Device and method for locating leaks

Abstract

The present invention relates to a monitoring method and a monitoring device that can be used during a medical treatment of a patient (Pt). A patient-fluid guide unit (32, 33) is established between the medical device (1) and the patient-side coupling unit (21). The gas sample (Gp) diverges from the patient-fluid conducting unit at a diverging point (34) and is conducted to the sensor assembly (50). The sensor assembly measures a portion of a component of the gas sample. It is determined whether an indicator (L) for a leak between the bifurcation point and the measurement position in the sensor assembly occurs. The route from the bifurcation point to the measurement position is divided into at least two sections. For each section, an aerodynamic resistance is specified, which is dependent on the volumetric flow through the section. If an indicator for a leak is found, which section the leak occurs is identified. The aerodynamic resistance and the pressure difference (Pcell-Paw) between the bifurcation point and the measurement point are used for this purpose.

Description

Field of the Invention

[0001] The present invention relates to a monitoring method and a monitoring device which can be used during the medical treatment of a patient, in particular during artificial respiration. A patient-fluid guiding unit establishes a fluid connection between a medical device and a coupling unit on the patient side. A gas mixture is guided from the medical device to the coupling unit on the patient side and / or in the reverse direction through the patient-fluid guiding unit. Furthermore, the present invention also relates to a measuring method which includes such a monitoring method, a measuring system with such a monitoring device, and a treatment assembly with such a measuring system. Background Art

[0002] During medical treatment, a gas sample is branched off from the patient-fluid guiding unit and guided to a measuring system with a sensor assembly, wherein the sensor assembly analyzes the gas sample. The sensor assembly analyzes the gas sample and in particular measures the fraction of at least one component of the gas sample, such as the fraction of oxygen and / or carbon dioxide and / or anesthetic.

[0003] A leak may suddenly occur in the measuring system. Ambient air can flow through the leak into the measuring system. Usually, ambient air has other chemical components different from the gas sample to be investigated. Therefore, during the medical treatment of a patient, the ambient air flowing through the leak to the sensor assembly may cause the measurement of the sensor assembly to be incorrect. This is undesirable. Therefore, it is desirable to be able to detect such a leak reliably and quickly. Summary of the Invention

[0004] The present invention is based on the following task: to provide a monitoring method and a monitoring device which can monitor a measuring system for the occurrence of a leak, wherein the measuring system can analyze a gas sample from a patient-fluid guiding unit, and wherein the monitoring method and the monitoring device should provide greater reliability in monitoring the measuring system compared to known methods and devices.

[0005] This task is solved by a monitoring method with the features of claim 1 and a monitoring device with the features of claim 8. Advantageous designs are described in the dependent claims. Advantageous designs of the monitoring method according to the present invention (wherever meaningful) are also advantageous designs of the monitoring device according to the present invention, and vice versa.

[0006] Note: The order in which the method steps of the claims are listed does not necessarily specify the order in which the steps are carried out when the method is actually executed.

[0007] The measurement system monitored according to the invention is designed for use in the medical treatment of a patient, in particular artificial respiration. At least temporarily during this medical treatment, the patient-fluid guiding unit establishes a fluid connection between the patient-side coupling unit and the medical device. The medical device is in particular a respiratory device which generates and discharges a breathable gas mixture for artificial respiration. The patient-side coupling unit is designed for arrangement in and / or at the patient's body. A breathing mask and a tube (Tubus) are two examples of the patient-side coupling unit.

[0008] In this application, the breathable gas mixture typically contains oxygen and optionally at least one anesthetic and / or gaseous drug. In this application, the discharged gas mixture is guided through the patient-fluid guiding unit to the patient-side coupling unit, wherein the patient-side coupling unit is arranged in and / or at the patient's body during the medical treatment. Optionally, a breathing circuit is established.

[0009] It is also possible that the patient inhales the breathable gas mixture from a stationary or mobile supply unit solely based on their own breathing activity. In this application, the supply unit acts as the medical device. The gas mixture flows from the supply unit through the patient-fluid guiding unit to the patient-side coupling unit. The medical device can also be a device for investigating the gas mixture exhaled by the patient.

[0010] The "fluid guiding unit" is understood as a component which is capable of guiding a fluid along a predefined trajectory, wherein the trajectory is predefined by the structure and / or arrangement of the fluid guiding unit. Ideally, the fluid guiding unit prevents the guided fluid from leaving the trajectory. A hose and a tube are two examples of the fluid guiding unit.

[0011] Such a measurement system can be automatically monitored by means of the monitoring method according to the invention and the monitoring device according to the invention. During the period in which the patient-fluid guiding unit permanently or at least temporarily establishes a fluid connection between the patient-side coupling unit and the medical device, the monitoring method is carried out and the monitoring device can be applied.

[0012] The invention can be used for the medical treatment of a patient. Generally, the measurement system is used to determine at least one characteristic of a gas sample, wherein the gas sample has branched off from or has been branched off from the gas mixture during the flow of the gas mixture through the patient-fluid guiding unit, preferably repeatedly branched off. The sought characteristic of the gas sample is in particular the presence or share (concentration) of a component (such as oxygen or carbon dioxide or an anesthetic) of the gas sample, the corresponding shares of multiple components or the pressure or temperature or humidity of the gas sample.

[0013] The sensor assembly of the measurement system is capable of measuring at least one property of the measurement-gas mixture, more precisely preferably while the measurement-gas mixture is in the sensor assembly. The sought property of the measurement-gas mixture is in particular the respective share (respective concentration) of at least one component of the measurement-gas mixture, but can also be, for example, pressure or temperature or humidity. Optionally, the sensor assembly is capable of measuring at least two different properties of the measurement-gas mixture, in particular the respective shares of two different components.

[0014] The measurement-gas mixture comprises a branched and to-be-investigated gas sample. If there is no leak, the measurement-gas mixture is usually identical to the branched gas sample. In the case of a leak, the measurement-gas mixture usually consists of the branched gas sample and the gas mixture flowing from the surroundings through the leak to the sensor assembly.

[0015] Note: Using the following expression, the sensor is capable of measuring a physical parameter, such as the share or concentration of a component in a gas mixture, or the pressure, temperature or thermal conductivity of a gas mixture. This expression means the following: The sensor directly measures the physical parameter or another physical parameter, which is related to the physical parameter to be measured and is thus a parameter for the physical parameter to be measured. It is possible to find out which value the physical parameter takes at a specific location. The measurement location at which the related other parameter is measured can deviate from this location. The measurement of the parameter or each parameter to be corrected provides a value for the sought physical parameter to be measured.

[0016] A fluid connection is established or can be established between the sensor assembly and the branching point by means of the sensor-fluid guiding unit. The measurement system is capable of branching off the gas sample at the branching point from the patient-fluid guiding unit and thus from the gas mixture and guiding it through the sensor-fluid guiding unit to the sensor assembly. It is possible that the sensor-fluid guiding unit guides through the sensor assembly.

[0017] In many cases, a leak in the measurement system causes a mixture of the gas sample and ambient air or other gas mixtures to reach the sensor assembly in the surroundings of the measurement system. In the case of a leak, such a mixture of the gas sample and ambient air acts as the measurement gas mixture. The reason for the gas mixture to reach the sensor assembly from the surroundings is as follows: Usually, a negative pressure occurs at least temporarily in the sensor-fluid guiding unit relative to the surroundings. As a result, one consequence of the leak is that the sensor assembly no longer analyzes the gas sample but rather a mixture of the gas sample and ambient air or other gas mixtures in the surroundings. Usually, the sought-after properties of the gas sample differ from the corresponding properties in the ambient air. Therefore, in the case of a leak, the measurement gas mixture no longer has the same sought-after properties as the branched-off gas sample. For example, the share of oxygen and / or the share of anesthetic in the gas sample usually differ from the oxygen share in the ambient air and are usually higher. Therefore, in many cases, the leak causes false measurement results. In particular, the leak is thus undesirable.

[0018] The pressure sensor assembly of the measurement system is capable of measuring the pressure at the branching point on the one hand and the pressure in the measurement system on the other hand. In many cases, the pressure measured at another location in the patient-fluid guiding unit is accurately consistent with the pressure at the branching point and can thus be used as the sought-after pressure at the branching point. The pressure in the measurement system is measured in the sensor-fluid guiding unit or at the measurement location. This measurement location can be located in the sensor assembly. The monitoring method according to the invention includes corresponding steps.

[0019] According to the invention, it is determined whether an indicator for a leak in the sensor-fluid guiding unit occurs. Embodiments of the design of the invention describe how to detect an indicator for a leak or determine that no indicator for a leak exists. The steps according to the invention are described below, which are carried out at least when an indicator for a leak is detected. The feature "indicator for a leak" indicates that the invention cannot rule out false alarms related to leaks in every case either.

[0020] Due to the invention, such a leak is reliably and automatically detected in many cases. Preferably, a message with the result that an indicator for a leak has been found is output in at least one form perceptible to humans. Then, the user can investigate the sensor-fluid guiding unit for the leak.

[0021] As already mentioned, the pressure in the measurement system is measured in the sensor-fluid guiding unit or at the measurement location. In addition, the pressure at the measurement bifurcation point is measured, that is, the pressure at the point where the gas sample bifurcates from the patient-fluid guiding unit. According to the invention, the route of the sensor-fluid guiding unit leading from the bifurcation point to the measurement location is divided into a sequence of sections. This sequence of sections is known from the structural design of the measurement system, is preset and includes at least two sections connected in series, preferably three sections connected in series.

[0022] For each section of the sequence of sections, a pneumatic resistance is preset respectively, more precisely: the value for the pneumatic resistance. The feature "preset" value means that this value is preset in a form that can be evaluated by a computer for the corresponding method and the corresponding device. Usually, this value is pre-measured, that is, determined empirically. It is also possible to preset and use standard values. The pneumatic resistance may vary from section to section.

[0023] When a gas or gas mixture flows through a section, due to the pneumatic resistance, a pressure drop occurs in the section. The pressure drop is the product of the pneumatic resistance of the section and the volume flow (volume flow rate) through the section. The volume flow is the volume flowing through the section per unit time. The greater the volume flow, the greater the pressure drop. Usually, the pneumatic resistance is related to the volume flow, and usually the greater the volume flow, the smaller the pneumatic resistance.

[0024] Preferably, the corresponding pneumatic resistance of the section is determined empirically in advance. Usually, it is reasonably assumed that the pneumatic resistance of the section has little relation to the chemical composition, temperature or humidity of the gas mixture flowing through the section.

[0025] The result that an indicator for a leak section is detected triggers a sequence of steps according to the invention. Through this sequence, such or at least one section of the sequence of sections that causes the indicator for the leak section can be identified. The steps of this triggered sequence are explained below.

[0026] Measure or detect the total volume flow. The total volume flow is the volume flow at which the measurement-gas mixture flows through the sensor assembly. The total volume flow is the sum of:

[0027] - the volume flow at which the gas sample bifurcates from the patient-fluid guiding unit at the bifurcation point, and

[0028] - the volume flow of gas flowing through the leak section from the surrounding environment (leak volume flow).

[0029] Therefore, the total volume flow is the volume flow of the measurement-gas mixture. If there is no leak section, the leak volume flow is equal to zero, and the gas sample usually bifurcates at the total volume flow.

[0030] Measure the actual pressure difference. This pressure difference is the difference between the pressure at the measurement location and the pressure at the bifurcation point. As mentioned above, the pressure sensor assembly is capable of measuring these two pressures. In one design, the pressure sensor assembly can measure the pressure difference without measuring the individual pressures.

[0031] Determine a measure for the relative leakage volume flow. The relative leakage volume flow is the ratio between

[0032] - the volume flow passing through and caused by the leakage to be detected, and

[0033] - the total volume flow leading to the measurement location, i.e., the volume flow of the measurement - gas mixture, where the total volume flow is measured or detected.

[0034] Thus, the relative leakage volume flow is a fraction between 0% and 100%. In the presence of a leakage, the relative leakage volume flow is greater than 0%. The determined measure for the relative leakage volume flow can be used to determine whether there is an indication for the leakage. It is also possible that the measure for the relative leakage volume flow is determined as a reaction to an indication for the leakage detected in some other way. Various designs of the present invention show different ways for determining the relative leakage volume flow.

