Abstract:
The present invention seeks to provide a system for analyzing the exhaled breath of a subject, including a gas analyzer, sensitive to at least one component of the exhaled breath and a gas sampling catheter having a first end and a second end, the first end being in fluid flow communication with the gas analyzer, wherein the gas sampling catheter has a plurality of exhaled breath sampling holes formed therein.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to U.S. Provisional Patent Application Ser. No. 60/640,962 filed Dec. 28, 2004 and entitled CAPNOGRAPHIC SAMPLING CATHETER the disclosures of which are hereby incorporated by reference and priority of which is hereby claimed pursuant to 37 CFR 1.78(a) (4) and (5)(i). 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of catheters for use in sampling the breath of subjects, especially for the purpose of providing capnographic data concerning the subject. 
       BACKGROUND OF THE INVENTION 
       [0003]    The following U.S. patents are believed to represent the current state of the art: U.S. Pat. Nos. 5,787,885; 5,383,469; 5,335,656 and 4,485,822. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention seeks to provide a sampling catheter for use with a capnographic system. 
         [0005]    There is thus provided in accordance with a preferred embodiment of the present invention a system for analyzing the exhaled breath of a subject, including a gas analyzer, sensitive to at least one component of the exhaled breath and a gas sampling catheter having a first end and a second end, the first end being in fluid flow communication with the gas analyzer, the gas sampling catheter has a plurality of exhaled breath sampling holes formed therein in the vicinity of said second end. 
         [0006]    In accordance with a preferred embodiment of the present invention different ones of the plurality of sampling holes are disposed at different longitudinal positions along the gas sampling catheter. Additionally or alternatively, different ones of the plurality of sampling holes are disposed at different circumferential positions around the gas sampling catheter 
         [0007]    In accordance with a preferred embodiment of the present invention the system also includes a suction element, configured to remove fluid from the gas sampling catheter. 
         [0008]    In accordance with another preferred embodiment of the present invention the plurality of sampling holes are disposed in a generally helical pattern. 
         [0009]    In accordance with yet another preferred embodiment of the present invention the second end of the gas sampling catheter is sealed. Preferably, the first end of the gas sampling catheter is directly connected to the gas analyzer, thereby forming the fluid flow communication therebetween. Alternatively, the first end of the gas sampling catheter is connected to the gas analyzer by means of a breath conduit. 
         [0010]    In accordance with a further preferred embodiment of the present invention the gas sampling catheter is fitted with a suction port, the suction port being adapted to connect to the suction element. 
         [0011]    In accordance with a still further preferred embodiment of the present invention the gas sampling catheter has at least one circumferential protrusion formed therearound. 
         [0012]    In accordance with yet a further preferred embodiment of the present invention the system also includes an oxygen delivery tube mounted onto the gas sampling catheter, thereby forming a multilumen tube therewith and an oxygen source connected to the oxygen delivery tube for supply of oxygen thereto. 
         [0013]    There is additionally provided in accordance with a further preferred embodiment of the present invention a gas sampling catheter including a catheter tube being formed with a plurality of exhaled breath sampling holes. 
         [0014]    In accordance with a preferred embodiment of the present invention different ones of the plurality of sampling holes are disposed at different longitudinal positions along the catheter tube. Additionally or alternatively, different ones of the plurality of sampling holes are disposed at different circumferential positions around the catheter tube 
         [0015]    In accordance with a preferred embodiment of the present invention the plurality of sampling holes are disposed in a generally helical pattern. 
         [0016]    In accordance with another preferred embodiment of the present invention one end of the catheter tube is sealed. Preferably, the catheter tube has at least one circumferential protrusion formed therearound. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
           [0018]      FIG. 1  is a schematic illustration of a sampling catheter constructed and operative in accordance with a preferred embodiment of the present invention, which is typically used in a capnographic system; 
           [0019]      FIG. 2  is a schematic illustration of a sampling catheter constructed and operative in accordance with another preferred embodiment of the present invention, which is typically used in a capnographic system; 
           [0020]      FIGS. 3A and 3B  are sectional illustrations taken along respective section lines IIIA-IIIA and IIIB-IIIB in  FIG. 2 ; and 
           [0021]      FIG. 4  is a schematic illustration of a sampling catheter constructed and operative in accordance with yet another preferred embodiment of the present invention, which is typically used in a capnographic system. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]    Catheters are thin flexible tubes, generally open at both ends, which are widely used in health care, for insertion into a bodily cavity, duct or vessel, generally for either supplying or extracting fluids from organs accessible through the bodily cavity or duct. 
