NO₂ delivery system to a patient configured to provide emergency flow in case of flow sensor malfunction

Abstract

The invention relates to an installation (100) for supplying a gas mixture containing NO, comprising an NO supply device (1) connected to a breathing circuit (20; 21) that includes a flow sensor (25). The device includes an internal gas circuit (200) with flow control means (220, 221), control means (210) for determining a set NO flow rate and controlling said flow control means, and storage means for storing successive set flow rates. In the event of an interruption in the transmission of flow measurements taken by the flow sensor, the control means operate the flow control means to supply the gas at a reserve flow rate calculated from the stored set flow rates.

Description

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

[0002] Inhaled nitric oxide (NO or NOi) is a gaseous drug commonly used to treat patients with acute pulmonary arterial hypertension, especially 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 nitric oxide (NO) therapy, a gas delivery system, also called an NO delivery system, is used. This system includes an NO delivery device and a medical ventilator, i.e., a respiratory support device, supplying a patient circuit. The NO delivery device injects a gas mixture based on NO, typically an NO / nitrogen mixture, into the patient circuit, which is also supplied with a gas stream containing oxygen (at least approximately 20% vol.), such as air or an oxygen / nitrogen (O₂ / N₂) mixture, provided by the medical ventilator. The patient circuit generally includes one or more flexible tubes fluidically connected to a respiratory interface, such as a tracheal intubation tube or similar device, used to deliver a therapeutic gas mixture containing a given quantity or dose of NO, i.e., a dosage, typically between 5 and 40 ppmv of NO, to the patient being treated.

[0004] Such a gas supply installation is described for example by EP3821929. This type of installation is used in a hospital setting 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 provide a therapeutic gas mixture to patients containing a NO content corresponding to the desired dosage, the NO delivery device must include means or a flow control system to control or adjust the flow of NO / N2 supplied, for example a system including one or more proportional or similar valves controlled by means of piloting the device.

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

[0008] Therefore, a flow sensor is typically installed in the breathing circuit between the medical ventilator and the NO / N2 injection site to perform (near-)continuous measurements of the breathing gas flow rate. These flow measurements are then transmitted to the control system, which uses them to calculate a target NO flow rate. This target flow rate is then used to control the flow control devices, typically one or more proportional valves, or other means.

[0009] However, during the use of a NO supply installation, it sometimes happens that the measurement of respiratory gas flow by the flow sensor is disrupted, defective or impossible to carry out, for example in the event of malfunction or accidental disconnection of the flow sensor, thus causing an interruption in the transmission of flow 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 setpoint NO flow rate which is used to control the flow control means, therefore the delivery of NO is done erroneously or may even be interrupted.

[0011] To avoid this, the device must be able to supply the patient with NO at the desired dosage, by switching to a so-called "emergency" or "emergency dosing" supply mode, in which the target NO flow rate is calculated even in the absence of flow measurement, i.e. even in the event of an interruption in the transmission of flow 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 an interruption in flow measurement transmission by the flow sensor. This is not precise and leads to significant fluctuations in the NO content of the combined gas mixture since the NO / N2 flow rate is fixed while the flow rate of the breathing gas, into which the NO / N2 flow rate is injected to form the combined gas mixture, varies over time.

[0013] Furthermore, EP3410927 proposes storing a history of flow measurement values ​​from the flow sensor and using this history to calculate the target NO / N2 flow rate in case of an interruption in flow measurement transmission. This solution is not ideal because the stored "raw" flow values ​​may be erroneous, particularly in the event of intermittent flow sensor malfunctions, which could result, for example, from unexpected electrostatic discharges on the sensor, leading to the storage of incorrect breathing gas flow values. Since the flow values ​​are erroneous, the flow calculations using them are also erroneous, resulting in an inadequate supply of NO / N2.

[0014] Furthermore, EP3410927 proposes using an additional NO sensor to measure the NO / N₂ flow rate delivered by the device over time and to store a history of the NO flow rate measurements taken by the additional NO sensor. In the event of an interruption in the transmission of breathing gas flow rate measurements by the breathing gas sensor, the device uses the history of stored NO flow rate values ​​to set the target NO / N₂ flow rate. Again, this solution is not ideal because it complicates the overall device architecture by requiring the incorporation of an additional sensor. Moreover, working with historical NO values ​​previously delivered has drawbacks since these flow rate values ​​can be erroneous, for example, due to an excessively high measurement signal-to-noise ratio, particularly for very low delivered NO values ​​(i.e., ppmv).

[0015] One problem is therefore to propose an improved NO delivery system, allowing the determination of a set NO flow rate, in the absence of respiratory gas flow measurement, i.e. in the event of an interruption of the transmission to the control means (i.e. loss of the respiratory flow signal), of the respiratory gas flow measurements carried out by the flow sensor, so as to be able to provide 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 professional, i.e. a doctor or similar.

[0016] One solution of the invention relates to a system for supplying a gaseous mixture containing NO, also called an "NO supply system", to a patient, comprising: a NO delivery device supplied with a gas containing NO in a given initial proportion, typically a NO / N2 mixture, and configured to deliver the NO-containing gas, a breathing circuit comprising an injection device configured to operate a mixture of the NO-containing gas from the NO delivery device with a flow of breathing gas containing O2 delivered through the breathing circuit, and obtain a combined gas mixture containing NO and oxygen, and a flow sensor configured to measure at least one breathing gas flow within the breathing circuit and provide at least one breathing gas flow measurement.

