Method and device for determining substance proportions of a fluid mixture of substances and medical device

Abstract

The invention relates to a method and a device for determining substance proportions of a fluid mixture of substances as well as a medical device. According to the invention, at least two different non-selective measuring devices or measuring methods are used to measure independent substance properties of a mixture of substances in order to determine the proportions of substances in the mixture of substances by solving a system of equations.

Description

[0001] Method and device for determining substance proportions of a fluid mixture and medical device

[0002] The invention relates to a method for determining substance proportions of a fluid mixture, in particular gases or liquids, using at least two sensors.

[0003] Furthermore, the invention relates to a device for determining substance proportions of a fluid mixture, in particular gases or liquids, wherein the device has at least two sensors for this purpose.

[0004] Furthermore, the invention relates to a medical device comprising such a device for determining substance proportions of a fluid mixture.

[0005] To analyze the composition of fluid (liquid or gaseous) mixtures, measurement methods are usually used that largely utilize selective properties to determine individual components of the mixture, such as spectroscopic or chemical measurement technologies. However, such selective measurement methods are often complex and / or slow. Therefore, a high-resolution, selective analysis of the complete composition of a mixture is usually not possible. In some applications, even the selective determination of a single desired component of the mixture is problematic.

[0006] Measurements of the composition of mixtures of substances by recording multiple measurement signals in relation to the mixture of substances are state of the art. However, a single material property is usually evaluated multiple times while varying an accompanying parameter and examined for component-specific characteristics. For example, in an absorption measurement, the light absorption of a gas / gas mixture is analyzed. The measurement wavelength is changed and the absorption at different wavelengths is measured. By scanning across a wavelength range, conclusions can be drawn about several gas concentrations or even the entire gas composition based on the absorption behavior at specific wavelengths. There are many similar methods that, as in this example, measure a specific material property (e.g., absorption) using a specific measurement method (e.g., absorption spectroscopy) using a varying parameter (e.g.,the wavelength) and thus measure the composition of a gas mixture.

[0007] These procedures are often very complex and expensive, and the equipment required for their implementation is large. Furthermore, mobile use of such equipment, for example, in a moving emergency vehicle, with its high shock and vibration loads, is often not possible.

[0008] Such methods and devices are also used in medical technology, for example in ventilation technology, where the composition of the respiratory gas is determined in particular. The rapid, selective measurement of, for example, oxygen (O2) currently requires complex, expensive measuring techniques that are also difficult to integrate into compact devices. In contrast to CO2 measurement, where, for example, a filter is placed in front of the sensor on the receiver side that only allows a wavelength relevant to CO2, this is not possible with O2 measurement. A corresponding characteristic absorption range does not exist for O2, so that optical O2 measurement can only be carried out with very finely tunable lasers. This procedure, however, is very expensive and complex. Breath-resolved measurement of oxygen concentration is important for good patient care, but has so far been difficult to implement with compact devices.The solution approach described here is intended to show that a combination of primarily non-selective measuring methods allows the determination of the gas composition and thus the determination of the oxygen concentration can still be made possible.

[0009] An object of the invention is to provide a device for determining substance proportions of a fluid mixture of substances, which at least partially eliminates the disadvantages of the prior art described above.

[0010] This object is achieved according to the invention by a device for determining the proportions of a fluid mixture of substances according to claim 1. A further object of the invention is to provide a medical device with which the above-described disadvantages of the prior art in determining the proportions of mixtures of substances are at least partially eliminated.

[0011] This object is achieved according to the invention by a medical device according to patent claim 11.

[0012] Furthermore, it is an object of the invention to provide a method for determining substance proportions of a fluid mixture of substances which at least partially eliminates the disadvantages of the prior art described above.

[0013] This object is achieved according to the invention by a method according to patent claim 13.

[0014] Advantageous embodiments of the invention are claimed in the dependent claims.

[0015] The features of a device for determining substance proportions of a fluid mixture, a medical device and a method for determining substance proportions of a fluid mixture disclosed below are part of the invention both individually and in all executable combinations.

[0016] The basic idea of ​​the invention is the combination of several non-selective measurement methods or measuring devices for determining the proportions of a fluid mixture. The higher speed of non-selective measurement methods allows for faster overall measurements to determine at least one component of a mixture.

