Medical ventilator displaying the patient's airway opening pressure

Abstract

Title of the Invention: Medical Ventilator Displaying Patient Airway Opening Pressure. The invention relates to a medical ventilator (1) comprising gas supply means (2) for supplying breathing gas to a patient circuit (3), pressure measurement means (4), flow rate determination means (5), data processing means (10) for processing pressure and / or flow rate measurements, display means (11), and storage means (10.3) for storing a pressure / volume compliance curve of the circuit (C1) representing the compliance of the breathing circuit. The data processing means (10) are configured to perform an airway opening pressure determination, and the display means (11) display the airway opening pressure value (20). The airway opening pressure is used to adjust a PEEP valve (13) arranged on the patient circuit (3). Abstract Figure: Figure 1

Description

Title of the invention: Medical ventilator displaying the patient's airway opening pressure

[0001] The invention relates to a medical ventilator, that is to say a respiratory assistance device capable of supplying a respiratory gas, such as air, oxygen or an air / oxygen mixture, allowing the determination and display of the patient's airway opening pressure or AOP (for Airways Opening Pressure in English) of a patient receiving the respiratory gas.

[0002] Acute respiratory distress syndrome (ARDS) is a common cause of death in humans. Its management requires the application of so-called "protective" ventilation to patients, which is generally implemented by a respiratory support device, also called a medical ventilator, with personalization of the ventilation parameters for each patient, typically the flow, pressure and / or the respiratory rate.

[0003] A phenomenon known as airway closure has been reported in 23 to 52% of patients with acute respiratory distress syndrome (ARDS).

[0004] Therefore, detection of airway closure and measurement of airway opening pressure are essential to adapt ventilation to each patient.

[0005] Indeed, setting a positive expiratory pressure (PEP) lower than the airway opening pressure can alter the measurement of the patient's respiratory mechanics.

[0006] In addition, cyclic openings and closings of the small airways can also occur and promote ventilator-induced lung injury.

[0007] There is therefore a risk to patients when ventilation parameters are poorly chosen or inadequately chosen.

[0008] A problem is therefore to be able to determine a possible closure of the airways in ARDS patients and to measure the airway opening pressure (AOP) when this closure of the airways is present in order to avoid a misinterpretation of the curves and calculations of respiratory mechanics and also to operate a personalization of ventilation based on the analysis of the phenomenon of closure of the airways, in order to avoid or minimize the risks for the patients.

[0009] One solution of the invention relates to a medical ventilator, i.e., a respiratory / ventilatory support device, for supplying a respiratory gas to a patient including: - means of supplying gas to provide a breathing gas, - a patient circuit supplied with respiratory gas by the gas supply means, - Pressure measurement devices configured to determine the gas pressure in the patient circuit, - flow rate determination devices configured to determine the respiratory gas flow rate in the patient circuit - data processing means comprising at least one (micro)processor for processing pressure and / or flow measurements taken by pressure measuring means and flow determination means, - display means controlled by data processing means, and - means of memorization to memorize a pressure / volume compliance curve of the circuit (P-Vcircuit_patient) representing the compliance of the respiratory circuit.

[0010] Furthermore, the medical ventilator further includes selection means, which can be activated by the user to initiate a determination of the airway opening pressure (AOP), and the data processing means are configured to perform an AOP pressure determination in response to actuation by the user of the selection means: a. by controlling the gas supply means to provide respiratory gas at a so-called "low" respiratory rate of between 2 and 10 ventilatory cycles per minute, and at a so-called "slow" insufflation rate of between 2 and 10 L / min until an inspiratory volume of between 200 and 1500 mL or a maximum pressure (Pmax) of between 20 and 60 cmH20 is obtained, b. by ordering a display on the display means of the stored circuit compliance pressure / volume curve (P-Vcircuit_patient) and a pressure / volume curve corresponding to the "slow" flow insufflation (P-Vflow_slow), the stored "slow" flow insufflation pressure / volume curve (P-Vcircuit_patient) being displayed superimposed on the circuit compliance pressure / volume curve (P-Vcircuit_patient), c. by searching for and locating on the pressure / volume insufflation curve at "slow" flow rate (P-Vslow_flow), an inflection point corresponding to a change in slope of said pressure / volume insufflation curve at "slow" flow rate (P-Vslow_flow) with separation of the pressure / volume insufflation curve at "slow" flow rate (P-Vslow_flow) from the pressure / volume curve of circuit compliance (P-Vcircuit_patient), and d. by determining the pressure value at the inflection point located on the "slow" flow curve (P-Vslow_flow).