[0035] The route from the bifurcation point to the measurement location is divided into at least two serially connected sections. If the route is divided into n sections (n >= 2), then n - 1 transition sections occur between two adjacent sections. For the said or each transition section, a transition - section pressure difference is calculated. The transition - section pressure difference is the pressure difference that would ideally occur when a leakage would occur at that transition section. The term "ideally" indicates that the calculated result usually does not exactly match the real situation. To calculate the transition - section pressure difference, on the one hand, the total volume flow through the sensor assembly and the relative leakage volume flow are used. On the other hand, the preset pneumatic resistance of the section is used.

[0036] Identify the section that leads to the detected indication for the leakage. To identify this section, on the one hand, the measured actual pressure difference is used. On the other hand, the said or each calculated transition - section pressure difference is used.

[0037] The present invention makes use of the fact that a gas sample flows through each section of the section sequence on its path from the bifurcation point to the measurement location and thus is subject to the respective pneumatic resistance of each section. In other words: the bifurcated gas sample is subject to the total pneumatic resistance of the section sequence. The total pneumatic resistance is the sum of the pneumatic resistances of the serially connected sections.

[0038] In contrast, the ambient air or other gas mixture drawn through the leak only flows through the said or each section located between the leak and the measurement location at or in the sensor-fluid guiding unit. Thus, this gas mixture is subject to a smaller pneumatic resistance than the branched gas sample, unless the leak occurs at the branching point. Therefore, with other conditions remaining the same, the closer the leak measurement location is positioned, the smaller the measured pressure difference. The closer the leak is to the measurement location, the shorter the path the gas mixture must travel from the leak to the measurement location. As mentioned above, the pressure in the measurement system is measured at the measurement location at or in the sensor-fluid guiding unit. The fact that the closer the leak is to the measurement location, the smaller the pressure difference is utilized to identify the section based on the actual pressure difference.

[0039] If such a leak is detected, the leak must be eliminated promptly. Otherwise, the patient may be medically treated in the wrong way. The present invention not only detects the presence of the leak, but additionally provides information on where the leak occurs. Due to the present invention, in many cases it is not necessary to investigate the entire measurement system for leaks. Instead, it is usually sufficient to investigate the identified section for leaks and, in particular, the transition from the identified section to the adjacent section. That is, leaks usually occur at the transition between two adjacent sections. Another way of putting it: the sections can usually be determined such that leaks occur at the transition between two adjacent sections. In many cases, this effect of the present invention reduces the time required to eliminate the leak. Thus, the present invention generally reduces the overall downtime required to find and eliminate leaks. Therefore, the present invention improves the reliability in monitoring the measurement system and thus the reliability of the measurement system itself.

[0040] The present invention does not require a sensor between the branching point and the pressure sensor in the sensor assembly. Instead, according to the present invention, the sections are determined based on the pressure difference.

[0041] In many cases, the present invention can be integrated into an existing measurement system with relatively little effort. Generally, the present invention requires

[0042] - a first pressure sensor that measures the pressure at the measurement location in the sensor assembly, and

[0043] - a second pressure sensor that measures the pressure in the patient-fluid guiding unit.

[0044] Typically, the pressure at the bifurcation point is sufficiently accurate to correspond to the pressure measured by the second pressure sensor. There are usually already two such pressure sensors, but at least the second pressure sensor exists. Usually, no additional pressure sensors or other sensors are required to implement the present invention in an existing measurement system. Thus, the present invention can typically be implemented in an existing treatment assembly by, for example, adapting the control device accordingly, in particular by running and activating the corresponding software, and then the control device implementing the software. The treatment assembly is designed for the medical treatment of a patient.

[0045] According to the present invention, the route from the bifurcation point to the measurement location is divided into at least two sections. In one implementation form, the measurement system includes a water trap, which is located between the sensor-fluid guiding unit and the sensor assembly, preferably at the inlet section of the sensor assembly. In particular, the condensed water and other liquids present or potentially present in the branched gas sample and / or the measurement-gas mixture are collected in this water trap. In particular during artificial respiration, the gas mixture flowing to the coupling unit on the patient side and thus also the gas sample has a high humidity in order not to dry out the patient's respiratory system and has a temperature higher than the ambient temperature. Therefore, the liquid usually condenses on the inner surface of the fluid guiding unit.

[0046] In the implementation form with a water trap, the route is preferably divided into three sections. The first section extends from the bifurcation point to the inlet of the water trap and includes the sensor-fluid guiding unit. The second section includes the water trap, and the third section includes the route from the inlet of the sensor assembly to the measurement location, which is located in the sensor assembly according to this implementation form.

[0047] In one design, the measurement system includes its own fluid delivery unit. The "fluid delivery unit" can be understood as a component that can deliver fluid, for example by generating a negative pressure or an overpressure. Pumps, fans, and piston-cylinder units are examples for the fluid delivery unit. The fluid delivery unit of the measurement system can be switched on and off by external manipulation. The switched-on fluid delivery unit can branch off the gas sample to be investigated from the patient-fluid guiding unit and deliver it to the sensor assembly. In one implementation form, the sensor assembly is located between the bifurcation point and the fluid delivery unit. The fluid delivery unit sucks the gas sample through the sensor assembly.

[0048] According to the present invention, the pressure in the measurement system is measured. In one design, the measurement location where the pressure is measured is located between the bifurcation point and the fluid delivery unit of the measurement system. A section of the sequence of sections into which the route from the bifurcation point to the measurement location is divided is preferably located upstream of the sensor assembly and the fluid delivery unit of the measurement system. The expression "upstream" relates to the flow direction of the measurement-gas mixture from the bifurcation point to the sensor assembly.

[0049] The sensor-fluid guiding unit preferably connects the bifurcation point to the fluid conveying unit of the measuring system. In many cases, when the fluid guiding unit is shut off, the gas sample flows through the sensor-fluid guiding unit to the sensor assembly due to the overpressure in the patient-fluid guiding unit.

[0050] According to the invention, the pressure in the measuring system can be measured. In a preferred design, the fluid conveying unit of the measuring system is shut off during the measurement of the pressure in the measuring system. The fluid conveying unit is preferably switched on during normal operation and is temporarily shut off for the inspection of leaks or at least when an indicator for a leak has been detected. Since, according to this design, the pressure in the measuring system is measured during the shut-off of the fluid conveying unit, the negative pressure, or overpressure, or pressure fluctuations generated by the fluid conveying unit do not affect the pressure measurement. Instead, an equilibrium is established between the pressure at the bifurcation point and the pressure in the sensor assembly, ideally an equilibrium with the speed of sound.

[0051] According to the invention, the total volume flow is measured or detected, where the total volume flow is the volume flow through which the measurement-gas mixture flows through the sensor assembly. In one design, the measuring system includes its own sensor which measures the volume flow through the sensor assembly. In another design, the total volume flow is derived and thus measured. For example, the sensor measures the volume flow through the patient-fluid guiding unit. The total volume flow through the sensor assembly is derived from this volume flow, the cross-sectional area of the patient-fluid guiding unit, and the cross-sectional area of the sensor-fluid guiding unit.

[0052] During operation of the measuring system, the sensor assembly measures at least one property of the measurement-gas mixture arriving at the sensor assembly. In one design, the or at least one property is the fraction of the composition of the measurement-gas mixture. For example, the composition is O2 and / or CO2 and / or anesthetic. Usually, the fraction can vary over time. For example, if the patient's own breathing activity is supported or even replaced by a medical device, the fraction of O2 in the gas mixture is greater during the inhalation phase than during the exhalation phase. Conversely, the fraction of CO2 is greater during the exhalation phase than during the inhalation phase.

[0053] According to the invention, it is determined whether an indicator for a leak site occurs. In one design, this determination relates to the respective time courses of the respective shares of at least two different components of the measurement - gas mixture. These two shares are two measured properties of the measurement - gas mixture. The two time courses are compared with each other. Here, the fact is utilized that the share of at least one component of the gas mixture flowing through the patient - fluid guiding unit is different from the share of this component in the surroundings of the measurement system. In the leak - free state, the two time courses ideally undergo a phase shift. For example, these two components are oxygen and carbon dioxide.

[0054] According to the invention, a measure for the relative leak volume flow is determined. Different designs for how to determine this measure are possible.

[0055] In one design, the share of at least one component of the measurement - gas mixture is used as the measured property. The said or each share is measured by a sensor assembly and is, for example, O2 and / or CO2. As already mentioned, if there is no leak site, the measurement - gas mixture is equal to the gas sample. The share of this component at the gas sample branched off at the bifurcation point is also measured, for example, in the patient fluid connection or by the sensor assembly. If the share of this component is measured by the sensor assembly, then preferably this measurement is carried out at the time point when there is no leak site and thus the gas sample reaches the sensor assembly without error. The share of this component in the surroundings of the measurement system, for example, in the air, is known and preset in a computer - implementable form. It is also possible that the share of this component in the surroundings is pre - measured and preset for the monitoring method and the monitoring device. As already mentioned, in addition, the total volume flow leading to the measurement location is measured or detected.

[0056] By definition, the volume flow through the leak site is the product of the sought - after relative leak volume flow (i.e., the ratio) and the total volume flow. The volume flow through the leak site contains the volume flow of the component in a known and preset share. The measured or detected total volume flow contains the volume flow of the component in the share measured by the sensor assembly. With the help of these relationships, a computer - evaluable calculation criterion can be preset, which has the relative leak volume flow as the only unknown and which can be applied when monitoring the measurement system.

[0057] In another design, the sensor assembly measures the thermal conductivity of the measurement-gas mixture. Corresponding to the design with components just described, the thermal conductivity of a gas sample is measured, for example, in the patient-fluid guiding unit or in a leak-free state. The thermal conductivity in the surroundings of the measurement system, for example, the thermal conductivity of the ambient air, is known and preset. A computer-evaluable calculation criterion can also be set in advance and used during the inspection, where the calculation criterion again includes the relative leak volume flow as the only unknown.

[0058] These two designs can be combined with each other. Ideally, the two designs provide the same value for the relative leak volume flow, but in practice, usually different values. On the one hand, the combination of the two designs enables the results to be compared with each other and the reasonableness to be checked. If the two designs respectively provide reasonable results, the average value or the weighted average value can be used as the leak volume flow.

[0059] It is also possible that, additionally or alternatively, it is determined based on the measured pressure difference whether an indication of a leak has occurred. If a leak occurs, the pressure difference usually decreases. This is because, compared to the leak-free state, in the case of a leak, a part of the measurement-gas mixture passes through a smaller pneumatic resistance. This part of the measurement-gas mixture is the share flowing through the leak.

[0060] According to the invention, the determined relative leak volume flow is used to identify the section that causes the indication of a leak. In one design, the relative leak volume flow is continuously determined, and it is determined based on the relative leak volume flow whether there is an indication of a leak. In particular, if at a certain point in time the relative leak volume flow is greater than a preset lower limit and / or increases faster than a preset change limit value, there is an indication of a leak.

[0061] According to the invention, a pneumatic resistance is preset for each section respectively. The pneumatic resistance is determined in advance, more precisely preferably based on experience. It is possible that during use, the pneumatic resistance of the section changes, for example, due to water or other liquids depositing on the inner wall of the section. Therefore, it is preferred to redetermine the pneumatic resistance of at least one section later. It is possible to repeat the determination of the pneumatic resistance regularly. The design described above enables the pneumatic resistance to be redetermined only when there is an indication that the values used until now are no longer applicable, that is, event-controlled rather than time-controlled.

[0062] According to this design, the expected pressure difference is calculated at least once, more precisely, preferably at least once when no indicator of a leak is detected. Preferably, the expected pressure difference is calculated repeatedly, for example at a preset frequency. The expected pressure difference is the difference between the pressure at the measurement location and the pressure at the bifurcation point. To use the expected pressure difference, on the one hand, the measured or determined total volume flow is used, and on the other hand, the value used so far for the aerodynamic resistance of the segment is used. Since the segments are connected in series, in the leak-free state, the aerodynamic resistance experienced by the measurement-gas mixture on the route from the bifurcation point to the measurement location is equal to the sum of the aerodynamic resistances of the individual segments. Furthermore, according to the present invention, the actual difference between the pressure at the bifurcation point and the pressure at the measurement location is measured.

[0063] If the measured actual pressure difference deviates from the calculated expected pressure difference by more than a preset tolerance, this result is an indicator that at least one previously used value for the aerodynamic drag is no longer applicable. A message including this result is generated. The message is preferably output in at least one form perceptible to a human. Output of this message can be used to redetermine the aerodynamic drag from now on.

