FILTER ARRANGEMENT AND PROCESS FOR FILTERING A GAS FROM A GAS MIXTURE

Abstract

An arrangement and a process filter out at least one gas from a gas mixture. A filter unit (4) of the filter arrangement comprises an inlet and an outlet and is adapted to filter the gas out of the gas mixture while the gas mixture flows through the filter unit (4). The filter unit (4) takes up the gas and heats up in the process. A filter temperature sensor (46, 46.2) of the filter arrangement is adapted to measure at least once an indicator of the temperature in a first measuring area (MP, MP.2) inside the filter unit (4). Depending on the measured temperature, a message is generated and output in a form perceptible by a human being. This message includes information about the current state of the filter unit (4).

Claims

1. A filter arrangement for filtering out a gas from a gas mixture, the filter arrangement comprising: a filter unit comprising an inlet and an outlet, wherein the filter unit is configured to filter gas out of the gas mixture with the gas mixture flowing through the filter unit, the filter unit is configured to take up the gas, wherein the filter unit heats up as a consequence of taking up the gas, wherein the filter arrangement is configured such that the gas mixture flows through the inlet into the filter unit, flows at least once through the filter unit and flows through the outlet out of the filter unit; a sensor arrangement comprising a filter temperature sensor configured to measure at least once an indicator of a temperature in a measuring area inside the filter unit, wherein the filter arrangement is configured: to generate a message depending on the measured temperature; and to output the message or cause that message to be output in a form that is perceptible by a human being, and wherein the message comprises information about a current state of the filter unit.

2. A filter arrangement according to claim 1, further comprising a signal-processing evaluation unit configured: to decide, using a signal from the filter temperature sensor, whether a predetermined criterion is met, wherein the criterion depends on at least one value of the temperature in the first measuring area; and to generate the message with the information about the state of the filter unit if the criterion is met.

3. A filter arrangement according to claim 2, wherein: the filter temperature sensor is configured to measure the indicator of temperature in the measuring area at a plurality of successive sampling times; the signal-processing evaluation unit is configured to determine a time course of the temperature in the measuring area using a signal from the first filter temperature sensor, and the criterion for which the message is generated when the criterion is met depends on the time course of the temperature in the measuring area.

4. A filter arrangement according to claim 2, wherein: the filter temperature sensor is a first filter temperature sensor and the measuring area is a first measuring area; the sensor arrangement further comprises a second filter temperature sensor configured to measure at least once an indicator of a temperature in a second measuring area inside the filter unit; the first measuring area, with respect to a direction in which the gas mixture flows through the filter unit, is arranged downstream of the second measuring area; the signal-processing evaluation unit is configured to use a signal from the first filter temperature sensor and a signal from the second filter temperature sensor to determine a spatial course at a point in time of the temperature along a distance from the inlet to the outlet of the filter unit; and the criterion for which the message is generated depends on the detected spatial course of the temperature along the distance.

5. A filter arrangement according to claim 2, wherein the sensor arrangement comprises an ambient temperature sensor configured to measure an indicator of a temperature in the environment of the filter assembly as a measured ambient temperature or is adapted to receive a signal containing a measured ambient temperature from an ambient temperature sensor, wherein the evaluation unit is configured to calculate a difference between a filter temperature measured by the filter temperature sensor and the measured ambient temperature, wherein the criterion depends on the difference between the measured filter temperature and the measured ambient temperature.

6. A filter arrangement according to claim 1, wherein: the filter unit comprises a filter mount and a filter; the filter is inserted or insertable into the filter mount; the filter arrangement is configured such that with the filter inserted into the filter mount, the gas mixture flows into the filter mount, through the inlet, through the filter, out of the outlet and out of the filter mount; and the filter temperature sensor is inserted into a wall of the filter mount and is spaced from the inserted filter.

7. A filter arrangement according to claim 6, wherein the filter temperature sensor comprises an infrared sensor configured to measure an indicator of an amount or of an intensity of infrared radiation emitted by the filter, as the indicator of temperature.

8. A filter arrangement according to claim 7, wherein the infrared sensor comprises one or more of: a pyroelectric sensor; a thermal imaging camera; several infrared thermocouples; and several thermo-piles.

9. A filter arrangement according to claim 6, wherein: the filter temperature sensor comprises a thermal probe and a transducer; the thermal probe establishes thermal contact between the inserted filter and the transducer; and the transducer is configured to generate a signal dependent on a temperature of the thermal probe.

10. A filter arrangement according to claim 6, wherein the filter temperature sensor comprises: a sensing element inside the filter, wherein the sensing element is configured to generate a signal depending on the temperature in the measuring area; and a receiver in the wall of the filter mount, wherein with the filter inserted into the filter mount, a data link is established between the sensing element and the receiver.

