Device, medical apparatus, setting unit, computer program product, storage device, and method for determining carbon dioxide concentration in measured gas

Abstract

The invention relates to a method for determining the carbon dioxide concentration in a measurement gas, comprising the following steps: branching off measurement gas from a main line (15) of a medical device (12) via a branch line (14) during the inhalation phase of a person (13) connected to the medical device (12) as inhaled gas and during the exhalation phase of the person (13) as exhaled gas towards a sensor unit (11); conveying the measurement gas from the main line (15) via the branch line (14) towards the sensor unit (11) by means of a fluid conveying unit (24); adaptively setting the fluid conveying unit (24) while taking into account the airway pressure in the main line (15) in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) towards the sensor unit (11) during the inhalation phase and the exhalation phase; and determining the carbon dioxide concentration in the measurement gas by means of the sensor unit (11). The invention further relates to an ascertainment device (10), a medical apparatus (12), a setting unit (26), a computer program product (29), and a memory device (30) having the computer program product (29) stored thereon for carrying out the method according to the invention.

Description

Technical Field

[0001] The present invention relates to a method for ascertaining the carbon dioxide concentration in a measurement gas, in particular from a medical device and / or in the medical device. Furthermore, the present invention relates to a computer program product comprising instructions for executing such a method and to a memory device on which such a computer program product is stored. Furthermore, the present invention relates to an ascertaining device, a medical device, and a setting unit for ascertaining the carbon dioxide concentration. Background Art

[0002] Carbon dioxide is one of the most important parameters for evaluating the effectiveness of artificial respiration during the artificial respiration of a person by means of a respirator. Therefore, precise and reliable monitoring of the carbon dioxide concentration during artificial respiration is of decisive importance.

[0003] Various physical and / or chemical methods are considered for determining the carbon dioxide concentration. For example, the carbon dioxide concentration can be detected using infrared sensors, electrochemical sensors, colorimetry, or mass spectrometry. Some of these methods have complex measurement structures and are therefore correspondingly expensive and / or unsuitable for continuous carbon dioxide concentration monitoring.

[0004] Furthermore, a system is known in which the carbon dioxide concentration in the measured gas can be inferred by heat conduction of the measured gas or a gas sample at a sensor cell. To determine the carbon dioxide concentration, a sensor cell located in close proximity to the so-called main flow or main line is inflated with inhaled and exhaled gas, for example, using a diffusion device. Such a system is known from German patent application DE 10 2010 047 159 A1. A hydrophobic blocking device is also proposed therein to suppress condensed moisture. A problem with this system is that the cross-influence of gas parameters synchronized with the breathing phases, i.e., inhalation and exhalation, such as the measured gas temperature and / or measured gas humidity, leads to an inaccurate determination of the carbon dioxide concentration in the measured gas due to a lack of selectivity in the sensor cell. In other words, the varying humidity caused by inhalation or the inspiratory phase and exhalation or the expiration phase results in varying humidity at the sensor, depending on the occupancy of the hydrophobic blocking device. This can lead to varying measured values ​​and corresponding measurement errors, as well as partial or complete gas blockage, which prevents further execution of the desired measurement.

[0005] In addition, a known measuring device is used in which a measuring gas is drawn or bifurcated from the main line toward a suitable sensor unit by means of a pump so as to obtain carbon dioxide concentration by means of the sensor unit. A disadvantage of this known solution is that the volume flow of the measuring gas produced by the pump in the bifurcated line has caused an influence on the measurement signal. Due to the varying airway pressure at the patient's place, different pressure differences on the bifurcated line have been produced. Thus, a varying volume flow has occurred, which has produced a measurement signal synchronized with the respiratory phase. Thus, it is almost impossible to obtain the necessary carbon dioxide difference for obtaining carbon dioxide concentration accurately between the two respiratory phases. Additionally, due to the varying volume flow, the correct connection in time of the two phases is disturbed. Summary of the Invention

[0006] The object of the present invention is to at least partially address the aforementioned problems. In particular, the object of the present invention is to provide a device and a method for determining the carbon dioxide concentration in a measurement gas from a medical device of the type described in the simplest, most cost-effective and most precise manner possible.

[0007] The aforementioned object is achieved by the claims. In particular, it is achieved by the method according to claim 1, the ascertainment device according to claim 9, the medical device according to claim 16, the setting unit according to claim 21, the computer program product according to claim 22, and the storage device according to claim 23. Further advantages of the present invention are apparent from the dependent claims, the description, and the drawings. Features described in conjunction with the method are of course also applicable in conjunction with the ascertainment device according to the invention, the medical device according to the invention, the setting unit according to the invention, the computer program product according to the invention, and the storage device according to the invention, and vice versa, so that reference is always made to each other and / or to the various aspects of the invention with respect to the disclosure.

[0008] According to a first aspect of the present invention, a method for determining the carbon dioxide concentration in a measurement gas is provided. The method comprises the following steps:

[0009] - branching off the measuring gas from the main line of the medical device via a branching line towards the sensor unit during the inhalation phase of the person connected to the medical device as inhaled gas and during the exhalation phase of the person as exhaled gas,

[0010] - conveying the measuring gas from the main line via the branch line to the sensor unit by means of the fluid conveying unit,

[0011] - adaptively setting the fluid delivery unit taking into account the airway pressure in the main line in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit during the inspiration and expiration phases, and

[0012] The carbon dioxide concentration in the measurement gas is determined by means of the sensor unit.

[0013] It is therefore proposed to control a fluid delivery unit, for example in the form of a suction pump, with the foreknowledge of the airway pressure in such a way that the volume flow is kept as constant as possible during the different breathing phases, or during the inhalation phase, in particular the inhalation phase of artificial respiration performed by a medical device, and during the exhalation phase, in particular the exhalation phase of artificial respiration performed by a medical device, or that the change in the volume flow during the different breathing phases is at least as small as possible or becomes at least as small as possible relative to the change in carbon dioxide concentration between the carbon dioxide concentration in the exhalation phase and the carbon dioxide concentration in the carbon dioxide-free or essentially carbon dioxide-free inhalation phase.

[0014] “Bifurcation of the measurement gas from the main line of the medical device during the inhalation phase and during the exhalation phase” should be understood here as meaning that the measurement gas is continuously branched off from the beginning of the inhalation phase to the end of the exhalation phase and then, in particular without interruption, in principle as often as desired from the beginning of another inhalation phase to the end of another exhalation phase.

[0015] “Adaptively setting the fluid delivery unit to produce a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit during the inhalation phase and the exhalation phase” can be understood to mean, correspondingly, that the fluid delivery unit is adaptively set in such a way, taking into account the current airway pressure in the main line, that a volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit is produced that remains as constant as possible from the inhalation phase through the exhalation phase and any further subsequent inhalation and exhalation phases and / or changes as little as possible. An “inhalation phase of a person” can be understood to mean an inhalation process performed by a person with or without at least partial support from a medical device. An “exhalation phase of a person” can be understood to mean an exhalation process performed by a person with or without at least partial support from a medical device.

[0016] Under the framework of the present invention, at first known is that, with regard to simple measurement structure, when using bifurcated line, sensor unit and fluid delivery unit, the relatively small volume flow in the bifurcated line is in principle just enough to desirably ask for carbon dioxide concentration.Usually, for the so-called carbon dioxide measurement of suctioning in the measuring gas, use or set the suction volume flow of common 100ml / min to 200ml / min.Such volume flow is necessary because employed assembly such as filter, hose and dehumidifying equipment.Now known at this, the simple suction device that is optionally configured as disposable not only should obtain the significantly smaller volume flow in the scope between for example 40ml / min and 60ml / min and the relatively low gas pressure in the scope between for example 25mbar and 35mbar, at this and also enough measuring gases are delivered towards the sensor unit, for desirably asking for carbon dioxide concentration in the measuring gas.

