EP4175543A2

EP4175543A2 - Sensor arrangement, medical apparatus, exhalation valve, and method for determining a carbon dioxide concentration in a measurement gas

Info

Publication number: EP4175543A2
Application number: EP21743060.2A
Authority: EP
Inventors: Hans-Ullrich Hansmann
Original assignee: Draegerwerk AG and Co KGaA
Current assignee: Draegerwerk AG and Co KGaA
Priority date: 2020-07-03
Filing date: 2021-06-28
Publication date: 2023-05-10
Also published as: DE102020117619A1; WO2022002824A3; US20230330367A1; WO2022002824A2; CN115734748A

Abstract

The present invention relates to a sensor arrangement (10) for a medical apparatus (12), having a sensor unit (11) for determining a carbon dioxide concentration in measurement gas, a branch line (14) for diverting the measurement gas from a main line (15) of the medical apparatus (12) and for conveying the diverted measurement gas to the sensor unit (11), and at least one HME filter (16, 17) for filtering the diverted measurement gas. The invention further relates to a medical apparatus (12) having a sensor arrangement (10) according to the invention, an exhalation valve (25) for a medical apparatus (12) according to the invention, and a method for determining a carbon dioxide concentration.

Description

Sensor arrangement, medical device, expiration valve and method for determining a carbon dioxide concentration in a measurement gas

description

The present invention relates to a sensor arrangement for a medical device, in particular for a ventilator, having a sensor unit for determining a carbon dioxide concentration in measurement gas, and a branch line for branching off the measurement gas from a main line of the medical device and for routing the branched measurement gas to the sensor unit. The invention also relates to a medical device, in particular a ventilator, an expiration valve for a medical device and a method for determining a carbon dioxide concentration in a measurement gas.

Carbon dioxide is one of the most important parameters for assessing ventilation efficiency when a person is ventilated using a ventilator. Precise and reliable monitoring of the carbon dioxide concentration is therefore of crucial importance during ventilation.

Various physical and / or chemical methods can be used to determine the carbon dioxide concentration. For example, the carbon dioxide concentration can be recorded with the aid of infrared sensors, electrochemical sensors, a colorimetric method, or with the aid of mass spectrometers. Some of these methods have a complex measurement setup, are accordingly expensive and / or are not suitable for continuous recording of the carbon dioxide concentration.

Furthermore, a system is known in which, by means of the thermal conduction of a measurement gas or a gas sample at a sensor unit, conclusions can be drawn about the carbon dioxide concentration in the measurement gas. To determine the carbon dioxide concentration, for example, a sensor unit close to a so-called mainstream or a main line is gassed with inspiration gas and expiration gas by means of diffusion. Such a system is from the German patent application DE 102010047 159 A1 is known. A hydrophobic barrier against condensing moisture is also proposed there. The problem with this system is that cross-influences via gas parameters such as the measuring gas temperature and / or the measuring gas humidity synchronously with the breathing phases, i.e. inspiration and expiration, lead to insufficiently accurate determination of the carbon dioxide concentration in the measuring gas due to the lack of selectivity in the sensor unit. In other words, the changing humidity caused by inspiration and expiration leads to changing humidity on the sensor depending on the occupancy of the hydrophobic barrier. This can lead to changed measured values and a corresponding measurement inaccuracy as well as to a partial to complete gas lock, which means that the desired measurement can no longer be carried out.

The object of the present invention is to at least partially take into account the problems described above. In particular, it is the object of the present invention to create a device and a method for determining the carbon dioxide concentration in measurement gas from a generic medical device as simply, inexpensively and precisely as possible.

The above object is achieved by the claims. In particular, the above object is achieved by the sensor arrangement according to claim 1, the medical device according to claim 15, the expiration valve according to claim 22, and the method according to claim 25. Further advantages of the invention emerge from the subclaims, the description and the figures. Features that are described in connection with the sensor arrangement naturally also apply in connection with the medical device according to the invention, the expiration valve according to the invention, the method according to the invention and vice versa, so that with regard to the disclosure of the individual aspects of the invention, reference is always made and / or are reciprocated can.

According to a first aspect of the present invention, a sensor arrangement for a medical device is provided. The sensor arrangement includes a Sensor unit for determining a carbon dioxide concentration in measurement gas, a branch line for branching off the measurement gas from a main line of the medical device and for guiding the branched measurement gas to the sensor unit, and at least one HME filter for filtering the branched measurement gas.

In the context of the present invention, it was recognized that using an HME filter to filter the measurement gas, temperature and humidity differences in the measurement gas, which are caused during inspiration and expiration of the person or a patient, are buffered, compensated, reduced and / or can be smoothed so that the carbon dioxide concentration can be determined or measured and / or calculated much more precisely in comparison to a system without an HME filter.

It was also recognized that the HME filter used has no significant and / or adverse effect on other gas components to be measured. In other words, the humidity and the heat of the measurement gas are evenly distributed over time without influencing the actually desired measurement effect of the differences in heat conduction with regard to the existing and missing carbon dioxide. That is to say, the HME filter has no or essentially no influence on the supply of the amount of carbon dioxide to the sensor unit. The gas transport may only be delayed somewhat by the volume of the HME filter. However, this has no or at least no significant influence on the desired determination of the carbon dioxide concentration in the measurement gas. Changes in heat conduction that result from changes in temperature and / or humidity in the measurement gas and occur synchronously with the breathing phases are among the main causes of inaccurate carbon dioxide measurements. With the present invention, this problem can be taken into account in a simple, inexpensive and effective manner.