[0017] Non-selective measuring methods or measuring devices are those methods or devices with which a specific substance proportion of a mixture of substances cannot be determined directly or not with the required accuracy or robustness and only on the basis of the measurement data obtained with this method or device, as is possible with selective measuring methods or measuring devices.

[0018] In embodiments of the invention, however, scanning is not primarily based on a single material property, but rather at least two different and independent material properties are measured and evaluated. Independent material properties are those properties of the respective substance or mixture of substances that do not influence each other. These include, for example, thermal conductivity, heat capacity, the speed of sound in the respective substance or mixture of substances, the molar mass, the dynamic viscosity, the permittivity, and the refractive index or the speed of light in the respective substance or mixture of substances, which can be used with known measurement methods for the non-selective determination of the material components of a mixture of substances.

[0019] By way of example, in embodiments of the invention, the following sensors can be used to measure these material properties.

[0020] Thermal conductivity and heat capacity are measured, for example, using a sensor comprising at least one heating element and a temperature sensor. If the fluid mixture is at rest, the temperature measurement at a known heater temperature can be used to determine the thermal conductivity of the fluid mixture after calibration of the sensor. If the heater temperature is modulated, the delay with which a temperature change can be detected at the temperature sensor is a measure of the thermal capacity of the fluid mixture. In principle, thermal conductivity and heat capacity can be measured with a suitable sensor device.

[0021] In embodiments of the invention, the device for determining the substance content of a fluid mixture comprises at least one thermal conductivity sensor and / or heat capacity sensor. In embodiments of the invention, this is embodied as an integrated sensor chip.

[0022] In embodiments of the invention, the speed of sound is measured using ultrasonic technology. Such sensors are already available on the market.

[0023] In embodiments of the invention, the device for determining substance proportions of a fluid mixture comprises at least one sound velocity sensor based on ultrasound technology.

[0024] The molar mass can be derived from the speed of sound. Measurement using other methods is very complex. In embodiments of the invention, the device for determining the proportions of a fluid mixture comprises at least one sensor for determining the molar mass based on the speed of sound.

[0025] Dynamic viscosity can be measured, for example, by the pressure drop in a thin tube in which laminar flow has been established. The pressure drop is directly proportional to dynamic viscosity.

[0026] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture has at least one sensor for determining the dynamic viscosity based on the determination of a pressure drop.

[0027] The permittivity of a mixture of substances can be measured using a plate capacitor through which the fluid mixture flows. The change in capacitance is also directly proportional to the permittivity. Among the gases measured in ventilation technology, water vapor is particularly important in this regard, as its density differs by more than a power of ten from that of other relevant gases.

[0028] In embodiments of the invention, the device for determining substance proportions of a fluid mixture comprises at least one permittivity sensor.

[0029] The refractive index or the speed of light of different gases differs very little, so that in corresponding embodiments of the invention interferometers are used as refractive index sensors or speed of light sensors.

[0030] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture comprises at least one refractive index sensor and / or a speed of light sensor comprising at least one interferometer.

[0031] If the composition of a mixture of substances with a number of X different substances is to be completely determined, at least X-1 independent non-selective measurements of different material properties are required in order to be able to solve the resulting system of equations completely and unambiguously.

[0032] In embodiments of the invention, use is made of the fact that in many applications only certain substance fractions of a substance mixture are of interest and / or that certain substances do not influence the substance properties of the substance mixture to be measured or influence them only to a small extent.

[0033] This allows the minimum required number of non-selective measurement methods / measurement devices for independent material properties to be reduced to a value less than or equal to X-1, where X is the number of relevant material components.

[0034] A device according to the invention for determining substance proportions of a fluid mixture of substances is designed to determine the proportion of at least one substance in a fluid mixture of substances.

[0035] A device according to the invention for determining substance proportions of a fluid substance mixture has at least two different non-selective measuring devices, each measuring a substance property of the substance mixture, wherein the substance properties measured by the measuring devices are different and independent of one another.

