Respirator and method for controlling a respirator

Abstract

The present invention describes a method apparatus (1) for providing ventilation assistance to a patient, comprising a set of tubes (30, 40, 50, 60, 70) for a gas flow (fl) into and out of the patient, a demand flow valve (81, 81 '), a flow sensor (86) and a pressure sensor (87, 88) for measuring airway pressure. The invention relates to a device (1) for controlling an inspiratory flow circuit and an expiratory flow circuit, comprising a demand flow valve (81, 81 ') located at a Y-shaped member (8Y) connecting a tube (30) for the inspiratory flow circuit and a tube (40) for the expiratory flow circuit to a patient. The invention also describes a demand flow valve (81, 81') that can be used in such a device (1) and a method for controlling such a device (1).

Description

Technical Field

[0001] The present invention relates to a device for providing ventilator assistance to a patient, the device comprising a group of tubes for gas flow in and out of the patient, a flow sensor and a pressure sensor for measuring airway pressure. Such a device is generally and may also be referred to as a "ventilator device" or a "mechanical ventilator" or simply a "ventilator" hereinafter. Therefore, these terms can be used interchangeably. In addition, the present invention relates to a demand flow valve that can be used for such a ventilator, and to a method for controlling such a ventilator. In particular, the present invention is used to provide ventilation assistance to spontaneously breathing intensive care patients, especially those with respiratory insufficiency (respiratory insufficiency, generally and hereinafter also referred to as "RI") or acute respiratory distress syndrome (acute respiratory distress syndrome, generally and hereinafter also referred to as "ARDS"), who are at risk of baro-and volutrauma, additional work of breathing, and patient-ventilator asynchrony. Background Art

[0002] For clarity, when "airway pressure" is referred to in the context of mechanical ventilation and in the context of the present invention, it is typically measured external to the patient, within the ventilator circuit, at the proximal end of the "patient interface" that connects the ventilator to the patient (e.g., this may be an endotracheal tube, also commonly and hereinafter referred to as an "ETT", a tracheostomy tube, also commonly and hereinafter referred to as a "TT", a mask, or a breathing helmet). This pressure is also referred to as the "airway opening pressure" because it is measured near the point where the patient's airway opens to the environment (note that the proximal end of the patient interface is also the patient's airway that opens to the ventilator). In contrast, when referring to the biological airways of the patient's lungs, they will be referred to as the "patient's airway".

[0003] Patients in critical care who require ventilator support are usually intubated, sedated, paralyzed if necessary, and ventilated using pressure- or volume-controlled ventilation. If patients suffer from RI (e.g. due to pneumonia) or ARDS (e.g. due to sepsis), their lungs usually become stiff during the course of their illness, for example as a result of damage to the pulmonary surfactant membrane and the resulting increase in air-liquid interfacial tension. Inflating the lungs with typical tidal volumes (e.g., 500-800 ml) requires excessive inflation pressures. In addition, the lungs of patients with RI and ARDS are usually ventilated unevenly, with some parts of the lungs being underventilated and other parts of the lungs being over-expanded. Local over-expansion of the lungs combined with the high pressures delivered by the ventilator can lead to barotrauma and volutrauma, resulting in further lung damage and worsening of the disease. In addition, as intrathoracic pressure increases, pulmonary vascular resistance increases and venous return to the heart decreases, leading to cardiac pressure and reduced perfusion of other organs (e.g., brain and kidneys).

[0004] To reduce the risk of barotrauma and volutrauma, critical care physicians limit maximum airway pressure during inspiration to less than 30-35 mbar and tidal volume to approximately 6 ml / kg body weight. This single protective measure, when introduced into clinical practice in the late 1980s / early 1990s, resulted in a dramatic reduction in mortality among critical care patients, from approximately 40%-60% in the 1980s to 20%-40% in the 1990s. This remarkable success raised hopes that mortality in patients with RI and ARDS could be further reduced by more aggressive reductions in airway pressure and tidal volume. However, this has proven difficult because the lungs of ARDS patients require a positive end-expiratory pressure (positive end-expiratory pressure; often and hereinafter also referred to as "PEEP") of typically 10 mbar to prevent collapse, and as inspiratory pressure or tidal volume is further reduced, minute ventilation becomes too small for adequate gas exchange. Therefore, it is recommended that patients with RI and ARDS breathe spontaneously and then have the ventilator augment each breath with some form of pressor support that is as low as possible but high enough to meet the necessary needs.

[0005] Existing critical care ventilators offer ventilation modes designed to increase airway pressure during the patient's inspiratory effort. The strategy is to provide only as much pressure support as required to maintain adequate gas exchange without causing patient fatigue. Such patient-triggered modes of inspiratory support have been shown to have clinical advantages in ventilated patients, such as during weaning from mechanical ventilation, but to date these pressure support modes have been largely ineffective in the setting of RI and ARDS patients.

[0006] The reasons for this situation can be attributed to the following:

[0007] First, patients with ARI and ARDS often exhibit rapid shallow breathing patterns. This makes it difficult for the ventilator to discern the patient's inspiratory and expiratory efforts, especially if the pressure support is greater than the inspiratory pressure generated by the patient, so that the patient's intrinsic breathing pattern is masked by the ventilator's breathing pattern.

[0008] Second, patients are usually intubated using an endotracheal tube (usually and hereinafter also referred to as "ETT"). The large and highly nonlinear gas flow resistance of the ETT (due to turbulent conditions) consumes most of the pressure support, so these pressure supports never reach the patient (Guttmann, Eberhard et al., 1993; all citations refer to the reference list at the end of the specification, where the citations are characterized in the usual way by indicating the first two authors and the year, and if the same author has published several articles in the same year, add the label a or b if necessary). In addition, the ETT resistance hinders expiration and causes the accumulation of endogenous PEEP in the patient's lungs (Guttmann, Eberhard et al., 1995). However, the ventilator only measures the airway pressure outside the ETT (and, if applicable, the bacterial filter / humidifier that further increases the air flow resistance). This further obscures the patient's inspiratory and expiratory efforts.

[0009] The consequences of ETT (and bacterial filter / humidifier) ​​resistance combined with inadequate means of detecting the patient's inspiratory and expiratory efforts are severe:

[0010] Although the ventilator appears to be supporting the patient's spontaneous breathing pattern well when judged based on the time course of airway pressures, the patient's intratracheal and intraalveolar pressures are below PEEP during most of inspiration and well above PEEP during expiration. Therefore, the patient must generate additional work of breathing and has great difficulty in exhaling (Fabry, Haberthur et al., 1997).

[0011] More seriously, the ventilator no longer recognizes the patient's inspiratory and expiratory efforts. This can cause the patient's breathing pattern and the ventilator's breathing pattern to become out of sync, especially for patients with rapid, shallow breaths (Fabry, Guttmann et al., 1995). Patient-ventilator asynchrony means that about half of the time, the patient receives pressure support during their expiratory phase, which actually increases the pressure load on the lungs rather than reducing it as originally intended. In addition, about half of the time, during the patient's inspiratory phase, the pressure support is reduced to the PEEP level, which, together with the large ETT resistance, not only does the patient's breathing effort not get supported, but also causes a large amount of additional breathing work.

[0012] In principle, the ventilator mode Automatic Tube Compensation (Automatic Tube Compensation, often and hereinafter also referred to as "ATC") can prevent both problems of additional work of breathing and patient-ventilator asynchrony (Fabry, Guttmann et al., 1994a, b; Fabry, Haberthur et al., 1997). Instead of controlling the airway pressure to a constant value (as in the ventilator mode continuous positive airway pressure (CPAP)), ATC controls the tracheal pressure.

[0013] This is achieved by continuously calculating the tracheal pressure (based on the difference between the airway pressure and the pressure drop across the ETT tube (which can be calculated from the product of the measured gas flow and the known ETT resistance)) and controlling the gas flow to keep the tracheal pressure constant. Therefore, during inspiration or exhalation, the airway pressure is no longer set to a determined value, but varies automatically to a value greater than PEEP during inspiration and to a value less than PEEP during exhalation. The amplitude of this pressure fluctuation depends on the patient's respiratory effort. ATC almost completely eliminates any additional work of breathing, even for patients with high ventilator demands (Fabry, Haberthur et al., 1997), and completely prevents patient-ventilator asynchrony (Fabry, Guttmann et al., 1994b).

[0014] To support ARDS patients using this mode, ATC can be combined with flow-proportional assist and / or volume-proportional assist ventilation (proportional assist ventilation, often and hereinafter also referred to as "PAV"). Essentially, instead of tracheal pressure being continuously calculated and adjusted, alveolar pressure is continuously calculated and adjusted (which corresponds to flow-proportional assist, which also overcomes airway resistance), or pleural pressure is continuously calculated and adjusted (which corresponds to volume-proportional assist, which also overcomes lung compliance). Even diaphragmatic pressure can be calculated and adjusted (which corresponds to flow-proportional assist and volume-proportional assist to overcome ETT and airway resistance and lung and chest compliance). In other words, ATC with flow assist and volume assist works similarly to an electric bicycle, where the cyclist can choose the percentage of his or her leg muscle effort supported by the electric motor.

[0015] ATC with PAV was first implemented in experimental ventilators (Fabry, Guttmann et al., 1994a), and after demonstrating that RI and ARDS patients could be successfully ventilated with this mode (Fabry, Haberthur et al., 1997), it was also implemented in commercial ventilators. Today, ATC with PAV is the standard mode for intensive care ventilators. However, this mode is rarely used to support RI and ARDS patients. The reasons for this are unclear, but are likely a combination of several factors:

[0016] First, the rapid shallow breathing pattern (tidal volume less than 300 ml, frequency about 50-60 / min) of patients with RI and ARDS is not obvious under standard pressure support (due to asynchrony) and only becomes obvious when the patient is ventilated with ATC (Fabry, Guttmann et al., 1994b; Fabry, Guttmann et al., 1995). If clinicians are not familiar with this extreme breathing pattern, they may interpret it as a sign of respiratory failure and switch to a mode that masks this pattern (the patient will still breathe rapidly and shallowly, but the physician will no longer observe it).

[0017] Second, commercial ventilators typically sense airway pressure and gas flow within the ventilator, which is about 2 meters away from the patient. Therefore, the speed of sound and the low-pass characteristics of the elastic tube limit the reaction time of the ventilator. There is also a delay in the demand flow, which is generated in the ventilator 2 meters away from the patient and does not reach the patient immediately.

[0018] Third, the expiratory valve of commercial ventilators is usually open to atmosphere. Therefore, the airway pressure is always positive. If the pressure difference across the expiratory valve, plus the pressure difference across the expiratory tubing, plus the pressure difference across the bacterial filter / humidifier, and plus the pressure difference across the endotracheal tube exceeds the PEEP level, the tube resistance cannot be fully compensated, so ATC is no longer effective and the patient's expiratory flow is reduced.