In medical technology, an HME filter is understood to mean a heat-moisture-exchange filter and / or a filter housing with such a filter material. The HME filter can therefore be understood as a heat and moisture exchanger. HME filters have so far been used in particular in a mainstream or in a main line of a ventilator or a corresponding medical device used where they are always alternated with inspiratory gas and expiratory gas in the ventilation cycle. HME filters have so far served in particular to adequately humidify the inspiratory gas or the inhaled air of the patient and to avoid cross-contamination in the main line. The proposed HME filter of the sensor arrangement is preferred in terms of its size and / or function for buffering, balancing, reducing and / or smoothing temperature and / or humidity differences of the branched measurement gas for the duration of at least one breath, i.e. including inspiration and expiration, configured. The HME filter can accordingly be provided not only for classic filtering of the measurement gas, but in particular for buffering, equalizing, reducing and / or smoothing the temperature and / or humidity differences in the branched measurement gas. The at least one HME filter can have a filter housing and filter material for filtering the measurement gas in the filter housing. The filter housing can be configured as a rigid filter housing or as a flexible or elastically deformable filter housing which, for example, is tubular. The HME filter can also be designed without a filter housing and exclusively as the functionally relevant HME filter material, for example in the form of a hose insert.

The measurement gas can be conveyed, in particular sucked, from the main line into the branch line and from there to the sensor unit using a fluid delivery unit, in particular a pump. Because the HME filter only has the extracted measurement gas flowing through it, i.e. in particular not all of the gas in the main line, it can be designed to be smaller, in particular many times smaller, than a conventional HME filter used in the main line. The sensor arrangement can have a fluid delivery unit, in particular a pump, for delivering and / or sucking measurement gas from the main line into the branch line and from there to the sensor unit.

The HME filter is preferably configured in a measurement gas flow direction to the sensor unit upstream of the sensor unit and / or in a state installed in the ventilator upstream of the sensor unit, so that the measurement gas can flow through the HME filter before it reaches the sensor unit. The sensor arrangement is preferably designed for use in and / or with a medical device in the form of a ventilator. The branch line preferably has a flexible hose line for guiding the branched measurement gas to the sensor unit. Furthermore, the branch line can be designed in the form of the flexible hose line. In addition, it is possible for the branch line to have, in addition to the hose line, further functional components such as adapter and / or connection components for connecting the hose line to the main line, to the sensor unit and / or to the HME filter.

The sensor unit can be designed and / or configured in accordance with a sensor described in DE 10 2010 047 159 A1 for determining the carbon dioxide concentration in the measurement gas. The branch line has a smaller, in particular a multiple smaller, inner diameter than a generic main line of a ventilator.

According to a further embodiment of the present invention, it is possible for the at least one HME filter in a sensor arrangement to be configured in the branch line. The sensor arrangement can thus be made available in a particularly compact and correspondingly space-saving manner. Furthermore, the sensor arrangement can easily be installed on and / or in the medical device. The at least one HME filter can already be configured in the branch line during installation. The at least one HME filter is designed in particular within a line volume of the branch line. The branch line can, for example, have a hose line, the at least one HME filter being configured at least in part of the inner volume of the hose line. In other words, at least part of a hose jacket of the hose line can enclose the at least one HME filter in a jacket shape over the entire length of the at least one HME filter or over part of the length of the HME filter. The at least one HME filter can be designed, so to speak, in the form of a hose insert. The at least one HME filter is preferably designed in a form-fitting and / or force-fitting manner in the branch line. The outer circumferential surface of the at least one HME filter can accordingly be complementary to an inner circumferential surface of the branch line, in particular to an inner circumferential surface of the hose line the branch line. The outer diameter of the at least one HME filter can consequently correspond to the inner diameter at the point of the hose line at which the at least one HME filter is positioned in the hose line, or to insert the at least one FIME filter into the branch line, it can be slightly smaller than the inner diameter be at the point of the hose line.

In a sensor arrangement according to the invention, it is also possible for the branch line to have an end section on the main line for connecting the branch line to the main line and a sensor-side end section for connecting the branch line to the sensor unit, an HME filter being arranged on and / or in the main line-side end section. The one, in particular individual, HME filter is thus arranged as directly and / or close to the main line as possible. As a result, the intended buffering or equalization of the temperature and / or moisture differences in the measurement gas can be carried out by the HME filter as early as possible upstream of the sensor unit. Undesired condensate in the branch line downstream of the HME filter and / or upstream of the sensor unit can thereby be effectively prevented or at least effectively reduced. This is particularly advantageous if the branch line has a longer hose line and critical conditions, for example cold outside temperatures, prevail, in which the temperature in the hose line falls well below the mask temperature or falls below the dew point of the mean humidity. The fact that the sensor-side end section is designed to connect the branch line to the sensor unit can be understood to mean that a connection port for fluid-tight connection of the branch line to the main line, in particular to a mating connection port of the main line, is configured on the sensor-side end section. The fluid-tight connection can be understood to mean a connection through which the measurement gas slides, in particular sucked, out of the main line into the branch line without leaks. The fact that the HME filter is arranged on and / or in the main line-side end section can be understood to mean that the HME filter, for example in the form of a hose insert, at least partially in the main line-side end section of the branch line or a hose line of the branch line is arranged, or is arranged as an attachment at least partially outside of such a hose line on the hose line.

