DE102022109699A1 - Process, gas mixer and ventilator for mixing gases - Google Patents

Abstract

The invention relates to a method for mixing gases, with at least two gas components each flowing through a separate flow channel, in each of which there is at least one controllable valve, so that the flow of each gas component through the respectively assigned flow channel is dependent on the respective valve setting, and where the individual gas components mix with each other in the flow direction behind the valves according to predetermined proportions to form a gas mixture. According to the invention, the proportions of the individual gas components are regulated by recording the pressure measurements from two differential pressure sensors for each gas component for specific pressure ranges and calculating the flows of the individual gas components therefrom.

Description

The invention relates to a method for mixing gases, wherein a gas mixture is produced from at least two gas components in predetermined proportions.

Gas mixers are generally used for such processes.

Gas mixers are used in a variety of devices to mix different gases together. It is often important to mix the different gases with one another in predetermined ratios and/or to set the proportions of the respective gases in the gas mixture to predetermined values or to regulate them continuously.

For example, such gas mixers are used in medical devices, including in particular in ventilators and/or anesthesia devices. Anesthesia devices within the meaning of this document are devices that enable the anesthesia of a patient using inhalation anesthetics.

In ventilators, gas mixers are used, for example, to set a predetermined oxygen content in the breathing gas.

In anesthesia machines, which are often designed as a combined ventilation and anesthesia device, gas mixers are used, for example, to set predetermined levels of oxygen (O2), a carrier gas (e.g. air) and an anesthetic gas (e.g. N20) in the breathing gas.
With both the ventilator and the anesthesia machine, the fresh gas mixture generated in this way is usually delivered to a patient via a ventilation tube and a patient interface, such as a tube, a ventilation mask or a nasal cannula.

It is very important to adjust the proportions of the different gases in the gas mixture as accurately as possible.

Particularly for applications in the medical technology sector, it is extremely important to be able to adjust the proportions of gases in a gas mixture with high precision. This is particularly true for anesthesia machines, because an overdose of the anesthetic gas used and/or an undersupply of an anesthetized patient with oxygen can have extremely harmful effects on the patient's health.

Various gas mixers are known which, through their mechanical structure and/or with the help of electronic components, enable relatively precise adjustment of the proportions of different gases in a gas mixture.

For example, methods for mixing gases and gas mixers are known with which oxygen, air and an anesthetic gas can be mixed with one another in predetermined proportions, the gas mixer having a plurality of valves with different channel diameters for each of the three components of the gas mixture. These valves can then be controlled individually for each component of the gas mixture, so that certain valves are opened and other valves are closed for each gas component. Depending on the pressure applied to the respective component, the flow and thus also the proportion of the respective component in the gas mixture can be adjusted. The accuracy of the setting options for the proportions of the various gas components in the gas mixture depends on the number of available valves per component. A lot of valves are required to achieve high levels of accuracy, so that such gas mixers are relatively large and require a large number of different components.

In other known methods for mixing gases and gas mixers, proportional valves are used for the various gas components, which can be controlled electronically with a pulse width modulated control signal (PWM) in such a way that the degree of opening of the valve is based on the duty cycle (ratio “on” to “off”). in one period) of the PWM can be set. As a rule, one proportional valve per gas component is sufficient.
In both types of processes for mixing gases and gas mixers, the determination of the flow of the individual gas components in the gas mixer is necessary in order to determine the proportions of the components in the gas mixture. This is often achieved by measuring the pressure of the individual gas components at the gas mixer and calculating the flow (volume flow) from this.

The pressure of a gas component applied to the gas mixer varies with the degree of opening of the respective valve or, if applicable, the valves assigned to the respective gas component and the resulting flow of the respective gas component. Volume flows in a range from less than 1 l/min to around 10 l/min are common, which are accompanied by a correspondingly large pressure range. According to the prior art, pressure sensors are used to measure the pressure, which can be used over the entire working range of the expected pressures.

In order to achieve a sufficiently high measurement accuracy in the entire working range of the existing pressures, high-quality pressure sensors with a wide measuring range must be used, which are, however, very expensive and which may still have lower dynamics and thus measurement accuracy for particularly high or low pressures.

It is therefore an object of the invention to provide a method for mixing gases that enables high measurement accuracy of the pressure for each gas component at lower costs.

