Abstract:
An airway tube for an airway device for human or animal use said airway tube having a first end and a second end, wherein the airway tube includes a first lumen and a second lumen, each of said first and second lumens extending from the first end to the second end of the airway tube. A a flexible wall is provided between the first lumen and the second lumen extending from the first end to the second end of the airway tube wherein movement of the flexible wall varies the cross-sectional area of the first lumen and the second lumen.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to medical devices and is applicable to airway tubes for airway devices. It is particularly applicable to airway tubes for supraglottic airway devices, more particularly to airway tubes for laryngeal airway devices and to their methods of manufacture. It is particularly applicable to airway tubes for airway devices used in the administration of Oxygen and/or anaesthetic gases to a human or veterinary patient breathing spontaneously, for Intermittent Positive Pressure Ventilation (IPPV) during a surgical procedure or resuscitation. 
       BACKGROUND TO THE INVENTION 
       [0002]    GB2393399 (Nasir) describes an airway device comprising an airway tube having a first end and a second end, the first end of which is surrounded by a non-inflatable laryngeal cuff which forms an anatomical fit over the laryngeal inlet of a patient and a buccal cavity stabiliser located on or around the airway tube between the laryngeal cuff and the second end of the tube, the buccal stabiliser being adapted to prevent rotational or side-to-side movement of the airway device in use. In addition to the airway tube the airway device described may also comprise a gastric tube. The airway tube is provided for fluid connection with the lungs of the patient and the gastric tube is provided for fluid connection with the stomach of the patient. The gastric tube, if provided, is housed in the buccal cavity stabiliser next to the airway tube. 
         [0003]    However, a buccal cavity stabiliser is not appropriate for all clinical situations and can sometimes impede rather than enhance the operation. For example in many opthamalogical, and maxillofacial or dental surgery the use of a reinforced tube is preferable, as the tube can flexibly move to one side to continue to provide an airway for the patient, whilst not interfering with the operation. An alternative device which does not have a buccal cavity stabiliser has been described in GB2404863. However, this device suffers from the disadvantage that no gastric tube has been provided. 
         [0004]    In other supraglottic airway devices which do not have a buccal cavity stabiliser the airway tube and the gastric tube are typically formed as separate discrete tubes, which are then attached to one another such as described in EP1169077 (Brain). In addition both the airway tube and the gastric tube once formed are of fixed cross-sectional area. This limits the size of tubes, scopes and other devices that may need to be passed through the airway tube and the gastric tube to the fixed cross-sectional area of the respective tube. In order to accommodate larger tubes, scopes and other devices that may need to be passed through the airway tube and the gastric tube, attempts have been made in the prior art to provide airway devices having large bore airway tubes and the gastric tubes such as described in EP1220701 (Brain). However, such large bore airway tubes and the gastric tubes are also of fixed cross-sectional area. 
       SUMMARY OF THE INVENTION 
       [0005]    A first aspect of the present invention provides an airway device as described in the accompanying claims. 
         [0006]    Accordingly, according to a first aspect of the present invention, there is provided an airway tube for an airway device for human or animal use said airway tube having a first end and a second end, wherein the airway tube comprises a first lumen and a second lumen, each of said first and second lumens extending from the first end to the second end of the airway tube, wherein a flexible wall is provided between the first lumen and the second lumen extending from the first end to the second end of the airway tube, wherein movement of the flexible wall changes the cross-sectional area of the first lumen and the second lumen. 
         [0007]    According to a second aspect of the invention there is provided an airway device for human or animal use comprising and airway tube having a first end and a second end, the first end of which is surrounded by a laryngeal cuff configured to fit over the laryngeal inlet of a patient when in situ, wherein the airway tube comprises a first lumen and a second lumen, each of said first and second lumens extending from the first end to the second end of the airway tube, wherein a flexible wall is provided between the first lumen and the second lumen extending from the first end to the second end of the airway tube, wherein movement of the flexible wall changes the cross-sectional area of the first lumen and the second lumen. 
         [0008]    Preferably movement of the flexible wall to increase the cross-sectional area of the first lumen results in a decrease in the cross-sectional area of the second lumen. 
         [0009]    Preferably movement of the flexible wall to increase the cross-sectional area of the second lumen results in a decrease in the cross-sectional area of the first lumen. 