[0017] The NO dispensing device of the NO supply installation includes: an internal gas circuit for conveying NO-containing gas, primary and secondary flow control means configured to control (i.e. allow, prevent / prohibit, adjust...) the flow of NO-containing gas conveyed by the internal gas circuit, (micro)processor control means configured to: ▪ determine at least one setpoint flow of NO-containing gas to be supplied to the injection device, from at least one measurement of breathing gas flow taken by the flow sensor, and ▪ control at least part of the primary and secondary flow control means to supply NO-containing gas at the setpoint flow that has been determined, and storage means.

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

[0019] Depending on the embodiment considered, the installation of the invention may include one or more of the following features: The control means are configured to determine successive NO-containing gas setpoint flow rates from several successive breathing gas flow rate measurements taken by the flow sensor and provided to said control means. The storage means are configured to store the successive NO-containing gas setpoint flow rates determined by the control means. The storage means are configured to store the successive NO-containing gas setpoint flow rates determined during the normal operation of the device and / or installation, i.e., before any loss of the breathing gas flow signal. The backup flow rate is obtained or calculated from several setpoint flow rates determined by the control means over a given period (dt) before said transmission interruption, i.e., successive flow rates determined during the normal operation of the device.The backup flow rate is calculated by averaging the setpoint flow rates stored during the given time interval (dt), i.e., before any loss of the breathing flow signal. The given time interval (dt) is less than or equal to 30 seconds, preferably less than or equal to 20 seconds, and preferably less than or equal to 10 seconds. The given time interval (dt) is fixed or, in another embodiment, modifiable. The given time interval (dt) is stored. The control means are configured to determine at least one setpoint flow rate of NO-containing gas to be supplied to the injection device, based on at least one breathing gas flow rate measurement taken and provided by the flow sensor, a setpoint for the NO concentration corresponding to the desired final proportion of NO (i.e., a dosage) in the combined gas mixture, and the initial proportion of NO in the NO-containing gas 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 an interruption in the transmission of any breathing gas flow measurement by the flow sensor to the control means (i.e., in the event of a loss of the breathing gas signal), the control means are configured to control the primary flow control means (i.e., those that remain operational, i.e., the primary flow control means that are not malfunctioning) to supply the NO-containing gas at the said backup flow rate. When the primary flow control means continue to function normally (i.e., those that are not malfunctioning), despite the interruption in the transmission of flow measurements (i.e., the primary flow control means), the device is configured to control the primary flow control means.In the event of a loss of the breathing gas flow signal, the NO-containing gas flows through the main line, which includes the primary flow control means. These means are controlled by the pilot means to supply the NO-containing gas at the backup flow rate. Conversely, in the event of an interruption in the transmission of any breathing gas flow measurement from the flow sensor to the pilot means, and also in the event of a malfunction of the primary flow control means (i.e., the primary flow control means are non-operational or out of service), the pilot means are configured to control the secondary flow control means (to make them operational) in order to supply the NO-containing gas at the backup flow rate. When the primary flow control means are not functioning normally, i.e., are malfunctioning, with an interruption in the transmission of flow measurements (i.e.,In the event of a loss of the breathing flow signal, the NO-containing gas flows through the secondary line (and no longer through the main line), which includes secondary flow control means driven by the pilot means to supply the NO-containing gas at the backup flow rate. The flow sensor is arranged within the breathing circuit, upstream of the injection device. The NO delivery device is supplied with a gas containing an initial proportion of NO between 100 and 1500 ppmv, typically between 200 and 1000 ppmv. The NO delivery device is supplied with a gas mixture consisting of nitrogen and NO. The NO delivery device includes dose adjustment means configured to allow a user to set or select the NO concentration setpoint corresponding to the desired final proportion of NO in the combined gas mixture, i.e., a dosage.The dose control means are part of an HMI (Human-Machine Interface) or GUI (Graphical User Interface). The dose control means include one or more user-operated touch buttons displayed on a digital touchscreen of the HMI. The HMI screen is a color display type. The NO concentration setpoint is between 1 and 80 ppmv, typically between 5 and 40 ppmv. It includes a medical ventilator configured to deliver the respiratory gas flow containing O2 to the respiratory circuit. The medical ventilator is configured to deliver a respiratory gas flow containing at least approximately 20% vol. O2, typically an NO / N2 mixture or air. The NO delivery device and the medical ventilator are fluid-connected to the respiratory circuit. The flow sensor is arranged in the respiratory circuit between the medical ventilator and the injection device.The injection device includes a first gas inlet supplied with a flow of respiratory gas containing O₂, i.e., from the medical ventilator. The injection device further includes a second gas inlet supplied with gas containing NO at the set flow rate, i.e., from the NO delivery device. The injection device further includes a gas outlet providing the combined gas mixture containing NO and oxygen, obtained by mixing, within the injection device, the gas containing NO (e.g., NO / N₂ mixture) with the flow of respiratory gas containing O₂ (e.g., air or O₂ / N₂ mixture). The storage means include computer memory, such as flash memory, RAM, or similar. The control means are configured to detect any interruption in the transmission of respiratory gas flow measurements from the flow sensor to the control means.The control means are configured to detect any interruption in the transmission of breathing gas flow measurements taken by the flow sensor, i.e., any loss of the breathing flow signal. The NO delivery device operates in at least two modes, including a normal operating mode and a backup operating mode. The NO delivery device is configured to automatically switch from normal operating mode to backup mode in response to an interruption in the transmission of breathing gas flow measurements taken by the flow sensor (i.e., in case of loss of the breathing flow signal), with or without malfunction of the main flow control means, in particular the main valve means.The control means are configured to detect any interruption in the transmission of breathing gas flow measurements and / or any malfunction of the main flow control means. The control means are configured to activate the backup mode in the event of an interruption in the transmission of breathing gas flow measurements (i.e., in the event of loss of the breathing gas signal). The control means are configured to determine successive NO-containing gas setpoint flow rates from successive breathing gas flow measurements taken by the flow sensor during normal operation of the NO delivery device, i.e., when it is operating in its normal operating mode.The control means are configured to command the primary and / or secondary flow control means to supply NO-containing gas at the emergency flow rate during operation of the NO delivery device in emergency mode. The control means are configured to determine and store successive NO-containing gas setpoint flow rates during normal operation of the NO delivery device. The internal gas circuit comprises two parallel gas sections, including a primary section and a secondary or emergency section. The primary and secondary sections include primary and secondary flow control means, typically primary and secondary valve means, such as solenoid valves or the like.The control means are configured to control the primary and secondary flow control means to allow or prevent the passage of the NO / N₂ flow through either the primary or secondary section, specifically depending on the operating mode of the NO delivery device. In normal operating mode, the control means are configured to control the primary and / or secondary flow control means so that the NO / N₂ flow passes only through the primary section. In backup mode, the control means are configured to control the primary and / or secondary flow control means so that the NO / N₂ flow passes through the primary section or, as appropriate, through the backup section, depending on whether the primary flow control means are functioning or, conversely, malfunctioning, respectively.The primary and secondary flow control means include primary and secondary valve means, such as solenoid valves. The primary flow control means include a proportional solenoid valve. The secondary flow control means include an on / off solenoid valve, preferably actuated in pulsed mode. The primary flow control means include a mass flow controller (MFC). The mass flow controller (MFC) includes at least one proportional solenoid valve actuated by the control means and a primary flow sensor. The primary flow sensor is integrated into the structure of the proportional solenoid valve of the MFC. The solenoid valve of the MFC further incorporates a microprocessor-based electronic board implementing at least one algorithm. The secondary section, i.e.The emergency section includes a calibrated orifice device for controlling the gas flow in the secondary section, particularly in emergency mode. The calibrated orifice device is arranged downstream of secondary flow control means for the secondary section. The secondary flow control means for the secondary section include secondary valve means, typically a solenoid valve, preferably of the on / off (ON / OFF) type. The on / off (ON / OFF) solenoid valve is actuated by the pilot means, preferably in pulsed mode. The main section includes one or more proportional solenoid valves, and the secondary section includes one or more on / off (ON / OFF) solenoid valves. The main section includes one or more proportional solenoid valves that are normally closed. In normal operation, the proportional solenoid valve is actuated to be at least partially open (i.e.,Proportional opening) and allow the passage of gas containing NO. In normal operation, the on / off solenoid valve is closed or controlled by the control means to be closed, thus preventing any passage of gas containing NO, i.e., preventing gas circulation. In the event of a malfunction of the main flow control means, typically the MFC, the proportional solenoid valve closes automatically or, as appropriate, is controlled to close, so as to prohibit, stop, or prevent any gas circulation. In the event of a malfunction of the main flow control means, typically the MFC, the on / off solenoid valve opens automatically or is controlled to be opened (i.e., to open), so as to allow or permit the passage of gas (e.g., NO / N₂) in the secondary section. The control means include a (micro)controller or similar device. The control means include one or more (micro)processors arranged on one or more electronic boards.The control means include one (or more) (micro)processors implementing one or more algorithms, in particular one (or more) algorithm for controlling the main and / or secondary flow control means, one (or more) algorithm for processing breathing gas flow measurements.... the storage means are integrated into the control means, in particular arranged on the electronic board.