[0011] In addition, the data processing means are further configured to command a display on the display means of the value of the AOP pressure, i.e. the patient's airway opening pressure, corresponding to the pressure value having been determined at the present inflection point of the "slow" flow curve (P-Vslow_flow).

[0012] In the context of the invention, in order to simplify understanding, the following abbreviations and / or simplifications are used: - "AOP pressure" to designate the opening pressure of the channels patient's airways; - "compliance curve" to designate the pressure / volume curve of circuit compliance (P-Vcircuit_patient); - "slow flow curve" to designate the pressure / volume curve at low flow "slow" (P-V slow_speed). - "%vol." means percentage by volume. - "O2" refers to oxygen. - The terms "means of" are considered to be totally equivalent and interchangeable with the terms "devices of", for example the terms "means of information processing" can be replaced by "information processing device", the terms "means of display" can be replaced by "display device", the "means of storage" can be replaced by "storage device"...

[0013] Depending on the embodiment considered, the medical ventilator of the invention may comprise one or more of the following features: - the patient circuit includes an inspiratory branch and an expiratory branch. - the means of supplying gas provide the breathing gas at the insufflation rate for a sufficient duration to obtain the desired inspiratory volume between 200 and 1500 mL or the desired maximum pressure (Pmax) between 20 and 60 cmH20. - said sufficient duration results from the setting of the flow rate and the desired inspiratory volume. - said sufficient duration is preferably less than 60 seconds, for example in the range of 1 to 45 seconds. - the inspiratory branch and the expiratory branch are fluidly connected to a connecting piece, typically a Y-piece. the patient circuit is fluidly connected to a respiratory interface, such as a respiratory mask, an endotracheal intubation tube or other, the inspiratory branch supplies the respiratory gas to the respiratory interface, the respiratory gas contains oxygen (O2) in a proportion of at least 20% vol., preferably at least 21% vol. The breathing gas is air, oxygen, or an air / oxygen mixture. the inspiratory branch is fluidly connected to the means of gas supply, in particular to the gas supply outlet of a motorized turbine, the expiratory branch recovers the gas exhaled by the patient in the respiratory interface, i.e. the gas containing CO2. The means of supplying breathing gas include a source of breathing gas, such as a motorized turbine. Alternatively, means of supplying breathing gas include means of fluidic connection to a source of breathing gas, such as a wall gas outlet. data processing means including at least one (micro)processor to determine one or more gaseous volumes entering or leaving the fan from the processing carried out on the flow measurements carried out by the flow determination means. The pressure measurement means include a pressure sensor, the flow determination means include a flow sensor, the pressure measurement means are arranged in the inspiratory branch of the patient circuit. The pressure measurement devices are arranged inside the fan, i.e. in its casing. The display means are configured to operate displays, including one or more curves, numerical values, texts, messages, windows, icons... or any other information. The data processing means are further configured to control the display of information relating to the existence of an airway closure in the patient, i.e., in particular when an inflection point is detected and / or an airway closure is determined, for example, a text message indicating the presence or absence of an airway closure, such as "airway closure present" or "airway closure detected" or, conversely, "no airway closure" or "airway open", or any other equivalent message. The data processing means are further configured to order a display on the means of displaying a message in text form indicating the pressure value "x" corresponding to the determined AOP, i.e. in case of presence of closure of the airways, for example "AOP = x cmH2O", with x typically between 1 and 30 cmH2 O. data processing means comprising at least one (micro)processor implementing one or more algorithms, the data processing means comprising a microcontroller, said at least one (micro)processor being arranged on an electronic board, the data processing means being configured to determine the inspired volume and the expired volume The display means include a touch screen, i.e., a touch panel. the selection means include a virtual key displayed on the display means, in particular on the touch screen, i.e. a touch key, i.e. actuation by pressing or digital pressure. The touchscreen has a color display. The "low" respiratory rate is between 3 and 7 respiratory cycles per minute, for example around 5 respiratory cycles per minute. The "slow" insufflation flow rate is between 3 and 7 L / min, for example around 5 L / min. The data processing means are configured to command a display of the AOP pressure value as a positive pressure value, preferably expressed in cmH20 or another unit. The slow flow curve is obtained from the pressure and flow values ​​processed by the microprocessor(s). The "slow" flow curve is a curve displayed and updated in real time; compliance (e.g., the stored compliance curve) is obtained before the start of patient treatment. The patient circuit compliance is recorded before the start of patient treatment during tests to verify the machine's proper functioning, or "self-tests". This circuit compliance is then used to determine and display the compliance curve (i.e., the P-V patient_circuit curve) superimposed on the slow-flow curve (i.e., the P-V slow_flow curve). the data processing means are further configured to determine a PEP pressure from the AOP pressure that has been determined. - the data processing means are further configured to recommend (i.e. determine) a PEP pressure higher than the AOP pressure that has been determined. - the data processing means are further configured to control a display on the means of displaying the recommended PEEP pressure. - the pressure value of AOP is between 1 and 30 cmH20. - the means of supplying gas include a motorized turbine controlled by the data processing means. - the means for measuring pressure include a pressure sensor and / or the means for determining flow include a flow sensor. - it includes a PEEP valve arranged on the patient circuit, specifically on the expiratory branch. - the data processing means are configured to adjust the PEP pressure of said PEP valve to the recommended PEP pressure. - the data processing means are configured to adjust the PEP pressure of said PEP valve in response to the activation by the user of a setting confirmation means, preferably after the user digitally presses a virtual confirmation key displayed on the digital screen. - it includes means of supplying electrical current to power the fan, such as a mains connection (110 / 220V) and / or a rechargeable battery.