11. A filter arrangement according to claim 1, wherein: the filter temperature sensor comprises a chemical indicator element being in thermal contact with the filter and having dependent on the temperature of the filter in the measuring area a first optically perceptible state or a second optically perceptible state; and the second optically perceptible state is different from the first optically perceptible state.

12. A filter arrangement according to claim 11, wherein the filter unit comprises a filter mount and a filter; the filter is inserted or insertable into the filter mount; the filter arrangement is configured such that with the filter inserted into the filter mount, the gas mixture flows into the filter mount, through the inlet, through the filter, out of the outlet and out of the filter mount; wherein the chemical indicator is mounted onto the filter; and wherein a viewing window is inserted into the filter mount such that the chemical indicator is visible from outside through the viewing window with the filter being inserted into the filter mount.

13. A filter arrangement according to claim 1, wherein the filter unit is configured to filter out anesthetic from the gas mixture.

14. A ventilation system for ventilation of a patient, the ventilation system comprising: a ventilator; a fluid guide unit comprising an inspiration portion, the fluid guide unit being configured to at least temporarily establish a fluid connection between the ventilator and a patient-side coupling unit, wherein the patient-side coupling unit is connectable to a patient, wherein the ventilator is configured to deliver a gas mixture comprising oxygen through the inspiration portion to the patient-side coupling unit; and a filter arrangement at least temporarily in fluid communication with the fluid guide unit and configured to filter out gas from a gas mixture, the filter arrangement comprising: a filter unit comprising an inlet and an outlet, wherein the filter unit is configured to take up the gas, wherein the filter unit heats up as a consequence of taking up the gas, wherein the filter arrangement is configured such that the gas mixture flows through the inlet into the filter unit, flows at least once through the filter unit and flows through the outlet out of the filter unit; a sensor arrangement comprising a filter temperature sensor configured to measure at least once an indicator of temperature in a measuring area inside the filter unit, wherein the filter arrangement is configured: to generate a message depending on the measured temperature; and to output the message or to cause that message to be output in a form that is perceptible by a human being, and wherein the message comprises information about a current state of the filter unit.

15. A ventilation system according to claim 14, wherein: the ventilator is configured as an anesthesia machine; and the fluid guide unit comprises an expiration portion and is configured to establish a ventilation circuit between the anesthesia machine and the patient-side coupling unit, the anesthesia machine is configured to convey a gas mixture comprising oxygen and at least one anesthetic to the patient-side coupling unit through the inspiration portion, and wherein the filter arrangement is at least temporarily in a fluid connection with the expiration portion and is adapted to filter out the anesthetic from the gas mixture which is passed through the filter unit of the filter arrangement.

16. A process for filtering a gas from a gas mixture using a filter arrangement which comprises a filter unit and a sensor arrangement with a filter temperature sensor, wherein the filter unit comprises an inlet and an outlet, the process comprising the steps of: providing a gas mixture such that the gas mixture flows through the inlet into the filter unit with the gas mixture flowing through the filter unit at least once and flows through the outlet out of the filter unit; filtering gas out of the gas mixture with the filter unit while the gas mixture flows through the filter unit; taking up the filtered-out gas with the filter unit heating up as a result of taking up of the gas; with the filter temperature sensor, measuring an indicator of a temperature in a measuring area inside the filter unit; generating a message depending on the measured temperature; and outputting the generated message or causing the generated message to be output in a form that can be perceived by a human being, said message comprising information about a current state of the filter unit.

17. A process according to claim 16, wherein the process further comprises: deciding whether a predetermined criterion is fulfilled, the criterion depending on the temperature in the first measuring area; and generating and outputting the message with the information about the state of the filter unit when the criterion is fulfilled.

18. A process according to claim 16, wherein the process comprises the further steps of: with the filter temperature sensor, measuring the indicator of temperature in a measurement region inside the filter unit at a plurality of successive sampling times; determining a time course of the measured temperature in the first measuring area; and providing the criterion for generating the message so that the criterion depends on the time course of the temperature in the first measuring area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0081] In the drawings:

[0082] FIG. 1 is a schematic view showing a ventilation system with an anesthesia machine and a filter unit;

[0083] FIG. 2 is a schematic side view showing an exemplary filter unit in which the inlet and the outlet of the filter are arranged near the bottom;

[0084] FIG. 3 is a schematic plan view showing another exemplary filter unit with a forced guidance of the excess gas;

[0085] FIG. 4 is a schematic view with graph showing an example of the spatial course of the temperature in the filter unit, i.e. the dependence of the temperature on the location;

[0086] FIG. 5 is a schematic sectional view showing a first embodiment of a filter temperature sensor comprising a sensing element within the filter element;

[0087] FIG. 6 is a schematic sectional view showing a second embodiment of a filter temperature sensor having a thermal contact element on the outer surface of the filter cartridge;

[0088] FIG. 7 is a schematic sectional view showing a third embodiment of a filter temperature sensor comprising a non-contact infrared sensor; and

[0089] FIG. 8 is a schematic sectional view showing a fourth embodiment of a filter temperature sensor having a plurality of chemical indicator elements on the filter cartridge.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0090] Referring to the drawings, in an embodiment, the invention is used to artificially ventilate a patient P while delivering at least one anesthetic agent (anesthetic) to the patient. The patient P is in an at least partially enclosed space while being artificially ventilated, for example in a room of a hospital or on board a vehicle or aircraft.