[0017] In some embodiments, the present invention relates to a device for the control of the present invention.The device of the present invention is used for the control of the fluid delivery unit.Yet, owing to little gas pressure and / or little volume flow and the relatively high dependency of the airway pressure of patient and / or medical appliance occur.Volume flow and gas pressure during suction are along with the gas pressure in the breathing phase of patient and / or medical appliance that carries out artificial respiration by medical appliance and change.In order to stop or at least reduce this influence, and utilize the cognition of airway pressure or corresponding patient pressure to control the fluid delivery unit like this, make the volume flow in the bifurcated line and / or the gas pressure in the bifurcated line keep constant as far as possible.Should abandon extra volume flow measurement at this as far as possible.

[0018] During normal artificial respiration of a person, the airway pressure varies continuously, for example, between approximately 25 mbar during the inspiration phase and approximately 5 mbar during the expiration phase. If, for example, the measured gas is then conveyed to the sensor unit via the branch line at 50 ml / min, then only a small amount of support is required by the fluid conveying unit during the inspiration phase.

[0019] During the exhalation phase, on the other hand, a significantly higher suction power is required because the pressure difference relative to the surroundings is only 1 / 5. For a gas flow rate of, for example, 50 ml / min, approximately 30 mbar is required. If the patient has an airway pressure of, for example, 25 mbar and / or this airway pressure is set at least partially by the medical device, then the fluid delivery unit must generate only an additional 5 mbar during the inspiration phase to achieve the desired volume flow. During the exhalation phase, with an airway pressure of, for example, only 5 mbar, an additional 25 mbar is required through the fluid delivery unit to achieve the same volume flow.

[0020] The pump vacuum of the fluid conveying unit, in particular a fluid conveying unit designed as a pump, can now be set such that the sum of the airway pressure and the pump pressure or the pressure generated by the fluid conveying unit together results in 30 mbar.

[0021] Such a process is shown in the table below.

[0022]

[0023] In known extraction devices that perform suction, the filters, dehumidifiers, branch lines, and significantly higher gas or volumetric flows of, for example, 200 ml / min used therein result in a relatively high pressure drop compared to the proposed extraction device and / or measuring device, so that the pressure difference relative to the performance of the fluid delivery unit also lies in a significantly higher range, for example, between 150 mbar and 200 mbar. The additional pressure difference caused by the airway pressure is of minor importance here, as, in particular, the fluid delivery unit, which is in the form of a pump, can be operated at a constant power and generate a moderate gas flow. Therefore, in such systems, it has not previously been necessary to consider the inventive control of the fluid delivery unit or adaptively setting the fluid delivery unit while taking into account the airway pressure.

[0024] In order to determine the carbon dioxide concentration in the measured gas, the thermal conductivity of the exhaled gas is measured in the sensor unit, in particular. This measurement is achieved by a microstructured heating element on the thin diaphragm of the sensor unit. A thermally suitable device is located near the heating element, which measures the superheat temperature of the gas near the heating element relative to the silicon frame of the diaphragm. In principle, it is known in the prior art to determine the carbon dioxide concentration by means of the thermal conductivity of the measured gas. Further details can be found, for example, in German patent application DE 10 2010 047 159 A1. However, within the framework of the present invention, it has been recognized that a constant volume flow of the measured gas through the branching line is important for determining the carbon dioxide concentration in the measured gas while taking into account the thermal conductivity of the measured gas, and the proposed method has been developed accordingly. Therefore, the sensor unit preferably includes a thermal conductivity sensor for measuring the thermal conductivity and / or heat conduction of the measured gas, i.e., the thermal conductivity of the branched portion of the inhaled gas and the thermal conductivity of the branched portion of the exhaled gas. The carbon dioxide concentration is then determined based on the measured thermal conductivity. "Determining the CO2 concentration using a sensor unit" can therefore be understood to mean determining the CO2 concentration based on various measurements and calculations, using a sensor unit, or, in other words, determining the CO2 concentration in the measured gas based on its thermal conductivity measured by the sensor unit. The sensor unit can be used to determine the CO2 difference and calculate the CO2 concentration based on the measured values ​​and / or determine it based on a lookup table, for example. As already mentioned, the measured gas preferably includes inhaled and expired gas. Therefore, the relative CO2 concentration in the expired gas can be determined using the CO2 difference between the inhaled and expired gas.

[0025] The method for determining the carbon dioxide concentration is implemented, in particular, as a method for determining the carbon dioxide concentration during artificial respiration of a person connected to the medical device by means of the medical device and / or at least during the operation of the medical device. Thus, at least temporarily, in the absence of current information about the current airway pressure, adaptive settings of the fluid delivery unit can be performed, for example, in the form of an emergency procedure and / or a transition procedure. The method can be implemented as a method for determining the carbon dioxide concentration in the main line or so-called mainstream measured gas from the medical device, in particular a ventilator. "Adaptively setting the fluid delivery unit" can be understood, in particular, to mean continuously setting and / or adjusting the fluid delivery unit according to the current airway pressure in the main line. In other words, the fluid delivery unit is set and / or controlled differently according to the current airway pressure in the main line.

[0026] The adaptive setting of the fluid delivery unit is performed, in particular, by a suitable setting unit, for example, in the form of a controller of the medical device. "Measurement gas" can be understood to mean the gas sample to be measured at the sensor unit. The measurement gas corresponds to a portion of the inhaled gas during the inhalation phase and to a portion of the exhaled gas during the exhalation phase. In other words, a portion of the inhaled gas is branched off as measurement gas during the inhalation phase, and a portion of the exhaled gas is likewise branched off as measurement gas during the exhalation phase.

[0027] "Delivering measured gas" can be understood as sucking measured gas from the main line into the branch line leading to the sensor unit. The fluid delivery unit is in this case particularly configured as a pump and / or a suction pump. The method steps shown do not necessarily have to be performed in a specific order. Rather, the method steps can be performed at least partially simultaneously. A "uniform volume flow" can be understood here as a volume flow whose value varies by less than 20%, in particular less than 10%, over the time period of at least one inhalation phase and the subsequent exhalation phase.

[0028] The airway pressure corresponds to the gas pressure of the inhaled gas in the main line during the inspiration phase and to the gas pressure of the exhaled gas in the main line during the exhalation phase. Therefore, the term "airway pressure" can also be understood to mean the gas pressure in the main line, in particular the gas pressure of the inhaled gas and the gas pressure of the exhaled gas. The airway pressure can be measured as the actual airway pressure and / or determined or used as a set airway pressure.

[0029] According to one embodiment of the present invention, it is possible that in the method, the airway pressure in the main line is measured by an airway pressure sensor, and the fluid delivery unit is adaptively set using the measured airway pressure in the main line to produce a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit. In other words, the fluid delivery unit is set using the actually measured airway pressure. As a result, the carbon dioxide concentration in the measurement gas can be determined particularly accurately. In this case, the main line can have: an inhalation gas line section for conducting inhalation gas, in particular only inhalation gas; and a total gas line section for conducting inhalation gas and exhalation gas, wherein the airway pressure is measured in and / or at the total gas line section.

[0030] Within the scope of the present invention, a method for determining the carbon dioxide concentration in the measured gas during pressure-guided artificial respiration of a person using a medical device is also proposed, wherein, using the airway pressure in the main line that is set due to the pressure-guided artificial respiration of the person, a fluid delivery unit is adaptively set to produce a uniform volume flow and / or a uniform gas pressure of the measured gas in the branch line to the sensor unit. Due to the pressure-guided artificial respiration of the person, the airway pressure sensor mentioned above can be omitted. For example, the airway pressure required for adaptively setting the fluid delivery unit can be read directly from the controller of the medical device and used. Thus, the fluid delivery unit can be adaptively set for pressure-guided artificial respiration using the airway pressure set for the operation of the medical device. Furthermore, it is possible, in the method according to the invention for determining the carbon dioxide concentration in the measurement gas during volume-guided artificial respiration of a person by means of a medical device, to adaptively set the fluid delivery unit using the airway pressure in the main line resulting from the volume-guided artificial respiration of the person in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit.

