Abstract:
According to a preferred embodiment of the present invention there is provided a bite block assembly adapted for capnography and oxygen delivery to a subject, the bite block assembly ( 50 ) including a first capnography passageway adapted for passage therethrough of exhaled breath from the subject to a capnograph and a second oxygen delivery passageway, separate from the first passageway, adapted for passage therethrough of oxygen from an oxygen source to the mouth of the subject.

Description:
REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to PCT Patent Application PCT/IL2004/000430, filed May 20, 2004, entitled “ENDOSCOPIC BITE BLOCK”, the disclosure of which is hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of bite blocks for endoscopic use and specifically to endoscopic bite blocks suitable for use with gas sampling or delivery cannulae. 
       BACKGROUND OF THE INVENTION 
       [0003]    The following U.S. Patents are believed to represent the current state of the art: U.S. Pat. Nos. 5,174,284; 6,257,238; 6,422,240; 5,273,032 and 5,513,634. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention seeks to provide a new endoscopic bite block. 
         [0005]    There is thus provided in accordance with a preferred embodiment of the present invention a bite block assembly adapted for capnography and oxygen delivery to a subject, the bite block assembly including a first capnography passageway adapted for passage therethrough of exhaled breath from the subject to a capnograph, and a second oxygen delivery passageway, separate from the first passageway, adapted for passage therethrough of oxygen from an oxygen source to the mouth of the subject. 
         [0006]    Preferably the bite block assembly also includes a gas collection cannula having formed therein the first capnography passageway. Additionally the gas collection cannula also includes an oxygen delivery cannula adapted to deliver oxygen from the oxygen source to the nostrils of the subject. More preferably the oxygen delivery cannula is connected to the oxygen source by a gas delivery tube. 
         [0007]    Preferably the bite block assembly also includes a bite block having formed therein the second oxygen delivery passageway. 
         [0008]    More preferably the bite block assembly also includes a tube element adapted to connect the oxygen delivery cannula to the second oxygen delivery passageway. Additionally, the tube element includes a branch of the gas delivery tube, and is adapted to connect to the second oxygen delivery passageway. Additionally the tube element is sealed by a normally closed valve. Preferably the normally closed valve includes a luer valve. Additionally a mating luer portion of the luer valve is mounted onto the oxygen delivery passageway. 
         [0009]    Preferably the tube element is permanently mounted onto the bite block and is adapted to connect to the gas delivery tube at a connection point formed therein. Additionally the connection point is sealed by a normally closed valve. Preferably the normally closed valve includes a luer valve. More preferably a mating luer portion of the luer valve is mounted onto the tube element. 
         [0010]    There is thus provided in accordance with another preferred embodiment of the present invention, a capnography system including a capnograph, a bite block adapted to maintain the mouth of a subject open during a medical procedure, an exhaled breath sampling element which is connectable to the capnograph and mountable onto the bite block, and an oral oxygen delivery passageway which is connectable to the bite block for delivering oxygen from an oxygen source to the mouth of the subject. 
         [0011]    Preferably the exhaled breath-sampling element has at least one gas collection passageway, formed therein, the gas collection passageway being configured to collect exhaled breath of the subject. Additionally the at least one gas collection passageway includes a nasal gas collection passageway configured for collecting breath exhaled through at least one nostril of the subject. Additionally or alternatively the at least one gas collection passageway includes an oral gas collection passageway configured for collecting breath exhaled through the mouth of the subject. 
         [0012]    Preferably the capnography system also includes a nasal gas delivery passageway for delivering oxygen from the oxygen source to at least one nostril of the subject. Additionally the nasal gas delivery passageway is connected to the oxygen source by a gas delivery tube. More preferably the oral oxygen delivery passageway includes a tubular branch of the gas delivery tube. 
         [0013]    Preferably the oral oxygen delivery passageway is sealed by a normally closed valve. Additionally the normally closed valve includes a luer valve. More preferably a mating luer portion of the luer valve is mounted onto the oral oxygen delivery passageway. 
         [0014]    Preferably the oral oxygen delivery passageway is permanently mounted onto the bite block and is adapted to connect to the gas delivery tube at a connection point formed therein. Additionally the connection point is sealed by a normally closed valve. More preferably the normally closed valve includes a luer valve. Additionally a mating luer portion of the luer valve is mounted onto the oral oxygen delivery passageway. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
           [0016]      FIGS. 1A and 1B  are simplified pictorial illustrations of an oral nasal sampling cannula forming part of an endoscopic bite block assembly, constructed and operative in accordance with a preferred embodiment of the present invention, in retracted and extended orientations respectively; 
           [0017]      FIGS. 2A and 2B  are front-view and rear-view simplified pictorial illustrations of an endoscopic bite block forming part of an endoscopic bite block assembly, constructed and operative in accordance with a preferred embodiment of the present invention; 
           [0018]      FIG. 3  is a simplified sectional pictorial illustration of the endoscopic bite block of  FIGS. 2A and 2B , taken along sections lines in  FIG. 2B ; 
           [0019]      FIG. 4  is a simplified schematic illustration of the connection between the oral nasal cannula of  FIGS. 1A and 1B  and the endoscopic bite block of  FIGS. 2A-3 ; 
           [0020]      FIGS. 5A, 5B, 5C, 5D, 5E, 5F and 5G  are pictorial illustrations of various stages of typical use of the endoscopic bite block assembly of  FIGS. 1A-4 ; 
           [0021]      FIGS. 6A and 6B  are simplified pictorial illustrations of an oral nasal cannula forming part of an endoscopic bite block assembly, constructed and operative in accordance with another preferred embodiment of the present invention, in retracted and extended orientations respectively; 
           [0022]      FIGS. 7A and 7B  are front-view and rear-view simplified pictorial illustrations of an endoscopic bite block forming part of an endoscopic bite block assembly, constructed and operative in accordance with another preferred embodiment of the present invention; 
           [0023]      FIG. 8  is a simplified sectional pictorial illustration of the endoscopic bite block of  FIGS. 7A and 7B , taken along sections lines VIII-VIII in  FIG. 7B ; 
           [0024]      FIG. 9  is a simplified schematic illustration of the connection between the oral nasal cannula of  FIGS. 6A and 6B  and the endoscopic bite block of  FIGS. 7A-8 ; 
           [0025]      FIGS. 10A, 10B, 10C, 10D, 10E, 10F and 10G  are pictorial illustrations of various stages of typical use of the endoscopic bite block assembly of  FIGS. 5A-9 ; 
           [0026]      FIGS. 11A and 11B  are simplified pictorial illustrations of an oral nasal cannula forming part of an endoscopic bite block assembly, constructed and operative in accordance with yet another preferred embodiment of the present invention, in retracted and extended orientations respectively; 
           [0027]      FIGS. 12A and 12B  are front-view and rear-view simplified pictorial illustrations of an endoscopic bite block forming part of an endoscopic bite block assembly, constructed and operative in accordance with yet another preferred embodiment of the present invention; 
           [0028]      FIG. 13  is a simplified sectional pictorial illustration of the endoscopic bite block of  FIGS. 12A and 12B , taken along sections lines XIII-XIII in  FIG. 12B ; 
           [0029]      FIG. 14  is a simplified schematic illustration of the connection between the oral nasal cannula of  FIGS. 11A and 11B  and the endoscopic bite block of  FIGS. 12A-13 ; and 
           [0030]      FIGS. 15A, 15B, 15C, 15D, 15E, 15F and 15G  are pictorial illustrations of various stages of typical use of the endoscopic bite block assembly of  FIGS. 11A-14 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0031]    A bite block is a device commonly used during upper gastro-intestinal endoscopic procedures to facilitate passage of an esophago-gastro-duodenoscopy (EGD) endoscope. The purpose of the bite block is to allow the physician to perform the procedure without the subject interfering by biting and damaging the endoscope tubing inserted via his mouth, whether voluntarily or involuntarily. 