[0020] Furthermore, depending on the embodiment considered, the gas supply installation of the invention may include 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% by volume of oxygen, preferably at least approximately 21% by volume of oxygen. The medical ventilator includes a motorized blower (i.e., turbine, compressor, or similar) delivering the breathing gas, typically air or an oxygen / nitrogen mixture, or, in another embodiment, an internal gas circuit comprising one or more proportional valves for routing the gas and controlling its supply, including its flow rate. Such a ventilator is generally supplied with breathing gas from one or more wall outlets supplied by a gas network in a hospital or hospital building, typically air or an oxygen / nitrogen mixture. The medical ventilator includes control means or a control device, such as one or more electronic control boards.Preferably, the medical ventilator's control means operate or control the motorized blower or, as appropriate, the proportional valves of the medical ventilator. The medical ventilator is of the HFO type or includes an HFO function, meaning 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 above 100 bar abs (before withdrawal begins). The NO source is or includes one or more gas cylinders with a capacity between 0.5 and 50 L (water equivalent).The gas cylinder(s) comprise a cylindrical body made of steel or aluminum alloy and are equipped with a simple valve (without a regulator) or a valve 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 tubing forming the inspiratory and expiratory branches, for example, polymer tubing. The inspiratory and expiratory branches, e.g., flexible tubing, are connected to a junction piece, such as a Y-piece. The inspiratory and / or expiratory branches are fluid-connected to a patient breathing interface, preferably via the junction piece. The patient breathing interface comprises a tracheal intubation tube or breathing mask, or other device.The inspiratory and expiratory limbs are further fluidically connected to, respectively, the inlet and outlet ports of the medical ventilator. The breathing circuit, in particular the inspiratory limb, may include a gas humidifier. The gas humidifier is arranged downstream of the delivery device, for example, a NO delivery module, so as to humidify the gas before its inhalation administration to the patient. The ventilator and the NO delivery device are electrically powered by one or more power sources, typically mains electricity (110 / 220V) and / or one or more rechargeable batteries.

