Device and method for mixing oxygen into a breathing gas mixture

Abstract

Device for providing a breathing gas mixture consisting of at least two gases, comprising a user interface (11) designed as a breathing mask, a hose (10') supplying at least one of the gases to be mixed or a gas mixture and connected to a gas source (13), an oxygen hose (16) supplying oxygen and connected to an oxygen source, means (10") designed as a venting system for discharging the exhaled air, a control valve (15, 18) regulating the volume flow of at least one of the gases to be mixed, and a controller (7), wherein the device has at least one detection of the volume flow or the gas composition of at least one of the gases or gas mixtures to be mixed, and the controller (7) processes the at least one detected volume flow value of the at least one gas or gas mixture to be mixed.and controls the volume flow of at least one of the gases or gas mixtures to be mixed, characterized in that the controller (7) takes into account the exhaled air expelled by the patient under a certain pressure, counter to the breathing gas mixture supplied into the dead space of the breathing mask (11), and thus recognizes the patient's respiratory rate and breathing air requirement based on the reduced volume flow(s) and the calculated volumes, and regulates the inflow of one or both gases to be mixed according to the measured and determined quantities and taking into account the exhaled air escaping from the venting system (10") into the environment, wherein the controller (7) starts oxygen dosing immediately at the beginning of an inspiration phase and terminates it within the inspiration phase at a suitable time at which the effectiveness of oxygen uptake by the patient decreases.

Description

[0001] The invention relates to a device and a method for admixing oxygen into a breathing gas mixture for ventilating a patient.

[0002] The invention further relates to a device and a method for saving oxygen in ventilation, in particular in injector-operated emergency ventilators.

[0003] In many cases, supplying a patient with ambient air alone through a breathing mask is insufficient, and oxygen must be added. The oxygen concentration varies from the normal amount found in ambient air to a level of 60%. Breathing mask systems are known and available that deliver a gas mixture of oxygen and ambient air with a predetermined oxygen concentration to a patient's respiratory system via a breathing mask connected to a tube.

[0004] The oxygen is generally mixed with the ambient air in two different ways. According to one of the two gas mixture preparation methods, the oxygen is combined with the ambient air in a pre-chamber of an electromechanical device and then supplied via a hose to the breathing mask and thus to the patient's respiratory organs using a pressurized gas source. This type of air mixture preparation is primarily used in intensive care ventilators. According to the invention, gas sources can be alternatively air pumps, pumps, blowers, and compressed gas cylinders, or other sources of ventilation gases.

[0005] According to a second type of gas mixture preparation, the oxygen is delivered via a dedicated hose supply, preferably a thin, flexible tube installed inside the air supply hose of the breathing mask, into the so-called dead space of the breathing mask, i.e., the space formed below the airway bowl of a breathing mask and the areas of the patient's face covered by it, where the escaping oxygen mixes with the air. This type of air mixture preparation is primarily used in home ventilation systems.

[0006] Routing the oxygen tubing outside the air supply tubing to the breathing mask achieves the same result. The oxygen is usually compressed in a cylinder and therefore flows into the system under its own pressure. Ambient air is usually drawn in from a gas source and then passed under pressure to the mixing system.

[0007] A specific patient must receive a specific concentration of oxygen in their breathing gas mixture according to medical instructions, even without supervision for several hours or even days. Both of the above-described types of breathing gas mixture preparation have a fundamental problem, which arises from the patient exhaling used air.

[0008] The CO2-enriched exhaled air is exhaled by the patient into the aforementioned dead space of the breathing mask against the prevailing positive pressure. It can usually escape through the designated openings or through a special diffusion filter. This can push back the gas mixture in the supply air hose to such an extent that the oxygen enters the gas source via the air hose. There, due to its highly reactive chemical properties, it can cause fire damage in the area of ​​the gas source's electric motor, or require a more expensive, fire-resistant motor design.

[0009] A chemical oxygen sensor positioned in the dead space of the breathing mask is used to set the desired oxygen concentration based on the measured value. However, due to the inertia of the usually chemical oxygen sensor and the length of the air supply hose, which is typically about 2 m, this system can only ensure an accurate oxygen concentration in static operation, i.e., without a connected patient. The air exhaled by the patient causes backflow, which extends into the air supply hose and enriches the breathing gas mixture with CO2 gas.

[0010] Furthermore, the forward and backward movements of the gas mixture in the dead space of the breathing mask caused by the breathing periodicity cause the oxygen content there to vary greatly depending on the breathing phase. Oxygen sensors are used to monitor the oxygen concentration, which are preferably positioned directly in the dead space of the breathing mask. However, these chemical oxygen sensors have a large time constant, which introduces inertia into the measurement results, making it impossible to differentiate the oxygen concentration during different breathing phases.