[0014] The invention will now be better understood with reference to the following detailed description, given by way of illustration but not limitation, with reference to the accompanying figures, among which:

[0015] [Fig.1] schematically illustrates an embodiment of a medical ventilator according to the invention.

[0016] [Fig.2] schematically illustrates one embodiment of the display of pressure / volume curves superimposed images showing the inflection point appearing in the event of closure of the patient's airways.

[0017] [Fig.1] schematically illustrates an embodiment of a medical ventilator 1 according to the invention, which includes means for supplying gas 2 to provide respiratory gas to a patient in need, typically a person suffering from ARDS.

[0018] Here, the gas supply means 2 comprise a motorized turbine 2.1 supplied with air by an air supply duct 2.2 connected to the ambient atmosphere and with oxygen by an oxygen supply duct 2.3 that can be connected to an oxygen source (not shown), such as a pressurized oxygen cylinder or a socket hospital wall supplied by an oxygen supply line.

[0019] However, according to another embodiment (not shown), the gas supply means 2 include fluidic connection means to a source of breathing gas, such as a wall gas outlet, and one or more piloted valves, such as solenoid valves controlled by the data processing means 10.

[0020] Typically, the breathing gas supplied by the gas supply means 2 is air, oxygen or an air / oxygen gas mixture (>20%vol. O2, preferably >21%vol. O2 about).

[0021] The gas supply means 2 supply a patient circuit 3 comprising an inspiratory branch 3.1 and an expiratory branch 3.2, such as gas passages or conduits, in particular flexible hoses, fluidly connected to a respiratory interface 6, such as a breathing mask or an endotracheal tube, via a connecting piece 6, namely a Y-piece or similar.

[0022] The inspiratory branch 3.1 carries the breathing gas to the breathing interface 6, which is inhaled by the patient during inspiratory phases, while the expiratory branch 3.2 carries the CO2-laden gases exhaled by the patient to the breathing interface 6 during expiratory phases. The expiratory branch 3.2 is connected to an exhaust outlet 9 for the exhaled gases of the ventilator 1, which is fluidically connected to the ambient atmosphere.