         [0032]    The upper gastro-intestinal endoscopic procedure itself, together with the use of a bite block, is often highly uncomfortable for the subject and therefore it is very common for the subject to be sedated during the procedure. Despite this, it is common for the subject to show opposition to the procedure. 
         [0033]    During upper gastro-intestinal endoscopy, and especially during long duration procedures performed under sedation, CO2 monitoring is often performed using a separate nasal or oral/nasal cannula in conjunction with a bite block. Concomitant use of bite blocks and cannulae may noticeably affect capnographic performance for a number of reasons, including inter alia misalignment between the cannula and the bite block and inefficient oral sampling due to the space taken up by the endoscope. The present invention provides a solution that generally does not affect the capnographic performance. 
         [0034]    Reference is now made to  FIGS. 1A and 1B , which are simplified pictorial illustrations of an oral nasal sampling cannula forming part of an endoscopic bite block assembly, constructed and operative in accordance with a preferred embodiment of the present invention, in retracted and extended orientations respectively. 
         [0035]      FIGS. 1A and 1B  show an oral nasal sampling cannula  10 , which is adapted for collection of gases, such as carbon dioxide, exhaled by a subject, and for supplying oxygen to the subject. 
         [0036]    The oral nasal sampling cannula  10  comprises a main body portion  12 , having formed therein an exhaled breath collection bore  14  and an oxygen delivery bore  16 . A pair of hollow nasal prongs  18 , which are adapted for insertion into the nostrils of the subject, is integrally formed with the main body portion  12 . A hollow oral prong  22 , which is formed with a limiting rib  23  and a cut-away tip  24 , is mounted onto a bottom surface of main body portion  12 . An oral breath directing element  26 , which is preferably in the shape of a cut-away tube, is slidably mounted onto oral prong  22  by a mounting portion  28 , and positioning of the oral breath directing element  26  is limited by the limiting rib  23  of oral prong  22 . 
         [0037]    A channel formed in oral prong  22  is in fluid flow connection with channels formed in nasal prongs  18 , thereby forming a single junction  32 . Single junction  32  is in fluid flow communication with exhaled breath collection bore  14 , which in turn is in fluid flow communication with an exhaled breath collection tube  34 , which is adapted to be connected to a breath test analyzer or a capnograph (not shown), such as Microcap® which is commercially available from Oridion Medical LTD. of Jerusalem, Israel. 
         [0038]    Main body portion  12  is formed with oxygen delivery openings  36 , which are in fluid flow communication with oxygen delivery bore  16 , which in turn is in fluid flow communication with an oxygen delivery tube  38 . Alternatively, at least one nasal oxygen delivery prong, adapted for insertion into the subject&#39;s nostril, may be used instead of oxygen delivery openings  36 . Oxygen delivery tube  38  is adapted to be connected to a source of oxygen (not shown). 
         [0039]    Oxygen delivery tube  38  and exhaled breath collection tube  34  may optionally be placed around the ears of the subject, thereby stabilizing the oral nasal sampling cannula  10  on the subject&#39;s face, such that any movement of the subject will have a negligible effect on the placement of the oral nasal sampling cannula  10 . 
         [0040]    It is appreciated that oral breath directing element  26  may be in a retracted orientation as shown in  FIG. 1A , or in an extended orientation as shown in  FIG. 1B , thereby allowing the oral nasal sampling cannula  10  to be suited to the facial dimensions of the subject, resulting in more efficient collection of exhaled breath. 
         [0041]    Reference is now made to  FIGS. 2A and 2B , which are front-view and rear-view simplified pictorial illustrations of an endoscopic bite block forming part of an endoscopic bite block assembly constructed and operative in accordance with a preferred embodiment of the present invention and to  FIG. 3 , which is a simplified sectional pictorial illustration thereof. 
         [0042]      FIGS. 2A, 2B and 3  show an endoscopic bite block  50 , which is adapted to be inserted into the mouth of a subject while the subject is sedated, to ensure that the mouth of the subject is maintained open during the endoscopy process and that the subject does not interfere with the process by biting on the medical instruments used. 
         [0043]    The endoscopic bite block  50  includes a main body portion  52 , having formed therein a central opening  54 . A hollow tubular portion  56  extends distally from main body portion  52 , such that the opening of tubular portion  56  is an extension of central opening  54 . Central opening  54  is of a first height, indicated by H 1  in  FIG. 3 , which is typically 16 to 20 mm in bite blocks for adult use, which is the height required by medical personnel for performing an endoscopy. In order to ensure that during breath sampling, oral prong  22  of oral nasal sampling cannula  10  ( FIGS. 1A and 1B ) does not interfere with the space required by medical personnel for performing the endoscopy procedure, the height of tubular portion  56  is greater than the height H 1  of the central opening  54  as indicated by H 2  in  FIG. 3 , and is typically 2 to 4 mm more than height H 1  (18 to 24 mm). 
         [0044]    An outer surface  58  of tubular portion  56  is formed with top and bottom teeth engagement surfaces  60  and  62 , such that top teeth engagement surface  60  is relatively forward of bottom teeth engagement surface  62 . This structure facilitates easy and accurate biting of the bite block  50  by a subject, as it is suited to the jaw morphology of a closed human mouth. Surface  58  is additionally formed with jaw engagement recesses  64 , which are formed forwardly of teeth engagement surfaces  60  and  62 , respectively. 