[0021] According to another (unclaimed) aspect, the present disclosure also relates to a method of therapeutically treating a person, i.e., a human patient (i.e., adult, child, adolescent, or neonate), suffering from pulmonary hypertension and / or hypoxia, causing pulmonary vasoconstriction or the like, comprising administering by inhalation to the person in need, a gas mixture comprising 1 to 80 ppmv of NO and at least 20% vol. of oxygen approximately, preferably at least 21% vol. of oxygen, by means of a gas supply system, such as that described above according to the invention, comprising an NO delivery device ensuring delivery of NO at a backup 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 (e.g.air or N2 / O2) and the means of 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 type PPHN (persistent pulmonary hypertension of the newborn) or ARDS (acute respiratory distress syndrome), or caused by cardiac surgery with the patient being placed under extracorporeal blood circulation (ECC). Definitions

[0022] In general, within the scope of the invention: "ppmv" means parts per million by volume, "%vol." means percentage by volume. "NO" refers to nitrogen monoxide. "NO₂" refers to nitrogen dioxide. "N₂" refers to nitrogen. "O₂" refers to oxygen. The terms "concentration," "quantity," "proportion," "dose," and "content" are considered equivalent. The terms "means of / to / for" are considered entirely equivalent and interchangeable with the terms "device of / to / for," for example, the terms "pilot means" can be replaced by "pilot device," the terms "valve means" can be replaced by "valve device," the "memory means" can be replaced by "memory device," etc. By "normal operation" or "normal operating mode," we mean the usual operation of the NO delivery device in the absence of any malfunction hindering or preventing supply (i.e.,Interruption of transmission or loss of flow signal) to the control means of 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) delivered through the breathing circuit, typically from the medical ventilator. By "malfunction" is meant a failure, anomaly, problem, defect, accidental disconnection or any technical problem, such as electromagnetic interference, 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 taken by the flow sensor measuring the flow of the respiratory gas (i.e., air or N2 / O2) delivered through the breathing circuit, typically from the medical ventilator."Flow measurement" means a flow value (e.g., a numerical value) or a signal representing such a flow value that reflects or corresponds to a gas flow measured by a flow sensor, such as a mass flow sensor. "Pressure measurement" means a pressure value (e.g., a numerical value) or a signal representing such a pressure value that reflects or corresponds to the gas pressure measured by a pressure sensor (regardless of the sensor's operating mode). "Backup mode operation" means operation of the NO delivery device in the event of a malfunction that hinders or prevents the supply (i.e., interruption of flow signal transmission or loss of flow signal) to the NO delivery device's control means of breathing gas flow measurements (i.e.,air or O2 / N2 mixture) operated by the flow sensor, with or without possible concomitant malfunction of the main flow control means (e.g., the proportional solenoid valve of the MFC) located on the main gas section.

[0023] 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 illustrates an embodiment of a gas administration installation according to the invention. Fig. 2 illustrates a schematic embodiment of the internal architecture of the NO delivery device of a gas distribution system according to the invention, in particular a gas distribution system according to Fig. 1 .

[0024] Fig. 1 diagram shows an embodiment of a gas administration installation 100 according to the invention comprising a NO supply device 1 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.

[0025] The installation 100 here includes two pressurized gas cylinders 10 each containing a gaseous NO / N 2 mixture, namely here a gaseous NO / N 2 mixture containing between 100 and 1000 ppmv of NO (remaining N 2), for example 450 or 800 ppm vol. of NO (remaining N 2), or any other suitable concentration, which supply the NO / N 2 mixture to the device or apparatus 1 for delivering or supplying NO, enabling the supply of the gaseous NO / N 2 mixture to be monitored and controlled.

[0026] The gas cylinders 10 are fluidly connected to the NO supply unit 1 via gas supply lines 12, such as flexible hoses 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 NO delivery unit 1, which supply an internal gas circuit 200, as schematically shown in Fig. 2 , used to convey the gas within the NO supply device 1, i.e. in the external casing or housing 1.1 of the device 1.

[0027] In the implementation of Fig. 2 The internal gas circuit 200 is connected to two gas inlets 2 arranged in parallel, each supplying a dedicated inlet section 200.3 of the internal gas circuit 200. Control valves 222 or similar control the flow of NO / N 2 into these inlet sections 200.3.

[0028] The NO delivery device 1 also includes an oxygen inlet 3 fluidically connected, via an oxygen supply line 11, such as a flexible hose or similar, to an oxygen source (not shown), for example, a pressurized oxygen cylinder or a hospital network, i.e., an oxygen supply pipeline installed in a hospital building. This allows the internal gas circuit 200 to be supplied with oxygen when required.

[0029] The medical ventilator 50, that is to say a respiratory assistance device, provides a flow of oxygen-based respiratory gas, that is to say containing at least 20% vol. of oxygen about, preferably at least 21% vol. of oxygen about, such as air or an oxygen / nitrogen mixture (N2 / O2).