[0036] Furthermore, a device according to the invention for determining substance proportions of a fluid substance mixture has at least one evaluation unit for evaluating the measured values ​​of the at least two different substance properties recorded by the measuring devices and for determining at least one substance proportion in the substance mixture from the combination of the measured substance properties.

[0037] In advantageous embodiments of the invention with a number X of proportions to be determined in the fluid substance mixture, the device for determining substance proportions of a fluid substance mixture has at least X-1 non-selective measuring devices with which various independent substance properties of the substance mixture can be measured.

[0038] In embodiments of the invention, at least two of the non-selective measuring devices are designed to carry out the respective measurements simultaneously or at least partially overlapping in time.

[0039] In embodiments of the invention, all non-selective measuring devices are designed to carry out the respective measurements simultaneously or at least partially overlapping in time.

[0040] If the various sensors are arranged one after the other in the volume flow of the fluid mixture, a temporal offset in the measured values ​​occurs, since a certain volume reaches the individual sensors one after the other. With a known volume flow of the fluid mixture, the temporal offset can be compensated for in corresponding embodiments of the invention, so that the measured values ​​of all sensors can be synchronized. For this purpose, the device for determining the substance proportions of a fluid mixture comprises a volume flow sensor in preferred embodiments.

[0041] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture is designed to determine the proportion of O2 and / or CO2 in the substance mixture.

[0042] In embodiments of the invention, at least one measuring device of the device for determining substance proportions of a fluid substance mixture has at least one sensor for determining one of the substance properties heat conduction, heat capacity, speed of sound (e.g. ultrasonic sensor), molar mass, dynamic viscosity, permittivity or refractive index or speed of light.

[0043] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture additionally comprises at least one selective sensor for selectively determining at least one substance proportion in the substance mixture.

[0044] In embodiments of the invention, the at least one selective sensor is designed for NDIR absorption measurement to determine the CO2 content, as a lambda probe to determine the O2 content, as a paramagnetic sensor to determine the O2 content, as an optical sensor such as an optrode for measurement by means of fluorescence quenching (in particular a pO2 optrode), as an electrochemical gas sensor or as a humidity sensor (in particular by means of permittivity measurement).

[0045] In embodiments of the invention, it is known which substances the mixture of substances contains or which substances the mixture of substances contains that influence the material properties of the mixture of substances to a relevant extent.

[0046] In embodiments of the invention, the device for determining substance proportions of a fluid mixture is designed for the iterative determination of at least one substance property. This allows the measurement accuracy to be improved in corresponding embodiments. In embodiments of the invention, the device for determining substance proportions of a fluid mixture has more than X-1 non-selective measuring devices. This allows the robustness and / or accuracy of the measurement to be increased. Furthermore, in embodiments of the invention, a plausibility check and / or a check of the mixture for unknown substances with a relevant influence on the measurement(s) is implemented.

[0047] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture has an evaluation unit with which the substance proportion of at least one substance in the substance mixture can be determined by setting up a system of equations from the measured substance properties and the solution of the system of equations.

[0048] In embodiments of the invention, the system of equations to be solved can be linear or non-linear.

[0049] The system of equations to be established includes the measured material properties and their mathematical dependencies on the individual substances of the mixture, taking into account at least the relevant components of the mixture.

[0050] In embodiments of the invention, the evaluation unit is designed to analytically solve the system of equations.

[0051] In embodiments of the invention, the evaluation unit is designed to numerically solve the system of equations.

[0052] In embodiments of the invention, the evaluation unit is designed to iteratively solve the system of equations.

[0053] In embodiments of the invention, the evaluation unit is designed to evaluate the measurement data acquired by the measuring devices using at least one Kl system.

[0054] In embodiments of the invention, the evaluation unit is designed to evaluate the measurement data using a combination of analytical, numerical, iterative and / or AI-based methods.

[0055] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture has at least one compensation device with which, for example, the temperature, the pressure, the volume flow and / or the humidity of the substance mixture can be measured and can be used to compensate for at least one of the other measurements of the measurements carried out to determine the substance proportions.

[0056] In embodiments of the invention, the device for determining substance proportions of a fluid mixture is designed for use in a medical-technical application.