[0023] A PEEP valve 13 is arranged on the patient circuit 3, in particular on the expiratory branch 3.2. The data processing means are configured to set the PEEP pressure of said PEEP valve 13 to the proposed PEEP pressure, as explained below, in particular in response to the activation by the user of a setting confirmation means, preferably after digital pressing by the user on a virtual confirmation key displayed on the digital display 11.1.

[0024] Furthermore, the patient circuit 3, in particular the inspiratory branch 3.1, includes pressure measurement means 4, such as a pressure sensor, enabling the measurement, i.e. determination, of the gas pressure in the inspiratory branch 3.1, and flow determination means 5, such as a flow sensor, used to determine the respiratory gas flow rate in the patient circuit 3.

[0025] Preferably, the flow determination means 5 are arranged near the outlet 2.4 of the gas supply means 2, i.e. immediately downstream of the turbine 2.1.

[0026] Furthermore, the pressure measuring means 4 are located upstream of the connecting piece 6, i.e. the Y-shaped piece.

[0027] The medical ventilator 1 includes data processing means 10, also called control means, comprising one or more microprocessors 10.1 arranged on an electronic board 10.2, which allow data to be processed and control or control elements of the fan 1, including the operation of the turbine 2.1, the displays on the display screen 11, preferably a touch panel screen 11.1, or others.

[0028] The pressure measuring means 4 and the flow determining means 5, i.e. the pressure and flow sensors, are electrically connected to the data processing means 10, typically to the (micro)processor 10.1, in order to provide them with pressure and flow measurements (i.e. values ​​or signals), and the data processing means 10 are configured to process the pressure and flow measurements from the pressure measuring means 4 and the flow determining means 5, i.e. the pressure and flow sensors.

[0029] The data processing means 10 can for example deduce one or more gas volumes entering or leaving the ventilator 1, typically from the patient circuit 3, i.e. respiratory gas supplied to the patient or CO2-rich gases exhaled by the patient.

[0030] The ventilator 1 also includes storage means 10.3, typically computer memory, such as flash memory, RAM, or similar, used to store a compliance pressure / volume curve (i.e., a curve or compliance values ​​allowing such a curve to be established) representing the compliance of the respiratory circuit (i.e., curve Cl in [Fig. 1]) or values ​​such as the AOP value. The storage means 10.3 are preferably arranged on the electronic board 10.2 and electrically connected to the (micro)processor 10.1

[0031] Means of supplying electrical current, such as a connection to the mains (110 / 220V), for example electrical cables, and / or a rechargeable battery, supply the fan 1, in particular the turbine 2.1, the sensors 4, 5, the data processing means 10, the touch screen 11.... and the other components requiring electrical current to operate.

[0032] All or part of the various components are arranged in an external casing or shell 1.1 of the fan 1.

[0033] According to the invention, it is desirable to be able to determine a possible closure of the airways in ARDS patients, who are ventilated with a medical ventilator 1, such as the one described above, and to measure the opening pressure of their airways (i.e. the AOP pressure) when it is present, in order to avoid a misinterpretation of the curves and calculations of respiratory mechanics and also to personalize ventilation based on the analysis of the phenomenon of closure of the airways, and in order to avoid or minimize the risks for the patients.

[0034] To achieve this, the fan 1 is equipped with selection means 11.2, which can be operated by the user to start a determination of the airway opening pressure or AOP pressure, that is to say to start the procedure for determining a possible closure of the patient's airway of the corresponding AOP pressure, as described below.

[0035] Preferably, the selection means 11.2 include a selection key, in particular a virtual key, i.e. a touch key, displayed on the touch screen 11.1 which the user presses with a finger, such as his index finger, to initiate the procedure for determining an AOP press.

[0036] The selection key can be permanently displayed on screen 11.1 or only be displayed after the user, i.e. a healthcare worker, has made a choice of AOP pressure determination procedure within a dedicated menu displayed on screen 11.1.

[0037] According to another embodiment, the ventilator 1 may also include a specific button, for example arranged on its casing 1.1, the actuation of which triggers the start of the procedure for determining the opening pressure of the airways, i.e. the AOP pressure.

[0038] In all cases, in response to such actuation by the user of the selection means 11.2, the data processing means 10, typically the processor 10.1, are configured to operate a determination of a possible closure of the patient's airways and, when they are closed, a determination of the corresponding AOP pressure, i.e. to initiate an AOP pressure determination procedure.

