow of respiratory gas containing O2 coming from the medical ventilator 50, a second gas inlet supplied with gas containing NO, i.e. coming from the NO 1 delivery apparatus, and a gas outlet providing the combined gas mixture containing NO and oxygen, obtained by mixing, within the injection device 24, the gas containing NO with the flow of respiratory gas containing O2.

[0039] In other words, the flow of NO / N2 supplied by the injection line 23 then mixes (thanks to the injection device 24) with the flow of oxygen-based gas (> 20% O2), e.g. air or an oxygen / nitrogen mixture, delivered by the medical ventilator 50 and conveyed by the inspiratory branch 21 of the patient circuit 20 so as to obtain a final mixture, i.e. a combined mixture, to be administered to the patient containing essentially NO at the desired dosage, nitrogen (N2) and oxygen (O2), and possibly unavoidable impurities (e.g. argon, CO2, NO2, etc.), i.e. a final gas mixture no / n2 / o2.

[0040] The inspiratory branch 21 of the circuit 20 further comprises a gas humidifier 30 arranged downstream of the injection device 24. It makes it possible to humidify the final gas flow, e.g. the combined gas mixture NO / N2 / O2, before it is administered by inhalation to the patient to be treated, by means of a respiratory interface 40, such as a tracheal intubation probe, a respiratory mask or the like.

[0041] A line for recovering gases exhaled by the patient forms an expiratory branch 22 of the patient circuit 20. It is fluidically connected to the inspiratory branch 21 via a connecting piece 25, such as a Y-shaped piece.

[0042] The inspiratory branch 21 is, at its upstream end, fluidically connected to an outlet port 51 of the medical ventilator 50, such as a connector, fitting or the like, so as to recover and convey the oxygen-based gas, typically air or N2 / O2 mixture supplied by the medical ventilator 50, while the expiratory branch 22 conveying the exhaled gases is fluidically connected to an inlet port 52 of the medical ventilator 50, such as a connector, fitting or the like, so as to return to the medical ventilator 50 all or part of the flow of gases exhaled by the patient. The expiratory branch 22 may comprise one or more optional components, for example a CO2 removal device 35, i.e. a CO2 trap, such as a hot tank or the like, making it possible to remove the CO2 present in the gases exhaled by the patient, a filter or the like.

[0043] Furthermore, a flow sensor 25, for example of the hot wire or pressure differential type, is arranged on the respiratory circuit 20, in particular on the inspiratory branch 21, between the ventilator 50 and the injection device 24. The flow sensor 25 is connected to a sensor connection port 27 of the NO 1 delivery device, via one or more flow measurement lines 26 connecting to said sensor connection port 27. It is used to measure the flow rate of gas delivered by the ventilator 50, such as air or N2 / O2, circulating in the inspiratory branch 21, upstream of the injection device.

[0044] These flow rate measurements made by the flow rate sensor 25 make it possible to more effectively control or regulate the delivery of the NO (i.e. N2 / O2) flow by the NO 1 delivery apparatus, in particular the NO flow rate, since the flow rate measurements made by the flow rate sensor 25 are returned, via the flow rate measurement line 26 (i.e. electrical cables or the like) and the sensor connection port 27, to (micro)processor control means 210 of the NO 1 delivery apparatus, typically a controller, which process these flow rate measurements as explained below and illustrated in [Fig.2]. The sensor connection port 27 is electrically connected to the control means 210 via one or more electrical connections, for example electrical cables or the like.

[0045] The NO 1 supply apparatus comprises a rigid casing 1.1, for example made of polymer, comprising the internal gas circuit 200 on [Fig.2], typically gas lines, passages or conduits or the like, used to convey the flow of NO-based gas, i.e. the NO / N2 mixture, coming from the NO / N2 mixture cylinders 12. The internal gas circuit 200 fluidly connects the gas inlet (or inlets) 21 of the NO 1 supply apparatus to the injection line 23 so as to convey the flow of NO-based gas between them.

[0046] In the embodiment shown schematically in [Fig. 2], a portion of the internal gas circuit 200 comprises two gas sections arranged in parallel, namely a main section 200.1 and a secondary section 200.2, called the emergency section. The main section 200.1 and the secondary section 200.2 are fluidically connected to each other and to the rest of the gas circuit 200 at upstream 260 and downstream 261 connection sites located, respectively, upstream and downstream of the main and secondary flow control means 220, 221.