[0019] Overall, current solutions fail to provide ARDS patients with a ventilator-assisted mode that would allow them to breathe on their own without the risk of asynchrony, additional work of breathing, and worsening of the underlying disease. As a result, ARDS patients are often ventilated in a controlled mode and are unable to breathe on their own.

[0020] It is therefore an object of the present invention to provide an improved device and a corresponding method, by which the above-mentioned problems may be at least partially overcome or reduced. Summary of the invention

[0021] This object is achieved by a device according to claim 1 , a demand flow valve according to claim 12 and a method according to claim 13 .

[0022] The device for providing ventilation assistance to a patient according to the present invention comprises at least:

[0023] - sets of tubes for the flow of gases to and from the patient,

[0024] - Demand flow valve,

[0025] - a flow sensor for measuring the flow of gas into and out of the patient's airway, for example at the airway opening, and

[0026] -Pressure sensor for measuring airway pressure.

[0027] According to the present invention, a demand flow valve is located in the air flow circuit at a Y-piece that connects the tube for inspiratory gas flow to the patient and connects the tube for expiratory gas flow from the patient to the patient interface.

[0028] In general, a demand flow valve is a pressure reducing device that regulates the outlet pressure to a set point, regardless of the inlet pressure (which must be greater than the set point) and the gas flow rate. To achieve this function, the valve resistance must be variable. A two-state (on-off) switching valve alone cannot function as a demand flow valve.

[0029] With such a demand flow valve, by using appropriate means for controlling the demand flow valve, in particular based on the values ​​measured by the flow sensor and the pressure sensor, the pressure generated on the patient side of the set of tubes can be directly regulated or controlled, thereby regulating or controlling the gas flow to and from the patient (hereinafter, if not mentioned otherwise, "control" and "regulation" are synonymous). In contrast, with a switching valve, it is only possible to switch between the tube for the inspiratory gas flow and the tube for the expiratory gas flow circuit. In particular, as explained later, the demand flow valve can be used to control at least one of the airway pressure, tracheal pressure, alveolar pressure, pleural pressure and muscle pressure, preferably depending on the mode of ventilator support.

[0030] As explained later, the Y-piece should be arranged as close to the patient as possible. According to the present invention, when the demand flow valve is located at the Y-piece, it is also located in the position of the air flow circuit as close to the patient as possible.

[0031] The demand flow valve according to the invention is implemented as a Y-piece located in an air flow circuit or a gas flow tube system of a ventilator device. Some implementation possibilities will be explained later.

[0032] The ventilator apparatus according to the present invention is preferably an intensive care apparatus, but may also be used in other settings to provide ventilator assistance to a patient.

[0033] According to the present invention, a method for controlling a ventilator, in particular an intensive care ventilator, comprises at least the following steps:

[0034] - measuring the flow of gas into and out of the patient's airway with a flow sensor, for example at the airway opening,

[0035] - measuring the airway pressure in the airway entering and exiting the patient with a pressure sensor, e.g. at the airway opening,

[0036] - Controlling a demand flow valve based on gas flow and airway pressure, wherein the demand flow valve is located at a Y-piece (close to the patient) that connects the tubing for the inspiratory airflow circuit and the tubing for the expiratory airflow circuit to the patient.

[0037] The ability to directly control or regulate the pressure from inspiratory flow to expiratory flow and back again, in a demand flow valve as close to the patient as possible, at least reduces the delay time between the control point at which the pressure is changed according to the control signal and the point at which the current pressure change actually becomes relevant to the patient, i.e. at the outlet of the patient interface or even deeper in the patient's airway (e.g. in the trachea or alveoli). This allows for more precise demand flow control and airway pressure control and, in principle, as will be explained later, also allows for improved performance of the ventilation modes mentioned above, such as ATC and optionally PAV (if used), in terms of, for example, lower additional work of breathing, better synchronization with the patient's respiratory effort, lower intrinsic PEEP and lower peak alveolar pressure levels.

[0038] In addition, as disclosed in the following description, particularly advantageous embodiments and further embodiments of the invention are given by the dependent claims. Features of different claim categories, description parts of different claim categories and individual features or feature groups of different embodiments can be appropriately combined to give further embodiments.

[0039] As mentioned above, the Y-piece in the device or system for supplying breathing air is an element defining a branch point at which the gas flowing to and from the patient's lungs and the patient's airway is divided into an inspiratory gas flow branch and an expiratory gas flow branch. The gas volume between the center of the Y-piece and the proximal end of the patient interface defines the functional dead space of the gas flow circuit. At the end of each exhalation, the dead space is filled with hypoxic alveolar gas and then re-inhaled at the beginning of the next inhalation. Therefore, preferably, the dead space is kept as small as possible. Therefore, the Y-piece is preferably positioned "close proximity" to the patient, and the distance from the patient-side outlet of the demand flow valve to the opening of the patient interface (the opening is the connection point with the interface) should be correspondingly small. The range of this distance (which can also be used to define "close proximity" or "close to" the patient) can be from 0 cm to the maximum distance of the maximum allowable dead space specified by the attending intensive care physician. For example, the maximum allowable dead space for an adult patient weighing 66 kg is 100 ml, then the maximum distance is about 60 cm, depending on the diameter of the elastic tube connecting the Y-piece and the patient interface, but the more preferred distance is a maximum of 30 cm or even lower.

[0040] "Dead space" as used herein is the volume of gas in the valve and connecting tubes that contains previously exhaled air and is re-inhaled during the next breath, potentially affecting the ventilation efficiency of the patient. In practice a compromise must be found between reaction time and dead space, both of which decrease with decreasing distance, and comfort of patients and staff, on the one hand, which increases with increasing distance.

[0041] Preferably, the demand flow valve is implemented and positioned at the Y-piece such that the dead space in the demand flow valve and in the tubing from the demand flow valve to the connection point to the patient interface is less than 1.5 cm per kg of patient weight. 3 value, or if a larger or smaller dead space is clinically required, below the maximum allowable dead space defined by the attending physician.

[0042] Preferably, for adult patients, the demand flow valve at the Y-piece is realized and positioned so that the maximum dead space in the demand flow valve and in the tubing system from the demand flow valve to the connection point to the patient interface is approximately 100 cm 3 , preferably 60cm 3 , more preferably 55cm 3 , and more preferably 30 cm 3 .

[0043] Preferably, the two tubes connected to the Y-piece for the inspiratory flow circuit and the expiratory flow circuit are connected to a pressure source that provides positive pressure for the inspiratory circuit and negative pressure for the expiratory circuit.

[0044] The pressure source may also be part of the ventilator device and may be realized by any arrangement of pressure sources for each tube or pressure side, such as a blower, preferably a brushless radial blower.

[0045] In a preferred embodiment, the pressure source may be a constant pressure source providing a near constant positive pressure, preferably about +40 mbar, for the inspiratory circuit and a near constant negative pressure, preferably -20 mbar, for the expiratory circuit, whereby other pressure levels may be selected if desired, including atmospheric pressure, particularly for the expiratory circuit. In another preferred embodiment, the pressure source or at least one of the pressure sources may also be variable, as long as the frequency and amplitude of the pressure changes do not overwhelm the ability of the demand flow valve to control the flow and pressure on the patient side of the valve to the desired values.

[0046] In particular, the pressure sources can also preferably be controlled in such a way (coordinated with the control of the demand flow valve) that they are raised and lowered as required, for example, the corresponding pressure source will only generate the corresponding pressure when a certain pressure is absolutely required, otherwise the pressure source only generates a smaller pressure or is even turned off. This has the advantage of making the device quieter. For this purpose, a suitable pressure source (such as a blower) that can be switched quickly accordingly can be used. It should be noted that, as is usually the case in the field of ventilation technology, all pressure values ​​given in this document are pressure differences from the current ambient pressure (nominally the current atmospheric pressure on site), so common differential pressure sensors are used (unless otherwise specified).

[0047] In principle, the demand flow valve at the Y-piece can be realized in various ways. For example, controllable closing elements or shutters (e.g. baffles) can be arranged at or in the tubes (or tube connections) for the inspiratory and expiratory airflow circuits directly adjacent to the Y-piece (and optionally also at or in the tubes (or tube connections) connected to the patient).

[0048] Preferably, the demand flow valve is implemented so that the pressure and flow on the inspiratory side can be adjusted, while the expiratory side remains closed and is not affected by the pressure on the inspiratory side, and vice versa. On the one hand, during the inspiratory phase, the expiratory flow circuit can be kept closed by the demand flow valve, while at the same time the flow and pressure of the inspiratory flow circuit can be adjusted by the demand flow valve. On the other hand, during the expiratory phase, the inspiratory flow circuit can be kept closed by the demand flow valve, while at the same time the flow and pressure of the expiratory flow circuit can be adjusted by the demand flow valve. This design can save a lot of breathing gas and reduce O 2 consumption.

[0049] Preferably, the Y-piece accommodates the demand flow valve, or, in other words, the demand flow valve may be integrated in the Y-piece, or, in other words, the demand flow valve serves as a Y-piece. In this way, the valve may be kept as compact as possible and regulation or control of the pressure and gas flow to and from the patient may be achieved as directly as possible at the point where the inspiratory and expiratory gas flow circuits meet.

[0050] However, preferably, the demand flow valve can be a preferably rotary three-way valve or better a rotatable three-way valve (e.g. a valve with a rotatable closing element (also referred to as a gate) inside the valve housing, as described in detail later), which connects the outlet (towards the patient) to the positive pressure side or the negative pressure side. Or, in other words, the three-way valve connects the outlet towards the patient interface and the inspiratory side (usually under positive pressure) with the expiratory side (usually connected to negative pressure or atmosphere). More preferably, the three-way valve can be a rotary three-way valve.

[0051] The use of a three-way valve, and in particular a rotating or rotatable three-way valve, allows a particularly simple and compact design and a particularly easy and precise control of the pressure and gas flow.

[0052] Furthermore, such a three-way valve also allows for an easy implementation of a demand flow valve, such that the pressure and flow on the inspiratory side can be adjusted while the expiratory side remains closed, and vice versa, as already mentioned above.

[0053] The pressure inlet (connection to the gas flow of inspiration gas, which is usually positive pressure, and connection to the gas flow of exhalation gas, which is preferably negative pressure) can be connected to the valve housing preferably in a straight or curved arrangement; the outlet can be in the plane of the inlet, or preferably perpendicular to the inlet, or inclined in other ways. Particularly preferred embodiments of these two versions will be described later.

[0054] The curved pressure inlet combined with the vertical outlet may allow for a more compact design and may further reduce the internal volume (and dead space) of the valve.

[0055] Preferably, a device to prevent flow turbulence, such as a grid structure, a laminar flow tube array, etc., may be positioned in the outlet of the demand flow valve.