         [0010]    Preferably the first lumen is configured for airway access, preferably for fluid communication with the lungs of patient when in situ. 
         [0011]    Preferably the second lumen is configured for gastric access, preferably for fluid communication with the stomach of the patient when in situ. 
         [0012]    By providing an airway tube having two lumens for both airway access and gastric access, wherein the cross-sectional area of each can be varied, a greater variety of tubes, scopes and other devices that may be required to be passed through the respective lumens can be accommodated in a single airway tube, and thus a single airway device. 
         [0013]    Preferably the circumference of the first lumen remains constant; however, the cross-sectional area is variable. Preferably the circumference of the first lumen is fixed; however, the cross-sectional area is variable. For the avoidance of doubt the term circumference is intended to include the cross-section length of the perimeter of the lumen, be it the first lumen or then second lumen. 
         [0014]    In the alternative both the circumference and the cross-sectional area for the first lumen are variable. 
         [0015]    Preferably the circumference of the second lumen remains constant; however, the cross-sectional area is variable. Preferably the circumference of the second lumen is fixed; however, the cross-sectional area is variable. 
         [0016]    In the alternative both the circumference and the cross-sectional area for the second lumen are variable. 
         [0017]    In one alterative the first and second lumens are of integral construction. Preferably airway tube is formed from extrusion moulding allowing the first and second lumens to be extruded in a single integral component. In this alternative the flexible wall may be expandable or non-expandable. 
         [0018]    In another alternative the first and second lumens are formed separately as individual components. In this alternative the cross-sectional area of the second lumen is preferably smaller than the cross-sectional area of the first lumen. Preferably the second lumen is located wholly inside the first lumen. Preferably the second lumen in its rest position in cross-section is in the form of a deformable shape. This means that when a large tube, scope or other instrument is passed down the first lumen it pushes against the deformable shape of the second lumen causing the second lumen to collapse and thus its cross-sectional area to decrease. This also means that when a large tube, scope or other instrument is passed down the second lumen it pushes against the deformable shape of the second lumen causing the second lumen to expand and thus its cross-sectional area to increase. Preferably the second lumen in its rest position is formed of any suitable deformable shape to allow the second lumen to both collapse (and thus its cross-sectional area to decrease) and to expand (and thus its cross-sectional area to increase). In one alternative the deformable shape is a lemon, in another alternative an inverted lemon, in another alternative a circle. In this alternative the wall of the second lumen forms the flexible wall provided between the first lumen and the second lumen. In this alternative the flexible wall may be expandable or non-expandable, such that the circumference of the second lumen is fixed or expandable. 
         [0019]    Preferably the first lumen is configured to extend beyond the second lumen at the second end of the airway tube. In the alternative the second lumen is configured to extend beyond the first lumen at the second end of the airway tube. 
         [0020]    Preferably the second lumen is configured to extend beyond the first lumen at the first end of the airway tube. In the alternative the second lumen is configured to extend beyond the first lumen at the first end of the airway tube. 
         [0021]    Preferably the second end of the airway tube is provided with a connector. Preferably the connector is provided with a first lumen for fluid connection with the first lumen of the airway tube. Preferably the connector is provided with a second lumen for fluid connection with the second lumen of the airway tube. Preferably the connector comprises a first component configured to fit over a portion of the second end of the airway tube. Preferably the first component is configured to provide an aperture to the second lumen of the connector and thus to the second lumen of the airway tube. Preferably the aperture is provided in the side wall of the first component. Preferably the connector comprises a second component configured to fit inside a portion of the second end of the first lumen such that a portion of the second end of the first lumen is retained between the first and second components of the connector to retain the connector in position about the airway tube. Preferably the portion of the second end of the first lumen is pinched or squashed between the first and second components of the connector. Preferably the first and second components of the connector are provided with respective male and female interlocking components to interlock the first and second components of the connector. The male and female interlocking components may cooperate for example to comprise a spring clip. 
         [0022]    Preferably the external surface of the airway tube is provided with a reinforcing means. Preferably the reinforcing means comprises a spiral bead of material of greater shore hardness than the airway tube located around the external wall of the airway tube. Preferably the reinforcing means extends from the second end of the airway tube to the first end of the airway tube. Preferably the reinforcing means comprises polypropylene. 