[0047] In this case, in normal operating mode, the flow of NO / N2 passes through the main section 200.1, whereas in the event of an interruption in signal transmission, it automatically switches to emergency mode, as explained below and: - if the main flow control means 220 remain operational, i.e. continue to operate normally, typically a mass flow controller or MFC, then the flow of NO / N2 continues to pass through the main section 200.1, - if the main flow control means 220 are rendered non-operational, i.e. dysfunctional, the flow of N0 / N2 is diverted and then passes through the emergency section 200.2.

[0048] Of course, according to another embodiment (not shown), the internal gas circuit 200 could be configured differently, for example comprising a single gas line instead of the two sections 200.1, 200.2, which would be used in normal operating mode and in emergency mode. However, in this embodiment, a malfunction of the main flow control means 220 could not be taken into account and the apparatus 1 would then become non-functional.

[0049] Generally speaking, the main and secondary flow control means 220, 221, such as main and secondary valve means 2200, 2210, shown diagrammatically in [Fig. 2], i.e. one or more valve devices, for example one or more proportional solenoid valves controlled by the control means 210, are arranged on the internal gas circuit 200, in particular on the main 200.1 and secondary 200.2 sections, and serve to control or adjust the gas flow which circulates therein towards the injection line 23, i.e. towards the injection device 24, whether in normal operating mode or in emergency mode.

[0050] Preferably, the main section 200.1 comprises a proportional solenoid valve 220 and an additional flow sensor 230, typically a mass flow controller or MFC, while the secondary section 200.2 comprises one (or more) all-or-nothing (TOR) type solenoid valves 221, preferably controlled in pulsed mode.

[0051] Preferably, the main and secondary flow control means 220, 221 of the NO 1 supply apparatus are controlled, i.e. monitored, by the piloting means 210, i.e. one or more piloting devices or (micro)controllers, arranged in the housing 1.1 of the NO 1 supply apparatus.

[0052] Typically, the control means 210 comprise one or more electronic cards comprising one or more microprocessors 211 implementing one or more algorithms. The control means 210 make it possible in particular to adjust or control the flow rate of NO-based gas by controlling all or part of the valve means 2200, 2210, typically to open or close one or more (electro)valves, to obtain a flow rate of NO-based gas, typically to authorize or stop the gas flow rate.

[0053] Of course, the control means 210 also make it possible to carry out calculations and / or to control or command all the electromechanical elements of the device 1, such as the sensors, the displays, etc.

[0054] As explained below, the control means 210 can determine the flow rate of NO to be supplied to obtain the desired NO content in the combined mixture, i.e. the desired NO dosage, based in particular on the NO content setpoint adjusted and / or set by the user, the composition of the NO / N2 gas mixture , in particular the NO content in this NO / N2 gas mixture, and one (or more) flow measurement(s) carried out by the flow sensor 25 arranged on the inspiratory branch 21 and connected by a flow measurement line 26 to the NO 1 supply device, in particular to the control means 210, via the sensor connection port 27.

[0055] The internal gas circuit 200 of the NO 1 supply apparatus may also comprise other elements or components, in particular one (or more) pressure sensor 250, one (or more) additional flow sensor or flow meter and / or calibrated orifice devices 240 or others. These other elements may be arranged upstream and / or downstream of the flow control means 220, 221, i.e. the valve means, for example an additional flow sensor may be used to determine the flow rate of NO-based gas circulating in all or part of the internal gas circuit 200, in particular to ensure that it complies with the desired flow rate.

[0056] Thus, in [Fig.2], we see that the main section 200.1 comprises an additional flow sensor 230 arranged upstream of the flow control means 220, such as valve means 2200, for example one or more solenoid valves, preferably a proportional solenoid valve, controlling the passage of gas in the main section 200.1. This assembly forms a mass flow controller (MFC).

[0057] Furthermore, the secondary section 200.2 comprises a calibrated orifice device 240 arranged downstream of secondary flow control means 221, such as secondary valve means 2210, preferably one or more solenoid valves, controlling the flow rate of gas passing through the secondary section 200.2.