[0091] FIG. 1 schematically shows a medical system 100 for anesthetizing or sedating and artificially ventilating the patient P. A schematically shown patient-side coupling unit 39, for example a breathing mask or a tube or a catheter, is positioned on or in the body of the patient P. The patient P is supplied with a gas mixture via an inspiration gas line 27, which flows to the patient-side coupling unit 39. This gas mixture includes oxygen and is mixed with anesthetic to keep the patient P sedated or anesthetized. The percentage of oxygen in the gas mixture may be higher than the percentage of oxygen in the breathing air. The breathable air exhaled by the patient P contains carbon dioxide (CO2) and may also contain traces of the anesthetic administered. The exhaled air is discharged via an expiratory gas line 28, suctioned off in the exemplary embodiment. Both gas lines 27, 28 are connected to a medical device in the form of an anesthesia machine 1 which maintains a flow of gas in a ventilation circuit to supply the patient P with respiratory air and anesthetic and to aspirate and receive exhaled air. This ventilation circuit includes gas lines 27 and 28 and patient-side coupling unit 39 and is passed through the anesthesia machine 1. The two gas lines 27, 28 together form the fluid guide unit of the embodiment, which at least temporarily provides fluid communication between the anesthesia machine 1 and the patient-side coupling unit 39. The gas line 27 serves as the inspiration portion, the gas line 28 as the expiration portion.

[0092] The anesthesia machine 1 is supplied with pressurized breathing air, pure oxygen (02) and nitrous oxide (N2O) from a hospital infrastructure and generates the gas mixture. In an embodiment example, the anesthesia machine 1 comprises the following components: [0093] a gas mixer 29 which generates a mixture from at least two of the three supplied gases breathing air, O2 and N20, which mixture is used as a carrier gas for anesthetics, wherein the gas mixer 29 can be constructed as described in DE 10 2008 057 180 B3 (corresponding to US8356596 (B2), which is incorporated by reference), [0094] a fluid delivery unit 5, for example a blower or a pump or a piston-cylinder unit, wherein the fluid delivery unit 5 moves a gas mixture through the ventilation circuit and thereby maintains the gas flow in the ventilation circuit, [0095] an anesthetic vaporizer 2 comprising a tank for liquid anesthetic and a vaporizer unit, and [0096] a preferably device-internal filter unit 3 with a lime filter, the filter unit 3 filtering CO2 out of the respiratory air exhaled by the patient P and discharged via the expiratory gas line 28.

[0097] The anesthetic vaporizer 2 adds anesthetic from the anesthetic tank to the carrier gas. For example, the vaporizer unit of the anesthetic vaporizer 2 vaporizes the anesthetic in the tank and/or injects it into the carrier gas.

[0098] The anesthesia machine1 supplies gas to the ventilation circuit. The filter unit 3 withdraws gas, in particular CO2, from the ventilation circuit. On balance, more gas is thus supplied to the ventilation circuit than is withdrawn. It is therefore necessary to remove excess gas from the ventilation circuit. This excess gas is hereinafter referred to as “excess gas” and functions as the gas mixture. This excess gas usually contains traces of exhaled anesthetic. The anesthetic is to be filtered out of this gas mixture. In the embodiment example, the anesthetic acts as a gas to be filtered out.

[0099] The excess gas is branched off from the ventilation circuit at a branching point 24, by means of a supply line 6 and a subsequent, i.e. downstream, discharge line 8. The branching is effected in two different ways: On the one hand, the fluid conveying unit 5 ejects gas and conveys the ejected excess gas into the feed line 6, wherein the volume flow of the ejected excess gas varies with time and the idealized time course of the volume flow has, for example, the shape of a half-sine curve. On the other hand, the ejected excess gas is passed through the discharge line 8 and, in one embodiment, is sucked in.

[0100] In the embodiment, the discharge conduit 8 leads into a stationary fluid receptacle 7 that is embedded in a wall W. The fluid receptacle 7 is preferably part of a stationary infrastructure of a hospital, with the infrastructure receiving gases emitted by various medical devices and passing them on. An intake pump 10 draws gas into the discharge line 8 and conveys it into the fluid receptacle 7. The intake pump 10 may be located in front of or behind the wall W.

