Abstract:
An arrangement for passive gas sampling of a breathing gas in a breathing system has an element disposed in a tube for the passive diversion of a portion of the flow of breathing gas to a measurement chamber.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an arrangement for passive gas sampling of the type suitable for sampling a breathing gas.  
           [0003]    2. Description of the Prior Art  
           [0004]    In breathing systems such as ventilators and anesthetic apparatus the breathing gas is analyzed regularly. This may be done directly in the main supply (with a so-called mainstream-analyzer) or by diverting a gas sample to a measuring chamber (so-called sidestream-analyzer).  
           [0005]    The diversion of the gas sample can be done actively by means of a pump or the like or passively, for example by creating a pressure variation between the pressure chamber&#39;s inlet and outlet. An example of the latter is described in U.S. Pat. No. 6,450,968.  
         SUMMARY OF THE INVENTION  
         [0006]    An object of the present invention is to provide an alternative to known arrangements for passive gas sampling.  
           [0007]    The above object is achieved in accordance with the invention in an arrangement for passive gas sampling of a breathing gas in a breathing system, having a tube in which breathing gas flows, and an element disposed in said tube for passively diverting a portion of the flow of breathing gas to measurement chamber.  
           [0008]    A gas sample may be easily obtained passively using an element that diverts the gas sample from a flow of breathing gas to a measurement chamber. The element can take different forms in order to effectively divert the gas sample and furthermore can be designed to divert a gas sample in one or two flow directions.  
           [0009]    The above object also is achieved in accordance with the invention in an arrangement for passive gas sampling of a breathing gas in a breathing system, having a housing element in which a measurement chamber is disposed, and having a first connection for reception of an inspiration flow, a second connection for discharging an expiration flow, and a third connection for discharging the inspiration flow and reception of the expiration flow, the housing containing gas flow paths therein configured so that the first connection and the third connection conduct the received inspiration flow and the expiration flow along a substantially straight path toward the measurement chamber.  
           [0010]    This solution builds upon the same principle, but instead of an element that diverts the gas sample, here the actual arrangement is designed to, in principle, force the entire gas flow to pass the measurement chamber. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 shows a first embodiment of an arrangement according to the invention.  
         [0012]    [0012]FIG. 2 shows an element in the arrangement according to the first embodiment.  
         [0013]    [0013]FIG. 3 shows a second embodiment of an arrangement according to the invention.  
         [0014]    [0014]FIG. 4 shows a third embodiment of an arrangement according to the invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]    A first embodiment of an arrangement  2  according to the invention is shown in FIG. 1. The arrangement  2  is formed as a tube  4 . A gas sample can be analyzed in a measurement chamber  6  according to a known method of analysis, e.g. optical, acoustical or electrochemical.  
         [0016]    Gas samples are conducted into the measurement chamber  6  via an element  8  arranged in the tube  4 . The element  8  is curved to lead the gas sample into the measurement chamber  6 . As is shown in FIG. 2 the element  8  is also curved around a central axis  10 . In the lower portion of FIG. 2 the profile is shown at different sections of the element  8 . A first section A shows that the element  8  is straight at its base; similarly for the second section B. Then the element  8  is successively curved, as is shown in a third section C and a fourth section D. At its tip the element  8  finally presents an essentially round ring, as is shown in a fifth section E.  
         [0017]    The successive curving around the center axis  10  contributes to an optimization of the flow of the gas sample into the measurement chamber  6 .  
         [0018]    A second embodiment of an arrangement  12  according to the invention is shown in FIG. 3. The arrangement  12  again is formed as a tube  14 . A gas sample can be analyzed in a measurement chamber  16  according to a known method of analysis. An element  18  is arranged in the tube  14  to conduct a gas sample into the measurement chamber  16 .  
         [0019]    Unlike the first exemplary embodiment, the arrangement  12  according to the second exemplary embodiment is designed to sample gas in both flow directions within the tube  14 . This can be done by providing the element  18  with an extension in both the directions. The arrangement  12  is therefore suitable for placement near a patient and to sample gas during both inspiration and expiration.  
         [0020]    The gas sample will be led in from one side (from the left side in FIG. 3 when the gas flow is from the left to the right and from the right side when the gas flow is from the right to the left) and at the same time the contents of the measurement chamber  16  are forced out through the other side (right to left).  
         [0021]    A third embodiment of an arrangement  20  according to the invention is shown in FIG. 4.  
         [0022]    The arrangement  20  has a housing element with a first connection  22  for reception of an inspiration flow from a (not shown) breathing arrangement, a second connection  24  for expulsion of an expiration flow and a third connection  26  for expulsion of the inspiration flow and reception of the expiration flow to and from a (not shown) patient. A measurement chamber  28  is formed in the arrangement  20  where a gas sample can be analyzed in a known way. The arrangement  20  is designed so that the first connection  22  and the third connection  26  respectively conduct the received inspiration flow and expiration flow essentially straight towards the measurement chamber  28 .  
         [0023]    The measurement chamber  28  is essentially completely open to the flow paths in the arrangement  20 , which is why it constitutes an intermediate design between a mainstream-analyzer and a sidestream-analyzer. Gas samples are efficiently swapped during both inspiration and expiration as the breathing gas flow is then directed toward the measurement chamber  28 .  
         [0024]    Combinations of the described exemplary embodiments can easily be done.  
         [0025]    For example the design of the element  8  in FIG. 1 can be used for the element  18  in FIG. 3.  
         [0026]    Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.