[0058] Advantageously, the solenoid valve of the secondary flow control means 221 is of the all-or-nothing (TOR) type, i.e. capable of adopting 2 “stable” positions, namely an open position allowing the gas flow to pass and a closed position preventing any circulation of gas flow.

[0059] According to the invention, during an interruption in the transmission of the respiratory gas flow measurement signal, i.e. loss of the respiratory gas flow signal, but with the main flow control means 220 operational (MFC), i.e. which continue to operate normally, the NO / N2 flow continues to pass through the main section 200.1 and the control means 210 control the proportional solenoid valve 220, i.e. in proportional mode, to adjust and deliver the gas at the desired emergency flow rate. The on / off solenoid valve 221 (TOR) arranged on the secondary section 200.2 is then in the closed position. The device 1 is then in emergency mode but the NO / N2 flow continues to pass through the main section 200.1.

[0060] On the other hand, in the event of interruption of transmission of the respiratory gas flow measurement signal with simultaneous malfunction of the main flow control means 220 (i.e. of the MFC, for example of the proportional solenoid valve), the control means 210 then control (typically in pulsed mode) an opening of the all-or-nothing solenoid valve 221 (TOR) arranged on the secondary section 200.2 to allow the gas to pass into this secondary section 200.2 to deliver the gas at the desired emergency flow rate, while the proportional solenoid valve 220 is no longer controlled and goes into the closed position, which is preferably its default position. The device 1 is then also in emergency mode and the flow of NO / N2 no longer passes through the main section 200.1.

[0061] Furthermore, the additional flow meter or flow sensor 230 of the MFC may be of the pressure differential, mass or other type, and cooperates with the control means 210 to provide them with flow rate measurements of the NO / N2 flow.

[0062] Usually, the NO 1 supply device also comprises a graphical user interface or GUI comprising a graphical display 4, preferably a touch screen, i.e. a touch panel, used to display various information or data, icons, curves, alarms, etc., as well as virtual selection keys and / or blocks or windows, used in particular to make choices, selections or to enter information, such as desired values ​​(e.g. flow rate, NO dosage, etc.), or any other information or data useful to the healthcare personnel. Preferably, the display is in color but it can also be in black and white.

[0063] The electrical power supply of the NO 1 supply apparatus, in particular of the components requiring electrical current to operate, such as the control means 210, the graphic display 4, etc., is conventionally provided by a source of electrical current and / or electrical power supply means (not shown), for example a connection to the mains current (110 / 220V) of the electrical cord and connection plug type, and / or one (or more) electrical power supply batteries, preferably rechargeable, and / or a current transformer. The electrical power supply of the medical ventilator 50 is provided in a similar manner, in particular by a connection to the mains current or an internal battery.

[0064] Furthermore, the installation 100 also comprises a gas sampling line 60 which fluidly connects the inspiratory branch 21 to the NO 1 supply device. It is fluidly connected (at 61) to the gas supply line 21, between the humidifier 30 and the junction piece 25, i.e. the Y-shaped piece, typically in the immediate vicinity of the junction piece 25, and also to an inlet port 62 of the NO 1 supply device, for example a port 62 carried by a connector, fitting or the like, allowing the connection of the gas sampling line 60, such as a flexible pipe or the like. The gas sampling line 60 makes it possible to take gas samples and convey them to the NO 1 supply device where they are analyzed in an internal gas analyzer (not shown), that is to say within a calibration line comprising at least one sensor, in particular one or more electrochemical cells, electrically connected to the control means, in order to verify their conformity. In particular, it is necessary to verify that the composition of the final gas is consistent with that of the desired NO / N2 / O2 gas mixture to be administered to the patient, in particular to ensure that it does not contain an excessive quantity of toxic NO2 species, that its oxygen content is not hypoxic, that it does not contain too high a NO2 content and that its NO content corresponds to the desired dosage, i.e. dose of NO to be administered by inhalation which is usually chosen by the healthcare staff, i.e. doctor or similar. This conformity verification is conventionally carried out by means of dedicated measuring means, typically NO2, NO and O2 sensors, for example electrochemical cells or similar, which must themselves be calibrated periodically, for example every week.The control means 210 of the device 1 are further configured to recover and process, i.e. analyze, the signals coming from the different sensors of the gas analyzer, which is arranged in the device 1, and to act in response to these signals, in particular to carry out a calibration of the sensors.