[0011] Known solutions to these problems include, on the one hand, supplying an overly oxygenated breathing gas mixture and, on the other hand, regulating the oxygen level based on the oxygen level measured in the patient's blood. In the first case, in addition to the inefficient aspects, this can lead to an oversupply of oxygen to the patient, known as overoxidation. In the second case, a more complex system with a measurement of the oxygen level in the patient's blood is required.In addition, with the latter method there is an even longer time constant between a change in the oxygen concentration in the breathing gas mixture and a resulting change in the oxygen content in the patient's blood, which can be undesirable, at least during an adjustment phase, in particularly severely affected patients, since the patient is used as a measuring instrument for experimentally finding an optimal setting for a certain period of time.

[0012] In the medical community, the technical term "FiO2" has become widespread for the oxygen content in the air we breathe. The English breakdown of FiO2 is "fraction of inspired O2," which literally means "proportion of inspired oxygen." The efforts of all technical solutions and medicine are aimed at being able to specify the FiO2 as precisely as possible, although there is a greater or lesser difference between a theoretically specified, a measured, and the actual FiO2.

[0013] The publications considered as part of the technological background are listed here without individual description: WO 2005 / 051 280 A3, US 6 761 165 B2, CA 1 039 144 A.

[0014] A further problem is that highly concentrated oxygen is predominantly used as the ventilation gas in ventilation. This is particularly true in emergency ventilation, where the ventilator draws at least part of its operating energy from the connected gas cylinder.

[0015] To reduce oxygen waste, some devices already provide ventilation gas via an adjustable mix of oxygen and ambient air. In general, adequate ventilation of a patient requiring ventilation with 50% oxygen in the ventilation gas is completely sufficient for most patients.

[0016] Technically, this is usually achieved using a Venturi nozzle, which utilizes the Venturi effect to mix ambient air with the oxygen propellant. The oxygen flow is transferred from a gas source to the Venturi nozzle. The oxygen flowing from the Venturi nozzle creates a suction effect, which allows air to be drawn in from the surrounding area. The Venturi nozzle is controlled by an adjustable valve cone, facilitating easy adjustment of the oxygen dosage. This and other examples of the aforementioned Venturi nozzle are already described in DE 10 2004 030 747 A1.

[0017] In the field of long-term oxygen therapy, oxygen savings are achieved through so-called oxygen-conserving systems. These are usually connected to small oxygen cylinders or liquid oxygen tanks of less than 2 liters. The patient is connected to the system via a nasal cannula or breathing mask. During inspiration, the resulting negative pressure propagates to the device, is measured, and an adjustable bolus is delivered at the beginning of inspiration.

[0018] Due to the early release of oxygen during the inspiratory cycle, it reaches the lung areas, known as the alveoli, which are responsible for oxygen and carbon dioxide exchange. The remaining airways serve only to transport the inhaled air and are not equipped with functional lung tissue. These systems achieve savings of up to 5:1 compared to continuous flow operation.

[0019] Ventilators with a volume flow measurement for the respiratory gases are already known from DE 39 06 202 A1 and DE 23 21 574 B2.

[0020] EP 0 973 443 B1 describes a gas supply system with a volume flow measurement for respiratory gases.

[0021] DE 196 26 924 C2 describes a ventilator with an oxygen dosage and a volume flow measurement for the respiratory gases.

[0022] The present invention aims to design the preparation and delivery of a breathing gas mixture in such a way that the oxygen content of the breathing gas mixture effectively provided for inhalation, i.e., FiO2, can be determined dynamically more accurately without having to measure the oxygen content in the patient's blood or in the dead space of the breathing mask. At the same time, the problem of returning the oxygen to the gas source should also be solved.

[0023] This object is achieved with regard to the device to be provided in that the device has at least one detection of the volume flow of at least one of the gases or gas mixtures to be mixed, and the controller processes the at least one detected volume flow value of the at least one gas or gas mixture to be mixed, and controls the volume flow of at least one of the gases or gas mixtures to be mixed.

[0024] With regard to the method according to the invention, the object is achieved in that the distribution of the concentration of at least one portion of a gas mixture is determined at at least two points along the transport line.

[0025] According to the invention, the use of an oxygen sensor for determining the oxygen content is completely dispensed with. The measured values ​​required for the inventive control of the mixing of at least two gases or gas mixtures are obtained from at least one measurement of the volume flow of at least one of the gases or gas mixtures to be mixed. The flowmeters required for this purpose exhibit very good dynamic measurement properties with good accuracy, thus enabling very timely measurement of one or more volume flows.

