Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Reexamination Certificate
1999-11-05
2001-09-18
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
C128S205230, C128S203130, C128S204220, C128S202220
Reexamination Certificate
active
06289891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method and to an apparatus for preventing mixing of different anaesthetics in an anaesthesia system.
2. Description of the Prior Art
During anaesthesia, the patient is usually supplied with a gas mixture containing nitrous oxide, oxygen and an anaesthetic. Generally, one of the anaesthetics desflurane, enflurane, isoflurane, halothane or sevoflurane is the anaesthetic employed. These are all liquid at room temperature (even though desflurane has a boiling point very close to normal room temperature).
The anaesthetic administered to the patient therefore is vaporized in an anaesthesia machine connected to the patient. Vaporization is usually performed by a vaporizer that can be devised in many ways. A number of different kinds of vaporizers are described in the literature and are well known to those skilled in the art. Since details of the vaporizer design and function are not of essential relevance to the present invention, they need not be specified below.
Since some liquid anaesthetic is consumed, however, occasions arise when the anaesthesia machine needs to be replenished with new anaesthetic.
Erroneous replenishment with an anaesthetic other than the anaesthetic currently in the anaesthesia machine is always a possibility, thereby posing a major risk to the patient.
Since the patient is at great risk during anaesthesia, there are a number of known procedures available for avoiding mixing.
One known procedure involves indexing. This means that the cylinders containing anaesthetics have different features. One known procedure entails assigning each anaesthetic a unique color. The contents of a color-coded cylinder may only be added to a correspondingly color-coded vaporizer in the anaesthesia machine.
Since this procedure is obviously not foolproof, systems employing this technique can be augmented with mechanical indexing, i.e. a cylinder of anaesthetic will only mate with a vaporizer equipped with a corresponding receptacle.
Even though this combination is safer than color coding alone, it is not completely safe. This is because different vaporizers around the world do not fit this indexing system because of their age or use of alternative technology. Vaporizers are sometimes emptied after use and the evacuated anaesthetic is re-used for inducing subsequent anaesthesia.
Yet another known procedure is to arrange a measurement unit inside the anaesthesia machine, either in the anaesthesia machine's gas flow paths or in an anaesthetic vessel in a vaporizer. The measurement unit is able to identify the anaesthetic, and anaesthesia can be stopped and/or an alarm sounded if the system detects any mixture of anaesthetics in the gas flow paths.
Since anaesthetics have similar molecular structures, they also have very similar properties. Therefore, reliable identification of even “pure” anaesthetic is difficult. Identifying mixtures of anaesthetics is even more difficult.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a safety system able to identify, more safely and effectively than hitherto, the situation in which inadvertent mixing of anaesthetics is imminent during replenishment with a new anaesthetic.
Another object of the present invention is to provide a safety system that safely and effectively prevents inadvertent mixing of anaesthetics in an anaesthesia machine.
Another object of the invention is to provide a method for avoiding inadvertent mixing of anaesthetic agents in an anaesthesia machine during replenishment with new anaesthetic.
The above object is achieved in accordance with the principles of the present invention in a method and a safety system for avoiding inadvertent mixing of two different anaesthetics in an anaesthesia apparatus when a new anaesthetic from a container is added to the anaesthesia apparatus wherein a currently-employed anaesthetic is already present in gaseous and/or liquid form, wherein the identity of the new anaesthetic is determined before it comes into contact with the currently-employed anaesthetic in the anaesthesia apparatus, and wherein the new anaesthetic is allowed to come into contact with the currently-employed anaesthetic only if the new anaesthetic is the same as the currently-employed anaesthetic.
The inventive safety system and method are based on identification of new anaesthetic with a suitable measurement technique before it is allowed to come into contact with the first anaesthetic in the anaesthesia machine. Known measurement techniques include spectrophotometry, determination of the anaesthetic's refractive index, determination of the anaesthetic's density etc.
The use of a blocking unit can completely prevent new anaesthetic from coming into contact with the first anaesthetic if an error should occur. Anaesthesia can then continue without interruption at the same time as the new anaesthetic is evacuated and replenishment (possibly with intermediate cleaning of the flow channel) with correct new anaesthetic.
The measurement unit is installed at a suitable location in the anaesthesia machine on which the safety system is to be employed. In certain instances, therefore, arranging the measurement unit in the flow channel may be advantageous. In others instances, it may be advantageous, or even necessary, to arrange the measurement unit outside the flow channel, i.e. on the exterior of the anaesthesia machine.
In principle, the flow channel also can be a part of the safety system. This means, in principle, that the safety system is used as a part of a device for replenishing anaesthetic. In this instance, it would be easier to tailor a device, with a minimum of measures, to a number of different kinds of anaesthesia machines.
It is advantageous to include an alarm in the safety system to provide a warning when inadvertent mixing is about to occur.
Identifying the first anaesthetic is also advantageous for further enhancing the system's safety (without reliance on the accuracy of information entered on the identity of the first anaesthetic).
This identification can be performed by filling an empty anaesthesia machine with the first anaesthetic in the same way as the new anaesthetic. The measurement unit then can identify the first anaesthetic and send this information to a memory. When the machine is replenished with a new anaesthetic, it is easy for the system to compare the identity of the new anaesthetic with information stored about the first anaesthetic.
A second measurement unit, in contact with the first anaesthetic, can alternatively be arranged in the anaesthesia machine. Measurement and comparison of identities can then be performed simultaneously. This may be preferable in instances in which the anaesthesia machine already contains an analyzer or the like for identifying the anaesthetic in the anaesthesia machine.
REFERENCES:
patent: 3910222 (1975-10-01), Metivier
patent: 4934358 (1990-06-01), Nilsson et al.
patent: 5293865 (1994-03-01), Altner et al.
patent: 5537992 (1996-07-01), Bjoernstijerna et al.
patent: 5572992 (1996-11-01), Kankkunen et al.
patent: 5730119 (1998-03-01), Lekholm
patent: 5824885 (1998-10-01), Lekholm
patent: 5957129 (1999-09-01), Tham et al.
patent: 0 727 654 (1996-08-01), None
Patel Mital
Schiff & Hardin & Waite
Siemens Elema AB
Weiss John G.
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