         [0045]    A top inner surface  70  of main body portion  52  is formed with a longitudinal groove  72  having a transverse surface  73 , which is adapted to accommodate oral prong  22  and oral breath directing element  26  of the oral nasal sampling cannula  10  ( FIGS. 1A and 1B ), as described with more detail herein below with reference to  FIG. 4 . 
         [0046]    A flexible barrier  76 , preferably comprised of several flaps  78 , is disposed within central opening  54 , thereby substantially closing off the central opening and preventing dilution of exhaled breath by ambient air during sampling. An opening  80  is preferably maintained within flexible barrier  76 , thereby ensuring a small part of central opening  54  remains open in order to enable the subject to inhale external air. The flexible barrier  76  ensures that a majority of the subject&#39;s orally exhaled breath will be directed toward oral prong  22  ( FIGS. 1A and 1B ) thereby ensuring accurate sampling of the subject&#39;s breath. Opening  80  is preferably placed at a top part of central opening  54  near the cut-away tip  24  of oral prong  22  ( FIGS. 1A and 1B ), thereby directing exhaled breath toward the oral prong  22  as it is the only substantial exit. 
         [0047]    The flaps  78  are preferably formed of a plastic material selected to be of suitable thickness to maintain their position when undisturbed, yet bend readily when pushed by an endoscope probe, and thus do not limit the actions of the medical personnel performing the endoscopy. However, the flaps  78  preferably close back around the endoscope probe, thus maintaining a substantially closed oral cavity volume and allowing most of the exchange of gases to occur close to the opening  80  of the flexible barrier  76  which is close to the cut-away tip  24  of oral prong  22  ( FIGS. 1A and 1B ) from which capnographic sampling can be performed accurately. Additionally, the flaps  78  are preferably transparent, thus enabling medical personnel to see into the oral cavity during the endoscopy procedure. 
         [0048]    Two attachment surfaces  82 , each formed with a slit  84 , extend horizontally outwardly from main body portion  52 . Slits  84  are adapted to connect to a band which is placed around the subject&#39;s head and is used to maintain the endoscopic bite block  50  firmly in position during the endoscopy procedure. Preferably, slits  84  are located above a horizontal centerline of main body portion  52 , such that the connected band will tend to exert a stronger pull to the top of the main body portion  52 , thus assisting in overcoming the subject&#39;s tendency to tilt the bite block  50  outward during the endoscopy procedure and in maintaining the bite block  50  upright in the subject&#39;s mouth. 
         [0049]    Reference is now made to  FIG. 4 , which is a simplified schematic illustration of the connection between the oral nasal sampling cannula of  FIGS. 1A and 1B  and the endoscopic bite block of  FIGS. 2A-3 . 
         [0050]    As seen in  FIG. 4 , oral prong  22  of oral nasal sampling cannula  10  is accommodated within groove  72  of bite block  50 , such that a bottom surface of oral breath directing element  26  engages transverse surface  73  of the groove  72 . It is appreciated that transverse surface  73  is located below an inner surface of tubular portion  56  in order to ensure that air exhaled by the subject into tubular portion  56  will be directed toward groove  72  and oral prong  22 . 
         [0051]    Reference is now made to  FIGS. 5A, 5B, 5C, 5D, 5E, 5F and 5G , which are pictorial illustrations of various stages of typical use of the endoscopic bite block assembly of  FIGS. 1A-4 . 
         [0052]    As seen in  FIG. 5A , the nasal prongs  18  of the oral nasal sampling cannula  10  are placed in the subjects nostrils, preferably before the subject is sedated. Preferably, the exhaled breath collection tube  34  and the oxygen delivery tube  38  are placed around the subject&#39;s ears, in order to ensure the stability of the oral nasal sampling cannula  10  on the subject&#39;s face. As seen in the enlarged portion of  FIG. 5A , at this stage the oral breath-directing element  26  is in its retracted orientation, indicated by the length H 3 . 
         [0053]    Turning to  FIG. 5B , it is seen that the oral breath directing element  26  is extended to accommodate the facial dimensions of the subject, revealing part of oral prong  22 . Preferably, the oral breath-directing element is moved down to a point in which a bottom end thereof is at the height of the top of the bottom lip of the subject, its new length being indicated by H 4 . This action is preferably preformed by medical personnel, but may alternatively be performed by the subject himself, a family member, or any other person. 
         [0054]      FIG. 5C  illustrates the insertion of bite block  50  into the mouth of the subject, such that main body portion  52  engages the outer surface of the subject&#39;s lips and the tubular portion  56  is inside the subject&#39;s mouth. A strap, indicated by reference numeral  90 , is attached to slits  84  of attachment surfaces  82  and is placed around the subject&#39;s head, thereby securing the bite block  50  in place. This stage is preferably performed when the subject is sedated, but may alternatively be performed prior thereto. 
         [0055]    As seen in the enlarged portion of  FIG. 5C , the oral breath directing element  26  and the oral prong  22  are accommodated in groove  72 , such that a bottom surface of the oral breath directing element  26  engages transverse surface  73  of groove  72 . Additionally, if oral breath directing element  26  has been extended more than necessary for the facial features of the subject, the transverse surface  73  pushes the oral breath-directing element  26  back, until it is optimally positioned. The lips of the subject, indicated by reference numeral  92  preferably engage jaw engagement recesses  64 , and the top and bottom teeth of the subject, indicated by reference numerals  94  and  96  engage top and bottom teeth engagement surfaces  60  and  62 , respectively. 
         [0056]    Turning to  FIG. 5D , it is seen that air exhaled orally by the subject, indicated by arrows, passes through the bore of tubular portion  56 , and is directed toward oral breath directing element  26  and oral prong  22  by the flaps  78  of flexible barrier  76 . Air that is exhaled nasally by the subject passes through nasal prongs  18 . 
         [0057]      FIG. 5E  illustrates the sedated subject, having the nasal prongs  18  of the oral nasal sampling cannula  10  in his nostrils and the endoscopic bite block  50  placed in his mouth and strapped to his head. Preferably, once the subject is sedated, oxygen is supplied to the nose of the subject via oxygen delivery openings  36  of oral nasal sampling cannula  10 , as indicated by arrows in the enlarged portion of  FIG. 5E . The oxygen is supplied to oxygen delivery openings  36  via oxygen delivery bore  16  ( FIGS. 1A and 1B ) and oxygen delivery tube  38 . 