[0057] In embodiments of the invention, the device for determining substance proportions of a fluid substance mixture is designed to determine at least a gas proportion of respiratory gas during the ventilation of a patient.

[0058] A medical device according to the invention has at least one device according to the invention for determining substance proportions of a fluid substance mixture.

[0059] In embodiments of the invention, the medical device is designed as a ventilator, wherein the substance mixture is a gas mixture, namely respiratory gas.

[0060] In other embodiments of the invention, the medical device is designed for blood gas analysis.

[0061] In embodiments of the invention, the medical device is designed to use the determined substance proportions to adapt the control of a therapy module and / or an instruction module.

[0062] In embodiments of the invention, a therapy module is designed as the ventilation unit of a ventilator and the instruction module is designed in embodiments of the invention to output instructions to a human helper.

[0063] A method according to the invention for determining substance fractions of a fluid mixture of substances can be used to determine at least one substance fraction of a fluid mixture of substances.

[0064] A method according to the invention for determining the substance proportions of a fluid mixture comprises at least the following method steps:

[0065] Carrying out at least two different non-selective measurements, each measuring a material property of the mixture and the material properties measured with the different measurements being independent of each other,

[0066] Combination of the measured substance properties to determine the proportion of at least one substance in the mixture.

[0067] In embodiments of the method, for a number X of proportions to be determined in the fluid mixture, at least X-1 different non-selective measuring methods or measuring devices are used which measure different, mutually independent material properties of the mixture.

[0068] In embodiments of the method according to the invention, at least two of the non-selective measurements are carried out simultaneously or at least partially overlapping in time.

[0069] In embodiments of the method according to the invention, all non-selective measurements are carried out simultaneously or at least partially overlapping in time.

[0070] In embodiments of the method according to the invention, the proportion of O2 and / or CO2 in the mixture of substances is determined.

[0071] In embodiments of the method according to the invention, at least one of the material properties heat conduction, heat capacity, speed of sound (e.g. ultrasonic sensor), molar mass, dynamic viscosity, permittivity or refractive index or speed of light is measured.

[0072] In embodiments of the method according to the invention, at least two of the material properties heat conduction, heat capacity, speed of sound, molar mass, dynamic viscosity, permittivity or refractive index or speed of light are measured.

[0073] In embodiments of the method according to the invention, in addition to the at least two non-selective measurements, at least one selective sensor is used for the selective determination of at least one substance fraction in the substance mixture.

[0074] In embodiments of the method according to the invention, a sensor for NDIR absorption measurement for determining the CO2 content, a lambda sensor for determining the O2 content, a paramagnetic sensor for determining the O2 content, an optical sensor such as an optrode for measuring by means of fluorescence quenching (in particular a pO2 optrode), an electrochemical gas sensor or a humidity sensor (in particular by means of permittivity measurement) is used as a selective sensor.

[0075] In embodiments of the method according to the invention, it is known which substances the mixture of substances contains or which substances the mixture of substances contains that influence the material properties of the mixture of substances to a relevant extent.

[0076] In embodiments of the method according to the invention, at least one material property is determined iteratively. This allows the measurement accuracy to be improved in corresponding embodiments.

[0077] In embodiments of the method according to the invention, more than X-1 different non-selective measurement methods are used. This can increase the robustness and / or accuracy of the measurement(s).

[0078] Furthermore, in embodiments of the invention, a plausibility check of the substance proportions determined from the remaining measurements and / or a check for unknown substances in the substance mixture with a relevant influence on the measurement(s) is realized with the aid of at least one additional measuring method / measuring device.

[0079] In embodiments of the invention, at least one additional measuring method is used to measure a material property slowly but accurately with a first measuring method and to detect rapid changes in the respective material property with a second fast, but possibly absolutely inaccurate measuring method, such as a measurement subject to strong drift.

