Method and apparatus for identifying an anesthetic fluid container

Abstract: The invention relates to an apparatus and a method for identifying containers containing different anesthetic fluids. The containers include at least a fluid chamber (2) for an anesthetic fluid and for vaporizing the fluid therefrom into a gas chamber (3). A connecting element (8) is used for coupling the container with a conduit (6) extending to a patient for supplying an anesthetic to a patient. The containers containing anesthetic fluids are designated or labelled distinctly from each other by means of at least one magnetic-field producing element (12). The presence of this element is in turn detected by means of a magnetic-field detecting element (13) . The identification of a container containing an anesthetic fluid and, thus, an anesthetic fluid contained therein is effected by means of an identification element (15), which receives a signal from one or more magnetic-field detecting elements.

Description: The present invention relates to an apparatus for identifying an anesthetic fluid container, said apparatus comprising at least two anesthetic fluid containers, which containers include at least a fluid chamber for an anesthetic fluid and which containers contain anesthetic fluids different from each other in terms of the chemical structure thereof and a gas chamber for vapourizing the anesthetic originating from the fluid chamber and which gas chamber can be a part of the container or a chamber separated from the container and a connecting element for coupling the container with a conduit extending to a patient for supplying the anesthetic to a patient and which container is detachable from the connecting element and replaceable with another container possibly containing a different anesthetic fluid and a body member for installing the container therein in view of coupling it by means of the connecting element with a conduit extending to a patient. The invention relates also to a method for identifying an anesthetic fluid container. Furthermore, the invention relates to a method and apparatus for detecting a connection between an anesthetic container and a conduit supplying a gas to a patient. The vaporizers generally used in anesthesia, consisting of an anesthetic fluid container and a regulating element, are intended for just one given anesthetic. The user must have a separate vaporizer for each necessary anesthetic. A preferred and easier solution is to use a vaporizer, wherein the regulating element is separated from the anesthetic fluid container and, thus, only the fluid container must be replaced when the anesthetic fluid is to be replaced with another and the regulating element remains the same. The regulating element is used for controlling the flow of a fresh gas delivered to a patient, which flow may occur partially through a gas chamber, in which gas chamber an anesthetic originating from a fluid chamber is vapourized, and which gas chamber may be included in the anesthetic fluid container or separated therefrom, e.g. connected to the regulating element. The regulating element is also used for controlling the flow of an anesthetic vapourized from the anesthetic fluid container to a patient, i.e. for maintaining a desired and safe anesthetic concentration in relation to a fresh gas supplied to a patient. The fresh gas generally consists of a mixture of oxygen and nitrogen oxidule (N 2 O) or oxygen and air. The number of regulating elements required for identifying an anesthetic fluid container is just one, if each anesthetic fluid has its own container element. Another benefit gained by a separate container is that the filling thereof can be easily effected not in the operating room but elsewhere, in a ventilated facility more suitable for the purpose. Various anesthetic fluids have different vaporizing characteristics and, thus, a regulating element for the anesthetic concentration must operate in a different way on different anesthetic fluids. Thus, the regulating element must be informed that a container containing an anesthetic fluid is coupled therewith. This information can be transmitted by means of mechanical pins or electric contacts (GB 2177007). When an anesthetic fluid container or a vaporizer is coupled with an anesthesia work station, the work station must be capable of identifying the anesthetic fluid which is contained in this particular container and, preferably, for detecting the presence of said container. If this is done by using pins included in the container or by means of electric contacts, those are susceptible to mechanical failures and soiling. These may lead to error situations, such as the identification of a wrong anesthetic fluid. Due to differences between the vapor pressures of various anesthetic fluids, an incorrect identification can cause a life-threatening anesthetic concentration. The use of optical means, reflection sensors, opto-forks, electric contacts, connectors and other such methods also involves the hazard of mechanical failures and soiling. When using an optical method, the soiling of an identification spot included in the sensor or container results in the situation that the container is not detected or it is identified incorrectly. An object of this invention is to eliminate the above problems. Another object is to provide a simple and reliable apparatus and method for identifying an anesthetic fluid container. A further object is also to provide a method and apparatus for detecting a connection between an anesthetic fluid container and a conduit supplying a gas to a patient. Document EP-A-0338518 discloses an anesthetising apparatus and the associated method including the technical features of the preamble of claims 1 and 14 respectively. The characterizing features of an apparatus and method of the invention are set forth in the appended claims. The invention relates to an apparatus and method suitable for identifying an anesthetic fluid container. The