[0064] The present invention also relates to a measurement system capable of monitoring a medical treatment of a patient, and a measurement method using such a measurement system. The measurement system includes a monitoring device according to the present invention. When performing the measurement method, the steps of the monitoring method according to the present invention are performed. The present invention also relates to a treatment assembly designed for performing medical treatment on a patient. The treatment assembly includes the measurement system according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The present invention is described below with reference to exemplary embodiments.

[0066] Figure 1 A breathing circuit for artificial respiration of a patient is schematically shown, wherein a leak occurs in the measuring system;

[0067] Figure 2 Three sections of the measuring system in which leaks may occur, four measuring positions, and the positions of the leaks that occurred are shown by way of example;

[0068] Figure 3 Shown in a different design of the sensor assembly Figure 2 three sections;

[0069] FIG4 shows two time histories of the pressure in the sensor assembly for two different positions of the leak;

[0070] Figure 5 The volume flow is shown as an example Figure 2 and Figure 3the pressure loss at the four measurement positions;

[0071] Figure 6 shows the correlation of the aerodynamic resistance with the volume flow for three sections of Figure 2 and Figure 3 ;

[0072] Figure 7 The method of the present embodiment is shown by a flow chart. Detailed implementation

[0073] In the embodiment, the present invention is used for artificial respiration of a patient. A breathable gas mixture is supplied to the patient, which gas mixture includes oxygen and at least one anesthetic, and optionally additionally includes a drug. The patient is thus anesthetized or at least sedated.

[0074] Figure 1 A breathing assembly 200 with a medical device in the form of an anesthesia device 1 is schematically shown, wherein the breathing assembly 200 serves as a treatment assembly and is capable of performing artificial respiration on a patient Pt. Only the face of the patient Pt is schematically shown. The anesthesia device 1 maintains a breathing circuit 40. The flow direction in the breathing circuit 40 is indicated by arrows. The patient Pt is anesthetized or at least sedated.

[0075] A patient-side coupling unit 21, such as a mask or a breathing mask or a tube arrangement, which is only schematically shown, is arranged in and / or at the body of the patient Pt and connects the patient Pt to the breathing circuit 40. The patient-side coupling unit 21 is connected to a Y-piece 22 via a pipeline 20. The Y-piece 22 is connected to a gas pipeline 32 for inhalation (suction) and a gas pipeline 33 for exhalation (exhalation). These two pipelines 32 and 33 belong to the patient-fluid guiding unit of the present embodiment.

[0076] A gas mixture Gg is supplied to the patient Pt in the breathing circuit 40. In this embodiment, the gas mixture Gg includes oxygen (O2), nitrogen (N2), at least one anesthetic, and optionally another component, such as nitrous oxide (N2O), as a carrier gas for the anesthetic, and / or a gaseous drug. The present invention can also be used for artificial respiration in which the patient Pt is not anesthetized or sedated because the gas mixture Gg supplied to the patient Pt includes oxygen but does not include an anesthetic. The present invention can also be used, for example, to measure at least one vital parameter of the patient Pt by means of a medical device.

[0077] To supply a gas mixture Gg to a patient Pt, an anesthesia device 1 performs a series of respiratory cycles (ventilation cycles). In each respiratory cycle, the anesthesia device 1 respectively discharges a certain amount of breathable gas mixture Gg. The discharged gas mixture Gg is guided in a breathing circuit 40 to a coupling unit 21 on the patient side. The gas mixture At exhaled by the patient Pt into the coupling unit 21 on the patient side contains anesthetic and carbon dioxide (CO2), and flows back in the breathing circuit 40 to the anesthesia device 1.

[0078] It is possible that the patient Pt is not fully anesthetized and instead performs its own respiratory activity. The patient Pt's own respiratory activity is caused by its spontaneous breathing and optionally by external stimulation of its respiratory muscles. Ideally, in this application, the respiratory cycles of the anesthesia device 1 are accurately synchronized with the patient Pt's own respiratory activity.

[0079] An anesthetic vaporizer 31 generates a fluid stream 28 with an additional gas mixture, which additional gas mixture includes a carrier gas and a vaporous anesthetic. The fluid stream 28 with the additional gas mixture is guided through a fluid guiding unit 18 and fed into the breathing circuit 40 at a feed point 38. The gas mixture Gg in the breathing circuit 40 receives the fed additional gas mixture.

[0080] The additional gas mixture and thus the fluid stream 28 are generated as follows: A fluid stream 27 with a carrier gas flows through a fluid guiding unit 17 to an evaporator chamber 47 of the anesthetic vaporizer 31. The carrier gas in the fluid stream 27 includes breathing air and / or pure oxygen (O2) and optionally nitrous oxide (N2O), and is generated by a mixer 48. To generate the additional gas mixture, the anesthetic vaporizer 31 evaporates the anesthetic and feeds the anesthetic into the fluid stream 27 in the evaporator chamber 47. For example, the fed anesthetic comes from a can with liquid anesthetic or from a preprocessor 44, where the preprocessor 44 preprocesses the exhaled breathing air At and extracts the anesthetic from this breathing air. The evaporator module of the anesthetic vaporizer 31 evaporates the liquid anesthetic, and the gaseous anesthetic is fed into the fluid stream 27 in the evaporator chamber 47.

[0081] At least as long as there is no excessive overpressure in the breathing circuit 40, the air At exhaled by the patient Pt remains in the breathing circuit 40, so that no anesthetic reaches the surroundings. The overpressure is preferably relieved in such a way that even when the overpressure is relieved, no anesthetic reaches the surroundings, but for example reaches the preprocessor 44.

[0082] The gas mixture At flowing away from the patient Pt through the breathing circuit 40 inevitably contains carbon dioxide (CO2) exhaled by the patient Pt. A carbon dioxide absorber (CO2 absorber) 25a can absorb carbon dioxide from the breathing circuit 40.

[0083] The fluid delivery unit 24a generates a flow of the gas mixture Gg in the breathing circuit 40. The breathing circuit 40 is kept operating by the fluid delivery unit 24a and optionally by a manually operable manual breathing bag 26. In this embodiment, the fluid delivery unit 24a is in the form of a fan, which generates a constant fluid flow. The use of the fan facilitates synchronization of the breathing stroke with the patient Pt's own breathing activity. It is also possible that the fluid delivery unit 24a includes a pump, a bellows, and / or a piston-cylinder unit.

[0084] In this embodiment, the fluid delivery unit 24a continuously delivers the gas mixture Gg. Preferably, the fluid delivery unit 24a is controlled in a closed-loop control target such that the pressure at the output of the fluid delivery unit 24a remains constant, for example, constant at 5 mbar. The controllable proportional valve 24b helps to generate the individual breathing strokes and determines the amplitude and frequency of these breathing strokes. In each breathing stroke, a certain amount of the breathable gas mixture Gg is respectively guided through the inhalation-gas line 32 to the Y-piece 22 and to the patient-side coupling unit 21 and thus to the patient Pt.

[0085] The PEEP valve 24c (PEEP = "positive end-expiratory pressure") can, depending on its position, allow the fluid flow through the exhalation-gas line 33 to pass or block the fluid flow, and thereby ensure that a sufficiently large pressure is maintained in the lungs of the patient Pt even at the end of exhalation or when the breathing circuit 40 is opened or interrupted for a short time. Thereby, the risk that the lungs of the patient Pt collapse due to too low a pressure is reduced.

[0086] The check valve 23a allows the air flow to pass through the inhalation-gas line 32 to the Y-piece 22 and blocks the air flow in the opposite direction. The check valve 23b allows the air flow to pass through the exhalation-gas line 33 away from the Y-piece 22 and blocks the air flow in the opposite direction.

[0087] The pressure relief valve 29 (pressure release valve) can relieve the overpressure in the breathing circuit 40 in such a way that the pressure relief valve causes the gas to escape from the breathing circuit 40 at too high a pressure. Preferably, the output gas is output to the delivery line for the anesthetic gas and reaches the pre-processor 44. Thereby, the anesthetic is prevented from escaping into the surrounding environment even in the case of overpressure.

[0088] The signal processing respiratory control device 35 (control unit), which is only schematically shown, receives the signals of an optional pressure sensor 58 and an optional temperature sensor 39, which measures the gas pressure P in the surroundings of the anesthesia device 1 and thus in the surroundings of the breathing circuit 40 amb, the temperature sensor measures the ambient temperature. In addition, the respiratory control device 35 also receives the signal from the pressure sensor 36, which measures the current pressure in the breathing circuit 40, such as the breathing pressure (airway pressure, P aw ) applied to the patient Pt, and in one design, as the pressure difference relative to the ambient pressure P amb . The pressure sensor 36 preferably measures the pressure of the gas mixture Gg that is delivered to the coupling unit 21 on the patient side during the inhalation phase. The volume flow sensor 46 measures the volume flow (volume flow rate) Vol' through the line 32, that is, the volume per unit time, more precisely at the measurement site downstream of the feed point 38 and downstream of the check valve 23a. The respiratory control device 35 receives the signals from the volume flow sensor 46 and the pressure sensor 36 and respectively receives the signals from the optional sensors 58 and 39. Preferably, an unshown volume flow sensor measures the volume flow through the line 33.

[0089] The respiratory control device 35 controls the fluid delivery unit 24a, the PEEP valve 24b, the anesthetic vaporizer 31 and other components of the breathing circuit 40 in order to achieve the desired artificial respiration and optionally the anesthesia of the patient Pt. For this control, the respiratory control device 35 processes the signals from the sensors 36, 46, 39, 58 and the indicators from the user and / or the higher-level control device.

[0090] In one design, the respiratory control device 35 performs closed-loop control. One closed-loop control objective is that the actual time course of the volume flow Vol' through the line 32 and / or the actual time course of the pressure P aw in the line 32 follows a preset time course. The first alternative is generally called volume-controlled closed-loop control, and the second alternative is called pressure-controlled closed-loop control. For this closed-loop control, the respiratory control device 35 processes the signals from the sensor 46 and / or the sensor 35.

[0091] It is generally desired that the gas mixture Gg supplied to the patient Pt satisfies certain characteristics. Generally, the concentration (proportion) of the components of the gas mixture Gg should be within a preset target range. In particular, the proportion of the anesthetic should generally be within a preset range. On the one hand, the anesthetic proportion should be high enough so that the patient Pt is reliably anesthetized. On the other hand, the patient Pt is not allowed to be endangered by an excessive anesthetic proportion. Hereinafter, the term "concentration" of the gas components in the gas mixture is used. The synonym is the term "proportion".

[0092] To achieve this goal, it is necessary to measure the actual corresponding fractions of the different components of the gas mixture Gg. At least one fraction can vary over time. Usually, in particular, the oxygen fraction and the CO2 fraction in the gas mixture Gg oscillate. For this purpose, for the gas mixture Gg, a sample of breathing gas (hereinafter: gas sample Gp) is taken (branched off) from the breathing circuit 40 via the extraction hose 52, analyzed, and fed back into the breathing circuit 40 via the return hose 56 again.

[0093] The extraction hose 52 starts at the branching point 34, which in this embodiment is located between the Y-piece 22 and the patient-side coupling unit 21. Thus, sometimes the gas mixture Gg from the line 22 and sometimes the gas mixture At of the patient-side coupling unit 21 enter the extraction hose 52. Optionally, a valve (not shown) is located at the branching point 34, which separates the extraction hose 52 from the breathing circuit 40 in the closed position and which can be controlled by the breathing control device 35. In the case of the valve being fully open or released, the extraction hose 52 is in unrestricted fluid connection with the breathing circuit 40. The return hose 56 leads to the confluence point 37 upstream of the carbon dioxide absorber 25a.

[0094] As Figure 1 can be seen, the fluid delivery unit 24a is located between the branching point 34 and the confluence point 37. Thus, the fluid delivery unit 24a generates an overpressure at the branching point 34 at least during the inhalation phase. This overpressure helps to branch off the gas sample Gp from the breathing circuit 40.

[0095] The extraction hose 52 guides the gas sample Gp to the sensor assembly 50 with its own signal processing unit 30. The sensor assembly 50 is spatially remote from the patient-side coupling unit 21 and from the lines 32 and 33 and, for example, also belongs to the schematically shown anesthesia device 1. In Figure 1 this, for the sake of illustration, the sensor assembly 50 is shown outside the anesthesia device 1.