         [0023]    The reinforcing means is used to prevent kinking of the airway tube when it is bent. A kinked airway tube can result in the air supply to the patient being significantly reduced or cut off. 
         [0024]    In the prior art the reinforcing means is typically a spiral wire embedded into the wall of the airway tube. However, by providing an external reinforcing means from a plastics material this means that the device can remain in situ in the patient during procedures where metal cannot be used such as in Magnetic Resonance Imaging (MRI) procedures. 
         [0025]    Preferably the airway tube is formed via linear extrusion with a rotating extruder ring around configured to extrude the spiral bead whilst the airway tube linear extrusion is still hot. 
         [0026]    Preferably the reinforcing means does not extend beyond the first lumen at the first end of the airway tube. 
         [0027]    Preferably the reinforcing means does not extend beyond the second lumen at the second end of the airway tube. 
         [0028]    Preferably the cuff is non-inflatable and is pre-formed in a shape adapted to form an anatomical fit over the laryngeal framework of a patient. 
         [0029]    Preferably the laryngeal cuff is pre-formed, pre-inflated with air or pre-filled with a suitable fluid. Most preferably the laryngeal cuff is non-inflatable, however in the alternative the laryngeal cuff can be inflatable. 
         [0030]    Preferably the laryngeal cuff is over moulded onto the first end of the airway tube linear extrusion. 
         [0031]    Preferably the second lumen is configured to exit the laryngeal cuff at the tip thereof. 
         [0032]    In one alternative the airway device further comprises a buccal cavity stabiliser located on or around the airway tube between the laryngeal cuff and the second end of the tube. The buccal cavity stabiliser, if provided, may be formed from the same material as the cuff or from a different material and assists in locating and maintaining the position of the device in use. 
         [0033]    In a particularly preferred embodiment the buccal cavity stabiliser, if provided, is formed as an integral part of the airway tube, and further preferably the buccal cavity stabiliser, if provided, the airway tube and the laryngeal cuff are all formed as an integral unit. 
         [0034]    In a further alternative no buccal cavity stabiliser is provided. 
         [0035]    The Shore hardness of the various, parts, portions or components is an important feature of the invention. For example, the laryngeal cuff is preferably formed from a material with a Shore hardness on the A scale of 40 or less and more preferably 000 to 20, and most preferably 000 to 4. 
         [0036]    Preferably the laryngeal cuff and a front, ventral part of the buccal cavity stabiliser, if provided, are formed from a material of substantially the same Shore hardness. This simplifies construction and ensures that all portions of the device that come into firm contact with the patient&#39;s soft tissue are relatively soft. 
         [0037]    In a further preferred embodiment a back or dorsal part of the device and a front or ventral part of the device are formed from materials of different Shore hardness. This enables the dorsal portion to be made of a firmer material than the ventral portion. 
         [0038]    Preferably the back or dorsal part of the device is formed from a material of Shore hardness less than 60 on the A scale, more preferably 25 to 45, and most preferably 30 to 40. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]    The invention will now be described, by way of example only, with reference to the accompanying drawings in which:— 
           [0040]      FIG. 1  illustrates a cross-sectional view of the airway tube according to a first embodiment; 
           [0041]      FIG. 2  illustrates a perspective view of a portion of the airway tube according to a first embodiment; 
           [0042]      FIG. 3  illustrates a side view of the airway tube according to a first embodiment; 
           [0043]      FIG. 4  illustrates a cross-sectional view of the airway tube according to a second embodiment; 
           [0044]      FIG. 5  illustrates a cross-sectional view of the second lumen of the airway tube according to a second embodiment; 
           [0045]      FIG. 6  illustrates a perspective view of a portion of the airway tube according to a second embodiment; 
           [0046]      FIG. 7  illustrates a longitudinal cross-sectional view of the airway tube according to a first embodiment in combination with a laryngeal cuff; 
           [0047]      FIG. 8 a    illustrates a side view of the second portion of the airway tube according to a first embodiment with a connector; 
           [0048]      FIG. 8 b    illustrates a side cross-sectional view of the second portion of the airway tube according to a first embodiment with a connector; and 
           [0049]      FIG. 9  illustrates a cross-sectional view of an alternative construction of the second lumen of the airway tube according to a second embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0050]    Embodiments of the present invention are described below by way of example only. These examples represent the best ways of putting the invention into practice that are currently known to the applicant although they are not the only ways in which this could be achieved. 