[0056] Preferably, a flow sensor and a pressure sensor for measuring the airway pressure (or airway opening pressure) which can be used as a basis for controlling the demand flow valve are also arranged in close proximity to the patient as defined above. This may help to reduce the delay of the feedback control signal for the demand flow valve. More preferably, the flow sensor and the pressure sensor are placed on the patient side of the demand flow valve (the side leading to the patient interface). If the airway pressure is detected close to the patient from downstream (proximal) of the demand flow valve, this automatically ensures that all upstream (distal) resistance elements are fully compensated, such as the resistance of the tube and the demand flow valve.

[0057] In a particularly preferred configuration, the Y-piece (on the patient side) that preferably houses the demand flow valve is connected to a respiratory flow meter or other device for flow sensing. The respiratory flow meter or other device for flow sensing is in turn optionally connected to a bacterial filter and / or humidifier, which is preferably followed by a short elastic tube that is connected to a swivel connector and further connected to a patient interface (e.g., an ETT, TT, mask, or breathing helmet).

[0058] However, instead of using a combination of a bacterial filter and / or a humidifier, in particular for chronically ventilated patients, an active humidifier can also be provided in the inspiratory circuit (inspiratory tube) leading to the Y-piece, which can better humidify the inspired air.

[0059] As already mentioned above, in order to control or regulate the pressure or gas flow supplied to and from the patient, the ventilator may comprise means for controlling or regulating the demand flow valve, respectively a controller (e.g. a control unit or system). Thus, the controller is connected to the demand flow valve and preferably also to (directly or indirectly) a flow sensor and a pressure sensor, since the control or regulation should be based on the values ​​measured by the flow sensor and the pressure sensor (directly or indirectly as explained below).

[0060] The controller preferably comprises a PID controller (Proportional-Integral-Derivative controller), but other control algorithms may also be used.

[0061] Advantageously, the control or regulation of the pressure provided on the patient side and the control or regulation of the gas flow to and from the patient may depend on a predefined (or preset) mode supported by the ventilator. For example, preferably, the controller or control system of the ventilator may operate in a predefined mode, which may be configured by the user via a user interface or selected by the user from a plurality of preset modes, which may be stored in the control system.

[0062] Preferably, the present invention can be used to control (adjust accordingly) at least one of airway pressure, tracheal pressure, alveolar pressure, pleural pressure and muscle pressure, or a portion of the pressures thereof, by controlling a demand flow valve. In particular, in a predefined mode of ventilator support, it can be specified that the control method is optimized with respect to which pressure (airway pressure, tracheal pressure, alveolar pressure, pleural pressure or muscle pressure).

[0063] For example, the target airway pressure can be set according to an established ventilation mode (such as patient-triggered inspiratory pressure support). However, the advantages of the proposed demand flow method and device are most evident in ventilation modes that require the demand flow valve to respond quickly and accurately to rapidly changing demands, particularly in ATC modes without or with proportional assist ventilation (ATC+PAV). The ATC+PAV mode compensates for the downstream resistance and elastic pressure difference between the demand flow valve and the patient's respiratory muscles, thereby reducing or avoiding excessive work of breathing, excessively negative positive transpulmonary pressure, intrinsic PEEP, or patient-ventilator asynchrony.

[0064] The actual tracheal pressure, alveolar pressure, pleural pressure or muscle pressure can preferably be continuously calculated based on the gas flow and the airway opening pressure. For example, the tracheal pressure can be calculated based on the difference between the airway pressure and the pressure drop across the ETT tube, which in turn can be calculated based on the product of the measured gas flow and the known ETT resistance.

[0065] When the ventilator is operated in ATC+PAV mode, the controller’s target pressure P target It can be calculated as follows:

[0066] P target =PEEP+f 0 ·ΔP(ETT)+f 1 ·ΔP(R aw )+f 2 ·ΔP(E rs ) (1)

[0067] where PEEP is positive end-expiratory pressure, ΔP(ETT) is the pressure drop across the endotracheal tube and any additional resistive elements (such as bacterial filters / humidifiers, swivel connectors, CO2 sensors, bronchoscopes, or catheters inserted into the tube); ΔP(R aw ) is the pressure drop caused by airway resistance; and ΔP(E rs ) is the pressure drop caused by the elasticity of the respiratory system. Factor f 0 、f 1 and f 2Adjusted by the attending intensive care physician or respiratory therapist to a value between 0 and 1, where a value of 1 results in complete (100%) compensation of the work of breathing caused by the corresponding resistance or elastic element and a value of 0 results in no (0%) compensation.

[0068] These pressure drops can be calculated based on the continuously measured gas flow V' (e.g. using a respiratory flowmeter) and the volume V as follows, where the volume V is the time integral of the gas flow (V = ∫V'dt, boundary condition V = 0 at the beginning of inspiration):

[0069] The pressure drop ΔP(ETT) during inspiration (V' is positive) can be calculated using the following equation:

[0070]

[0071] or alternatively

[0072]

[0073] And during exhalation (V' is negative)

[0074]

[0075] or alternatively

[0076]

[0077] In equations (2a, 2b, 3a, 3b), the coefficient k 1,in , k 2,in , k 1,ex , k 2,ex The nonlinear resistance of the endotracheal tube and the additional resistance element is described as described in (Guttmann, Eberhard et al., 1993). In addition to the power law fit (Eq. 2a, 3a) or the second order polynomial (Eq. 2b, 3b), other empirical fit equations are possible.

[0078] The patient's airway resistance R aw The pressure drop across the patient's airway caused by aw ) can be calculated according to the following equation:

[0079]

[0080] The elasticity E of the patient's respiratory system rs The pressure drop ΔP (E rs ) can be calculated according to the following equation:

[0081] ΔP(E rs ) = E rs·V (5)

[0082] In equation (1), the factor f 0 、f 1 and f 2 You can select between 0 (0% compensation) and 1 (100% compensation). 1 and f 2 Preferably, f is set to zero during exhalation. 0 Select an f of 1 during both inspiration and expiration. This ensures that tube resistance and other additional resistance elements do not cause additional work of breathing and intrinsic PEEP. In some cases, such as in patients with chronic obstructive pulmonary disease (COPD) with expiratory flow limitation, an f lower than 1 can be selected during expiration. 0 Value. aw and E rs The exact value of f is usually unknown. 1 and f 2 It can also be chosen to be less than 1 to avoid so-called run-away effects. Once the set tidal volume is reached, the f 1 and f 2 Setting it to a lower value can also prevent the runaway effect.

[0083] Based on these pressure drops, the tracheal pressure P trach , alveolar pressure P alv or muscle pressure P mus It can be calculated as follows:

[0084] P trach =P aw -ΔP(ETT)(6a)

[0085] P alv =P trach -ΔP(R aw )(6b)

[0086] P mus =P alv -ΔP(E rs )(6c)

[0087] If the actual tracheal pressure, alveolar pressure, pleural pressure and / or muscle pressure are known, the gas flow can be controlled using a demand flow valve to keep the tracheal pressure constant and / or to fully or partially compensate for the work of breathing required to overcome airway resistance, lung elasticity and chest wall elasticity. In this way, the present invention can help minimize the additional work of breathing for the patient caused by the resistance of various elements in the inspiratory and expiratory circuits (particularly the resistance of the ETT, humidifier, the resistance of the expiratory tubing and the expiratory valve) and the delay of the demand flow and feedback control signal (airway pressure gas flow).

[0088] In addition, the controller can also be implemented to control the positive pressure source and the negative pressure source, in particular to modify or adjust the pressure levels provided by the positive pressure source and the negative pressure source. For example, if the pressure source includes a brushless radial blower, the precise pressure can be easily adjusted or controlled by changing the motor speed.

[0089] In one embodiment, the demand flow valve is implemented so that in the neutral position of the demand flow valve, a small overlap allows airflow to pass between the positive pressure (inspiratory) side and the negative pressure (expiratory tube) side. This may help improve the accuracy of pressure control in low flow conditions (such as at the end of exhalation).

[0090] The "neutral position" of the demand flow valve is the middle position of the valve, meaning halfway between the inspiratory position, in which the demand flow valve connects the tubing for the inspiratory airflow circuit to the tubing leading to the patient, and the expiratory position, in which the demand flow valve connects the tubing for the expiratory airflow circuit to the tubing leading to the patient.

[0091] However, in another embodiment, the demand flow valve has no overlap in the neutral position, as this reduces the O 2 consumption and allows for occlusion manoeuvre when required.

[0092] Since both variants may be advantageous depending on the situation, the demand flow valve may also preferably be realized such that it can be switched both to a mode with overlap in the neutral position and to a mode without overlap in the neutral position.

[0093] The ventilator according to the present invention can no longer be considered as a single device, usually located 1.5m-2m away from the patient (as in existing intensive care ventilators), but can be divided into two main parts. Preferably, the ventilator comprises:

[0094] - A valve-sensor assembly (hereinafter also referred to as a "valve-sensor unit"), which is placed close to the patient at the location of the Y-piece and comprises a demand flow valve and a sensor. Thus, the demand flow valve of the valve-sensor unit can replace the Y-piece.

[0095] - A base station located remotely from the valve-sensor assembly and typically 1.5-2 m from the patient. The base station may comprise at least means for generating (and controlling, if necessary) positive and negative inlet pressures.

[0096] Preferably, in this embodiment, on the one hand, the remote base station

[0097] - The air / oxygen mixture can be supplied from the hospital's air pressure line and oxygen pressure line (or from compressed air and oxygen cylinders);

[0098] - positive and negative pressures can be generated for the inlet and outlet, for example with the help of radial blowers, venturi valves, pressure regulators, etc.,

[0099] - may include a power supply for all components of the device,

[0100] - may optionally include a computer or controller for various monitoring and control tasks and for providing a user interface (e.g. for selecting ventilation mode, device settings),

[0101] - May optionally accommodate a monitor for visual feedback and for displaying measured flow, pressure and volume curves and other respiratory parameters.

[0102] The latter two optional components (computer and monitor) may also be provided, for example, by a separate laptop, tablet, smartphone or other remote monitoring and control device.

[0103] On the other hand, the valve-sensor unit is preferably

[0104] -Can continuously measure airway pressure and gas flow

[0105] - may include an electric valve that controls airway pressure or gas flow to a desired value depending on the selected ventilation mode,

[0106] - A microcontroller may optionally be included for data acquisition, for controlling valves or for operating a ventilator.

[0107] Examples of preferred embodiments of the base station and the valve-sensor unit will be explained in more detail later on hereinafter with reference to the accompanying drawings.

[0108] In most cases where critical care patients require ventilator assistance, an ETT (endotracheal tube) is used as the patient interface from the ventilator to the patient's airway. However, while choosing an endotracheal tube with a larger diameter to reduce its resistance and improve air flow may seem attractive to intensive care physicians, this may lead to other serious complications. Immediate complications of a larger tube diameter include irritation of the delicate tracheal tissue, inflammation, trauma and pressure ulcers, subglottic stenosis, and vocal cord injury. Long-term consequences of large tube extubation after extubation may include impaired breathing, speaking, and swallowing, seriously affecting the patient's overall health and recovery.