This object is achieved according to the invention by a process for mixing gases according to claim 1.

The features of a method according to the invention for mixing gases disclosed below are part of the invention both individually and in all executable combinations.

In a method according to the invention for mixing gases, at least two gas components are provided at a pressure from corresponding sources. These gas components are mixed with one another in such a way that the proportions of the gas components in the gas mixture correspond as closely as possible to predetermined values.

Each of the gas components flows through a separate flow channel, in which there is at least one controllable valve, so that the volume flow, or flow, of each gas component through the respectively assigned flow channel depends on the respective valve setting. In the direction of flow behind the valves, the flow channels of the individual gas components connect to form a single common flow channel for the gas mixture, in which the gas components mix with one another accordingly.

The gas mixture produced according to the method according to the invention can be used for various applications.

• - Messung des Differenzdrucks im Strömungskanal der jeweiligen Gaskomponente mit zwei Drucksensoren, wobei ein erster Drucksensor zur Messung geringer Drücke und ein zweiter Drucksensor zur Messung hoher Drücke ausgebildet ist
• - Übertragung der Druckmesswerte von den Drucksensoren an eine Steuereinheit
• - Auswahl des Druckmesswertes eines der beiden Sensoren anhand mindestens eines Kriteriums
• - Berechnung des Flusses der Gaskomponente aus dem ausgewählten Druckmesswert
• - Ansteuerung des mindestens einen der jeweiligen Gaskomponente zugeordneten Ventils zur Einstellung des Flusses der Gaskomponente durch dieses hindurch

The core process of the method according to the invention for mixing gases consists of the following process steps for each of the gas components of the gas mixture to be produced:

• - Measuring the differential pressure in the flow channel of the respective gas component with two pressure sensors, a first pressure sensor being designed to measure low pressures and a second pressure sensor being designed to measure high pressures
• - Transmission of the pressure measurements from the pressure sensors to a control unit
• - Selection of the pressure measurement value of one of the two sensors based on at least one criterion
• - Calculation of the flow of the gas component from the selected pressure reading
• - Controlling the at least one valve assigned to the respective gas component to adjust the flow of the gas component through it

The total flow of the gas mixture is further calculated from the sum of the flows of all gas components and the proportion of the respective gas component in the gas mixture is determined based on the ratio of the flow of a gas component to the total flow.

The proportion of the gas component in the gas mixture determined in this way is compared with a target value and the control of the at least one valve assigned to the respective gas components is adjusted or maintained accordingly.

In embodiments of the invention in which proportional valves are controlled, this is preferably done by adapting the on-off cycle of a PWM used to control the respective valve.

In embodiments of the method according to the invention, the method steps of the core process are carried out approximately every 50 ms in a continuous loop until the method is terminated.

In embodiments of the invention, the sensor measured values of the pressure sensors are queried every 5 ms. The pressure value used to calculate flow is generated by applying a filter (e.g. moving average) over 10 readings.

In advantageous embodiments of the invention, differential pressure sensors are used for pressure measurement, with the first pressure sensor for each gas component being a 100 mbar differential pressure sensor for low pressures (low pressure sensor), with which differential pressures in a range from 0 to 100 mbar can be measured, and a 1000 as the second pressure sensor mbar differential pressure sensor for high pressures (high pressure sensor), with which differential pressures in a range from 0 to 1000 mbar can be measured, is used.

Low pressures in the sense of this document lie in a range from 0 bar to approximately 100 mbar. High pressures in the sense of this document are in a range from approximately 100 mbar to approximately 1000 mbar.

The accuracy of the flows of the gas components that can be determined using the pressure measurements using a method according to the invention for mixing gases is at least 100 ml/min in embodiments of the invention for flows below 1 l/min, at least 50 ml/min in particularly preferred embodiments of the invention, and for Flows greater than or equal to 1 l/min in embodiments of the invention at least 15%, in particularly preferred embodiments of the invention at least 10%.