         [0058]    Turning to  FIG. 5F , it is seen that when the subject is sedated, he tends to move or slump his head, thereby moving oral nasal sampling cannula  10  relative to bite block  50 , as indicated by angle a in the enlarged portion of  FIG. 5F . The feature of the present invention which provides oral nasal sampling cannula  10  which is physically separated from bite block  50  and the placement of oral breath directing element  26  and oral prong  22  within groove  72 , ensure that even when the subject moves or slumps his head, the oral prong  22  and nasal prongs  18  will be maintained in their respective places, and accurate sampling will continue. Additionally, the placement of oral prong  22  within groove  72  provides a counter force to force applied by the subject&#39;s tongue to push at least the top portion of the bite block  50  out of the subject&#39;s mouth, thus ensuring accurate placement of the bite block. 
         [0059]    As seen in  FIG. 5G , an endoscope probe  98  is inserted into the bore of tubular portion  56  of bite block  50 , for performing an endoscopy procedure. During the insertion of endoscope probe  98  and its presence in the subject&#39;s mouth and pharynx, flaps  78  of flexible barrier  76  bend slightly inward to allow the passage of the endoscope probe  98 , as seen with particular clarity in the enlarged portion of  FIG. 5G . However, the central opening  54  of bite block  50  remains substantially closed by flaps  78 , thereby separating the exhaled breath of the subject which is in the bore of tubular portion  56  from the ambient air. 
         [0060]    Additionally, the sampling may continue during the presence of the endoscope probe  98  in the pharynx of the subject, as the tubular portion  56  is of a slightly larger diameter than the central opening  54 , thereby ensuring that medical personnel have the space required for the endoscopy procedure and sampling can take place from the space defined by the difference between heights H 2  and H 1  ( FIG. 3 ), as indicated by arrows in the enlarged portion of  FIG. 5G . 
         [0061]    It is appreciated that following the endoscopy, the bite block  50  may be removed from the subject&#39;s mouth, preferably by medical personnel. However, the sampling of exhaled breath through nasal prongs  18  which remain in the subject&#39;s nostrils and through oral prong  22  which remains near the subject&#39;s mouth, preferably continues until the subject has awaken from the sedation. This is necessary because the subject&#39;s breath must be monitored as long as the subject is sedated. 
         [0062]    Reference is now made to  FIGS. 6A and 6B , which are simplified pictorial illustrations of an oral nasal sampling cannula forming part of an endoscopic bite block assembly, constructed and operative in accordance with another preferred embodiment of the present invention, in retracted and extended orientations respectively. 
         [0063]      FIGS. 6A and 6B  show an oral nasal sampling cannula  110 , which is adapted for collection of gases, such as carbon dioxide, exhaled by a subject, and for supplying oxygen to the subject. 
         [0064]    The oral nasal sampling cannula  110  comprises a main body portion  112 , having formed therein an exhaled breath collection bore  114  and an oxygen delivery bore  116 . A pair of hollow nasal prongs  118 , which are adapted for insertion into the nostrils of the subject, is integrally formed with the main body portion  112 . A hollow oral prong  122 , which is formed with a limiting rib  123  and a cut-away tip  124 , is mounted onto a bottom surface of main body portion  112 . An oral breath directing element  126 , which is preferably in the shape of a cut-away tube, is slidably mounted onto oral prong  122  by a mounting portion  128 , and positioning of the oral breath directing element  126  is limited by the limiting rib  123  of oral prong  122 . 
         [0065]    A channel formed in oral prong  122  is in fluid flow connection with channels formed in nasal prongs  118 , thereby forming a single junction  132 . Single junction  132  is in fluid flow communication with exhaled breath collection bore  114 , which in turn is in fluid flow communication with an exhaled breath collection tube  134 , which is adapted to be connected to a breath test analyzer or a capnograph (not shown), such as Microcap® which is commercially available from Oridion Medical LTD. of Jerusalem, Israel. 
         [0066]    Main body portion  112  is formed with oxygen delivery openings  136 , which are in fluid flow communication with oxygen delivery bore  116 , which in turn is in fluid flow communication with an oxygen delivery tube  138 . Alternatively, at least one nasal oxygen delivery prong, which is adapted to be inserted into the nostril of the subject, may be used instead of oxygen delivery openings  136 . Oxygen delivery tube  138  is preferably formed with a T-element  140 , connecting the oxygen delivery tube  138  to an oral oxygen delivery tube  142 . Oxygen delivery tube  138  is adapted to be connected to a source of oxygen (not shown). Oral oxygen delivery tube  142  is preferably normally closed by a valve element  144 . Typically, the valve is a luer type valve. 
         [0067]    Oxygen delivery tube  138  and exhaled breath collection tube  134  may optionally be placed around the ears of the subject, thereby stabilizing the oral nasal sampling cannula  110  on the subject&#39;s face, such that any movement of the subject will have negligible effect on the placement of the oral nasal sampling cannula  110 . 
         [0068]    It is appreciated that oral breath directing element  126  may be in a retracted orientation as shown in  FIG. 6A , or in an extended orientation as shown in  FIG. 6B , thereby allowing the oral nasal sampling cannula  110  to be suited to the facial dimensions of the subject, resulting in more efficient collection of exhaled breath. 
         [0069]    Reference is now made to  FIGS. 7A and 7B , which are front-view and rear-view simplified pictorial illustrations of an endoscopic bite block forming part of an endoscopic bite block assembly constructed and operative in accordance with a preferred embodiment of the present invention and to  FIG. 8 , which is a simplified sectional pictorial illustration thereof. 
         [0070]      FIGS. 7A, 7B and 8  show an endoscopic bite block  150 , which is adapted to be inserted into the mouth of a subject while the subject is sedated, to ensure that the mouth of the subject is maintained open during the endoscopy process and that the subject does not interfere with the process by biting on the medical instruments used. 
         [0071]    The endoscopic bite block  150  includes a main body portion  152 , having formed therein a central opening  154 . A hollow tubular portion  156  extends distally from main body portion  152 , such that the opening of tubular portion  156  is an extension of central opening  154 . Central opening  154  is of a first height, indicated by H 1  in  FIG. 8 , which is typically 16 to 20 mm in bite blocks for adult use, which is the height required by medical personnel for performing an endoscopy. In order to ensure that during breath sampling, oral prong  122  of oral nasal sampling cannula  110  ( FIGS. 6A and 6B ) does not interfere with the space required by medical personnel for performing the endoscopy procedure, the height of tubular portion  156  is greater than the height H 1  of central opening  154  as indicated by H 2  in  FIG. 8 , and is typically 2 to 4 mm more than height H 1  (18 to 24 mm). 
