MEDICAL VENTILATOR WITH DISPLAY OF PATIENT'S LUNG RECRUITABILITY

Description

[0001] The invention relates to a medical ventilator, i.e. a respiratory assistance device, for providing a real-time clinical diagnosis of a ventilated patient suffering from respiratory distress, i.e. ARDS, in the form of a recruitability index of the lungs of the patient in question, namely a recruitment / inflation ratio or recruitability ratio, called RI ratio.

[0002] Acute respiratory distress syndrome, or ARDS, is a common cause of death in humans. ARDS is characterized by severe lung damage, of which only a small portion can be recruited, i.e., ventilated and able to participate in pulmonary gas exchange, namely the supply of inspired oxygen (O 2 ) and the elimination of expired carbon dioxide (CO 2 ). Patients with ARDS have what are called "baby lungs."

[0003] Ventilatory management of ARDS requires the application of so-called "protective" ventilation, for example using a medical ventilator such as that described by US 2022 / 0096765, as well as personalization of the ventilatory parameters to adapt them to the patient in question.

[0004] Thus, an increase in positive end-expiratory pressure or PEEP (also called PEEP in English for Positive End-Expiratory Pressure) compared to a previously set PEEP level can allow an additional part of the lungs to be recruited, that is, to open parts of the lung that were not participating in gas exchange before the application of this PEEP. However, too high a PEEP could also distend part of the lungs and be harmful to the patient.

[0005] According to a common definition, PEEP can be defined as the residual gas pressure maintained above atmospheric pressure in the airways of a person, i.e. a patient, at the end of expiration. PEEP allows ventilation of the pulmonary alveoli that may be collapsed and, in general, increases pulmonary gas exchange and reduces the patient's work of breathing.

[0006] The ability to recruit the lungs by increasing PEEP depends on the individual, that is, the patients to be treated. We distinguish: so-called "recruiter" patients for whom an increase in PEEP allows for the recruitment of an additional part of the lungs. This recruitment, when effective, improves gas exchange and proves beneficial for patients. so-called "non-recruiter" patients for whom an increase in PEEP does not allow for the recruitment of an additional part of the lungs and can even be harmful for the patient since it can lead in particular to distension of the lungs, hemodynamic instability, etc.

[0007] We therefore understand that it is essential to be able to assess the recruitability of each patient in order to personalize their ventilation, in particular the PEEP setting to be applied, to ensure effective ventilation of the patient and avoid harmful ventilation if the patient is not a recruiter.

[0008] Although different methods have been proposed to determine the PEEP setting, for example the multiple pressure / volume curve method, the use of electro-impedance tomography (EIT), the adaptation of PEEP according to the value of the inspired oxygen fraction (FiO 2 ) set on the ventilator or according to the patient's respiratory mechanics (i.e. driving pressure, plateau pressure, etc.), these generally give random results and are often difficult to implement in practice, for example in a hospital setting at the patient's bedside.

[0009] Furthermore, we also know the document Chen Lu et al, Potential for Lung Recruitment Estimated by the Recruitment-To-Infliction Ratio in Acute Respiratory Distress Syndrom; A Clinical Trial; American Journal of Respiratory and Care Medicine; vol. 201, n°2, 15 Jan. 2020; p. 178-187 ,which teaches trials to assess lung recruitment in patients with ARDS. Patients are ventilated by a medical ventilator but the measurements are processed by an independent computer connected to the ventilator, which uses a specific software program, namely MATLAB (see paragraph Analysis, p. 182).

[0010] This method is inconvenient because it requires the use of a computer and connections between the computer and the fan.

[0011] A problem is therefore to be able to provide a reliable assessment of the recruitability of a patient with ARDS ventilated by a medical ventilator in order to be able to personalize their ventilation, in particular the PEEP setting to be applied, to ensure effective, non-deleterious ventilation, in particular if the patient is non-recruiting, and this, without encountering the aforementioned drawbacks.

[0012] One solution involves a medical ventilator, i.e. a respiratory assistance device, comprising: a gas circuit comprising an inspiratory branch for conveying a respiratory gas and an expiratory branch for evacuating the exhaled gas to the atmosphere, flow rate measuring means configured to determine at least one gas flow rate in the gas circuit, pressure measuring means configured to determine at least one gas pressure in the gas circuit, a PEEP valve arranged on the expiratory branch, a graphic display, and microprocessor control means cooperating with the flow rate measuring means, the pressure measuring means, the PEEP valve and the graphic display.

