Device for absorbing a gas mixture consisting of laughing gas and anesthetic vapor

A device for removing at least laughing gas and anesthetic vapor from a gas sample based on a molecular sieve shall be improved such that it possesses good adsorption properties for both gas components. A molecular sieve arrangement is provided, which is flown through from a gas inlet to a gas outlet and comprises a first molecular sieve area with a first pore size between about 0.3 nm and 0.5 nm and a second molecular sieve area with a second pore size between about 0.8 nm and 1 nm.

FIELD OF THE INVENTION 
The present invention pertains to a device for removing at least laughing 
gas and anesthetic vapor from a gas sample. 
BACKGROUND OF THE INVENTION 
A laughing gas-oxygen mixture, to which a defined amount of anesthetic is 
added in the form of a vapor, is used in many cases in the field of 
inhalation anesthesia. Since prior-art anesthetic respirators operate, in 
general, in the so-called excess gas mode, in which more gaseous 
anesthetic is fed into the respiratory circuit than is consumed by the 
patient, a certain volume of gas must be removed and disposed of via a 
central gaseous anesthetic exhaust unit during the use of the apparatus. 
An activated carbon filter is provided as the adsorbent for anesthetic 
vapor in a gaseous anesthetic processing unit known from DE 42 08 521 A1, 
and the laughing gas is decomposed into oxygen and nitrogen in a catalyst 
cartridge, because it is not bound by the activated carbon filter. This 
method of processing gaseous anesthetics is relatively expensive, because 
at least two purification steps are necessary. 
It has been known from EP 113 023 B1 that laughing gas can be removed from 
a hydrogen-nitrogen monoxide gas mixture with a molecular sieve having a 
pore size between 0.4 and 1 nm. 
However, the removal of two components from a gas mixture, laughing gas and 
anesthetic vapor in this case, is possible only insufficiently with the 
prior-art molecular sieve, because only one of the components is always 
adsorbed sufficiently, depending on the pore size. 
SUMMARY AND OBJECTS OF THE INVENTION 
The primary object of the present invention is to provide an adsorbent for 
a mixture of laughing gas and anesthetic vapor based on a molecular sieve 
that possesses good adsorption properties for both gas components. 
According to the invention, a device is provided for removing at least 
laughing gas and anesthetic vapor from a gas sample. The device includes a 
molecular sieve arrangement formed of a mixture of molecular sieves with a 
first pore sires between 0.3 nm and 0.5 nm and a second pore sizes between 
about 0.8 nm and 1 nm. 
The advantage of the present invention is essentially that the separation 
performance is markedly improved by the use of a molecular sieve with 
different adsorption ranges designed for the components to be removed. A 
molecular sieve arrangement consisting of a molecular sieve mixture with 
first pore sizes between 0.3 nm and 0.5 nm and second pore sizes between 
0.8 nm and 1 nm is especially suitable for the adsorption of a gas mixture 
consisting of anesthetic vapor and laughing gas. 
The molecular sieve according to the present invention may be used 
especially advantageously at the excess gas outlet of an inhalation 
anesthesia apparatus to remove laughing gas and anesthetic vapor. Another 
advantageous application of the molecular sieve according to the present 
invention is on components of the anesthesia apparatus through which the 
anesthetic gas flows and from which anesthetic gas escapes during brief 
periods of time, e.g., during changeover processes. For example, the 
anesthetic gas can be eliminated immediately at the point at which such 
gas escapes from a changeover switch by means of a molecular sieve of a 
cartridge-like design, which is then replaced by the service provider at 
predetermined time intervals. 
One exemplary embodiment of the present invention is shown in the drawings 
and will be explained in greater detail below.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 shows schematically a first molecular sieve arrangement 1, through 
which medium flows from a gas inlet 2 to a gas outlet 3. The first 
molecular sieve arrangement 1 comprises a molecular sieve mixture with a 
first pore size 4 between 0.3 nm and 0.5 nm and a second pore size 5 
between 0.8 nm and 1 nm. 
The different pore sizes 4, 5 are illustrated in FIG. 1 by circles with 
larger and smaller radii. 
FIG. 2 shows schematically a second molecular sieve arrangement 10. 
Identical components are designated with the same reference numbers as in 
FIG. 1. What is different from FIG. 1 is that molecular sieve components 
with the first pore size 4 are integrated in a first molecular sieve area 
6 and molecular sieve components with the second pore size 5 are 
integrated in a second molecular sieve area 7. The flow through the second 
molecular sieve arrangement 10 is in the direction from the second area 7 
into the first area 6. A molecular sieve structure thus stratified offers 
the advantage that a high degree of purity is obtained at the gas outlet 
3. 
The present invention shall be illustrated on the basis of an example: 
Six g a of molecular sieve mixture, e.g., a mixture arrangement purchased 
from the firm of Merck, Darmstadt, having a pore size of 1 nm and 0.5 nm, 
were charged with about 10,000 ppm of halothane and about 10,000 ppm of 
laughing gas (corresponding to about 200 mg of halothane and about 200 mL 
of gaseous laughing gas). The charge of the molecular sieve was about 19 
mL of gaseous halothane (corresponding to 50%) and 5 mL (corresponding to 
14%) of laughing gas per g of molecular sieve. The regeneration of the 
molecular sieve was performed by heating for 4 hours at 120.degree. C. 
While a specific embodiment of the invention has been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.