         [0051]    Referring to  FIGS. 1 to 3 , these illustrates an airway tube  10  according to a first embodiment of the invention. The airway tube  10  has a first lumen  14 , a second lumen  16  and a flexible wall  12  there between. The first lumen  14  is configured for airway access, and delivers gasses to the patient. The second lumen  16  is configured for gastric access. It may be necessary after the airway tube  10  has been inserted into the patient to insert further tubes, scopes or other devices through either the first lumen  14 , or the second lumen  16 , into the patient. When a tube needs to be inserted into the first lumen  14 , that is larger than the cross-sectional area illustrated in  FIG. 1 , the flexible wall  12  simply moves, as the tube, is inserted, towards the second lumen  16 . In doing so the cross-sectional area of the first lumen  14  increases, and the cross-sectional area of the second lumen  16  decreases to accommodate the tube through the first lumen. Should a tube then need to be inserted into the second lumen  16 , the tube inserted into the first lumen  14  can be removed, and then the tube which is larger in cross-section than the current cross-sectional area of the second lumen  16 , can then be inserted into the second lumen  16 . As the tube is inserted into the second lumen  16 , the flexible wall  12  again simply moves, as the tube is inserted, towards the first lumen  14 . In doing so the cross-sectional area of the second lumen  16  increases and the cross-sectional area of the first lumen  14  decreases, to accommodate the tube through the second lumen  16 . 
         [0052]    In the alternative, as well as the flexible wall  12  being flexible, the flexible wall  12  is also expandable, such that not only the cross-sectional area of the respective lumens  14 ,  16  changes, but also the circumference thereof. 
         [0053]    Referring to  FIGS. 4 to 6 , these illustrate an airway tube  110  according to a second embodiment of the invention. The airway tube  110  has a first lumen  114  within which is housed a second lumen  116 . The wall  112  of the second lumen forms the flexible wall there between. The first lumen  114  is configured for airway access, and delivers gasses to the patient. The second lumen  116  is configured for gastric access. When a tube needs to be inserted into the first lumen  114 , that is larger than the cross-sectional area illustrated in  FIG. 4 , the flexible wall  112  simply moves, as the tube, is inserted, to cause the second lumen  116  to collapse. In doing so the cross-sectional area of the first lumen  114  increases, and the cross-sectional area of the second lumen  116  decreases to accommodate the tube through the first lumen. Should a tube then need to be inserted into the second lumen  116 , the tube inserted into the first lumen  114  can be removed, and then the tube which is larger in cross-section than the current cross-sectional area of the second lumen  116 , can then be inserted into the second lumen  116 . As the tube is inserted into the second lumen  16 , the flexible wall  112  again simply moves, as the tube is inserted, to cause the second lumen  116  to expand. In doing so the cross-sectional area of the second lumen  116  increases and the cross-sectional area of the first lumen  114  decreases, to accommodate the tube through the second lumen  116 . 
         [0054]    In the embodiment illustrated the shape of cross-section of the second lumen  116  is a lemon shape. Such a shape allows the second lumen  116  to readily collapse and expand. Other suitable shapes of cross-section of the second lumen  116  which also allow the second lumen  116  to readily collapse and expand include an inverted lemon wherein the tips of the lemon point into rather than away from the body of the lemon as illustrated in  FIG. 9 . Further in the alternative the cross-section of the second lumen  116  may be a circle. Yet further in the alternative the cross-section of the second lumen  116  may be any other suitably deformable shape. 
         [0055]    In the alternative, as well as the flexible wall  112  being flexible, the flexible wall  112  is also expandable, such that not only the cross-sectional area of the respective lumens  114 ,  116  changes, but also the circumference of the second lumen  116 . 
         [0056]    In both embodiments the second lumen  16 ,  116  optionally extends beyond the first lumen  14 ,  114  at the second end of the airway tube  10 ,  110  and the second lumen  16 ,  116  optionally extends beyond the first lumen  14 ,  114  as the first end of the airway tube  10 ,  110 . 