A sufficiently high measurement accuracy of the pressure sensors for the respective area is achieved by appropriately apportioning the pressures that occur with the flows of the gas components to the specialized pressure sensors. For example, the sensitivity of a sensor can be used as an indicator, which results from the ratio of the output value range (full scale) to the difference between the maximum and minimum measured values. The sensitivity of a 100 mbar pressure sensor in comparison to a 1000 mbar pressure sensor results, for example, for an output value range of 26214 (maximum output value minus the offset) to 262.14 values/mbar (100 mbar sensor) and 26.21 values/mbar (1000 mbar sensor) . The 100 mbar sensor is therefore 10 times more sensitive and therefore more accurate than the 1000 mbar sensor, but is not suitable for pressures above 100 mbar due to the limited measuring range.

The low differential pressures occur at low flows in a range of 100 ml/min to 2 l/min and the high differential pressures occur at large flows in a range of 2 l/min to 10 l/min.

Particular preference is given to using a closed-loop control algorithm in the method according to the invention to adjust the flows of the individual gas components and thus their proportions in the gas mixture.

In preferred embodiments of the invention, each gas component is assigned its own regulator, so that the flows of the individual gas components are regulated independently of one another.

• - Laden von Kalibrierungsdaten aus einem nicht-flüchtigen Speicher

When starting a method according to the invention, in preferred embodiments the system is first initialized. The following steps are carried out:

• - Loading calibration data from non-volatile memory

• - Bestimmung der Steigung der Übertragungsfunktion der Sensoren zwischen den Kalibrierungspunkten durch Berechnung des Verhältnisses der Änderung des Sensormesswertes (Druck) über einer Änderung des Flusses.
• - Laden des Schwellwertes zur Entscheidung der Verwendung der Sensormesswerte von Niedrigdruck- oder Hochdruck-Sensor. In einer bevorzugten Ausführungsform der Erfindung liegt dieser Schwellwert zwischen 1,6 und 2,8 l/min, in besonders bevorzugten Ausführungsformen bei 2 l/min bis 2,4 l/min, insbesondere bei etwa 2,2 l/min.
• - Vorzugsweise zusätzlich Laden eines Hysteresewertes aus dem Speicher.

Calibration data are in particular pressure measured values of the individual pressure sensors at certain volume flows of the gas components, for example the pressure measured values at a volume flow of 0 l/min, 0.3 l/min, 0.6 l/min, 1 l/min, 2 l/min, 5 l/min and 10 l/min, which together form a sensor-specific calibration curve or transfer function.

• - Determine the slope of the transfer function of the sensors between the calibration points by calculating the ratio of the change in sensor reading (pressure) over a change in flow.
• - Loading the threshold value to decide whether to use the sensor readings from low pressure or high pressure sensor. In a preferred embodiment of the invention, this threshold value is between 1.6 and 2.8 l/min, in particularly preferred embodiments it is 2 l/min to 2.4 l/min, in particular approximately 2.2 l/min.
• - Preferably also loading a hysteresis value from the memory.

Using hysteresis when deciding which sensor to read prevents oscillation between sensors in pressure readings around the threshold. In an advantageous embodiment of the invention, the hysteresis value is approximately 0.2 l/min, so that with a threshold value of 2.2 l/min, for example, the system only switches to the low-pressure sensor as soon as the volume flow falls below 2 l/min.

After the initialization, the gas mixing process as such is started.

First, an initial setting of the proportions of the gas components in the gas mixture is loaded or queried from a memory or based on user input.

The valves assigned to the gas components are then activated with initial values so that they are fully or partially opened or closed in a predetermined manner.

In a preferred embodiment, the initial control of the valves takes place by determining the intervals of the calibration curve in which the target flows fall and setting the initial default value of the flow of the gas components to the upper limit of the respective interval. This means that faster convergence to the actual target value can be achieved in the subsequent control. In preferred embodiments of the invention, the same procedure is also used when specifying changes to the shares of the Gaskom components on the gas mixture are implemented, for example, through user input during ongoing operation.

In advantageous embodiments of the invention, the control configurations of the valves of the gas components (e.g. on-off cycle of a PWM) required for setting a desired initial flow (e.g. on-off cycle of a PWM) are at least to the upper limits of the gas components provided by corresponding sources at a normally expected pressure Intervals of the calibration curve of the sensors are available and are retrieved and used for the initial control of the valves.

The control loop and thus the core process of the method already described above is then started.

First, the flows of the individual gas components as well as the total flow of the gas mixture are determined from the flows of all gas components.