[0101] An optional volume flow sensor 9 measures the volume flow, i.e. the volume per unit time, flowing through the discharge line 8. For example, the volume flow sensor 9 measures a pressure difference between two measuring points in the discharge line 8, one measuring point being arranged downstream of the other measuring point. In one embodiment, the suction pump 10 is controlled in response to a signal from the volume flow sensor 9 with the control objective that the actual volume flow through the discharge line 8 is equal to a desired predetermined volume flow. Thus, the actual volume flow in the discharge line 8 is automatically controlled.

[0102] The feed line 6 directs the excess gas from the anesthesia machine1 to a filter unit 4, which will be described further below and is part of the filter arrangement according to the invention. The excess gas flows at least once through the filter unit 4, optionally several times. Here, the filter unit 4 filters out the anesthetic agent or at least one, preferably each anesthetic agent (the anesthetic) from the excess gas flowing therethrough. The excess gas, cleaned of anesthetic, flows into the discharge line 8.

[0103] An ambient temperature sensor 21 measures an indicator of the ambient temperature in the vicinity of the filter unit 4.

[0104] FIG. 2 shows an exemplary embodiment of the filter unit 4. The filter unit 4 comprises a filter element 11 for anesthetics and a cartridge 20 in the form of a cylinder or a truncated cone, the cartridge 20 surrounding the filter element 11. Preferably, the cartridge 20 completely surrounds the filter element 11 in a gas-tight manner except for openings described below. In a preferred embodiment, the filter element 11 comprises a bulk material surrounded and held on all sides by the cartridge 20. Preferably, the bulk material comprises activated carbon. The cartridge 20 prevents bulk material from escaping. It is also possible that the filter element 11 comprises zeolites, organometallic filters and/or silica instead of or in addition to the activated carbon. In the embodiment example, a circumferential protrusion 12 is mounted on the top of the cartridge 20. The filter element 11, the cartridge 20 and the optional protrusion 12 together form the filter of the embodiment.

[0105] Furthermore, the filter unit 4 comprises a filter mount in the form of a pot 13, the pot 13 being rotationally symmetrical to a central axis, this central axis being arranged vertically in use and lying in the drawing planes of FIG. 2 and FIG. 5 to FIG. 8. The pot 13 comprises a preferably circular base perpendicular to the central axis and a tubular peripheral surface surrounding the central axis. The pot may also have the shape of a cylinder or a truncated cone. Two openings 22.1 and 22.2 are recessed in the mantle surface of the pot 13, and in the illustrated embodiment near the upper edge of the mantle surface.

[0106] A circumferential seal 41 is placed on the upper edge of the circumferential surface of the pot 13. An approximately cylindrical filter 11, 20, 12 can be inserted into this pot 13 from above and removed from the pot 13 again. The circumferential projection 12 is supported on the seal 41 at the upper edge of the circumferential surface. Thanks to the protrusion 12 and the seal 41, the risk of a relevant amount of a gas mixture escaping from the pot 13 into the environment is low. Optionally, a lid not shown can be placed on the pot 13 from above and removed again.

[0107] A tubular gap 19 appears between the outer surface of the pot 13 and the cartridge 20, cf. FIG. 3. A pot supply line 16 in the pot 13 is connected in a fluid-tight manner to the supply line 6, conducts excess gas supplied from the opening 22.1 to the bottom of the pot 13 and ends in an outlet opening 14. A pot discharge line 32 in the pot 13 is fluid-tightly connected to the discharge line 8, conducts excess gas exiting the filter 11, 20, 12 towards the discharge line 8, starts in an inlet opening 35 or at the level of the bottom of the cartridge 20 and leads to the opening 22.2.

[0108] In one embodiment, when the cartridge 20 is correctly inserted into the pot 13, and in particular in the correct rotational position, the outlet opening 14 of the pot feed line 16 overlaps with an inlet opening 25 in the cartridge 20. The inlet opening 35 of the pot discharge line 32 overlaps with an outlet opening 34 in the cartridge 20. The two openings 14, 35 are located near the lateral surface of the cartridge 20 and near the bottom of the pot 13, and the two openings 25, 34 are located in the lateral surface and near the bottom of the cartridge 20.

[0109] In the example shown, the excess gas is introduced into the filter 11, 20, 12 from below through the inlet opening 25. The arrows in the filter element 11 illustrate by way of example the directions in which the excess gas flows through the filter element 11, cf. FIG. 2.

[0110] It is also possible that the outlet opening 14 of the pot feed line 16 is located near the lid of the pot 13 and/or the inlet opening 25 in the cartridge 20 is located near the circumferential protrusion 12.

[0111] FIG. 3 shows an embodiment in which the excess gas is forced as it flows through the filter unit 11, and therefore flows twice through the filter unit 11. The drawing plane of FIG. 3 is horizontal and perpendicular to the drawing plane of FIG. 2, and the coincident central axis of the pot 13 and the filter 11, 20, 12 is perpendicular to the drawing plane of FIG. 3. It can be seen that the circular gap 19 occurs between the filter 11, 20, 12 and the pot 13.