[0080] In embodiments of the invention, at least one measurement method is used that is influenced by at least two material properties (e.g., thermal conductivity and heat capacity). The measurement method is used multiple times in different versions (e.g., modulating the temperature of the substance mixture using a heater), with the influence of the different material properties being weighted differently in each version. In the example of thermal conductivity and heat capacity as material properties, this would be, for example, the measurement of the temperature of the substance mixture, with the temperature being adjustable using a controllable heater. Depending on the speed of the modulation, the measurement is predominantly influenced by the thermal conductivity (slow modulation) or the heat capacity (fast modulation).In embodiments of the invention, at least one measuring method is used in which the respective material property is measured in two different states of the substance mixture. For example, many material properties depend on the temperature and / or the pressure. In corresponding embodiments of the invention, the substance mixture is first measured at a first temperature T1 (e.g. ambient temperature) and / or a first pressure P1. Subsequently, the respective parameter is changed without changing the composition of the substance mixture and the measurement is repeated. For example, the substance mixture is heated to a temperature T2 (or cooled down) or the pressure is changed to a value P2. If the material properties of the individual components of the substance mixture have significantly different temperature or pressure behavior, the repeated measurement provides new information about the composition of the substance mixture.

[0081] In embodiments of the method according to the invention, the substance proportion of at least one substance in the substance mixture is determined by automatically setting up and solving a possibly linear system of equations from the measured substance properties.

[0082] In embodiments of the method according to the invention, the system of equations established using the determined material properties is solved analytically.

[0083] In embodiments of the method according to the invention, the system of equations established using the determined material properties is solved numerically.

[0084] In embodiments of the method according to the invention, the system of equations established using the determined material properties is solved iteratively.

[0085] Such an iterative solution of the system of equations works as follows in embodiments of the invention. Even if a material property S1 cannot be used selectively to determine the proportion of a substance in the mixture, it can be dominated by a substance A1. In the first iteration stage, it is assumed that the measurement of the material property S1 is determined only by substance A1. Then, the proportion of substance A1 is first determined, and the system of equations with X equations is reduced by 1.

[0086] In embodiments of the invention, at least one further material property S2, independent of the material property S1, is used in a similar way to estimate a material proportion A2 or further material proportions, so that the system of equations to be solved is further reduced. In embodiments of the invention, at least one material proportion is estimated in at least one iteration stage using an empirical value. In certain mixtures of substances, for example air or breathable air, certain substances (e.g. argon or nitrogen) normally occur in certain concentrations. In corresponding embodiments of the invention, these values ​​are used at least for an initial estimate in the first iteration stage, so that the system of equations can be reduced accordingly.

[0087] In embodiments of the invention, substances that have a similar influence on a material property are combined during the corresponding iteration and treated as a single substance. Substances that will have a similar influence on all measured material properties, provided that determining the separate proportions of these substances in the mixture is irrelevant in the respective application, are considered globally as a single substance in the solution of the system of equations in embodiments of the invention.

[0088] Once all the component parts of the mixture have been determined in the first iteration, these resulting values ​​are used again in at least one subsequent iteration, in which the influences of several or all components on the respective properties are taken into account, to improve the determination of the component parts of the mixture. This refines the analysis. The improvement in the accuracy of the determined component parts increases with further iterations.

[0089] In embodiments of the method according to the invention, the measurement data acquired with the measuring devices are evaluated using at least one Kl system.

[0090] A combination of elements from the numerical, iterative and / or Cl-supported determination of the substance proportions is also possible in embodiments of the invention.

[0091] In embodiments of the method according to the invention, at least one of the values ​​temperature, pressure, volume flow and / or humidity of the substance mixture is measured and used to compensate for at least one of the other measurements carried out to determine the substance proportions.

[0092] In embodiments of the method according to the invention, it is used in a medical-technical application.

[0093] In embodiments of the method according to the invention, at least a gas fraction of respiratory gas is determined during the ventilation of a patient. In embodiments of the method according to the invention, at least one device according to the invention for determining substance fractions of a fluid mixture or a medical device according to the invention is used.

[0094] The following figures illustrate exemplary embodiments of the invention. They show:

[0095] Fig. 1 : A schematic block diagram of an inventive device for

[0096] Determination of at least one substance component in a fluid mixture,

[0097] Fig. 2 to 4: Schematic block diagrams of a device according to the invention for determining at least one substance fraction in a fluid mixture in a bypass configuration in three different designs,

[0098] Fig. 5: A sensor configuration of a device according to the invention for determining at least one substance fraction in a fluid mixture,

[0099] Fig. 6: A schematic block diagram of an inventive device for

[0100] Determination of at least one substance fraction in a fluid mixture in a main stream configuration,

[0101] Fig. 7: An illustration of different iteration stages in a corresponding method according to the invention for determining at least one substance fraction in a fluid mixture and

[0102] Fig. 8: A schematic representation of the measured value processing according to the invention.