[0039] To achieve this, the data processing means 10 first control the breathing gas supply means 2, such as the motorized turbine 2.1, to supply the breathing gas (i.e., O2 content > 20% vol.), for example air, O2, or an air / O2 mixture, at a so-called "low" respiratory rate of between 2 and 10 ventilatory cycles per minute, for example, on the order of 5 ventilatory cycles per minute, and at a so-called "slow" insufflation flow rate of between 2 and 10 L / min, for example, on the order of 5 L / min, for a sufficient duration to obtain an inspiratory volume of between 200 and 1500 mL or a maximum pressure (Pmax) of between 20 and 60 cmH2O. The flow rate and inspiratory volume settings determine the duration. In general, this duration is less than 60 seconds, for example in the range of 1 to 45 seconds.

[0040] Furthermore, the data processing means 10 control a display on the display means 11 of the compliance pressure / volume curve (curve Cl in [Fig.2]) of the circuit (P-Vcircuit_patient) which has been previously stored by the storage means 11.3 and of a pressure / volume curve (curve C2 in [Fig.2]) corresponding to the "slow" flow insufflation (P-Vslow_flow) determined during the given duration.

[0041] The pressure / volume insufflation curve at "slow" flow (P-Vcircuit_patient) (i.e. curve C2), more simply called the "slow flow curve", is displayed superimposed on the stored compliance pressure / volume curve (P-Vcircuit_patient) (i.e. curve Cl), more simply called the "compliance curve", as illustrated in [Fig.2].

[0042] Regarding the patient circuit compliance curve (P-Vcircuit_patient), it is determined beforehand, for example, during a self-test procedure or similar procedure of ventilator 1. The patient circuit compliance is recorded before the start of patient treatment during tests to verify the proper functioning of the machine or “self-tests”. This circuit compliance is then used to determine and display the compliance curve, i.e., the P-Vcircuit_patient curve, superimposed on the slow-flow curve, i.e., the P-Vslow_flow curve.

[0043] Indeed, a self-test procedure of a ventilator 1 is generally carried out before ventilating, i.e. treating, a patient in order to check the proper functioning of the sensors or other components, and to take into account the characteristics of the patient circuit 3 of the ventilator 1.

[0044] To do this, a sealing plug can be inserted into the patient circuit 3, typically at the Y-piece 7 of the patient circuit 3 so as to prevent the flow of respiratory gas, such as air, delivered by the gas supply means 2 from exiting the circuit 3 through the respiratory interface 6, e.g. mask 6 or similar.

[0045] Next, the actual self-test procedure is launched, for example via a specific selection menu displayed on the screen 11 of the fan 1.

[0046] This includes an insufflation of a given flow rate of respiratory gas into the inspiratory branch 3.1 of the patient circuit 3 with measurement of the corresponding pressure by the pressure sensor 4, until a set maximum pressure (Pmax) is reached, for example of the order of 60 cmH20.

[0047] By carrying out an integration of the gas flow rate, we can then calculate the volume of gas (Vcircuit_patient) delivered in the patient circuit 3.

[0048] The data processing means 10, typically the processor 10.1, can therefore determine the compliance of the circuit (Ccircuit_patient) using the values ​​of maximum pressure set (Pmax) and of volume of gas delivered thus determined (Vcircuit_patient), by performing the following calculation: Ccircuit_patient = Vcircuit_patient / Pmax.

[0049] In fact, compliance is considered to be linear, so only two flow and pressure measurement points are taken (including the point at zero flow and pressure). The insufflated flow rate is constant to obtain the patient circuit volume V.

[0050] Once the circuit compliance has been determined, as well as other verification procedures internal procedures, the self-testing procedure is stopped and the sealing plug can be removed so that ventilator 1 can be used to treat a patient.

[0051] The data processing means 10, typically the processor 10.1, are further configured to search and locate on the slow flow curve, i.e. curve C2 on [Fig.2], any inflection point PI from which there is a change in slope of the slow flow curve, (P-Vslow_flow) accompanied by a separation of the slow flow curve (i.e. curve C2) from the circuit compliance curve (P-Vpatient_circuit) (i.e. curve Cl), i.e. a sudden separation of the two curves Cl, C2 from each other, as illustrated on [Fig.2].