         [0023]    Traditional breath sampling is generally performed at the oral or nasal orifices using an appropriate cannula. There are a number of problems with such nasal or nasal/oral breath sampling such as dilution of the breath sample by the ambient air, and the difficulty of sampling effectively from a patient that alternates between nasal and oral breathing. 
         [0024]    Breath sampling by means of a catheter is more accurate than sampling methods at the oral or nasal orifices using an appropriate cannula, since catheter sampling is performed at the oral/nasal junction, or even closer to the source of the breath, and hence well away from any diluent effects from the sampling orifice. However, when using a breath sampling catheter, blockage of the sampling line by entrance thereto of liquids from the oral/nasal junction may occur. The design and structure of the sampling catheter of the present invention ensure that little or no blockage will occur, as described with more detail hereinbelow. 
         [0025]    Reference is now made to  FIG. 1 , which is a schematic illustration of a capnographic sampling system constructed and operative in accordance with a preferred embodiment of the present invention. Capnographic system  10  includes a sampling catheter  11  having a sampling portion  12 , which is preferably located at a lower end  13  of sampling catheter  11 . A number of sampling holes  14  are formed in the wall of the sampling catheter  11 , preferably within the sampling portion  12 . Sampling catheter  11  additionally includes an internal bore  16 , forming a passageway for the sampled fluid. 
         [0026]    Sampling holes  14  are preferably arranged at different longitudinal positions along the length of sampling catheter  11  and at different circumferential positions therearound. A preferred pattern for the location of the sampling holes  14  is in the form of a helix. This structure ensures that at least some of the sampling holes  14  remain open, even when one side of the catheter circumference is in contact with the passageway into which the sampling catheter  11  has been inserted. 
         [0027]    Additionally, the use of several sampling holes  14  ensures that even if a few of the sampling holes  14  are in contact with liquids, the gas sample will continue to flow through the open holes. This is due to the fact that the relatively small sampling holes have a greater resistance to liquids than to the sampled breath. Preferably, the gas sampling catheter  11  is formed of a hydrophobic material, and is therefore less prone to blockage of the sampling holes  14 . 
         [0028]    The diameter of the sampling holes  14  and the longitudinal distance between them are preferably determined according to the width of internal bore  16  and to the flow rate within the passageway through which the sample is taken. According to one preferred configuration of the sampling catheter  11 , five sampling holes  14 , each of a diameter in the range of 0.3-0.8 mm are disposed within a 4 cm-long sampling portion  12 . Alternatively, a longer sampling portion  12  may be provided. 
         [0029]    The sampling catheter  11  preferably has a narrow overall diameter and a narrow internal bore  16 . For adult-sized use, the internal bore  16  is preferably of the order of 1.0 mm, and for pediatric use, even less. The use of a catheter with such a narrow diameter is advantageous as it is readily filled by the sampled breath, creating a faster response time. Furthermore, it can be comfortably and easily inserted into the passageway from which the sample will be taken. Additionally, the internal diameter of the internal bore  16  is similar to that of the internal diameter of other capnographic sampling systems which are in common use, thus ensuring a smooth flow of the sampled gas from the sampling catheter to the sampling system. 
         [0030]    Sampling catheter  11  preferably includes a sealed and rounded end  18 , sealing sampling portion  12 . This structure facilitates insertion of sampling catheter  11  without scratching the tissues of the internal walls of the subject&#39;s passageways. 
         [0031]    A top end  20  of the sampling catheter  11  is preferably fitted with a connector  22 , which is adapted for attaching the sampling catheter  11  to a capnographic gas analyzer  24 , such as Microcap® commercially available from Oridion Medical LTD. of Jerusalem, Israel, typically by means of standard sampling tubing. 
         [0032]    A T-piece arrangement  26  may also be preferably provided at the top end  20  of the sampling catheter  11 , to facilitate the pumping out of any liquids which may accumulate within the sampling catheter  11 . T-piece arrangement  26  preferably enables connection of the catheter to a pumping system  28 . 
         [0033]    When using the sampling catheter  11 , it is inserted into the nasal or oral orifice of a subject, and is pushed in preferably until the sampling portion  12  is located at least at the posterior pharynx of the subject, or further down the respiratory tract. At this location of the sampling catheter  11 , the sampling is not sensitive to changes in the exhaled breath concentrations resulting from alternating oral and nasal breathing, and therefore the sampling is more accurate. 
         [0034]    Preferably, longitudinal markings  30  are provided on an outer wall of the sampling catheter  11 , allowing medical personnel inserting the catheter to determine the depth of catheter penetration. 
         [0035]    Reference is now made to  FIG. 2 , which is a schematic illustration of a capnographic sampling system constructed and operative in accordance with another preferred embodiment of the present invention and to  FIGS. 3A and 3B , which are sectional illustrations taken along respective section lines IIIA-IIIA and IIIB-IIIB thereof. 