[0031] Furthermore, it is possible that, in the method according to the present invention, the fluid delivery unit for delivering the measured gas from the main line via the branch line to the sensor unit includes a piezoelectric pump, and that the operating voltage of the piezoelectric pump is adaptively set, taking into account the airway pressure and using a lookup table, to generate a uniform volume flow and / or gas pressure of the measured gas in the branch line toward the sensor unit. Using a piezoelectric pump and an associated lookup table, particularly an associated lookup table with a characteristic curve according to a type of characteristic curve diagram, the fluid delivery unit can be quickly, simply, and inexpensively set in a desired manner. Based on the characteristic curve of the lookup table, it is possible to quickly determine and / or determine which volume flow and gas pressure are or will be present in the branch line at which voltage or operating voltage of the piezoelectric pump. However, a necessary precondition for using a piezoelectric pump and an associated lookup table is that, in experiments within the framework of the present invention, it has been demonstrated that the aforementioned lower pressures and lower volume flows are sufficient for the desired determination of the carbon dioxide concentration by means of heat conduction measurement in the measured gas. For conventional systems with a volume flow of the measurement gas of, for example, more than 100 ml / min and / or more than 40 mbar, a piezoelectric pump would be less suitable or even unsuitable.

[0032] Furthermore, it is possible, in the method according to the invention, to adaptively adjust the fluid delivery unit in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit, taking into account only the airway pressure in the main line during the inspiration phase or taking into account only the airway pressure in the main line during the expiration phase of artificial respiration. Experiments within the framework of the invention have shown that, for example, observing or taking into account only the inspiration phase or the expiration phase is sufficient to determine the carbon dioxide concentration with sufficient accuracy and / or generate a volume flow and / or a gas pressure of the measurement gas that is as uniform as possible, even with reduced computing power.

[0033] Furthermore, it is possible that, in the method according to the present invention, the fluid delivery unit is operated at a constant power during the expiration phase of artificial respiration, and during the inspiration phase of artificial respiration, the fluid delivery unit is adaptively set, taking into account the airway pressure during the inspiration phase of artificial respiration, to produce a uniform volume flow and / or gas pressure of the measurement gas in the branch line toward the sensor unit. Therefore, it is not necessary to continuously adaptively set and / or operate the fluid delivery unit. Therefore, it is also possible to reduce the necessary computing power for determining the carbon dioxide concentration and to perform the method in a resource-saving manner. Here, during the expiration phase of artificial respiration, the fluid delivery unit is operated at a constant power, in particular at maximum power or at a constant power in the range between 80% and 100% of the maximum power of the fluid delivery unit.

[0034] In another design variant of the present invention, in this method, during the expiration phase of artificial respiration, taking into account the airway pressure during the expiration phase of artificial respiration, the fluid delivery unit is adaptively set or operated, and during the inspiration phase of artificial respiration, the fluid delivery unit is deactivated to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line toward the sensor unit. Therefore, the method can be operated efficiently and particularly energy-savingly. In addition, the service life of the fluid delivery unit can be extended. "Deactivating the fluid delivery unit" can be understood as cutting off the fluid delivery unit and / or at least not operating the fluid delivery unit.

[0035] According to another aspect of the present invention, a determination device is provided for determining the carbon dioxide concentration in a measurement gas from a medical device during artificial respiration of a person by the medical device. The determination device comprises:

[0036] - a sensor unit for determining the carbon dioxide concentration in the measurement gas,

[0037] a branch line for branching off the measuring gas from the main line of the medical device as inhaled gas during the inhalation phase of the person and as exhaled gas during the exhalation phase of the person towards the sensor unit,

[0038] a fluid conveying unit for conveying the measuring gas from the main line via the branch line towards the sensor unit, and

[0039] a setting unit configured and designed to adaptively set the fluid delivery unit taking into account the airway pressure in the main line in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit during the inspiration phase and the expiration phase.

[0040] The determination device according to the present invention thus offers the same advantages as those described in detail with reference to the method according to the present invention. The determination device can be designed as a separate device relative to the medical device or as a component of the medical device. The setting unit can include a controller of the medical device or be designed as a component of such a controller.

[0041] According to another embodiment of the present invention, the acquisition device can have an airway pressure sensor for measuring the airway pressure in the main line, wherein the setting unit is configured and designed to adaptively set the fluid delivery unit taking into account and / or using the measured airway pressure in the main line in order to generate a uniform volume flow and / or gas pressure of the measuring gas in the branch line to the sensor unit.

[0042] Furthermore, the ascertainment device can be configured to ascertain the carbon dioxide concentration in the measurement gas during pressure-guided artificial respiration of a person by means of a medical device, wherein the setting unit can be configured and designed to adaptively set the fluid delivery unit using the airway pressure in the main line that is set due to the pressure-guided artificial respiration of the person, in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit.

[0043] Furthermore, the determination unit can be configured to determine the carbon dioxide concentration in the measurement gas during volume-guided artificial respiration of the person by means of the medical device, wherein the setting unit can be configured and designed to adaptively set the fluid delivery unit using the airway pressure in the main line resulting from the volume-guided artificial respiration of the person, in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit.

[0044] In addition, the fluid conveying unit can have a piezoelectric pump for conveying the measuring gas from the main line via the branch line toward the sensor unit, wherein the setting unit is configured to adaptively set the operating voltage of the piezoelectric pump so as to generate a uniform volume flow and / or gas pressure of the measuring gas in the branch line toward the sensor unit while taking into account the airway pressure and using a lookup table.

[0045] In the acquisition device according to the invention, the setting unit can furthermore be configured and designed to adaptively set the fluid delivery unit while taking into account only the airway pressure in the main line during the inhalation phase of artificial respiration or while taking into account only the airway pressure in the main line during the exhalation phase of artificial respiration, and to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit.

[0046] Furthermore, the setting unit of the ascertainment device according to the invention can be configured and designed to operate the fluid delivery unit at a constant power during the expiration phase of artificial respiration and to adaptively set the fluid delivery unit during the inspiration phase of artificial respiration, taking into account the airway pressure during the inspiration phase of artificial respiration, in order to produce a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit. Furthermore, the setting unit can be configured and designed to adaptively set the fluid delivery unit during the expiration phase of artificial respiration, taking into account the airway pressure during the expiration phase of artificial respiration, and to deactivate the fluid delivery unit during the inspiration phase of artificial respiration, in order to produce a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit.

[0047] In addition, the determination device according to the present invention can have at least one HME filter in and / or at the branch line. In this case, the setting unit is configured to compensate for the possible influence of the HME filter on the volume flow and / or gas pressure in the branch line so that a uniform volume flow and / or uniform gas pressure is generated in the branch line. Within the framework of the present invention, it is known that when using an HME filter for filtering the measured gas, temperature and humidity differences in the measured gas (which are caused during the inspiration and expiration phases of a person or a patient connected to the medical device) can be buffered, balanced, reduced and / or smoothed so that the carbon dioxide concentration can be determined or measured and / or calculated significantly more accurately than a system without an HME filter. In other words, the HME filter helps to determine the carbon dioxide concentration more accurately in a simple manner.

[0048] It is also known that the HME filter used has no worthy of mention and / or adverse effects on other gas components to be measured. That is to say, the humidity and heat of the measured gas are evenly distributed over time, and can not affect the actual measurement effect that is achieved by the difference in heat conduction between the existing and missing carbon dioxide. Therefore, the HME filter will not or will not basically affect the supply of carbon dioxide to the sensor unit. Only due to the volume of the HME filter, the gas delivery may be slightly delayed. However, this will not or at least will not be worthy of mentioning the impact of the desired carbon dioxide concentration in the measured gas. Due to the change in temperature and / or humidity in the measured gas and the change in heat conduction that occurs synchronously with the breathing phase, in addition to the changing volume flow, is considered to be the main reason for inaccurate carbon dioxide measurement. This problem can be considered simply, cost-effectively and effectively by using an HME filter.