[0052] If no inflection point PI is found, this means that there is no closure of the patient's airway. Conversely, if an inflection point PI, i.e., the inflection point PI on [Fig. 2], is found and located on the slow-flow curve C2, this means that the patient in question has an airway closure and the AOP pressure then corresponds to the pressure value at the inflection point PI.

[0053] The data processing means 10, typically the processor 10.1, are therefore configured to determine the pressure value at the inflection point PI which has been located on the pressure / volume insufflation curve at "slow" flow rate (P-Vslow_flow), i.e. C2 on [Fig.2].

[0054] Once determined, the pressure value at the inflection point PI has been determined is displayed on the display screen 11.1 of the display means 11, given that the pressure of AOP corresponds to the pressure value at the inflection point PI of the "slow" flow curve (P-Vslow_flow) ), i.e. C2 on [Fig.2].

[0055] [Fig.2] schematically illustrates an example of real-time monitoring of pressure curves / volume Cl, C2 obtained from the pressure and flow values ​​processed by microprocessor 10.1, namely the slow flow curve (P-Vslow_flow), designated by "C2", and the compliance curve (P-Vpatient_circuit), designated by "Cl", obtained from the pressure values ​​processed by microprocessor 10.1 and the circuit compliance measured during a self-test procedure, as explained above.

[0056] In particular, it is important that the gas be insufflated at a slow flow rate when establishing the slow flow curve because this allows the resistive component of airway pressure to be eliminated, making it possible to detect a closure of the patient's airway by means of a localization on the curves (Cl, C2) of any abrupt change in slope, i.e. the inflection point PI present in case of airway closure but absent when the patient's airway is not closed, which inflection point PI allows the determination of the AOP pressure.

[0057] In the graph of [Fig.2], the x-axis gives pressure values, expressed in cmH20, and the y-axis gives volume values, expressed in mL. Of course, other units / quantities could be used.

[0058] We see that an inflection point PI appears where the two curves Cl, C2 diverge sharply from each other, which indicates a closure of the airways of the patient in question and therefore the existence of an AOP pressure.

[0059] The pressure value of AOP then corresponds to the positive pressure value at the inflection point PI, namely here a pressure of 22.9 cmH20, as indicated by the x-axis.

[0060] This information, namely the existence of an airway closure and the value of the AOP pressure, is then displayed in a dedicated display window 12 of the display screen 11.1. The display is controlled by the data processing means 10, in particular by the processor 10.1.

[0061] The display within the display window 12 may include various pieces of information useful to healthcare personnel, namely: - a text message indicating whether or not there is an airway closure, such as “airway closure present” or “no airway closure”; and / or - a message in text form indicating the value "x" of the AOP pressure in case of airway closure, for example "AOP = x cmH20", with x between 1 and 30 cmH20.

[0062] Preferably, the data processing means 10 can also be configured to determine and propose a ventilatory strategy, i.e. an action to be taken by the care staff, according to the value of the patient's AOP pressure having been determined.

[0063] Thus, if the PEEP of the PEEP valve 13 is set to a value lower than the AOP pressure value, the data processing means 10 can propose a change in the PEEP setting to a value higher than the AOP pressure value (preferably to be considered in association with other available clinical data) and command a display of this PEEP setting recommendation on the display means 11.

[0064] For example, the data processing means 10 can command the display of a message (in text form) recommending the setting of the PEP, such as “maintain PEP” or “increase PEP”, either in the window 12 or elsewhere on the screen 11.1. The recommended PEP value is also advantageously displayed.

[0065] Thanks to the invention, by knowing the AOP pressure value, healthcare personnel can adjust the positive end-expiratory pressure or PEEP of the PEEP valve 13 to a value above the AOP pressure in order to keep the airways open and thus limit the risk of lung injury in the patient.

[0066] Generally, according to the invention, the detection of the closure of the patient's airways and the determination of the airway opening pressure (AOP pressure) by analysis of the compliance curve and the slow flow curve (Cl, C2), as explained above, are done automatically within the medical ventilator 1.