Furthermore, it is possible in a sensor arrangement according to the present invention that the branch line has an end section on the main line for connecting the branch line to the main line and a sensor-side end section for connecting the branch line to the sensor unit, the sensor arrangement having a first HME filter on and / or in the main line-side end section and a second HME filter on and / or in the sensor-side end section. The second HME filter on and / or in the sensor-side end section can effectively protect the sensor unit from condensing moisture. This in turn leads to a measurement gas supply to the sensor unit that is as free from moisture as possible and consequently to correspondingly precise measurement results. The two HME filters, viewed along the branch line, are preferably designed at a distance from one another, for example by more than 50 cm, in particular in a range between 50 cm and 150 cm from one another. The two HME filters preferably have the same size and / or shape.

It is also possible that in a sensor arrangement according to the present invention, the first HME filter in the main line-side end section of the branch line is designed in the form of a hose insert, the branch line, viewed in a flow direction of the measurement gas through the branch line, at the level of the HME filter has a larger inner diameter than in a region downstream of the HME filter. Because the branch line downstream of the HME filter is less susceptible to condensing moisture in the measurement gas, the internal diameter of the branch line downstream of the HME filter can be designed to be relatively small. Material and costs can thus be saved and the branch line can be designed to be compact. In particular, a dead space in the branch line and / or a measurement delay can thereby be kept relatively small. The direction of flow of the measurement gas through the branch line is in a state of the sensor arrangement in which it is in the medical unit is installed. The flow direction runs from the main line through the branch line, there through the at least one HME filter arranged in and / or on the branch line, and downstream of the at least one HME filter to the sensor unit and beyond, for example to a pump, the downstream the sensor unit can be arranged for sucking off the measurement gas from the main line into the branch line. The inside diameter at the level of the HME filter is designed to be somewhat larger than the inside diameter downstream of the HME filter in order to be able to accommodate the HME filter with a correspondingly large diameter or outside diameter. In this way, the requirements for a sufficient buffer effect by the HME filter and, nevertheless, a space-saving and, if possible, delay-free forwarding of the measuring gas to the sensor unit can be taken into account.

In a sensor arrangement according to the invention at the level of the first HME filter, the inner diameter of the branch line can have a value in a range between 2 mm and 4 mm and the inner diameter of the branch line downstream of the first HME filter can have a value in a range between 0.5 mm and 2 mm. Extensive tests within the scope of the present invention have shown that with a diameter in the range between 2 mm and 4 mm, possible condensate upstream of the HME filter is relatively unproblematic. The diameter in a range between 0.5 mm and 2 mm downstream of the HME filter has proven to be an advantageous compromise with regard to a robust branch line and nevertheless the smallest possible dead space or a correspondingly low measurement delay. The branch line or hose line can be used to produce a flow velocity in a range between 1 m / s and 1.5 m / s with a volume flow in a range between

50 ml / min and 70 ml / min.

In the case of a sensor arrangement according to the present invention, the at least one HME filter can furthermore be designed in the form of a hose insert in the main line-side end section of the branch line, the branch line through the Considered branch line, in a region upstream of the at least one HME filter has a larger inner diameter than downstream of the at least one HME filter. This can prevent condensate upstream of the at least one HME filter from clogging the branch line and downstream of the at least one HME filter the desired compromise with regard to a robust branch line and nevertheless the smallest possible dead space or a correspondingly small measurement delay . It has been found to be advantageous if the internal diameter of the branch line upstream of the at least one HME filter has a value in a range between 1.5 mm and 4 mm and the internal diameter of the branch line downstream of the at least one HME filter has a value in a range between 0.5 mm and 2 mm. Advantages in terms of simple manufacture of the branch line can be achieved if the areas upstream of the HME filter and at the level of the HME filter have the same inner diameter. For example, a hose line of the branch line with an inside diameter that has the same value from an area upstream of the HME filter in the sensor-side end section to an area in which the HME filter is configured in the hose line, and only downstream of the HME filter has a smaller inner diameter than upstream of the HME filter or in the area of the HME filter, be configured. The same can be configured in an analogous manner with regard to an outer diameter of such a hose line. It is also possible that the area upstream of the HME filter or the corresponding internal volume of a hose line of the branch line has a smaller internal diameter than in the area of the HME filter, and preferably nevertheless larger than in the area downstream of the HME filter. The inner diameter of a hose line described above can therefore remain constant over the area upstream of the HME filter to the area in which the HME filter is configured in the hose line and can differ from the area in which the HME filter is configured in the hose line is, to the area downstream of the HME filter, decrease, or from the area upstream of the HME filter to the area in which the HME filter is configured in the hose line, and from the area in which the HME filter is designed in the hose line, towards the area downstream of the HME filter, reduce it again.

The at least one HME filter preferably has a length in a range between 8 mm and 20 mm and a width in a range between 2 mm and 6 mm. In particular, the at least one HME filter has a length in a range between 10 mm and 15 mm and a width in a range between 3 mm and 5 mm. According to the invention, the at least one HME filter is flowed through as far as possible only with the measurement gas or the suction flow and can thus be kept relatively small. The well-known HME filters that have been used in the main line up to now are designed for patient gas flows of up to 180 1 / min. The at least one HME filter according to the present invention is designed for a flow of measurement gas in a range of, for example, between 30 ml / min and 100 ml / min, in particular in a range between 40 ml / min and 70 ml / min. The branch line can therefore be designed correspondingly small, material and space-saving and inexpensive. The at least one HME filter is preferably cylindrical and designed with a length in a range between 8 mm and 20 mm and a diameter in a range between 2 mm and 6 mm.