[0030] The medical ventilator 50 and the NO supply device 1 of the installation 100 are in fluidic communication with a breathing circuit 20, also called the patient circuit, in particular with a gas supply line or inspiratory branch 21 of the breathing circuit 20, which serves to convey the gas flow to the breathing interface 40 supplying the therapeutic gas flow to the patient, i.e. a final gas mixture containing the desired NO dosage.

[0031] More specifically, 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) from the medical ventilator 50 and the flow containing NO, i.e. the NO / N2 gas mixture, delivered by the NO delivery device 1.

[0032] To do this, the NO delivery device 1 supplies or injects the NO / N 2 mixture into the breathing circuit 20, typically into the inspiratory limb 21, via a conduit or injection line 23, fluidly connecting the internal gas circuit of the NO supply device 1 to an injection device 24 arranged on the gas supply line 21.

[0033] The injection device 24 is configured to operate a mixture of the NO-containing gas from the NO delivery device 1 with the O2-containing respiratory gas stream from the ventilator 50 and delivered through the inspiratory branch 21 of the respiratory circuit 20, and obtain a combined gas mixture containing NO and oxygen, i.e. the final gas mixture administered to the patient.

[0034] More specifically, the injection device 24 includes a first gas inlet supplied with a flow of breathing gas containing O2 from the medical ventilator 50, a second gas inlet supplied with gas containing NO, i.e. from the NO delivery device 1, 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 breathing gas containing O2.

[0035] In other words, the NO / N2 flow brought 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 carried 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, ....), i.e. a final NO / N2 / O2 gas mixture.

[0036] The inspiratory branch 21 of the circuit 20 further includes a gas humidifier 30 arranged downstream of the injection device 24. It allows the final gas flow, e.g. the combined NO / N2 / O2 gas mixture, to be humidified before it is administered by inhalation to the patient to be treated, by means of a respiratory interface 40, such as a tracheal intubation tube, a breathing mask or similar.

[0037] A patient exhaled gas recovery line forms an expiratory branch 22 of the patient circuit 20. It is fluidly connected to the inspiratory branch 21 via a connecting piece 25, such as a Y-piece.

[0038] The inspiratory limb 21 is, at its upstream end, fluidically connected to an outlet port 51 of the medical ventilator 50, such as a connector, fitting, or similar device, so as to recover and deliver the oxygen-based gas, typically air or an N₂ / O₂ mixture supplied by the medical ventilator 50. Conversely, the expiratory limb 22, which carries the exhaled gases, is fluidly connected to an inlet port 52 of the medical ventilator 50, such as a connector, fitting, or similar device, so as to return all or part of the patient's exhaled gas flow to the medical ventilator 50. The expiratory limb 22 may include one or more optional components, for example, a CO₂ removal device 35, i.e., a CO₂ trap, such as a hot tank or similar device, for removing CO₂ present in the patient's exhaled gases, a filter, or similar device.

[0039] Furthermore, a flow sensor 25, for example of the hot-wire or differential pressure type, is arranged on the breathing circuit 20, in particular on the inspiratory limb 21, between the ventilator 50 and the injection device 24. The flow sensor 25 is connected to a connection port to the sensor 27, of the NO delivery device 1, via a flow measurement line 26 which connects to said connection port to the sensor 27. It serves to measure the flow rate of gas delivered by the ventilator 50, such as air or N2 / O2, circulating in the inspiratory limb 21, upstream of the injection device.

[0040] These flow measurements taken by the flow sensor 25 allow for more effective control or regulation of the NO (i.e., N₂ / O₂) flow delivered by the NO delivery device 1, in particular the NO flow rate, since the flow measurements taken by the flow sensor 25 are returned, via the flow measurement line 26 (i.e., electrical cables or similar) and the connection port to the sensor 27, to (micro)processor-based control means 210 of the NO delivery device 1, typically a controller, which processes these flow 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 links, for example electrical cables or similar.

[0041] 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 lines, passages or conduits for gas or similar, used to convey the flow of NO-based gas, i.e. the NO / N 2 mixture, from the NO / N 2 mixing cylinders 12. The internal gas circuit 200 fluidly connects the gas inlet(s) 21 of the NO supply device 1 to the injection line 23 so as to convey the flow of NO-based gas between them.

[0042] In the schematic embodiment shown in Fig. 2 A portion of the internal gas circuit 200 comprises two parallel gas sections, namely a main section 200.1 and a secondary section 200.2, referred to as the backup section. The main section 200.1 and the secondary section 200.2 are fluidly connected to each other and to the rest of the gas circuit 200 at upstream connection points 260 and downstream connection points 261 located, respectively, upstream and downstream of the main and secondary flow control means 220, 221.

[0043] In this case, under normal operating conditions, the NO / N 2 flow passes through the main segment 200.1, whereas in the event of a signal transmission interruption, it automatically switches to backup mode, as explained below and: If the main flow control means 220 remain operational, i.e. continue to function normally, typically a mass flow controller or MFC, then the NO / N 2 flow continues to pass through the main section 200.1; if the main flow control means 220 are rendered non-operational, i.e. malfunctioning, the NO / N 2 flow is diverted and then passes through the backup section 200.2.

[0044] 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 and emergency operating modes. However, in this embodiment, a malfunction of the main flow control means 220 could not be taken into account, and the device 1 would then become inoperative.