[0049] In medical technology, a "HME filter" should be understood as a heat and moisture exchange filter and / or a filter housing having such a filter material. Therefore, an HME filter can be understood as a heat and moisture exchanger. HME filters have been used in particular in the main flow or main line of a ventilator or corresponding medical device, where inhaled gas and exhaled gas alternately flow through the HME filter during the respiration cycle. HME filters have been used in particular to properly humidify a patient's inhaled gas or inhaled air and to prevent cross-contamination in the main line. The proposed HME filter of the ascertainment device is preferably configured, in terms of size and / or functionality, to buffer, equalize, reduce, and / or smooth temperature and / or humidity differences in the branched measurement gas for at least one breath, i.e., the duration of the inhalation phase and the exhalation phase. Therefore, the HME filter can not only be used for conventional filtering of the measurement gas, but can also be used in particular to buffer, equalize, reduce, and / or smooth temperature and / or humidity differences in the branched measurement gas. At least one HME filter can have a filter housing and a filter material for filtering the measured gas in the filter housing. The filter housing can be configured as a rigid filter housing or as a flexible or elastically deformable filter housing, which is, for example, tubular. The HME filter can also be configured without a filter housing and only with the functionally relevant HME filter material, for example, in the form of a hose insert.

[0050] Since preferably only the drawn-in measuring gas flows through the HME filter, i.e., in particular not all the gas of the main line flows through the HME filter, the HME filter can be designed to be smaller, in particular many times smaller, than conventional HME filters used in the main line. The HME filter is preferably arranged upstream of the sensor unit in the direction of measuring gas flow toward the sensor unit and / or upstream of the sensor unit when installed in a ventilator, so that the measuring gas can flow through the HME filter before it reaches the sensor unit.

[0051] The ascertaining device is preferably designed for use in a medical appliance in the form of a ventilator and / or for use together with the medical appliance. The branch line preferably has a flexible hose line to guide the branched measurement gas toward the sensor unit. In addition, the branch line can be designed in the form of a flexible hose line. In addition, it is feasible that the branch line also has other functional components such as adapters and / or connecting components at the sensor unit and / or at the HME filter in addition to the hose line to connect the hose line to the main line.

[0052] The sensor unit can be designed and / or configured for determining the carbon dioxide concentration in the measurement gas in accordance with the sensor described in DE 10 2010 047 159 A1, wherein the measurement gas is supplied to the sensor unit by means of a fluid conveying unit and in particular by means of a suction pump. The branch line has an internal diameter that is smaller, in particular many times smaller, than a corresponding main line of the ventilator.

[0053] According to another embodiment of the present invention, it is feasible to design at least one HME filter in the branch line for the acquisition device. Therefore, the acquisition device can be provided in a particularly compact and correspondingly space-saving manner. In addition, the acquisition device can be simply installed in the place and / or among the medical instruments. At least one HME filter can be designed in the branch line when installed. At least one HME filter is particularly designed within the pipeline volume of the branch line. The branch line can, for example, have a hose line, wherein at least one HME filter is at least designed in a part of the internal volume of the hose line. In other words, at least a part of the hose cover of the hose line can surround at least one HME filter in the form of a cover within the entire length of the at least one HME filter or within the scope of a part of the length of the HME filter. At least one HME filter can be designed as a hose insert. At least one HME filter is preferably designed in the branch line in a form-and / or force-locking manner. Therefore, the outer peripheral surface of at least one HME filter can be designed complementary to the inner peripheral surface of the branch line, particularly to the inner peripheral surface of the hose line of the branch line. Thus, the outer diameter of the at least one HME filter can correspond to the inner diameter of the hose line at the location where the at least one HME filter is positioned in the hose line, or be slightly smaller than the inner diameter of the hose line at this location in order to insert the at least one HME filter into the branch line.

[0054] Furthermore, it is possible that, in the ascertainment device according to the present invention, the branch line includes a main line-side end section for connecting the branch line to the main line, and a sensor-side end section for connecting the branch line to the sensor unit, wherein an HME filter is arranged at and / or within the main line-side end section. Thus, one, or in particular, each HME filter is arranged as close to and / or as close to the main line as possible. This allows the HME filter to perform a standardized buffering or compensation of temperature and / or humidity differences in the measured gas as early as possible upstream of the sensor unit. This effectively prevents or at least effectively reduces unwanted condensation in the branch line downstream of the HME filter and / or upstream of the sensor unit. This is particularly advantageous when the branch line has a longer hose line and critical conditions exist, such as a relatively cold external temperature, where the temperature in the hose line is significantly below the mask temperature or below the average humidity dew point. The term "the sensor-side end section is designed to connect the branch line to the sensor unit" can be understood to mean that a connection is provided at the sensor-side end section for fluid-tightly connecting the branch line to the main line, in particular to a mating connection of the main line. "Fluid-tightly connected" can be understood to mean a connection through which the measured gas can flow, in particular be drawn, from the main line into the branch line without leakage. The term "the HME filter is arranged at and / or in the main line-side end section" can be understood to mean that the HME filter is at least partially arranged, for example, in the form of a hose insert, in the main line-side end section of the branch line or of a hose line of the branch line, or as a mounting part on the hose line, at least partially outside such a hose line.

[0055] In addition, it is feasible that, in the acquisition device according to the present invention, the branch line has: an end section on the main line side for connecting the branch line to the main line and an end section on the sensor side for connecting the branch line to the sensor unit, wherein the acquisition device has: a first HME filter at and / or in the end section on the main line side, and a second HME filter at and / or in the end section on the sensor side. The second HME filter at and / or in the end section on the sensor side can effectively protect the sensor unit from condensed moisture. This has again resulted in a measurement gas supply as free of moisture as possible toward the sensor unit and has therefore resulted in correspondingly accurate measurement results. The two HME filters are preferably designed to be spaced apart from each other, for example, more than 50 cm, in particular in the range between 50 cm and 150 cm, along the branch line. The two HME filters preferably have the same size and / or shape.

[0056] In addition, it is feasible that, in obtaining device according to the present invention, the first HME filter in the end section of the main pipeline side of branching line is designed to the form of hose insert, wherein, along the flow direction of measuring gas through branching line, observe, branching line has the larger internal diameter than in the zone of the downstream of HME filter on the level of HME filter. Because the branching line in the downstream of HME filter is less susceptible to the moisture influence of the condensation in the measuring gas, the internal diameter of the branching line in the downstream of HME filter can be designed to be relatively small thus. Therefore, can save material and cost and branching line can be designed compactly. Especially, can the dead space and / or measurement hysteresis in the branching line be kept relatively small thus. Should consider the flow direction of measuring gas through branching line under the state that it is installed in the medical unit of obtaining device. The flow direction of the main line then extends through the branch line, there through at least one HME filter arranged in and / or at the branch line, and downstream of the at least one HME filter toward the sensor unit and, for example, toward a pump, which can be arranged downstream of the sensor unit to draw the measured gas from the main line into the branch line. The inner diameter at the level of the HME filter is designed to be slightly larger than the inner diameter downstream of the HME filter in order to accommodate an HME filter with a correspondingly large diameter or outer diameter. This allows for the desire for a sufficient buffering effect caused by the HME filter and the desire for a space-saving and minimally delayed transfer of the measured gas to the sensor unit.

[0057] According to obtaining device of the present invention, the internal diameter of bifurcated line can have the value in the scope between 2mm and 4mm on the level of the first HME filter, and the internal diameter of the bifurcated line in the downstream of the first HME filter can have the value in the scope between 0.5mm and 2mm.In the extensive test under framework of the present invention, verified, with regard to the diameter in the scope between 2mm and 4mm, the possible condensate in the upstream of the HME filter is relatively not a problem.In robust bifurcated line and nevertheless as far as possible dead space or correspondingly low measurement hysteresis, the diameter in the scope between 0.5mm and 2mm in the downstream of the HME filter has been verified to be favourable compromise.Bifurcation line or hose line can be designed for, under the situation of the volumetric flow in the scope between 50ml / min and 70ml / min, be set up at the flow velocity in the scope between 1m / s and 1.5m / s.

