Device and method for measuring respective concentrations of three gas components in gas sample

Abstract

The invention relates to a sensor device and a measuring method for measuring respective concentrations of three gas components of a gas sample (Gp). One gas component is a paramagnetic gas. The gas sample (Gp) is guided into a measuring chamber (2). A magnetic field having an oscillating magnetic field strength is applied to the measurement chamber (2). A thermal conductivity of the gas sample (Gp) and a magnetically modulated thermal conductivity of the gas sample in the measurement chamber (2) are measured. Three concentrations of the three gas components are determined, for which purpose the predefined densities of the three gas components and the measured thermal conductivity, the measured magnetically modulated thermal conductivity and the measured densities are used.

Description

Technical Field

[0001] The present invention relates to a sensor device and a measuring method for measuring the respective concentrations of three gas components of a gas sample. Background Art

[0002] The task of measuring the individual concentrations of a plurality of gas components in a gas sample occurs, for example, during artificial respiration of a patient. The ventilator delivers a respirable gas mixture to a patient-side coupling unit, for example to a breathing mask or a tube, wherein the patient-side coupling unit is connected to the patient. The respirable gas mixture contains oxygen and, in one embodiment, at least one anesthetic agent (anesthetic gas).

[0003] DE 10 2021 126 106 A1 describes a method and a device for measuring oxygen concentration and anesthetic agent concentration. A magnetic field with an oscillating magnetic field strength is generated in a measuring chamber. The thermal conductivity and the magnetically modulated thermal conductivity of the respirable gas mixture are measured. Utilization is made of the fact that oxygen is a paramagnetic gas. Summary of the invention

[0004] The object of the present invention is to provide a sensor device and a measuring method which are able to measure the individual concentrations of three gas components of a gas sample and to measure them with greater reliability than known sensor devices and measuring methods.

[0005] This object is achieved by a sensor device having the features of claim 1 and by a measuring method having the features of claim 6. Where appropriate, advantageous embodiments of the sensor device according to the invention are also advantageous embodiments of the measuring method according to the invention and vice versa.

[0006] The sensor device according to the invention and the measuring method according to the invention are capable of measuring the respective concentrations (respective fractions) of three different gas components of a gas sample. "Concentration" is preferably understood to mean the respective fraction in volume percent, the concentration can also be the fraction in weight percent, i.e. the quantitative fraction. The gas component of the gas sample is a paramagnetic gas, in particular oxygen.

[0007] Note: A paramagnetic gas has the property that the atoms or molecules of the gas have permanent magnetism (magnetic moment) and align themselves in a magnetic field.

[0008] The respective density and the respective thermal conductivity of each of the three gas components are predetermined in a form that can be evaluated by a computer. For example, the sensor device has at least temporary read access to a data memory in which the density and thermal conductivity are stored.

[0009] The sensor device comprises a measuring chamber, a thermal conductivity sensor and a density sensor. The measuring chamber is capable of accommodating a gas sample. The thermal conductivity sensor is capable of measuring the thermal conductivity of the gas sample in the measuring chamber. The density sensor is capable of measuring the density of the gas sample. The measuring method according to the present invention is performed by using such a sensor device and comprises the steps of measuring the thermal conductivity and the density of the gas sample.

[0010] Note: The expression that a sensor measures a physical variable means the following: the sensor directly measures the physical variable or at least one other physical variable, wherein the physical variable or each other physical variable is correlated with the physical variable to be measured. Therefore, the physical variable or each other physical variable is a measure for the physical variable to be measured.

[0011] The measuring method according to the invention further comprises the following steps, and the sensor device according to the invention is designed to perform the following steps:

[0012] - A gas sample is delivered or directed into a measurement chamber.

[0013] - A magnetic field with an oscillating magnetic field strength is applied to the measurement chamber.

[0014] - measuring the magnetically modulated thermal conductivity of a gas sample in said measurement chamber.

[0015] The "magnetically modulated thermal conductivity" of the gas sample is understood to mean that portion of the thermal conductivity which oscillates in a manner dependent on the magnetic field strength. This magnetically modulated thermal conductivity depends primarily, but usually not exclusively, on the concentration of paramagnetic gases in the gas sample. The thermal conductivity which the gas sample has in the measuring chamber can be measured as a measure for the (total) thermal conductivity of the gas sample. The same thermal conductivity sensor can measure both the thermal conductivity and the magnetically modulated thermal conductivity, i.e. provide two different signals which can be independent of each other. It is also possible to use two different thermal conductivity sensors.

[0016] The concentrations of these three gas components are determined by using the following information:

[0017] - the predetermined densities of the three gas components,

[0018] - the predetermined thermal conductivities of the three gas components,

[0019] - the measured thermal conductivity of the gas sample,

[0020] - the measured magnetically modulated thermal conductivity of the gas sample, and

[0021] - the measured density of the gas sample,

[0022] - optionally additionally the temperature of the gas sample,

[0023] - optionally additionally measuring the temperature in the chamber, and

[0024] Optionally, the pressure at which the gas sample is present is also included, preferably the pressure in the measuring chamber.

[0025] According to the invention, three different properties of the gas sample are measured, namely thermal conductivity, magnetically modulated thermal conductivity and density. Typically, these three properties of the gas sample depend on the desired concentrations of the three gas components in the gas sample, but do not depend on each other. In particular, these three properties typically vary independently of each other. With these three properties of the gas sample, which are independent of each other and determined by measurement and are therefore known, three unknowns, namely the three desired concentrations of the three gas components, can be determined.

[0026] The invention does not presuppose that the gas sample consists only of these three gas components. Instead, the gas sample may include at least one other gas component. To determine its concentration, in many cases use can be made of the fact that the sum of the concentrations of the gas components measured in volume percent or weight percent gives 100%.

[0027] In some applications, the concentration of paramagnetic gases is particularly required, wherein paramagnetic gases are in particular oxygen. Some known sensor devices and measuring methods are also able to measure the oxygen concentration in a gas sample, but have a relatively high, undesirable cross-sensitivity with respect to other components of the gas sample. Such cross-sensitivity can lead to incorrect measurement results and is therefore undesirable. On the other hand, the sensor device according to the invention and the measuring method according to the invention have a significantly lower cross-sensitivity with respect to other gas components in the gas sample and ideally have no cross-sensitivity at all.

[0028] Due to the invention, it is not necessary in many cases to provide a reference gas with a known composition and use it for the measurement during the measurement of the concentration of a gas component by the sensor device and the measuring method.

[0029] Electrochemical sensors have become well known. The chemical process carried out in an electrochemical sensor depends on the concentration of oxygen and / or other gas components in a gas sample. The detection parameter of the electrochemical sensor The sensor measures an electrical detection parameter which is correlated with the desired oxygen concentration. In some cases, a disadvantage of such electrochemical sensors is that they require chemicals which become depleted over time and therefore have to be replenished from time to time. In addition, the chemicals may change or evaporate due to environmental influences, in particular the heat of the surrounding environment. The present invention can be implemented without the need for chemicals and thus avoids these disadvantages.

[0030] In one application, the paramagnetic gas component is oxygen. In this application, the two other gas components whose concentrations are measured according to the invention are anesthetic agents (anesthetic gases) or carbon dioxide and argon. The rare gas argon is present in the ambient air in a known concentration. However, in many cases, the argon concentration in the gas sample is higher than the known argon concentration in the ambient air. This occurs in particular in applications in which the gas sample comes from a breathable gas mixture for artificial respiration of a patient. This gas mixture is produced using ambient air, but has a higher oxygen content than the ambient air. So-called concentrators are used to produce the gas mixture from the ambient air. If a concentrator is used to produce a gas mixture with a higher oxygen content than the ambient air, the produced gas mixture generally also has a higher concentration of argon than the ambient air. This higher concentration is measured in the application of the invention just described.