[0096] The fluid guiding unit 60 guides through the sensor assembly 50 and connects the extraction hose 52 with the return hose 56. The two hoses 52 and 56 and the fluid guiding unit 60 belong to the sensor-fluid guiding unit of this embodiment.

[0097] In this embodiment, the sensor assembly 50 includes a fluid delivery unit in the form of a pump 55 that sucks the gas sample Gp from the breathing circuit 40 and aspirates it through the extraction hose 52. In one design, the pump 55 aspirates the gas sample Gp at a constant volumetric flow, for example 0.2 l / min, where the volumetric flow has the unit of measurement [l / min] for example. In one design, the sensor of the sensor assembly 50 is located between the bifurcation point 34 and the pump 55. Preferably, the pump 55 aspirates the gas sample Gp through and / or past the sensor. The volumetric flow generated by the pump 55 can be constant or can vary over time. The volumetric flow leading to the sensor assembly 50 is only a part of the volumetric flow Vol', through which the gas mixture Gg flows through the breathing circuit 40, and the volumetric flow sensor 46 measures this volumetric flow.

[0098] Generally, the gas mixture Gg flows through the breathing circuit 40 at a temperature that is approximately equal to the body temperature of the patient Pt. The branched-off gas sample Gp cools down to approximately room temperature in the extraction hose 52, whereby moisture condenses. A water separator 51 is arranged at the input of the sensor assembly 50, where the moisture condensed in the extraction hose 52 is collected in the water separator 51. Thereby, the gas sample Gp with a reduced water content reaches the sensor assembly 50. The water separator 51 includes a water tank in which the condensed moisture is collected and a receiving part that is in fluid connection with the extraction hose 52 and in fluid connection with the sensor assembly 50. The gas sample Gp flows from the extraction hose 52 through the receiving part of the water tank 51 into the sensor assembly 50. The water tank is detachably connected to the receiving part. To empty the water tank, the water tank is detached from the receiving part, emptied and reconnected to the receiving part.

[0099] In this embodiment, the sensor assembly 50 includes the following sensors that measure the respective concentrations of the components of the gas sample Gp, see Figure 2 and Figure 3 :

[0100] - a sensor 59 for the anesthetic concentration (AGas);

[0101] - a sensor 54 for the carbon dioxide concentration (CO2); and

[0102] - a sensor 53 for the oxygen concentration (O2), where the sensor 53 preferably utilizes the fact that oxygen is a paramagnetic gas.

[0103] The sensor assembly 50 is designed, for example, in the same way as described in DE 10 2021 126 106 A1.

[0104] In addition, the sensor assembly 50 also includes a pressure sensor 57 that measures the pressure P of the gas sample Gp in the sensor assembly 50cell This pressure P cell can vary over time due to pressure oscillations in the breathing circuit 40 and because the extraction hose 52 is in fluid connection with the breathing circuit 40 if no valve is present at the bifurcation point 34 or as long as the optional valve at the bifurcation point 34 is open. If the valve is missing or open, the pressure in the breathing circuit 40 propagates approximately at the speed of sound to the sensor assembly 50.

[0105] Figure 2 and Figure 3 shows Figure 1 measurement system 100 and four measurement positions Mp.0, ..., Mp.3, the meanings of which are described below. The measurement position Mp.0 is the bifurcation point 34, the measurement position Mp.1 is the transition from the extraction hose 52 to the water separator 51, the measurement position Mp.2 is the transition from the water separator 51 to the sensor assembly 50, and the measurement position Mp.3 is the measurement position where the pressure sensor 57 in the sensor assembly 50 measures the pressure P cell at.

[0106] In Figure 2 the implementation shown, two sensors 59 and 54 are connected in series and arranged at the fluid guiding unit 60, and the O2 sensor 53 is arranged in parallel with these two sensors 59 and 54 at the bypass line. Another arrangement is also possible. The pressure sensor 57 is arranged downstream of the three sensors 59, 54, 53 and upstream of the pump 55. Thus, the pressure sensor 57 measures the pressure P at the input of the pump 55 cell .

[0107] In Figure 3 the implementation, the same component implements both the sensor 59 for the anesthetic and the sensor 54 for the carbon dioxide. This component is connected in series with the oxygen sensor 53. This implementation reduces the risk of the three sensors 59, 54, 53 analyzing two different gas samples in two parallel fluid guiding units. The pressure sensor 57 measures the pressure in the fluid guiding unit 60, more precisely at the measurement position between the component implementing the sensors 54 and 59 and the O2 sensor 53. In one design, a sensor (not shown) is arranged in the bypass line, which measures the density of the measurement - gas mixture MGg. Other implementations and measurement positions are also possible.

[0108] Even when the pump 55 is switched off, the gas sample Gp reaches the sensor assembly 50, unless the fluid connection between the breathing circuit 40 and the extraction hose 52 is interrupted. Hereinafter, the volume flow of the gas mixture reaching the pressure sensor 57 is denoted by Q ges . If the pump 55 is switched on, this pump realizes this volume flow Q gesPreferably, the pump 55 is switched off for the check period and the pressure sensor 57 measures the pressure P during the check period. cell .

[0109] Sensor assembly 50, water trap 51, signal processing unit 30, and hoses 52 and 56 together form a measuring system 100, which draws a gas sample Gp from breathing circuit 40, analyzes it, and feeds it back into breathing circuit 40. Measuring system 100 is part of breathing assembly 200. Signal processing unit 30 receives the signals of sensors 59, 54, 53, and 57 and, in one embodiment, controls pump 55. The measurement results of measuring system 100 are transmitted to breathing control device 35.

[0110] It is possible that a leak has occurred on the path from the branching point 34 of the removal hose 52 to the pressure sensor 57. Some possible reasons for the occurrence of a leak are as follows:

[0111] - Sensors 59, 54, 53 of sensor assembly 50 were replaced and the new sensors were not inserted correctly.

[0112] The removal hose 52 is not correctly connected to the water trap 51 and / or is not correctly connected to the breathing circuit 40 .

[0113] The water tank of the water trap 51 is empty and the empty water tank is not correctly connected to the receiving part of the water trap 51 .

[0114] - In order to meet the requirements of hygiene, the water trap 51 is replaced from time to time. However, the new water trap 51 is not properly connected to the extraction hose 52 and / or is not properly connected to the sensor assembly 50.

[0115] Due to mechanical effects, the removal hose 52 becomes detached from the water trap 51 and / or detached from the breathing circuit 40 or is damaged.

[0116] This leak usually occurs suddenly. Figure 1 、 Figure 2 and Figure 3 FIG. 5 shows, by way of example, a leakage L in the transition between the removal hose 52 and the water trap 51 .

[0117] This leakage portion L can cause errors in the measurement results of sensors 59, 53, and / or 54 and / or additional sensors not shown. For example, the ambient air sucked into the measurement system 100 through the leakage portion L may have a higher or lower concentration of a certain component than the gas mixture Gg. Therefore, the leakage portion L disguises other concentrations different from the actual concentration and can thus lead to incorrect measurement results. The incorrectly measured concentration can lead to errors in the artificial respiration of the patient Pt. Therefore, the leakage portion L must be identified as quickly as possible and a corresponding alarm must be issued in order to quickly locate and eliminate the leakage portion L. On the other hand, it is desirable to generate as few false alarms as possible, ideally no false alarms at all.

[0118] As already mentioned, the sensor assembly 50 measures the respective time courses of multiple components of the gas mixture flowing through the sensor assembly 50. In a leak-free state, this gas mixture is equal to the branched gas sample Gp. Hereinafter, the term "measurement-gas mixture" is used for the gas mixture that flows through the sensor assembly 50. In the case of the leakage portion L, the measurement-gas mixture MGg contains a certain proportion of the ambient air sucked through the leakage portion L.

[0119] Different methods can be applied to automatically check whether such a leakage portion occurs. Some methods are based on the following embodiment in their application, that is, the sensor assembly 50 measures the respective time courses of at least two different components of the measurement-gas mixture MGg, in particular the time courses of CO2 and O2. The control device 30 uses these at least two time courses to determine whether a leakage portion occurs. One basis of these methods is that in the absence of a leakage portion, the two courses are phase-shifted relative to each other after appropriate normalization, and are differently positioned relative to each other in the presence of a leakage portion.

[0120] One possible method is to determine the statistical similarity between the two time courses, such as the phase shift between the two time courses or a measure for the symmetry between the two time courses or the covariance between the two time courses or the covariance between the two time derivatives of the two time courses.

[0121] In another possible method, how the two time courses change is derived, that is, two time derivatives are formed. In a leak-free state, ideally the two time change courses always have opposite signs, because during the inhalation phase, the proportion of O2 increases, and during the exhalation phase, the proportion of CO2 increases. A long enough time interval with the same sign is an indicator for a leakage portion.

[0122] In this embodiment, the pump 55 is turned off for at least one inspection period. The gas sample then due to the pressure P in the breathing circuit 40 awand flows through the extraction hose 52 into the sensor assembly 50.

[0123] The pressure sensor 57 measures the pressure P of the measurement-gas mixture MGg at the measurement position Mp.3 cell over time. The pressure sensor 36 measures the pressure P in the breathing circuit 40 aw . In one design for detecting a leak, the two time courses of the pressures P cell and P aw are compared with each other. A large deviation is an indicator for a leak.

[0124] In another application, the sensor assembly 50 measures the time course of the thermal conductivity of the measurement-gas mixture MGg. Generally, the gas mixture Gg in the breathing circuit 40 and thus the gas sample Gp have a different thermal conductivity from the ambient air, so that a leak L changes the thermal conductivity of the measurement-gas mixture MGg.

[0125] The signal processing unit 30 determines the time course of the relative leak volume flow α rel . The relative leak volume flow α rel is the ratio between the volume flow Q leak through the leak L and the total volume flow Q ges leading to the sensor assembly 50. If no leak occurs, the relative leak volume flow α rel ideally equals zero. The total volume flow Q ges flowing through the sensor assembly 50 is detected or approximately measured. When the pump 55 is switched on, the total volume flow Q ges can be detected by controlling the pump 55. When the pump 55 is switched off, the total volume flow Q ges can be approximately derived, for example, by using the fact that the volume flow through the line 32 is divided at the bifurcation point 34 into the volume flow towards the coupling unit 21 on the patient side and the volume flow into the extraction hose 52. The volume flow Vol' through the line 32 is measured by the volume flow sensor 46. The cross-sectional areas of the line 26 and the extraction hose 52 are known from the structural design. In a leak-free state, the volume flow into the extraction hose 52 equals the sought total volume flow Q ges . It is also possible that the measuring system 100 includes its own volume flow sensor (not shown) which measures the volume flow through the sensor assembly 30.

[0126] The total volume flow Q ges leading to the measurement position Mp.3 is the sum of

[0127] - the volume flow Q Gp into the extraction hose 52 at the bifurcation point 34, and

[0128] - Volume flow Q through the leakage L Leak ,

[0129] Right now

[0130] (1) Q ges = Q Gp + Q Leak .

[0131] Applicable by definition

[0132] (2) Q Leak = α rel *Q ges .

[0133] For the following volume flow Q Gp , with which volume flow the gas sample Gp branches off from the breathing circuit 34 at the branching point 34 , the following applies:

[0134] (3) Q Gp = Q ges -Q Leak = (1-α rel )*Q ges .

[0135] It is possible (but not necessary for the present invention) to measure the volume flow Q at the bifurcation point 34 Gp .

[0136] To determine the relative leakage volume flow α rel In one embodiment, the signal processing unit 30 uses the measured time course of the thermal conductivity of the gas mixture MGg and the predefined thermal conductivity of the surrounding air. In another embodiment, the signal processing unit 30 additionally uses the measured time course of the concentration of O 2 or another component of the gas mixture MGg.

[0137] Ideally, the thermal conductivity and O2 concentration of the measured gas mixture MGg result in the same relative leakage volume flow α rel ; In practice, these two are for the relative leakage volume flow α rel The measurements deviate from each other. Calculate the appropriate average of these two measured measurements and use it as the relative leakage volume flow α rel Measure of.