[0058] In addition, in the acquisition device according to the present invention, at least one HME filter can be designed as a hose insert in the end section of the main line side of the branch line, wherein, when observing the flow direction of the gas passing through the branch line, the branch line has an internal diameter larger in the region upstream of at least one HME filter than in the downstream of at least one HME filter. Therefore, the condensate upstream of at least one HME filter can be prevented from causing the blocking of the branch line, and in the downstream of at least one HME filter, a desired compromise can be achieved in the branch line and the least possible dead space or correspondingly low measurement hysteresis. It has been proved to be advantageous that the internal diameter of the branch line upstream of at least one HME filter has a value in the scope between 1.5mm and 4mm, and the internal diameter of the branch line downstream of at least one HME filter has a value in the scope between 0.5mm and 2mm. If the region upstream of the HME filter and at the level of the HME filter has the same internal diameter, then the advantage in simply processing the branch line can be obtained. Thus, for example, the hose line of the branch line can be configured with an internal diameter that has the same value from the area upstream of the HME filter in the sensor-side end section to the area in which the HME filter is located when it is designed in the hose line, and only has a smaller internal diameter downstream of the HME filter than upstream of the HME filter or in the area of ​​the HME filter. The same situation can be configured in a similar manner with respect to the external diameter of such a hose line. It is also possible that the area upstream of the HME filter, or the corresponding internal volume, of the hose line of the branch line has a smaller internal diameter than in the area of ​​the HME filter, and preferably, nevertheless, is larger than in the area downstream of the HME filter. Therefore, the inner diameter of the hose line described above can remain constant from the area upstream of the HME filter toward the area where the HME filter is designed in the hose line, and decrease from the area where the HME filter is designed in the hose line toward the area downstream of the HME filter, or increase from the area upstream of the HME filter toward the area where the HME filter is designed in the hose line, and decrease again from the area where the HME filter is designed in the hose line toward the area downstream of the HME filter.

[0059] In the acquisition device according to the present invention, at least one HME filter can also have a length in the range between 8mm and 20mm and a width in the range between 2mm and 6mm. In particular, at least one HME filter has a length in the range between 10mm and 15mm and a width in the range between 3mm and 5mm. According to the present invention, at least one HME filter is only used to flow through with measured gas or suction flow as much as possible and can therefore be kept relatively small. Known and previously used HME filters in the main pipeline are designed for patient gas flows up to 180l / min. According to the present invention, at least one HME filter is designed to flow through with measured gas, for example, in the range between 30ml / min and 100ml / min, in particular in the range between 40ml / min and 70ml / min. Therefore, the branch line can be correspondingly smaller, material-saving, space-saving and cost-effectively designed. At least one HME filter is preferably cylindrically designed and is designed with a length in the range between 8mm and 20mm and a diameter in the range between 2mm and 6mm.

[0060] According to another design variant of the present invention, it is possible for the branching line in the ascertainment device to comprise a hose line having a length in the range of between 80 cm and 150 cm. Experiments within the framework of the present invention have shown that an effective buffering effect with respect to the desired temperature and / or humidity balance can be achieved with this hose length. In particular, the hose line has a length in the range of between 90 cm and 110 cm. Preferably, over a hose line length in the range of between 80 cm and 120 cm, the hose line has the aforementioned inner diameter in the range of between 0.5 mm and 2 mm.

[0061] Furthermore, in the ascertainment device according to the invention, the branch line can include a hose line made of silicone or at least partially of silicone. Tests within the framework of the invention have shown that the use of silicone hoses in the branch line results in a reverse drying effect on the measured gas, which leads to further damping and / or smoothing of humidity fluctuations.

[0062] In the ascertainment device according to the invention, it can further be advantageous if the branch line comprises a hose line having a PVC coating on its outer circumference. The PVC coating can be used to simply and cost-effectively prevent environmental influences on the measured gas that could affect the measurement result. The PVC coating preferably has a thickness in the range of 0.1 mm to 0.4 mm.

[0063] In a further embodiment of the ascertainment device according to the present invention, it is possible for the branch line to have a Luer Lock connector for establishing a fluid connection with the main line. This allows the branch line to be connected or coupled to the main line and / or a connector section of the main line particularly quickly and easily. A corresponding mating Luer connector can be provided on the main line of the medical system, the breathing mask, and / or the exhalation valve on the breathing mask for corresponding connector connections between the main line and the branch line, between the breathing mask and the branch line, and / or between the exhalation valve and the branch line.

[0064] In a preferred embodiment of the ascertainment device according to the present invention, the at least one HME filter can also comprise a microporous plastic foam. This allows for a particularly reliable balancing effect on the temperature and / or humidity in the measured gas. The at least one HME filter can comprise a particularly porous, salt-coated plastic foam. Consequently, the at least one HME filter can have a humidification efficiency of approximately 30 mg of water per liter of the inhaled gas.

[0065] In the ascertainment device according to the present invention, the fluid delivery unit can also include a piezoelectric pump. As previously mentioned, when using a piezoelectric pump, an associated lookup table can be used to quickly, simply, and nonetheless accurately ascertain the carbon dioxide concentration and / or to quickly and reliably generate a volume flow rate and / or a gas pressure of the measurement gas that is as uniform as possible. Furthermore, the ascertainment device according to the present invention can be configured to ascertain the carbon dioxide concentration in the measurement gas from the medical device during pressure-controlled artificial respiration of a person using the medical device, wherein the setting unit is configured to adaptively set the fluid delivery unit using the airway pressure in the main line that is set due to the pressure-controlled artificial respiration of the person. "The setting unit is configured to adaptively set the fluid delivery unit using the airway pressure in the main line that is set due to the pressure-controlled artificial respiration of the person" can be understood to mean that the setting unit uses the set airway pressure in the main line to adaptively set the fluid delivery unit, or adaptively sets the fluid delivery unit based on the set airway pressure.

[0066] In another embodiment of the present invention, the ascertainment device can be configured to ascertain the carbon dioxide concentration in the measurement gas from the medical device during volume-guided artificial respiration of a person by the medical device, wherein the setting unit is configured to adaptively set the fluid delivery unit using the airway pressure in the main line resulting from the volume-guided artificial respiration of the person. “The setting unit is configured to adaptively set the fluid delivery unit using the airway pressure in the main line resulting from the volume-guided artificial respiration of the person” can be understood to mean that the setting unit uses the airway pressure in the main line resulting from the volume-guided artificial respiration of the person to adaptively set the fluid delivery unit, or adaptively sets the fluid delivery unit based on the resulting airway pressure.

[0067] According to another aspect of the present invention, a medical device can be used for artificial respiration of a person. The medical device comprises a main line for conducting inhaled gas and for conducting exhaled gas, and a determination device, as described in detail above, for determining the carbon dioxide concentration in the measured gas from the main line. The medical device according to the present invention thus also offers the advantages described above. The medical device can comprise a breathing mask and / or an exhalation valve, wherein the main line can be configured to direct inhaled gas toward the breathing mask and to direct exhaled gas away from the breathing mask and / or toward the exhalation valve. The branch line can be designed to branch the measured gas from the main line through the breathing mask and / or through the exhalation valve. Thus, in the medical device according to the present invention, the exhalation valve can be arranged at the breathing mask, wherein the main line extends from the exhalation region of the breathing mask toward the exhalation valve, and there, i.e., in and / or at the exhalation valve, the branch line on the main line is designed to branch the measured gas from the main line. Furthermore, the medical device can include a fluid delivery unit, in particular a pump, such as a piezoelectric pump, for conveying, pumping, and / or aspirating the measurement gas or the inhaled gas and the expired gas from the main line into the branch line. The medical device and / or the ascertainment device are each configured and designed to carry out the method described above.