         [0072]    An outer surface  158  of tubular portion  156  is formed with top and bottom teeth engagement surfaces  160  and  162 , such that top teeth engagement surface  160  is relatively forward of bottom teeth engagement surface  162 . This structure facilitates easy and accurate biting of the bite block  150  by a subject, as it is suited to the jaw morphology of a closed human mouth. Surface  158  is additionally formed with jaw engagement recesses  164 , which are formed forwardly of teeth engagement surfaces  160  and  162 , respectively. 
         [0073]    A top inner surface  170  of main body portion  152  is formed with a longitudinal groove  172  having a transverse surface  173 , which is adapted to accommodate oral prong  122  and oral breath directing element  126  of the oral nasal sampling cannula  110  ( FIGS. 6A and 6B ), as described with more detail hereinbelow with reference to  FIG. 9 . 
         [0074]    A tubular portion  174  is formed on a side of outer surface  158  of tubular portion  156 . Tubular portion  174  is adapted to threadably engage oral oxygen delivery tube  142  ( FIGS. 6A and 6B ), thereby opening valve  144  to the passage of gases and thus supplying oxygen directly to the oral cavity of the subject. Preferably, tubular portion  174  includes a luer portion corresponding to luer valve element  144 . It is appreciated that tubular portion  174  is formed on outer surface  158  of tubular portion  156 , in order to ensure that the oral oxygen delivery does not interfere with the procedure performed by the medical personnel and so that the oxygen flow does not directly interfere with the CO2 sampling. 
         [0075]    A flexible barrier  176 , preferably comprised of several flaps  178 , is disposed within central opening  154 , thereby substantially closing off the central opening and preventing dilution of exhaled breath by ambient air during sampling. An opening  180  is preferably maintained within flexible barrier  176 , thereby ensuring a small part of central opening  154  to remain open in order to enable the subject to inhale external air. The flexible barrier  176  ensures that a majority of the subject&#39;s orally exhaled breath will be directed toward oral prong  122  ( FIGS. 6A and 6B ) thereby ensuring accurate sampling of the subject&#39;s breath. Opening  180  is preferably placed at a top part of central opening  154  near the cut-away tip  124  of oral prong  122  ( FIGS. 6A and 6B ), thereby directing exhaled breath toward the oral prong  122  as it is the only substantial exit. 
         [0076]    The flaps  178  are preferably formed of a plastic material selected to be of suitable thickness to maintain their position when undisturbed, yet bend readily when pushed by an endoscope probe, and thus do not limit the actions of the medical personnel performing the endoscopy. However, the flaps  178  preferably close back around the endoscope probe, thus maintaining a substantially closed oral cavity volume, and allowing most of the exchange of gases to occur close to the opening  180  of the flexible barrier  176 , which opening is close to the cut-away tip  124  of oral prong  122  from which capnographic sampling can be performed accurately. Additionally, the flaps  178  are preferably transparent, thus enabling medical personnel to see into the oral cavity during the endoscopy procedure. 
         [0077]    Two attachment surfaces  182 , each formed with a slit  184 , extend horizontally outwardly from main body portion  152 . Slits  184  are adapted to connect to a band which is place around the subject&#39;s head and is used to maintain the endoscopic bite block  150  firmly in position during the endoscopy procedure. Preferably, slits  184  are located above a horizontal centerline of main body portion  152 , such that the connected band will tend to exert a stronger pull to the top of the main body portion  152 , thus assisting in overcoming the subject&#39;s tendency to tilt the bite block  150  outward during the endoscopy procedure and in maintaining the bite block  150  upright in the subject&#39;s mouth. 
         [0078]    Reference is now made to  FIG. 9 , which is a simplified schematic illustration of the connection between the oral nasal sampling cannula of  FIGS. 6A and 6B  and the endoscopic bite block of  FIGS. 7A-8 . 
         [0079]    As seen in  FIG. 9 , oral prong  122  of oral nasal sampling cannula  110  is accommodated within groove  172  of bite block  150 , such that a bottom surface of oral breath directing element  126  engages transverse surface  173  of the groove  172 . It is appreciated that transverse surface  173  is located below an inner surface of tubular portion  156  in order to ensure that air exhaled by the subject into tubular portion  156  will be directed toward groove  172  and oral prong  122 . 
         [0080]    Additionally, valve  144  ( FIGS. 6A and 6B ) of oral oxygen delivery tube  142  is accommodated in tubular portion  174  of endoscopic bite block  150 , thereby opening the valve element and forming a fluid flow engagement between oxygen delivery tube  138  and tubular portion  174  of endoscopic bite block  150 , which is in fluid flow engagement with the oral cavity of the subject. 
         [0081]    Reference is now made to  FIGS. 10A, 10B, 10C, 10D, 10E, 10F and 10G , which are pictorial illustrations of various stages of typical use of the endoscopic bite block assembly of  FIGS. 6A-9 . 
         [0082]    As seen in  FIG. 10A , the nasal prongs  118  of the oral nasal sampling cannula  110  are placed in the subjects nostrils, preferably before the subject is sedated. Preferably, the exhaled breath collection tube  134  and the oxygen delivery tube  138  are placed around the subject&#39;s ears, in order to ensure the stability of the oral nasal sampling cannula  110  on the subject&#39;s face. As seen in the enlarged portion of  FIG. 10A , at this stage the oral breath-directing element  126  is in its retracted orientation, indicated by the length H 3 . At this stage, oral oxygen delivery tube  142  is not connected to the bite block  150  ( FIGS. 7A-8 ). 
         [0083]    Turning to  FIG. 10B , it is seen that the oral breath directing element  126  is extended to accommodate the facial dimensions of the subject, revealing part of oral prong  122 . Preferably, the oral breath-directing element is moved down to a point in which a bottom end thereof is at the height of the top of the bottom lip of the subject, its new length being indicated by H 4 . This action is preferably preformed by medical personnel, but may alternatively be performed by the subject himself, a family member, or any other person. 
         [0084]      FIG. 10C  illustrates the insertion of bite block  150  into the mouth of the subject, such that main body portion  152  engages the outer surface of the subject&#39;s lips and the tubular portion  156  ( FIGS. 7A-8 ) is inside the subject&#39;s mouth. Additionally, valve  144  of oral oxygen delivery tube  142  is inserted, preferably by medical personnel, into tubular portion  174  of endoscopic bite block  150 , as indicated by an arrow in the enlarged portion of  FIG. 10C , thereby opening the valve and allowing passage of fluids from the oral oxygen delivery tube  142  into the oral cavity of the subject. 