[0138] The following describes in more detail how the relative leakage volume flow α is determined. rel In many cases, it is reasonable to assume that the thermal conductivity WLF of the measurement-gas mixture MGg arriving at the measurement position Mp.3 ges is the thermal conductivity WLF of the bifurcated gas sample Gp GpThermal conductivity WLF of the ambient air and the surrounding environment env The weighted average value, and thus the weighted average value of the gas flow through the leakage portion L. The thermal conductivity WLF of the ambient air env The weighted coefficient of the inflow is the relative leakage volume flow α rel . Under this assumption, it follows that:

[0139] (4) WLF ges = (1 - α rel ) * WLF Gp + α rel * WLF env

[0140] The thermal conductivity WLF of the ambient air env is known and preset. In a design, the thermal conductivity WLF of the ambient air env is measured regularly, for example when recalibrating the sensor assembly 50. In a design, the signal of the temperature sensor 39 is used to derive the thermal conductivity WLF of the ambient air env . The sensor assembly 50 measures the thermal conductivity WLF of the measurement-gas mixture MGg reaching the measurement position Mp.3 ges . The sensor assembly 50 preferably determines the value for the thermal conductivity WLF ges , which is determined over a respiratory cycle including an inhalation phase, an optional intermediate phase, and an exhalation phase. Different values can be determined for the next respiratory cycle. If there is no leakage portion, then WLF ges = WLF Gp .

[0141] The measured thermal conductivity WLF ges is used as the thermal conductivity WLF of the gas sample Gp Gp , where the thermal conductivity WLF used ges is measured at a point in time, or determined for a respiratory cycle where no leakage is detected, such as at the start of use or when no other method provides an indication of leakage. These premises mean that the only unknown in formula (4) is the relative leakage volume flow α rel .

[0142] The sensor assembly 50 measures the current concentration (current fraction) con of the components of the measurement-gas mixture MGg drawn in by the pump 55 ges . It is also reasonably assumed that the concentration of this component is the weighted average of the concentration Con in the gas sample Gp Gp and the concentration con in the ambient air env , that is, the following applies

[0143] (5) Conges = (1- α rel )*Con Gp + α rel * Con env

[0144] The concentration Con at the time when there is no leakage is measured. ges , and use it as the concentration Con of the gas sample Gp Gp The concentration of the component in the ambient air is Con env is known or measured and preset in advance. Then formula (5) has the leakage volume flow α rel As the only unknown variable, it is possible to carry out the procedure just described for two different components of the measurement gas mixture MGg, for example for O 2 and for CO 2 .

[0145] At least two of the above-described embodiments for detecting a leak L can be combined with one another. For example, if at least one of the above-mentioned criteria is met, an indicator for a leak exists. For example, if the relative leakage volume flow α rel If it is greater than a preset lower limit, there is an indicator for the leakage part L.

[0146] The method just mentioned can be used to determine Figure 2 The system detects whether a leak is present between the two measurement positions Mp.0 and Mp.3, or more precisely, whether an indicator for such a leak is present. If such a leak L is present, it must be eliminated as quickly as possible to avoid endangering the patient Pt's artificial respiration. To quickly eliminate a detected leak L, the user must locate the leak. The present invention assists the user in locating the leak L or eliminating the possibility of an actual leak.

[0147] For this purpose, the path from the branch point 34 (measurement position Mp.0) to the measurement position Mp.3 is pre-divided into at least two sections, in this embodiment, into three sections. Not only is the presence of a leak indicated to the user, but also the section in which the leak occurred is indicated to the user.

[0148] At least two sections are connected in series. Figure 2 and Figure 3Three sections Sg.1, Sg.2, Sg.3 of the present embodiment are shown by way of example. The first section Sg.1 includes a withdrawal hose 52 and extends from a bifurcation point 34 (measurement position Mp.0) until it enters a water collector 51 (measurement position Mp.1). The second section Sg.2 includes the water collector 51. A leakage section L shown by way of example appears in the second section Sg.2. The third section Sg.3 includes a sensor assembly 50 between an input end (measurement position Mp.2) and a pressure sensor 57 (measurement position Mp.3).

[0149] FIG. 4 shows by way of example the pressure P measured by the pressure sensor 57 cell as a function of time. The pressure P in the breathing circuit 40 aw and thus also the measured pressure P cell oscillate. The time in [sec] is plotted on the x-axis and the measured pressure P in [mbar] cell is plotted on the y-axis. In the time interval T Leak between 60 s and 110 s, the influence of the leakage section L can be seen. In the example shown, a laboratory test is performed in which a leakage section L is generated and then eliminated again. The leakage section L causes the measured oscillating pressure P cell to be greater than the pressure in the state without the leakage section. In the Figure 4a ) example, the leakage section appears in section Sg.1, and in the Figure 4b ) example, the leakage section appears in section Sg.3. It can be seen that the oscillating pressure P cell with a leakage section in section Sg.3 is greater than the pressure with a leakage section in section Sg.1, and is greater with a leakage section than in the non-leaking state. This fact is utilized according to the present invention. It is explained below why this is the case and how this situation is utilized and the leakage section L is located.

[0150] It is well known that a fluid guiding unit has a pneumatic resistance which causes a pressure drop. The pneumatic resistance corresponds to an electrical resistance and is also designated by R hereinafter. According to Ohm's law, the electrical resistance is the quotient of the voltage U and the current intensity I and causes an electrical pressure drop ΔU. Correspondingly, the pneumatic resistance R is the quotient of the pressure loss ΔP and the volume flow Q. For example, the pneumatic resistance R has the measuring unit mbar / (l / min) which corresponds to the electrical measuring unit ohm. The pneumatic resistance R causes a pressure loss ΔP. The pneumatic resistance between Figure 2 the measurement positions Mp.0 and Mp.3 causes a pressure loss ΔP cell . This pressure loss ΔP cell is equal to the difference between

[0151] - the pressure P measured by the pressure sensor 57cell , and

[0152] - the pressure P measured by the pressure sensor 36 aw .

[0153] The pressure loss ΔP cell is continuously measured.

[0154] Figure 5 Exemplarily shows the corresponding pressure losses caused by the aerodynamic resistance of three sections. The shown course is from internal tests and simulations. The course is obtained without the presence of a leak section. The four measurement positions Mp.0,..., Mp.3 where the corresponding pressures are measured are plotted on the x-axis, and the pressure loss ΔP in [mbar] occurring between the bifurcation point 34 (measurement position Mp.0) and the corresponding measurement positions Mp.0,..., Mp.3 is plotted on the y-axis. As already mentioned, the pressure loss ΔP is the difference between the pressure at the corresponding measurement positions Mp.0,..., Mp.3 and the pressure P at the bifurcation point 34 aw The pressure loss ΔP at the measurement position Mp.3 is equal to the pressure loss ΔP measured during use cell .

[0155] The aerodynamic resistance R and thus the pressure loss ΔP are related to the volume flow Q in [l / min] of the gas sample Gp flowing from the bifurcation point 34 to the sensor assembly 50. Seven measurement curves relate to the volume flow Q between 0.1 l / min and 0.2 l / min. It can be seen that the higher the volume flow Q, the greater the pressure loss ΔP.

[0156] Note: In order to obtain Figure 5 the test results shown in, the corresponding pressures are measured at four different measurement positions. For production use, it is sufficient for the pressure sensor 57 to measure the pressure P in the sensor assembly 50 (i.e., at the measurement position Mp.3) cell , and in addition the pressure sensor 36 measures the pressure in the breathing circuit 40 and thus at the measurement position Mp.0.

[0157] One concept of the present invention is to measure this pressure loss ΔP cell , and then, based on the measured pressure loss ΔP cell to identify those sections Sg.1, Sg.2, Sg.3 in which a leak section L occurs. Since the sections Sg.1, Sg.2, Sg.3 are connected in series, the aerodynamic resistances of the individual sections add up to the total aerodynamic resistance fluidly connected between the measurement positions Mp.0 and Mp.3.

[0158] The following boundary conditions are to be considered:

[0159] - The corresponding pneumatic resistances of the partial sections Sg.1, Sg.2, Sg.3 are related to the actual volume flow Q passing through these partial sections Sg.1 , Q Sg.2 , Q Sg.3 . In the state without a leakage section, this volume flow Q Sg.1 , Q Sg.2 , Q Sg.3 is equal to the volume flow Q generated by the pump 55 with sufficient accuracy, i.e., it is consistent in all three partial sections Sg.1, Sg.2, Sg.3. In the case of a leakage section L, the two volume flows Q passing through the partial sections Sg.1, Sg.2, Sg.3 ges , Q Sg.1 , Q Sg.2 , Q Sg.3 can be different from each other. This is because the volume flow Q generated by the pump 55 ges is then divided into the volume flow Q from the bifurcation point 34 Gp and the volume flow Q passing through the leakage section L Leak .

[0160] - The pressure in the breathing circuit 40 and thus also the pressure P measured by the pressure sensor 57 cell oscillates. These oscillations are caused by the breathing stroke of the breathing device 1.

[0161] - The pneumatic resistances of the partial sections Sg.1, Sg.2, Sg.3 can change over time, especially in the case of the partial sections Sg.1, Sg.2 due to condensate.

[0162] How these boundary conditions are taken into account is described below.

[0163] In this embodiment, the pressure loss ΔP can be described by the following formula:

[0164] (6) ΔP cell = ΔP Sg.1 + ΔP Sg.2 + ΔP Sg.3 =

[0165] R Sg.1 (Q Sg.1 ) * Q Sg.1 +R Sg.2 (Q Sg.2 ) * Q Sg.2 +R Sg.3 (Q Sg.3 ) * Q Sg.3 .

[0166] Here, Q Sg.1 , Q Sg.2 , Q Sg.3Denote the corresponding actual volume flows through the respective sections Sg.1, Sg.2, Sg.3. ΔP Sg.1 , ΔP Sg.2 , ΔP Sg.3 Denote the pressure losses in the respective sections Sg.1, Sg.2, Sg.3, and R Sg.1 (Q), R Sg.2 (Q), R Sg.3 (Q) denotes the respective aerodynamic resistances of the sections Sg.1, Sg.2, Sg.3. This aerodynamic resistance is related to the volume flow Q through the section. Equation (6) applies both to the case without a leakage section and to the case with a leakage section. If there is no leakage section, the actual volume flow Q Sg.1 , Q Sg.2 , Q Sg.3 Are consistent with each other. In closed-loop control operation, the actual volume flow is consistent with the volume flow Q that is constant over time achieved by the pump 55 ges .

[0167] Figure 6 Exemplarily shows the respective aerodynamic resistances R Sg.1 (Q), R Sg.2 (Q), R Sg.3 (Q) of the three sections Sg.1, Sg.2, Sg.3. If Ohm's law is directly borrowed, the aerodynamic resistance R would be independent of the volume flow Q. However, in the current case, the aerodynamic resistance R is slightly related to the volume flow Q, i.e., R = R(Q). The volume flow Q through the section in [l / min] is plotted on the x-axis, and the aerodynamic resistance R in [mbar / (l / min)] related to the volume flow Q through the respective section Sg.x (x = 1, 2, 3) is plotted on the y-axis

[0168] As can be seen from Figure 6 , the aerodynamic resistance R Sg.x = R Sg.x (Q) is approximately described by the following model

[0169] (7) R Sg.x (Q) = R_0 Sg.x – R_1 Sg.x *Q

[0170] for (x = 1, 2, 3). Here, R_0 Sg.x and R_1 Sg.x Are two constants greater than zero. These constants can be determined in advance based on experience

[0171] If equation (7) is inserted into equation (6), the following equation is obtained

[0172] (8) ΔP cell= ΔP SG.1 (Q Sg.1 ) + ΔP Sg.2 (Q Sg.2 ) + ΔP SG.3 (Q Sg.3 ) = R Sg.1 (Q Sg.1 )*Q Sg.1 +R Sg.2 (Q Sg.2 )*Q Sg.2 +R Sg.3 (Q Sg.3 )*Q Sg.3 = [R_0 Sg.1 *Q Sg.1 +R_0 Sg.2 *Q Sg.2 +R_0 Sg.3 *Q Sg.3 - [R_1 Sg.1 *Q Sg.1 2 +R_1 Sg.2 *Q Sg.2 2 +R_1 Sg.3 *Q Sg.3 2 。

[0173] If there is no leakage part, the formula (8) is simplified to

[0174] (9) ΔP = [R_0 Sg.1 + R_0 Sg.2 + R_0 Sg.3 *Q ges – [R_1 Sg.1 + R_1 Sg.2 +R_1 Sg.3 *Q ges 2 。

[0175] The following describes how to identify the section Sg.x (x = 1, 2, 3) where the leakage part L appears after detecting the leakage part L. If the leakage part L appears, the relative leakage volume flow α rel is greater than 0. In this embodiment, the relative leakage volume flow α rel is determined, for example, in the case of applying the calculation criteria (4) and / or (5). In addition, the pressure difference ΔP cell is determined, that is, the difference between the two pressures P cell and P aw measured by the two pressure sensors 57 and 36 is determined. Although the measured pressures P cell and P awOscillations occur, but the pressure difference ΔP cell oscillates less, and ideally no oscillations occur.