[0068] In the medical device according to the present invention, the main line can include an inhalation gas line section for conducting inhalation gas and a total gas line section for conducting inhalation gas and exhalation gas, wherein the branching line is designed to branch off the measurement gas from the total gas line section. In other words, the measurement gas can branch off from a portion of the main line through which both inhalation gas and exhalation gas are conducted during operation of the medical device. In particular, the carbon dioxide concentration in the measurement gas is determined or measured using the carbon dioxide difference between the inhalation gas and the exhalation gas, and calculated using a computing unit of the medical device.

[0069] In the medical device according to the present invention, at least one HME filter can be located within the main gas line section. That is, the branch line is not only connected and / or coupled to the main line, but also extends into the main line, more precisely into the main gas line section. The HME filter and / or the branch line with the HME filter arranged therein can be arranged and / or guided within the main line. The outer peripheral surface of the branch line can be spaced apart from the inner peripheral surface of the main line in the region where the HME filter is designed in the branch line and / or where it is located. Thus, a particularly compact and yet functional construction can be achieved. In addition, the main line can extend toward the exhalation valve of the medical device or extend through at least a portion of the exhalation valve. In this case, at least one HME filter can also be considered to be designed within the exhalation filter. This also results in a particularly compact and robust construction. In particular, the HME filter can be effectively protected from environmental influences within the main line and / or the exhalation valve. In the medical device according to the present invention, at least a portion of the branch line can extend from a location within the main line, from the main gas line section, into the inhalation gas line section. In other words, the branch line can be guided within the main line or through the main line volume of the main line designed for guiding inhalation gas. In other words, the branch line can be integrated into at least a portion of the main line and / or guided therein. This allows for a particularly space-saving medical device.

[0070] According to the medical appliance of the present invention, an exhalation valve is designed in the total gas line section so that the exhaled gas from the medical appliance is discharged into the surrounding environment of the medical appliance. In this medical appliance, at least one HME filter can be designed in the exhalation valve. Such a design variant can also be realized relatively compactly. With regard to the HME filter that is integrated into the exhalation valve, when assembling the medical appliance, only the branch line needs to be connected to the exhalation valve and subsequently guided toward the sensor unit. The branch line, for example, in the form of a simple hose line, can be replaced quickly, simply and cost-effectively when necessary. "Position within the exhalation valve" means that at least one HME filter and / or a part of the branch line with at least one HME filter arranged therein and / or therein is arranged in the valve volume of the exhalation valve, and the exhaled gas of the main line and the inhaled gas flow through this valve volume. The branch line is preferably connected with the exhalation valve for branching the measured gas from the main line. For this purpose, the branch line can have a branch connection, and the exhalation valve can have a counter-branch connection for producing a fluid-tight connection with the branch connection.

[0071] The medical device described herein is preferably provided and / or designed in the form of a ventilator. Therefore, a "medical device" can be understood as a medical device for artificial respiration of a person, in particular a patient. In addition, the medical device can also be configured in the form of an anesthesia machine. The ventilator can preferably be configured and / or designed in the form of an emergency ventilator, a ventilator for use in an intensive care unit, a home ventilator, a mobile ventilator, and / or a neonatal ventilator.

[0072] According to another aspect of the present invention, a setting unit is provided for use in an ascertainment device as described above and / or in a medical device as described above. The setting unit is configured and designed to adaptively set the fluid conveying unit, taking into account the airway pressure in the main line, in order to produce a uniform volume flow and / or gas pressure of the measurement gas in the branch line to the sensor unit during the inspiration and expiration phases.

[0073] Furthermore, within the scope of the present invention, a computer program product is proposed. The computer program product includes commands that, when executed on a computer, drive the computer to perform the method described above. The computer program product can be implemented as computer-readable instruction code in any suitable programming language, such as Java, C++, C#, and / or Python. The computer program product can be stored on a computer-readable storage medium, such as a data disk, a removable drive, volatile or non-volatile memory, or an internal memory / processor. The instruction code can program a computer or other programmable device, such as a controller and / or a setting unit, to perform the desired functions. Furthermore, the computer program product can be made available on a network, such as the Internet, from which it can be downloaded by a user as needed. The computer program product can be implemented not only by software but also by one or more specialized electronic circuits, that is, in hardware, or in any hybrid form, that is, by software and hardware components. Another aspect of the present invention relates to a storage device on which such a computer program product is stored. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Further measures for improving the invention are shown below in the description of various exemplary embodiments of the invention schematically shown in the drawings. All features and / or advantages arising from the claims, the description or the drawings, including structural details and spatial arrangements, can be important to the invention both individually and in various combinations. The following are schematically shown:

[0075] Figure 1 shows a medical device with an ascertainment device according to a first embodiment of the present invention,

[0076] Figure 2 A storage device having a computer program product stored thereon is shown,

[0077] Figure 3 shows a medical device with an ascertainment device according to a second embodiment of the present invention,

[0078] Figure 4 A flow chart is shown for explaining a method according to a preferred embodiment of the present invention.

[0079] Figure 5 A characteristic diagram is shown for illustrating the airway pressure during artificial respiration with a uniform volume flow by actuating the fluid delivery unit according to the invention,

[0080] Figure 6 shows a lookup table for a piezoelectric pump,

[0081] Figure 7 A characteristic diagram is shown for explaining the adaptive setting of the fluid delivery unit during pressure-guided artificial respiration by the medical device according to the invention, and

[0082] Figure 8 A characteristic diagram is shown to illustrate the adaptive setting of the fluid delivery unit during volume-guided artificial respiration by means of the medical device according to the invention. DETAILED DESCRIPTION

[0083] Elements having the same function and mode of operation are respectively provided with the same reference numerals in the figures.

[0084] Figure 1A medical device 12 in the form of a ventilator for artificially breathing a person 13 is shown according to a first embodiment. The medical device 12 includes a breathing mask 20 and a main line 15 for conducting inhalation gas toward the breathing mask 20 and for conducting exhalation gas away from the breathing mask 20. The main line 15 has an inhalation gas line section 21 and an exhalation gas line section 23. A main pump 32 is provided in the inhalation gas line section 21 for supplying inhalation gas to the breathing mask 20 or the person 13. An exhalation valve 25 is provided downstream of the main pump 32, viewed in the flow direction of the inhalation gas. Upstream of the exhalation valve 25 and downstream of the main pump 32, only inhalation gas is conducted in the inhalation gas line section 21. In an exhalation valve 25, through which the main line 15 also extends, the inhaled gas is guided toward the breathing mask 20, and the exhaled gas is guided away from the breathing mask 20 and, via the exhalation valve 25, into the surroundings of the medical device 12. A main gas line section 22 is provided between the exhalation valve 25 and the breathing mask 20, in which the inhaled gas is guided during the inhalation phase and the exhaled gas during the exhalation phase.

[0085] The illustrated medical device 12 also has a determination device 10 for determining the carbon dioxide concentration in the measurement gas from the medical device 12 or from a main line 15 during artificial respiration (Beatmung) of a person 13 performed via the medical device 12. The determination device 10 has a branching line 14 with a first HME filter 16 and a second HME filter 17 for filtering the branched measurement gas. The determination device 10 also has a sensor unit 11 for determining the carbon dioxide concentration in the measurement gas. The branching line 14 is configured to branch the measurement gas from the main line 15 of the medical device 12 toward the sensor unit 11 during the inhalation phase of the person 13 as inhaled gas and during the exhalation phase of the person 13 as exhaled gas. Taking into account the flow direction of the branched and drawn-in measurement gas, a first HME filter 16 is arranged on the main gas line section 22 directly upstream of the sensor unit 11, and taking into account the flow direction of the branched and drawn-in measurement gas, a second HME filter 17 is arranged on the sensor unit 11 directly upstream of the sensor unit 11. Both HME filters 16, 17 are cylindrical in design and each have a length of 13 mm and a diameter of 3 mm.