         [0036]    Capnographic system  40  includes a sampling catheter  41  having a sampling portion  42 , which is preferably located at a lower end  43  of sampling catheter  41 . A number of sampling holes  44  are formed in the wall of the sampling catheter  41 , preferably within the sampling portion  42 . Sampling catheter  41  additionally includes an internal bore  46 , forming a passageway for the sampled fluid. 
         [0037]    Sampling holes  44  are preferably arranged at different longitudinal positions along the length of sampling catheter  41  and at different circumferential positions therearound. A preferred pattern for the location of the sampling holes  44  is in the form of a helix. Additionally, at least two circumferential protrusions  47  are preferably formed on sampling catheter  41  at two restricting ends of sampling portion  42 . More preferably, an additional circumferential protrusion  47  is formed in the middle of sampling portion  42 , between sampling holes  44 . The circumferential protrusions  47  distance the sampling holes  44  from a wall of the passageway into which the sampling catheter  41  has been inserted, such that even in the case of engagement between the sampling catheter  41  and the walls of the passageway all the sampling holes  44  remain open. 
         [0038]    Additionally, the use of several sampling holes  44  ensures that even if a few of the sampling holes  44  are in contact with liquids, the gas sample will continue to flow through the open holes. This is due to the fact that the relatively small sampling holes have a greater resistance to liquids than to the sampled breath. Preferably, the gas sampling catheter  41  is formed of a hydrophobic material, and is therefore less prone to blockage of the sampling holes  44 . 
         [0039]    The diameter of the sampling holes  44  and the longitudinal distance between them are preferably determined according to the width of internal bore  46  and to the flow rate within the passageway from which the sample is taken. According to one preferred configuration of the sampling catheter  41 , five sampling holes  44 , each of a diameter in the range of 0.3-0.8 mm are disposed within a 4 cm-long sampling portion  42 . Alternatively, a longer sampling portion  42  may be provided. The sampling catheter  41  preferably has a narrow overall diameter and a narrow internal bore  46 . For adult-sized use, the internal bore  46  is preferably of the order of 1.0 mm, and for pediatric use, even less. The use of a catheter with such a narrow diameter is advantageous as it is readily filled by the sampled breath creating a faster response time. Furthermore, it can be comfortably and easily inserted into the passageway from which the sample will be taken. Additionally, the internal diameter of the internal bore  46  is similar to that of the internal diameter of other capnographic sampling systems which are in common use, thus ensuring a smooth flow of the sampled gas from the sampling catheter to the sampling system. 
         [0040]    Sampling catheter  41  preferably includes a sealed and rounded end  48 , sealing sampling portion  42 . This structure facilitates insertion of sampling catheter  41  without scratching the tissues of the internal walls of the subject&#39;s passageways. 
         [0041]    A top end  50  of the sampling catheter  41  is preferably fitted with a connector  52 , which is adapted for attaching the sampling catheter  41  to a capnographic gas analyzer  54 , such as Microcap® commercially available from Oridion Medical LTD. of Jerusalem, Israel, typically by means of standard sampling tubing. 
         [0042]    A T-piece arrangement  56  may also be preferably provided at the top end  50  of the sampling catheter  41 , to facilitate the pumping out of any liquids which may accumulate within the sampling catheter  41 . T-piece arrangement  56  preferably enables connection of the catheter to a pumping system  58 . 
         [0043]    When using the sampling catheter  41 , it is inserted into the nasal or oral orifice of a subject, and is pushed in preferably until the sampling portion  42  is located at least at the posterior pharynx of the subject, or further down the respiratory tract. At this location of the sampling catheter  41 , the sampling is not sensitive to changes in the exhaled breath concentrations resulting from alternating oral and nasal breathing, and therefore the sample is more accurate. 
         [0044]    Preferably, longitudinal markings  60  are provided on an outer wall of the sampling catheter  41 , allowing medical personnel inserting the catheter to determine the depth of catheter penetration. 
         [0045]    An essential difference between the embodiment of  FIG. 1  and that of  FIGS. 2-3B  is that the sampling holes on the sampling catheter cannot be blocked by engagement with the walls of the passageway into which the catheter is inserted due to the circumferential protrusions distancing the sampling holes from the passageway wall. 
         [0046]    Reference is now made to  FIG. 4 , which is a schematic illustration of a capnographic sampling system constructed and operative in accordance with yet another preferred embodiment of the present invention. 
         [0047]    Capnographic system  70  includes a sampling catheter  71  having a sampling portion  72 , which is preferably located at a lower end  73  of sampling catheter  71 . A number of sampling holes  74  are formed in the wall of the sampling catheter  71 , preferably within the sampling portion  72 . Sampling catheter  71  additionally includes an internal bore  76 , forming a passageway for the sampled fluid. 