[0176] The branched gas sample Gp is subject to the respective pneumatic resistances of all three sections Sg.1, Sg.2, Sg.3 on its path from the branch point 34 to the pressure sensor 57. The volume flow into the extraction hose 52 is Q Gp . However, depending on where the leak section L occurs, unless the leak section occurs at the measurement location Mp.0, the gas mixture sucked through the leak section L and flowing to the pressure sensor 57 with the volume flow Q Leak is subject to a lower pneumatic resistance. Along the route from Mp.0 to Mp.3, the closer the leak section is to the pressure sensor 57, the smaller the pressure difference ΔP cell . This principle is used to identify the section Sg.x with the leak section L. This is explained below with two examples.

[0177] As already mentioned, the gas mixture flows with the volume flow Q Leak = α rel *Q ges from the surroundings through the leak section L to the pressure sensor 57, see formula (2). The relative leak volume flow α rel is determined, and the total volume flow Q ges with which the gas mixture flows to the pressure sensor 57 is known or also measured. In particular, it is known which volume flow the pump 55 achieves.

[0178] Let ΔP Mp.x represent the predicted pressure difference for the case where a leak section L occurs at the measurement location Mp.x. In other words: If the model assumptions described below apply, and a leak section occurs at the measurement location Mp.x, but otherwise no leak section occurs in the measurement system 100, and if the pressures P cell and P aw are measured correctly, then ΔP cell = ΔP Mp.x .

[0179] In the first example, it is assumed that the leak section L occurs at the measurement location Mp.2, i.e., at the transition between the sections Sg.2 and Sg.3, and no other leak sections occur. At least when the pump 55 is switched on, the following volume flow Q ges is not changed due to the leak section L, and the pump 55 generates this volume flow and the measurement - gas mixture MGg reaches the pressure sensor 57 with this volume flow.

[0180] The gas sample Gp has a reduced volume flow

[0181] (10) Q Gp = Qges – Q Leak = (1 - α rel ) * Q ges

[0182] Flows from the bifurcation point 34 to the pressure sensor 57. Then the gas mixture passing through the leakage part L has a volume flow Q leak Only flows through the section Sg.3 to the pressure sensor 57.

[0183] According to the calculation criterion (6), for the pressure loss ΔP of this gas mixture Mp.2 On the one hand, ΔP Sg.1 + ΔP Sg.2 And on the other hand, ΔP Sg.3 Is the sum of. Using the model assumption according to formula (7), for the pressure losses in the two sections Sg.1 and Sg.2, it applies

[0184] (11) ΔP Sg.1 + ΔP Sg.2 = [R Sg.1 (Q Gp ) + R Sg.2 (Q Gp )] * Q Gp = [R_0 Sg.1 + R_0 Sg.2 * (1 - α rel ) * Q ges – [R_1 Sg.1 + R_1 Sg.2 * (1 - α rel ) 2 * Q ges 2 .

[0185] For the pressure loss in the section Sg.3, it applies

[0186] (12) ΔP Sg.3 = R Sg.3 * Q ges = R_0 Sg.3 * Q ges – R_1 Sg.3 * Q ges 2 .

[0187] For the total pressure loss ΔP Mp.2 , it is obtained that

[0188] (13) ΔP Mp.2 = [R_0 Sg.1 + R_0 Sg.2 * (1 - α rel ) * Qges + R_0 Sg.3 *Q ges - [R_1 Sg.1 +R_1 Sg.2 *(1-α rel ) 2 *Q ges 2 -R_1 Sg.3 *Q ges 2 。

[0189] All the parameters on the right side of formula (13) are known. Therefore, if a leakage occurs at the measurement position Mp.2, the differential pressure ΔP is measured according to formula (13) based on the model assumption (i.e., ideally). Mp.2 。

[0190] In the second example, it is assumed that a leakage L occurs at the measurement position Mp.1. This situation is shown in Figure 2 . The leakage-gas mixture then flows through two sections Sg.2 and Sg.3 with a volume flow Q and undergoes an aerodynamic resistance R Leak +R Sg.2 there. If no other leakage occurs, the gas sample Gp flows from the bifurcation point 34 to the pressure sensor 57 with a volume flow Q Sg.3 . Gp For the pressure loss ΔP of this gas mixture

[0191] is on the one hand ΔP Mp.1 and on the other hand is ΔP Sg.1 and Sg.2 +ΔP Sg.3 The sum of. Corresponding to the expression for the volume flow when there is a leakage at the measurement position Mp.2, for the pressure loss in Mp.1, it is obtained that

[0192] (14) ΔP Sg.1 = R_0 Sg.1 *(1-α rel )*Q ges – R_1 Sg.1 *(1-α rel ) 2 *Q ges 2

[0193] and

[0194] (15) ΔP Sg.2 + ΔP Sg.3 = [R_0 Sg.2 + R_0 Sg.3 *Q ges - [R_1Sg.2 +R_1 Sg.3 *Q ges 2 。

[0195] For the total pressure loss ΔP Mp.1 , it is obtained that

[0196] (16) ΔP Mp.1 = [R_0 Sg.1 *(1-α rel )*Q ges + [R_0 Sg.2 + R_0 Sg.3 *Q ges -R_1 Sg.1 *(1-α rel ) 2 *Q ges 2 -[R_1 Sg.2 +R_1 Sg.3 *Q ges 2 。

[0197] ΔP Mp.1 is greater than ΔP Mp.2 。

[0198] As already described, the farther the leakage portion L is from the pressure sensor 57, the greater the pressure difference ΔP cell will be. "Farther away" refers to the path of the gas sample Gp from the bifurcation point 34 to the pressure sensor 57. Based on this principle, the following decision rule can be derived and applied in use, more precisely preferably when the pump 55 is switched on and generates a volume flow Q ges :

[0199] - If the measured pressure difference ΔP cell is less than ΔP Mp.2 , then the leakage portion is located in section Sg.3.

[0200] - If the measured pressure difference ΔP cell is greater than ΔP Mp.1 , then the leakage portion is located in section Sg.1.

[0201] - In other cases, the leakage portion L is located in section Sg.2 or in one of the measurement positions Mp.1 or Mp.2.

[0202] The method just described utilizes the three pneumatic resistances R Sg.1 (Q), R Sg.2 (Q), R Sg.3(Q). In one design, formula (7) is used for this purpose, and this formula requires two values, R_0, for each of the three segments Sg.x (x = 1, 2, 3). Sg.x and R_1 Sg.x . The aerodynamic resistance of segment Sg.x may change during use. If the aerodynamic resistance R Sg.x (Q) of segment Sg.x changes, it is preferable to determine the new values of R_0 Sg.x and R_1 Sg.x based on experience. One design described below describes how to automatically detect an indicator of a change in the aerodynamic resistance of at least one of the segments Sg.1, Sg.2, Sg.3.

[0203] According to this design, it is checked whether the expected aerodynamic resistance in the leak-free state is in sufficient agreement with the actual aerodynamic resistance. The expected pressure difference ΔP exp is predicted according to formula (6), where the values of the aerodynamic resistances R Sg.1 (Q), R Sg.2 (Q), R Sg.3 (Q) used until now for the three segments Sg.1, Sg.2, Sg.3 are inserted into formula (6). The volume flow through the segment is equal to Q ges . The actual pressure difference ΔP cell is measured in a state where there is no leak section. For example, the actual pressure difference ΔP cell is measured in a state where no indicator for a leak section is provided in the methods described above by way of example.

[0204] In the leak-free state, the gas sample Gp flows from the bifurcation point 34 to the pressure sensor 57 at a known volume flow Q ges . The application of formula (6) can provide the following calculation criterion for the expected pressure difference ΔP exp :

[0205] (17) ΔP exp = {R Sg.1 (Q ges ) + R Sg.2 (Q ges ) + R Sg.3 (Q ges )} * Q ges .

[0206] If the deviation between the measured actual pressure difference ΔP cell and the expected pressure difference ΔP exp exceeds a preset absolute limit or percentage limit, then the aerodynamic resistances R Sg.1 (Q), R Sg.2 (Q), RSg.3 At least one of the values of (Q) deviates significantly from the actual situation. Therefore, these values must be adapted to the changing actual situation.

[0207] In one design, the corresponding notification is output in a form perceptible by humans. From now on, the user can determine the current value for aerodynamic drag based on experience and prompt the use of these current values from now on.

[0208] In another design, for the aerodynamic drag R Sg.1 (Q), R Sg.2 (Q), R Sg.3 The value of (Q) is automatically adapted. For example, the previously used value for aerodynamic drag R Sg.1 (Q), R Sg.2 (Q), R Sg.3 The value of (Q) applies a preset adaptation rule, where the adaptation rule is related to the expected pressure difference ΔP exp and the measured actual pressure difference ΔP cell is relevant. For example, each value changes by the same multiple, where the multiple is equal to the quotient ΔP cell / ΔP exp .

[0209] Figure 7 The method steps of this embodiment are shown by a flowchart. This means:

[0210] The M53 sensor 53 measures the time course Con[O2](t) of the O2 concentration in the measurement-gas mixture MGg.

[0211] The M54 sensor 54 measures the time course Con[CO2](t) of the CO2 concentration in the measurement-gas mixture MGg.

[0212] The M50 sensor 50 measures the time course WLF(t) of the thermal conductivity of the measurement-gas mixture MGg.

[0213] The M55 measures or detects the total volume flow Q leading to the pump 55 ges .

[0214] The M36 pressure sensor 36 measures the pressure P in the breathing circuit 40 aw .

[0215] The M57 pressure sensor 57 measures the pressure P at the measurement position Mp.3 in the sensor assembly 50 cell .

[0216] The ΔP calculates the difference ΔP between the measured pressures P cell and P aw and cell .

[0217] S Leak Check whether there is a leak in the measurement system 100.

[0218] Leak determination: Is there a leak in the measurement system 100?

[0219] S Pred Calculate the predicted pressure difference ΔP Mp.1 and ΔP Mp.2 .

[0220] S Loc Identify (locate) the section Sg.x where the leak L occurs.

[0221] S Exp The expected pressure difference ΔP in the non-leaking state exp is calculated according to the currently preset pneumatic resistance of the section.

[0222] Tol calculates the deviation between the measured pressure difference ΔP cell and the expected pressure difference ΔP exp .

[0223] ΔP o.k.? Determination: Is the calculated deviation between ΔP cell and ΔP exp within the preset tolerance band?

[0224] Recalib generates an alarm: The pneumatic resistance R Sg.1 (Q), R Sg.2 (Q), R Sg.3 (Q) values used until now are no longer applicable and new values must be derived (recalibration is required).

[0225] List of Reference Numerals

[0226] 1 A breathing device in the form of an anesthesia device that performs a breathing cycle and discharges a certain amount of gas mixture Gg in each breathing cycle

[0227] 17 A carrier gas line that guides from the mixer 48 to the anesthetic vaporizer 31 and guides the fluid flow 27

[0228] 18 A supply line that guides from the anesthetic vaporizer 31 to the feed point 38 and guides the fluid flow 28

[0229] 20 The line between the coupling unit 21 on the patient side and the Y-piece 22

[0230] 21 The coupling unit on the patient side, which is connected to the body of the patient Pt and to the Y-piece 22

[0231] 22 Y-piece, connecting two gas lines 32 and 33 to the coupling unit 21 on the patient side via line 20

[0232] 23a Check valve in the inhalation-gas line 32

[0233] 23b Check valve in the exhalation-gas line 33

[0234] 24a Fluid delivery unit that moves the gas mixture Gg in the breathing circuit 40

[0235] 24b Controllable proportional valve that causes the breathing stroke

[0236] 24c PEEP valve that maintains the end-expiratory pressure in the lungs

[0237] 25a Carbon dioxide absorber that removes carbon dioxide from the exhaled gas At.