[0067] A medical ventilator 1 according to the invention is particularly well suited to the treatment of patients, i.e., men, women, or children, suffering from acute respiratory distress syndrome (ARDS). Indeed, it allows for real-time monitoring and detection of airway closure and determination of the airway opening pressure (AOP) of ventilated patients with ARDS.

Claims

1. Demands Medical ventilator (1) comprising: - means for supplying gas (2) to provide a breathing gas, - a patient circuit (3) supplied with respiratory gas by the gas supply means (2), - pressure measurement means (4) configured to determine the gas pressure in the patient circuit (3), - flow determination means (5) configured to determine the respiratory gas flow rate in the patient circuit (3), - data processing means (10) comprising at least one processor (10.1) for processing pressure and / or flow measurements taken by pressure measuring means (4) and flow determination means (5), - display means (11) controlled by data processing means (10), and - means of memorization (10.3) to memorize a pressure / volume compliance curve of the circuit (Cl) representing the compliance of the respiratory circuit, characterized in that: - it further includes selection means (11.2), which can be activated by the user to begin a determination of the airway opening pressure (or AOP pressure), - the data processing means (10) are configured to perform a determination of the AOP pressure in response to an actuation by the user of the selection means (11.2): a. by controlling the gas supply means (2) to provide breathing gas at a so-called "low" respiratory rate of between 2 and 10 respiratory cycles per minute, and at a so-called "slow" insufflation rate of between 2 and 10 L / min, until an inspiratory volume of between 200 and 1500 mL or a maximum pressure (Pmax) of between 20 is obtained and 60 cmH2O, b. by ordering a display on the display means (11) of the stored circuit compliance pressure / volume curve (Cl) and a pressure / volume curve corresponding to the slow flow insufflation (C2), the slow flow insufflation pressure / volume curve (C2) being displayed superimposed on the stored circuit compliance pressure / volume curve (Cl), c. by searching for and locating on the slow-flow insufflation pressure / volume curve (C2), an inflection point (PI) corresponding to a change in slope of said slow-flow insufflation pressure / volume curve (C2) with separation of the slow-flow insufflation pressure / volume curve (C2) from the circuit compliance pressure / volume curve (Cl), and d. by determining the pressure value at the inflection point (PI) located on the slow flow curve (Cl), - and the data processing means (10) are further configured to control a display on the display means (11), of the pressure value of AOP (20) corresponding to the pressure value at the inflection point (PI) having been determined on the slow flow curve (C2).

2. Ventilator according to claim 1, characterized in that the data processing means (10) are further configured to control a display on the display means (11), of information relating to the existence of a closure of the patient's airways.

3. Fan according to claim 1, characterized in that the display means (11) comprise a touch screen (11.1).

4. Fan according to claim 1, characterized in that the selection means (11.2) include a virtual key displayed on the display means (11), in particular on the touch screen (11.1).

5. Fan according to claim 1, characterized in that the data processing means (10) are further configured to control a display on the display means (11) of a recommended PEP pressure, said recommended PEP pressure being determined from the AOP pressure (20) having been determined, preferably the recommended PEP pressure is greater than the AOP pressure (20) having been determined.

6. Fan according to claim 1, characterized in that the pressure value of AOP (20) is between 1 and 30 cmH20.

7. Fan according to claim 1, characterized in that the gas supply means (2) comprise a motorized turbine (2.1) driven by the data processing means (10).

8. Fan according to claim 1, characterized in that the pressure measurement means (4) comprise a pressure sensor and / or the flow determination means (5) comprise a flow sensor.

9. Ventilator according to claims 1 and 5, characterized in that it comprises a PEEP valve (13) arranged on the patient circuit (3) and the data processing means (10) are configured to set the PEEP pressure of said PEEP valve (13) to the recommended PEEP pressure.

10. Fan according to claim 1, characterized in that the data processing means (10) are configured to drive the gas supply means (2) to supply breathing gas at a so-called "low" respiratory rate of between 3 and 7 ventilatory cycles per minute and / or at a so-called "slow" insufflation rate of between 3 and 7 L / min.