apparatus consists of at least two anesthetic fluid containers, said containers containing anesthetic fluids that are different from each other in terms of the chemical structure. Thus, in the most preferred case, each anesthetic fluid intended for use is provided with its own container. The presently used anesthetic fluids include e.g. halotan, isofluran, enfluran, sevofluran, methoxy fluran and desfluran. Thus, if all these anesthetic fluids are to be used, six different containers are needed. The selected anesthetic fluid container, which thus includes at least a fluid chamber for an anesthetic fluid but preferably also a gas chamber for vaporizing the anesthetic originating from the fluid chamber, is coupled by means of a connecting element with a conduit extending to a patient for delivering the anesthetic to the patient along said conduit. However, the anesthetic must be mixed with a fresh gas upstream of the respiratory passages of a patient. The mixing can already be effected e.g. partly in the gas chamber, wherein the anesthetic vaporizes, by delivering through the gas chamber a fresh gas to be administered to a patient, and partly by mixing the mixture of fresh gas and anesthetic discharged from the gas chamber with a fresh gas that has bypassed the gas chamber and is also intended for the patient. Thus, the fresh gas flow usually originating from two different gas sources is preferably divided in two, i.e. a flow passing through and another flow passing by the gas chamber. Subsequently, prior to the administration thereof to a patient, said flows merge together again but contain additionally an anesthetic vaporized from an anesthetic fluid. According to another presently used mixing method, an anesthetic originating from an anesthetic fluid is vaporized in a gas chamber, wherefrom the vapor, through the action of a produced pressure, pursues along a conduit towards a patient but, upstream of the respiratory passages of the patient, this anesthetic-containing vapor is joined with a fresh gas to be supplied to the patient. Thus, no fresh gas flow is delivered into the gas chamber. According to the invention, an anesthetic fluid container, intended to be coupled by means of a connecting element with a conduit extending to a patient, must be identified before the anesthetic vaporized from this anesthetic fluid container reaches the respiratory passages of the patient. Thus, it is of a major importance to know that the patient receives exactly the correct anesthetic since, for example, different anesthetics are administered to patients at different concentrations, whereby a flow possibly discharging from the anesthetic container must either be reduced or increased in relation to a fresh gas flow. Another consideration is that the patient may be sensitive to a certain anesthetic, in which case the administration of a wrong anesthetic may cause a life danger. The identification of an anesthetic fluid container is effected by using magnetic phenomenon. This phenomenon for the identification of anesthetic fluid containers can be exploited in a variety of ways. It is essential that the containers containing different anesthetic fluids be designated differently from each other, whereby the incorrect identification of containers is not possible. The development of magnetic phenomenon requires a magnetic- field producing element, which is usually designated as a magnet, and the detection thereof requires a magnetic- field detecting element, such as e.g. a reed-relay or a Hall-sensor. The number of these elements is dependent on how such elements are to be used in the identification of anesthetic fluid containers. In principle, one magnetic- field producing element and one magnetic-field detecting element are sufficient for distinguishing various anesthetic fluid containers from each other. The identification could be effected by indicating a certain position in an anesthetic fluid container with a magnetic- field producing element, whereby in each container a certain position refers to a certain anesthetic fluid. In each container containing a different anesthetic fluid, the position would be at a different location. Accordingly, separated from the anesthetic fluid container would be a magnetic-field detecting element for running through the various predetermined positions in an anesthetic fluid container and detection of the existence of a magnetic field in a certain position would be an indication of a certain container containing some anesthetic fluid. An easier solution would be such that would include a number of magnetic-field detecting elements equal to the number of employed anesthetic fluid containers, whereby each possible position of a magnetic-field producing element would be provided with one magnetic-field detecting element. In practice, it would be preferable to include the magnetic- field detecting elements in some solid object, which is here designated as a body member, in such a manner that such elements would place themselves within the sphere of influence of a magnetic-field producing element positioned for each employed container containing a different anesthetic fluid as the anesthetic fluid container and the body member including the magnetic-field detecting elements are brought sufficiently close to each other and placed relative to each other in a position that enables the identification. According to a preferred exemplary solution, there are several magnetic-field detecting elements separated from a container and an equivalent number of positions included in the containers for placing the magnetic-field producing elements therein. The accepted magnetic combinations are selected in such a manner that the failure of one magnetic- field detecting element does not produce an incorrect identification. Thus, for example, when using four magnetic- field detecting elements, the selected acceptable combinations are those which include an even number of magnetic-field producing elements. If