[0013] Furthermore, according to the invention: the medical ventilator control means are configured to: a) determine an RI ratio from the flow and pressure measurements made by the flow measurement means and the pressure measurement means, where the RI ratio is such that: R − I ratio = Crec / Crs where: Crec is the compliance of the patient's recruited lungs and Crs is the compliance of the respiratory system, b) command a display on the graphic display of the calculated RI ratio, and the graphic display is configured to display the RI ratio.

[0014] According to the invention, we call: PEEP: the residual gas pressure maintained by a medical ventilator above atmospheric pressure (i.e. 1 atm), in the ventilator's patient circuit, therefore indirectly also in the airways of a person, i.e. a patient, at the end of expiration, i.e. at the end of each of their expiratory phases. "RI ratio": the recruitment / inflation ratio of the lungs of a person, typically a patient (for recruitment to inflation ratio in English) which estimates the capacity of an additional part of the lungs to be recruited, that is to say opened, to participate in gas exchanges by implementing PEP. patient: a person or human being (e.g. man, woman, etc.) whether an adult, an adolescent, a child, a baby, a newborn or other suffering from a respiratory disorder or pathology, such as ARDS or other, requiring artificial ventilation.

[0015] According to the invention, the determination of the RI ratio is carried out directly in the medical ventilator and does not require any computer or other computer device connected to the ventilator, used for this determination. In other words, according to the invention, the determination of the RI ratio is done automatically within the control means of the medical ventilator.

[0016] Integrating this determination of the RI ratio into a medical ventilator had never been done or suggested until now. It constitutes an important advance in the treatment of ARDS patients. Indeed, it is now possible to evaluate the recruitability of each patient using the medical ventilator itself, i.e. in real time during ventilation applied to the patient, and therefore to be able to immediately feedback at the level of said ventilator in order to personalize the ventilation applied to the patient in question, in particular the PEEP setting applied to him. This ensures effective and non-deleterious ventilation even when the patient is non-recruiting.

[0017] Depending on the embodiment considered, the medical ventilator of the invention may comprise one or more of the following features: the control means are configured to determine the compliance (Crs) of the respiratory system (Crs) such that: Crs = Vte / (P flat - low_measured PEEP) where: ∘ P flat is the plateau pressure at low PEEP, where: low PEEP = high PEEP - A with high PEEP between 10 and 30 cmH2O and A between 5 and 15 cmH2O, ∘ low_measured PEEP is a low PEEP value measured by the pressure sensor, and o Vte is the tidal volume expired by the patient (at low PEEP). the control means are configured to determine the compliance (Crec) of the patient's recruited lungs such that: Crec = ΔVrec / PEP haute _ mesurée − PEP basse _ mesurée where ΔVrec is the gas volume recruited with: ΔVrec = Δ EELV mesuré − Δ EELV estimé − Vte where: o ΔEELV measured is the gas volume ΔEELV measured and generated by the transition between high PEEP and low PEEP, and o ΔEELV estimated = Crs. (high PEEP_measured - low PEEP_measured). the control means are further configured to determine a recruitability status of the patient by comparing the RI-ratio determined for the patient in question with a given recruitability threshold value, e.g. prefixed, and by determining that: i) the patient is non-recruitable when the RI ratio is less than or equal to the recruitability threshold value, or ii) the patient is recruitable when the RI ratio is greater than the recruitability threshold value. the recruitability threshold value is adjustable, i.e. modifiable by the user. the recruitability threshold value is between 0 and 2. the recruitability threshold value is equal to 0.5. the control means are further configured to command a display on the graphic display of the patient's recruitability status.the graphic display is configured to display the recruitability status of the patient. the control means are configured to determine the calculated RI ratio, after activation by the user of a selection means displayed on the graphic display, preferably by digitally pressing a virtual key or a numeric keypad. the control means are further configured to determine a recommendation for action to be taken as a function of the recruitability status having been determined and further control a display on the graphic display of the recommendation for action to be taken. the graphic display is configured to display the recommendation for action to be taken. it comprises storage means configured to store recommendations for action to be taken including an increase in PEEP, a decrease in PEEP or a maintenance of PEEP.it further comprises a micro-blower as a gas source supplying the inspiratory branch of the gas circuit with air or an air / oxygen mixture. the control means comprise one or more microprocessors. the control means comprise (at least) one electronic card carrying the microprocessor(s). the microprocessor(s) implements one or more algorithms. it comprises storage means, such as a computer memory. the storage means are arranged on the electronic card. it comprises power supply means. the power supply means comprise an electric cord and a mains connection plug (110 / 220 V) and / or one or more rechargeable batteries, and possibly a current transformer. the graphic display is a digital touch screen, iewith a touch-sensitive digital panel, i.e. capable of being controlled by digital presses by the user on the screen panel, to make choices, selections, entries, validations, launch actions, activate functionalities, etc. or perform other actions. the display screen is of the color display type. the display screen is configured to display selection means, such as a numeric keypad or one or more digital selection keys. it comprises a source of pressurized gas to supply a gas flow to the inspiratory branch. the source of pressurized gas is a motorized micro-blower, i.e. with an electric motor. the control means are configured to control the micro-blower. the control means are configured to control the operation of the micro-blower, in particular the accelerations or decelerations of the micro-blower.the electrical supply means supply electrical current to the components requiring electrical current to operate, such as the control means, the motorized micro-blower, the display screen or other elements. the control means are further configured to control a display on the graphic display of at least one additional item of information chosen from the tidal volume (Vte), the respiratory rate (Fr) and the PEP. the graphic display is further configured to operate a display of said at least one additional item of information.