[0103] Figure 1 shows a schematic block diagram of a device (1) according to the invention for determining at least one component of a fluid mixture (10). The device (1) for determining at least one component of a fluid mixture (10) comprises an evaluation unit (2), two non-selective sensors (3), a selective sensor (4), and a compensation device (5) for recording measured values ​​relating to a fluid mixture (10). The evaluation unit (2) is designed to retrieve and evaluate the measured values ​​for determining at least one component of the fluid mixture (10).

[0104] In the illustrated embodiment of the invention, the evaluation unit (2) can utilize a K1 system (6) to determine the substance fractions of the fluid mixture (10). The at least one specific substance fraction of the fluid mixture (10) can be output using an output unit (7), for example, as a display, as an acoustic output, or as a digital data packet.

[0105] Figures 2, 3 and 4 show various embodiments of a device (1) according to the invention for determining at least one substance fraction in a fluid substance mixture (10) in sidestream configurations.

[0106] Figure 2 shows the arrangement of non-selective sensors (3) in a secondary stream (21) that branches off from the main stream (20) of the fluid mixture (10) at a sampling point (22). The fluid mixture (10) is pumped into the secondary stream (21) and past the sensors (3) for measurement by means of a suction pump (8) arranged downstream of the sensors (3) in the flow direction. Embodiments with at least one selective sensor are also possible according to the invention.

[0107] According to the embodiment shown in Figure 3, the suction pump (8) is positioned in the secondary flow (21) in the flow direction upstream of the sensors (3).

[0108] Figure 4 shows an embodiment with two sensors (3) arranged in parallel, marked M2 and M3.

[0109] Figure 5 shows a sensor configuration 3 for parallel measurement of at least three measured values. The fluid mixture (10) can be guided into the region of the sensor configuration (3) using a line, here designed as a main flow line (20) or a secondary flow line (21). The sensor configuration (3) comprises a permittivity sensor (3') designed as a plate capacitor, a sound velocity and / or volume flow sensor (3") implemented using an ultrasonic sensor, and a viscosity sensor (3"') implemented using a differential pressure sensor.

[0110] The differential pressure can be measured using pressure sensors located at the inlet and outlet of the plate capacitor. The space between the capacitor plates is also used for ultrasonic measurement.

[0111] Appropriate arrangements enable the realization of compact sensor configurations (3), which are particularly important for mobile applications. Figure 6 shows a medical device (15) designed as a ventilator, which has a device (1) for determining at least one substance fraction in a fluid mixture (10), which is integrated into the hose system (23) of the ventilator with respect to the sensors, shown here as non-selective sensors (3).

[0112] Figure 7 shows the iterative determination of substance proportions of a fluid substance mixture (10) according to advantageous embodiments of the invention. Based on the initially determined measured values ​​M1, M2 ... Mn, the substance proportions C1', C2', ... Cn' are determined in the first step, whereby the estimates E1', E2', ... En' are used. Based on the determined substance proportions, improved estimates E1", E2", ... En" are used in the second iteration stage to determine the now more precise substance proportions C1", C2", ... Cn". Depending on the available time and computing resources, embodiments according to the invention with more than two iteration stages are also feasible.

[0113] Figure 8 shows schematically the mathematical evaluation of the measured values ​​recorded by the sensors (3) using the evaluation unit (2) to determine the substance proportions C1, ... Cn of a fluid substance mixture (10).

Claims

Patent claims 1. Device (1) for determining substance proportions of a fluid substance mixture (10), comprising at least two different non-selective measuring devices (3), each designed to measure a substance property of the substance mixture (10), wherein the substance properties measured with the measuring devices (3) are different and independent of one another, further comprising at least one evaluation unit (2) for evaluating the measured values ​​of the at least two different substance properties recorded with the measuring devices (3) and for determining at least one substance proportion in the substance mixture (10) from the combination of the measured substance properties.