According to a further embodiment variant of the present invention, it is possible, in a sensor arrangement, for the branch line to have a hose line with a length in a range between 80 cm and 150 cm. In tests within the scope of the present invention it was found that an effective buffer effect with regard to the desired temperature and / or moisture compensation can be achieved even with this hose length. In particular, the hose line has a length in a range between 90 cm and 110 cm. The hose line has the above-described inside diameter in a range between 0.5 mm and 2 mm, preferably over a length of the hose line in a range between 80 cm and 120 cm.

Furthermore, in a sensor arrangement according to the invention, the branch line can have a hose line made of silicone or at least partially made of silicone. In experiments within the scope of the present invention has been shown that when a silicone hose is used in the branch line, a counter-drying effect is exerted on the measurement gas, which leads to further buffering and / or smoothing of fluctuations in humidity.

In the case of a sensor arrangement according to the present invention, it can be of further advantage if the branch line has a hose line with a PVC coating on an outer circumferential surface of the hose line. The PVC coating enables environmental influences on the measurement gas, which could influence the measurement result, to be prevented in a simple and inexpensive manner. The PVC coating preferably has a thickness in a range between 0.1 mm and 0.4 mm.

In a sensor arrangement according to a further embodiment variant of the present invention, it is possible for the branch line to have a Luer lock connection for establishing a fluid connection with the main line. In this way, the branch line can be connected or connected to the main line and / or a connection section of the main line particularly quickly and easily. On the main line, the breathing mask and / or an exhalation valve on the breathing mask of the medical system, a counter-Luer lock connection for a corresponding connection between the main line and the branch line, between the breathing mask and the branch line and / or between the exhalation valve and the branch line be designed.

In a preferred embodiment of a sensor arrangement according to the invention, the at least one HME filter can also have a microporous plastic foam. In this way, the desired equalizing effects on the temperature and / or the humidity in the measurement gas can be achieved particularly reliably. The at least one HME filter can in particular have an open-pored, salt-coated plastic foam. The at least one HME filter can therefore have a humidification efficiency of approx. 30 mg water per liter with respect to the inspiratory gas.

According to a further aspect of the present invention there is a medical device made available for ventilation of a person. The medical device has a main line for guiding inspiratory gas and for guiding expiratory gas, as well as a sensor arrangement as described above, the branch line being designed to branch off a measurement gas from the main line and the at least one HME filter being configured to filter the branched measurement gas. The medical device according to the invention thus brings the same advantages as have been described in detail with reference to the device according to the invention. The medical device can furthermore have a breathing mask and / or an expiration valve, wherein the main line can be configured for conveying inspiratory gas to the breathing mask and for conveying expiratory gas away from the breathing mask and / or towards the expiratory valve. The branch line can be designed to branch off the measurement gas from the main line through the breathing mask and / or through the expiration valve. In a medical device according to the invention, an expiration valve can accordingly be configured on the breathing mask, the main line extending from an exhalation area of the breathing mask to the expiration valve and from there, i.e. in and / or on the expiration valve, the branch line on the main line for branching off the measurement gas from the main line , is designed. The medical device can also have a fluid delivery unit, in particular a pump, for delivering, pumping and / or sucking off the measurement gas or inspiratory gas and expiratory gas from the main line into the branch line. The at least one HME filter is configured in particular to buffer and / or smooth temperature and / or humidity changes in the measurement gas for the duration of at least one breath.

In a medical device according to a preferred embodiment, it is possible for the main line to have an inspiratory gas line section for conveying the inspiratory gas and an overall gas line section for conveying the inspiratory gas and the expiratory gas, the branch line being designed to branch off the measurement gas from the overall gas line section. That is, the measurement gas will be branched off from a part of the main line through which both inspiratory gas and expiratory gas are passed while the medical device is in operation. The carbon dioxide concentration in the measurement gas is in particular via a Carbon dioxide difference between the inspiratory gas and the expiratory gas is determined or measured and calculated by means of a computing unit of the medical device. Including that the sensor unit to determine the

Carbon dioxide concentration in the measurement gas is configured to be understood in particular that the sensor unit is used to determine the

Carbon dioxide concentration is used. The fact that the carbon dioxide concentration is determined by means of the sensor unit can be understood to mean that the carbon dioxide concentration is determined on the basis of various measurements and calculations and the sensor unit is used here, or, in other words, that the carbon dioxide concentration in the measurement gas is determined on the basis of a thermal conductivity of the measurement gas measured by the sensor unit will. The carbon dioxide differences can be determined by means of the sensor unit and the carbon dioxide concentration is calculated on the basis of the measured values and / or determined on the basis of, for example, a look-up table. As already mentioned above, the measurement gas therefore preferably comprises inspiration gas and expiration gas. Accordingly, the relative carbon dioxide concentration in the expiratory gas can be determined from the carbon dioxide difference between the inspiratory gas and the expiratory gas. The branch line is accordingly configured to branch off the measurement gas, which comprises the inspiratory gas and the expiratory gas, from the main line through the at least one HME filter to the sensor unit.