[0018] The invention will now be better understood thanks to the following detailed description, given for illustrative but non-limiting purposes, with reference to the appended figures among which: Fig. 1 schematizes an embodiment of the internal architecture of a medical ventilator according to the invention; and Fig. 2 schematizes an example of display on the display screen of a medical ventilator according to the invention.

[0019] Fig. 1 schematizes an embodiment of the internal architecture of a medical ventilator 1 according to the invention, that is to say a ventilatory assistance device, usable for treating a person, that is to say a patient, suffering from ARDS or other respiratory pathologies.

[0020] Ventilator 1 supplies the patient with breathing gas, such as an air / oxygen gas mixture, during each of the patient's inspiratory phases and expels exhaled gas from the patient's lungs during each expiratory phase.

[0021] The ventilator is connected to the patient via a gas circuit 2 which here has a double branch comprising an inspiratory branch 2-1 and an expiratory branch 2-2, allowing the delivery of gas supplied by a gas source.

[0022] The inspiratory branch 2-1 and the expiratory branch 2-2 are fluidically connected to a junction piece 3, such as a Y-piece, making it possible to make the junction between the two branches 2-1, 2-2. The patient interface 10, such as a mask or an intubation probe, is fluidically connected to the junction piece 3.

[0023] The supply of oxygen (O 2 ) is ensured by the inspiratory branch 2-1 and the elimination of carbon dioxide (CO 2 ) exhaled by the patient is ensured by the expiratory branch 2-2 whose terminal end leads to the atmosphere, via for example an exhaled gas outlet 2-3 located at the level of the casing 11 of the ventilator 1.

[0024] The expiratory branch 2-2 also comprises a PEEP valve 12 arranged upstream of the expired gas outlet 2-3 used to adjust the PEEP level to ensure, according to the invention, effective ventilation of the patient and to avoid harmful ventilation if the patient is non-recruiting, as explained below.

[0025] The gas circuit 2 may comprise internal gas passages arranged in the outer casing or shell 11 of the ventilator 1 and flexible conduits connecting the ventilator 1 to the patient respiratory interface 10.

[0026] The gas flow is provided by a pressurized gas source 4, namely here a micro-blower 14, also called a turbine or compressor, sucking in ambient air via an air inlet 4-1 of the fan 1 opening into the atmosphere and furthermore supplied with gaseous oxygen via an oxygen inlet 4-2 of the fan 1 through which oxygen enters from an external oxygen source connected to the fan 1 by a flexible hose, such as a pressurized oxygen cylinder, or an oxygen distribution wall outlet supplied with oxygen by an oxygen delivery pipe connected to an oxygen storage, or even an oxygen concentrator.