[0026] According to the invention, not only volume flows are determined and controlled, but also, additionally or alternatively, mass flows. The terms volume flow / mass flow and volume flow or mass flow are used essentially synonymously.

[0027] Another important feature of the invention is the inlet point of the second gas to be mixed, oxygen, located between the two hose ends in the air supply hose. The optimal position of this inlet point was determined experimentally in a model, and the volume in the hose was mathematically divided into discrete volume segments in this model, each of which has a calculable oxygen concentration depending on location and time.

[0028] According to a preferred embodiment of the invention, the volume flow of at least one of the gases to be mixed is measured using at least one flow meter. The volume flow of the second gas or gas mixture can also be measured using a flow meter in a preferred embodiment, or alternatively, in another embodiment, can be specified as a constant volume flow, which can possibly be adjusted in several constant steps, in order to thereby adjust the breathing mixture volume.

[0029] At least one measured volume flow value is fed to a controller, which calculates the volume of one or both gases to be mixed from the measured value(s). The information about the volume of the second gas / gas mixture involved is then available to the controller either as a constant or as a measured value.

[0030] Since the flow measurement devices can dynamically follow the temporal sequence of inspiration and expiration phases (breathing in and out) very well, conclusions can be drawn from the obtained time-dependent signals regarding the respiratory rate and the patient's breathing air requirement, among other things.

[0031] During exhalation, the patient's exhaled air, expelled under a certain pressure against the breathing gas mixture delivered into the dead space of the breathing mask, causes a blockage of the two gas mixture streams. During this phase, the inflow of the breathing gas mixture from the hose slows, which the flow meters detect as a reduced volume flow. Based on the reduced volume flow(s) and the calculated volumes, the control system detects the patient's respiratory rate and breathing air requirement and, in a preferred embodiment, regulates the inflow of one or both gases to be mixed according to the measured and determined values.

[0032] The algorithm for determining the controlled variables for the control valves uses both a time and spatial discretization of the volume sections in the entire system supplying the gas mixture, mainly the hose and the dead space of the breathing mask, and is based on the measured volume flow rates of both gases or gas mixtures involved.

[0033] The measured volume flow rates are time-dependent due to the exhalation phases of the patient connected to the ventilation system. Their values, after an integration calculation over time, provide the respective volume for the period under consideration. If the integration time periods are broken down into small, discrete sections, the corresponding volumes of the two gases involved introduced into the system per time period are obtained.

[0034] By taking reference measurements of the oxygen concentration along a model formed in the supply tube at various simulated volume flow rates, an experimental analogue of the concentration formation and distribution as a function of the volume flow rates of the individual gases is obtained. In addition, a third gas mixture, namely exhaled air, periodically flows into the model space against the main flow of the respiratory gas mixture and, due to the increased CO2 content, periodically reduces the oxygen concentration, particularly in the dead space of the breathing mask.

[0035] Another important role in the system according to the invention is played by the venting system, through which the exhaled air can escape into the environment. Valves, defined leak openings, or diffusion filters are used for this purpose. The algorithm calculates the escaping air volume from the total flow of the breathing gas mixture, since this must all escape along with the exhaled air.

[0036] Through reference measurements in the same model, the CO2 sensors can also be used to determine the concentration and its temporal and spatial distribution in the respiratory gas-carrying system for different operating regimes and to take this into account in the algorithm in a mathematical representation.

[0037] In a preferred embodiment of the invention, the volume flow of the oxygen can also be regulated so that no oxygen is added during the expiration phase and a precisely required amount of oxygen is added during the inspiration phase.

[0038] The result is a mixing system for two gases or gas mixtures that is significantly more accurate without the use of an overly slow chemical-sensory determination of the oxygen concentration, which, with appropriately careful design of the system, enables improved accuracy in supplying a patient with the correct oxygen mixture for him.

[0039] Furthermore, the same principles and algorithms according to the present invention can also be applied to other technical fields and systems, including liquid substances, for more than two substances, and for a wide variety of applications where chemically operating sensors are too slow to detect dynamically changing mixture sizes, thus making application possible. Application is also possible in cases where the system is formed by a defined geometric and even quite complex shape, since the flow conditions can essentially be mathematically modeled according to the invention.

[0040] With the present invention, under such complex and similar conditions as a ventilation system that has a counterflowing expiratory air, it is possible to maintain significantly more accurate FiO2 values ​​according to the specifications than conventional systems can achieve.