[0086] To draw the measured gas from the main line 15 or from the main gas line section 22, the ascertainment device 10 has a fluid delivery unit 24 in the form of a piezoelectric pump. The fluid delivery unit 24 is arranged downstream of the sensor unit 11. The HME filters 16 and 17 shown each comprise a microporous plastic foam for filtering the measured gas or for achieving the desired buffering or balancing function with respect to temperature and humidity differences occurring in the measured gas.

[0087] To determine the carbon dioxide concentration in the measured gas, the thermal conductivity of the exhaled gas is measured in the sensor unit 11. This measurement is achieved via a microstructured heating element on the thin membrane of the sensor unit. A thermophilic device is located near the heating element and measures the superheat temperature of the gas near the heating element relative to the silicon frame of the membrane. Further details on this can be found in German patent application DE 10 2010 047 159 A1.

[0088] Furthermore, the medical device 12 or the ascertainment device 10 includes a setting unit 26, which is configured and designed to adaptively set the fluid delivery unit 24, taking into account the airway pressure in the main line 15, to produce a volume flow rate and a gas pressure that are as uniform as possible for the measurement gas in the branch line 14 of the sensor unit 11 during the inspiration and expiration phases. The setting unit 26 can be considered a controller for the medical device 12. The setting unit 26 is in signal communication with the main pump 32 and with the fluid delivery unit 24 for setting or controlling them. Furthermore, the ascertainment device 10 includes an airway pressure sensor 27 for measuring the airway pressure in the main line 15. The setting unit 26 is configured and designed to adaptively set the fluid delivery unit 24, taking into account the airway pressure in the main line 15 measured by the airway pressure sensor 27, to produce a volume flow rate and a gas pressure that are as uniform as possible for the measurement gas in the branch line 14 of the sensor unit 11.

[0089] A computer program product 29 is installed in the setting unit 26, and the computer program product includes commands that, when the computer program product 29 is executed, drive it through the setting unit 26 to implement the reference Figure 4 The method described is implemented. Figure 2 2 shows a memory device 30 on which such a computer program product 29 is stored.

[0090] Figure 3 A medical device 12 according to a second embodiment is shown. Figure 3 In the medical device 12 shown in FIG, the exhalation valve 25 is fastened to the respiratory mask 20 . Figure 3 The exhalation valve 25 shown in FIG further comprises a first HME filter 16 integrated into the exhalation valve 25. The first HME filter 16 is arranged in accordance with Figure 3 It is designed directly on the hose line of the branch line 14. Therefore, the branch line 14 is connected to the exhalation valve 25 by means of the hose line and forms a fluid connection to the first HME filter 16 there, or enables a fluid connection from the main line 15 through the first HME filter 16 to the sensor unit 11. For this purpose, the exhalation valve 25 has a valve connector 31 in the form of a Luer lock connector for connecting the branch line 14 or the hose line.

[0091] Figure 4 A flow chart is shown for explaining a method for determining the carbon dioxide concentration in a measurement gas. In a first step S1, measurement gas is first branched off from a main line 15 of a medical device 12, as described above, during the inhalation phase of a person 13 connected to the medical device 12 as inhaled gas, and during the exhalation phase of the person 13 as exhaled gas, via a branch line 14 toward a sensor unit 11. The measurement gas is then conveyed or drawn from the main line 15 via the branch line 14 toward the sensor unit 11 by means of a fluid conveying unit 24. In a second step S2, which is partially performed simultaneously with the first step S1, the fluid conveying unit 24 is adaptively set, taking into account the airway pressure in the main line 15, to produce a volume flow of measurement gas and a gas pressure that is as uniform as possible in the branch line 14 toward the sensor unit 11 during the inhalation and exhalation phases. Here, the airway pressure in main line 15 is measured by airway pressure sensor 27, and, using the measured airway pressure in main line 15, fluid conveying unit 24 is adaptively set to produce a uniform volume flow and uniform gas pressure of the measured gas in branch line 14 to sensor unit 11. During this process, in a third step S3, the carbon dioxide concentration in the measured gas is ascertained using sensor unit 11. More precisely, the thermal conductivity of the measured gas is measured by sensor unit 11 in order to determine the carbon dioxide concentration based on the above-described method.

[0092] Figure 5 Characteristic diagrams are shown to illustrate the airway pressure during artificial respiration with a uniform volume flow by controlling the fluid delivery unit 24 as described above. More precisely, diagram A shows a typical course of the airway pressure. Graph B shows how the fluid delivery unit 24 is controlled or set to produce the most uniform possible volume flow, as shown in diagram C.

[0093] Figure 6A lookup table 28 is shown, which, when used, produces a volume flow of the measured gas that is as uniform as possible and a gas pressure that is as uniform as possible in the branch line 14 of the sensor unit 11. If a straight line 33 at 50 ml / min is plotted in the lookup table 28, it is immediately apparent which gas pressure is generated at which operating voltage of the fluid conveying unit 24. This process can be automated in the proposed method using the setting unit 26.

[0094] Figure 7 Characteristic diagrams are shown to illustrate the adaptive setting of the fluid delivery unit 24 during pressure-controlled artificial respiration by the medical device 12. Characteristic diagram A shows the volume over time. Characteristic diagram B shows the associated volume flow over time. Characteristic diagram C shows the associated pressure over time. Characteristic diagram D shows the varying volume flow for a uniform operation of the fluid delivery unit 24. Characteristic diagram E shows the varying operating power of the fluid delivery unit 24 over time, which results from the adaptive setting of the fluid delivery unit 24 described above. Characteristic diagram F shows the uniform volume flow resulting from the adaptive setting of the fluid delivery unit 24.

[0095] Figure 8 Characteristic diagrams are shown to illustrate the adaptive setting of the fluid delivery unit during volume-guided artificial respiration using the medical device according to the present invention. Characteristic diagram A plots the volume over time. Characteristic diagram B plots the associated volume flow over time. Characteristic diagram C plots the associated pressure over time. Characteristic diagram D shows the varying volume flow for a uniformly operating fluid delivery unit 24. Characteristic diagram E shows the varying operating power of the fluid delivery unit 24 over time, which is caused by the adaptive setting of the fluid delivery unit 24 described above. Characteristic diagram F shows the uniform volume flow, which is produced by the adaptive setting of the fluid delivery unit 24. In order to determine the carbon dioxide concentration in the measurement gas during volume-guided artificial respiration of a person by means of the medical device 12 , the fluid delivery unit 24 is adaptively set using the airway pressure in the main line 15 resulting from the volume-guided artificial respiration of the person 13 in order to generate a uniform volume flow in the branch line 14 to the sensor unit 11 .

[0096] In addition to the embodiments shown, the present invention also allows for other design principles. That is, the present invention should not be considered restrictively with respect to the exemplary embodiments illustrated in the accompanying drawings. Thus, in the method described above, the fluid delivery unit 24 can be adaptively set to produce a uniform volume flow and / or uniform gas pressure of the measurement gas in the branch line 14 of the sensor unit 11, taking into account only the airway pressure in the main line 15 during the inhalation phase of artificial respiration or taking into account only the airway pressure in the main line 15 during the exhalation phase of artificial respiration. In addition, in the method described above, the fluid delivery unit 24 can be operated at a constant power during the exhalation phase of artificial respiration, and during the inhalation phase of artificial respiration, the fluid delivery unit can be adaptively set to produce a uniform volume flow and / or uniform gas pressure of the measurement gas in the branch line 14 of the sensor unit 11, taking into account the airway pressure during the inhalation phase of artificial respiration. Furthermore, the fluid delivery unit 24 can be adaptively set during the expiratory phase of artificial respiration, taking into account the airway pressure during the expiratory phase of artificial respiration, and can be deactivated during the inspiratory phase of artificial respiration in order to generate a uniform volume flow and / or a uniform gas pressure of the measuring gas in the branch line 14 toward the sensor unit 11.