[0027] Alternatively, the micro-blower 14 may be replaced by a control valve (not shown) of the gas supply arranged between the air inlet 4-1 of the ventilator 1 and the inspiratory branch 2-1, for example in place of the micro-blower 14 on Fig. 1 In this case, the air inlet 4-1 of the fan 1 is supplied by a flexible conduit fluidly connected to a medical air distribution wall outlet carried by a wall of a hospital building and supplied with medical air by a medical air delivery pipe connected to a medical air storage or a medical air production installation, such as a PSA type installation, i.e. pressure swing adsorption (Pressure Swing Adsorption) making it possible to produce medical air on site, typically in a hospital building, such as a hospital, a clinic or the like.

[0028] In all cases, an air / oxygen mixture is obtained (O2 content >21% vol.) which is delivered to the patient via the inspiratory branch 2-1 of the gas circuit 2 of the ventilator 1.

[0029] Furthermore, pressure measuring means (i.e. a device) 5, such as a pressure sensor, are provided, and flow measuring means (i.e. a device) 6, such as a mass flow sensor or a differential pressure sensor, are integrated in the fan 1 on the gas circuit 2 in order to determine a pressure and a flow rate of the gas, i.e. of the air / O 2 mixture flow circulating therein.

[0030] More precisely, the pressure measuring means 5 are configured and arranged to determine at least one gas pressure, for example a pressure reflecting the pressure in the patient's airways, while the flow measuring (i.e. determining) means 6 determine at least one gas flow rate value corresponding to the gas flow rate in the gas circuit 2 ensuring the delivery of the gas coming from the ventilator 1, i.e. typically in the inspiratory branch 2-1.

[0031] Means or a control unit 7 making it possible to operate in particular the data processing, such as measurements, and the various controls of the fan 1 are provided in the fan 1. They comprise at least one microprocessor 7-1, such as a microcontroller, implementing one or more algorithms, preferably carried by an electronic card 7-2.

[0032] Furthermore, the control means or unit 7 also serve to control the micro-blower 14 (or the control valve (not shown) of the gas supply ensuring the supply of gas from one or more wall outlets) in order to supply the gas during the patient's inspiratory phases and reduce or stop this supply during his expiratory phases.

[0033] Furthermore, according to the invention, the control means or unit 7 also control the PEP valve 12 which makes it possible to adjust the patient's PEP level during gas expirations.

[0034] The desired PEEP level is set by the user on the ventilator's HMI, i.e., the caregiver, as explained below. Generally, PEEP is between 0 and 30 cmH2O, or sometimes even higher, depending on the patient category to be treated, i.e., adult, adolescent, child, newborn, or other.

[0035] The pressure measuring means 5 and the flow measuring means 6 cooperate with the control means 7. More precisely, the pressure measuring means 5 and flow measuring means 6 provide the pressure and flow measurements that they carry out to the control means 7, which then carry out processing of these data, that is to say of the measurements received, in particular to determine the volumes generated by the ventilator 1, that is to say delivered by the gas source 4, for example the inspired volume and the expired volume, from the successive gas flow measurements.

[0036] Pressure and flow measurements can be measured values ​​or signals corresponding to values ​​measured by the sensors.

[0037] The fan 1 also comprises a graphic display or display screen 8 for displaying data, information, curves or other graphic representations, alarms, settings, selections, menus, icons or the like. The display on the display screen 8 is controlled by the control means 7.

[0038] Furthermore, an electric current source 9, i.e. electrical power supply means, is also provided to supply electric current to the various components of the fan 1 requiring electric current to operate, such as the control means 7, the display screen 8, the micro-blower 14, the sensors, etc.

[0039] The electric current source 9 may comprise an internal rechargeable battery(ies) which may be associated with a current transformer, and / or means of connection to the mains (110 / 200 V), such as an electric cord provided with a connection plug or the like.

[0040] The display screen 8 is preferably a digital touch screen, i.e. a digital touch panel, i.e. one that can be controlled by digital presses by the user on the panel of the screen 8, to make choices, selections, entries, validations, launch actions, activate functionalities, etc., or perform other actions. Advantageously, the display screen 8 is of the color display type.

[0041] Preferably, the display screen 8 is configured to display means of selection, such as a specific monitoring block, of the monitoring mode and / or the recruitment / inflation ratio or “RI ratio” (for recruitment to inflation ratio in English) according to the invention, as detailed below.

[0042] A digital, i.e. tactile, press by the user, i.e. a healthcare professional, such as a doctor, on this monitoring pad displayed on the screen panel 8 allows this mode to be selected and therefore the different stages of the automatic calculation of the RI ratio to be activated, which are given below.