[0031] The sensor device is preferably capable of simultaneously measuring the thermal conductivity and the magnetically modulated thermal conductivity of the gas sample in the same measuring chamber. In one design, the sensor device comprises a heating element and is capable of heating the heating element, in particular by applying a voltage to the heating element and passing a current through a heating wire of the heating element. If the heating element is heated, it delivers thermal energy to the gas sample in the measuring chamber. The heating element preferably does not chemically react with the gas sample in the measuring chamber.

[0032] According to the invention, a magnetic field with an oscillating magnetic field strength is applied to the measuring chamber. The thermal conductivity and magnetically modulated thermal conductivity of the gas sample are measured in the measuring chamber. Preferably, an electrical detection parameter is measured. The electrical detection parameter is correlated with the thermal conductivity of the gas sample in the measuring chamber. Electrical filtering or electronic filtering is performed on the electrical detection parameter. This filtering provides two signals, namely an oscillating signal and an additional signal. The oscillating signal oscillates according to the oscillating magnetic field strength. Ideally, the temporal variation of the additional signal does not depend on the oscillating magnetic field strength. The oscillating signal is used as the measure for the magnetically modulated thermal conductivity or as a measure for the magnetically modulated thermal conductivity. Therefore, the oscillating signal is correlated with the concentration of paramagnetic gas in the gas sample. The additional signal is used as the measure for the thermal conductivity of the gas sample or as a measure for the thermal conductivity of the gas sample. It is correlated with the thermal conductivity of the gas sample.

[0033] In many cases, this design leads to a particularly compact sensor arrangement. In the same measuring chamber, with the aid of the same magnetic field generator and the same heated heating element, two mutually independent properties of the gas sample, namely the thermal conductivity and the magnetically modulated thermal conductivity, are measured.

[0034] There can be various designs for how to measure the density of a gas sample. In one design, a mechanical or electronic flexural oscillator (flexural resonator) is used. The flexural oscillator comprises an oscillating body. In the case of a mechanical flexural oscillator, the oscillating body is or comprises a movably mounted fluid guiding unit. A "fluid guiding unit" is understood to be a component that guides a fluid along a trajectory, wherein the trajectory is predetermined by the construction and arrangement of the component. Corrugated hoses, smooth hoses and tubes are examples of fluid guiding units. A fluid guiding unit does not necessarily include a conveying unit. In the case of an electronic flexural oscillator, the oscillating body is preferably a quartz oscillator.

[0035] The gas sample is guided through the fluid guide unit of the flexural oscillator or is guided past the quartz oscillator. The flexural oscillator is able to cause the oscillating body (fluid guide unit or quartz oscillator) to oscillate when a portion of the gas sample is located in the fluid guide unit or is guided past the oscillating body or around the oscillating body. The natural frequency of the oscillating oscillating body is measured. The measured natural frequency is correlated with the mass of the gas sample.

[0036] In the case of a mechanical flexural oscillator, the natural frequency is dependent on the mass of the filled fluid guiding unit. Typically, this mass is the sum of the mass of the empty fluid guiding unit and the desired mass of the gas sample in the fluid guiding unit. Due to the construction of the flexural oscillator, the mass of the empty fluid guiding unit is known and does not change during the measurement. The volume of the fluid guiding unit is also known by the construction and remains constant. The desired density of the gas sample can be derived from the measured natural frequency and the mass and volume of the empty fluid guiding unit.

[0037] The principle of such flexural oscillators has been known for a long time and reliable flexural oscillators are available for density measurement.

[0038] In one design, the concentration of at least one fourth gas component of the gas sample is directly measured. The corresponding concentration of the or each fourth gas component of the gas sample is used in the step of determining the corresponding concentrations of the three gas components. In many cases, this design increases the reliability of determining the three concentrations of the three gas components.

[0039] In one implementation of this design, the concentration of the or at least the fourth gas component is measured by a photoelectric sensor using the following known principle:

[0040] The radiation source emits electromagnetic radiation or sound or ultrasound into a measuring section or measuring chamber, and precisely in a sufficiently broadband manner. The gas sample flows through the measuring section or is located in the measuring chamber. The measuring chamber can be the just described measuring chamber with the described magnetic field strength or another spatially separated measuring section or measuring chamber.

[0041] - The electromagnetic radiation or the sound penetrates the measuring section or the measuring chamber and at least part of it hits the detector.

[0042] The gas sample in the measuring section or measuring chamber absorbs part of the radiation or sound, thereby reducing the intensity of the radiation or sound in a wavelength range.

[0043] - The detector measures the intensity of the incident radiation or incident sound. This intensity is correlated with the desired concentration of the fourth gas component.

[0044] - The detector generates a signal as a function of the measured intensity. The signal comprises information about the intensity and therefore also about the concentration of the fourth gas component.

[0045] Many gases have a characteristic absorption spectral profile, ie a characteristic dependence of the degree of absorption on the wavelength of the electromagnetic radiation or sound penetrating the gas.In general, the concentration of the fourth gas component can be measured independently of the desired concentrations of the three gas components.

[0046] According to the invention, three properties of the gas sample are measured to determine values ​​for three unknowns, wherein the three unknowns are three desired concentrations of three gas components in the gas sample. In one embodiment, three functional relationships, three distance measures and one target function are predefined. The sensor device according to the invention preferably has at least temporary read access to a data memory in which the target function, the distance measures and the functional relationships are stored in a computer-evaluable form.

[0047] The first functional relationship describes the thermal conductivity of the gas sample as a function of the three desired gas component concentrations. The second functional relationship describes the magnetically modulated thermal conductivity of the gas sample as a function of the three gas component concentrations. The third functional relationship describes the density of the gas sample as a function of the three gas component concentrations. All three functional relationships therefore depend on the three unknown and desired gas component concentrations.

[0048] The first distance metric describes a measure of the distance between the measured thermal conductivity for the gas sample and the thermal conductivity derived by means of the first functional relationship. The second distance metric describes a measure of the distance between the measured magnetically modulated thermal conductivity for the gas sample and the magnetically modulated thermal conductivity derived by means of the second functional relationship. The third distance metric describes a measure of the distance between the measured density for the gas sample and the density derived by means of the third functional relationship. Each distance metric is preferably the square of the respective difference, or the absolute value of the difference, or another function, the greater the absolute value of the difference, the greater the other function.

[0049] The objective function is an aggregation of the three distance metrics. The objective function is preferably a weighted average of the three distance metrics. The weighting factors, for example, compensate for the different magnitudes of the three properties of thermal conductivity, magnetically modulated thermal conductivity, and density. The weighting factors may also additionally or alternatively take into account different accuracy requirements for the desired gas component concentrations.

[0050] The three measured values ​​for the gas sample, i.e. the measured thermal conductivity, magnetically modulated thermal conductivity and density of the gas sample, are adopted into the objective function. After adoption, the objective function depends on three unknowns, i.e. on the three gas component concentrations to be sought. The objective function is numerically minimized. This means that different value triplets for the three gas component concentrations are adopted into the objective function sample by sample. Each value triplet assigns a value to each of the three concentrations. The value triplets or value triplets that lead to the minimum of the objective function provide the three gas component concentrations to be sought. Ideally, the value triplets that are minimized provide the zero value of the objective function. In practice, the distances between the measured properties and the properties predicted according to the functional relationship are generated respectively. Preferably, an iterative minimization method is applied. The objective function may have multiple minimum values.