2. Device (1) according to claim 1, characterized in that, for a number X of proportions to be determined in the fluid substance mixture, it has at least X-1 non-selective measuring devices (3) with which different, mutually independent material properties of the substance mixture (10) can be measured.

3. Device (1) according to one of the preceding claims, characterized in that at least two of the non-selective measuring devices (3) are designed to carry out the respective measurements simultaneously or at least partially overlapping in time or have a measurable or known time offset so that the individual measurements can be synchronized.

4. Device (1) according to one of the preceding claims, characterized in that it is designed to determine the proportion of O2 and / or CO2 in the substance mixture (10).

5. Device (1) according to one of the preceding claims, characterized in that at least one measuring device (3) has at least one sensor for determining one of the material properties of heat conduction, heat capacity, speed of sound, molar mass, dynamic viscosity, permittivity or refractive index or speed of light.

6. Device (1) according to one of the preceding claims, characterized in that it additionally has at least one selective sensor (4) for the selective determination of at least one substance component in the substance mixture (10).

7. Device (1) according to one of the preceding claims, characterized in that it is designed for the iterative determination of at least one material property.

8. Device (1) according to one of the preceding claims, characterized in that it has an evaluation unit (2) with which the proportion of at least one substance in the substance mixture (10) can be determined by setting up a system of equations from the measured substance properties and the solution of the system of equations.

9. Device (1) according to one of the preceding claims, characterized in that it has a compensation device (5) with which, for example, the temperature, the pressure, the volume flow and / or the humidity of the substance mixture (10) can be measured and used to compensate for at least one of the other measurements carried out to determine the substance proportions.

10. Device (1) according to one of the preceding claims, characterized in that it is designed to determine at least a gas component of respiratory gas during the ventilation of a patient.

11. A medical device (15) comprising at least one device (1) for determining substance proportions of a fluid substance mixture (10) according to one of claims 1 to 10.

12. Medical device (15) according to claim 11, characterized in that it is designed as a ventilator and that the substance mixture (10) is a gas mixture.

13. Method for determining the substance proportions of a fluid mixture (10) comprising at least the following method steps: Carrying out at least two different non-selective measurements, wherein in each case a material property of the substance mixture (10) is measured and wherein the material properties measured with the different measurements are independent of each other, Combination of the measured substance properties to determine the proportion of at least one substance in the mixture (10).

14. Method according to claim 13, characterized in that, for a number of X proportions to be determined in the fluid substance mixture (10), at least X-1 different non-selective measuring methods or measuring devices are used which measure different, mutually independent material properties of the substance mixture (10).

15. Method according to one of claims 13 and 14, characterized in that at least two of the non-selective measurements are carried out simultaneously or at least partially overlapping in time or have a measurable or known time offset, the individual measurements being synchronized.

16. Method according to one of claims 13 to 15, characterized in that the proportion of O2 and / or CO2 in the substance mixture (10) is determined.

17. Method according to one of claims 13 to 16, characterized in that at least one of the material properties heat conduction, heat capacity, speed of sound, molar mass, dynamic viscosity, permittivity or refractive index or speed of light is measured.

18. Method according to one of claims 13 to 17, characterized in that in addition to the at least two non-selective measurements, at least one selective sensor is used for the selective determination of at least one substance component in the substance mixture (10).

19. Method according to one of claims 13 to 18, characterized in that at least one material property is determined iteratively.

20. Method according to one of claims 13 to 19, characterized in that the substance proportion of at least one substance in the substance mixture (10) is determined by automatically setting up and solving a system of equations from the measured substance properties.

21. Method according to one of claims 13 to 20, characterized in that at least one of the values ​​temperature, pressure, volume flow and / or humidity of the substance mixture is measured and used to compensate for at least one of the other measurements carried out to determine the substance proportions.

22. Method according to one of claims 13 to 21, characterized in that at least a gas component of respiratory gas is determined during the ventilation of a patient.

23. Method according to one of claims 13 to 22, characterized in that at least one device (1) according to one of claims 1 to 10 or a medical device (15) according to claim 11 is used.

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