         [0048]    Sampling holes  74  are preferably arranged at different longitudinal positions along the length of sampling catheter  71  and at different circumferential positions therearound. A preferred pattern for the location of the sampling holes  74  is in the form of a helix. This structure ensures that at least some of the sampling holes  74  remain open, even when one side of the catheter circumference is in contact with the passageway into which the sampling catheter  71  has been inserted. 
         [0049]    Additionally, the use of several sampling holes  74  ensures that even if a few of the sampling holes  74  are in contact with liquids, the gas sample will continue to flow through the open holes. This is due to the fact that the relatively small sampling holes have a greater resistance to liquids than to the sampled breath. Preferably, the gas sampling catheter  71  is formed of a hydrophobic material, and is therefore less prone to blockage of the sampling holes  74 . 
         [0050]    The diameter of the sampling holes  74  and the longitudinal distance between them are preferably determined according to the width of internal bore  76  and to the flow rate within the passageway from which the sample is taken. According to one preferred configuration of the sampling catheter  71 , five sampling holes  74 , each of a diameter in the range of 0.3-0.8 mm are disposed within a 4 cm-long sampling portion  72 . Alternatively, a longer sampling portion  72  may be provided. 
         [0051]    The sampling catheter  71  preferably has a narrow overall diameter and a narrow internal bore  76 . For adult-sized use, the internal bore  76  is preferably of the order of 1.0 mm, and for pediatric use, even less. The use of a catheter with such a narrow diameter is advantageous as it is readily filled by the sampled breath, creating a faster response time. Furthermore, it can be comfortably and easily inserted into the passageway from which the sample will be taken. Additionally, the internal diameter of the internal bore  76  is similar to that of the internal diameter of other capnographic sampling systems which are in common use, thus ensuring a smooth flow of the sampled gas from the sampling catheter to the sampling system. 
         [0052]    Sampling catheter  71  preferably includes a sealed and rounded end  78 , sealing sampling portion  72 . This structure facilitates insertion of sampling catheter  71  without scratching the tissues of the internal walls of the subject&#39;s passageways. 
         [0053]    A top end  80  of the sampling catheter  71  is preferably fitted with a connector  82 , which is adapted for attaching the sampling catheter  71  to a capnographic gas analyzer  84 , such as Microcap® commercially available from Oridion Medical LTD. of Jerusalem, Israel, typically by means of standard sampling tubing. 
         [0054]    A T-piece arrangement  86  may also be preferably provided at the top end  80  of the sampling catheter  71 , to facilitate the pumping out of any liquids which may accumulate within the sampling catheter  71 . T-piece arrangement  86  preferably enables connection of the catheter to a pumping system  88 . 
         [0055]    Sampling catheter  71  is preferably integrally formed with an oxygen delivery tube  90 , surrounding an internal lumen  92 , thereby forming a double-lumen structure with sampling catheter  71  as shown in the enlarged portion in  FIG. 4 . One end of oxygen delivery tube  90  is fitted with a connector  94 , adapted to connect the oxygen delivery tube  90  to an oxygen source  96 . Preferably, oxygen delivery tube  90  terminates at a point slightly higher than the beginning of sampling portion  72 , in order to prevent dilution of sampled breath during exhalation by oxygen emitted from the oxygen delivery tube  90 . Typically and preferably, the distance between the beginning of sampling portion  72  and the end of oxygen delivery tube  90 , indicated by the letter H, is 2 or more centimeters. 
         [0056]    When using the sampling catheter  71 , it is inserted into the nasal or oral orifice of a subject, and is pushed in preferably until the sampling portion  72  is located at least at the posterior pharynx of the subject, or further down the respiratory tract. At this location of the sampling catheter  71 , the sampling is not sensitive to changes in the exhaled breath concentrations resulting from alternating oral and nasal breathing, and thereby the sampling is more accurate. Moreover, this location of the sampling catheter  71  will ensure sufficient oxygen supply to the subject&#39;s respiratory tract through oxygen delivery tube  90 , which is also located at or near the posterior pharynx of the subject. 
         [0057]    Preferably, longitudinal markings  98  are provided on an outer wall of the sampling catheter  71 , allowing medical personnel inserting the catheter to determine the depth of catheter penetration. 
         [0058]    An essential advantage of the embodiment of  FIG. 4  is that the design is specifically suitable for sedated yet spontaneously breathing patients. 
         [0059]    It is appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention includes both combinations and subcombinations of various features described hereinabove as well as variations and modifications thereto which would occur to a person of skill in the art upon reading the above description and which are not in the prior art.