[0112] According to this embodiment, a wall 38 is inserted into the interior of the filter 11, 20, 12, which is impermeable to fluid. This wall 38 extends parallel to the central axis of the filter 11, which is perpendicular to the drawing plane of FIG. 3, preferably at a distance from the central axis, and is preferably in the form of a flat surface or a surface curved along a vertical axis. The wall 38 divides the cartridge 20 and thus the filter element 11 in the cartridge 20 into an ascent region Au and a descent region Ab for the gas mixture flowing therethrough, cf. FIG. 3. Viewed in a viewing direction parallel to the central axis of the filter 11, 20, 12, both the ascent region Au and the descent region Ab each have a cross-section in the form of a segment of a circle. The ascending region Au is in fluid communication with the inlet port 25.

[0113] In all embodiments, the filter element 11 filters out anesthetic from the excess gas. The excess gas flows through the supply line 6 into the pot supply line 16 and through the pot supply line 16 and enters the filter element 11 through the inlet port 25 in the cartridge 20. Ideally, all of the anesthetic is removed from the excess gas in the filter element 11. The excess gas then exits the filter element 11 through the outlet opening 34, enters the pot discharge line 32 through the inlet opening 35, and flows through the pot discharge line 32 into the discharge line 8.

[0114] The filter element 11 absorbs the anesthetic (the anesthetic comprising one or more anesthetic agents). In many cases, the filter material binds molecules of the anesthetic. This process is exothermic for any filter material used for the filter element 11 of the embodiment. Thus, heat is released when the anesthetic is absorbed. The invention takes advantage of this fact. If activated carbon is used as the filter material, the filter material will in many cases heat up by at least 4° C. at a usual concentration of the anesthetic until the filter element 11 is completely clogged and no further anesthetic can be absorbed. This temperature increase of at least 4° C. can be reliably detected in many cases.

[0115] FIG. 4 shows an example of how the temperature inside the filter element 11 at a point in time depends on location, i.e. a spatial pattern. In this schematic diagram, the excess gas flows into the filter element 11 from above through the inlet opening 25, flows through the filter element 11, and exits the filter element 11 through the outlet opening 34, the outlet opening 34 being located at the bottom of the filter element 11. Note: Because the excess gas contains anesthetic, it is generally heavier than air and sinks to the bottom.

[0116] The diagram to the left of filter unit 4 shows on the x-axis (from top to bottom) the location x along the direction of flow of the excess gas. L denotes the length of the filter element 11 in the direction of flow, i.e. in FIG. 4 the vertical extent. The location x = 0 stands for the inlet opening 25, the location x = L for the outlet opening 34 of the filter element 11. On the y-axis the location-dependent temperature Temp at a certain point in time is plotted. A maximum at x.sub.max can be seen. The filter element 11 is currently taking in anesthetics in a range around this maximum x.sub.max. The area from x = 0 to behind x = x.sub.max has already largely become clogged with anesthetic.

[0117] The temperature peak x.sub.max and thus the absorption range in which the filter element 11 currently absorbs anesthetic migrates over time from the inlet opening 25 through the filter element 11 towards the outlet opening 34. A first measuring position MP, at which the current temperature inside the filter element 11 is measured according to the invention, is therefore preferably located in the vicinity of the outlet opening 34. By measuring the temperature at this first measuring position MP, it is possible to detect the event that the temperature peak x.sub.max has almost reached the outlet opening 34 and the filter element 11 can only absorb a small amount of further anesthetic.

[0118] It is possible that additionally the respective current temperature is measured at further measuring positions MP.2, MP.3, ..., MP.n, wherein these further measuring positions MP.2, MP.3, ..., MP.n are located between the inlet opening 25 and the first measuring position MP. Generally, at a point in time, the respective actual temperature in the filter element 11 differs depending on the measuring position MP, MP.2, ... at which this temperature is measured. The temperature peak x.sub.max moves over time from the inlet opening 25 to the outlet opening 34, passing successively through the measuring positions MP.n, ..., MP.2, MP. From the temporal course, i.e. the migration, of the temperature peak x.sub.max it is possible in many cases to predict when the filter element 11 will be used up and will therefore have to be replaced.

[0119] A signal-processing evaluation unit 26 receives a signal from at least one filter temperature sensor described below and preferably a signal from the ambient temperature sensor 21, cf. FIG. 2 and FIG. 5 to FIG. 7. The measured ambient temperature acts as a reference value and can influence the temperature of the filter element 11. The or each filter temperature sensor respectively measures an indicator of the temperature inside the filter element 11 at a measuring position MP, MP.2, ..., MP.n. The evaluation unit 26 respectively receives a signal from the or each filter temperature sensor and from the ambient temperature sensor 21 and determines a current state of the filter element 11 depending on the or each measured temperature inside the filter element 11 and depending on the measured ambient temperature.