         [0085]    A strap, indicated by reference numeral  190 , is attached to slits  184  of attachment surfaces  182  and is placed around the subject&#39;s head, thereby securing the bite block  150  in place. This stage is preferably performed when the subject is sedated, but may alternatively be performed prior thereto. 
         [0086]    Turning to  FIG. 10D , it is seen that air exhaled orally by the subject, indicated by arrows, passes through the bore of tubular portion  156 , and is directed toward oral breath directing element  126  and oral prong  122  by the flaps  178  of flexible barrier  176 . Air that is exhaled nasally by the subject passes through nasal prongs  118 . 
         [0087]      FIG. 10D  illustrates the oral breath directing element  126  and the oral prong  122  being accommodated in groove  172 , such that a bottom surface of the oral breath directing element  126  engages transverse surface  173  of groove  172 . Additionally, if oral breath directing element  126  has been extended more than necessary for the facial features of the subject, the transverse surface  173  pushes the oral breath-directing element  126  back until it is optimally positioned. The lips of the subject, indicated by reference numeral  192  preferably engage jaw engagement recesses  164 , and the top and bottom teeth of the subject, indicated by reference numerals  194  and  196  engage top and bottom teeth engagement surfaces  160  and  162 , respectively. 
         [0088]      FIG. 10E  illustrates the sedated subject, having the nasal prongs  118  of the oral nasal sampling cannula  110  in his nostrils and the endoscopic bite block  150  placed in his mouth and strapped to his head. Preferably, once the subject is sedated, oxygen is supplied to the nose of the subject via oxygen delivery openings  136  of oral nasal sampling cannula  110 , and to the mouth of the subject via oral oxygen delivery tube  142  and tubular portion  174 , as indicated by arrows. The oxygen is supplied to the oxygen delivery openings  136  via oxygen delivery bore  116  ( FIGS. 6A and 6B ) and to oral oxygen delivery tube  142  via oxygen delivery tube  138  and T-element  140 . 
         [0089]    Turning to  FIG. 10F , it is seen that when the subject is sedated, he tends to move or slump his head, thereby moving oral nasal sampling cannula  110  relative to bite block  150 , as indicated by angle a in the enlarged portion of  FIG. 10F . The feature of the present invention which provides oral nasal sampling cannula  110  which is physically separated from bite block  150  and the placement of oral breath directing element  126  and oral prong  122  within groove  172 , ensure that even when the subject moves or slumps his head, the oral prong  122  and nasal prongs  118  will be maintained in their respective places, and accurate sampling will continue. Additionally, the placement of oral prong  122  within groove  172  provides a counter force to force applied by the subject&#39;s tongue to push at least the top portion of the bite block  150  out of the subject&#39;s mouth, thus ensuring accurate placement of the bite block. 
         [0090]    As seen in  FIG. 10G , an endoscope probe  198  is inserted into the bore of tubular portion  156  of bite block  150 , for performing the endoscopy procedure. During the insertion of endoscope probe  198  and its presence in the subject&#39;s mouth and pharynx, flaps  178  of flexible barrier  176  bend slightly inward to allow the passage of the endoscope probe  198 , as seen with particular clarity in the enlarged portion of  FIG. 10G . However, the central opening  154  of bite block  150  remains substantially closed by flaps  178 , thereby separating the exhaled breath of the subject which is in bore of tubular portion  156  from the ambient air. 
         [0091]    Additionally, the sampling may continue during the presence of the endoscope probe  198  in the pharynx of the subject, as the tubular portion  156  is of a slightly larger diameter than the central opening  154 , thereby ensuring that medical personnel have the space defined by the difference between heights H 2  and H 1  ( FIG. 8 ), as indicated by arrows in the enlarged portion of  FIG. 10G . 
         [0092]    It is appreciated that following the endoscopy, the bite block  150  may be removed from the subject&#39;s mouth, preferably by medical personnel. Prior to this stage, the valve  144  of oral oxygen delivery tube  142  is removed from tubular portion  174  thereby closing the valve and thus fully decoupling the oral nasal sampling cannula  110  from the endoscopic bite block  150 . However, the sampling of exhaled breath through nasal prongs  118  which remain in the subject&#39;s nostrils and through oral prong  122  which remains near the subject&#39;s mouth, preferably continues until the subject has awaken from the sedation. This is necessary because the subject&#39;s breath must be monitored as long as the subject is sedated. 
         [0093]    Reference is now made to  FIGS. 11A and 11B , which are simplified pictorial illustrations of an oral nasal sampling cannula forming part of an endoscopic bite block assembly, constructed and operative in accordance with yet another preferred embodiment of the present invention, in retracted and extended orientations respectively. 
         [0094]      FIGS. 11A and 11B  show an oral nasal sampling cannula  210 , which is adapted for collection of gases, such as carbon dioxide, exhaled by a subject, and for supplying oxygen to the subject. 
         [0095]    The oral nasal sampling cannula  210  comprises a main body portion  212 , having formed therein an exhaled breath collection bore  214  and an oxygen delivery bore  216 . A pair of hollow nasal prongs  218 , which are adapted for insertion into the nostrils of the subject, is integrally formed with the main body portion  212 . A hollow oral prong  222 , which is formed with a limiting rib  223  and a cut-away tip  224 , is mounted onto a bottom surface of main body portion  212 . An oral breath directing element  226 , which is preferably in the shape of a cut-away tube, is slidably mounted onto oral prong  222  by a mounting portion  228 , and positioning of the oral breath directing element  226  is limited by the limiting rib  223  of oral prong  222 . 
         [0096]    A channel formed in oral prong  222  is in fluid flow connection with channels formed in nasal prongs  218 , thereby forming a single junction  232 . Single junction  232  is in fluid flow communication with exhaled breath collection bore  214 , which in turn is in fluid flow communication with an exhaled breath collection tube  234 , which is adapted to be connected to a breath test analyzer or a capnograph (not shown), such as Microcap® which is commercially available from Oridion Medical LTD. of Jerusalem, Israel. 
         [0097]    Main body portion  212  is formed with oxygen delivery openings  236 , which are in fluid flow communication with oxygen delivery bore  216 , which in turn is in fluid flow communication with an oxygen delivery tube  238 . Alternatively, at least one nasal oxygen delivery prong, adapted for insertion into the subject&#39;s nostril, may be used instead of oxygen delivery openings  236 . Oxygen delivery tube  238  is preferably formed with a T-element  240 , preferably terminating at an end thereof in a normally closed valve element  244 , which is preferably a luer valve. Oxygen delivery tube  238  is adapted to be connected to a source of oxygen (not shown). 