the magnetic-field detecting elements detect an odd number of magnets, it is clear that the question is about a faulty condition. Thus, the method can be applied also in self-diagnostics. When using four positions included in a container and two magnets per container, it is possible to encode six containers containing different anesthetic fluids if the detection only relates to the number and position of magnets included in the container. If necessary, more alternatives can be introduced by increasing the number of positions. It is also possible to exploit the polarity of magnets. In that case, magnets are placed in the positions at various attitudes. The magnet can have either its N-or P-pole towards a magnetic-field detecting element which, thus, must be capable of identifying the direction of a magnetic field. In the application of this method, even a single position included in a container can be used for identifying two containers containing different anesthetic fluids. When using several positions, the maximum number of identifiable containers is 2 to the power of N, wherein N is the number of positions. The magnet can also be mounted at an arbitrary attitude, the identification being effected by measuring the direction of a magnetic field, for example by means of two magnetic- field detecting elements, such as hall-sensors, mounted perpendicularly to each other. Thus, even a single magnet is capable of identifying a variety of alternatives. The limiting factor is principally the accuracy of measurement. The exploitation of magnetic-field producing and detecting elements does not require any visible or otherwise fault sensitive structures. The magnetic-field producing elements can be e.g. hidden in a fluid container, usually inside its shroud, and the magnetic-field detecting elements respectively outside the container, e.g. inside a body member that the container is to be coupled with as the supply of a vaporized anesthetic originating from the container is commenced to a patient. In order to produce an identification it is sufficient that such elements be brought as close to each other as necessary. The invention relates also to an apparatus and method for detecting a connection between an anesthetic fluid container and a conduit extending from this container to a patient or a conduit supplying a gas into this container. The coupling of an anesthetic fluid container with a gas- supplying conduit for delivering an anesthetic to a patient is effected by means of a connecting element. Thus, an object of the invention is to detect whether or not a fluid container is coupled on. This is also effected in part by using a magnetic-field producing element and a magnetic-field detecting element. According to the invention, an anesthetic fluid container is indicated by means of a magnetic-field producing element. Although there are a plurality of individual anesthetic fluid containers, possibly even containing different anesthetic fluids, a single magnetic-field producing element will be sufficient for indicating a connection, whereby said element must have such a position in the fluid container that a magnetic-field detecting element spaced apart from the container detects its presence or absence. Thus, the container connection can be detected either from the fact that a magnetic-field detecting element falls within the sphere of influence of a magnetic-field producing element or vice versa, whereby a magnetic-field detecting element lies no longer within the sphere of influence of a magnetic- field producing element. The invention will now be described in more detail with reference made to the accompanying patent drawing, in which fig. 1 shows a basic view of the identification of an anesthetic fluid container and an apparatus or a mechanism used therein for detecting the presence of an anesthetic fluid container. The illustrated apparatus comprises an anesthetic fluid container 1, including a fluid chamber 2 for an anesthetic fluid and a gas chamber 3 for vaporizing an anesthetic therein from the fluid chamber. According to a preferred solution shown in the figure, a gas, such as a fresh gas originating from one or more gas sources, not shown in the figure, is delivered through the gas chamber 3. From the gas source a fresh gas flows along a conduit 4 towards a patient, yet in such a manner that upstream of the patient some of the gas is deflected along another conduit 5 into the gas chamber 3, wherein the fresh gas is admixed with an anesthetic vaporized from the fluid chamber and wherefrom this gas mixture consisting of fresh gas and vapor is carried further along another conduit 6 back into the conduit 4 extending to the patient, wherein the mixture consisting of fresh gas and anesthetic is diluted as far as the anesthetic is concerned upon mixing with the fresh gas flowing along the conduit 4 before the gas mixture reaches the respiratory tracts of a patient. The conduit 5 supplying a gas into and the conduit 6 discharging a gas from the anesthetic fluid container are coupled with the anesthetic fluid container by means of connecting elements 7 and 8. The connecting element can be any useful solution for attaching a conduit either directly or indirectly to a container. Such a connection should be tightly sealed for eliminating gas leaks into the environment. The conduit 5 is further provided with a valve 9, preferably a shut-off valve, which can be closed and opened as necessary. The conduit 6 extending away from the gas chamber 3 is fitted with a valve 10, preferably a regulating valve, used for regulating the flow discharging from the gas chamber. In addition, the valve 10 is preferably of such a design that allows a flow in just one direction, i.e. from the gas chamber 3 towards a patient. The anesthetic fluid container includes one or, as shown in the figure, a number of positions 11, which position can be fitted with a magnetic-field producing element 12 required for identifying the