[0120] The evaluation unit 26 is able to control a status display 17. If the filter element 11 has absorbed so much anesthetic that the filter 11, 20, 12 needs to be replaced, a message, for example an alarm, is output on the status display 17 in a form that can be perceived by a human being. This message comprises information about the current state of the filter element 11. The alarm may also indicate a period of time after which the filter 11, 20, 12 needs to be replaced.

[0121] Four possible embodiments of a filter temperature sensor are described below with reference to FIG. 5 to FIG. 8. It is possible that the filter arrangement comprises several filter temperature sensors, whereby several of these configurations are used, which leads to redundancy and in some cases increases the reliability compared to a single measuring principle. It is also possible that the filter arrangement comprises multiple filter temperature sensors configured in the same way, configured to use the same measurement principle.

[0122] In the embodiment shown in FIG. 5, a sensing element 15 measures the temperature inside the filter element 11 and there at a first measuring position MP near the outlet opening 34 in the cartridge 20. This sensing element 15 is arranged at the first measuring position MP inside the filter element 11. When the excess gas has reached this first measuring position MP, it has already covered most of its path through the filter element 11. The sensing element 15 is in a data connection with a filter-side contact element 44 inside the pot 13 via a signal line 18, which bridges the gap 19 between the filter 11, 12, 20 and the pot 13. The signal line 18 is arranged inside the filter element 11. A pot side contact element 45 is recessed into the shell surface of the pot 13. The filter-side contact element 44 establishes a data connection between the sensing element 15 and the pot-side contact element 45, and is preferably also mechanically connected to the pot-side contact element 45.

[0123] In one embodiment, the cartridge 20 includes a filter-side contact surface 47 that is in electrical contact with the signal line 18 on the inside and in electrical contact with the filter-side contact element 44 on the outside. This filter-side contact surface 47 may comprise a ring or ring segment, so that electrical contact between the signal line 18 and the contact element 44 is established at many or even all possible rotational positions of the filter 11, 20, 12 relative to the pot 13.

[0124] The elements 18, 47 and 44 form a data connection between the sensing element 15 and the contact element 45. A signal from the sensing element 15 is transmitted via this data connection to the contact element 45 and from there further to the evaluation unit 26. In addition, the evaluation unit 26 receives measured values from the ambient temperature sensor 21. The evaluation unit 26 compares the signal from the sensing element 15 with the measured ambient temperature and decides whether the filter unit 11 can receive further anesthetic.

[0125] It is possible that a further measurement sensor (not shown) is arranged at at least one further measurement position MP.2, ..., MP.n. The measured values of the or each further measuring sensor are also transmitted to the evaluation unit 26 via a signal line and via contact elements.

[0126] FIG. 6 and FIG. 7 show a preferred embodiment in which it is not necessary to provide the filter element 11 with a sensing element 15 and a signal line 18. Rather, the filter temperature sensor or each filter temperature sensor is located entirely outside of the filter 11, 20, 12, allowing the same filter temperature sensor to be reused sequentially to monitor multiple filters 11, 20, 12. When a spent filter 11, 20, 12 is reprocessed or disposed of, there is no need to give special treatment to a sensing element 15 and a signal line 18.

[0127] In the embodiment according to FIG. 6, a filter-side contact element 49 is arranged inside the pot 13 and bridges the gap 19 between the cartridge 20 and the pot 13. The filter-side contact element 49 is in thermal contact with the outer surface of the cartridge 20 and is preferably positioned as close as possible to the measuring position MP. Just as in the embodiment according to FIG. 5, an annular filter-side contact surface 47 may be embedded in the cartridge 20 and as close as possible to the first measuring position MP. However, this filter-side contact surface 47 serves to establish a thermal contact. The elements 47 and 49 together act as a sensing element.

[0128] The filter side contact element 49 conducts heat from the filter element 11 to a pot side sensing element 48. The pot-side sensing element 48 acts as a transducer and generates an electrical signal depending on the heat transmitted by the filter-side contact element 49. Examples of implementations of such a sensing element 48 are a thermocouple, a PTC sensor or an NTC sensor.

[0129] It is possible that at least one further measuring sensor is positioned in the vicinity of a respective further measuring position MP.2, ..., MP.n. In the example of FIG. 6, a second pot-side sensing element 48.2 is additionally embedded in the outer surface of the pot 13. A second filter-side contact element 49 bridges the gap 19 between the inserted filter 11, 20, 12 and the outer surface of the pot 13. A further filter-side contact surface 47.2 can be inserted into the cartridge 20, namely in the vicinity of the second measuring position MP.2.