[0043] In other words, the user's pressing on the specific monitoring pad of the RI ratio mode displayed on the screen panel 8 of the display screen 8 is recognized and transmitted to the control means 7 which then carry out appropriate data processing, in particular determining the actions to be carried out which include the calculation of the RI ratio and its subsequent display on the display screen 8.

[0044] The calculation of the RI ratio is then done automatically by the control means 7, as detailed below.

[0045] Generally speaking, the control means 7 with microprocessor 7-1 cooperate with the flow measurement means 6, the pressure measurement means 5, the PEP valve 12, the graphic display 8 and the pressurized gas source 4, such as the micro-blower 14 or the gas supply control valve (not shown) used to control the air supply from a wall outlet for example.

[0046] Within the control means 7, the microprocessor 7-1 is configured to calculate the RI ratio in the following manner by controlling the different components of the fan 1 necessary for this calculation.

[0047] More precisely, we operate as follows: a) modification or fixing, typically by a doctor, of the respiratory frequency (Fr) so that the control means 7, in particular the microprocessor 7-1, control the micro-blower to deliver the gas at a frequency of between 4 and 10 breaths per minute; however, according to another embodiment, the frequency can be modified automatically by the ventilator, and possibly validated by a doctor by pressing a validation key for example, b) switching to or fixing, by controlling the expiratory valve 12 by the control means 7, a so-called "high" PEP or high PEP between 10 and 30 cmH2O, preferably between 10 and 25 cmH2O, for example 15 cmH2O, c) measurement by the pressure sensor 5 of a high PEP_measured, d) reduction of the PEP of the expiratory valve 12 by the control means 7, down to a so-called "low" PEP or low PEP, such as: PEP basse = PEP haute − A Where: high PEP is between 10 and 30 cmH2O, for example 15 cmH2O, A is a value between 5 and 15 cmH2O, typically equal to approximately 10 cmH2O From there, we have for example low PEP = 5 cmH2O (for A = 10 cmH2O and high PEP = 15 cmH2O), e) determination of the measured gas volume ΔEELV (End Expiratory Lung Volume or end-expiratory lung volume) which is measured and generated by the transition between high PEP and low PEP, the gas volume being determined by the control means 7 by integration of the flow rate measured by the flow rate measuring means 6 during said transition. f) measurement of the tidal gas volume (Vte) at low PEEP, which is the tidal volume expired by the patient (Vte = tidal volume expired), determined by the control means 7 by integration of the expired flow measured by the flow measuring means 6 during the expiration time at low PEEP. g) setting an inspiratory pause time (t pi ) of up to 0.6 sec, typically between 0.1 and 0.4 sec approximately, h) measurement by the pressure sensor 5 of the plateau pressure P flat obtained at low PEP, i.e. the pressure at the end of inspiration at the instant when the flow rate measured by the flow rate measuring means 6 is zero, i) measurement by the pressure sensor 5 of a low PEP_measured, j) calculation of the compliance Crs of the respiratory system at low PEP, where: . Crs = V te / P plat − PEP basse _ mesurée k) estimation of the estimated ΔEELV volume estimated by a reduction of the PEEP from high PEEP to low PEEP (eg between 15 and 5 cmH2O) predicted by the compliance of the system at low PEEP, namely Δ estimated = Crs * (high PEEP_measured - low PEEP_measured), l) calculation of the recruited gas volume Vrec where: ΔVrec = Δ EELV mesuré − Δ EELV estimé − Vte m) calculation of the compliance of the recruited lungs Crec such that: Crec = ΔVrec / PEP haute _ mesurée − PEP basse _ mesurée n) calculation of the recruitment / inflation ratio or RI ratio, such as: R − I ratio = Crec / Crs

[0048] Once the RI ratio has been calculated by the control means 7, the latter control its display on the display screen 8, as well as preferably information on the recruitability status of the patient, for example on one or more monitoring blocks 8-1, 8-2 displayed on the display screen 8 of the ventilator 1.

[0049] So, Fig. 2 schematizes a display on the display screen 8, of a first monitoring block 8-1, that is to say a display window, making it possible to visualize the RI ratio calculated by the control means 7 and the recruitability status of the patient P.