[0097] List of reference numerals:

[0098] 10 Obtaining Equipment

[0099] 11 Sensor unit

[0100] 12 Medical devices

[0101] 13 people

[0102] 14 Branch pipeline

[0103] 15 Main pipeline

[0104] 16 HME filter

[0105] 17 HME filter

[0106] 20 breathing masks

[0107] 21 Intake gas pipeline section

[0108] 22 Total gas pipeline section

[0109] 23 Exhaled gas pipeline section

[0110] 24 Fluid transport unit

[0111] 25 Exhalation valve

[0112] 26 Setting unit

[0113] 27 Airway pressure sensor

[0114] 28 Lookup Table

[0115] 29 Computer program products

[0116] 30 Storage Devices

[0117] 31 Valve connector

[0118] 32 Main pump

[0119] 33 straight line.

Claims

1. A method for determining the carbon dioxide concentration in a measurement gas, comprising the following steps: - branching the measuring gas from the main line (15) of the medical device (12) via a branch line (14) towards the sensor unit (11) during the inhalation phase of a person (13) connected to the medical device (12) as inhaled gas and during the exhalation phase of the person (13) as exhaled gas, - conveying the measuring gas from the main line (15) to the sensor unit (11) via the branch line (14) by means of a fluid conveying unit (24), - adaptively setting the fluid delivery unit (24) taking into account the airway pressure in the main line (15) in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) to the sensor unit (11) during the inspiration phase and the expiration phase, and - determining the carbon dioxide concentration in the measurement gas by means of the sensor unit (11), in, The fluid delivery unit (24) for delivering the measuring gas from the main line (15) through the branch line (14) toward the sensor unit (11) has a piezoelectric pump, and the operating voltage of the piezoelectric pump is adaptively set taking into account the airway pressure and using a lookup table (28) to generate a uniform volume flow and / or gas pressure of the measuring gas in the branch line (14) toward the sensor unit (11).

2. The method according to claim 1, It is characterized in that The airway pressure in the main line (15) is measured by an airway pressure sensor (27), and the fluid conveying unit (24) is adaptively set using the measured airway pressure in the main line (15) to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) toward the sensor unit (11).

3. The method according to claim 1 or 2 for determining the carbon dioxide concentration in the measurement gas during pressure-induced artificial respiration of the person (13) by means of the medical device (12), wherein: The fluid conveying unit (24) is adaptively set using the airway pressure in the main line (15) which is set due to pressure-guided artificial respiration of the person (13) in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) to the sensor unit (11).

4. The method according to claim 1 or 2 for determining the carbon dioxide concentration in the measurement gas during volume-guided artificial respiration of the person (13) by means of the medical device (12), wherein: The fluid conveying unit (24) is adaptively set using the airway pressure in the main line (15) caused by volume-guided artificial respiration of the person (13) in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) to the sensor unit (11).

5. The method according to claim 1 or 2, It is characterized in that The fluid delivery unit (24) is adaptively set, taking into account only the airway pressure in the main line (15) during the inspiration phase of artificial respiration or taking into account only the airway pressure in the main line (15) during the expiration phase of artificial respiration, in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) to the sensor unit (11).

6. The method according to claim 1 or 2, It is characterized in that The fluid delivery unit (24) is operated at a constant power during the exhalation phase of artificial respiration and is adaptively set during the inhalation phase of the artificial respiration taking into account the airway pressure during the inhalation phase of the artificial respiration in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) toward the sensor unit (11).

7. The method according to claim 1 or 2, It is characterized in that The fluid delivery unit (24) is adaptively set during the expiration phase of artificial respiration taking into account the airway pressure during the expiration phase of the artificial respiration and is deactivated during the inspiratory phase of the artificial respiration in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) toward the sensor unit (11).

8. A determination device (10) for determining the carbon dioxide concentration in a measurement gas from a medical device (12) during artificial respiration of a person (13) by means of the medical device (12), the determination device comprising: - a sensor unit (11) for determining the carbon dioxide concentration in the measurement gas, a branch line (14) for branching the measurement gas from the main line (15) of the medical device (12) towards the sensor unit (11) as inhaled gas during the inhalation phase of the person (13) and as exhaled gas during the exhalation phase of the person (13), a fluid conveying unit (24) having a piezoelectric pump for conveying the measuring gas from the main line (15) through the branch line (14) toward the sensor unit (11), and - a setting unit (26) configured and designed to adaptively set the piezoelectric pump, taking into account the airway pressure in the main line (15) and using a look-up table (28), in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) to the sensor unit (11) during the inspiration phase and the expiration phase.

9. The determination device (10) according to claim 8, It is characterized by An airway pressure sensor (27) for measuring the airway pressure in the main line (15), wherein the setting unit (26) is configured and designed to adaptively set the fluid conveying unit (24) taking into account the airway pressure measured in the main line (15) in order to generate a uniform volume flow and / or gas pressure of the measuring gas in the branch line (14) toward the sensor unit (11).

10. The determination device (10) according to claim 8 or 9, It is characterized in that At least one HME filter (16) is provided in and / or at the branch line (14).

11. The determination device (10) according to claim 10, It is characterized in that The at least one HME filter (16) has a length in the range between 8 mm and 20 mm and a width in the range between 2 mm and 6 mm.

12. The ascertainment device (10) according to claim 8 or 9 for ascertaining the carbon dioxide concentration in the measurement gas from the medical device (12) during pressure-induced artificial respiration of a person (13) by means of the medical device (12), It is characterized in that The setting unit (26) is configured to adaptively set the fluid delivery unit (24) using the airway pressure in the main line (15) that is set as a result of pressure-controlled artificial respiration of a person.

13. The ascertainment device (10) according to claim 8 or 9, for ascertaining the carbon dioxide concentration in a measurement gas from a medical device (12) during volume-guided artificial respiration of a person (13) by means of the medical device (12), It is characterized in that The setting unit (26) is configured to adaptively set the fluid delivery unit (24) using the airway pressure in the main line (15) resulting from volume-guided artificial respiration of the person.

14. A medical device (12) for artificial respiration of a person (13), comprising: a main line (15) for conducting the inhaled gas and for conducting the exhaled gas, and The ascertainment device (10) according to any one of claims 8 to 13, for ascertaining the carbon dioxide concentration in the measurement gas from the main line (15).

15. The medical device (12) according to claim 14, It is characterized in that The main line (15) comprises an inhalation gas line section (21) for guiding inhalation gas and a total gas line section (22) for guiding the inhalation gas and exhalation gas, wherein the branch line (14) is designed to branch off the measurement gas from the total gas line section (22).

16. The medical device (12) according to claim 15, It is characterized in that An exhalation valve (25) for discharging exhaled gas from the medical device (12) into the surroundings of the medical device (12) is provided in the total gas line section (22), wherein at least one HME filter (16) is provided in the exhalation valve (25).

17. The medical device (12) according to claim 16, It is characterized in that The branch line (14) for branching the measurement gas from the main line (15) is connected to the exhalation valve (25).

18. The medical device (12) according to claim 14 or 15, It is characterized in that The medical device (12) is designed as a ventilator.

19. A setting unit (26) for use in a determination device (10) according to any one of claims 8 to 13 and / or a medical device (12) according to any one of claims 14 to 18, the setting unit being configured and designed to adaptively set the fluid delivery unit (24) taking into account the airway pressure in the main line (15) in order to generate a uniform volume flow and / or gas pressure of the measurement gas in the branch line (14) toward the sensor unit (11) during an inhalation phase and an exhalation phase.

20. Computer program product (29) comprising commands which, when the computer program product (29) is executed by a computer, drive the computer to carry out the method according to any one of claims 1 to 7.

21. A memory device (30) having a computer program product (29) according to claim 20 stored thereon.

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