container. The purpose is to place preferably one magnetic-field producing element in one position, but usually the arrangement is such that some of the positions remain vacant. In the illustrated solution, the number of positions 11 is five but just two of the stations are fitted with magnetic-field producing elements 12. Outside and spaced from the container 1 is located one or more magnetic-field detecting elements 13. In the figure, the magnetic-field detecting elements are preferably included in a body member 14, which body member is also fitted with the connecting elements 7 and 8. The magnetic-field detecting elements 13 are included in the body member in such a manner that, as the container is coupled by means of the connecting element 8 with the conduit 6 extending to a patient and, preferably at the same time, the container is coupled by means of the connecting element 7 with the conduit 5 supplying fresh gas into the container, the magnetic-field detecting elements fall at this time within the sphere of influence the magnetic-field producing elements possibly included in the container positions 11 but, according to a preferred embodiment, are not within the sphere of influence when the container is not properly connected to the conduit 6. Usually, the magnetic-field producing elements and the magnetic-field detecting elements are aligned with each other at the time of identification in such a manner that one magnetic-field detecting element corresponds to each operative position. The magnetic-field producing elements and the locations therefor can be selected for example in such a manner that, when using five positions 11 and two magnetic-field producing elements, positions a and b relate to halotan. In that case, each position a and b is provided with a magnetic-field producing element 12 while positions c, d and e are vacant. Accordingly, as the magnetic-field producing elements are included in positions a and c and positions b, d and e are vacant, the container is identified as an enfluran container. In accordance with the same principles, it is also possible to designate containers containing other anesthetic fluids as well. As shown in the figure, one or more of the magnetic-field detecting elements 13 are in communication with an identification element 15, capable of using information received from each element for identifying which anesthetic fluid is contained in a container that is coupled or is about to be coupled by means of the connecting element 8 with the conduit 6 extending to a patient. Prior to this, the identification element has been supplied with information about which position or positions is or are provided with one or more magnetic-field producing elements 12 corresponding to a container containing whichever anesthetic fluid. Respectively, in view of exploiting the orientation of a magnetic field, the identification element is provided with information about which direction indicates a container containing any given anesthetic fluid. If an identification performed by the identification element indicates that the container assigned to a patient contains a wrong anesthetic fluid, the identification element may produce e.g. an alarm to this effect or close the valve 10 included in the conduit extending from the gas chamber 3 towards a patient or, possibly, close the valve 9 included in the conduit 5 supplying fresh gas into the gas chamber 3. The replacement of a container with another container carrying either the same anesthetic fluid or some other anesthetic fluid is effected simply by removing the container from one or more connecting elements 8 and 7 said container has been coupled with and by fitting another container in position, the identification of a container being effected at the same time. The magnetic-field producing element 12 and the magnetic- field detecting element 11 can also be used for detecting a connection between the anesthetic fluid container and the conduit 6 or 5 supplying gas to a patient, i.e. whether or not the container is coupled with the conduit. In practice, the above-described apparatus applicable for the identification of a container can also be used for detecting a connection between a container and a conduit. One magnetic-field producing element, indicating a container, and one magnetic-field detecting element spaced from the container are sufficient. The fall of a magnetic- field detecting element within the sphere of influence of a magnetic-field producing element is an indication of a connection between a container and a conduit. Detection of the presence of a connection may also occur in reversed order, i.e. a magnetic-field detecting element is no longer within the sphere of influence of a magnetic-field producing element. A change in the direction of a magnetic field can also be used as an indication of the existence of a connection. Thus, the identification element 15 must be supplied with information about how to detect whether or not a container is coupled. For example, the identification element produce some type of signal indicating a connection to the operator. The positions included in the container can be produced e.g. by drilling holes in the container surface or by casting the container in a mould provided with preset locations for the positions. This is followed by placing one or more magnetic-field producing elements in one or more positions, whereafter it is further preferable to secure these elements in their positions and possibly to use e.g. a plastic coating for protecting at least those positions which are provided with magnetic-field producing elements. This way, the magnetic-field producing elements and the positions can be kept clean. Thus, it would also be desirable to prevent the unintentional detachment of these elements or the possible attachment thereof to an incorrect position. In practice, it is beneficial to combine the protection and attachment of magnetic-field producing elements e.g. by casting molten