[0109] As explained above, the present invention allows better use of methods such as ATC (with or without PAV), the purpose of which is to compensate for the resistance of various components in the gas flow circuit, in particular the resistance in the ETT. Therefore, in a preferred embodiment of the present invention, the set of tubes for the flow of gas to and from the patient comprises in the adult version at least one endotracheal tube or tracheostomy tube having a maximum inner diameter of 7 mm, preferably 6 mm, more preferably 5 mm, and if feasible, even smaller. In the version for children or infant patients, the set of tubes for the flow of gas to and from the patient comprises at least one endotracheal tube or tracheostomy tube having a maximum inner diameter of 5 mm, preferably 2 mm.

[0110] In some cases, it is desirable or necessary to insert additional tubular medical instruments, such as endoscopes, particularly bronchoscopes, through the ETT or TT. This also significantly increases the resistance in the ETT or TT. However, as explained above, the present invention provides an opportunity to better compensate for any resistance in the tube. Therefore, in a preferred embodiment of the present invention, the group of tubes for gas flow to and from the patient includes at least one ETT or TT, wherein instrument leads and / or tubes (such as bronchoscopes, endoscopes or other tubular instruments) are arranged within the ETT or TT to extend along at least a portion of the length of the ETT or TT.

[0111] In general, the present invention provides a fast and accurate demand flow method and demand flow valve (and a ventilator with such a demand flow valve) for controlling the airway pressure and gas flow of a mechanically ventilated patient. Particularly advantageous features and effects are summarized again as follows:

[0112] The first feature is that the demand flow valve is placed in close proximity to the patient; specifically, it can replace the traditional Y-piece that connects the two tubes for the inspiratory and expiratory airflow circuits to the patient. The benefit of this close proximity to the patient's airway is that the reaction time caused by the speed of sound, the elasticity of the tube (channel) and the pressure oscillations in the air column is reduced.

[0113] To further reduce the reaction time of the demand flow valve, the second feature is that the flow sensor and the pressure sensor can also be placed close to the patient, in particular between the demand flow valve and the ventilator end of the patient interface (such as ETT, TT, mask or helmet). This improves the performance and accuracy of demand flow control because the speed of sound, the elasticity of the measuring tube (channel) and the pressure oscillation in the air column in the tube (channel) no longer cause significant delays in flow delivery and pressure transmission.

[0114] Since the demand flow valve is now in close proximity to the patient, as a third feature, the feed (inlet) pressure to the valve can be lower (compared to the pressure of several atmospheres of typical oxygen and compressed air pressure lines in hospitals). This is advantageous for patient safety reasons. The pressure at the inlet does not need to be tightly controlled, as the demand flow valve can handle large pressure fluctuations. The pressure should preferably be adjusted to the lowest level sufficient to deliver the required airway pressure and gas flow. For most cases, a positive pressure of +40 mbar will be sufficient, but higher or lower positive pressure values ​​may be required depending on the patient's breathing pattern and respiratory mechanics. For example, for ETTs with an inner diameter of less than 5 mm, or during bronchoscopy when the endoscope is introduced into the endotracheal tube, the tube resistance generated may exceed a value of 100 mbar*s / l. In this case, it is recommended to use a supply pressure greater than +100 mbar.

[0115] The fourth feature is that a separate exhalation valve, also known as a PEEP (positive end expiratory pressure) valve, which is an important component of traditional ventilators, is no longer needed. This is because the demand flow valve can regulate airway pressure during both inspiration and exhalation. The benefit of controlling the exhalation pressure through the demand flow valve is that the resistance of the exhalation tube can be automatically compensated.

[0116] Optionally, as a fifth feature, the outlet of the demand flow valve is not open to atmospheric pressure (as is customary in conventional ventilators), but is connected to a negative pressure source. This allows the demand flow valve to compensate for the flow resistance of the ETT during exhalation, thereby helping to reduce or avoid intrinsic PEEP, also known as auto-PEEP. For most cases, a pressure of -20 mbar will be sufficient, but smaller or larger negative values ​​may be required depending on the patient's breathing pattern and the resistance of the ETT, as explained above in conjunction with the third feature. As with the positive pressure at the inlet, the negative pressure at the outlet does not need to be precisely controlled because the demand flow valve can effectively handle pressure fluctuations.

[0117] The sixth feature is that the ventilator equipped with the new demand flow valve is no longer a single device 1.5m-2m away from the patient, but is divided into two parts, namely the valve-sensor unit (demand flow valve and sensor unit) close to the patient and the remote base station, as explained above.

[0118] These features, and particularly the combination of these features, allow for more accurate and faster demand flow control. The demand flow valve and method, combined with an automatic tube compensation control algorithm, allow for almost complete compensation of tube resistance, regardless of tube diameter. This eliminates concerns that a small tube will cause excessive resistance and impair ventilation. Instead of the standard (inner) tube diameter of 8 mm for men and the standard (inner) tube diameter of 7 mm for women, tube diameters as low as 4.5 mm are feasible (for inlet and outlet pressures of approximately 100 mbar; at greater inlet and outlet pressure levels, even smaller tube diameter resistances can be compensated). By analogy, a similar relative reduction in tube diameter is possible when the system is used for infants and children. Smaller tube diameters help to significantly reduce tracheal tissue damage, subglottic stenosis, and vocal cord damage, thereby also reducing post-extubation complications such as impaired breathing, speaking, and swallowing.

[0119] Besides compensating for tube resistance, the proposed control method and device for demand flow can also be used to compensate for additional resistance elements, such as humidifiers and bacterial filters, or bronchoscopes, catheters or measuring probes that have been inserted through the endotracheal tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0120] Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. However, it should be understood that the accompanying drawings are for illustrative purposes only and are not intended to be limiting of the present invention. In the drawings, like numbers always refer to like objects. Objects in the drawings are not necessarily drawn to scale.

[0121] FIG1 is a schematic diagram of various components of an existing ventilator and their relative arrangement;

[0122] Figure 2 is a schematic diagram of the components of a ventilator according to a first embodiment of the present invention and their relative arrangement;

[0123] Figure 3 is a schematic diagram of various components of an embodiment of a base station for a ventilator according to the present invention;

[0124] Figure 4 is a first schematic diagram of a valve-sensor assembly for a ventilator including a demand flow valve of a first embodiment according to the present invention;

[0125] Figure 5 yes Figure 4 A second schematic diagram of a valve-sensor assembly;

[0126] Figure 6 yes Figure 2 and Figure 4 Schematic diagram of the operation of a demand flow valve of a valve-sensor assembly at various rotational positions of the demand flow valve;

[0127] Figure 7 is a schematic exploded view of a demand flow valve of a second embodiment of a valve-sensor assembly for a ventilator according to the present invention;

[0128] Figure 8 is a schematic diagram of various electronic components of an embodiment of a controller for a valve-sensor assembly of a ventilator according to the present invention;

[0129] Fig. 9 is a schematic diagram of the experimental setup used to test and compare the prototype ventilator with commercial ventilators;

[0130] Fig.10 is a comparison of different measurement graphs of pressure and gas flow over time in a first operating mode (CPAP) of a leading conventional ventilator (left) and a ventilator according to the invention (right);

[0131] Fig.11 Yes Fig.10 Comparison of different measurement graphs of pressure and gas flow over time of a leading conventional ventilator (left) and a ventilator according to the invention (right), but in a second operating mode (ATC). DETAILED DESCRIPTION

[0132] FIG1 shows a schematic diagram of a typical arrangement of an existing ventilator 2 connected to a patient (not shown). In most cases of mechanical ventilation, an ETT 70 is inserted into the patient's trachea. The ETT is connected to an elastic tube 50 via a rotary connector 60. The elastic tube 50 is connected at its distal end to the patient-side outlet of a so-called Y-piece 8. Here, the gas flow circuit is divided into two branches, namely a first tube 30 and a second tube 40, the first tube 30 supplies inspiratory gas to the patient from the ventilation unit 7 during the inspiration phase, and the second tube 40 leads to an outlet valve 6 in the ventilation unit 7 to discharge the exhausted gas during the expiration (expiration) phase.

[0133] The pressure and gas flow supplied to the patient during the inhalation phase are controlled via a demand flow valve 3 located in the ventilation unit 7. As an alternative or in addition to the demand flow valve 3, a suitable blower (not shown) can be directly controlled to control the pressure and gas flow. In addition, sensors 4, 5 for pressure and gas flow are located inside the ventilator unit 7, directly behind the valves 3, 6 in the direction of the patient. Based on the values ​​measured by these sensors 4, 5, the valves 3, 6 can be controlled.

[0134] The Y-piece 8 is usually arranged in the tube system at a distance a of about 1.5m-2m from the ventilation unit 7. Therefore, the valves 3, 6, especially the demand flow valve 3 and the sensors 4, 5 are correspondingly far away from the patient, i.e. usually around 2m. This positioning leads to the problems mentioned above.

[0135] For comparison with this prior art, Figure 2 The arrangement of an example of a ventilator device 1 according to the invention is schematically shown. Here too, an ETT 70 is connected to a swivel connector 60 which in turn is connected to an elastic tube 50 .

[0136] However, in contrast to the prior art, the flexible tube 50 is not connected at its distal end to a conventional Y-piece, but to a valve-sensor assembly 80, which comprises a controllable demand flow valve 81 and measuring devices 86, 87, 88 for measuring pressure and gas flow, here a pneumotachograph 86 (wherein, as will be explained later, the pressure P aw The demand flow valve 81 has the function of a Y-piece, because in the demand flow valve 81, the gas flow circuit is divided into two branches, namely the first tube 30 (inspiratory duct 30) for inhaled gas during the inspiration phase and the second tube 40 (expiratory duct 40) for exhaling the exhaled gas during the exhalation phase. In other words, the demand flow valve 81 is a Y-piece 8Y that integrates the functions of a demand flow valve and a PEEP valve.

[0137] The valve-sensor assembly 80 is located relatively close to the patient, so the dead space from the distal end of the patient interface 70 (here, ETT 70) to the demand flow valve 81 is relatively small. Figure 2 In the typical configuration shown for an adult patient, the demand flow valve 81 can be connected to the patient via a respiratory flow meter (length about 5 cm), an elastic tube 50 (profile length about 20 cm), and a swivel connector 60 (profile length about 5 cm). The total distance to the airway opening is then 30 cm, and the total dead space is 51 cm 3 (13cm 3 From the demand flow valve prototype, 5cm 3 From respiratory flow meter, 29cm 3 From elastic tube, 4 cm 3 As explained above, the distal end of the patient interface 70 (here the connection point from the ETT 70 to the swivel connector 60) is defined as the "airway opening". If, optionally, a passive humidifier / filter is added between the respiratory flow meter and the flexible tube, such as Figure 4 and Figure 5 Example shown, this would increase the dead space by another 5cm 3 .