• - Bestimmung des Intervalls zwischen den Kalibrierungspunkten der Kalibrierungskurve des jeweiligen Sensors, in das der Druckmesswert fällt
• - Abziehen des Druckwertes des unteren Kalibrierungspunktes des Intervalls vom Messwert
• - Teilung des Zwischenergebnisses durch die Steigung der Kalibrierungskurve im Intervall
• - Addition des Volumenstromes der unteren Grenze des Intervalls

The calculation of the flow of a gas component from a pressure measurement value is carried out in preferred embodiments of the invention by the following steps:

• - Determination of the interval between the calibration points of the calibration curve of the respective sensor in which the pressure measurement value falls
• - Subtracting the pressure value of the lower calibration point of the interval from the measured value
• - Division of the intermediate result by the slope of the calibration curve in the interval
• - Addition of the volume flow of the lower limit of the interval

To determine the control requirement (error), the target flows of the gas components are determined based on the predetermined proportions of the gas components in the gas mixture and, for each gas component, the corresponding control of the at least one assigned valve to adjust the flow.

• - Prüfung auf Hardwarefehler z.B. Sensorfehler und entsprechende Ausgabe von Alarmen und/oder Wechsel in einen sicheren Betriebsmodus
• - Prüfung, ob ein neuer Vorgabewert bezüglich des Anteils einer Gaskomponente an der Gasmischung vorliegt, z.B. aufgrund einer Nutzereingabe. Dies ist insbesondere bei dynamischen Ausführungsformen des Verfahrens zur Mischung von Gasen erforderlich, bei denen Parameter im laufenden Betrieb geändert werden können.
• - Prüfung, ob zusätzliche Vorgaben bezüglich zumindest einer Gaskomponente eingehalten werden, z.B. Einhaltung vorbestimmter Grenzen bezüglich einzelner Gaskomponenten, darunter Mindest- und/oder Höchstgehalte von Gaskomponenten am Gasgemisch und/oder Mindest- und/oder Höchstflüsse einzelner Gaskomponenten z.B. Mindestgehalt O2 im Gasgemisch mindestens 25% und/oder Fluss des Trägergases beträgt mindestens 250 ml/min. In Ausführungsformen der Erfindung können diese Grenzen auch an Nutzereingaben oder Betriebsmodi gekoppelt sein und werden dementsprechend laufend aktualisiert.

Additional method steps carried out partially or completely in embodiments of the method according to the invention:

• - Checking for hardware errors e.g. sensor errors and corresponding output of alarms and/or switching to a safe operating mode
• - Check whether there is a new default value regarding the proportion of a gas component in the gas mixture, for example based on user input. This is particularly necessary in dynamic embodiments of the process for mixing gases in which parameters can be changed during ongoing operation.
• - Check whether additional specifications regarding at least one gas component are adhered to, e.g. compliance with predetermined limits regarding individual gas components, including minimum and/or maximum contents of gas components in the gas mixture and/or minimum and/or maximum flows of individual gas components, e.g. minimum O2 content in the gas mixture of at least 25 % and/or flow of the carrier gas is at least 250 ml/min. In embodiments of the invention, these limits can also be linked to user input or operating modes and are accordingly continuously updated.

As a consequence of violating such a limit value, the gas mixture is stopped completely or partially in embodiments of the invention, for example by closing all valves or closing the at least one valve assigned to a gas component (in particular closing the at least one valve assigned to an anesthetic gas as a gas component), so that, depending on the respective application, a safe operating mode is guaranteed and/or an alarm is issued. For example, the above-mentioned O2 content of the gas mixture is checked. If the specified minimum content (e.g. 25%) is undershot over a certain number of measurements (e.g. 200 measurements corresponding to around 10 seconds), an alarm is issued. In the case of a predetermined maximum value of the flow of a gas component, for example if a gas component is to be reduced to a proportion of 0% of the gas mixture, i.e. switched off, a possible leak can be detected by monitoring the flow of this gas component and, for example, an alarm can be issued.

In a preferred embodiment of a method according to the invention for mixing gases, a gas mixer for mixing at least two gas components with one another to form a gas mixture has at least one adjustable valve per gas component, at least two differential pressure sensors per gas component, with a first sensor in each case acting as a low-pressure sensor and a second sensor is designed as a high-pressure sensor, and a control unit with which the valves can be controlled according to predetermined flows of the gas components based on the recorded pressure measurement values is used.