In a medical device according to the invention, the at least one HME filter can be located within the entire gas line section. That is to say, the branch line is not only connected and / or tied to the main line, but extends into the main line, more precisely into the entire gas line section. The HME filter and / or the branch line with an HME filter arranged therein can, so to speak, be arranged and / or guided within the main line. The outer circumferential surface of the branch line can be spaced apart from an inner circumferential surface of the main line in a region in which the HME filter is configured in and / or on the branch line. As a result, a particularly compact yet functional design can be achieved. The main line can also lead to an expiration valve of the medical device or extend through at least a portion of the expiratory valve. In this case, the at least one HME filter can also be viewed as being designed within the expiratory filter. This also leads to a particularly compact and robust design. In particular, the HME filter can be effectively protected against environmental influences within the main line and / or the expiration valve.

In a medical device according to the present invention, at least a part of the branch line can extend from a position within the main line from the total gas line section into the inspiratory gas line section Inspiratory gas is designed to be performed. In other words, the branch line can be integrated and / or guided in at least part of the main line. The medical device can thus be provided in a particularly space-saving manner.

In the overall gas line section of a medical device according to the invention, an expiration valve can be configured for letting out expiratory gas from the medical device into the vicinity of the medical device, the at least one HME filter being configured in the expiration valve. Such a design variant can also be implemented in a relatively compact manner. With an HME filter integrated into the exhalation valve, when assembling the medical device, only the branch line has to be connected to the exhalation valve and then led to the sensor unit. The branch line can be replaced quickly, easily and inexpensively if necessary, for example in the form of a simple hose line. A position within the expiration valve means that the at least one HME filter and / or part of the branch line with the at least one HME filter arranged thereon and / or therein are arranged in a valve volume of the expiration valve through which the expiration gas and the inspiration gas of the Main line flow. The branch line is preferably connected to the expiration valve for branching off the measurement gas from the main line. For this purpose, the branch line can have a branch connection and the expiratory valve can have a counter-branch connection, for establishing a fluid-tight connection with the branch connection.

The medical device described here is preferably made available and / or designed in the form of a ventilator. The medical device can therefore be understood to mean a medical device for ventilating a person, in particular a patient. For this purpose, the medical device can also be configured in the form of an anesthesia device. The ventilator can preferably be configured and / or designed in the form of an emergency ventilator, a ventilator for use in an intensive care unit, a home ventilator, a mobile ventilator and / or a neonatal ventilator.

In the context of the present invention, an expiration valve is also provided for a medical device as described above for letting out expiratory gas from the medical device into the vicinity of the medical device. The expiratory valve has an HME filter integrated into the expiratory valve for filtering a measurement gas branched off from the medical device via the expiratory valve. The expiration valve according to the invention thus also has the advantages already described. The expiratory valve can have a breathing mask as mentioned above or a breathing mask with an expiratory valve installed thereon and / or at least partially therein with the features described can be and / or be made available.

An expiration valve according to the invention can have a valve connection for connecting a branch line for branching off the measurement gas from a main line of the medical device through the HME filter. A branch line as described above can be connected with one side to the valve connection and the other side to the sensor unit in order to lead the sample gas from the expiration valve and the HME filter integrated there to the sensor unit. The at least one HME filter can have a microporous plastic foam.

According to a further aspect of the present invention, there is also a A method for determining a carbon dioxide concentration in a measurement gas using a sensor arrangement, a medical device and / or an exhalation valve as described above is provided, the carbon dioxide concentration being determined by measuring the thermal conductivity of the expiratory gas. The method according to the invention thus also has the advantages described above.

Further measures improving the invention emerge from the following description of various exemplary embodiments of the invention, which are shown schematically in the figures. All of the features and / or advantages arising from the claims, the description or the figures, including structural details and spatial arrangements, can be essential to the invention both individually and in the various combinations.

They each show schematically:

Figure 1 shows a medical device according to a first embodiment of the present invention,

FIG. 2 shows a medical device according to a second embodiment of the present invention,

Figures 3 to 5 different sensor arrangements according to the present invention,

FIG. 6 shows a medical device according to a third embodiment of the present invention,

FIG. 7 shows a medical device according to a fourth embodiment of the present invention,

FIGS. 8 to 10 are diagrams for explaining the mode of operation of the present invention. Elements with the same function and mode of operation are each provided with the same reference symbols in the figures.

1 shows a medical device 12 in the form of a ventilator for ventilating a person 13 according to a first embodiment. The medical device 12 comprises a breathing mask 20 and a main line 15 for conveying inspiration gas to the breathing mask 20 and for conveying expiration gas away from the breathing mask 20. The main line 15 has an inspiration gas line section 21 and an expiration gas line section 23. A main pump 27 for supplying the inspiratory gas to the breathing mask 20 or to the person 13 is configured in the inspiratory gas line section 21. An expiration valve 25 is configured downstream of the main pump 27, viewed in a flow direction of the inspiratory gas. The expiration valve 25 is attached to the respiratory protection mask 20. Upstream of the expiration valve 25 and downstream of the main pump 27, only inspiration gas is conducted in the inspiration gas line section 21. In the expiration valve 25, through which the main line 15 also extends, inspiratory gas is conducted to the breathing mask 20 and expired gas is conducted away from the breathing mask 20 and via the expiration valve 25 into the vicinity of the medical device 12. This is shown in Fig. 1 for illustration with two separate arrows. In fact, the expiration valve 25 has a total gas line section 22 in which inspiration gas is conducted during inspiration and expiration gas is conducted during expiration.