[0138] It should be noted that the ETT 70 is only one example of the patient interface 70. Depending on the situation, another patient interface, such as a TT, a mask or a helmet, etc., may also be used instead of the ETT 70.

[0139] like Figure 2 As shown, each tube 30 , 40 is connected to a corresponding port 24 , 25 in the housing 10 h of the base station 10 of the ventilator 1 in an upstream direction of the Y-piece 8Y with the integrated demand flow valve 81 , away from the patient.

[0140] The circuit for the suction branch leads to the first controllable blower 15 inside the housing 10h. The breathing air is supplied by the air-O 2 The mixer 11 is supplied via a pressure reducing valve (pressure regulator) 12 to a first controllable blower 15. The blower 15 ensures a defined, adjustable overpressure, for example between 0 and approximately +100 mbar above the ambient pressure, in order to support the suction.

[0141] The circuit for the exhalation branch leads to a second controllable blower 19, which is connected on the other side to an outlet 17 for used air and which can, if necessary, provide a negative pressure relative to the ambient pressure on its suction side (the side facing the patient), for example between 0 and -100 mbar, to support exhalation.

[0142] Based on various embodiment examples, reference will be made to Figures 3 to 8 The structure of the base station 10 and the structure of the valve-sensor assembly 80 (in particular the demand flow valve 81), as well as their operating modes, are explained in more detail.

[0143] First, use Figure 3 Explain in more detail the structure and function of the base station 10, Figure 3 An overview is provided of the arrangement of the various components in the base station 10. For clarity, the power supply (for the computer / microcontroller, blower motor and DC motor servo controller, and (if required) for the demand flow valve and valve controller in the valve-sensor assembly placed near the patient) is not shown here.

[0144] Used to set the required inspired oxygen fraction (Fi,O 2) is provided by an air-oxygen mixer 11, which is fed from a central gas source or compressed gas cylinders in the hospital via ports 11a, 11b. The mixer 11 includes pressure reducing valves 11c, 11d to reduce the gas pressure to a typical value of ~1.5 bar (about 1.5 bar), which is then further reduced to near atmospheric pressure (0 mbar) by a pressure regulator 12. A breathing valve 13 (pressure / vacuum safety valve 13 open to the atmosphere via port 14) ensures that the pressure there remains close to zero in the event of a failure of valves 11c, 11d or blower 15, as will be explained below.

[0145] The air-oxygen mixture is then pressurized to a value of up to +100 mbar (typically +40 mbar) using a (radial) blower 15 and is then delivered to the demand flow valve via port 24 and inspiration duct 30. To reduce high frequency acoustic noise, a silencer 16 or muffler may be used.

[0146] It is also possible to generate pressure directly with an electronic, pneumatic or manually controlled pressure reducing valve without a blower. In this case, the breathing valve should also be controllable.

[0147] In a practical prototype embodiment, the radial blower 15 is driven, for example, by a DC motor servo controller 21 which allows variable motor speed and thus variable pressure. The motor speed (and pressure) is controlled by a microcontroller of the controller 26 or a computer of the base station 10 via I 2 C serial interface settings. However, changing the pressure is not mandatory. The benefit of variable pressure is improved patient safety, since the lowest possible pressure can be selected and applied (depending on the patient's breathing pattern and ventilation mode).

[0148] The pressure delivered by the blower 15 is measured by a pressure transducer 23 and monitored by the microcontroller. This is not mandatory, since the pressure delivered by the radial blower 15 (for a given motor speed) remains almost constant over a wide range of gas flow rates. However, the pressure measurement allows any malfunction of the blower 15 and upstream (and downstream) pneumatic components to be detected more easily. Alternatively, a respirometer or flow meter ( Figure 3 ) to measure gas flow, for example to detect leaks or device malfunctions.

[0149] The expiration tubing 40 leading from the patient via the port 25 of the base station 10 is connected to the negative pressure source 19. This is optional, but allows compensation of the flow resistance of the expiration tubing (including the endotracheal tube) during expiration. If such compensation is not required, or if a high PEEP value (positive end-expiratory pressure at the patient's airway) has been selected, the expiration outlet of the demand flow valve can be opened directly to the atmosphere without the need for a tubing (not shown here) between the demand flow valve and the base station 10.

[0150] In a practical prototype embodiment, a radial blower 19 generates a negative pressure of up to -100 mbar below atmospheric pressure, typically -20 mbar. Other negative pressure sources, such as a venturi valve or a different type of pump are also possible. The blower outlet is then open to the atmosphere 17. Optionally, especially in the case of a blower as a pressure source, a muffler 18, 20 or a silencer can be used to reduce high-frequency acoustic noise.

[0151] As with the positive pressure source 15, the radial blower 19 of the negative pressure source can optionally be controlled by a DC motor servo controller 21 connected to a microcontroller. The negative pressure can optionally be monitored with a pressure transducer 22. For safety reasons, a minimum negative pressure can be selected and applied (depending on the patient's breathing pattern and ventilation mode). A respiratory flow meter or flow meter ( Figure 3 ) to measure gas flow, for example to detect leaks or device malfunctions.

[0152] The controller 26 or computer in the base station 10 is optional and is useful if variable positive or negative pressure and monitoring of the delivered positive and negative pressures is required. In addition, for safety reasons, the controller 26 can monitor the motor speed of the radial blowers 15, 19, the motor temperature, or the temperature within the base station 10. An RS232 serial connection can be used as an interface 29 to and from the demand flow valve (as explained later) and can be looped through the microcontroller of the controller 26 so that the base station 10 can (optionally) be informed of the current required pressure and demand flow. Also optionally, the controller or computer provides a user interface 27, 28 and communicates with the controller 90 of the demand flow valve 81 (see Figure 8 ), for example to set ventilation parameters or control parameters.

[0153] A computer or controller, laptop, tablet or similar device with a display 28 or screen and an input device 27 (e.g., a mouse, touch screen, keyboard) can be used as a user interface 27, 28 to

[0154] - Display of pressure, flow, volume graphs, ventilator parameters (e.g. respiratory rate, tidal volume, minute ventilation),

[0155] - display and change the current settings of the ventilator 1 (e.g. ventilation mode, PEEP, pressure support level, tube compensation, scale factor for proportional assist ventilation, trigger threshold, target minute ventilation, alarms),

[0156] - display, change or calibrate the control parameters for the demand flow controller 90 (e.g. PID parameters, pressure and flow calibration, zero position of the rotary encoder),

[0157] -Store and retrieve measurements and log files,

[0158] - Communicate with, service or reprogram the demand flow controller 90 and the base station controller 26 , 90 .

[0159] The user interface software may be provided by a dedicated computer or controller, or may also be provided by the demand flow controller 90 or the base station controller 26. The interface may also include an interface to a hospital IT network (such as M-HIS / M-PDMS) or another network to exchange any data.

[0160] Next, we will use Figures 4 to 8 The structure and function of the valve-sensor assembly 80, 80' and in particular the structure and function of the demand flow valve 81, 81' are explained in more detail. Figure 4 , Figure 5 , Figure 6 and Figure 8 A first prototype embodiment of a valve-sensor assembly 80 is shown, which is also shown in FIG. Figure 2 It is shown in Figure 7 A second prototype embodiment of a valve-sensor assembly 80' is shown. The first embodiment comprises a demand flow valve 81 with gas flow in a plane from inlet to outlet, the second embodiment comprises a demand flow valve 81' with a gas flow outlet perpendicular to the inlet, as described later.

[0161] In the following, the first embodiment will be described first, whereby the explanations on the first embodiment, in particular on the operating mode, apply in the same way to the second embodiment, unless explicitly mentioned otherwise.

[0162] Figure 4 and Figure 5 A first prototype embodiment of a valve-sensor assembly 80 is shown from two different external views. The valve-sensor assembly 80 comprises a Y-piece 8Y connecting two tubes 30, 40 for an inspiratory airflow circuit and an expiratory airflow circuit to the patient. For example, an air / oxygen mixture with a positive pressure (e.g. +40 mbar) may be provided at the tube 30 for the inspiratory airflow circuit, and a negative pressure, e.g. -20 mbar (or atmospheric pressure) may be provided at the tube 40 for the expiratory airflow circuit.

[0163] As can be seen from these figures, the Y-shaped piece 8Y housing the demand flow valve 81 is connected in the direction toward the patient to a respiratory flow meter or other device for flow sensing (flow sensor) 86, which is connected to the bacterial filter / humidifier 51, which is then connected to a swivel connector (see Figure 2 ) and a short elastic tube 50 for an endotracheal tube or other patient interface.

[0164] A controller 90 with a pressure sensor is located in a housing on the upper side of the Y-shaped piece 8Y. Via a short tube 86I leading from the flow sensor (here a respiratory flow meter) 86 to the pressure sensor, the pressure difference across the resistance element in the flow sensor 86 can be determined, as will be described later in conjunction with Figure 8 Explained.

[0165] Figure 2 and Figure 6 The figures respectively show a front view of the interior of a Y-shaped member 8Y having a demand flow valve 81 .

[0166] As from Figure 2 and Figure 6 It can be seen that in the first prototype embodiment, the demand flow valve 81 is a rotary three-way valve that connects the outlet 85 (toward the patient) of the valve housing 82 to the positive pressure side or the negative pressure side (i.e., to the inspiratory duct 30 through the connecting tube or port 83, and to the expiratory duct 40 through the connecting tube or port 84). The rotation is driven by the servo motor 96 ( Figure 5 ) to facilitate, but a solenoid or rotary solenoid valve or other electric motor is also possible.

[0167] Figure 6 In the middle row are schematic diagrams of the demand flow valve 81 from left to right in four different rotational positions (also referred to as “valve positions” for short) of the rotatable closing element 89, which is rotatable about the center axis A in the valve housing 82. The bottom row shows the rhombus shape of the (valve) orifice 89o of the closing element 89 of the three-way valve in each corresponding position relative to the circular (inlet) orifice 83o of the connecting tube 83 of the valve housing 82 leading to the inhalation duct 30 and the circular (inlet) orifice 84o of the connecting tube 84 leading to the exhalation duct 40. The size of the opening 89t of the closing element 89 in the direction toward the outlet 85 is designed to completely overlap with the outlet 85 in any rotational position shown in the middle row. Figure 6 In the upper row, the airway pressure P at outlet 85 is aw Shown is a function of the position of the closure element 89 shown in the middle row.