[0041] With regard to the saving of oxygen, one object of the present invention is to improve a method and a device of the type mentioned in the introduction in such a way that the amount of oxygen consumed is reduced.

[0042] With regard to the method, this task is solved by providing a high oxygen concentration for a time period of an early inspiration phase compared to a remaining inspiration time at the end of a ventilation phase.

[0043] With regard to the device, this object is achieved in that the control and evaluation unit has a control program for specifying an oxygen dosage such that a high oxygen concentration is specified for a time range of an early inspiration phase compared to a remaining inspiration time at the end of a ventilation phase.

[0044] The advantage of this procedure is that only the portion of the breathing gas with a high oxygen concentration is provided, which can also be used physiologically for oxygenating the blood. The remaining breathing gas required for ventilation is optimized to minimize the amount of oxygen used. This results in a significantly extended duration of use of the available compressed oxygen.

[0045] With optimized injectors based on the Venturi principle for intake of ambient air, it is possible to extend the oxygen availability by a factor of 2 to 4.

[0046] By dosing highly concentrated oxygen at the beginning of inspiration, the best possible supply of oxygen to the alveoli is achieved, even if the oxygen concentration is reduced during subsequent inspiration. This reduction can be achieved by admixing ambient air or air from house systems, such as those found in hospitals, using a Venturi principle or similar. This gas with reduced oxygen concentration primarily serves to transport the bolus of high O2 concentration to the alveoli, although it only reaches the airways and not the areas with functioning lung tissue.

[0047] In one embodiment of the invention, the time-limited delivery of the high oxygen concentration at the beginning of inspiration can occur independently of the ventilation parameters. The time range of the increased oxygen delivery can be fixed.

[0048] In a further embodiment of the invention, the limited delivery of the high oxygen concentration can be dependent on ventilation parameters. For example, any combination of inspiratory time, inspiratory flow, and inspiratory pressure, as well as general pressure, flow, and volume criteria, for example, depending on the inspiratory time Ti, can be used with different weightings to determine the time range for the delivery of the high oxygen concentration.

[0049] Other physiological parameters such as hemoglobin level, etCO2, spO2, or other direct or indirect indicators of blood oxygenation can also be used. Furthermore, device-related parameters such as tube volume, volume of the entire ventilation path, device block volume, pneumatic resistance of the ventilator components, and other technical parameters necessary for calculating the correct time to administer oxygen can be incorporated into the process.

[0050] The time of bolus initiation must be pre-determined by the volume between the oxygen inlet and the mixture outlet, with a lead time t_x. This requires the evaluation of flow and ventilator volume, among other factors.

[0051] In another embodiment, the physiological, ventilation-relevant parameters are recorded using various sensors and subjected to a trend analysis. This attempts to predict the patient's next respiratory movements in order to optimally calculate the lead time t_x.

[0052] Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which functionally identical parts are designated by corresponding identical reference numerals. Fig. 1 shows a basic arrangement of a volume model of a preferred embodiment of the present invention, Fig. Figure 2 shows a flow chart of the algorithm for calculating the exit concentration and FiO2 of the preferred embodiment of the present invention, Fig. 3 shows an algorithm of FiO2 control, Fig. 4 shows a block diagram of the FiO2 control, Fig. 5 shows a graphical representation of the volume flow curve, Fig. 6 shows a schematic arrangement of a ventilation system according to the invention, Fig. 7 shows a longitudinal section through a Venturi injector with connected functional components, Fig. 8 shows a representation of a ventilation phase with oxygen dosage according to the invention, Fig. 9 shows a Fig. 8 modified representation taking into account a lead time and Fig. Figure 10 shows a diagram with constant oxygen dosage throughout the entire inspiration phase.

[0053] In Fig. Figure 1 shows a basic arrangement of a volume model of a preferred embodiment of the present invention. Generally speaking, a non-solid substance of the first type, a liquid or gaseous, with a volume Vins,n(cins,n) is introduced from a source 1 into a mixing chamber 2 that is elongated relative to its diameter and has a specific volumetric flow rate under pressure. At an inlet point 4, a non-solid substance of the second type, a liquid or gaseous, with a volume VO2,n, is introduced into the mixing chamber 2 under pressure. A mixture of the two non-solid substances with a volume Vadd3,n(cmix3,n) emerges from the mixing chamber 2.

[0054] The non-solid substance of the first type with the volume Vins,n(cins,n) has a concentration c1 of the non-solid substance of the second type. In the preferred embodiment, the second type is pure oxygen (or a highly concentrated oxygen mixture), and the first type is a gas mixture that essentially corresponds to atmospheric air. Preferably, the introduction point is designed as a pipe arranged in the direction of flow in the mixing chamber 2. The number n in parentheses next to the volume Vadd2,n(cmix2,n) stands for an imaginary discrete sub-volume whose concentration of the second non-solid substance contained therein, in this case oxygen, is a location- and time-dependent variable cmix.