In embodiments of the invention, the control unit used has an FPGA and an MCU, with the FPGA retrieving the pressure measurement values from the sensors, the MCU retrieving these pressure measurement values from the FPGA and using them in the control algorithm to determine the parameters for controlling the valves, sending the corresponding information to the FPGA is transmitted, which then controls the valves accordingly.

In a preferred embodiment of the invention, the method for mixing gases is designed to mix three gas components to form a gas mixture.

A gas mixer according to the invention is designed to mix at least two gas components into a gas mixture according to the method according to the invention and has at least one adjustable valve per gas component, at least two differential pressure sensors per gas component and a control unit with which the valves correspond to predetermined flows of the gas components based on the detected Pressure measurement values can be controlled and is further characterized in particular by the fact that a first sensor is designed as a low-pressure sensor and a second sensor is designed as a high-pressure sensor.

A ventilator or anesthesia device according to the invention is set up and designed to mix at least two gas components to form a gas mixture, the gas mixer having at least one adjustable valve per gas component, at least one differential pressure sensor per gas component and a control unit with which the valves are based on predetermined flows of the gas components can be controlled based on the recorded pressure measurement values, characterized in that a first sensor is designed as a low-pressure sensor and a second sensor is designed as a high-pressure sensor.

A ventilator or anesthesia device according to the invention is set up and designed for mixing gases according to one of the preceding claims, wherein at least two gas components flow through a separate flow channel in which there is at least one controllable valve, so that the flow of each gas component through the respectively assigned Flow channel is dependent on the respective valve setting, and the individual gas components mix with each other in the flow direction behind the valves according to predetermined proportions to form a gas mixture, with the regulation of the proportions of the individual gas components by recording the pressure measured values from two differential pressure sensors

• 1: Ein Ablaufdiagramm einer Ausführungsform eines erfindungsgemäßen Verfahrens zum Mischen von Gasen und 2: Ein Diagramm des in einem erfindungsgemäßen Verfahren zur Mischung von Gasen implementierten Regelkreises.

In the figures explained below, the method according to the invention is illustrated by way of example using an embodiment. Show it:

• 1 : A flow chart of an embodiment of a method according to the invention for mixing gases and 2 : A diagram of the control loop implemented in a method according to the invention for mixing gases.

In 1 a flowchart of an embodiment of a method according to the invention for mixing gases is shown.

The first step is initialization.

A timer is then set to 50 ms, which counts down from this start value.

The system is then checked for errors and an alarm is issued if necessary.

In the following process step, new user input (e.g. proportions of gas components in the gas mixture) is checked. If new user input is available, the corresponding target flows of the gas components are calculated from this.

The gas mixture will then be started, provided a corresponding entry has been made. Otherwise, the timer is read and the process is restarted at the step of setting the timer to 50 ms.

Once the mixing of the gas components has been started, the valves are activated according to an initial setting and opened accordingly.

In the present example, two of the gas components are O2 and N2O and the next step is to check whether a minimum value of the O2 content in the gas mixture is maintained.
If the minimum proportion of O2 in the gas mixture is not reached, the valve assigned to the gas component N2O is closed.

If the O2 content is above the limit value, the corresponding flows are calculated from the recorded pressure measurements and the control of the valves is adjusted accordingly.
The flows of the gas components are then checked to see whether they are within specified specifications. If this is not the case, an alarm is issued.

It is then checked whether the gas components (no flow) are inactive by completely closing the respective valves There is essentially no flow. If this is not the case, an alarm is issued.

It will then be checked whether there are any system errors. If this is the case, the gas mixing is stopped by closing all valves.

The next step asks whether the gas mixing should be ended by user input. If this is the case, the valves are closed.

Otherwise, the timer is read out continuously and after the timer has expired, the process is restarted with the step of setting the timer to 50 ms. In the loop runs following the first run, no initial values are used to control the valves or to specify target values, but rather the values obtained from the previous run are used.

2 shows a diagram of the control loop implemented in a method according to the invention for mixing gases.

The reference variable of the control loop is given by the initial values or the specifications for the flow of a gas component generated by user input. By comparing it with the flow calculated from the recorded measured values, the error is determined and the valve as a control element is activated accordingly in accordance with the control by the controller (control unit). By adjusting the valve accordingly, a flow of the respective gas component is established in the process. The differential pressure is then measured as a process variable and the current flow is calculated from this.