[0168] As from Figure 6 It can be seen that counterclockwise rotation increases airway pressure P aw, clockwise rotation will reduce airway pressure P aw .exist Figure 6 (and in Figure 2 ;Please note that Figure 6 and Figure 2 The first position of the valve is schematically shown from the opposite side, and the demand flow valve 81 is shown in the "inspiratory" position. Here, the airway pressure P aw (actually by a pressure source, such as a blower 15 (see Figure 3 Maximum pressure P delivered max .exist Figure 6 In the second position, the pressure at the outlet 85 toward the patient is reduced by the demand flow valve 81. The third position is the "neutral position" NP. In the neutral position NP, an (optional) small overlap with the positive and negative pressure orifices allows airflow to pass between the positive and negative pressure sides to improve the pressure control accuracy under low flow conditions (such as end-expiration). In the fourth position, the demand flow valve 81 is shown in the "expiratory" position, in which the overlap of the orifice 89o of the closing element 89 and the orifice 84o of the connecting tube 84 leading to the exhalation duct 40 is maximized. Here, the airway pressure P aw (actually by a pressure source, such as a blower 19 (see Figure 3 ) Maximum negative pressure (minimum pressure) P min .

[0169] The gas flow rate is determined by the flow resistance and the pressure difference acting on both ends of the inlet orifice 83o, 84o-valve orifice 89o pathway. The flow resistance is determined by the two orifices ( Figure 6 83o, 89o or 84o, 89o in the demand flow valve 81). By increasing the overlap, the internal gas flow resistance of the demand flow valve 81 is reduced, thereby increasing the gas flow rate. The shape of the orifice 89o of the rotating closing element 89 and the shape of the orifices 83o, 84o of the pressure inlets 83, 84 determine the shape of the overlapping area, thereby determining the valve resistance as a function of the rotation angle. As in the first prototype embodiment, the inlet orifices 83o, 84o both have a circular shape, and the orifice 89o of the rotating closing element 89 has a diamond shape, and the overlapping area between the two orifices depends roughly on the square of the angular position of the valve until about 50% of the relative area overlaps. For a constant pressure difference, this results in an approximately linear relationship between the gas flow rate and the angular position of the valve. For an overlap greater than 50%, the flow rate increases less-than-proportional with increasing angular position until the maximum flow rate is reached when the overlap reaches a maximum value.

[0170] Since the orifice of the rotary valve can only overlap with the orifice of one of the two pressure inlets at any given time (in a typical configuration), the position of the rotary valve also determines the direction of gas flow (inspiration or exhalation), and therefore the valve can be used to control airway pressure during both inspiration and exhalation.

[0171] In the neutral position NP, the orifice of the rotary valve generally does not overlap with either of the two orifices of the pressure inlet, effectively sealing or blocking both inlets, and thereby also sealing or blocking the outlet, so that no gas can flow. However, as explained above with respect to the first embodiment, it may be desirable to allow a small amount of gas flow to bypass from the positive pressure inlet to the negative pressure inlet in the neutral position so that the pressure outlet is never completely blocked. Such bypass flow may improve the accuracy and speed of the valve when switching between inspiration and exhalation, and vice versa. The bypass flow may be achieved by an orifice of the rotary valve that is slightly larger than the distance between the orifices of the two pressure inlets, such as Figure 6 shown.

[0172] In a preferred embodiment (not shown), the demand flow valve comprises a mechanism for adjusting between a first setting, in which a bypass flow is possible in a neutral position NP, and a second setting, in which both inlets are completely closed in a neutral position NP. Therefore, the closing element can preferably be mounted in the valve housing so that it is slightly displaceable along the rotation axis A relative to the orifices 83o, 84o of the pressure inlets 83, 84. By means of such a mechanism, the overlap between the orifice 89o of the rotating closing element 89 and the orifices 83o, 84o of the pressure inlets 83, 84 in the neutral (rotational) position NP can be varied, depending on the axial position of the closing element. Preferably, there is an overlap in the neutral position NP of the first axial position, and there is no overlap in the neutral position NP of the second axial position, i.e. the valve is completely closed in the second axial position.

[0173] In particular, such a mechanism can be implemented in an embodiment having a diamond-shaped orifice 89o of the rotational closure element 89 and circular orifices 83o, 84o of the pressure inlets 83, 84, as shown in FIG. Figure 6 Then, a slight displacement in the axial direction is sufficient to make the tips of the diamond-shaped orifices 89o (such as Figure 6 The bottom row (shown in the third picture from the left) no longer overlaps the circular apertures 83o, 84o.

[0174] This can also be done by something like Figure 7 The design of the illustrated embodiment works well.

[0175] In a first embodiment, the pressure inlet is connected to the valve housing in a straight arrangement and, as mentioned above, the outlet is in the same plane as the inlet. Figure 6In the embodiment of the present invention, the pressure inlets 83', 84' (connecting the tubes 83', 84' to the inspiratory duct 30 and the expiratory duct 40) are connected to the valve housing 82' in a curved arrangement, and the outlet 85' is perpendicular to the pressure inlets 83', 84'. The curved pressure inlet combined with the perpendicular outlet can achieve a more compact design and can further reduce the internal volume (dead space) of the valve. A grid structure or a laminar flow tube array can be inserted into the valve outlet 85' ( Figure 7 85') to prevent flow turbulence in a flow meter or respiratory flow meter connected to outlet 85'.

[0176] exist Figure 7 In the illustrated exemplary embodiment, the valve housing 82' of the demand flow valve 81' (which also forms a Y-shaped member 8Y as a whole) is basically composed of a central portion 82a' extending annularly around the rotation axis A', a cover 82b' arranged on a first end face (right front in the figure) of the central portion 82a', and a base portion 82c' arranged on the other end face of the central portion 82a'. In the assembled state, the central portion 82a' is sealed against the cover 82b' and the base portion 82c' by annular seals 100, 101, respectively. The outlet 85' is arranged coaxially with the rotation axis A' on the cover 82b'. Two pressure inlets 83', 84' are radially connected to the central portion 82a' and are bent to extend in a direction opposite to the outlet 85' along the side of the central portion 82a'.

[0177] A closing element 89 ′ having a diamond-shaped valve orifice 89 o ′ is arranged inside the central portion 82 a ′. The closing element 89 ′ is rotatably mounted between two ball bearings 102 , 103 .

[0178] On the side of the base part 82c' facing away from the central part 82a', the base part 82c' is connected by a flange to a motor 104, which is coupled to the closing element 89' via a shaft (not shown) extending along the rotation axis A', so as to rotate the closing element 89' in a controlled manner. This motor 104 is arranged in a motor housing 105. On one side of the motor housing 105, a (relatively flat C-shaped) housing 106 for various electronic components 108 (including motor driver, valve controller, pressure sensor, encoder, etc.) is arranged. On the side facing away from the motor 104, the electronics housing 106 is covered by a panel 107 and, on the front side close to the valve housing 82', by an angle element 110, where two ports 109 are located, which are used for pressure pipes to the pressure sensor of the electronics and then to the flow sensor (not shown). On the front side facing away from the valve housing 82', the motor housing 105 and the electronics housing 106 have a common cover 111.

[0179] Such a design is, for example, particularly space-saving and can therefore be easily accommodated in the vicinity of the patient.

[0180] It will be appreciated that the various electronic components of the electronics 108 are appropriately connected (directly or indirectly) to the motor 104 and any other elements to be controlled and / or measured, as will be explained later.

[0181] Regardless of the specific embodiment, the task of the demand flow valve 81, 81' according to the present invention is to mix the pressures from two pressure inlets, one positive pressure (e.g. typically +40 mbar) and the other negative pressure (e.g. typically -20 mbar) to the desired airway pressure. An alternative way to describe the function of the demand flow valve 81, 81' is that it delivers as much required gas flow as possible from the two inlets to maintain the desired airway pressure or the desired gas flow in and out of the patient. The direction of the gas flow from the positive pressure inlet is always towards the demand flow valve 81, 81', and the direction of the gas flow from the negative pressure inlet is always away from the demand flow valve 81, 81'. The direction of the gas flow at the outlet can be bidirectional. The patient's inhalation is defined as a forward flow away from the valve toward the patient; exhalation is defined as a reverse flow away from the patient toward the demand flow valve. Unlike the demand flow control methods and valves used in conventional ventilators, which are effective only during inspiration, and a separate expiratory valve controls pressure and flow during exhalation, the demand flow valve described herein controls airway pressure (or gas flow) during both inspiration and exhalation.

[0182] The following explanations about the controller design of the valve and about the apparatus and method for measuring and / or recording pressure values ​​and gas flow values ​​also apply to any other embodiments of the demand flow valve, and in particular to the demand flow valve 81' of the second prototype embodiment, even though these explanations are mainly based on examples in combination with the first embodiment.

[0183] The rotation of the demand flow valve (the closing element 89, 89' of the demand flow valve 81, 81', respectively) can be achieved by a motor (as described above) or other form of actuator. In the second prototype, a stepper motor and an integrated stepper motor driver were used, but any other actuator, such as a DC motor, a servo motor (as in the first prototype) or a pneumatic actuator is also possible. The rotational position of the demand flow valve (the closing element of the demand flow valve, respectively) can be measured with a magnetic encoder. The actuator (e.g., a motor) and the valve (with a closing element inside the valve housing) are preferably connected via a plug-in connection so that the part of the valve unit that is in direct contact with the oxygen / air entering and leaving the patient can be separated from the actuator and the controller for cleaning and disinfection, or replaced when necessary.

[0184] For demand flow control of demand flow valves 81, 81' used for mechanical ventilation of patients, the controlled variable is the airway pressure, which should preferably be measured accurately and continuously without significant delay. In certain modes of mechanical ventilation, such as automatic tube compensation (ATC) with or without proportional assist ventilation (PAV), the target airway pressure is further adjusted by the currently acting gas flow, so the currently acting gas flow should also preferably be able to be accurately measured without delay.

[0185] Gas flow can be measured in a variety of ways, such as by hot wire anemometer or eddy current detection. For example, in a prototype embodiment, gas flow is measured by the pressure difference across a small resistance element (respiratory flow meter). Respiratory flow meter 86 is located between demand flow valve 81, 81' and the patient's airway. One of the two pressure lines of respiratory flow meter 86 (usually the pressure line on the patient side) can be split to measure airway pressure using a separate pressure sensor, such as Figure 2 and Figure 8 shown.

[0186] As mentioned above, flow and pressure measurements are affected by delays caused, for example, by the speed of sound or by the low-pass characteristics of the compliance of the pipe. In addition, rapid pressure changes can excite oscillations of the air column in the pipe, resulting in huge measurement errors. In order to reduce errors and avoid measurement delays, the distance between the measurement point and the pressure sensor and therefore the length of the pipe should preferably be as short as possible. In the prototype, the distance is less than 10 cm. Miniature high-precision silicon ceramic piezoresistive pressure sensors (Honeywell HSC series) can be used to measure airway pressure and gas flow.

[0187] The electronic components that are part of the valve-sensor assembly 80 (demand flow valve and sensor unit) are Figure 8 In this figure, the dotted lines represent pneumatic components.