[0065] In the context of the invention, in order to be able to determine a set NO flow rate, in the absence of a respiratory gas flow rate measurement, i.e. in the event of interruption of the transmission to the control means 210 or loss of signal, of the respiratory gas flow rate measurements carried out by the flow sensor 25, and therefore to be able to provide a final gas mixture based on NO, i.e. a combined mixture, to the patient containing a proportion of NO equal to or close to a dosage set by the healthcare personnel, i.e. a doctor or the like, the procedure is as follows.

[0066] The interruption of transmission of flow measurements, i.e. the loss of signal, may result from a malfunction or defect of the flow sensor, a break in electrical connectivity such as accidental disconnection of the flow sensor or cutting of a connecting cable, or another cause, such as electromagnetic or other disturbances.

[0067] During normal operation of the apparatus 1, that is to say before any interruption of transmission of flow measurement from the flow sensor 25, the control means 210 with (micro)processor 211, such as a controller, determine the set flow rate of gas containing NO to be supplied to the injection device 24 and control flow control means 220, 221, such as proportional solenoid valves 220 and / or TOR 221, to supply the gas containing NO at the set flow rate having been determined, as explained above.

[0068] This determination of the NO setpoint flow rate is carried out from a measurement of the respiratory gas flow rate, i.e. flow rate value or signal, carried out and supplied by the flow sensor 25 to the control means 210, of a NO content setpoint corresponding to the final proportion of NO desired in the combined gas mixture, typically set by the user, i.e. healthcare personnel, and the initial proportion of NO in the gas containing NO supplying the NO 1 delivery device, i.e. the quantity of NO present in the NO / N2 mixture coming from the gas cylinders 10, typically between 200 and 1000 ppmv, for example 450 or 800 ppmv.

[0069] The NO setpoint value and / or the NO content in the NO / N2 gas mixture supplying the apparatus 1 can be entered and / or adjusted and / or modified by the user, for example via the HMI, using dose adjustment means or the like, such as keys, sliders or the like. Preferably, the NO setpoint value and / or the NO content in the NO / N2 gas mixture supplying the apparatus 1 can be stored by the storage means 212 of the apparatus 1.

[0070] Advantageously, the NO set flow rate is determined, i.e. updated, at a frequency of between 10 Hz and 1000 Hz or at a time period of between 1 and 100 milliseconds (msec).

[0071] The successive NO set flow rates thus determined during normal operation of the apparatus 1 are stored by storage means 212, i.e. a storage device, such as a flash memory or other. These NO set flow rates are used to control the flow control means 220, 221 arranged on the internal circuit 200, in particular on the main section 200.1 and the secondary section 200.2, i.e. the emergency section, as explained above, to supply the gas containing NO at the set flow rate having been determined.

[0072] As already stated, in normal operating mode, in the embodiment of [Fig. 2], the NO / N2 flow passes through the main section 200.1 since the main flow control means 220, typically main valve means 2200, of the main section 200.1 are in the open position to allow the gas flow to pass, while the secondary flow control means 221, i.e. the secondary valve means 2200, of the secondary section 200.2 are in the closed position to prevent any circulation of gas in the secondary section 200.2, i.e. to block or prohibit any circulation of gas flow based on NO within this secondary section 200.2.

[0073] According to the invention, in the event of an interruption in the transmission to the control means 210 of any measurement of the respiratory gas flow rate by the flow sensor 25, the NO 1 delivery apparatus switches to emergency mode and the control means 210 are then configured to control, monitor or command the main and secondary flow rate control means 220, 221, typically the main and secondary valve means 2210, 2200, to supply the gas containing NO at an emergency flow rate. obtained or calculated from one or more set flow rates of gas containing NO having been determined by the control means 210 and having been stored by the storage means 212, before said interruption of transmission.

[0074] In the embodiment of [Fig.2], in the event of interruption of transmission to the control means 210 of any measurement of respiratory gas flow rate by the flow sensor 25, the NO / N2 flow then passes through the main section 200.1 or through the secondary section 200.2 depending on whether the main flow control means 220, i.e. the main valve means 2200, of the main section 200.1 also malfunction or not, as already explained.