[0055] At the exit from the mixing chamber 2, the mixture of the two mixed substances of the first and second type emerges with a total volume Vadd3,n(cmix3,n), which has a concentration of the second non-solid substance of cmix3,n, which also varies in discrete volumetric steps n in a ready-mixed chamber 5 depending on location and time. A non-solid mixture of the third type with the volume V3,n(cexp,n) is introduced into the ready-mixed chamber 5. In the preferred embodiment, this is the exhaled air of a person, with the air periodically changing its direction, oxygen, CO2 content, etc., depending on time and location.

[0056] Not shown are the volume flow or mass flow sensors that measure the two, or at least one of the two, volume flows of the two substances to be mixed, as well as control units, such as electromechanically controlled valves, by means of which a controller controls at least one of the volume flows depending on measured and existing volume flows or mass flows.

[0057] Furthermore, two further sections of the mixing chamber 2 are shown: anteroom 2' and postroom 2'' related to the inlet point 4

[0058] In Fig. Figure 2 is a flow chart of the exit concentration and FiO2 calculation algorithm of the preferred embodiment of the present invention.

[0059] The process is initially based on the values ​​for a respective basic concentration in the two sections of the mixing chamber 2, a value in the anteroom 2' and a value in the postroom 2'' related to the introduction point 4.

[0060] In the first process step, the measured values ​​of the volume flows V̇ insp,n , V̇ O2,n measured using volume flow sensors, or at least one value is recorded as a measured value if the other value is a constant flow. Since the volume flows are first time-dependent derivatives of the corresponding volume, the next step is to calculate the corresponding volume V from the measured volume flows. insp,n , V O2,n , V add2,n calculated in a control system. Using the values ​​then available, the control system calculates the mixed concentration c mix2,nFurthermore, the control system calculates the oxygen concentration for discrete volumes based on a suitable algorithm. Depending on the inspiration and expiration phases, a volume shift is calculated, resulting in an outlet concentration c. mix3,n for the finished gas mixture at the outlet end of the mixing chamber, which calculates the time-dependent displacement of the spatially discrete volume sections of different concentrations.

[0061] The escaping gas mixture is inhaled during an inspiration phase, if the timing is right for the patient's ventilation. If this condition is not met, the process branches back to the beginning.

[0062] To calculate FIO2, i.e., the oxygen content in the breathing gas mixture, a preferred embodiment uses an algorithm shown at the end of the diagram. Other, more precise algorithms are conceivable, both based on theoretical and experimental approaches.

[0063] In Fig. Figure 3 shows an algorithm for controlling the oxygen content, FIO2, of the breathing air.

[0064] The input variables are the therapy parameters for FiO2, which a physician prescribes for a specific patient, for example. These are entered into the system using an input unit.

[0065] In the next process step, a comparison is made between the specified FiO2 target value and the determined FiO2 actual value. From this comparison, one or two values ​​are provided for a subsequent process step in which the oxygen volume flow is controlled. To implement this volume flow control, a preferred embodiment of the invention provides electromechanically driven valves or actuators, each of which controls one of the non-solid substances involved, in this example, gases and gas mixtures.

[0066] In a simplified preferred embodiment of the invention, only one of the two substances to be mixed is equipped with a control, ie an electromechanical valve or an actuating unit, while a constant value is specified for the volume flow of the second substance involved, which is flow-hydraulically specified by a calibrated passage opening.

[0067] In the next step, the prepared breathing gas mixture is available for the patient’s ventilation.

[0068] The next step in the process includes the Fig. 2 described calculation of the FiO2 value from the measured volume flow values, from which the FiO2 actual values ​​for the closed control loop are determined and fed back to the beginning of the process step in which a setpoint-actual value comparison takes place.

[0069] In Fig. Figure 4 shows a block diagram of the FIO2 control system according to a preferred embodiment of the present invention. It includes a patient 12 as a subelement and comprises a controller 7 with a processing unit (CPU) contained therein, a pneumatic unit 10, a user interface 11, which in the preferred embodiment of the invention corresponds to a breathing mask, and a sensor unit 8 connected between the controller 7 and the pneumatic unit, as well as an actuator unit 9.

