Surgery – Respiratory method or device – Means for cooling respiratory gas or respiration device
Reexamination Certificate
2001-08-06
2004-05-04
Lewis, Aaron J. (Department: 3743)
Surgery
Respiratory method or device
Means for cooling respiratory gas or respiration device
C128S205120
Reexamination Certificate
active
06729329
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns treatment of waste anesthetic gas. In particular the invention pertains to the removal of halocarbons from waste anesthetic gas of a healthcare facility before the gas is discharged to atmosphere in order to decrease atmospheric pollution.
2. Description of the Prior Art
Anesthesia machines in surgical facilities (both hospital and outpatient) emit significant quantities of waste gases. Currently these gases are “scavenged” and diluted with air in a system of dedicated pipes. However, they are then vented to the atmosphere outside the building. The average composition of the waste gases is estimated to be:
Oxygen
25-30%
Nitrogen
60-65%
Nitrous oxide
5-10%
Volatile halocarbon
0.1-0.5%
The halocarbons (primarily halogenated methyl ethyl ethers) represent an increasingly significant source of environmental concern, because other halocarbon emission has recently been reduced by legislative and other initiatives. These compounds (similar to refrigerants Freon-12® and others) can contribute to ozone depletion and, to a lesser extent, environmental warming. Currently no regulation of these emissions exists, although it is anticipated that regulation of them will occur in the near future.
Several techniques have been employed to treat waste anesthetic gases. U.S. Pat. No. 4,259,303 describes treating laughing gas with a catalyst. Adsorption of anesthetic gases by charcoal granules is described in U.S. Pat. No. 5,044,363. Destruction of anesthetic gases by heating in the presence of a catalyst is described in U.S. Pat. No. 5,759,504.
Identification of Objects of the Invention
A primary object of the invention is to provide a system and method for removing volatile halocarbons of waste anesthetic gases from a surgical facility before such gases are vented to the atmosphere.
Another object of the invention is to provide an economical system and method for substantially preventing atmospheric venting of volatile halocarbons of waste anesthetic gas while eliminating the need of prior art catalysts, charcoal granules and heating techniques.
SUMMARY OF THE INVENTION
The objects identified above, as well as other advantages and features are embodied in a system and method which uses condensation (“cold trap”) technology such that the temperature of the halocarbons is lowered to a point where the vapor pressure of the halocarbons is negligible. In other words, the halocarbon gas is liquefied through refrigeration. The source of refrigeration is liquid oxygen at a surgical facility, which must be warmed for ordinary use at a surgical facility, such as a hospital or outpatient clinic. The waste anesthetic gas is passed first through a first set of condensing coils where water vapor in the gas is condensed by virtue of the cold oxygen flowing through the condensing coils. The remainder of the gas from the first set of condensing coils is passed to a second set of coils (with cold oxygen gas flowing through them) where the gas temperature is lowered to about −150° C. at which point the halocarbons are liquefied. The remainder of the anesthetic gas is vented to atmosphere.
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Brown AC, Canosa-Mas CE, Parr AD, et al.: Tropospheric lifetimes of halogenated anaesthetics. Nature 1989; 341: 635-637.
Langbein T, Sonntag H, Trapp D, et al.: Volatile anaesthetics and the atmosphere: atmospheric lifetimes and atmospheric effects of halothane, enflurane, isoflurane, desflurane and sevoflurane. Br J Anaesth 1999; 82: 66-73.
McCulloch, A.: Letter to Editor regarding Langbein, et al. 1999 paper. Br J Anaesth 2000; 84 (4): 534-36.
Andrews & Kurth LLP
Bush Gary L.
Lewis Aaron J.
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