[0238] 26 Line between the Y-piece 22 and the coupling unit 21 on the patient side

[0239] 27 Fluid flow with carrier gas that flows from the mixer 48 to the anaesthetic vaporizer 31 in the carrier gas line 17

[0240] 28 Fluid flow with carrier gas and anaesthetic that flows from the anaesthetic vaporizer 31 to the feed point 38 in the supply line 18

[0241] 29 Pressure relief valve in the breathing circuit 40

[0242] 30 Signal processing unit of the sensor assembly 50

[0243] 31 Anaesthetic vaporizer that generates a fluid flow with gaseous anaesthetic from the fluid flow 27 with carrier gas and from the liquid anaesthetic and feeds the fluid flow with gaseous anaesthetic into the supply line 18, the anaesthetic vaporizer including an evaporator chamber 47

[0244] 32 Gas line for inhalation, leading from the carbon dioxide absorber 25a to the Y-piece 22

[0245] 33 Gas line for exhalation, leading from the Y-piece 22 to the carbon dioxide absorber 25a

[0246] 34 Bifurcation point at which the gas sample Gp branches off from the breathing circuit 40 and is guided into the sampling hose 52

[0247] 35 Respiratory control device that controls the mixer 48 and the anaesthetic vaporizer 31 and processes the signals from the sensors 36, 46, 39, 58 and the sensor assembly 50

[0248] 36 A pressure sensor that measures the pressure P in the breathing circuit 40 aw

[0249] 37 A confluence point where the gas sample Gp is fed back into the breathing circuit 40

[0250] 38 A feed point where the fluid flow 28 is fed into the breathing circuit 40

[0251] 39 A temperature sensor that measures the ambient temperature

[0252] 40 The breathing circuit between the anesthesia device 1 and the coupling unit 21 on the patient side, in which the gas mixture Gg is transported to the coupling unit 21 on the patient side and the exhaled air At is transported back to the anesthesia device 1

[0253] 44 A preprocessor that extracts anesthetic from the exhaled gas At containing anesthetic

[0254] 46 A volume flow sensor that measures the volume flow Vol' through the pipeline 32

[0255] 47 The evaporation chamber of the anesthetic evaporator 31

[0256] 48 A mixer that generates a carrier gas composed of components of breathing air and / or pure oxygen (O2) and optionally nitrous oxide (N2O) and feeds the carrier gas into the carrier gas pipeline 17

[0257] 50 A sensor assembly that analyzes the measurement-gas mixture MGg, the sensor assembly includes sensors 53, 54, 57 and 59, a pump 55, a fluid guiding unit 60 and a signal processing unit 30

[0258] 51 A water separator at the input of the sensor assembly 50

[0259] 52 A sampling hose for the gas sample Gp that starts at the bifurcation point 34 and leads to the sensor assembly 50

[0260] 53 A sensor for measuring the oxygen concentration in the measurement-gas mixture MGg

[0261] 54 A sensor for measuring the carbon dioxide concentration in the measurement-gas mixture MGg

[0262] 55 The pump of the sensor assembly 50 that sucks the gas sample Gp from the breathing circuit 40

[0263] 56 A return hose for the gas sample Gp that starts at the sensor assembly 50 and leads to the confluence point 37

[0264] 57 A pressure sensor that measures the pressure P of the measurement-gas mixture MGg at the measurement location Mp.3 of the sensor assembly 50 cell

[0265] 58 A pressure sensor that measures the gas pressure P in the ambient environment amb

[0266] 59 A sensor for measuring the concentration of anesthetic in the measurement-gas mixture MGg

[0267] 60 A fluid guiding unit that passes through the sensor assembly 50

[0268] 100 A measurement system including the sensor assembly 50, the water separator 51, the signal processing unit 30, and the hoses 52 and 56

[0269] 200 A breathing assembly including the breathing device 1, the pipelines 32 and 33, the Y-piece 22, the coupling unit 21 on the patient side, the measurement system 100, the sensors 36 and 46, and optionally the sensors 39 and 58, providing the breathing circuit 40

[0270] α rel The relative leakage volume flow, the volume flow Q through the leak L leak In the total volume flow Q ges The share at

[0271] At gas mixture, the gas mixture exhaled by the patient Pt into the coupling unit 21 on the patient side and flowing in the breathing circuit 40 to the anesthesia device 1

[0272] Con[CO2] env The share of CO2 in the ambient air, preset or pre-measured

[0273] Con[CO2](t) The time course of the share of CO2 in the measurement-gas mixture MGg, measured by the sensor 54

[0274] Con[O2] env The share of O2 in the ambient air, preset or pre-measured

[0275] Con[O2](t) The time course of the share of O2 in the measurement-gas mixture MGg, measured by the sensor 53

[0276] Gg Gas mixture, the gas mixture discharged from the anesthesia device 1 and guided through the pipeline 32 to the coupling unit 21 on the patient side, the gas mixture contains anesthetic and a carrier gas with oxygen.

[0277] Gp gas sample, which branches off from the breathing circuit 40 at the branching point 34 and is fed back into the breathing circuit 40 again at the confluence point 37

[0278] L Leakage in the measuring system 100

[0279] MGg Measurement - gas mixture, which flows through the sensor assembly 50 and consists of the gas sample Gp and the gas mixture flowing through the leakage L. In a leak - free state, the measurement - gas mixture is equal to the gas sample Gp

[0280] Mp.0 Measuring position at the branching point 34

[0281] Mp.1 Measuring position at the transition between the two sections Sg.1 and Sg.2

[0282] Mp.3 Measuring position at the transition between the two sections Sg.2 and Sg.3

[0283] Mp.3 Measuring position of the pressure sensor 57, while the downstream end of the section Sg.3

[0284] Pt Patient, connected to the patient - side coupling unit 21, being artificially ventilated and optionally anesthetized

[0285] P amb Ambient pressure, measured by the pressure sensor 58

[0286] P aw Airway pressure at the patient - side coupling unit 21, measured by the pressure sensor 36 at the pipeline 20

[0287] P cell Time - varying pressure at the measuring position Mp.3, measured by the pressure sensor 57

[0288] ΔP cell Pressure P at the branching point 34 aw And the pressure P in the sensor assembly 50 cell Between the time - varying pressure loss

[0289] ΔP exp Expected pressure difference in a leak - free state, predicted using the current value of the pneumatic resistance R Sg.1 (Q),R Sg.2 (Q),R Sg.3 (Q) of the current value

[0290] ΔP Gp Pressure difference, which the gas sample Gp experiences on the path from the measuring position Mp.0 to the measuring position Mp.3

[0291] ΔP Mp.1 If the leak portion L appears at the measurement position Mp.1, the predicted pressure difference cell between pressures P aw and P

[0292] ΔP Mp.2 If the leak portion L appears at the measurement position Mp.2, the predicted pressure difference cell between pressures P aw and P

[0293] R Aerodynamic resistance

[0294] R Sg.1 (Q), R Sg.2 (Q), R Sg.3 (Q) Aerodynamic resistances of sections Sg.1, Sg.2, Sg.3, related to the volume flow Q through the sections

[0295] Q Volume flow

[0296] Q ges The volume flow in [l / min] of the gas mixture flowing to the pressure sensor 57, generated and measured or derived by the pump 55 or by the overpressure in the breathing circuit 40

[0297] Q Leak Volume flow through the leak portion L

[0298] Q Sg.1 , Q Sg.2 , Q Sg.3 Actual volume flows through sections Sg.1, Sg.2, Sg.3

[0299] Sg.1 Section with the extraction hose 52, extending between the measurement positions Mp.0 and Mp.1

[0300] Sg.2 Section with the water trap 51, extending between the measurement positions Mp.1 and Mp.2 Sg.3 Section in the sensor assembly 50, extending between the measurement positions Mp.2 and Mp.3

[0301] T Leak Time period during which the leak portion L appears

[0302] Temp amb Ambient temperature, measured by the temperature sensor 39

[0303] Vol' Volume flow (volume rate) through the line 32, measured by the volume flow sensor 46

[0304] WLF(t) Time history of the measurement of the thermal conductivity of the gas mixture MGg, measured by the sensor 50

[0305] WLFenv The thermal conductivity of the ambient air is preset or pre-measured

Claims

1. A monitoring method for monitoring a measurement system (100) for the medical treatment of a patient (Pt), in particular for artificial respiration, Among them, The measurement system (100) comprises - a sensor assembly (50), - a pressure sensor assembly (36, 57), and - a sensor-fluid guiding unit (52, 60, 56), wherein the sensor assembly (50) is designed to measure at least one property of a measurement gas mixture (MGg), wherein the measurement gas mixture (MGg) contains a gas sample (Gp) to be investigated, wherein the property or properties of the measurement gas mixture (MGg) are preferably the respective fractions {Con[O2](t), Con[CO2](t)} of at least one component (O2, CO2, AGas) of the measurement gas mixture (MGg), wherein, during the establishment of a fluid connection (40) at least temporarily between - a patient-side coupling unit (21) arranged in and / or at the body of the patient (Pt) and - a medical device (1) by means of a patient-fluid guiding unit (32, 33), the monitoring method is carried out, wherein the monitoring method comprises steps which are automatically carried out, namely - branching off the gas sample (Gp) from the patient-fluid guiding unit (32, 33) at a branching point (34) and guiding it through the sensor-fluid guiding unit (52, 60, 56) and the sensor assembly (50), - Measure the pressure [P aw (t)] at the bifurcation point (34), - Measure the pressure [P cell (t)] in the measurement system (100) at or in the measurement location (Mp.3) of the sensor-fluid guiding unit (52, 60, 56), and - determining whether an indication of a leak (L) in the sensor-fluid guiding unit (52, 60, 56) occurs, wherein the route of the sensor-fluid guiding unit (52, 60, 56) from the branching point (34) to the measurement location (Mp.3) is divided into a sequence of sections with at least two serially connected sections (Sg.1, Sg.2, Sg.3), wherein, for each section (Sg.1, Sg.2, Sg.3), a pneumatic resistance {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} is preset, which is related to the volume flow (Q) through the section (Sg.1, Sg.2, Sg.3), wherein, at least when an indication of a leak (L) is detected, further steps are carried out, namely Measure or detect said total volume flow (Q ges ), where said total volume flow is the volume flow through which the measurement-gas mixture (MGg) flows through said sensor assembly (50), Measure the actual pressure difference [ΔP cell (t)], where the actual pressure difference is the difference between the pressure [P cell (t)] at the measurement location (Mp.3) and the pressure [P aw (t)] at the bifurcation point (34). Determine a measure for the relative leakage volume flow (α rel ), wherein, the relative leakage volume flow rate (α rel ) is at -induced volumetric flow (Q) through the leak (L) to be detected Leak ) and - Measured or detected total volumetric flow (Q ges ) the ratio between, For each transition section (Mp.1, Mp.2) between a section (Sg.1, Sg.2) and a section (Sg.2, Sg.3) arranged downstream of the sequence of said sections, the transition-section pressure difference (ΔP Mp.1 , ΔP Mp.2 ) is calculated separately, wherein the transition-section pressure difference (ΔPMp.1, ΔPMp.2) is the pressure difference caused when the leak (L) occurs at this transition section (Mp.1, Mp.2), and wherein the transition-section pressure difference (ΔPMp.1, ΔPMp.2) is calculated using - the total volumetric flow (Q ges ) - the relative leakage volume flow rate (α rel ), and - the preset pneumatic resistances {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} of the sections (Sg.1, Sg.2, Sg.3), and When using the actual pressure difference [ΔP cell (t)] and the said or each calculated transition-section pressure difference (ΔPMp.1, ΔPMp.2) identifying the section (Sg.1, Sg.2, Sg.3) which causes the indication of the leak (L).

2. The monitoring method according to claim 1, characterized in that The measurement system (100) includes a fluid delivery unit (55), wherein the fluid delivery unit (55) is switchable on and off, wherein the switched-on fluid delivery unit (55) is designed to branch off a gas sample (Gp) to be investigated from the patient-fluid guiding unit (32, 33) and to convey it to the sensor assembly (50), and Among them, the step of measuring the pressure [P cell (t)] in the measurement system (100) is performed during the shut-off period of the fluid delivery unit (55).