The expiratory valve 25 shown in FIG. 1 also has a first HME filter 16. More precisely, the first HME filter 16 is integrated into the expiration valve 25. The first HME filter 16 is part of a sensor arrangement 10, which in turn is part of the medical device 12. The sensor arrangement 10 has a sensor unit 11 for determining a carbon dioxide concentration in the measurement gas and a branch line 14 for branching off the measurement gas from the main line 15 of the medical device 12 and for guiding the branched measurement gas to the sensor unit 11. The sensor arrangement 10 also has the first HME filter 16 and a second HME filter 17 for filtering the branched measurement gas. The second HME filter 17 is facing a direction of flow of the branched and extracted measurement gas is arranged upstream of the sensor unit 11 directly on the sensor unit 11.

To extract the measurement gas from the main line 15 or from the overall gas line section 22, the sensor arrangement 10 has a fluid delivery unit 24 in the form of a piezo pump. The fluid delivery unit 24 is arranged downstream of the sensor unit 11. According to FIG. 1, the first HME filter 16 is configured directly on a hose line of the branch line 14. The branch line 14 is thus connected to the expiration valve 25 by means of the hose line and there forms a fluid connection to the first HME filter 16 or enables a fluid connection from the main line 15 through the first HME filter 16 to the sensor unit 11. The expiration valve 25 has a valve connection for this purpose 26 in the form of a Luer lock connection for connecting the branch line 14 or the hose line.

The HME filters 16, 17 shown each have a microporous plastic foam for filtering the measurement gas or for achieving the desired buffer or compensation function with regard to the temperature and humidity differences that occur in the measurement gas.

To determine a carbon dioxide concentration in the measurement gas, in particular the thermal conductivity of the expiratory gas is measured in the sensor unit 11. The measurement is carried out by a micro-structured heating element on a thin membrane of the sensor unit. Next to the heating element is a thermophilic arrangement that measures an excess temperature of the gas near the heating element in relation to a silicon frame of the membrane. Further details on this can be found in German patent application DE 102010047 159 A1.

In Fig. 2, a medical device is shown according to a second embodiment. The expiration valve 25 shown in FIG. 2 is shown at a distance from the breathing mask 20. Nevertheless, the entire gas line section 22 can be understood as part of the expiration valve 25. According to the exemplary embodiment shown in FIG. 2, the first HME filter 16 is outside the expiratory valve 25 as well as outside the overall gas line section 22 and inside a hose line of the branch line 14. In this case, a valve connection 26 is configured on the hose line. The branch line 14 shown in Fig. 2 has an end section 18 on the main line side for connecting the branch line 14 to the main line 15 and a sensor-side end section 19 for connecting the branch line 14 to the sensor unit 11, the first HME filter 16 being arranged on the main line end section 18 and the second HME filter 17 is arranged on the sensor-side end section 19. More precisely, the two HME filters 16, 17 are each integrated as a hose insert in the hose line of the branch line 14. In the example shown, the hose line has a length of approx. 100 cm and consists of a silicone hose coated with PVC.

3 shows a sensor arrangement 10 in which the first HME filter 16 is designed in the main line-side end section 18 of the branch line 14 in the form of a hose insert, the branch line 14 or the hose line viewed in the flow direction of the measurement gas through the branch line 14 Height of the HME filter 16 has a larger inner diameter than in a region downstream of the HME filter 16. More specifically, the inside diameter of the branch pipe 14 at the level of the first HME filter 16 has a value of 3 mm and the inside diameter of the branch pipe 14 downstream of the first HME filter 16 has a value of 1 mm. In the sensor arrangement 10 shown in FIG. 3, the branch line 14 or the hose line upstream of the first HME filter 16 and in the area of the first HME filter 16 each have the same inner diameter and the same outer diameter. As a result, the branch line 14, viewed in the flow direction of the measurement gas through the branch line 14, has a larger internal diameter in the area upstream of the first HME filter 16 than downstream of the first HME filter 16. In the present case, the inside diameter is to be understood as meaning a diameter of a passage volume for conducting the measurement gas.

In the exemplary embodiment shown in FIG. 4, the branch line 14, viewed in the direction of flow of the measurement gas through the branch line 14, has in The area upstream of the first HME filter 16 also has a larger inner diameter than downstream of the first HME filter 16. However, the inner diameter and the outer diameter of the branch line in the area of the first HME filter 16 are greater than upstream of the first HME filter 16. More precisely, the inner diameter of the branch line 14 upstream of the first HME filter 16 has a value of 2 mm, which The inside diameter of the branch line 14 at the level of the first HME filter 16 has a value of 3 mm, and the inside diameter of the branch line 14 downstream of the first HME filter 16 has a value of 1 mm. The length of the cylindrical, first HME filter has a value of 13 mm and the diameter has a value of 3 mm.

In the embodiment variant of the sensor arrangement 10 shown in FIG. 5, the first HME filter 16 and the second HME filter 17 are each not configured inside the hose line, but on or outside the hose line. The branch line can be understood to mean a component arrangement which comprises the two HME filters 16, 17 and the hose line between the two HME filters 16, 17.

6 shows a medical device 12 according to a third embodiment. According to this embodiment, the first HME filter 16 is located in the branch line 14 and within the total gas line section 22 or within a passage volume of the total gas line section 22. In addition, the branch line 14 extends within the main line 15 from the total gas line section 22 into the inspiratory gas line section 21. With others In other words, the branch line 14 is routed coaxially or essentially coaxially in part within the main line 15 with respect to a longitudinal or extension direction of the branch line 14 or is enclosed by the main line in a jacket-like manner, in particular over several tens of centimeters.

