GB2254005A

GB2254005A - Anaesthetic evaporator for dosing different anaesthetics

Info

Publication number: GB2254005A
Application number: GB9206596A
Authority: GB
Inventors: Wolfgang Falb; Karl-Ludwig Gippert; Ulrich Heim; Uvo Holscher; Siegfried Kiske; Gotz Kullik; Ralf-Ernst Loser; Christoph Maurer
Original assignee: Draegerwerk AG and Co KGaA
Current assignee: Draegerwerk AG and Co KGaA
Priority date: 1991-03-28
Filing date: 1992-03-25
Publication date: 1992-09-30
Also published as: GB9206596D0; FR2674438A1; DE4110211A1

Abstract

In an anaesthetic evaporator with a dosing unit 2 and with a plurality of evaporator chambers 3 which can be selectively attached to the dosing unit for different anaesthetics 8, the dosing unit (2) is provided with a heating and cooling means 4 engaging into the evaporator chamber 3 operable under control of a regulator 5 to set a constant vapour pressure of 700 millibar for each anaesthetic. Cooling means 11 specific to the respective chamber and its anaesthetic signals the regulator which also receives a sensed temperature of the anaesthetic and actuates the heating and cooling means to achieve the set vapour pressure. In another embodiment, the respective anaesthetic is provided in a supply container which is attachable to an evaporator chamber firmly connected to the dosing unit and mounting a Peltier heating and cooling device. <IMAGE>

Description

2 2 5 4,0 0 5 -I- 1 ANAESTHETIC EVAPORATOR FOR DOSING DIFFERENT

ANAESTHETICS The invention relates to an anaesthetic avaporator having a dosing unit and having evaporator chambers which can be attached to the dosing unit for different anaesthetics.

An anaesthetic evaporator is known from US-A4693853. This known anaesthetic evaporator comprises a dosing unit with an attachable evaporator chamber, whereby, in order to change to a different anaesthetic, the evaporator chamber is separated from the dosing unit and is exchanged for an evaporator chamber containing another anaesthetic. The dosing unit remains attached to the anaesthesia apparatus. In this is way, it is possible to dose several anaesthetics with only one dosing unit in combination with various evaporator chambers. The adaptation of the setting means of the dosing unit to the anaesthetic used is effected such that, by means of an identifier which engages into the dosing unit, an appropriate scale for dosing the anaesthetic is attained. An alternative way of adapting the dosing unit to the appropriate anaesthetic consists in providing a temperaturedependent regulating device by means of which a bypass valve is controlled, which valve influences the amount of gas flowing through the evaporator chamber. The control of the regulating device is effected by means of an anaesthetic-specific code and by means of a temperature sensor which extends into the evaporator chamber.

In this known anaesthetic evaporator, it is a disadvantage that, for the adaptation to a different anaesthetic, contact with the dosing unit is necessary, in that, for example, an appropriate scale for the dosing is released, or by means of a regulating device the gas flow is influenced by the evaporator chamber..

This results in a considerable expenditure in terms of construction, since, by appropriate logistics, it must be ensured that the dosing unit is always set for the correct anaesthetic.

In US-A-3251361, there is disclosed an anaesthesia system having an anaesthetic evaporator which in turn has an evaporator chamber which is tempered by a Peltier element to a certain temperature for the setting of a saturation concentration value. The use of various evaporator chambers containing different anaesthetics, however, is not disclosed in this document.

The object of the present invention is to improve an anaesthetic evaporator in such a way that the adaptation of the dosing unit to the respective anaesthetic is simplified.

According to the present invention, there is provided an anaesthetic evaporator comprising a dosing unit and one of a plurality of evaporator chambers for containing different anaesthetics each of which chambers can be associated with the dosing unit, wherein the dosing unit is provided with a heatingcooling means able to heat or cool the anaesthetic in the respective evaporator chamber when the latter is so associated with the dosing unit whereby the heatingcooling means can then be used to set a dosing parameter which is the same for different anaesthetics.

According to the invention, the dosing unit is provided with a heatingcooling means (hereinafter referred to as a "tempering means") with which a dosing parameter can be set which is fixed for all anaesthetics.

The temperaing means is associated with the evaporator chamber, e.g. can engage into the evaporator chamber or can be attached releasably to the evaporator chamber.