The following applies to all embodiments: When using ventilators, safe operation of these is of particular importance, since disruptions can have a significantly detrimental effect on the health of a patient being treated with such a device. For example, if a ventilator designed as a ventilator is used to ventilate a patient, it is imperative to supply the patient with fresh gas that has a certain minimum oxygen content (02). Another example is the use of an anesthesia machine to anesthetize a patient. In addition to a minimum O2 content in the fresh gas mixture, a specification regarding the proportion of anesthetic gas in the fresh gas mixture must also be adhered to. Examples of anesthetic gases are argon, helium, nitrous oxide, chloroform, isoflurane, sevoflurane, desflurane, halothane, enflurane, xenon, carbon dioxide.

It should be noted that the features listed individually in the claims can be combined with one another in any technically sensible manner and show further refinements of the invention. The description additionally characterizes and specifies the invention, particularly in connection with the figures.

It should also be noted that a conjunction “and/or” used here between two features and linking them together must always be interpreted in such a way that in a first embodiment of the subject matter according to the invention only the first feature can be present, in a second embodiment only the second feature can be present and in a third embodiment both the first and the second feature can be present.

A ventilator is any device that supports a user or patient in natural breathing, provides ventilation for the user or living being (e.g. patient and/or newborn and/or premature infant) and/or is used for respiratory therapy and/or otherwise influences the breathing of the user or patient or is used for anesthesia. These include, for example, but are not limited to, CPAP and BiPAP devices, anesthesia or anesthesia devices, respiratory therapy devices, (clinical, out-of-hospital or emergency) ventilators, high-flow therapy devices and cough machines. Ventilators can also be understood as diagnostic devices for ventilation. Diagnostic devices can generally be used to record medical and/or respiratory parameters of a living being. This also includes devices that can record and optionally process medical parameters of patients in combination with breathing or only relating to breathing.

Unless explicitly described otherwise, a patient interface can be understood to mean any peripheral device that is intended for the interaction, in particular for therapy or diagnostic purposes, of the measuring device with a living being. In particular, a patient interface can be understood as a mask of a ventilator or a mask connected to the ventilator. This mask can be a full-face mask, i.e. that encloses the nose and mouth, or a nasal mask, i.e. a mask that only encloses the nose. Tracheal tubes or cannulas and so-called nasal cannulas can also be used as masks or patient interfaces. In some cases, the patient interface can also be a simple mouthpiece, for example a tube, through which the living being at least exhales and/or inhales.

Claims (17)