[0070] The pneumatic unit 10 comprises all parts relating to the pneumatics, such as the mixing chamber, which in a preferred embodiment is designed as a hose, and a second supply hose through which the oxygen is fed into the mixing chamber, as well as calibrated openings which, in terms of flow hydraulics, ensure a predetermined normal or maximum volume flow.

[0071] The controller 7 comprises a computing unit, which in the preferred embodiment is supplemented with the usual means for loading, maintaining, and temporarily storing data, as well as a data-related peripheral interface. It receives the measured signals from the volume flow sensors via this peripheral interface and processes them according to an algorithm running in the computing unit. As a result, the controller 7 outputs electrical signals corresponding to the computationally determined control variables via an output section of the peripheral interface to one or more control units that control the volume flow of a particular substance to be mixed.

[0072] In the preferred embodiment of the present invention, the user interface 11 is a breathing mask that serves as a link between the system preparing a breathing gas mixture and the patient.

[0073] Sensor unit 8 comprises the volume flow sensor(s), as well as the associated cables and any required signal converters. Hot-wire or differential pressure sensors, which have good dynamic properties, are preferably suitable as volume flow sensors.

[0074] The actuator unit 9 comprises one or more electromechanically driven control valves or actuating units that can vary the volume flow, as well as associated lines and any required signal converters.

[0075] In Fig. Figure 5 shows a graphical representation of the volume flow rate curve. In this preferred embodiment of the invention, the volume flow rate of the oxygen is constant, represented here by the solid line. The dotted line represents the volume flow rate of the air to be mixed with the oxygen, and the dashed line shows the curve of the total summed volume flow rate and / or O2 regulation of the prepared breathing gas mixture. It can be seen that inspiration, i.e. inhalation, takes place between the start time and time T1, and expiration or exhalation takes place between times T1 and T2. The control system according to the invention regulates the volume flow up and down depending on the respiratory rate determined from the measured flow values.

[0076] In a further preferred embodiment of the invention, the oxygen flow is also controlled depending on the breathing phases - then all three curves have a similar shape.

[0077] Fig. 6 shows a schematic arrangement of a preferred embodiment of the ventilation system according to the invention.

[0078] The system has a gas source 13, which compresses one of the substances to be mixed, in this case the ambient air, and introduces it into the hose 10'. The second substance to be mixed, which in this case is oxygen, is introduced via a separate supply line 16 into the hose 10' at a conveniently positioned inlet point 4 located between the ends of the hose 10'. The oxygen is either drawn from a gas cylinder via a pressure reducer, as is usually the case, or supplied directly from a generator (neither are shown).

[0079] The supply of ambient air is detected by the volume flow sensor 14, preferably positioned at the beginning of the hose 10', and controlled by an electromechanically driven control valve 15, the flow opening of which can be adjusted.

[0080] In the hose 10', between its two ends, is positioned the inlet point 4 of the supply line 16, through which the oxygen is introduced. In this preferred embodiment of the invention, the supply line 16 for the oxygen supply also has a volume flow sensor 17 and an electromechanically driven control valve 18, which enable control of the volume flow of the oxygen.

[0081] The signals from the volume flow sensors 14 and 17 are fed to the controller 7, which evaluates them and outputs control values ​​calculated according to an algorithm for the electromechanically driven control valves 15 and 18, which are also connected to them. The controller 7 also displays measured values ​​and / or calculated values ​​on a display device 19 for control purposes. An input unit 20 is provided for the manual specification of setpoints for the oxygen concentration, the FiO2 value.

[0082] At the end of the tube 10' is an exhalation system 10'', which is usually implemented either as a diffusion filter or an opening. Immediately adjacent to this is a user interface 11, which in the present preferred embodiment is designed as a breathing mask. This user interface is connected to the respiratory organs of a patient 12 and ensures a comfortable and tolerable connection of the person to the ventilation system.

[0083] The method according to the invention is implemented by means of a program running in the controller 7, which program records the volumes of one or both substances to be mixed over time and space based on measured volume flow values, calculates therefrom the course of the FiO2 concentration in the hose 10', the exhalation system 10" and the user interface 11 according to an algorithm and displays it on the display device 19.

[0084] Fig. Figure 7 shows a compressed gas source (21) connected to a mixing device (24) via a pressure regulator (22) and a control valve (23). The mixing device (24) has a compressed gas inlet (25), at least one ambient air connection (26, 27), and an outlet (28).

[0085] The compressed gas source (21) can, for example, be designed as a liquid gas source, the pressure of which is adjusted by the pressure regulator (22) to a range of 2.7 to 6 bar. The control valve (23) can be designed as a proportional valve. The ambient air is advantageously supplied to the ambient air connections (26, 27) via an air filter (29).