The advantage of the invention lies in the fact that, to adapt the dosing unit to a different anaesthetic, contact with the dosing unit is no longer necessary, but the adaptation of the anaesthetic- specific evaporator chamber to the dosing unit is undertaken by means of a tempering means which is brought into thermal contact with the anaesthetic, e.g. engages into the evaporator chamber so as to be in thermal contact with the anaesthetic. The individual anaesthetics differ from one another, with regard to their physical properties, mainly in vapour pressure. If a known dosing system is now operated with a different anaesthetic, the contact in the dosing for setting in respect of the appropriate anaesthetic consists in setting the dosing system at the respective vapour pressure. For an anaesthetic evaporator operating according to the bypass principle, for example in accordance with DE-C-1271903, this means that flow restrictors in the dosing unit, which are responsible for the division of the gas flow to the bypass and the evaporator chamber, must be altered. By the present invention, however, it is now possible to compensate for the change of vapour pressure by the fact that the tempering means engages into the evaporator chamber, whereby a dosing parameter is set which is fixed for all anaesthetics, without changing the flow restrictors. A temperature compensation, as is present, for example, in the anaesthetic evaporator known from DE-C-2507261, is then no longer required according to the invention, due to the presence of the tempering means.

It is advantageous for the evaporator chamber to comprise a supply container for the anaesthetic and an evaporator container, whereby the tempering means is connected only to the evaporator container. The supply container and the evaporator container are connected by means of a conveying device and a conveying valve such that only as much anaesthetic is present in the evaporator container as can evaporate within a certain time interval. The tempering means therefore needs only to be dimensioned with regard to the anaesthetic located in the evaporator container.

In an advantageous construction, the evaporator container, forming part of the evaporator chamber, is firmly connected to the dosing unit and the tempering means, and the supply container only is constructed as a unit to be attached to the evaporator container. The supply container can be, for example, a tank which is pushed into an appropriate holding fixture of the anaesthetic evaporator, or a cartridge which is filled with anaesthetic at the time that it is produced.

In an advantageous embodiment, the tempering means has a concentric type of construction so that it can be inserted as a ring or bar into the evaporator chamber or the evaporator container.

To compensate for the influence of different anaesthetics on the dosing unit, it is advantageous to control the tempering means in the evaporator chamber or the evaporator container such that, with each anaesthetic used, the same vapour pressure is set as the dosing parameter.

In an advantageous embodiment, the tempering means is controlled such that a vapour pressure is set under ambient pressure. For example, the anaesthetic halothane has, at an ambient temperature of 2WC and at an ambient pressure of 1013 millibar, a vapour pressure of 260 millibar. The absolute value of the vapour pressure of halothane under these conditions is below the ambient pressure of 1013 millibar. If the halothane is now heated, the vapour pressure rises, for example, to a value of 700 millibar, which likewise is below the ambient pressure. Anaesthetics which have similar properties to halothane, for example enflurane, can be set by variable heating to a respectively constant vapour pressure of 700 millibar. If, on the other hand, there is used an anaesthetic which boils at ambient temperature, cooling is generally necessary in order to achieve the vapour pressure of 700 millibar. The tempering means must therefore be constructed both for heating and for cooling. In addition to vapour pressure, the dosing is also influenced by the viscosity of the anaesthetic. Since, for medical uses, concentration values of only a few per cent are used, this influence is negligible.

In an advantageous embodiment of the invention, the connection between the dosing unit and the evaporator chamber or the supply container is effected by means of an electrical disconnecting point. By means of this disconnecting point, for example, the pressure and temperature within the evaporator chamber, and an anaesthetic-specific code for the evaporator chamber or for the supply container, can be transmitted to the dosing unit.

The invention will now be described, by way of example, with reference to the drawings, in which: Figure 1 is a schematic representation of an anaesthetic evaporator having a concentric arrangement of the tempering means in the evaporator chamber; and Figure 2 is a schematic representation of an anaesthetic evaporator having a supply container and an evaporator container, and provided with a tempering means.

Figure 1 schematically shows a first anaesthetic evaporator 1 consisting of a dosing unit 2, an evaporator chamber 3 and a tempering means 4 (including a regulating device 5) connected to the dosing unit 2. The tempering means 4 engages into the evaporator -6 chamber 3 in a concentric type of construction.

The tempering means 4 has a heating means 6 and a cooling means 7 which can be controlled by the regulating device 5. The evaporator chamber 3, containing an anaesthetic 8, has a wick 9 for evaporating the anaesthetic 8 and also has, at a disconnecting point 10, a coding means 11 specific to the anaesthetic 8, whereby a code is passed to the regulating device 5 via a signal line 12. A temperature sensor 13 dipping into the anaesthetic 8 is likewise connected to the disconnecting point 10 and relays a temperature signal via the signal line 12 to the regulating device 5.

Inside the dosing unit 2, the path of the gas is illustrated schematically.

The gas flow 15 entering at a gas inlet 14 is divided into (a) a bypass flow 16 which pases via a bypass valve 17 to a gas outlet 18 and (b) an evaporator-chamber flow 19 which flows through the evaporator chamber 3 and back into the bypass flow 16 via an evaporator- chamber valve 20. The evaporatorchamber valve 20 is operated by a handwheel 21 for setting the anaesthetic concentration.

