Surgery – Respiratory method or device – Means for supplying respiratory gas under positive pressure
Reexamination Certificate
1999-04-15
2001-12-11
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Means for supplying respiratory gas under positive pressure
C128S203120, C128S203140, C128S203280, C128S204280, C128S205130, C128S205120, C128S205160
Reexamination Certificate
active
06328036
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to an anesthetic apparatus of the type which is operable at least as an open system, wherein a connector for fresh gas is a part of an inspiratory section of a breathing circuit, and a bellows system and an outlet valve are part of an expiratory section of the breathing circuit. The present invention is also directed to a method for operating such an anesthetic apparatus.
2. Description of the Prior Art
Most anesthetic apparatuses are devised for operation in different modes, especially with open and closed systems.
In an open system, all the gas prepared in the anesthetic apparatus and delivered to the patient during inspiration (inhalation) is removed from the anesthetic apparatus and carried to an evacuation unit during expiration (exhalation).
In a closed system, a larger or smaller part of the gas expired by the patient is returned in the anesthetic apparatus to the patient at the next inspiration. Gas is usually returned to the patient via an absorber to remove carbon dioxide from the gas.
One problem with anesthetic apparatuses of this kind is that the compressible volumes in the breathing circuit are much larger than in apparatuses that cannot be switched between open and closed systems.
The large compressible volume in the expiratory section of the breathing circuit is a particular problem when the anesthetic apparatus operates as an open system. During inspiration, more than a negligible part of the programmed tidal volume may be consumed in compressible volume, since inspiratory pressure is greater than expiratory pressure.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an anesthetic apparatus with which the aforementioned problems are eliminated.
Another object of the present invention is to provide a method for operating an anesthetic apparatus that eliminates the aforementioned problems.
The above object is achieved is accordance with the invention in an anesthetic apparatus having a control unit and a breathing circuit with a connector for fresh gas, a bellows system and an outlet valve, the anesthetic apparatus being operable at least as an open system wherein the connector is a part of an inspiratory section of the breathing circuit and the bellows system and the outlet valve are a part of an expiratory section of the breathing circuit, and wherein the control unit regulates the bellows system during inspiration so that a counter-pressure, substantially corresponding to the pressure of the fresh gas at the connector, is maintained in the expiratory section of the breathing circuit.
The bellows system in the expiratory section of the breathing circuit is, in conventional systems, disconnected in functional respects when the anesthetic apparatus operates as an open system. By instead, in the inventive method and apparatus, making active use of the presence of the bellows system and controlling the bellows system (and possibly even the outlet valve) by a control unit to supply gas to the expiratory section of the breathing circuit during inspiration, a counter-pressure can be built up in this section. None of the fresh gas supplied to the breathing circuit's inspiratory section will then be consumed by compressible volume.
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Emtell Par
Kock Mikael
Patel Mital
Schiff & Hardin & Waite
Siemens-Elema AB
Weiss John G.
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