[0051] In at least one functional relationship, the concentration of a fourth gas component may additionally appear. In one embodiment, the sensor directly measures the concentration of the fourth gas component, for example using the above-mentioned photoelectric measurement principle, wherein the photoelectric measurement principle includes a radiation source and a detector. In another embodiment, a standard value is predefined for the concentration of the fourth gas component. There may be another gas component, namely a fifth gas component, whose concentration is measured or for which a standard value is predefined.

[0052] The invention also relates to a breathing device and a breathing method for artificial respiration of a patient.

[0053] The breathing apparatus comprises

[0054] - Medical equipment, especially ventilators,

[0055] - Patient-side coupling unit,

[0056] - Breathing control equipment and

[0057] - A sensor device according to the invention.

[0058] The breathing method is performed by using such a breathing apparatus.

[0059] The patient is connected to the patient-side coupling unit or can be connected at least temporarily to the patient-side coupling unit. The patient-side coupling unit particularly comprises a breathing mask and / or a tube and / or a catheter. The breathing device can guide and / or convey a breathable gas mixture from the medical device to the patient-side coupling unit. The gas mixture contains oxygen and, in one embodiment, at least one anesthetic and / or a drug. A breathing circuit may have been established. The gas mixture exhaled by the patient flows back to the medical device in the breathing circuit.

[0060] The concentration of at least one gas component of the respirable gas mixture, in particular the concentration of oxygen, should be within a predeterminable nominal range. This nominal range may change over time. It is also possible to predetermine nominal ranges for at least two gas components.

[0061] The breathing apparatus is designed to perform the following steps, and the breathing method comprises the following steps:

[0062] A gas sample is branched off from the gas mixture supplied to the patient-side coupling unit.

[0063] - The branched gas sample is directed to the sensor device.

[0064] The sensor device measures at least the concentration of the or each gas component for which a target range is predefined in the branched-off gas sample and optionally the concentration of at least one further gas component.

[0065] The respiration control device performs regulation (closed-loop control) or also control (open-loop control). The regulation variable is the actual concentration of at least one gas component in the gas mixture that is fed to the patient-side coupling unit. The regulation goal (control gain) in the regulation is that the regulation variable, i.e. the actual gas component concentration, is within a predefined setpoint range. For the regulation, the respiration control device uses the gas component concentration in the branched gas sample, which concentration has been measured by the sensor device. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The present invention is described below using embodiments. In this case:

[0067] Figure 1 A breathing circuit for artificial respiration of a patient is schematically shown;

[0068] Figure 2 A first embodiment of a sensor capable of measuring the concentration of oxygen and another gas is schematically shown;

[0069] Figure 3 A second embodiment of such a sensor is schematically shown;

[0070] Figure 4 Shows Figure 3 The measuring unit of the sensor in;

[0071] Figure 5 Shows Figure 2 and Figure 3 An exemplary evaluation circuit for a sensor of;

[0072] Figure 6 A mechanical flexural oscillator for measuring the density of a gas sample is shown;

[0073] Fig. 7A and 7B An electronic flexural oscillator in the form of a quartz oscillator is shown, respectively, for measuring the density of a gas sample;

[0074] Figure 8 The magnetically modulated thermal conductivity λ of a gas mixture is shown as an example 2f as a function of oxygen concentration. DETAILED DESCRIPTION

[0075] In an embodiment, the sensor device according to the invention is used for artificial respiration of a patient. A respirable gas mixture containing oxygen and at least one anesthetic agent (anesthetic agent) is supplied to the patient. Thus, the patient is anesthetized or at least sedated.

[0076] Figure 1 Schematically, a respiration device 200 is shown with a schematically shown respirator 1, wherein the respiration device 200 is capable of artificially respirating a patient P. Only the face of the patient P is schematically shown. In the example shown, the respirator 1 maintains a respiration circuit 40. In the example shown, the respirator 1 is designed as an anesthesia machine, and the patient P is anesthetized or at least sedated.

[0077] In the breathing circuit 40, a breathable gas mixture Gg is delivered to the patient P. In an embodiment, the gas mixture Gg contains oxygen (O2), at least one anesthetic agent and optionally a carrier gas for the anesthetic agent, such as laughing gas (N2O) and optionally additionally contains drugs. An anesthetic agent dispenser (Narkosemitteldosierer) 31 produces a fluid flow 28 with an anesthetic agent and a carrier gas in vapor form. The fluid flow 28 is fed into the breathing circuit 40. In addition, a fluid flow 27 of fresh air or other fresh gas is fed at least temporarily. At least as long as there is no excessive overpressure in the breathing circuit 40, the gas mixture exhaled by the patient P will remain in the breathing circuit 40, so that no anesthetic agent enters the surrounding environment.

[0078] The gas mixture At exhaled by the patient P and flowing through the breathing circuit 40 inevitably contains carbon dioxide (CO2). The carbon dioxide absorber (CO2 absorber) 25a is capable of absorbing carbon dioxide from the breathing circuit 40. In addition, the breathable gas mixture Gg may contain other components that are also present in the ambient air, although their concentrations may be different from those in the ambient air.

[0079] The invention can also be used in applications where no breathing circuit is implemented. The gas mixture At exhaled by the patient P passes through the exhalation line 33 into the surrounding environment.

[0080] A patient-side coupling unit 21, shown only schematically, such as a mouthpiece or a breathing mask or a tube, connects the patient P to the breathing circuit 40. A hose near the patient connects the patient-side coupling unit 21 to the base part of the Y-piece 22. One leg of the Y-piece 22 is connected to an inspiration line 32 for inhalation (Inspiration), and the other leg is connected to an exhalation line 33 for exhalation (Expiration).

[0081] The fluid delivery unit 24a draws in gas and generates a permanent flow of a breathable gas mixture Gg, which flows via the inspiration line 32 to the Y-piece 22 and to the patient-side coupling unit 21 and thus to the patient P. The breathing circuit 40 is kept in motion by the fluid delivery unit 24a and optionally by the manually operable breathing bag 26. The fluid delivery unit 24a can be implemented in particular as a blower, a pump or a piston-cylinder unit.

[0082] Check valve (non-return valve) 23a allows airflow through the inspiratory line 32 to the Y-piece 22 and prevents airflow in the opposite direction. Check valve 23b allows airflow through the expiratory line 33 away from the Y-piece 22 and prevents airflow in the opposite direction.

[0083] In an embodiment, the fluid delivery unit 24a continuously delivers the gas mixture Gg. A controllable valve 24b, preferably a proportional valve, allows the flow of the gas mixture generated by the fluid delivery unit 24a to pass or completely or totally blocks the flow of the gas mixture, depending on its position, thereby contributing to the generation of individual ventilation strokes and setting the amplitude and frequency of these breathing strokes.

[0084] The PEEP valve 24 c (PEEP=“positive end-expiratory pressure”) also ensures that a sufficiently high air pressure is maintained in the lungs of the patient P even at the end of exhalation or when the breathing circuit 40 is briefly opened or interrupted. This reduces the risk of collapse of the lungs of the patient P due to underpressure.

[0085] A pressure relief valve 29 can reduce the overpressure in the breathing circuit 40 by allowing gas to escape from the breathing circuit 40 in the event of an overpressure. The released gas is preferably released into a supply line for anesthetic gas and reaches a preprocessor (not shown).