plastics in a position provided with a magnetic-field producing element, said plastics immobilizing the element as it solidifies. The same procedure can be followed when placing the magnetic-field detecting elements 13 outside a container in the body member 14. The invention is by no means limited to the above embodiments but various details of the invention can be modified within the scope of the claims. In most cases, the anesthetic fluid container includes both a fluid chamber, containing a vaporizable and liquid anesthetic, and a gas chamber for vaporizing some of the fluid. However, this is not absolutely necessary but, instead, the anesthetic fluid container may include just a fluid chamber, whereby the actual gas chamber is a separate element that can be permanently coupled with or be separated from a gas duct extending to a patient. In the invention, the anesthetic fluid container may include not only a fluid chamber and a gas chamber but also an inlet passage for a gas flowing e.g. from gas tanks into and an outlet passage from the gas chamber as well as a passage for a gas flowing from gas tanks to by-pass the gas chamber to a patient, i.e. a classic vaporizer as a whole. The connecting element need not necessarily be directly coupled with the conduit 5 or 6 but it can also be coupled between the gas chamber and the fluid chamber, especially in the case that the container only includes a fluid chamber but not a gas chamber. Anyway, and even in this case, the container must be regarded as being coupled with the conduit 5 or 6 through the intermediary of a connecting element. Neither is it necessary to deliver a portion of the fresh gas flow through the gas chamber 3 but, instead, an anesthetic vaporized from the fluid chamber may be forced by the action of a pressure along the conduit 6 towards the conduit 4, the mixing with a fresh gas not being effected until there. In this case, just one connecting element 8 is required. The above description of the invention has primarily focused on an embodiment, wherein the magnetic-field producing elements are included in a container even when the container is not coupled for operation. However, it is possible to mount the magnetic-field producing elements outside the container, e.g. on a body member, wherein the container can be coupled by means of a connecting element with a gas conduit extending to a patient. In this case, the identification or the coupling of a container could be effected e.g. in such a manner that the magnetic-field producing elements would penetrate into vacant positions provided in the container as each container containing a different anesthetic would only have certain predetermined positions vacant and the magnetic-field detecting elements would detect either those magnetic-field producing elements which are absent or those which are present.

Claims: An anesthetising apparatus including means for identifying an anesthetic fluid container, comprising at least two anesthetic fluid containers (1), which containers include at least a fluid chamber (2) for an anesthetic fluid and which containers are adapted to contain anesthetic fluids different from each other in terms of the chemical structure thereof, a gas chamber (3) for vaporizing the anesthetic originating from the fluid chamber, which gas chamber can be part of the container or a chamber separated from the container, and a connecting element (8) for coupling the container either directly or indirectly with a conduit (6) extending to a patient for supplying the anesthetic to a patient, wherein each said container is detachable from the connecting element and replaceable with another container possibly containing a different anesthetic fluid, wherein the means for identifying an anesthetic fluid container comprises a magnetic-field producing element (12), by means of which element the containers containing different anesthetic fluids are designated distinctly from each other, and a magnetic-field detecting element (13) separated from the container, which magnetic-field detecting element remains in its position during a container replacement process, and an identification element (15) which is adapted to receive a signal from the magnetic-field detecting element and which identification element, in response to the received signal, is adapted to identify which anesthetic fluid is contained in a relevant container, characterised in that the magnetic-field producing element (12) is adapted to produce a permanent magnetic field which is continuously detectable by the magnetic-field detecting element (13) while a respective container (1) remains coupled to the conduit (6). An apparatus according to claim 1, wherein each container (1) has a plurality of sites (11) for accommodating at least one magnetic-field producing element (12), wherein each of a corresponding plurality of magnetic-field detecting elements (13) is positioned to be adjacent each respective site (11) so as to detect a magnetic field thereat when the container (1) is coupled to the conduit (6), and wherein each container (1) is identifiable by the pattern of magnetic fields detected among the sites (11). An apparatus as set forth in claim 1, characterised in that the apparatus includes at least one magnetic-field producing element (12) per container, yet in such a manner that the containers containing different anesthetic fluids are designated distinctly from each other by means of one or more magnetic-field producing elements. An apparatus as set forth in claim 1, characterised in that the containers containing different anesthetics are designated distinctly from each other by means of one or more magnetic-field producing elements in such a manner that the containers containing different anesthetics include one feature, such as the location of an element or the direction of a magnetic field or the number of elements, which is different from those in the other containers. An apparatus as set forth in any of the