FIG. 7 shows a medical device 12 in the form of a circulatory ventilator with an expiration valve 25 and an inspiration valve 29. The branch line 14 is connected according to FIG. The medical device 12 shown in FIG. 7 has a control unit 30 for controlling the fluid delivery unit 24 and the main pump 27. A generic HME filter 28, which is many times larger than the HME filters 16, 17 of the sensor arrangement 10, is also arranged downstream of the inspiration valve 29.

With reference to FIGS. 8 to 10, the mode of operation of the newly used HME filter 16 will then be explained. The heat conduction of a gas depends on the components of the gas. Since oxygen and nitrogen have similar thermal conductivity, the components are balanced with high concentrations. Depending on the setting of the medical device, the oxygen content in the inspiratory gas varies from, for example, 21% by volume in air to 100% by volume when using pure oxygen. The remainder is nitrogen. Noble gases such as argon take up just under 1% by volume. The exhaled gas stream also contains carbon dioxide, which is mixed in as a result of the gas exchange in the lungs. The oxygen content in the expiratory gas drops accordingly. Healthy people exhale a gas with about 4 to 5% by volume of carbon dioxide. The oxygen content is accordingly around 16 to 95% by volume. The proportion of noble gas remains constant. If the heat conduction is now continuously measured, the same gas mixture can be measured in the expiratory phase as in the inspiratory phase, the carbon dioxide being added during the expiratory phase. Even an intentionally increased proportion of noble gas, such as that used with helium for a lower viscosity, does not play a role in the changes in relation to the breathing phases. In simplified terms, it can therefore be said that only the change in thermal conductivity in the breathing phases has to be measured. The actual basic heat conduction does not matter. To make matters worse, however, the expiratory gas has been heated by the lungs to a temperature of approx. 36 ° C and has a high relative humidity of close to 100% at 36 ° C. The inspiratory gas or inhaled air is very different depending on the source and can be very dry via a pressure bottle supply to very humid when using a blower with room air and humidifier. The temperature of the inspiratory gas can also vary greatly depending on the climatic conditions.

Since the measurement by the sensor unit to determine the Carbon dioxide concentration is exposed to a constant change between inspiratory gas and expiratory gas, only the change in the measured values is preferably taken into account. Through the proposed use of at least the first HME filter 16, which is always flowed through alternately with expiratory gas and inspiratory gas from both breathing phases, the respective gas of both breathing phases is balanced in terms of humidity and temperature. So much FIME material is preferably used or at least the first HME filter 16 is dimensioned in such a way that no or only a slight change in signal due to temperature and humidity is noticeable in the slowest breathing cycles of the person 13. The average moisture content depends on the ventilation or climate situation. Various scenarios are shown in the following table:

The above observation shows that condensation can be critical in cold ambient conditions. The first HME filter 16, which is responsible for mixing the absolute humidities, is therefore installed and / or positioned as close as possible to the main line 15, i.e. in an area that is close to ambient temperatures and therefore does not allow any high absolute humidity.

FIG. 8 shows the curve of a typical ventilation in which the ventilation pressure is plotted over time. 9 shows a comparison between measured values for a medical device 12 in the form of a ventilator with the proposed HME filter 16 (below) and without an HME filter (above). In FIG. 9, therefore, in particular the buffering or equalization of the differences in moisture that would occur without the HME filter 16 can be recognized.

10 shows a diagram in which a change in voltage is plotted over time. On the basis of the voltage change, conclusions can be drawn about the carbon dioxide content. So it is important to have one as possible to get accurate voltage curve. If humid and warm gas is now sucked from the main line 15 to the sensor unit 11 without an HME filter 16, the heat conduction shows negative changes according to the lower, dotted line, since the heat conduction is better. The effect can be derived almost directly from the moisture differences shown in FIG. 9. The effect would now be superimposed with the positive change according to the solid line at the top in FIG. 10, which results from the admixture of 5% by volume of carbon dioxide in the expiratory gas. Since the difference in humidity and temperature cannot be foreseen during operation under unknown climatic conditions, there would be an uncertainty of approx. 10% in this case. In the case of very cool temperatures and / or a particularly dry inspiratory gas, even more. Using the proposed HME filter 16, the temperature and humidity-related voltage change can now be compensated for in accordance with the middle, dash-dotted graph. As a result, the influence on the voltage measurement with regard to the change in carbon dioxide between the inspiratory gas and the expired gas can be reduced and the measurement result can be improved accordingly.

In addition to the illustrated embodiments, the invention allows further design principles. That is to say, the invention should not be viewed as being restricted to the exemplary embodiments explained with reference to the figures.

Reference list

10 Sensor arrangement

11 sensor unit

12 medical device

13 person

14 branch line

15 main line

16 HME filters

17 HME filters

18 end section on the main line side

19 end section on the sensor side

20 breathing mask

21 Inspiratory gas line section

22 Total gas line section

23 Expiratory gas line section

24 fluid delivery unit

25 exhalation valve

26 valve connection

27 main pump

28 HME filters

29 Inspiratory valve

30 control unit

Claims

1. Sensor arrangement (10) for a medical device (12), comprising a sensor unit (11) for determining a carbon dioxide concentration in measurement gas, a branch line (14) for branching off the measurement gas from a main line (15) of the medical device (12) and for routing the branched measurement gas to the sensor unit (11), and at least one HME filter (16, 17) for filtering the branched measurement gas.

2. Sensor arrangement (10) according to claim 1, characterized in that the at least one HME filter (16) is configured in the branch line (14).