[0086] The signal processing breathing control unit 35, which is only schematically shown, receives the signals of an optional pressure sensor 58, which measures the air pressure P in the surroundings of the anesthesia machine 1 and thus in the surroundings of the breathing circuit 40, and the signals of an optional temperature sensor 39. amb The temperature sensor 39 measures the ambient temperature Temp amb In addition, the breathing control device 35 receives measurement values ​​from a pressure sensor 36 which measures the current pressure in the breathing circuit 40 , for example the breathing pressure (pressure in airway, P ) applied to the patient P. aw ), in one embodiment, as relative to the ambient pressure P amb The measuring position of the pressure sensor 36 can be in the inspiratory line 32 or in the Y-shaped piece 22 or on or near the Y-shaped piece 22 as shown in the figure. The measuring position of the pressure sensor 36 is preferably located on a hose close to the patient. The breathing control device 35 controls the fluid delivery unit 24a, the valve 24b, the anesthetic agent dispenser 31 and other components of the breathing circuit 40 to achieve the desired artificial respiration and anesthesia for the patient P.

[0087] It is generally desired that the gas mixture Gg delivered to the patient P meets certain predetermined properties. In particular, the concentrations of the components of the gas mixture Gg should be within a predetermined rated range. In particular, the proportion of pure oxygen (O2) should generally be within a predetermined rated range, for example between 40 Vol.% and 50 Vol.% or between 25 Vol.% and 30 Vol.%. In other words, the proportion of anesthetics should be within a predetermined range. The term "concentration" of the gas components in the gas mixture is used below. A synonymous term is "proportion".

[0088] For this purpose, a sample (hereinafter: gas sample Gp) is extracted (branched off) from the gas mixture Gg, At in the breathing circuit 40 by means of a gas sample fluid conducting unit in the form of an extraction hose 52, analyzed and fed back into the breathing circuit 40 via a discharge hose 56. The extraction hose 52 begins at a branching point 34 between the patient-side coupling unit 21 and the Y-piece 22. Since the branching point 34 is located at this point, the gas sample Gp contains a sample from the breathable gas mixture Gg or a sample from the exhaled gas mixture At, depending on the branching time point. That is, sometimes the gas mixture Gg from the inspiration line 22 and sometimes the gas mixture At for the exhalation line 33 enter the extraction hose 52. At the branching point 34, there is optionally a valve (not shown) which, in the closed position, separates the extraction hose 52 from the breathing circuit 40 sample and can be controlled by the breathing control device 35. When the valve is fully opened or released, the extraction hose 52 is in unrestricted fluid communication with the breathing circuit 40. The discharge hose 56 leads to the junction 37 upstream of the carbon dioxide absorber 25 a.

[0089] The extraction hose 52 conducts the gas sample Gp to the sensor device 50. The sensor device 50 is spatially remote from the patient-side coupling unit 21 and the lines 32 and 33 and preferably also belongs to the schematically illustrated respirator 1. Figure 1 2 shows a sensor device 50 for illustrating the exterior of the ventilator 1 .

[0090] In an embodiment, the sensor device 50 comprises a pump 55, which sucks the gas sample Gp out of the breathing circuit 40 and sucks it in through the extraction hose 52. The pump 55 preferably permanently generates a negative pressure on the side pointing to the extraction hose 52 and a permanent overpressure on the side pointing to the discharge hose 56. The pump 55 can generate a volume flow rate (Volumenfluss) which is preferably constant over time and is, for example, 200 ml / min. A condenser (Wasserfalle) 51 is arranged at the input end of the sensor device 50, wherein moisture is condensed and collected in the condenser 51. The water content in the gas sample Gp is ​​thereby reduced.

[0091] The sensor 54 is capable of generating signals, wherein these signals are correlated with the concentrations of CO2 and N2O measured in the extracted gas sample Gp, respectively. The sensor 54 preferably comprises an infrared measuring head, which makes full use of the dipole moment of the molecules in the gas sample Gp and quantitatively evaluates the absorption of the infrared active gas to determine the corresponding concentration. The sensor 54 preferably comprises a radiation source that emits electromagnetic radiation and a detector that measures the intensity of the incident electromagnetic radiation and generates a corresponding signal.

[0092] The sensor 53 is capable of generating a signal that is correlated in particular to the concentration of O2 or other paramagnetic components of the gas sample Gp. Figures 2 to 5 The sensor 53 is described in more detail.

[0093] The sensor device 50 further comprises a pressure sensor 57 which measures the pressure P of the gas sample Gp at the input of the sensor device 50. cell The pressure P cell Over time, because the pressure in the breathing circuit 40 oscillates and because the extraction hose 52 is in fluid communication with the breathing circuit 40 when there is no valve at the branch point 34 or as long as the optional valve at the branch point 34 is open. The branch point 34 is open. If the valve is missing or open, the pressure in the breathing circuit 40 propagates to the sensor device 50 at close to the speed of sound.

[0094] Density sensors 59, 60 measure the density of the gas sample Gp flowing through the sensor device 50. Figure 6 and Figures 7A to 7B The concentration sensors 59 and 60 are described below. Figure 1 In the example of FIG. 5 , density sensors 59, 60 are arranged in parallel with sensors 53, 54, 57. Sensors 53, 54, 57 may also be arranged in series with density sensors 59, 60, and the branched gas sample Gp flows through all four sensors.

[0095] Sensor device 50, water condenser 51, signal processing unit 30 and hoses 52 and 56 together belong to measuring system 100 which draws a gas sample Gp from breathing circuit 40, checks it and feeds it back into breathing circuit 40. Measuring system 100 belongs to breathing device 200.

[0096] Figure 2 A sensor 53 is shown by way of example, which is capable of measuring the respective concentrations of oxygen (O2) and other gases in a gas sample Gp. The sensor 53 makes use of the fact that oxygen is a paramagnetic gas, whereas each other gas present or possibly present in the gas sample Gp is ​​not paramagnetic.

[0097] The two pole shoes 6, 7 and the two excitation coils 4, 5 generate a magnetic field. Between the two pole shoes 6, 7 an air gap 3 is generated which serves as a measuring chamber 2. The measuring chamber 2 is delimited by the two pole shoes 6, 7 and by a wall 9. An inlet 10 and an outlet 11 are embedded in the wall 9.

[0098] The thermocouple 8 is fixed at two connection points 12 and 14 to two support wires 15, 16, wherein the two support wires 15, 16 pass through the lower pole shoe 7 and are in thermal contact with the lower pole shoe 7. The thermocouple 8 comprises two wires 17, 18, which are connected to each other at the connection point 13. A voltage source 20 applies an alternating voltage to the two support wires 15, 16 and thus to the thermocouple 8. As a result, the thermocouple 8 is heated to an operating temperature that is higher than the temperature of the gas sample Gp in the measuring chamber 2. The voltage U applied to the measuring resistor 19 is measured. This voltage U contains an alternating voltage component and a direct voltage component.

[0099] The current operating temperature of the thermocouple 8 is measured at the connection point 13. This temperature depends on the voltage U occurring between the support wires 15, 16 on the one hand and on the thermal conductivity λ of the gas sample Gp in the measuring chamber 2 on the other hand. Regulation (closed-loop control) is performed with the goal that the operating temperature of the thermocouple 8 is regulated to a constant value. Regulation variable ( ) is the time-varying voltage U applied by the voltage source 20 to the supporting wires 15, 16. Since the temperature of the thermocouple 8 is ideally kept the same, the electrical detection variable of the thermocouple 8 is correlated with the thermal conductivity λ of the gas sample Gp in the measuring chamber 2.