Method for mixing gases, wherein at least two gas components flow through a separate flow channel, in each of which there is at least one controllable valve, so that the flow of each gas component through the respectively assigned flow channel depends on the respective valve setting, and wherein the individual gas components Mix together in the flow direction behind the valves according to predetermined proportions to form a gas mixture, comprising the following process steps: - Measuring the differential pressure in the flow channel of the respective gas component with two pressure sensors, a first pressure sensor being designed to measure low pressures and a second pressure sensor being designed to measure high pressures, - Transmission of the pressure measured values from the pressure sensors to a control unit, - Selection of the pressure measurement value of one of the two sensors based on at least one criterion, - Calculation of the flow of the gas component from the selected pressure reading, - Controlling the at least one valve assigned to the respective gas component to adjust the flow of the gas component through it. Process for mixing gases according to Patent claim 1 , characterized in that a 100 mbar differential pressure sensor is used as the first pressure sensor of a gas component and a 1000 mbar differential pressure sensor is used as the second pressure sensor of a gas component. Method for mixing gases according to one of the preceding claims, characterized in that a calibration is carried out - in which calibration data is loaded from a non-volatile memory, the calibration data being pressure measured values of the individual pressure sensors at certain volume flows of the gas components, for example the pressure measured values at a Volume flows of 0 l/min, 0.3 l/min, 0.6 l/min, 1 l/min, 2 l/min, 5 l/min and 10 l/min, which together form a sensor-specific calibration curve or transfer function form, - a determination of the slope of the transfer function of the sensors between the calibration points (intervals) is carried out by calculating the ratio of the change in the sensor reading (pressure) over a change in the flow, - and loading the threshold value for deciding to use the sensor readings of low pressure or High pressure sensor. In a preferred embodiment of the invention, this threshold value is between 1.6 and 2.8 l/min, in particularly preferred embodiments it is 2 l/min to 2.4 l/min, in particular approximately 2.2 l/min. Process for mixing gases according to Claim 3 , characterized in that the flow is calculated according to the following steps: - determining the interval between the calibration points of the calibration curve of the respective sensor in which the pressure measurement value falls, - subtracting the pressure value of the lower calibration point of the interval from the measurement value, - dividing the intermediate result by the slope of the calibration curve in the interval, - addition of the volume flow of the lower limit of the interval. Method for mixing gases according to one of the preceding claims, characterized in that a first criterion for deciding between the measured values of the pressure sensors is a threshold value. Process for mixing gases according to Claim 5 , characterized in that the threshold value is in a range of 1.6 to 2.8 l/min. Process for mixing gases according to one of Claims 5 and 6 , characterized in that a second criterion for deciding between the measured values of the pressure sensors is a hysteresis, whereby the value of the hysteresis must also be undercut before a change from the second pressure sensor for high pressures to the first pressure sensor for low pressures if the threshold value falls below. Method for mixing gases according to one of the preceding claims, characterized in that the control of the flows of the individual gas components is a closed control loop. Method for mixing gases according to one of the preceding claims, characterized in that at least one additional specification for at least one of the gas components is continuously checked and that if a specification is violated, an alarm is issued and/or a change to a safe operating mode occurs. Method for mixing gases according to one of the preceding claims, characterized in that the flows of the gas components for flows below 1 l/min with an accuracy of at least 100 ml/min and for flows greater than or equal to 1 l/min with an accuracy of at least 15 % can be determined. Method for mixing gases according to one of the preceding claims, characterized in that a gas mixer having at least one adjustable valve per gas component, at least two differential pressure sensors per gas component, with a first sensor as a low-pressure sensor and a second sensor as a high-pressure sensor. Sensor is formed, and a control unit with which the valves can be controlled according to predetermined flows of the gas components based on the recorded pressure measurements is used. Process for mixing gases according to Claim 11 , characterized in that the control unit has an FPGA and an MCU, whereby the FPGA retrieves the pressure measured values from the pressure sensors, the MCU retrieves these pressure measured values from the FPGA and uses the corresponding information in the control algorithm to determine the parameters for controlling the valves to the FPGA transmitted, which then controls the valves accordingly. Method for mixing gases according to one of the preceding claims, wherein at least two gas components flow through a separate flow channel in which there is at least one controllable valve, so that the flow of each gas component through the respectively assigned flow channel is dependent on the respective valve setting, and whereby the individual gas components mix with each other in the direction of flow behind the valves according to predetermined proportions to form a gas mixture, the proportions of the individual gas components being regulated by recording the pressure measurements from two differential pressure sensors per gas component for specific pressure ranges and the flows of the individual gas components being calculated therefrom he follows. Gas mixer for mixing at least two gas components to form a gas mixture according to the method according to one of Claims 1 until 13 , the gas mixer having at least one adjustable valve per gas component, at least two differential pressure sensors per gas component and a control unit with which the valves can be controlled in accordance with predetermined flows of the gas components based on the recorded pressure measurement values, characterized in that a first sensor is in each case a low-pressure sensor. Sensor and a second sensor is designed as a high-pressure sensor. Ventilator or anesthesia device comprising a gas mixer Claim 14 . Ventilator or anesthesia device set up and designed to mix at least two gas components into a gas mixture, the gas mixer having at least one adjustable valve per gas component, at least one differential pressure sensor per gas component and a control unit with which the valves correspond to predetermined flows of the gas components based on the detected Pressure measurement values can be controlled, characterized in that a first sensor is designed as a low-pressure sensor and a second sensor as a high-pressure sensor. Ventilator or anesthesia device set up and designed for mixing gases according to one of the preceding claims, wherein at least two gas components flow through a separate flow channel in which there is at least one controllable valve, so that the flow of each gas component through the respectively assigned flow channel of the depends on the respective valve setting, and the individual gas components mix with each other in the flow direction behind the valves according to predetermined proportions to form a gas mixture, the proportions of the individual gas components being regulated by recording the pressure measurements from two differential pressure sensors per gas component for specific pressure ranges and the calculation of the flows of the individual gas components.

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