3. Sensor arrangement (10) according to one of the preceding claims, characterized in that the branch line (14) has a main line-side end section (18) for connecting the branch line (14) to the main line (15) and a sensor-side end section (19) for connecting the Having a branch line (14) to the sensor unit (11), an HME filter (16) being arranged on and / or in the end section (18) on the main line side.

4. Sensor arrangement (10) according to one of the preceding claims, characterized in that the branch line (14) has a main line-side end section (18) for connecting the branch line (14) to the main line (15) and a sensor-side end section (19) for connecting the Branch line (14) to the sensor unit (11), the sensor arrangement (10) having a first HME filter (16) on and / or in the main line-side end section (18) and a second HME filter (17) on and / or in having sensor-side end section (19).

5. Sensor arrangement (10) according to claim 4, characterized in that the first HME filter (16) in the main line-side end section (18) of the branch line (14) is designed in the form of a hose insert, the branch line (14), in the flow direction of the When measured gas is viewed through the branch line (14), it has a larger inside diameter at fleas of the HME filter (16) than in an area downstream of the FIME filter (16).

6. Sensor arrangement (10) according to claim 5, characterized in that the inner diameter of the branch line (14) at fleas of the first FIME filter (16) has a value in a range between 2 mm and 4 mm and the inner diameter of the branch line (14 ) downstream of the first FIME filter (16) has a value in a range between 0.5 mm and 2 mm.

7. Sensor arrangement (10) according to one of the preceding claims, characterized in that the at least one FHME filter (16) in the main line-side end section (18) of the branch line (14) is designed in the form of a hose insert, the branch line (14), viewed in the direction of flow of the measurement gas through the branch line (14), has a larger inner diameter in an area upstream of the at least one FIME filter (16) than downstream of the at least one FIME filter (16).

8. Sensor arrangement (10) according to claim 7, characterized in that the inner diameter of the branch line (14) upstream of the at least one FIME filter (16) has a value in a range between 1.5 mm and 4 mm and the inner diameter of the branch line (14) downstream of the at least one FIME filter (16) has a value in a range between 0.5 mm and 2 mm.

9. Sensor arrangement (10) according to one of the preceding claims, characterized in that the at least one HME filter (16) has a length in a range between 8 mm and 20 mm and a width in a range between 2 mm and 6 mm.

10. Sensor arrangement (10) according to one of the preceding claims, characterized in that the branch line (14) has a hose line with a length in a range between 80 cm and 150 cm.

11. Sensor arrangement (10) according to one of the preceding claims, characterized in that the branch line (14) has a hose line made of silicone or at least predominantly made of silicone.

12. Sensor arrangement (10) according to one of the preceding claims, characterized in that the branch line (14) has a hose line with a PVC coating on an outer peripheral surface of the hose line.

13. Sensor arrangement (10) according to one of the preceding claims, characterized in that the branch line (14) has a Luer lock connection for establishing a fluid connection with the main line (15).

14. Sensor arrangement (10) according to one of the preceding claims, characterized in that the at least one HME filter (16, 17) has a microporous plastic foam.

15. Medical device (12) for ventilating a person (13), comprising a main line (15) for conducting inspiratory gas and for conducting expiratory gas, and a sensor arrangement (10) according to one of the preceding claims, wherein the branch line (14) for branching a measurement gas from the main line (15) and the at least one HME filter (16, 17) is configured to filter the branched measurement gas.

16. Medical device (12) according to claim 15, characterized in that the main line (15) has an inspiratory gas line section (21) for guiding the inspiratory gas and a total gas line section (22) for guiding the inspiratory gas and the expiratory gas, the branch line (14) for The measurement gas is branched off from the total gas line section (22).

17. Medical device (12) according to claim 16, characterized in that the at least one HME filter (16) is located within the overall gas line section (22).

18. Medical device (12) according to one of claims 16 to 17, characterized in that at least part of the branch line (14) extends within the main line (15) from the total gas line section (22) into the inspiration gas line section (21).

19. Medical device (12) according to one of claims 16 to 18, characterized in that an expiration valve (25) for letting out expiratory gas from the medical device (12) into the vicinity of the medical device (12) is configured in the overall gas line section (22), wherein the at least one HME filter (16) is configured in the expiratory valve (25).

20. Medical device (12) according to claim 19, characterized in that the branch line (14) for branching off the measurement gas from the main line (15) is connected to the expiration valve (25).

21. Medical device (12) according to one of claims 15 to 20, characterized in that the medical device (12) is designed as a ventilator.

22. Exhalation valve (25) for a medical device (12) according to one of the

Claims 15 to 21 for letting out expiratory gas from the medical device (12) into the surroundings of the medical device (12), having an HME filter (16, 17) integrated into the expiration valve (25) for filtering one from the medical device (12) the exhalation valve (25) diverted sample gas.

23. Exhalation valve (25) according to claim 22, characterized by a valve connection (26) for connecting a branch line (14) for branching off the measurement gas from a main line (15) of the medical device (12) through the HME filter (16).

24. Exhalation valve (25) according to one of claims 22 to 23, characterized in that the integrated HME filter (16, 17) has a microporous plastic foam.

25. A method for determining a carbon dioxide concentration in a measurement gas using a sensor arrangement (10) according to one of claims 1 to 14, a medical device (12) according to one of claims 15 to 21 and / or an expiration valve (25) according to one of claims 22 to 24, wherein the carbon dioxide concentration is determined by measuring the thermal conductivity of the expiratory gas.

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