         [0098]    Oxygen delivery tube  238  and exhaled breath collection tube  234  may optionally be placed around the ears of the subject, thereby stabilizing the oral nasal sampling cannula  210  on the subject&#39;s face, such that any movement of the subject will have negligible effect on the placement of the oral nasal sampling cannula  210 . 
         [0099]    It is appreciated that oral breath directing element  226  may be in a retracted orientation as shown in  FIG. 11A , or in an extended orientation as shown in  FIG. 11B , thereby allowing the oral nasal sampling cannula  210  to be suited to the facial dimensions of the subject, resulting in more efficient collection of exhaled breath. 
         [0100]    Reference is now made to  FIGS. 12A and 12B , which are front-view and rear-view simplified pictorial illustrations of an endoscopic bite block forming part of an endoscopic bite block assembly constructed and operative in accordance with yet another preferred embodiment of the present invention and to  FIG. 13 , which is a simplified sectional pictorial illustration thereof. 
         [0101]      FIGS. 12A, 12B and 13  show an endoscopic bite block  250 , which is adapted to be inserted into the mouth of a subject while the subject is sedated, to ensure that the mouth of the subject is maintained open during the endoscopy process, and that the subject does not interfere with the process by biting on medical instruments used. 
         [0102]    The endoscopic bite block  250  includes a main body portion  252 , having formed therein a central opening  254 . A hollow tubular portion  256  extends distally from main body portion  252 , such that the opening of tubular portion  256  is an extension of central opening  254 . Central opening  254  is of a first height, indicated by H 1  in  FIG. 13 , which is typically 16 to 20 mm in bite blocks for adult use, which is the height required by medical personnel for performing an endoscopy. In order to ensure that during breath sampling, oral prong  222  of oral nasal sampling cannula  210  ( FIGS. 11A and 11B ) does not interfere with the space required by medical personnel for performing the endoscopy procedure, the height of tubular portion  256  is greater than the height H 1  of central opening  254  as indicated by H 2  in  FIG. 13 , and is typically 2 to 4 mm more than height H 1  (18 to 24 mm). 
         [0103]    An outer surface  258  of tubular portion  256  is formed with top and bottom teeth engagement surfaces  260  and  262 , such that top teeth engagement surface  260  is relatively forward of bottom teeth engagement surface  262 . This structure facilitates easy and accurate biting of the bite block  250  by a subject, as it is suited to the jaw morphology of a closed human mouth. Surface  258  is additionally formed with jaw engagement recesses  264 , which are formed forwardly of teeth engagement surfaces  260  and  262 , respectively. 
         [0104]    A top inner surface  270  of main body portion  252  is formed with a longitudinal groove  272  having a transverse surface  273 , which is adapted to accommodate oral prong  222  and oral breath directing element  226  of the oral nasal sampling cannula  210  ( FIGS. 12A and 12B ), as described with more detail hereinbelow with reference to  FIG. 14 . 
         [0105]    A tubular portion  274  is formed on a side of outer surface  258  of tubular portion  256 . Extending out of tubular portion  274  is an oral oxygen delivery tube  275  including a tip  276 , which is adapted to engage valve  244  ( FIGS. 11A and 11B ), thereby supplying oxygen directly to the oral cavity of the subject. Preferably, tip  276  comprises a luer corresponding to luer valve  244 . It is appreciated that tubular portion  274  is formed on outer surface  258  of tubular portion  256 , in order to ensure that the oral oxygen delivery does not interfere with the procedure performed by the medical personnel. 
         [0106]    A flexible barrier  277 , preferably comprised of several flaps  278 , is disposed within central opening  254 , thereby substantially closing off the central opening and preventing dilution of exhaled breath by ambient air during sampling. An opening  280  is preferably maintained within flexible barrier  277 , thereby ensuring a small part of central opening  254  remains open in order to enable the subject to inhale external air. The flexible barrier  277  ensures that a majority of the subject&#39;s orally exhaled breath will be directed toward oral prong  222  ( FIGS. 11A and 11B ) thereby ensuring accurate sampling of the subject&#39;s breath. Opening  280  is preferably placed at a top part of central opening  254  near the cut-away tip  224  of oral prong  222  ( FIGS. 11A and 11B ), thereby directing and amplifying exhaled breath toward the oral prong  222  as it is the only substantial exit. 
         [0107]    The flaps  278  are preferably formed of a plastic material selected to be of suitable thickness to maintain their position when undisturbed, yet bend readily when pushed by an endoscope probe, and thus do not limit the actions of the medical personnel performing the endoscopy. However, the flaps  278  preferably close back around the endoscope probe, thus maintaining a substantially closed oral cavity volume, and allowing most of the exchange of gases to occur close to the opening  280  of flexible barrier  277 , which opening is close to the cut-away tip  224  of oral prong  222  ( FIGS. 11A and 11B ) from which capnographic sampling can be performed accurately. 
         [0108]    Additionally, the flaps  278  are preferably transparent, thus enabling medical personnel to see into the oral cavity during the endoscopy procedure. 
         [0109]    Two attachment surfaces  282 , each formed with a slit  284 , extend horizontally outwardly from main body portion  252 . Slits  284  are adapted to connect to a band which is placed around the subject&#39;s head and is used to maintain the endoscopic bite block  250  firmly in position during the endoscopy procedure. Preferably, slits  284  are located above a horizontal centerline of main body portion  252 , such that the connected band will tend to exert a stronger pull to the top of the main body portion  252 , thus assisting in overcoming the subject&#39;s tendency to tilt the bite block  250  outward during the endoscopy procedure and in maintaining the bite block  250  upright in the subject&#39;s mouth. 
         [0110]    Reference is now made to  FIG. 14 , which is a simplified schematic illustration of the connection between the oral nasal sampling cannula of  FIGS. 11A and 11B  and the endoscopic bite block of  FIGS. 12A-13 . 
         [0111]    As seen in  FIG. 14 , oral prong  222  of oral nasal sampling cannula  210  is accommodated within groove  272  of bite block  250 , such that a bottom surface of oral breath directing element  226  engages transverse surface  273  of the groove  272 . It is appreciated that transverse surface  273  is located below an inner surface of tubular portion  256  in order to ensure that air exhaled by the subject into tubular portion  256  will be directed toward groove  272  and oral prong  222 . 
         [0112]    Additionally, tip  276  of oral oxygen delivery tube  275  engages valve  244  ( FIGS. 11A and 11B ) of T-element  240  of oral nasal sampling cannula  210 , thereby opening the valve  244  and forming a fluid flow engagement between oxygen delivery tube  238  and tubular portion  274  of endoscopic bite block  250 , which is in fluid flow engagement with the oral cavity of the subject. 