[0045] In general, the main and secondary flow control means 220, 221, such as main and secondary valve means 2200, 2210, schematically represented in Fig. 2 , i.e. one (or more) valve(s) device(s), for example one (or more) proportional solenoid valve(s) 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 there towards the injection line 23, i.e. towards the injection device 24, whether in normal operating mode or in emergency mode.

[0046] Preferably, the main section 200.1 includes a proportional solenoid valve 220 and an additional flow sensor 230, typically a mass flow controller or MFC, while the secondary section 200.2 includes one (or more) on / off solenoid valves 221, preferably piloted in pulsed mode.

[0047] Preferably, the main and secondary flow control means 220, 221 of the NO supply device 1 are commanded, i.e. controlled, by the control means 210, i.e. a (or more) control device or (micro)controller, arranged in the housing 1.1 of the NO supply device 1.

[0048] Typically, the control means 210 include an electronic board comprising one or more microprocessors 211 implementing one or more algorithms. The control means 210 allow, in particular, the adjustment or control of the NO-based gas flow rate by controlling all or part of the valve means 2200, 2210, typically opening or closing one or more (solenoid) valves, to obtain a flow rate of NO-based gas, typically allowing or stopping the gas flow.

[0049] Of course, the control means 210 also allow calculations to be performed and / or all electromechanical elements of the device 1 to be controlled, such as sensors, displays...

[0050] 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 setpoint for NO content adjusted and / or fixed 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) operated by the flow sensor 25 arranged on the inspiratory limb 21 and connected by a flow measurement line 26 to the NO supply device 1, in particular to the control means 210, via the connection port to the sensor 27.

[0051] The internal gas circuit 200 of the NO supply unit 1 may also include other elements or components, in particular one or more pressure sensors 250, one or more additional flow sensors or flow meters, 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., 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 conforms to the desired flow rate.

[0052] Thus, in Fig. 2 , we see that the main section 200.1 includes an additional flow sensor 230 arranged upstream of the flow control means 220, such as valve means 2200, for example a solenoid valve, preferably a proportional solenoid valve, controlling the passage of gas in the main section 200.1. This assembly forms a mass flow controller (MFC).

[0053] Furthermore, the secondary section 200.2 includes a calibrated orifice device 240 arranged downstream of secondary flow control means 221, such as secondary valve means 2210, preferably a solenoid valve(s), controlling the flow of gas in the secondary section 200.2.

[0054] Advantageously, the solenoid valve of the secondary flow control means 221 is of the on / off (ON) type, that is to say, it can adopt 2 "stable" positions, namely an open position allowing the gas flow to pass and a closed position preventing any circulation of gas flow.

[0055] According to the invention, in the event of an interruption in the transmission of the breathing gas flow measurement signal, i.e., a loss of the breathing gas flow signal, but with the main flow control means 220 operational (MFC), i.e., continuing to function normally, the NO / N2 flow continues to pass through the main section 200.1 and the control means 210 operate the proportional solenoid valve 220, i.e., in proportional mode, to adjust and deliver the gas at the desired backup flow rate. The on / off solenoid valve 221 arranged on the secondary section 200.2 is then in the closed position. Device 1 is then in backup mode, but the NO / N2 flow continues to pass through the main section 200.1.

[0056] However, in the event of an interruption in the transmission of the breathing gas flow measurement signal with a simultaneous malfunction of the main flow control means 220 (i.e., the MFC, for example, the proportional solenoid valve), the control means 210 then command (typically in pulsed mode) the opening of the on / off (TOR) solenoid valve 221 located on the secondary section 200.2 to allow gas to flow through this secondary section 200.2 to deliver the gas at the desired backup flow rate, while the proportional solenoid valve 220 is no longer controlled and returns to the closed position, which is preferably its default position. Device 1 is then also in backup mode and the NO / N flow 2 no longer passes through the main section 200.1.

[0057] Furthermore, the additional flow meter or flow sensor 230 of the MFC can be of the differential pressure, mass or other type, and cooperates with the control means 210 to provide them with flow measurements of the NO / N2 flow.

[0058] Typically, the NO1 delivery device also includes a graphical user interface (GUI) comprising a graphical display, preferably a touchscreen, used to display various information or data, icons, graphs, alarms, etc., as well as virtual selection keys and / or touchpads or windows, used in particular for making choices, selections, or entering information, such as desired values ​​(e.g., flow rate, NO dosage), or any other information or data useful to healthcare personnel. Preferably, the display is in color, but it can also be in black and white.

[0059] The power supply for the NO 1 supply unit, in particular for components requiring electrical current to operate, such as the control means 210, the graphic display 4, etc., is conventionally provided by a power source and / or power supply means (not shown), for example, a mains power connection (110 / 220V) such as a power cord and plug, and / or one or more power supply batteries, preferably rechargeable, and / or a current transformer. The power supply for the medical ventilator 50 is provided in a similar manner, notably by a mains power connection or an internal battery.