[0050] The recruitability status of patient P is determined by the control means 7 in the following manner from the RI-ratio: if the RI ratio is less than or equal to a threshold value, for example 0.5, the control means 7 determine that the patient is a non-recruiter, conversely, if the RI ratio is greater than the threshold value, the control means 7 determine that the patient is a recruiter.

[0051] The threshold value is set by default on the ventilator 1, can be adjusted by the user, for example a doctor at the HMI level, and stored in a memory 14 of the ventilator 1 and / or in a microprocessor 7-1 of the control means 7. Advantageously, the threshold value is between 0 and 2, in particular depending on the doctor's decision, typically the threshold value is equal to 0.5, but of course, depending on the case, it could be greater than 0.5, for example equal to 0.6, 0.7, 0.8, 0.9 or 1, or even more.

[0052] As already stated, the control means 7 can then command a display, i.e. visualization, on the display screen 8, of information relating to the recruitability status of the patient having been thus determined, typically a text signaling this recruitability status of the patient, for example "recruiting patient" or "non-recruiting patient", as illustrated in Fig. 2 , and / or a graphic representation with a color code dedicated to each state, such as a patient face colored green for a recruiting patient and red for a non-recruiting patient, or any equivalent information allowing the healthcare staff to immediately and / or easily distinguish a recruiting patient from a non-recruiting patient.

[0053] Advantageously, the control means 7 can also be configured to determine and control a display on the display screen 8 of a recommendation for action to be taken by the healthcare staff depending on the recruitability status having been determined for a given patient, for example in a second monitoring block 8-1, as shown diagrammatically in Fig. 2 , especially : for a non-recruiting patient, propose or recommend maintaining or reducing the set PEEP value, or for a recruiting patient, propose or recommend an increase in the PEEP value and / or a maximum PEEP threshold value not to be exceeded.

[0054] As illustrated in Fig. 2 , the recommendation for action to be taken by the healthcare personnel which is displayed on the display screen 8 may be, for example, textual information of the type "maintain PEEP", "increase PEEP" or "decrease PEEP", or any similar or equivalent indication.

[0055] It can be accompanied by a graphical representation display allowing the nursing staff to better visualize the recommended action to be taken, such as an arrow pointing upwards to indicate an increase in positive pressure or, conversely, downwards to indicate a decrease in positive pressure, or an "=" sign for maintaining or preserving the current positive pressure.

[0056] In addition, the control means 7 can also be configured to control a display on the display screen 8: of a graphical representation and / or the value of the RI ratio having been determined in the form of a unitless value between 0 and 5, and / or of one (or more) real-time curve(s) (8-3) of pressure or volume type obtained from several successive measurements of gas pressure and / or gas flow rate processed by the microprocessor of the control means 7, as illustrated in Fig. 2 .

[0057] In addition, other information useful to the nursing staff may be displayed (8-4) on the display screen 8, such as the tidal volume (Vte), the respiratory rate (Rf), the expiratory pressure or PEEP, or other ventilatory parameters, as visible in Fig. 2 .

[0058] A ventilator 1 according to the invention is of great help to the healthcare staff because it provides them with a reliable assessment of the recruitability of a patient suffering from ARDS, thanks to the calculation and display of the recruitment / inflation ratio or RI ratio, thus allowing them to personalize the ventilation of the patient in question, in particular the PEEP setting to be applied to them, to ensure effective, non-deleterious ventilation, whether the patient is a recruiter or a non-recruiter.

[0059] Generally speaking, a medical ventilator 1 of the invention can be used to ventilate a person, i.e. a patient, suffering from respiratory distress, i.e. ARDS, by providing the healthcare personnel with an indication(s) of whether or not the lungs of the patient in question are recruitable and preferably also a recommendation for action to be taken regarding the PEP to be implemented.

[0060] Such information helps the healthcare personnel, i.e. physician or similar, to adapt the PEEP setting, preferably in association with other available clinical data or parameters, such as real-time pressure, volume and / or flow curves or others.

[0061] In addition, such a ventilator has the advantage of being able to give an indication of the ability of a patient's lungs to open further to participate in gas exchange when implementing PEEP on expiration, directly at the patient's bedside and without the need for additional equipment.