         [0113]    Reference is now made to  FIGS. 15A, 15B, 15C, 15D, 15E, 15F and 15G , which are pictorial illustrations of various stages of typical use of the endoscopic bite block assembly of  FIGS. 11A-14 . 
         [0114]    As seen in  FIG. 15A , the nasal prongs  218  of the oral nasal sampling cannula  210  are placed in the subjects nostrils, preferably before the subject is sedated. Preferably, the exhaled breath collection tube  234  and the oxygen delivery tube  238  are placed around the subject&#39;s ears, in order to ensure the stability of the oral nasal sampling cannula  210  on the subject&#39;s face. As seen in the enlarged portion of  FIG. 15A , at this stage the oral breath-directing element  226  is in its retracted orientation, indicated by the length H 3 . 
         [0115]    At this stage, oral oxygen delivery tube  275  ( FIGS. 12A-13 ) is not connected to the T-element  240  of oral nasal sampling cannula  210 . However, even if oxygen is supplied to oral nasal sampling cannula  210  via oxygen delivery tube  238 , there is no oxygen leakage, as the T-element  240  is sealed by valve  244 . 
         [0116]    Turning to  FIG. 15B  it is seen that the oral breath directing element  226  is extended to accommodate the facial dimensions of the subject, revealing part of oral prong  222 . Preferably, the oral breath-directing element  226  is moved down to a point in which a bottom end thereof is at the height of the top of the bottom lip of the subject, its new length being indicated by H 4 . This action is preferably preformed by medical personnel, but may alternatively be performed by the subject himself, a family member, or any other person. 
         [0117]      FIG. 15C  illustrates the insertion of bite block  250  into the mouth of the subject, such that main body portion  252  engages the outer surface of the subject&#39;s lips and the tubular portion  256  is inside the subject&#39;s mouth. Additionally, tip  276  of oral oxygen delivery tube  275  is inserted, preferably by medical personnel, into valve  244  of T-element  240  of oral nasal sampling cannula  210 , as indicated by an arrow in the enlarged portion of  FIG. 15C , thereby opening the valve  244 . 
         [0118]    A strap, indicated by reference numeral  290 , is attached to slits  284  of attachment surfaces  282  and is placed around the subject&#39;s head, thereby securing the bite block  250  in place. This stage is preferably performed when the subject is sedated, but may alternatively be performed prior thereto. 
         [0119]    Turning to  FIG. 15D , it is seen that air exhaled orally by the subject, indicated by arrows, passes through the bore of tubular portion  256 , and is directed toward oral breath directing element  226  and oral prong  222  by the flaps  278  of flexible barrier  277 . Air that is exhaled nasally by the subject passes through nasal prongs  218 . 
         [0120]      FIG. 15D  illustrates the oral breath directing element  226  and the oral prong  222  being accommodated in groove  272 , such that a bottom surface of the oral breath directing element  226  engages transverse surface  273  of groove  272 . Additionally, if oral breath directing element  226  has been extended more than necessary for the facial features of the subject, the transverse surface  273  pushes the oral breath-directing element  226  back until it is optimally positioned. The lips of the subject, indicated by reference numeral  292  preferably engage jaw engagement recesses  264 , and the top and bottom teeth of the subject, indicated by reference numerals  294  and  296  engage top and bottom teeth engagement surfaces  260  and  262 , respectively. 
         [0121]      FIG. 15E  illustrates the sedated subject, having the nasal prongs  218  of the oral nasal sampling cannula  210  in his nostrils and the endoscopic bite block  250  placed in his mouth and strapped to his head. Preferably, once the subject is sedated, oxygen is supplied to the nose of the subject via oxygen delivery openings  236  of oral nasal sampling cannula  210 , and to the mouth of the subject via oral oxygen delivery tube  275  and tubular portion  274 , as indicated by arrows. The oxygen is supplied to the oxygen delivery openings  236  via oxygen delivery bore  216  ( FIGS. 11A and 11B ) and to oral oxygen delivery tube  275  via oxygen delivery tube  238  and T-element  240 . 
         [0122]    Turning to  FIG. 15F , it is seen that when the subject is sedated, he tends to move or slump his head, thereby moving oral nasal sampling cannula  210  relative to bite block  250 , as indicated by angle a in the enlarged portion of  FIG. 15F . The feature of the present invention which provides oral nasal sampling cannula  210  which is physically separated from bite block  250  and the placement of oral breath directing element  226  and oral prong  222  within groove  272 , ensure that even when the subject moves or slumps his head, the oral prong  222  and nasal prongs  218  will be maintained in their respective places, and accurate sampling will continue. Additionally, the placement of oral prong  222  within groove  272  provides a counter force to force applied by the subject&#39;s tongue to push at least the top portion of the bite block  250  out of the subject&#39;s mouth, thus ensuring accurate placement of the bite block. 
         [0123]    As seen in  FIG. 15G , an endoscope probe  298  is inserted into the bore of tubular portion  256  of bite block  250 , for performing the endoscopy procedure. During the insertion of endoscope probe  298  and its presence in the subject&#39;s mouth and pharynx, flaps  278  of flexible barrier  277  bend slightly inward to allow the passage of the endoscope probe  298 , as seen with particular clarity in the enlarged portion of  FIG. 15G . However, the central opening  254  of bite block  250  remains substantially closed by flaps  278 , thereby separating the exhaled breath of the subject which is in the bore of tubular portion  256  from the ambient air. 
         [0124]    Additionally, the sampling may continue during the presence of the endoscope probe  298  in the pharynx of the subject, as the tubular portion  256  is of a slightly larger diameter than the central opening  254 , thereby ensuring that medical personnel have the space defined by the difference between heights H 2  and H 1  ( FIG. 13 ), as indicated by arrows in the enlarged portion of  FIG. 15G . 
         [0125]    It is appreciated that following the endoscopy the bite block  250  may be removed from the subject&#39;s mouth, preferably by medical personnel. Prior to this stage, the tip  276  of oral oxygen delivery tube  275  is removed from valve  244  ( FIGS. 11A and 11B ) of T-element  240 , thereby closing the valve and fully decoupling the oral nasal sampling cannula  210  from the endoscopic bite block  250 . However, the sampling of exhaled breath through nasal prongs  218  which remain in the subject&#39;s nostrils and through oral prong  222  which remains near the subject&#39;s mouth, preferably continues until the subject has awaken from the sedation. This is necessary because the subject&#39;s breath must be monitored as long as the subject is sedated. 
         [0126]    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.