To put the first anaesthetic evaporator 1 into operation, the evaporator chamber 3 is first of all filled with the associated anaesthetic 8 via an anaesthetic-specific filling device 22 and is then connected to the dosing unit 2. By means of the coding means 11, the above-mentioned code is transmitted via the disconnecting point 10 to the regulating device 5 attached to the anaesthetic-specific evaporator chamber 3. For the dosing, for all anaesthetics 8 inside the evaporator chamber 3, a constant vapour pressure, for example 700 millibar, is set. With knowledge of the particular anaesthetic that is present, the regulating device 5 calculates the temperature at which the vapour pressure of the anaesthetic is 700 millibar. The actual temperature of the anaesthetic 8 is determined by the temperature sensor 13. Depending upon the difference between the actual temperature and the desired temperature, either the heating means 6 or the cooling means 7 of the tempering means 4 is put into operation by means of the regulating device 5, and the desired temperature is attained. The dosing of the anaesthetic vapour takes place via the handwheel 21, which has a uniform scale 23 for all anaesthetics 8.

Should a different anaesthetic 8 now have to be used, a second evaporator chamber (not shown), which is filled with a second anaesthetic and which has a second coding means, is connected to the dosing unit 2. Via the second coding means, the regulating device 5 receives the above-mentioned code relating to the second anaesthetic in the second evaporator chamber, and a second desired temperature, such that a vapour pressure of 700 millibar attained, is calculated. By the use of a constant vapour pressure, temperature compensation, as used in known anaesthetic evaporators, is not required.

In Figure 2, there is shown a second anaesthetic evaporator 30 in which the evaporator chamber 3 of Figure 1 is divided into a supply container 23 and an evaporator container 24.

In Figure 2, the same components are denoted with the same reference numerals as in Figure 1.

The evaporator container 24 is firmly connected to the dosing unit 2 and has a limited fill volume for anaesthetic 8.

The tempering means consists of a Peltier element 25, which abuts the evaporator container 24, and a cooling body 26. By means of an appropriate control, either cooling or heating can be effected by the tempering means.

The volume of anaesthetic 8 inside the evaporator container 24 is such that only the quantity of anaesthetic 8 which is required within an established time interval is present and tempered to the desired temperature. Due to the presence of a thermal mass which is comparatively small as compared with the evaporator chamber 3 of Figure 1, a Peltier element 25 with a small heating and cooling capacity is sufficient. The anaesthetic 8 to be evaporated is conducted, via a conveyer device 28 and a conveyer valve 27, into the evaporator container 24. Aeration of the supply container 23, for example during the filling via the filling device 22, is possible via a ventilation valve 29. The supply container 23 also has a coding means 11 for the anaesthetic 8 whereby a code is passed on to the regulating device 5 via the disconnecting point 10. Inside the evaporator container 24, for all anaesthetics, a constant vapour pressure is again set by means of the tempering by the Peltier element 25.

Claims

1. A anaesthetic evaporator comprising a dosing unit and one of a plurality of evaporator chambers for containing different anaesthetics each of which chambers can be associated with the dosing unit, wherein the dosing unit is provided with a heatingcooling means able to heat or cool the anaesthetic in the respective evaporator chamber when the latter is so associated with the dosing unit whereby the heating- cooling means can then be used to set a dosing parameter which is the same for different anaesthetics.

2. An anaesthetic evaporator according to claim 1, wherein the evaporator chamber comprises a supply container for the anaesthetic and an evaporator container, wherein the heating-cooling means can be connected to the evaporator container, and wherein the anaesthetic can be brought from the supply container into the evaporator container via a valve by means of a conveying device. 20

3. An anaesthetic evaporator according to claim 2, wherein the evaporator container can be connected to the dosing unit and wherein the supply container can be attached to the evaporator container.

4. An anaesthetic evaporator according to claim 1 or 2, wherein the tempering means has a concentric form of construction.

5. An anaesthetic evaporator according to any of claims 1 to 4, comprising a regulating device for controlling the heating-cooling means such that, as the dosing parameter, a constant vapour pressure is present in the evaporator chamber or the evaporator container for different anaesthetics.

6. An anaesthetic evaporator according to claim 5, wherein the vapour pressure can be set at a value below ambient pressure.

7. An anaesthetic evaporator according to claim 5, wherein the temperature of the heating-cooling means can be set at a value above ambient temperature.

8. An anaesthetic evaporator according to any of claims 1 to 7, wherein the connection between the dosing unit and the evaporator chamber, or between the dosing unit and the supply container, is effected by an electrical disconnecting point via which at least one anaesthetic-specific code can be transmitted.

9. An anaesthetic evaporator according to claim 1, substantially as hereinbefore described with reference to, and as shown in, Figure 1 or Figure 2 of the drawings.

10. Anaesthetic evaporator with a dosing unit and with evaporator chambers which can be attached to the dosing unit for different anaesthetics, characterized in that the dosing unit is provided with a tempering means engaging into the evaporator chamber, with which a dosing parameter can be set which is fixed for all anaesthetics.