[0075] Thus, when the main flow control means 220 of the main section 200.1, such as a proportional solenoid valve of an MFC, operate normally, the control means 210 are configured to control the main and / or secondary flow control means 220, 221 to circulate the gas flow through said main flow control means 220 and deliver the emergency gas flow via the main section 200.1.

[0076] On the other hand, in the event of a malfunction also of the main flow control means 220 of the main section 200.1, such as a proportional solenoid valve, said main flow control means 220, i.e. the main valve means 2200, of the main section 200.1 go (by default) to the closed position to stop the gas flow, while the secondary flow control means 221, i.e. the secondary valve means 2100, of the secondary section 200.2, such as a TOR solenoid valve, are controlled by the pilot means 210 to be in the open position and thus allow gas to circulate in the secondary section 200.2 and its emergency gas flow delivery, after passing through the calibrated orifice device 240.

[0077] In other words, the NO 1 delivery device is therefore designed to operate according to (at least) two operating modes, namely a so-called “normal” operating mode and a so-called “emergency” operating mode, called “emergency mode”. The transition from the normal operating mode to the emergency mode is done automatically in response to detection by the control means 210 of an interruption in the transmission of the respiratory gas flow rate measurements carried out by the flow sensor 25.

[0078] In all cases, in the event of an interruption in signal transmission, the emergency flow rate is obtained or calculated from several set flow rates having been determined and stored beforehand, for a given duration dt, by the control means 210, during normal operation of the device 1, i.e. before said interruption in transmission and switching to emergency mode.

[0079] The duration dt corresponds to the period of time preceding the moment of the interruption of transmission of the flow signal, that is to say the detection by the control means 210 of the interruption of transmission of the flow measurements. Preferably, the duration dt is less than or equal to 30 seconds, preferably less than or equal to 20 seconds, for example less than or equal to 10 seconds.

[0080] In other words, not all the set flow rate values ​​that have been determined and stored during the normal operation of the device 1, which generally lasts several hours, are used, but only the most recent ones, namely those determined and stored during the duration dt, i.e. the short period of time, typically < 30 sec, which immediately precedes the moment or instant when the interruption in transmission of the flow rate measurements (i.e. signal or value) occurred and was detected by the control means.

[0081] The set flow rate values ​​having been determined and stored during this duration dt, are preferably averaged, and possibly weighted or otherwise, to obtain an average flow rate value, i.e. the emergency flow rate.

[0082] It is therefore understood that, according to the invention, the emergency flow rate value(s) is / are calculated from the NO set flow rate values ​​having been previously used to control the NO flow, i.e. flow rate, during normal operation of the apparatus 1, and stored by the storage means of the apparatus 1, for duration dt, and this, contrary to what is taught by the prior art, which recommends using, in the event of interruption of transmission of the flow rate signal, either a single pre-fixed constant emergency flow rate value, or flow rate values ​​of the respiratory gas flow (e.g. air or N2 / O2) or of the NO flow measured during normal operation of the apparatus 1 and recorded in a stored history.

[0083] In other words, it has never been recommended before the present invention to store and use NO set flow rate values ​​that have been previously used to control the NO flow, during normal operation of the device 1, in order to use them subsequently in the event of interruption of the transmission of the flow rate measurements (i.e. loss of the flow rate signal) coming from the respiratory flow rate sensor, e.g. air or O2 / N2, i.e. after switching to emergency mode.

[0084] According to the invention, the emergency flow rate preferably corresponds to an average flow rate value obtained from the set flow rate values ​​determined and stored, during the duration dt, generally a duration dt of less than 45 to 60 seconds, typically less than 30 seconds, for example for 10 seconds or another duration, when the device 1 was fully functional, as explained above, that is to say when it is in normal operating mode.

[0085] Once the emergency flow rate has been determined, the control means 210 control the main and secondary flow control means 220, 221, typically the main and secondary valve means 2200, 2210, for supplying the gas containing NO, i.e. the NO / N2 gas mixture, at the emergency flow rate thus obtained, as explained above.

[0086] The NO 1 delivery apparatus can then continue to supply the NO-based mixture, i.e. NO / N2 mixture, but at the emergency flow rate thus determined, despite the absence of respiratory gas flow rate measurements, i.e. despite the interruption of transmission of these flow rate measurements (loss of signal), or even in the event of failure of the main flow rate control means 220, such as the MFC, which makes it possible to continue to treat the patient by supplying him with NO at the desired dosage or close to this dosage. This greatly improves the safety of treatment for the patient.