[0188] As can be seen here, the various pressure sensors used to detect the pressure (and gas flow) in the respiratory flow meter 86 can also be part of the controller 90 (as in the first and second embodiments), or at least arranged in the controller housing, and these pressure sensors can be connected to different parts of the respiratory flow meter 86 via small and short pressure tubes.

[0189] Two important electrical components are the differential pressure transducers (pressure sensors 97, 98) for measuring gas flow and airway pressure, which, as explained in the previous section, should be placed as close to the patient's airway opening as possible. In addition to the rotary encoder 93 for measuring valve position, Figure 8All other components depicted in FIG. 1 (motor driver 92 for powering valve actuator / motor; μ-controller 91 for executing the demand flow control algorithm (controlling motor and valve position according to ventilation mode and communication with base station, calculating resistance loss of endotracheal tube, etc.)) can be placed at a more remote location, such as at base station 10 (see FIG. 1 ). Figure 2 ) at the base station 10. However, this would require a large number of electrical signal lines and power lines between the base station 10 and the valve-sensor assembly 80, which may impair the quality of the electrical signal. By placing all the electrical components of the valve-sensor assembly 80 in a compact housing, such as Figure 7 and Figure 8 As depicted, the only electrical connections between the base station 10 and the valve-sensor assembly 80 are the power (GND, +24V) line 94 and the serial RS232 signal (GND, Rx, Tx) line 95 .

[0190] In the prototype, the motor driver 92 is a Trinamic TMC2209, the magnetic rotary encoder 93 is an AMS AS5600, and the μ-controller 91 is a PJRC Teensy 4.0 based on an ARM Cortex-M7 600MHz processor. The μ-controller 91 can send short digital pulses to the motor driver 92 for stepper motors ( Figure 8 Each micro-step (not shown) in FIG. 1 . In addition, the μ-controller 91 can set the direction and micro-step size via digital (TTL) signals. The magnetic rotary encoder 93 can set the direction and micro-step size via I 2 The C serial communication line sends the current position of the stepper motor to the μ-controller 91, which in turn sends the valve position to the μ-controller 91 to ensure that no steps are missed.

[0191] μ-controller 91 can be connected via I 2 The C serial communication line reads the current airway pressure and the pressure difference across the respiratory flow meter 86, calculates the gas flow and the volume delivered, calculates the pressure drop across the endotracheal tube, calculates the target airway pressure according to the ventilation mode, and controls the position of the demand flow valve according to the feedback control algorithm (in the prototype, a PID controller is preferably selected). The μ-controller 91 sends airway pressure and flow signals to the base station 10 via the RS232 communication line, and receives commands and settings from the base station 10.

[0192] If the currently measured airway pressure is lower than the target airway pressure, the PID controller tends to rotate the demand flow valve 81, 81' (the orifices 89o, 89o' of the closing elements 89, 89' of the demand flow valves 81, 81', respectively) more toward the positive pressure inlet. Conversely, if the currently measured airway pressure is greater than the target airway pressure, the PID controller tends to rotate the demand flow valve more toward the negative pressure inlet. It is also possible to directly control the gas flow instead of the pressure, for example to simulate a volume-controlled ventilation mode with a constant inspiratory flow rate. In this case, if the currently measured gas flow is lower than the target flow, the PID controller tends to rotate the demand flow valve more toward the positive pressure inlet, and vice versa. The parameters of the PID controller are optimized based on the performance of the actuator / motor and the valve resistance to achieve maximum speed and accuracy with minimal pressure oscillations. In the second prototype, the PID controller is combined with a stepper motor controller to ensure that the acceleration of the motor remains within its physical limitations.

[0193] As described above, the target airway pressure can be set according to any established ventilation mode, but preferably a ventilation mode such as ATC with or without PAV is used. In these modes, the target pressure P target can be determined according to equation (1) above, and the pressure drops ΔP(ETT), ΔP(Raw) and ΔP(Ers) can be calculated based on the continuously measured gas flow (V') and volume (V) according to equation (2-6c) and the above explanation.

[0194] The performance of the demand flow valve and method according to the present invention has been tested against the performance of a commonly used leading commercial off-the-shelf critical care ventilator (as a comparison product).

[0195] Therefore, two ventilation modes were tested for an endotracheal tube with a diameter of 7 mm (Rüsch, length 32 cm, flow resistance including swivel connector and elastic tube ~12 mbar s / l at 1 l / s):

[0196] 1) CPAP (continuous positive airway pressure), and

[0197] 2)ATC (Automatic Tube Compensation).

[0198] In CPAP mode, the ventilator should set the airway pressure P aw The ventilator should control the tracheal pressure P at a constant value regardless of the inspiratory or expiratory flow generated by the patient. trach Controlled at a constant value regardless of the inspiratory or expiratory flow generated by the patient.

[0199] The following is a test result of a comparative product (Hamilton S1). Fig. 9 is schematically shown in FIG.

[0200] The ventilator 1 (the second prototype embodiment of the valve-sensor assembly 80') or the comparative product (conventional ventilator 2) is connected to the ventilator unit side of the respiratory flow meter 86, which is connected to the bacterial filter 210 at the patient end, further connected to the elastic tube 50, and connected to the ETT 70 via the swivel connector 60. Note that Fig. 9 A similar notation to that of the first embodiment is shown in FIG. 1 because such notation is easier to explain.

[0201] The airflow is generated by a spontaneously breathing test subject (not shown).

[0202] Airway pressure P aw The tracheal pressure P is measured at the patient end of the respiratory flow meter 86; trach Measured 5 cm behind the patient end of the ETT 70, the ETT 70 is inserted and securely attached to an artificial trachea 211 (a tube with an inner diameter of 2 cm) by inflating the cuff. The other end of the artificial trachea 211 is connected to an interface piece 212 for the test subject.

[0203] Note that the respiratory flow meter 86 introduces a small additional flow resistance of ~0.7 mbar s / l (approximately 0.7 mbar s / l), which the commercial ventilator is not "aware of" and therefore cannot compensate for in CPAP or ATC mode. In addition, for hygiene reasons, a bacterial filter 210 was added between the ventilator and the test subject. This bacterial filter 210 introduces an additional flow resistance of ~2 mbar s / l (approximately 2 mbar s / l), which acts in series with the endotracheal tube resistance. This has no effect on comparing ventilators in CPAP mode, but makes a difference when comparing ventilators in ATC mode. Although such bacterial filters are commonly used to ventilate patients, commercial ventilators do not provide the option of compensating for their flow resistance. In contrast, the prototype ventilator 1 is programmed to also compensate for the resistance of the bacterial filter.

[0204] exist Fig.10 and Fig.11 In the figure, the measurement graph of the comparative product is shown on the left, and the corresponding measurement graph of the prototype according to the present invention is shown on the right, for better comparison.

[0205] Fig.10 The airway pressure P during 3 consecutive spontaneous breathing in CPAP mode (continuous positive airway pressure) is shown. aw(upper graph, in mbar) and flow fl (lower graph, in l / s) versus time t (in s). The positive end-expiratory pressure (PEEP) is set to 0 mbar. Therefore, the airway pressure P aw is expected to remain constant at 0 mbar. Deviations from this target pressure are indicated by the shaded area.

[0206] The comparison product shows that during the entire inhalation process, the airway pressure P aw The significant deviation from the target value is about -2.3 mbar. During the entire exhalation process, the airway pressure P aw The significant deviation from the target value was approximately +4 mbar.

[0207] Prototype displays airway pressure P aw There is almost no deviation from the target pressure. Only during the switch from inspiration to exhalation or from exhalation to inspiration does the airway pressure deviate from the target pressure briefly (~100ms) by a maximum of 2 mbar.

[0208] CPAP mode is often used to test extubation readiness. If the patient is able to breathe in CPAP mode for 30 minutes without fatigue, the patient is considered ready for extubation. However, airway pressure P aw Significant deviations from the target pressure add substantial additional work of breathing during inspiration and impede exhalation. This may result in patients who are ready for extubation being falsely deemed unready. In contrast, the prototype was able to precisely control airway pressure to the target pressure, except for a brief period (~100ms) during the switch between inspiration and exhalation where measurable deviations may occur.

[0209] Similar testing of 3 other commercial ventilators under CPAP was recently published (Sameed, Chatburn et al., 2023), and these published data also showed large deviations from target airway pressures during inspiration and expiration, prompting the authors to recommend that CPAP should no longer be used to test patients for extubation readiness. Overall, these measurements demonstrate the superior performance of the prototype ventilator compared to existing commercial ventilators.

[0210] Fig.11 The airway pressure P is shown during 3 consecutive spontaneous breaths in ATC mode (automatic tube compensation). aw (dashed line), tracheal pressure P trach (solid line) (upper graph, in mbar) and flow fl (lower graph, in l / s) versus time t (in s). The positive end-expiratory pressure (PEEP) is set to 0 mbar. Therefore, the tracheal pressure P trach is expected to remain constant at 0 mbar. Deviations from this target pressure are indicated by the shaded area.

[0211] The control product does not increase the airway pressure above PEEP during inspiration, so the tracheal pressure P trach During exhalation, the airway pressure P aw Failure to decrease below PEEP and tracheal pressure remains well above target pressure.

[0212] In the prototype, the airway pressure P aw During inspiration, it increases to well above PEEP, and during expiration, it decreases to well below PEEP. trach Keep the target pressure close to the target pressure. Only during the transition from inspiration to exhalation or from exhalation to inspiration, the tracheal pressure P trach There were only brief (~100ms) deviations from the target pressure, up to 5 mbar. Note that the test subjects generated greater inspiratory and expiratory flows (compared to breathing on a commercial ventilator) due to the full tube compensation provided by the prototype, which prevented additional work of breathing from flow limitation.

[0213] In summary, the comparison product did not provide any tube resistance compensation during both inspiration and expiration. In contrast, the prototype almost completely compensated for tube resistance at all times, demonstrating its superior performance compared to the leading existing commercial ventilator.

[0214] Therefore, as explained above, in a preferred embodiment, the present invention combines

[0215] - Subcritical low pressure demand flow valve close to the patient

[0216] -Pressure and flow sensors close to the patient

[0217] -Safety inspiratory circuit for driving inspiratory support (approx. +40 mbar)

[0218] -Safety expiratory circuit for driving expiratory support (approx. -20 mbar)

[0219] -ATC, flow and volume proportional assist modes

[0220] Optimized for supporting spontaneously breathing intensive care patients, especially those with ARDS.

[0221] Thus, the present invention allows the design of ventilation support to minimize the additional work of breathing caused by the resistance of the endotracheal tube, the resistance of the humidifier, the resistance of the expiratory tubing and the expiratory valve, and the delays in the demand flow and feedback control signals (airway pressure, gas flow) (caused by the finite speed of sound in the elastic tube). In addition, the present invention avoids patient-ventilator asynchrony by using the ATC mode in combination with flow and volume assistance (if necessary), thereby controlling the tracheal pressure (or alveolar, pleural or muscle pressure) instead of providing a predefined pressure support.