[0100] One implementation form for measuring the detection variable is as follows: the time-varying electric power delivered to the thermocouple 8 is measured as the detection variable. The two support wires 15 and 16 are electrically connected to each other via an electric measuring resistor 19. The voltage U dropped on the measuring resistor 19 is measured. In addition, the intensity of the current flowing through the thermocouple 8 is measured. As is well known, electric power depends on voltage and current intensity. The voltage U can also be used as the detection variable.

[0101] The voltage source 43 is connected to the excitation coil 5 via a power amplifier 42, and the other excitation coil 4 is connected to electrical ground. The voltage source 43 emits a sinusoidal voltage. This voltage generates a sinusoidally varying magnetic field in the measuring chamber 2. The thermocouple 8, which is heated to a constant temperature, releases a certain amount of heat to the gas sample Gp in the measuring chamber 2 per unit time. The amount of heat released per unit time is correlated with the measured electrical power supplied to the thermocouple 8. Because the field strength of the magnetic field in the measuring chamber 2 oscillates periodically, the amount of heat released per unit time also oscillates, assuming that a paramagnetic gas is present in the measuring chamber 2 as part of the gas sample Gp. The detection parameter is correlated with the thermal conductivity λ of the gas sample Gp. By using this detection parameter, a signal that oscillates according to the oscillation of the magnetic field, such as an AC voltage, and a non-oscillating or less oscillating signal, such as a DC voltage, is generated. The oscillating signal is correlated with the thermal conductivity of the paramagnetic part of the gas sample Gp, and therefore with the O2 concentration. This thermal conductivity is also called magnetically modulated thermal conductivity λ 2f The other signals are related to the (total) thermal conductivity λ of the entire gas sample Gp.

[0102] Figure 3 , Figure 4 and Figure 5 Other designs of sensors 53 are shown. Figure 2 The same meaning in . Figure 5 The circuit can also be used accordingly according to Figure 2 design plan.

[0103] The electromagnet 62 with the electric coil 63 generates a temporally varying, preferably oscillating, magnetic field in the air gap 3, see Figure 3 The gas sample Gp to be examined reaches the air gap 3. The temporal course of the intensity of the generated magnetic field is set by the control of the coil 63. The magnetic field strength preferably has a sinusoidal curve. A measuring unit 64 implemented as a chip, preferably as a semiconductor chip, is arranged in the air gap 3, wherein the semiconductor chip is produced, for example, by using doped silicon.

[0104] Figure 4 The measuring unit 64 is shown in detail. The measuring unit 64 comprises an electrically controllable thermal conductivity measuring element 65, an electrically controllable heating unit 66 and a membrane 67 in a frame 69. The gas sample Gp can reach the elements 65, 66 through holes in or around the membrane 67. The heating unit 66 can be an electrically conductive resistor structure deposited on the membrane 67 or can be designed as a heating wire. Two heating elements of the heating unit 66 are shown, which are electrically connected to each other via a connecting element 68. The thermal conductivity measuring element 65 and the heating unit 66 can also be designed as a one-piece element with a temperature-dependent resistance.

[0105] The heating unit 66 heats the measuring element 65 to an operating temperature, which is higher than the temperature of the gas sample Gp in the measuring chamber 2. The heated measuring element 65 measures the temperature at the measuring position 77. In the embodiment shown, the measuring element 65 measures the thermovoltage and utilizes the Seebeck effect. Assuming the premise that the gas sample Gp at the measuring position 77 contains a paramagnetic gas with a sufficiently high concentration, the thermal conductivity of the gas sample Gp at the measuring position 77 changes synchronously with the temporally varying magnetic field generated by the electromagnet 62. A higher thermal conductivity results in that the heat energy is better conducted away. This in turn results in a lower temperature, which in turn causes a lower thermovoltage.

[0106] Figure 5 An evaluation circuit with the following components is shown by way of example:

[0107] - an amplifier 70 connected as an impedance converter,

[0108] - a voltage divider 71 with a variable tap,

[0109] - a DC voltage source 72,

[0110] - a low pass filter 73, and

[0111] A high-pass filter 74 is connected in parallel with the low-pass filter 73 .

[0112] The heating unit 66 is connected to a DC voltage source 72 via an amplifier 70 and a voltage divider 71. The output signal of the thermal conductivity measuring element 65 is guided via a low-pass filter 73 and a high-pass filter 74. At the output of the high-pass filter 74 there is a signal 75 which oscillates according to the oscillation of the magnetic field. This signal 75 is related to the magnetically modulated thermal conductivity λ 2f The signal 76 is correlated with the thermal conductivity λ of the entire gas sample Gp and is therefore correlated with the concentration of paramagnetic gas in the gas sample Gp, for example with the concentration of oxygen. At the output of the low-pass filter 73 there is a signal 76 which does not oscillate at all or at least is not synchronized with the oscillations of the magnetic field. This signal 76 is correlated with the thermal conductivity λ of the entire gas sample Gp.

[0113] Since the magnetic field strength oscillates, the amount of heat transported per unit time consists of a superposition of a portion that remains constant over time and a portion that fluctuates periodically. The portion that fluctuates periodically is correlated with the thermal conductivity and, therefore, with the oxygen concentration in the measuring chamber 2. The constant portion, i.e., the portion that oscillates in a manner independent of the magnetic field strength, is correlated with the thermal conductivity of the overall gas sample Gp in the measuring chamber 2. The thermal conductivity of the oxygen in the gas sample Gp and the respective thermal conductivity of each other component contribute to the thermal conductivity λ of the gas sample Gp. Both portions are measured. The sensor 53 therefore provides two signals:

[0114] a signal which oscillates in a manner dependent on the magnetic field strength, here a periodically fluctuating signal, which is a measure for the concentration of oxygen or another paramagnetic gas in the measuring chamber 2 (proportion of the periodic fluctuations, AC voltage), and

[0115] A signal for the thermal conductivity λ of the gas sample Gp in the measuring chamber 2 , wherein the signal does not oscillate or at least oscillates independently of the magnetic field strength (constant proportion, DC voltage).

[0116] Optionally, the measured values ​​for the component concentrations and / or for the thermal conductivity λ are displayed on a display device 44, see Figure 2 .

[0117] According to the invention, the density of the gas sample Gp is ​​also measured. Figure 6 An embodiment of a density sensor 59 in the form of a mechanical flexural oscillator is schematically shown. Figures 7A to 7B An embodiment of an electronic flexural oscillator 60 implemented as a quartz oscillator is shown. In one design, the density sensors 59, 60 are connected in parallel with the sensor 53, which measures thermal conductivity and magnetically modulated thermal conductivity and is referred to above. Figures 2 to 5 The sensor 53 may be implemented as a chip, and the density sensor 60 may be mounted on the chip and supplied with voltage by the chip.

[0118] The density measurement principle described below has long been known, but not for the application described here. In the exemplary embodiment, the density sensors 59 , 60 measure the density p of the gas sample Gp flowing through the sensor device 50 .

[0119] Reference Figure 6 First, a mechanical flexure oscillator 59 is described. A gas sample Gp, whose density p is to be measured, is guided through a U-shaped tube 80 having two legs 80.1, 80.2. The tube 80 is located in a housing 83 and is made of a material that is chemically resistant to the components of the gas sample Gp, such as glass or steel. The two legs 80.1, 80.2 of the tube 80 form the spring element of the flexure oscillator. This principle is similar to that of a tuning fork. The two legs 80.1, 80.2 are clamped at a fastening point 81. Area B of the tube 80 can be in oscillation. This area B also has a U-shape, comprises a segment of each leg 80.1, 80.2 respectively and is delimited by a fastening point 81.