[0086] The mixing device (24) according to Fig. 1 comprises two Venturi nozzles (30, 31), wherein the Venturi nozzle (30) provides a base flow stage for a lower load range and the Venturi nozzle (31) provides a full flow stage for an upper load range. In particular, it is intended to operate the Venturi nozzles (30, 31) in parallel relative to one another in the upper load range.

[0087] The Venturi nozzle (30) is designed as a fixed injector, to which the compressed gas is supplied as propellant via the compressed gas inlet (25). The ambient air is fed to the Venturi nozzle (30) via the ambient air connection (26). Due to the injector effect of the compressed gas flow flowing out of the Venturi nozzle (30), ambient air is entrained, mixed with the compressed gas in the area of ​​a mixing chamber (32), and then directed toward the outlet (28). In this process, pressure is rebuilt via a diffuser (32a).

[0088] The Venturi nozzle (31) is designed as a needle injector, wherein in the Fig. 1, a needle (33) closes the nozzle outlet (34). The needle (33) is held by a needle carrier (35) in which the needle (33) is movably guided in the direction of a needle longitudinal axis (16). A needle tip (37) projects from the nozzle outlet (34). A needle base (38) facing away from the needle tip (37) is fastened to a diaphragm (39) which is arranged in a diaphragm chamber (40). The diaphragm chamber (40) is connected to the compressed gas inlet (25) via a control channel (41). Furthermore, the diaphragm (39) is supported in the region of its surface facing away from the diaphragm chamber (40) by a counter-element (42) which is braced against a chamber housing (44) by a spring (43).

[0089] The force of the spring (43) is dimensioned and preset by means of an adjusting screw (43a) in such a way that, when the pressure at the compressed gas inlet (25) is at a lower pressure range, which is transmitted to the diaphragm chamber (40) via the control channel (41), the force of the spring (43) is sufficient to press the needle (33) sealingly into the nozzle outlet (34).

[0090] To support a compact design of the mixing device (24), a connecting channel (45) extends from the compressed gas inlet (25) past the needle carrier (15) to an inlet channel (46) of the Venturi nozzle (30). This allows a common compressed gas supply to both Venturi nozzles (30, 31).

[0091] Fig. Figure 8 shows the progression of a ventilation cycle with an inspiration phase and an expiration phase. Oxygen is administered during part of the expiration phase. The duration of the administration is indicated by the dashed line. It can be seen that oxygen administration begins immediately at the beginning of the inspiration phase and is terminated within the inspiration phase at a suitable time when the effectiveness of oxygen uptake by the patient decreases.

[0092] Fig. 9 shows a different view from the illustration in Fig. 8 modified oxygen dosage. Dosing begins here taking into account a lead time TX, which accounts for the transit time of the volume units assigned to the oxygen supply through the ventilation system to the area of ​​the application site.

[0093] Fig.Figure 10 shows an oxygen dosage that extends over the entire period of inspiration time.