Claims

1. Medical ventilator (1) comprising: - a gas circuit (2) comprising an inspiratory branch (2-1) for conveying a respiratory gas and an expiratory branch (2-2) for evacuating the exhaled gas to the atmosphere, - flow rate measurement means (6) configured to determine at least one gaseous flow rate in the gas circuit (2), - pressure measurement means (5) configured to determine at least one gaseous pressure in the gas circuit (2), - a PEEP valve (12) arranged on the expiratory branch (2-2), - a graphical display (8), and - operating means (7) with microprocessor (7-1) cooperating with the flow rate measurement means (6), the pressure measurement means (5), the PEEP valve (12) and the graphical display (8), characterized in that: - the operating means (7) are configured to: a) determine an R-I ratio from the flow rate and pressure measurements performed by the flow rate measurement means (6) and the pressure measurement means (5), where the R-I ratio is such that: R − I ratio = Crec / Crs where: - Crec is the compliance of the recruited lungs of the patient and - Crs is the compliance of the respiratory system, b) order a display, on the graphical display (8), of the calculated R-I ratio, - and the graphical display (8) is configured to display (8-1) the R-I ratio.

2. Ventilator according to Claim 1, characterized in that the operating means (7) are configured to determine the compliance (Crs) of the respiratory system (Crs) such that: Crs = Vte / (Pplat - PEEP measured low), where: - Pplat is the plateau pressure at PEEPlow, with: PEEPlow = PEEPhigh - A and PEEPhigh between 10 and 30 cmH2O and A between 5 and 15 cmH2O, - PEEP measured low is a low PEEP value measured by the pressure sensor (5), and - Vte is the tidal volume exhaled by the patient.

3. Ventilator according to Claim 2, characterized in that the operating means (7) are configured to determine the compliance (Crec) of the recruited lungs of the patient such that: Crec = Δvrec / PEEP measured high − PEEP measured low where: ΔVrec is the gas volume recruited with: ΔVrec = Δ EELV measured − Δ EELV estimated − Vte where: - ΔEELVmeasured is the gas volume ΔEELVmeasured measured and generated by the transition between PEEPhigh and PEEPlow, and - ΔEELVestimated = Crs. (PEEP measured high - PEEP measured low).

4. Ventilator according to any one of the preceding claims, characterized in that the operating means (7) are further configured to determine a state of recruitability of the patient by comparing the RI ratio, determined for the patient in question, against a given recruitability threshold value and by determining that: - the patient is a non-recruiter when the R-I ratio is less than or equal to the recruitability threshold value, or - the patient is a recruiter when the R-I ratio is greater than the recruitability threshold value.

5. Ventilator according to Claim 4, characterized in that the recruitability threshold value is between 0 and 2, preferably equal to 0.5.

6. Ventilator according to Claim 1, characterized in that: - the operating means (7) are further configured to order a display, on the graphical display (8), of the state of recruitability of the patient (8-1), and - the graphical display (8) is configured to display (8-1) the state of recruitability of the patient.

7. Ventilator according to Claim 1, characterized in that the operating means (7) are configured to determine the calculated R-I ratio, after activation, by the user, of a selection means (13) displayed on the graphical display (8).

8. Ventilator according to Claim 7, characterized in that the activation of the selection means (13) is effected by pressing with a finger on a virtual key or a numeric keypad.

9. Ventilator according to Claim 1, characterized in that: - the operating means (7) are further configured to determine a recommendation for action to be taken as a function of the state of recruitability that has been determined and to further order a display (8-2), on the graphical display (8), of the recommendation for action to be taken, and - the graphical display (8) is configured to display the recommendation for action to be taken (8-2).

10. Ventilator according to Claim 9, characterized in that it comprises storage means (14) configured to store recommendations for action to be taken, including increasing the PEEP, decreasing the PEEP or maintaining the PEEP.

11. Ventilator according to Claim 1, characterized in that it further comprises a micro-blower (14) as a gas source (4) supplying the inspiratory branch (2-1) of the gas circuit (2) with air or an air / oxygen mixture.

12. Ventilator according to Claim 1, characterized in that the operating means comprise at least one electronic card comprising at least one microprocessor.

13. Ventilator according to Claims 11 and 12, characterized in that the operating means are configured to operate the micro-blower (14).

14. Ventilator according to Claim 1, characterized in that the operating means (7) are further configured to order a display (8-4), on the graphical display (8), of at least one additional item of information selected from the tidal volume (Vte), the respiratory rate (Fr) and the PEEP.

15. Ventilator according to Claim 1, characterized in that the display screen (8) is of the type with a colour display.