[0060] In addition, the installation 100 also includes a gas sampling line 60 which fluidly connects the inspiratory branch 21 to the NO supply device 1. It is fluidly connected (at 61) to the gas supply line 21, between the humidifier 30 and the junction piece 25, i.e. Y-piece, typically in the immediate vicinity of the junction piece 25, and also to an inlet port 62 of the NO supply device 1, for example a port 62 carried by a connector, fitting or similar, allowing the connection of the gas sampling line 60, such as a flexible hose or similar.The gas sampling line 60 allows for the collection of gas samples and their conveyance to the NO₂ supply device, where they are analyzed in an internal gas analyzer (not shown). This analysis takes place within a calibration line comprising at least one sensor, including one or more electrochemical cells, electrically connected to the control system, to verify their conformity. Specifically, it is necessary to verify that the composition of the final gas conforms to that of the desired NO / N₂ / O₂ gas mixture to be administered to the patient. This verification ensures that the gas does not contain excessive amounts of toxic NO₂ species, that its oxygen content is not hypoxic, that it does not contain an excessively high NO₂ content, and that its NO content corresponds to the desired dosage, i.e., the dose of NO to be administered by inhalation, which is usually chosen by the healthcare personnel, i.e., physician or similar professional.This conformity check is conventionally performed using dedicated measuring devices, typically NO₂, NO, and O₂ sensors, for example, electrochemical cells or similar devices, which themselves must be calibrated periodically, for example, weekly. The control means 210 of device 1 are further configured to retrieve and process, i.e., analyze, the signals from the various sensors of the gas analyzer, which is arranged within device 1, and to act in response to these signals, in particular to perform sensor calibration.

[0061] Within the framework of the invention, in order to be able to determine a setpoint NO flow rate, in the absence of respiratory gas flow rate measurement, i.e. in the event of interruption of transmission to the control means 210 or loss of signal, of the respiratory gas flow rate measurements operated 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 similar, the following procedure is carried out.

[0062] The interruption of flow measurement transmission, i.e., the loss of signal, can result from a malfunction or defect in the flow sensor, a break in electrical connectivity such as an accidental disconnection of the flow sensor or a severing of a connecting cable, or another cause, such as electromagnetic or other disturbances.

[0063] During normal operation of device 1, i.e. before any interruption of flow measurement transmission from flow sensor 25, the control means 210 with (micro)processor 211, such as a controller, determine the set flow rate of NO-containing gas 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 NO-containing gas at the set flow rate that has been determined, as explained above.

[0064] This determination of the NO setpoint flow rate is carried out from a measurement of respiratory gas flow rate, i.e. flow value or signal, operated and supplied by the flow sensor 25 to the control means 210, a setpoint of NO content 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 delivery device 1, i.e. the quantity of NO present in the NO / N 2 mixture coming from the gas cylinders 10, typically between 200 and 1000 ppmv, for example 450 or 800 ppmv.

[0065] The NO setpoint value and / or the NO concentration in the NO / N₂ gas mixture supplying device 1 can be entered, adjusted, and / or modified by the user, for example via the HMI, using dose control or similar means, such as buttons, sliders, or the like. Preferably, the NO setpoint value and / or the NO concentration in the NO / N₂ gas mixture supplying device 1 can be stored by the storage means 212 of device 1.

[0066] Advantageously, the NO setpoint flow rate is determined, i.e. updated, at a frequency between 10 Hz and 1000 Hz or at a time period between 1 and 100 milliseconds (msec).

[0067] The successive NO setpoint flow rates thus determined during the normal operation of the device 1 are stored by storage means 212, i.e., a storage device such as a flash memory or other. These NO setpoint 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 backup section, as explained above, to supply the NO-containing gas at the setpoint flow rate that has been determined.

[0068] As already mentioned, in normal operating mode, in the implementation mode of Fig. 2 , the NO / N 2 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 gas flow in the secondary section 200.2, i.e. to block or prohibit any flow of NO-based gas within this secondary section 200.2.

[0069] According to the invention, in the event of an interruption of transmission to the control means 210 of any measurement of breathing gas flow by the flow sensor 25, the NO delivery device 1 goes into backup mode and the control means 210 are then configured to control, control or command the main and secondary flow control means 220, 221, typically the main and secondary valve means 2210, 2200, to supply the gas containing NO at a backup flow rate obtained or calculated from one or more setpoint flow rates of gas containing NO having been determined by the control means 210 and having been memorized by the memorization means 212, before said interruption of transmission.

[0070] In the implementation of Fig. 2, in the event of an interruption of transmission to the control means 210, of any measurement of breathing gas flow by the flow sensor 25, the NO / N 2 flow then passes through the main section 200.1 or through the secondary 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.

[0071] Thus, when the main flow control means 220 of the main section 200.1, such as a proportional solenoid valve of an MFC, are operating normally, the pilot 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.

[0072] On the other hand, in the event of a malfunction of the main flow control means 220 of the main section 200.1, such as a proportional solenoid valve, the said main flow control means 220, i.e. the means with main valves 2200, of the main section 200.1 go (by default) into the closed position to stop the gas flow, while the secondary flow control means 221, i.e. the means with secondary valves 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 circulation in the secondary section 200.2 and its delivery of emergency gas flow, after passing through the calibrated orifice device 240.

[0073] In other words, the NO 1 delivery device is designed to operate in (at least) two modes: a "normal" mode and a "backup" mode. The switch from normal to backup mode occurs automatically upon detection by the control system 210 of an interruption in the transmission of breathing gas flow measurements from the flow sensor 25.

[0074] In all cases, in the event of an interruption of signal transmission, the backup flow rate is obtained or calculated from several setpoint flow rates which have been determined and stored beforehand, for a given duration dt, by the control means 210, during the normal operation of the device 1, that is to say before said interruption of transmission and switch to backup mode.

[0075] The duration dt corresponds to the period of time preceding the interruption of the flow signal transmission, i.e., the detection by the control means 210 of the interruption in the transmission of 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.