3. The monitoring method according to any one of the preceding claims, characterized in that Steps for determining a measure for said relative leakage volume flow (α rel ) it includes steps, namely - the sensor assembly (50) measures the fractions {Con[O2](t), Con[CO2](t)} of the components of the measurement gas mixture (MGg) as the said or one characteristic, wherein the components are in particular oxygen or carbon dioxide, and in use the fractions {Con[O2](t), Con[CO2](t)} of the components of the measurement gas mixture (MGg), The total volumetric flow (Q ges ), and The preset fractions (Con[O2] env , Con[CO2] env ) of the components in the gas mixture in the surroundings of the measurement system (100) in the case where Determine a measure for said relative leakage volume flow (α rel ), and / or it includes steps, namely - the sensor assembly (50) measures the thermal conductivity [WLF(t)] of the measurement gas mixture (MGg), and in use the measured thermal conductivity [WLF(t)] of the measurement gas mixture (MGg), The total volume flow (Q ges ), and The preset thermal conductivity (WLF) of the gas mixture in the surroundings of the measurement system (100) env in the case of Determine a measure for the relative leakage volume flow (α rel ).

4. The monitoring method according to any one of the preceding claims, characterized in that Based on the determined relative leakage volume flow rate (α rel ), it is determined whether an index for the leakage part (L) appears.

5. The monitoring method according to any one of the preceding claims, characterized in that the sensor assembly (50) measures the respective time courses of the respective fractions {Con[O2](t), Con[CO2](t)} of at least two different components (O2, CO2) of the measurement gas mixture (MGg), and a determination is made based on the two measured time courses as to whether an indicator for a leak (L) has occurred.

6. The monitoring method according to any one of the preceding claims, characterized in that at least once when it has been determined that no leak has occurred, Calculate the expected pressure difference (ΔP cell )(t)) between the pressure [P aw (t)] at the measurement location (Mp.3) and the pressure [P exp (t)] at the bifurcation point (34). Among them, for the calculation of the said expected pressure difference (ΔP exp ), use - Measured or detected total volumetric flow (Q ges ), and - the preset pneumatic resistances {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} of the sections (Sg.1, Sg.2, Sg.3), and If the measured actual pressure difference [ΔP cell (t)] deviates from the calculated expected pressure difference (ΔP exp ) by more than a preset limit value, a message of this result is then generated and preferably output in a human-perceivable form.

7. A measurement method for medical treatment, Among them, the measurement method being performed automatically and using a measurement system (100), wherein the measurement system (100) includes - a sensor assembly (50), - a pressure sensor assembly (36, 57), and - a sensor-fluid guiding unit (52, 60, 56) wherein the measurement method is performed during the establishment of a fluid connection (40) at least temporarily between - a patient-side coupling unit (21) arranged in and / or at the body of the patient (Pt) and - a medical device (1) by means of a patient-fluid guiding unit (32, 33), wherein the measurement method includes steps, namely - branching the gas sample (Gp) off from the patient-fluid guiding unit (32, 33) at a branching point (34) and guiding it through the sensor-fluid guiding unit (52, 60, 56) and the sensor assembly (50), and - the sensor assembly (50) measuring at least one property of the measurement gas mixture (MGg), wherein the measurement gas mixture (MGg) comprises the gas sample (Gp) to be investigated, wherein the property or at least one property of the measurement gas mixture (MGg) is preferably the respective share {Con[O2](t), Con[CO2](t)} of at least one component (O2, CO2, AGas) of the measurement gas mixture (MGg), wherein the measurement method comprises a further step, namely - Measure the pressure [P aw (t)] at the bifurcation point (34), and - Measure the pressure [P cell (t)] in the measurement system (100) at or in the measurement location (Mp.3) of the sensor-fluid guiding unit (52, 60, 56), and - determining whether an indicator for a leak (L) in the sensor-fluid guiding unit (52, 60, 56) occurs, wherein the route of the sensor-fluid guiding unit (52, 60, 56) from the branching point (34) to the measurement location (Mp.3) is divided into a sequence of sections (Sg.1, Sg.2, Sg.3) with at least two serially connected sections, wherein for each section (Sg.1, Sg.2, Sg.3), a pneumatic resistance {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} is preset respectively, and the pneumatic resistance is related to the volume flow (Q) through the section (Sg.1, Sg.2, Sg.3), wherein at least when an indicator for a leak (L) is detected, a further step is performed, namely Measure or detect said total volume flow (Q ges ), where said total volume flow is the volume flow through which the measurement-gas mixture (MGg) flows through said sensor assembly (50), Measure the actual pressure difference [ΔP cell (t)], where the actual pressure difference is the difference between the pressure [P cell (t)] at the measurement location (Mp.3) and the pressure [P aw (t)] at the bifurcation point (34). Determine a measure for the relative leakage volume flow (α rel ), wherein, the relative leakage volume flow rate (α rel ) is at -induced volumetric flow (Q) through the leakage portion (L) to be detected Leak ) and - Measured or detected total volume flow (Q ges ) the ratio between, For each transition section (Mp.1, Mp.2) between a section (Sg.1, Sg.2) and a section (Sg.2, Sg.3) arranged downstream of the sequence of said sections, the transition-section pressure difference (ΔP Mp.1 , ΔP Mp.2 ) is calculated separately, wherein the transition-section pressure difference (ΔPMp.1, ΔPMp.2) is the pressure difference caused when the leak (L) occurs at this transition section (Mp.1, Mp.2), and wherein the transition-section pressure difference (ΔPMp.1, ΔPMp.2) is used in - the total volume flow (Q ges ) - the relative leakage volume flow rate (α rel ) and - calculating using the preset pneumatic resistances {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} of the sections (Sg.1, Sg.2, Sg.3), and when using the actual pressure difference [ΔP cell (t)] and the said or each calculated transition-section pressure difference (ΔPMp.1, ΔPMp.2) identifying the section (Sg.1, Sg.2, Sg.3) that causes the indicator for the leak (L).

8. A monitoring device (30) for monitoring a measurement system (100) for the medical treatment of a patient (Pt), in particular for artificial respiration, Among them, the measurement system (100) comprising - a sensor assembly (50), - a pressure sensor assembly (36, 57), and - a sensor-fluid guiding unit (52, 60, 56), wherein the sensor assembly (50) is designed to measure at least one property of the measurement gas mixture (MGg), wherein the measurement gas mixture (MGg) contains the gas sample (Gp) to be investigated, Wherein, at least one characteristic of the measurement-gas mixture (MGg) is preferably the respective fraction {Con[O2](t), Con[CO2](t)} of at least one component (O2, CO2, AGas) of the measurement-gas mixture (MGg). Wherein, the measurement system (100) is connected or connectable to a patient-fluid guiding unit (32, 33). Wherein, the patient-fluid guiding unit (32, 33) is designed for - a patient-side coupling unit (21) arranged in and / or at the body of the patient (Pt) and - a medical device (1) to establish a fluid connection (40) therebetween. Wherein, the measurement system (100) is designed for - branching off a gas sample (Gp) from the patient-fluid guiding unit (32, 33) at a bifurcation point (34), and - guiding it through the sensor-fluid guiding unit (52, 60, 56) and the sensor assembly (50). Wherein, the pressure sensor assembly (36, 57) is designed for - Measure the pressure [P aw (t)] at the bifurcation point (34), and - Measure the pressure [P cell (t)] in the measurement system (100) at the measurement position (Mp.3) at the sensor-fluid guiding unit (52, 60, 56). Wherein, the route of the sensor-fluid guiding unit (52, 60, 56) from the bifurcation point (34) to the measurement location (Mp.3) is divided into a sequence of sections (Sg.1, Sg.2, Sg.3) with at least two serially connected sections. Wherein, for each section (Sg.1, Sg.2, Sg.3), a pneumatic resistance {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} is preset respectively, and the pneumatic resistance is related to the volume flow (Q) through the section (Sg.1, Sg.2, Sg.3). Wherein, the monitoring device (30) is designed for automatically determining whether an indicator for a leak section (L) in the sensor-fluid guiding unit (52, 60, 56) occurs. Wherein, the monitoring device (30) is also designed for performing additional steps, more precisely at least as a reaction to detecting an indicator for the leak section (L). Measuring or detecting the total volume flow (Q ges ), where the total volume flow is the volume flow through which the measurement-gas mixture (MGg) flows through the sensor assembly (50), Measure the actual pressure difference [ΔP cell (t)], where the actual pressure difference is the pressure [P cell (t)] at the measurement location (Mp.3) minus the pressure [P aw (t)] at the bifurcation point (34). Determine a measure for the relative leakage volume flow (α rel ), wherein, the relative leakage volume flow rate (α rel ) is at - The induced volumetric flow rate (Q) through the leakage portion (L) to be detected Leak ) and - Measured or detected total volume flow (Q ges ) The ratio between For each transition section (Mp.1, Mp.2) between a section (Sg.1, Sg.2) and a section (Sg.2, Sg.3) arranged downstream of the sequence of said sections, the transition-section pressure difference (ΔP Mp.1 , ΔP Mp.2 ) is calculated separately, Wherein, the transition-section pressure difference (ΔPMp.1, ΔPMp.2) is the pressure difference caused when the leak section (L) appears at this transition section (Mp.1, Mp.2), and when using the actual pressure difference [ΔP cell (t)] and the said or each calculated transition - pressure difference (ΔPMp.1, ΔPMp.2) identifying the section (Sg.1, Sg.2, Sg.3) that causes the indicator for the leak section (L). Wherein, the monitoring device (30) is designed for, when using - the total volume flow (Q ges ) - the relative leakage volume flow rate (α rel ), and - the preset pneumatic resistances {R[Sg.1](Q), R[Sg.2](Q), R[Sg.3](Q)} of the section (Sg.1, Sg.2, Sg.3), calculating the transition-section pressure difference (ΔPMp.1, ΔPMp.2).

9. A measurement system (100) for monitoring a medical treatment of a patient (Pt), in particular artificial respiration. Among them, The measurement system (100) comprises - a sensor assembly (50), - a pressure sensor assembly (36, 57), - a sensor-fluid guiding unit (52, 60, 56), and - The monitoring device (30) according to claim 8, wherein the sensor assembly (50) is designed to measure at least one property of the measurement-gas mixture (MGg), wherein the measurement-gas mixture (MGg) contains the gas sample (Gp) to be investigated, wherein the property or properties of the measurement-gas mixture (MGg) are preferably the respective fractions {Con[O2](t), Con[CO2](t)} of at least one component (O2, CO2, AGas) of the measurement-gas mixture (MGg), wherein the measurement system (100) is connected or connectable to the patient-fluid guiding unit (32, 33), wherein the patient-fluid guiding unit (32, 33) is designed for - a patient-side coupling unit (21) arranged in and / or at the body of the patient (Pt) and - a medical device (1) to establish a fluid connection (40) therebetween, wherein the measurement system (100) is designed to branch off a gas sample (Gp) from the patient-fluid guiding unit (32, 33) at a bifurcation point (34) and guide it through the sensor-fluid guiding unit (52, 60, 56) to the sensor assembly (50), wherein the pressure sensor assembly (36, 57) is designed for - Measure the pressure [P aw (t)] at the bifurcation point (34), and - Measure the pressure [P cell (t)] in the measurement system (100) at the measurement position (Mp.3) at the sensor-fluid guiding unit (52, 60, 56), and wherein the monitoring device (30) is designed to monitor the measurement system (100).

10. A treatment assembly (200) for the medical treatment of a patient (Pt), in particular for artificial respiration, Among them, The treatment assembly 200 comprises - a medical device (1), - a patient-fluid guiding unit (32, 33), - a patient-side coupling unit (21), and - a measurement system (100) according to claim 9, wherein the patient-side coupling unit (21) is arranged or arrangeable in and / or at the body of the patient (Pt), wherein the patient-fluid guiding unit (32, 33) establishes a fluid connection between the medical device (1) and the patient-side coupling unit (21), and wherein the measurement system (100) - is connected or connectable to the patient-fluid guiding unit (32, 33), and - is designed to branch off a gas sample (Gp) from the patient-fluid guiding unit (32, 33) at a bifurcation point (34) and measure at least one property of the measurement-gas mixture (MGg), wherein the measurement-gas mixture (MGg) contains the branched-off gas sample (Gp), and wherein the property or properties are preferably the respective fractions of at least one component (O2, CO2, AGas) of the measurement-gas mixture (MGg).

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