preceding claims, characterised in that the number of magnetic-field detecting elements (13) is at least equal to, preferably at least twice the number of magnetic-field producing elements (12) per container. An apparatus as set forth in any of the preceding claims, characterised in that the number of magnetic-field detecting elements is at least equal to that of containers containing different anesthetics. An apparatus as set forth in any of the preceding claims, characterised in that the containers containing different anesthetics are provided with a plurality of predetermined positions (11) for selecting one or more positions which can be fitted with the magnetic-field producing element (12). An apparatus as set forth in claim 7, characterised in that for each possible position in the containers containing different anesthetics there is a magnetic-field detecting element. An apparatus as set forth in any of the preceding claims, characterised in that the magnetic-field detecting elements are spaced apart from the container and included preferably permanently in a body member (14), which is also fitted with a container containing a desired anesthetic, which anesthetic is to be supplied to a patient and which body member can be alternately fitted with individual containers. An apparatus as set forth in any of the preceding claims, characterised in that one or more magnetic-field detecting elements (13) is mounted on a body member (14), which is fitted with a container for coupling the same by means of the connecting element (8) with the conduit (6) extending to a patient and which magnetic-field detecting element or elements are located within the sphere of influence of the magnetic-field producing elements fitted in positions (11) included in the containers when the container is mounted on the body member (14), but are not located within the sphere of influence when the container is not properly coupled with the conduit (6) by means of the connecting element (8). An apparatus as set forth in any of the preceding claims, characterised in that between the connecting element (8) and the conduit (6) supplying gas to a patient there is the gas chamber (3). An apparatus as set forth in any of claims 1 to 10, characterised in that the gas chamber (3) is located between the connecting element (8) and the fluid chamber (2). A vaporizer comprising an anesthetising apparatus as claimed in any preceding claim. A method for identifying an anesthetic fluid container for use when anesthetics of different chemical structures, the number of said anesthetics being at least two, are each contained in a respective container (1), wherein said anesthetic fluid container is coupled either directly or indirectly with a conduit (6) extending to a patient, along which conduit a vaporised anesthetic originating from the anesthetic container is delivered to the respiratory tracts of a patient, yet in such a manner that the anesthetic is mixed with an oxygen-containing gas upstream of the respiratory tracts of a patient, wherein the containers each containing a different respective anesthetic are designated distinctly from each other by means of a magnetic-field producing element (12), whereby the presence of such element can be detected by means of a magnetic-field detecting element (13) prior to supplying a patient with a vaporized anesthetic originating from its respective container, said detection being a basis for identifying an anesthetic container and, thus, an anesthetic fluid contained therein, characterised in that the magnetic-field producing element (12) is adapted to produce a permanent magnetic field which is continuously detectable by the magnetic-field detecting element (13) while a respective container (1) remains coupled to the conduit (6). A method according to claim 14, wherein each container (1) has a plurality of sites (11) for accommodating at least one magnetic-field producing element (12), wherein each of a corresponding plurality of magnetic-field detecting elements (13) is positioned to be adjacent each respective site (11) so as to detect a magnetic-field thereat when the container (1) is coupled to the conduit (6), and wherein each container (1) is identifiable by the pattern of magnetic-fields detected among the sites (11). A method as set forth in claim 14, characterised in that the magnetic-field detecting element (13) is used for monitoring the presence or absence of a magnetic-field. A method as set forth in any of claims 14 to 16, characterised in that the presence of said magnetic-field producing element (12) is detected by establishing the direction or location of a magnetic field or the number of magnetic fields. A method as set forth in claim 17, characterised in that the direction of a magnetic field is established by means of two magnetic-field detecting elements (13). A method as set forth in claim 17, characterised in that the direction of a magnetic field is established by detecting which of the poles of said magnetic-field producing element is directed towards the magnetic-field detecting element. A method as set forth in any of the preceding claims 14 to 17, characterised in that a container containing any given anesthetic is distinguished from a container containing some other anesthetic by means of one or more magnetic-field producing elements included in a container. A method as set forth in any of the preceding claims 14 to 17, characterised in that the containers containing different anesthetics are provided with one or more magnetic-field producing elements in such a manner that the position of one or more elements included in the container is different from the position of one or more elements included in some other container containing a different anesthetic.

Inventors: KANKKUNEN JUKKA, PUUKANGAS PERTTI, KANKKUNEN, JUKKA, PUUKANGAS, PERTTI
Applicants: INSTRUMENTARIUM CORP, INSTRUMENTARIUM CORPORATION
Application year: 1995
Main classification: A61M16
IPC codes: A61M16, B67D7