[0120] In one implementation, the tube 80 may be temporarily closed for measurement purposes. In another implementation, the gas sample Gp also flows through the tube 80 during the measurement.

[0121] The schematically shown actuator excites the flexural oscillator to produce undamped oscillations. In the embodiment shown, the actuator is realized by two converters 82.1, 82.2. Each converter 82.1, 82.2 comprises a coil 83.1, 83.2 and a magnet 84.1, 84.2, respectively. In one mode, an alternating voltage is applied to each converter 82.1, 82.2, which generates mechanical oscillations, and these mechanical oscillations are transmitted to the tube 80, and more preferably transmitted to the tube 80 via a mechanical connection between the magnets 84.1, 84.2 and the tube 80.

[0122] The two legs 80.1, 80.2 extend over a plane. The two directions of oscillation generated by the excitation are orthogonal in this plane. Region B of the tube 80 is set into oscillation. The actuator 84 is then closed. Region B then continues to oscillate, and more precisely, continues to oscillate at its natural frequency after the start-up phase.

[0123] The region B of the tube 80 and the portion of the gas sample Gp located inside this region B participate in the oscillation. The oscillating system has a mass which is the sum of the mass of the region B and the mass of the portion of the gas sample in the region B. The mass of the region B is predetermined by design and remains constant. The volume provided by the region B for the gas sample Gp also remains constant. In general, during the measurement, the mass of the portion of the gas sample Gp located in the region B can be considered constant. The density p sought is then proportional to the mass of this portion of the gas sample.

[0124] The two converters 82.1, 82.2 are then closed. From now on, the system just described oscillates with a natural frequency τ. This natural frequency τ depends on the mass of the system and is measured. In the embodiment shown, the two converters 82.1, 82.2 work in a different mode after being closed and convert the mechanical oscillations of the region B into an alternating voltage. The frequency of this alternating voltage is equal to the natural frequency τ of the region B. The amplifier 85 amplifies this alternating voltage. The evaluation unit 86 receives the signal of the amplifier 85 and provides the desired density p.

[0125] The desired density ρ is related to the measured natural frequency τ as follows:

[0126] (1)ρ=A ＊ T 2 -B.

[0127] A and B are two constants of the density sensor (flexural oscillator) 59. In a previous calibration, these two constants A and B are determined empirically, for example by regression analysis. For this purpose, at least two different gases with known and mutually different densities are sent through the density sensor 59 and the corresponding resulting natural frequencies are measured.

[0128] Figures 7A to 7B A flexure oscillator 60 in the form of a quartz oscillator is schematically shown. The quartz oscillator has the shape of a tuning fork with two legs 61.1 and 61.2. Fig. 7A The quartz oscillator is shown schematically. Electrodes are connected to the flexural oscillator 60 in such a way that two opposing fields appear in the x-direction. It is thereby forced to bend in the z-direction. Figure 7B The oscillations of the two legs 61 . 1 and 61 . 2 are shown, wherein the x-direction and the z-direction lie in the drawing plane. The forced frequency is caused by the feedback to be equal to the natural frequency τ.

[0129] Such a flexural oscillator 60 is described, for example, in Th. Voglhuber-Brunnmeier et al.: “Fluid Sensing Using Quartz Tuning Forks – Measurement Technology and Applications, Sensors, Vol. 19 (2019) No. 10”.

[0130] In one design scenario, the following relationship is used:

[0131] (2)

[0132] A, B and C are again device-specific constants which are determined in advance by calibration. Since three constants are to be determined, at least three different gases with known and mutually different densities are used for the calibration.

[0133] As already explained, the sensor device 50 is intended to measure the respective concentrations (portions) of oxygen and anesthetic agent (anesthetic gas) in the branched-off gas sample Gp, which are expressed in vol.%. Other components may be present in the gas sample Gp, which may falsify the measurement result without appropriate countermeasures. In particular, the rare gas argon (Ar) in the gas sample Gp may falsify the measurement result. It is known that the portion of argon in the ambient air is approximately 0.93%. However, the argon concentration in the gas sample Gp can be significantly higher than the argon concentration in the ambient air. This occurs in particular when the oxygen concentration in the breathing circuit 40 and therefore in the gas sample Gp is ​​higher than the oxygen concentration in the ambient air, and more precisely in particular when the gas mixture Gg is produced from the ambient air and the oxygen concentration is amplified by means of a so-called oxygen concentrator.

[0134] In some cases, another component or another sensor of the anesthesia machine 1 additionally uses the information about the measured argon concentration. For example, the measured argon concentration is compared with an upper limit. Once the upper limit for the argon concentration is reached, the breathing circuit 40 is flushed.

[0135] In an embodiment, the gas sample Gp contains n different components, including nitrogen (N2), pure oxygen (O2), carbon dioxide (CO2), anesthetic gas (A-Gas (A gas)), laughing gas (N2O), water (H2O) and argon (Ar). The density ρ (x i )(i=1,…,n) and their respective thermal conductivity λ(x i ) are known and predetermined. The sensor device 50 preferably has at least temporary read access to a data memory in which the densities and thermal conductivities are stored. The following table shows by way of example the respective densities and respective thermal conductivities of components that are present or may be present in the breathing circuit 40 and therefore in the gas sample Gp, wherein these densities and thermal conductivities relate to: a reference ambient temperature of 15° C. and a reference ambient pressure of 1 bar.

[0136]

[0137] Table 1: Thermal conductivity and density of various gas components

[0138] The gas components have different densities. It can be seen that the density of the anesthetic isoflurane mentioned as an example is several times greater than the other gas components.

[0139] As already stated, the optional pressure sensor 36 measures the pressure in the breathing circuit 40 and preferably provides the airway pressure P AW The optional pressure sensor 58 measures the pressure P in the surrounding environment. ambOptional temperature sensor 39 measures the ambient temperature Temp amb , and the optional pressure sensor 57 measures the pressure P of the gas sample Gp at the input of the sensor device 50 cell The values ​​listed in Table 1 relate to a specific reference ambient temperature and a specific reference ambient pressure. Optionally, the signal processing unit 30 uses the signals from the sensors 36, 58 and / or 39 to derive the actual ambient temperature Temp. amb and the actual ambient pressure P amb The actual thermal conductivity and actual density of the possible gas components in the case.

[0140] What is required is that each component x i (i=1,...,n) each concentration ξ(X i ), i.e. the share in Vol.-%.

[0141] In many cases, it applies with sufficient accuracy that the density ρ of a gas sample Gp is ​​the density ρ(x i ), which means:

[0142] (3)ρ=ξ(x1) ＊ ρ(x1)+…+ξ(x n ) ＊ ρ(x n )

[0143] Gas composition x1,…,x n The required concentration ξ(x1),…,ξ(x n ) acts as a weighting factor.

[0144] In addition, in the above, reference Figures 2 to 5 , shows a sensor 53 for measuring a detection variable that is correlated with the thermal conductivity λ of the gas sample Gp. Figure 2 In the example, this is the detection parameter of thermocouple 8. Figure 5 In the example of , the signal 76 is. In many cases, it applies with sufficient accuracy that the thermal conductivity λ of the gas sample Gp is ​​the individual thermal conductivities λ(x i ) is the weighted average of:

[0145] (4)λ=ξ(x1) ＊ λ(x1)+...+ξ(x n ) ＊ λ(x n ).

[0146] Gas composition x1,...,x n The required concentration ξ(x1),…,ξ(x n) acts as a weighting factor.

[0147] The following function dependencies are also available:

[0148] (5)

[0149] The factors G(i, k) (i=1, ..., n; k=1, ..., n) can be predetermined empirically.