[0076] In other words, not all the setpoint flow values ​​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, that is to say the short period of time, typically < 30 sec, which immediately precedes the moment or instant when the interruption of transmission of flow measurements (i.e. signal or value) occurred and was detected by the control means.

[0077] The setpoint flow values ​​having been determined and stored during this time dt, are preferably averaged, and possibly weighted or otherwise, to obtain an average flow value, i.e. the emergency flow.

[0078] It is therefore understood that, according to the invention, the emergency flow value(s) is calculated from the NO setpoint flow values ​​previously used to control the NO flow, i.e. flow, during the normal operation of the device 1, and stored by the storage means of the device 1, for a duration dt, contrary to what is taught by the prior art, which recommends using, in the event of an interruption in the transmission of the flow signal, either a single prefixed constant emergency flow value, or flow values ​​of the respiratory gas flow (e.g. air or N2 / O2) or of the NO flow measured during the normal operation of the device 1 and recorded in a stored history.

[0079] In other words, it has never been recommended before the present invention to store and use NO setpoint flow values ​​that were previously used to control the NO flow during normal operation of device 1, in order to use them later in case of interruption of the transmission of flow measurements (i.e. loss of flow signal) from the respiratory flow flow sensor, e.g. air or O2 / N2, i.e. after switching to backup mode.

[0080] According to the invention, the emergency flow rate corresponds preferably to an average flow rate value obtained from the determined and stored setpoint flow rate values, 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, i.e. when it is in normal operating mode.

[0081] Once the emergency flow rate has been determined, the pilot means 210 control the main and secondary flow control means 220, 221, typically the main and secondary valve means 2200, 2210, to supply the gas containing NO, i.e. the NO / N2 gas mixture, at the emergency flow rate thus obtained, as explained above.

[0082] The NO delivery device can then continue to supply the NO-based mixture, i.e., the NO / N₂ mixture, but at the backup flow rate thus determined, even in the absence of respiratory gas flow measurements, that is, despite the interruption of transmission of these flow measurements (signal loss), or even in the event of failure of the primary flow control devices, such as the MFC. This allows the patient to continue receiving treatment by delivering NO at the desired dosage or close to it. This greatly improves treatment safety for the patient.

[0083] A gas delivery system 100 can be used to administer by inhalation of nitric oxide (NO), i.e. the final mixture obtained NO / O2 / N2, to persons, 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. An installation (100) for delivering a gas mixture containing NO to a patient, comprising: - an NO delivery device (1) supplied with a gas containing NO in a given initial proportion, and configured to deliver the NO-containing gas, - a breathing circuit (20; 21) comprising an injection device (24) configured to mix the NO-containing gas from the NO delivery device (1) with a flow of O□-containing breathing gas 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 device (1) comprises: - an internal gas circuit (200) for conveying the NO-containing gas, - primary and secondary flow control means (220, 221) configured to control the flow of NO-containing gas delivered by the internal gas circuit (200), - control means (210) with a processor (211) configured to: ▪ determine at least one setpoint flow rate of NO-containing gas to be supplied to the injection device (24), based on at least one measurement of respiratory gas flow performed and provided by the flow sensor (25), and ▪ control at least a portion of the flow control means (220, 221) to supply the NO-containing gas at the determined setpoint flow rate, - and storage means (212), characterized in that: - the storage means (212) are configured to store successive setpoint flow rates of NO-containing gas determined by the control means (210), and - in the event of an interruption in the transmission to the control means (210) of any measurement of respiratory gas flow by the flow sensor (25), the control means (210) are configured to control said flow control means (220, 221) to supply the NO-containing gas at a backup flow rate obtained or calculated from one or more setpoint flow rates of NO-containing gas that have been determined by the control means (210) and stored by the storage means (212), prior to said transmission interruption.

2. Installation according to claim 1, characterized in that the control means (210) are configured to determine successive setpoint flow rates of NO-containing gas based on a plurality of successive respiratory gas flow measurements taken 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 setpoint flow rates of NO-containing gas that have been determined by the control means (210).

4. Installation according to claim 1, characterized in that the backup flow rate is obtained or calculated based on a plurality of setpoint flow rates determined by the control means (210) over a given duration (dt) prior to said transmission interruption.

5. Installation according to claim 4, characterized in that the backup flow rate is calculated by averaging the setpoint flow rates that have been stored during the given time period (dt).

6. Installation according to claim 4, characterized in that the given time period (dt) is less than or equal to 30 seconds, preferably less than or equal to 20 seconds, and 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 least one setpoint flow rate of NO-containing gas to be supplied to the injection device (24), based on at least one respiratory gas flow measurement taken and provided by the flow sensor (25), a setpoint NO concentration corresponding to the desired final proportion of NO in the combined gas mixture, and the initial proportion of NO in the NO-containing gas supplying the NO delivery device (1).

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

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

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

11. Installation according to any one of claims 4 to 6, characterized in that the given duration (dt) is fixed and stored by the storage means (212), preferably the storage means are integrated into the control means (210).

12. Installation according to claim 9, characterized in that the target NO concentration is between 1 and 80 ppmv, typically between 5 and 40 ppmv.

13. Installation according to claim 9, characterized in that the dose control means are part of a human-machine interface (HMI) or a graphical user interface (GUI).

14. Installation according to claim 9, characterized in that the dose adjustment means comprise one or more touch-sensitive keys, operable by the user, displayed on a digital touchscreen.

15. Installation according to claim 1, characterized in that the control means (210) comprise at least one microprocessor arranged on at least one electronic board.

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