[0222] This will allow ARDS patients and other patients with respiratory insufficiency to breathe spontaneously. Therefore, the present invention can be particularly beneficial to patients who cannot currently be supported by existing advanced pressure support modes, which can cause additional breathing work and patient-ventilator asynchrony. The present invention can assist each of the patient's inspiratory and expiratory efforts with a level of pressure support (or pressure release during exhalation) synchronized with the patient's efforts, with minimal delay, and with a minimum intrathoracic pressure above PEEP. Therefore, the present invention can allow critical care physicians to adopt a ventilator support strategy that is expected to reduce ventilator-induced lung barotrauma and volume trauma, thereby reducing the mortality rate of ventilated ARDS patients.

[0223] Although the present invention has been disclosed in the form of preferred embodiments and variations thereof, it will be appreciated that many additional modifications and variations may be made thereto without departing from the scope of the invention. In particular, unless expressly stated otherwise, a single feature or group of features of an embodiment may also be effective in developing the invention independently of the other elements of that particular embodiment. For example, the type of motor / actuator used for the first embodiment may also be used for the second embodiment, and vice versa. For the sake of clarity, it will be appreciated that the use of "one" or "an" in this application does not exclude a plurality, and that "comprising" does not exclude other steps or elements. Reference to a "unit" or "device" does not exclude the use of more than one unit or device. The term "plurality" should be understood as "at least one".

[0224] References

[0225] Fabry, B., J. Guttmann, L. Eberhard and G. Wolff (1994a), "Automatic compensation of endotracheal tube resistance in spontaneously breathing patients", TechnolHealth Care healthy) 1(4):281-291.

[0226] Fabry, B., J. Guttmann, L. Eberhard and G. Wolff (1994b), "Treatment of patient-ventilator desynchronization with automatic tube compensation (ATC) and proportional assist ventilation", Int Care Med (International Nursing Medicine) 20(Suppl.2)(Supplement 2):38.

[0227] Fabry, B., J. Guttmann, L. Eberhard, T. Bauer, C. Haberthur and G. Wolff (1995), "Ananalysis of desynchronization between the spontaneously breathing patient and ventilator during inspiratory pressure support", Chest 107(5):1387-1394.

[0228] Fabry, B., C. Haberthur, D. Zappe, J. Guttmann, R. Kuhlen and R. Stocker (1997), "Breathing pattern and additional work of breathing in spontaneously breathing patients with different ventilatory demands during inspiratory pressure support and automatic tube compensation", Intensive Care Med (Critical Care Medicine) 23(5):545-552.

[0229] Guttmann, J., L. Eberhard, B. Fabry, W. Bertschmann and G. Wolff (1993), "Continuous calculation of intratracheal pressure in tracheally intubated patients", Anesthesiology 79(3):503-513.

[0230] Guttmann, J., L. Eberhard, B. Fabry, W. Bertschmann, J. Zeravik, M. Adolph, J. Eckart and G. Wolff (1995), "Time constant / volume relationship of passive expiration in mechanically ventilated ARDS patients", Eur Respir J (European Respiratory Journal) 8(1):114-120.

[0231] Sameed, M., R.L. Chatburn, and U. Hatipoglu (2023), "Bench Assessment of Work of Breathing During a Spontaneous Breathing Trial on Zero Pressure Sup-port and Zero PEEP Compared to T-Piece", Respir Care 68(6):767-772.

[0232] Description of Reference Numerals

[0233] 1 Ventilator / Respiratory Device

[0234] 2 Existing ventilators

[0235] 3 Demand flow valve

[0236] 4 Sensors

[0237] 5 Sensors

[0238] 6 Outlet valve

[0239] 7 Ventilation unit

[0240] 8. 8Y Y-shaped piece

[0241] 10 Base Station

[0242] 10h Housing

[0243] 11 Air-oxygen mixer

[0244] Ports 11a, 11b

[0245] 11c, 11d Pressure reducing valve

[0246] 12 Pressure regulator / pressure reducing valve

[0247] 13 Breathing valve (pressure / vacuum safety valve)

[0248] 14 Ports

[0249] 15 Pressure source / blower

[0250] 16 Muffler

[0251] 17 Outlet / atmospheric pressure

[0252] 18 Muffler

[0253] 19 Pressure source / blower

[0254] 20 Muffler

[0255] 21 Servo controller

[0256] 22, 23 Pressure transducer

[0257] Ports 24 and 25

[0258] 26 Controller

[0259] 27 User interface / input device

[0260] 28 User interface / display

[0261] 29 Interface

[0262] 30 First pipe / suction pipe / suction duct

[0263] 40 Second tube / expiratory tube / expiratory tube

[0264] 50 Elastic tube

[0265] 51 Bacteria filter / humidifier

[0266] 60 Rotary Connector

[0267] 70 Patient interface / endotracheal tube (ETT)

[0268] 80, 80' valve-sensor assembly

[0269] 81, 81' Demand flow valve

[0270] 82, 82' valve housing

[0271] 82a' Central part

[0272] 82b' Cover

[0273] 82c' Basic part

[0274] 83, 83', 84, 84' Connecting pipe / pressure inlet / port

[0275] 83o, 84o entrance orifice

[0276] 85, 85' export

[0277] 86 Measuring device / flow sensor / respiratory flow meter

[0278] 86l pipe

[0279] 87, 88 Measuring device / pressure sensor

[0280] 89, 89' Closing element / gate

[0281] 89o, 89o' valve orifice

[0282] 89 Opening

[0283] 90 Controller

[0284] 91 μ-Controller

[0285] 92 Motor Driver

[0286] 93 Rotary encoder

[0287] 94 Power supply line

[0288] 95 Signal line

[0289] 96 Servo Motor

[0290] 97, 98 Differential pressure transducer / differential pressure sensor

[0291] 100, 101 Ring seal

[0292] 102, 103 Ball bearings

[0293] 104 Motor

[0294] 105 Motor housing

[0295] 106 Electronic device housing

[0296] 107 Panel

[0297] 108 Electronic devices

[0298] Port 109

[0299] 110 Corner element

[0300] 111 Common lid

[0301] 210 Bacteria Filter

[0302] 211 Artificial trachea

[0303] 212 Interface parts

[0304] a Distance

[0305] A, A' axis

[0306] fl flow

[0307] NP Neutral Position

[0308] P aw Airway pressure

[0309] P trach Tracheal pressure

[0310] P max Maximum pressure

[0311] P min Minimum pressure / maximum negative pressure

[0312] t time.

Claims

1. A device (1) for providing ventilation assistance to a patient, comprising - a set of tubes (30, 40, 50, 60, 70) for the flow of gas (fl) to and from the patient, - demand flow valve (81, 81'), - a flow sensor (86), and - a pressure sensor (87, 88) for measuring airway pressure, in, The demand flow valves (81, 81') are located at a Y-piece (8Y) that connects a tube (30) for an inspiratory airflow circuit and a tube (40) for an expiratory airflow circuit to the patient.

2. The device according to claim 1, wherein: The demand flow valve (81, 81') is implemented and positioned so that the maximum dead space in the demand flow valve (81) and in the tube system (86, 50, 60, 70) from the demand flow valve (81, 81') to the connection point of the patient interface is 100 cm 3 , preferably 60cm 3 , more preferably 55cm 3 , and more preferably 30 cm 3 .

3. The device according to claim 1 or 2, wherein: The two tubes (30, 40) for the inspiratory airflow circuit and the expiratory airflow circuit connected to the Y-piece (8Y) are connected to a pressure source (15, 19), which provides a positive pressure of preferably about +40 mbar for the inspiratory circuit and a negative pressure of preferably -20 mbar for the expiratory circuit, wherein other pressure levels can be selected, including atmospheric pressure, if necessary.

4. The device according to any one of claims 1 to 3, wherein: The Y-shaped piece (8Y) accommodates the demand flow valve (81, 81').

5. The device according to any one of claims 1 to 4, wherein: The demand flow valve (81) is a three-way valve (81, 81').

6. The device according to any one of claims 1 to 5, wherein: The flow sensor (86) and the pressure sensors (87, 88) are placed in close proximity to the patient, preferably on the patient side of the demand flow valve (81, 81').

7. The device according to any one of claims 1 to 6, wherein: The Y-piece (8Y) is connected to a respiratory flow meter (86) or other device for flow sensing, which is optionally connected to a bacterial filter and / or humidifier (51), which is then preferably a short elastic tube (50) connected to a swivel connector (60) and a patient interface (70).

8. A device according to any one of claims 1 to 7, comprising means (26, 90, 91) for controlling the demand flow valve (81, 81') and preferably also for controlling the pressure source (15, 19) according to a predetermined mode of ventilator support.

9. The device according to any one of claims 1 to 8, wherein: The demand flow valve (81) is implemented such that in a neutral position of the demand flow valve (81), a small overlap allows air flow to pass between the positive pressure side and the negative pressure side.

10. The device according to any one of claims 1 to 9, comprising at least - a valve sensor assembly (80, 80'), the valve sensor assembly (80, 80') comprising the demand flow valve (81, 81') and the sensor (86, 87, 88), and - a base station (10) located remotely from the valve sensor assembly (80, 80'), the base station (10) comprising means (15, 19) for positive and negative pressure.

11. The device according to any one of claims 1 to 10, wherein: The set of tubes (30, 40, 50, 60, 70) for gas flow comprises at least one endotracheal tube (70) or tracheostomy tube, the endotracheal tube (70) or tracheostomy tube - have a maximum inner diameter of 7 mm in the adult version, preferably 6 mm, more preferably 5 mm, and even smaller if feasible, or - In the children's or infant version has a maximum inner diameter of 5 mm, preferably 2 mm.

12. A demand flow valve (81, 81') for a device (1) according to any one of claims 1 to 11, in particular a valve-sensor assembly (80, 80').

13. A method for controlling a ventilator (1), comprising the following steps: - measuring the gas flow rate with a flow sensor (86), - measuring the airway pressure using a pressure sensor (87, 88), - controlling a demand flow valve (81, 81') based on the gas flow and the airway opening pressure, The demand flow valve is located at a Y-shaped piece (8Y), and the Y-shaped piece (8Y) connects a tube (30) for an inspiratory airflow circuit and a tube (40) for an expiratory airflow circuit to a patient.

14. The method according to claim 13, wherein: At least one of airway pressure, tracheal pressure, alveolar pressure, pleural pressure and muscle pressure is controlled by controlling the demand flow valve (81, 81').

15. The method according to claim 14, wherein: Based on the gas flow and the airway opening pressure (P aw ) calculates the tracheal pressure, alveolar pressure, pleural pressure or muscle pressure, and controls the gas flow (fl) via the demand flow valve (81, 81') to keep the tracheal pressure constant and / or fully or partially compensate for the breathing work required to overcome airway resistance, lung elasticity and chest wall elasticity.

Images