[0150] The sensor 53 can also measure the thermal conductivity λ of the magnetic modulation periodic component of the gas sample Gp 2f , for example, by using Figure 2 The periodic proportion of the detection variable of the design or by means of Figure 5 The oscillation signal of the circuit in is 75. Since O2 is a paramagnetic gas, λ 2f It mainly depends on the O2 concentration ξ(O2). In general, the following functional dependence can be applied ( )f:

[0151] (6)λ 2f =f[ξ(O2),ξ(N2O),ξ(CO2),ξ(H2O),ξ(Ar),Temp amb , P cell ]

[0152] Predetermine the functional dependency f. Temp amb represents the ambient temperature, which is measured by the temperature sensor 39, for example. Usually, the temperature of the gas sample Gp is ​​similar to the ambient temperature Temp amb There is no significant difference. The O2 concentration is approximately linear. Pressure P cell For example, it is measured by sensor 57 .

[0153] Figure 8 Schematic diagram of the magnetically modulated thermal conductivity λ of a gas mixture 2f As a function of the O2 concentration ξ(O2). In this case, the gas mixture consists only of oxygen and N2O. The oxygen concentration ξ(O2) in the gas mixture in volume percent is plotted on the x-axis, and the magnetically modulated thermal conductivity λ 2f is plotted on the y-axis. It can be seen that the relationship λ 2f =λ 2f [ξ(O2)] is approximately linear, but not perfectly linear.

[0154] The sensor 54 measures the CO2 concentration ξ(CO2) and the N2O concentration ξ(N2O). The pressure sensor 57 measures the pressure P cell The capacitive sensor not shown measures the H2O concentration ξ(H2O), ie the water vapor concentration in the gas sample Gp. Figure 6 and Figures 7A to 7B The described density sensors 59 , 60 measure the density ρ of the gas sample Gp.

[0155] The CO2 concentration ξ(CO2), the N2O concentration ξ(N2O) and the water vapor concentration ξ(H2O) are measured directly. Therefore, three unknown components remain, namely the O2 concentration ξ(O2), the anesthetic agent concentration ξ(A-Gas) and the argon concentration ξ(Ar). In order to determine these three unknowns, three equations (3), (4) and (6) are used. In summary, the following system of equations is used, which has three unknowns, namely ξ(O2), ξ(A-Gas) and ξ(Ar) and three equations, namely (3), (4) and (6).

[0156] In one implementation form, three values ​​ξ(x1), ξ(x2) and ξ(x3) are calculated for the three unknowns ξ(O2), ξ(A-Gas) and ξ(Ar) in such a way that the objective function Z is given by

[0157]

[0158] is minimized. Here ρ meas represents the measured density, λ meas represents the measured thermal conductivity, and λ 2f，meas represents the measured magnetically modulated thermal conductivity. ρ[ξ(x1), ξ(x2), ξ(x3)] represents the density generated according to equation (3), λ[ξ(x1), ξ(x2), ξ(x3)] represents the thermal conductivity according to equation (4) or (5), and λ 2f [ξ(x1), ξ(x2), ξ(x3)] represents the magnetically modulated thermal conductivity according to equation (6). The three factors α1, α2, α3 are selected so that all three summands of the objective function Z have the same order of magnitude and / or meet different accuracy requirements for measuring the three concentrations ξ(x1), ξ(x2), ξ(x3). The sum of the three factors α1, α2, α3 gives 1.

[0159] Obviously, the sum of the gas component shares gives 1, so it applies:

[0160] (8)ξ(x1)+…+ξ(x n )=1.

[0161] The N2 concentration ξ(N2) can be derived with the aid of equation (8).

[0162] Reference numerals list

[0163]

[0164]

[0165]

[0166]

[0167]

Claims

1. A sensor device (50) for measuring the respective concentrations of three gas components of a gas sample (Gp), The three gas components each have a respective density and a respective thermal conductivity which are predetermined, wherein one of the three gas components (O2) is a paramagnetic gas, The sensor device (50) comprises - a measurement chamber (2) for receiving a gas sample (Gp), - a thermal conductivity sensor (53) and - density sensors (59, 60), wherein the thermal conductivity sensor (53) is designed to measure the thermal conductivity (λ) of the gas sample (Gp), The sensor device (50) is designed as - directing the gas sample (Gp) into the measurement chamber (2), - applying a magnetic field with an oscillating magnetic field strength to the measurement chamber (2), and - measuring the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) in the measuring chamber (2); 2f ), in, The magnetically modulated thermal conductivity (λ 2f ) is the portion of the thermal conductivity of the gas sample (Gp) that oscillates in a manner dependent on the magnetic field strength, wherein the density sensor (59, 60) is designed to measure the density (ρ) of the gas sample (Gp), and The sensor device (50) is designed as The concentrations of the three gas components were determined by using: - a predetermined density of the gas component, - a predetermined thermal conductivity of the gas component, - the measured thermal conductivity (λ) of the gas sample (Gp), - The measured magnetically modulated thermal conductivity (λ 2f ),and - The measured density (ρ) of the gas sample (Gp).

2. The sensor device (50) according to claim 1, It is characterized in that The sensor device (50) comprises a heating unit (8, 66), wherein the heating unit (8, 66) is designed to deliver thermal energy to the gas sample (Gp) in the measuring chamber (2), The sensor device (50) is designed as - measuring an electrical detection variable (U) correlated to the thermal conductivity (λ) of said gas sample (Gp), and - by filtering the electrical detection variable (U), an oscillating signal (75) oscillating in a manner dependent on the magnetic field strength and a further signal (76) whose own temporal course is independent of the oscillating magnetic field strength are derived, and The sensor device (50) is further designed to: - measuring the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) based on the oscillating signal (75) 2f ), in particular using the oscillating signal (75) as the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) 2f ),and - measuring the thermal conductivity (λ) of the gas sample (Gp) based on the further signal (76), in particular using the further signal (76) as thermal conductivity (λ).

3. The sensor device (50) according to any one of the preceding claims, Features The density sensor comprises a flexural oscillator (59, 60) having an oscillating body (80, 61.1, 61.2), wherein the sensor device (50) is designed to guide the gas sample (Gp) through or along the oscillating body (80, 61.1, 61.2), The flexural oscillator (59, 60) is designed as - putting the oscillating body (80, 61.1, 61.2) into oscillation, and - measuring the natural frequency of the oscillating oscillating body (80, 61.1, 61.2), and The sensor device (50) is designed to determine the density (ρ) of the gas sample (Gp) based on the measured natural frequency of the oscillating body (80, 61.1, 61.2).

4. A breathing device (200) for artificially respiring a patient (P), The breathing device (200) comprises: - medical equipment (1), in particular ventilators, - a patient-side coupling unit (21), - breathing control equipment (35), and - A sensor device (50) according to any one of the preceding claims The patient-side coupling unit (21) is connected to the patient (P) or can be connected to the patient (P) at least temporarily, The breathing device (200) is designed to convey a breathable gas mixture (Gg) from the medical device (1) to a patient-side coupling unit (21), wherein a setpoint range is predefined for the concentration [ξ(O2)] of the gas component (O2) in the gas mixture (Gg), wherein the gas component is preferably a paramagnetic gas, The breathing device (200) is designed to - branching off a gas sample (Gp) from the gas mixture (Gg) supplied to the patient-side coupling unit (21), and - directing the branched gas sample (Gp) to the sensor device (50), and The sensor device (50) is designed to measure an actual concentration [ξ(O2)] of the gas component (O2) for which a target range is predefined in a branched-off gas sample (Gp).