[0130] FIG. 7 shows an embodiment in which a filter temperature sensor 46 measures an indicator of the temperature occurring at the measurement position MP inside the filter element 11 without contact. This embodiment is less dependent on the relative position of the inserted filter 11, 20, 12 relative to the pot 13 and also less dependent on the actual maximum diameter of the filter 11, 20, 12, which may vary from filter to filter. Preferably, the filter temperature sensor 46 is embedded in the lateral surface of the pot 13 and as close as possible to the measuring position MP. It is possible that at least one further filter temperature sensor 46.2 measures the temperature at a further measuring position MP.2, ..., MP.n without contact.

[0131] In a preferred embodiment, the filter temperature sensor 46 measures an indicator of the intensity and/or amount of infrared radiation emanating from the filter element 11 and passing through the cartridge 20 to the outside. The measured values of the filter temperature sensor 46, 46.2 are transmitted to the evaluation unit 26. Examples of a filter temperature sensor 46, 46.2 that measures an indicator of infrared radiation include a pyroelectric sensor, a CCD camera, a thermal imaging camera, multiple infrared thermocouples, or multiple thermopiles. It is also possible to use an infrared camera (thermal imaging camera) as the filter temperature sensor 46.

[0132] FIG. 8 shows an embodiment which does not require data transmission or a signal-processing evaluation unit 26, but which can be used in combination with such an evaluation unit 26. At least one chemical indicator element 50 is applied to the outer surface of the filter cartridge 20, preferably additionally at least one further chemical indicator element 50.2, ..., 50.n, particularly preferably a sequence of chemical indicator elements 50, 50.2, ..., 50.n, the sequence extending parallel to the central axis of the filter cartridge 20. Each chemical indicator element 50, 50.2, ..., 50.n is located near a respective measurement position MP, MP.2, ..., MP.n. Each chemical indicator element 50, 50.2, ..., 50.n has a first optically perceptible state when the temperature at a measurement position MP, MP.2, ..., MP.n is below a predetermined temperature threshold, and assumes a second optically perceptible state when the cartridge temperature exceeds said temperature threshold, said second state being optically different from said first state. Each sensing position MP, MP.2, ..., MP.n is located on the cartridge 20 and around or in proximity to the respective chemical indicator element. For example, the indicator element 50, 50.2, ..., 50.n changes color when the cartridge temperature exceeds the temperature threshold, thus shows a color change. The temperature threshold is selected such that the cartridge temperature is below this temperature threshold when the filter element 11 has not yet taken up any anesthetic at the respective measuring position MP, MP.2, ..., MP.n, and is above the temperature threshold when the filter element 11 cannot take up any more anesthetic at this measuring position MP, MP.2, ..., MP.n.

[0133] In the example of FIG. 8, the indicator element 50.n positioned furthest upstream already has the second state, this state being indicated by hatching, and the remaining indicator elements 50.3, 50.2, 50 still have the first state, which is indicated by white color.

[0134] A viewing window 37, shown schematically in FIG. 8, is provided in the peripheral surface of the pot 13. The indicator element or each indicator element 50, 50.2, ..., 50.n is visible from the outside through this viewing window 37. A user can visually detect the current state of the or each indicator element 50, 50.2, ..., 50.n behind the viewing window 37. It is also possible for a camera and an image evaluation unit (both not shown) to automatically determine whether an indicator element 50, 50.2, ..., 50.n is currently in the first state or in the second state. In one embodiment, the camera is recessed in the pot 13 and in another embodiment such that the viewing window 37 is located between the camera and the indicator elements 50, 50.2, ..., 50.n.