Claims

[1] Device for providing a breathing gas mixture consisting of at least two gases, comprising a user interface (11) designed as a breathing mask, a hose (10') supplying at least one of the gases to be mixed or a gas mixture and connected to a gas source (13), an oxygen hose (16) supplying oxygen and connected to an oxygen source, means (10") designed as a venting system for discharging the exhaled air, a control valve (15, 18) regulating the volume flow of at least one of the gases to be mixed, and a controller (7), wherein the device has at least one detection of the volume flow or the gas composition of at least one of the gases or gas mixtures to be mixed, and the controller (7) processes the at least one detected volume flow value of the at least one gas or gas mixture to be mixed,and controls the volume flow of at least one of the gases or gas mixtures to be mixed, characterized by that the control (7) takes into account the breathing air expelled by the patient under a certain pressure, contrary to the breathing gas mixture supplied into the dead space of the breathing mask (11), and thus recognizes the respiratory rate and the breathing air requirement of the patient on the basis of the reduced volume flow(s) and the calculated volumes, and regulates the inflow of one or both gases to be mixed in accordance with the measured and determined values ​​and taking into account the exhaled air escaping from the ventilation system (10") into the environment, wherein the control (7) starts an oxygen dosage immediately at the beginning of an inspiration phase and ends it within the inspiration phase at a suitable time at which the effectiveness of oxygen uptake by the patient decreases. [2] Device according to claim 1, characterized bythat one of the gases to be mixed is a gas mixture. [3] Device according to claim 1 or 2, characterized by that one of the gases to be mixed is a gas mixture, preferably air. [4] Device according to claim 1, characterized by that the detection of the volume flow and / or mass flow extends to at least a second gas to be mixed or a gas mixture and the controller (7) also processes these measured values. [5] Device according to claim 1, characterized by that the oxygen hose (16) is laid inside the air supply hose (10'). [6] Device according to claim 1, characterized by that the oxygen hose (16) is laid outside the air supply hose (10'). [7] Device according to one of the preceding claims, characterized bythat the inlet point (4) of the oxygen into the air supply hose (10') is located between its connection to the user interface (11) and its connection to the gas source (13). [8] Device according to one of the preceding claims, characterized by that the controller (7) controls the volume flow and / or mass flow of at least one further gas to be mixed. [9] Device according to one of the preceding claims, characterized by that at least one of the gases or gas mixtures to be mixed is introduced into the associated hose (10', 16) with a constant volume flow and / or mass flow. [10] Device according to one of the preceding claims, characterized by that the oxygen source is a pressure vessel with pre-compressed oxygen (21). [11] Device according to one of the preceding claims, characterized by that the oxygen source (21) is an oxygen generator. [12] Device according to one of the preceding claims, characterized by that the volume flow and / or mass flow is detected by means of at least one flow measuring device (14, 17). [13] Device according to one of the preceding claims, characterized by that the control of the volume flow of at least one of the substances to be mixed is carried out by means of at least one electromechanically driven control valve (15, 18). [14] Device according to one of the preceding claims, characterized by that the controller (7) has an interface that receives incoming signals from one or more volume flow and / or mass flow sensors and outputs outgoing signals for one or more control valves (15, 18). [15] Device according to one of the preceding claims, characterized by that the control (7) has a display device (19). [16] Device according to one of the preceding claims, characterized bythat the controller (7) has an input device (20). [17] Device according to one of the preceding claims, characterized by that the user interface (11) is designed as a breathing mask or an endotracheal tube or a tracheostomy. [18] Device according to one of the preceding claims, characterized by that the gas source (1) is designed as a blower. [19] Device according to one of the preceding claims, characterized by that the gas source (1) is designed as a pre-compressed pressure vessel. [20] Method for determining the concentration of at least a portion of a gas mixture consisting of at least two gases with known concentrations of the respective ingredients, using the device according to claim 1, wherein at least one second gas is added at least temporarily in the region of a mixing point (2) to the volume flow and / or the mass flow of at least one first gas flowing through a transport line (10'), and a detection and / or specification of the volume flows and / or the mass flows of the gases to be mixed takes place, and a determination of the displaced volumes of the gases in the respective transport line (10', 16) takes place, wherein the determination of the mixed concentration in the region of the mixing point (2) takes place from the calculated concentrations of the displaced volumes and / or masses, characterized bythat the distribution of the concentration of at least one portion of a gas mixture is determined at at least two points along the transport line (10'). [21] Method according to claim 20, characterized by that the dimensions of the transport line (10') are known or determined. [22] Method according to claim 20 or 21, characterized by that one of the non-solid substances to be mixed, preferably gases or gas mixtures, is supplied with a constant volume flow and / or mass flow, and no recording of the volume flow and / or mass flow is carried out for this purpose. [23] Method according to one of claims 21 to 22, characterized by that one of the gases to be mixed is oxygen. [24] Method according to one of claims 21 to 23, characterized by that one of the gases to be mixed is air. [25] Method according to one of claims 21 to 24, characterized bythat the control of the volume flow and / or mass flow for oxygen is carried out. [26] Method according to one of claims 21 to 25, characterized by that the CO2 concentration is calculated in the area below the user interface (11). [27] Method according to one of claims 21 to 26, characterized by that the nitrogen concentration is calculated in the area below the user interface (11). [28] Method according to one of claims 21 to 27, characterized by that an alarm is triggered in the event of a deviation of the calculated gas concentration from the specified target value. [29] Method according to one of claims 21 to 28, characterized by that the breathing phases, in particular the inhalation and exhalation, of the patient (12) are recorded and the volume flow and / or mass flow of at least one of the gases or gas mixtures to be mixed is controlled as a function of the breathing phases. [30] Method according to claim 25, characterized by that the breathing phases are carried out by recording the volume flow and / or mass flow of at least one of the gases or gas mixtures to be mixed and evaluating the measurement results. [31] Method according to one of claims 21 to 30, characterized by that the concentration of at least a portion of a gas mixture is determined at the end of the transport line (10). [32] Method according to one of claims 21 to 31, characterized by that a comparison is carried out between the specified target value and the calculated actual value of the mixed concentration, and that the comparison result is used to control the volume flow and / or mass flow of at least one of the non-solid substances involved, preferably gases or mixtures.

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