5. The breathing device (200) according to claim 4, It is characterized in that The breathing control device (35) is designed to - regulating the concentration [ξ(O2)] of the gas component (O2) for which a setpoint range is predefined in the gas mixture (Gg) supplied to the patient-side coupling unit (21), and - using the measured gas component concentration [ξ(O2)] for said regulation, and The control goal in the control is to keep the actual gas component concentration [ξ(O2)] in the gas mixture (Gg) within a predefined setpoint range.

6. A measurement method for measuring the respective concentrations of the three gas components of a gas sample (Gp), wherein a respective density and a respective thermal conductivity are predetermined for each of the three gas components, wherein one of the three gas components (O2) is a paramagnetic gas, and in, The measuring method comprises the following steps: - measuring the thermal conductivity of said gas sample (Gp), and - measuring the density of said gas sample (Gp), The measuring method further comprises the following steps: - directing the gas sample (Gp) into the measurement chamber (2), - applying a magnetic field with an oscillating magnetic field strength to the measurement chamber (2), and - measuring the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) in the measuring chamber (2) 2f ), The magnetically modulated thermal conductivity (λ 2f ) is the portion of the thermal conductivity of the gas sample (Gp) that oscillates in a manner dependent on the magnetic field strength, and Among other steps: The concentrations of the three gas components were determined by using: - a predetermined density of the gas component, - a predetermined thermal conductivity of the gas component, - the measured thermal conductivity (λ) of the gas sample (Gp), - The measured magnetically modulated thermal conductivity (λ 2f ),and - The measured density (ρ) of the gas sample (Gp).

7. The measuring method according to claim 6, It is characterized in that measuring the thermal conductivity of the gas sample (Gp) in the measurement chamber (2) as the thermal conductivity (λ), and The measuring method comprises the following further steps: - the heating unit (8, 66) is heated, - the heated heating unit (8, 66) delivers thermal energy to the gas sample (Gp) in the measuring chamber (2), - an electrical detection variable (U) of the heated heating unit (8, 66) is measured, wherein the electrical detection parameter (U) is correlated with the thermal conductivity (λ) of the gas sample (Gp), and - by filtering the electrical detection variable (U), an oscillating signal (75) oscillating in a manner dependent on the magnetic field strength and a further signal (76) whose own temporal course is independent of the oscillating magnetic field strength are derived, in, - measuring the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) based on the oscillating signal (75) 2f ), in particular using the oscillating signal (75) as the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) 2f ),and The thermal conductivity (λ) of the gas sample (Gp) is measured based on the further signal (76), in particular the further signal (76) is used as the thermal conductivity (λ).

8. The measuring method according to claim 6 or 7, It is characterized in that The measuring method comprises the following further steps: - guiding the gas sample (Gp) through or along the oscillating body (80, 61.1, 62.2) of the flexural oscillator (59, 60), - putting the oscillating body (80, 61.1, 62.2) into oscillation, and - measuring the natural frequency of the oscillating body (80, 61.1, 62.2), The density of the gas sample (Gp) is determined based on the measured natural frequency of the oscillating body (80, 61.1, 61.2).

9. The measuring method according to any one of claims 6 to 8, It is characterized in that the thermal conductivity, magnetically modulated thermal conductivity and / or density of the gas sample (Gp) additionally depends on the concentration of a fourth gas component, wherein the density of the fourth gas component is predetermined and The measuring method further comprises the following steps: - the concentration of the fourth gas component is measured or otherwise determined, and In the step of determining the respective concentrations of the three gas components, the measured concentration of the fourth gas component is additionally used.

10. The measuring method according to claim 9, It is characterized in that The step of measuring the concentration of the fourth gas component comprises the following steps: - a radiation source emits electromagnetic radiation or sound, - the emitted electromagnetic radiation or the emitted sound penetrates the gas sample (Gp) and hits a detector, - the detector measures the intensity of incident electromagnetic radiation or incident sound, and - the detector generates a signal as a function of the measured intensity, wherein the concentration of the fourth gas component is measured based on a signal generated by the detector, In particular, the signal generated by the detector is used as the concentration of the fourth gas component.

11. The measuring method according to any one of claims 6 to 10, It is characterized in that Given three functional relationships, three distance metrics and one objective function, wherein the first functional relationship describes the thermal conductivity (λ) of the gas sample (Gp) as a function of the concentrations of the three gas components, The second functional relationship converts the magnetically modulated thermal conductivity (λ) of the gas sample (Gp) into 2f ) is described as a function of the concentrations of the three gas components, The third functional relationship describes the density (ρ) of the gas sample (Gp) as a function of the concentrations of the three gas components, wherein the first distance measure describes a measure of the distance between the measured thermal conductivity (λ) for the gas sample (Gp) and the thermal conductivity derived by means of the first functional relationship, where the second distance metric describes the measured magnetically modulated thermal conductivity (λ) for the gas sample (Gp) 2f ) and the magnetically modulated thermal conductivity derived by means of the second functional relationship, wherein the third distance metric describes a measure of the distance between the measured density (ρ) for the gas sample (Gp) and the density derived by means of the third functional relationship, wherein the objective function is an aggregation of the three distance metrics, in particular a weighted average, and The measuring method further comprises the following steps: - For the thermal conductivity (λ), the magnetically modulated thermal conductivity (λ 2f ) and the three measured values ​​of the gas sample density (ρ) are adopted into the objective function, and - calculating a triplet of values ​​of the three gas component concentrations in such a way as to minimize the objective function.

12. The measuring method according to any one of claims 6 to 11, It is characterized in that The three gas components whose concentrations are measured in the branched gas sample (Gp) are oxygen (O2), anesthetic agent and argon.

13. The breathing method used for artificial respiration of the patient (P), The patient (P) is connected to the patient-side coupling unit (21) or is connected to the patient-side coupling unit (21), and in, The breathing method comprises the steps of automatically performing: - conveying a respirable gas mixture (Gg) from a medical device (1), in particular from a ventilator, to a patient-side coupling unit (21), - predetermining a setpoint range for the concentration [ξ(O2)] of the gas component (O2) in the gas mixture (Gg), - branching off a gas sample (Gp) from the gas mixture (Gg) which is fed to a patient-side coupling unit (21), - measuring the actual concentration [ξ(O2)] of the gas component (O2) for which a setpoint range is predefined, The measurement method according to any one of claims 6 to 12 is applied for the measurement of the actual gas component concentration [ξ(O2)], and The gas component for which the setpoint range is predefined is the gas component of the three gas components whose concentration is measured, preferably a parameter gas, wherein the actual concentration [ξ(O2)] of the gas component (O2) in the gas mixture (Gg) is preferably controlled with the following control target: the actual oxygen concentration lies within a predefined setpoint range, The measured actual gas component concentration [ξ(O 2 )] in the branched-off gas sample (Gp) is used for the regulation.

14. The breathing method according to claim 13, It is characterized in that The gas mixture (Gg) is generated by using ambient air, wherein, when generating the gas mixture (Gg), the oxygen concentration is increased, and The three gas components whose concentrations in the branched-off gas sample (Gp) are measured are oxygen (O2), anesthetic agent and argon.

15. The breathing method according to claim 13 or 14, It is characterized in that The gas mixture (Gg) is conveyed from the medical device (1) to the patient-side coupling unit (21) via a fluid guiding unit (32), and detecting the event that at least one gas component in the delivered gas mixture (Gg) is outside a setpoint range predefined for said gas component, The following step is triggered: flushing the fluid guiding unit (32).

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