[0135] While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

TABLE-US-00001 List of reference characters: 1 Anesthesia machine, comprising an anesthetic vaporizer 2, a gas mixer 29, a CO2 lime filter 3, and a fluid delivery unit 5 2 Anesthetic vaporizer in anesthesia machine 1, includes anesthetic tank 49 3 Lime filter, which filters CO2 out of the exhaled air 4 Filter unit, which filters out anesthetics from the gas emitted by the anesthesia machine 1, comprises the filter element 11 in the cartridge 20, the cartridge 20 with the projection 12 and the pot 13, is connected to the supply line 6 and the discharge line 8 5 Fluid delivery unit of the anesthesia machine 1, which moves gas in the ventilation circuit, is for example in the form of a pump 6 Feed line, leads from anesthesia machine 1 to filter unit 4 7 stationary gas intake of the hospital infrastructure, received by the wall W, connected to the filter unit 4 via the discharge line 8 8 Discharge line, leading from the filter unit 4 to the gas intake 7 9 Volume flow sensor in the discharge line 8 10 suction pump on the discharge line 8 or in the fluid receiver 7, is in fluid communication with the discharge line 8 11 cylindrical activated carbon filter of the filter unit 4, acts as a filter element, is surrounded by the cartridge 20 12 circumferential projection of the cartridge 20, rests on the upper edge of the pot 13, preferably on the circumferential seal 41 13 Pot, into which the feed line 6 leads and from which the discharge line 8 leads, has the shape of a cylinder or truncated cone, acts as a filter mount 14 Outlet port of pot feed line 16, located at the lower end of pot feed line 16, overlaps with inlet port 25 when cartridge 20 is in place. 15 Sensing element, which measures the temperature of the filter element 11 at a first measuring position MP inside the filter element 11, is connected to the signal line 18 16 Pot supply line inside pot 13, forms a fluid-tight continuation of supply line 6, conducts gas from supply line 6 to the bottom of pot 13, ends in outlet opening 14 17 Status display for the filter element 11, is controlled by the evaluation unit 26, can output alarms 18 Signal line inside the filter element 11, leads from the sensing element 15 to the contact surface 47 19 Circumferential gap between the filter 11, 20, 12 and the inner wall of the pot 13 20 Cylindrical cartridge, surrounds the filter element 11, comprises the circumferential projection 12, carries in one embodiment the indicator elements 50, 50.2, ... 21 Ambient temperature sensor, measures an indicator of the temperature in the vicinity of the filter arrangement. 22.1 Opening in the circumferential surface of the pot 13, in which the supply line 6 ends 22.2 Opening in the jacket surface of the pot 13, in which the discharge line 8 begins 24 Branching point in the ventilation circuit at which excess gas is branched off from the ventilation circuit and in which the supply line 6 begins 25 Inlet opening near the bottom or cover of cartridge 20, overlaps with outlet opening 14 when filter 11, 20, 12 is in place. 26 Signal processing evaluation unit, which receives measured values from the or each filter temperature sensor and the ambient temperature sensor 21 and determines the current state of the filter element 11. 27 Inspiratory gas line to supply the patient P with breathing air 28 Expiratory gas line to aspirate breathing air exhaled by patient P 29 Gas mixer of the anesthesia machine 1, generates the carrier gas for the anesthetic 32 Pot discharge line inside pot 13, starts in inlet opening 35, directs gas from bottom of pot 13 into discharge line 8 34 Outlet opening near the bottom of cartridge 20, overlaps with inlet opening 35 when filter 11, 20, 12 is in place. 35 Inlet port of pot discharge line 32, is in fluid communication with outlet port 34 when filter 11, 20, 12 is in place. 37 Inspection window in the jacket surface of the pot 13 39 Patient-side coupling unit, positioned in or on the patient’s body P 41 Circumferential seal on the upper rim of the pot 13 44 Contact element on the filter side, which electrically bridges the gap 19 between the pot 13 and the filter 11, 20, 12 45 Pot-side contact element in the wall of the pot 13, comes into thermal contact with the filter-side contact element 44, generates measured values and forwards these to the evaluation unit 26 46 Non-contact filter temperature sensor, measures an indicator of the infrared radiation generated by the filter element 11 at the measuring position MP 46.2 Second non-contact filter temperature sensor, measures an indicator of the infrared radiation generated by the filter element 11 at the measuring position MP.2 47 Contact surface in the cartridge 20 and in the vicinity of the first measuring position MP, comes into contact with the signal line 18 (only in the embodiment with the sensing element 15) and the filter-side contact element 44, 49 47.2 Contact surface in the cartridge 20 and near the first measuring position MP, comes into contact with the filter-side contact element 49.2 48 Pot-side sensing element in the outer surface of the pot 13, is in thermal contact with the filter-side contact element 49, forwards measured values to the evaluation unit 26 48.2 Further sensing element on the pot side in the outer surface of the pot 13, is in thermal contact with the contact element 49.2 on the filter side, forwards measured values to the evaluation unit 26 49 Contact element inside the pot 13, comes into contact with the contact surface 47, thermally bridges the gap 19 between the pot 13 and the cartridge 20, 49.2 Further contact element inside the pot 13, comes into contact with the contact surface 47.2, thermally bridges the gap 19 between the pot 13 and the cartridge 20, 50 Chemical indicator element in the vicinity of the first measuring position MP, has a first state (low temperature) or a second state (high temperature) depending on the temperature of the filter element 11 50.2, ..., 50.n Further chemical indicator elements near the measuring positions MP.2, ..., MP.n 100 Medical system for artificial ventilation of patient P, comprising the anesthesia machine 1, the filter unit 4, the lines 6 and 8, the volume flow sensor 9 and the ambient temperature sensor 21, can be connected to the coupling unit 39 on the patient side and the gas intake 7 L Length of the filter element 11 MP First measuring position, at which the temperature in the filter element 11 is measured, is located close to the outlet opening 34 MP.2, ..., MP.n Further measuring positions inside the filter element 11, arranged upstream of the first measuring position MP P Patient connected to the anesthesia machine 1 via the patient-side coupling unit 39 and breathing at least one anesthetic (anesthetic) Temp Temperature inside the filter unit 11 W Wall receiving the stationary gas intake 7 Xmax Position of the temperature peak, i.e. position of the maximum temperature inside the filter element 11