[0087] A gas administration installation 100 can be used to administer nitric oxide (NO) by inhalation, i.e. the final mixture obtained NO / O2 / N2, to people, i.e. patients, suffering from acute pulmonary arterial hypertension, in particular to operate a dilation of their pulmonary vessels and an increase in their oxygenation by improving pulmonary gas exchange, in particular to treat Pulmonary Arterial Hypertension of the Newborn or PPHN, Acute Respiratory Distress Syndrome or ARDS observed mainly in adults, or pulmonary hypertension (PH) in cardiac surgery in adults or children.

Claims

1. Claims Installation (100) for supplying a gas mixture containing NO to a patient comprising: - an NO delivery apparatus (1) supplied with a gas containing NO in a given initial proportion, and configured to supply the gas containing NO, - a breathing circuit (20; 21) comprising an injection device (24) configured to operate a mixture of the gas containing NO coming from the NO delivery apparatus (1) with a flow of breathing gas containing O2 conveyed by the breathing circuit (20; 21), and to obtain a combined gas mixture containing NO and oxygen, and - a flow sensor (25) configured to measure at least one respiratory gas flow rate within the respiratory circuit (20; 21) and provide at least one respiratory gas flow rate measurement, and wherein the NO delivery apparatus (1) comprises: - an internal gas circuit (200) for conveying the gas containing NO, - main and secondary flow control means (220, 221) configured to control the flow of gas containing NO conveyed by the internal gas circuit (200), - control means (210) with processor (211) configured for: • determine at least one set flow rate of gas containing NO to be supplied to the injection device (24), from at least one measurement of respiratory gas flow rate carried out and supplied by the flow sensor (25), and • control at least part of the flow control means (220, 221) to supply the gas containing NO at the set flow rate having been determined, - and storage means (212), characterized in that: - the storage means (212) are configured to store successive set flow rates of gas containing NO having been determined by the control means (210), and - in the event of interruption of transmission to the control means (210), of any measurement of respiratory gas flow rate by the flow sensor (25), the control means (210) are configured to control said flow control means (220, 221) to supply the gas containing NO at an emergency flow rate obtained or calculated from one or more set flow rates of gas containing NO having been determined by the control means (210) and stored by the storage means (212), before said interruption of transmission.

2. Installation according to claim 1, characterized in that the control means (210) are configured to determine successive set flow rates of gas containing NO from several successive respiratory gas flow measurements carried out by the flow sensor (25) and supplied to said control means (210).

3. Installation according to claim 2, characterized in that the storage means (212) are configured to store the successive set flow rates of gas containing NO having been determined by the control means (210).

4. Installation according to claim 1, characterized in that the emergency flow rate is obtained or calculated from several set flow rates having been determined by the control means (210) for a given duration (dt), before said transmission interruption.

5. Installation according to claim 4, characterized in that the emergency flow rate is calculated by taking an average of the set flow rates having been stored during the given duration (dt).

6. Installation according to claim 4, characterized in that the given duration (dt) is less than or equal to 30 seconds, preferably less than or equal to 20 seconds, more preferably less than or equal to 10 seconds.

7. Installation according to claim 1, characterized in that the control means (210) are configured to determine said at at least one set flow rate of gas containing NO to be supplied to the injection device (24), from at least one measurement of respiratory gas flow rate operated and supplied by the flow sensor (25), an NO content set point corresponding to the final proportion of NO desired in the combined gas mixture, and the initial proportion of NO in the gas containing NO supplying the NO delivery device (1).

8. Installation according to claim 1, characterized in that the NO delivery apparatus (1) is supplied with a gas containing an initial proportion of NO of between 100 and 1500 ppmv, in particular a gas mixture formed of nitrogen and NO.

9. Installation according to claim 1, characterized in that the NO delivery apparatus (1) comprises dose adjustment means configured to allow a user to set or select the NO content setpoint corresponding to the final proportion of NO desired in the combined gas mixture, preferably the NO content setpoint is between 1 and 80 ppmv.

10. Installation according to claim 1, characterized in that it comprises a medical ventilator (50) configured to supply the flow of respiratory gas containing O2 to said respiratory circuit (20; 21).

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