         [0057]    In both embodiments the external surface of the airway tube  10 ,  110  is optionally provided with a reinforcing means  18 ,  118 . The reinforcing means  18 ,  118  is configured to prevent the airway tube from kinking when it is bent. The reinforcing means  18 ,  118  illustrated in accordance to the first and second embodiments is a spiral bead of material, in one alternative a plastics material, of greater shore hardness than the airway tube  10 ,  110  itself such as polypropylene. 
         [0058]    Where a reinforcing means  18 ,  118  is provided it optionally does not extend beyond the end of the second lumen  16 ,  116  at the second end of the airway tube  10 ,  110  and the end of the first lumen  14 ,  114  at the first end of the airway tube  10 ,  110 . 
         [0059]    In both embodiments the airway tube  10 ,  110  is optionally provided with a connector  20  configured to connect the airway tube  10 ,  110  for connection to an anaesthetic breathing system of conventional type. A suitable connector  20  is illustrated in  FIGS. 8 a    and  8   b.    
         [0060]    The connector  20  is formed from a first component  22  and a second component  24 . The first component  22  is provided with a first lumen  26  for fluid connection with the first lumen  14  of the airway tube  10  and a second lumen  28  for fluid connection with the second lumen  16  of the airway tube  10 . The first component  22  is also provided with an aperture  36  in the side wall thereof for fluid connection with the second lumen  28  of the first component  22  and thus the second lumen  16  of the airway tube  10 . The second component  24  is provided with a first lumen  30  for fluid connection with the first aperture  26  of the first component  22  and the first lumen  14  of the airway tube  10 . 
         [0061]    The first component  22  of the connector  20  is configured to fit over a portion of the second end of the airway tube  10 . In the embodiment illustrated in  FIGS. 8 a  and 8 b   , the first lumen  14  of the airway tube  10  is configured to extend beyond the second lumen  16  of the airway tube  10  at the second end of the airway tube. The first component  22  of the connector  20  is configured to fit over a portion of the second end of the first lumen  14  of the airway tube  10 . The second aperture  28  of the first component  22  is configured to connect with the second lumen  16  of the airway tube  10  and exit the side wall of the first component  22 . 
         [0062]    The second component  24  of the connector  20  is configured to fit inside a portion of the second end of the airway tube  10 . In the embodiment illustrated in  FIGS. 8 a  and 8 b   , the first lumen  14  of the airway tube  10  is configured to extend beyond the second lumen  16  of the airway tube  10  at the second end of the airway tube. The second component  24  of the connector  20  is configured to fit inside a portion of the second end of the first lumen  14  of the airway tube  10  such that a portion of the first lumen  14  is retained between the first and second components  22 ,  24  of the connector  20  to retain the connector  20  in position about airway tube  10 . 
         [0063]    The first lumen  14  should be pinched or squashed between the first and second components  22 ,  24  of the connector  20  to retain the connector  20  in position about airway tube  10 . 
         [0064]    In order to connect the first and second components  22 ,  24  together to form the connector  20  once it is in situ about the airway tube  10  the first and second components  22 ,  24  are provided with interlocking male and female components to interlock the first and second components  22 ,  24  of the connector  20 . In the embodiment illustrated in  FIGS. 8 a  and 8 b    a spring clip  32  is provided. 
         [0065]    In one embodiment illustrated in  FIG. 7  formed around the first end of the airway tube is a laryngeal cuff  34 . In the embodiment illustrated the laryngeal cuff is non inflatable and is adapted in its shape and contours to correspond with the laryngeal inlet region of a patient. In one preferred embodiment the laryngeal cuff is non-inflatable and is formed from any suitable soft plastics material. By way of a preferred softness (hardness) range, on the Shore A scale of Hardness, a hardness of less than 40 for the face of the laryngeal cuff that contacts the laryngeal inlet is optimum. By way of a preferred range, a value on the same scale of 000 to 20 is preferred, with a particularly preferred range of 000 to 4. The softness of the laryngeal cuff can be further adapted by forming cavities or channels within the body of the cuff itself. 
         [0066]    In a further preferred embodiment the laryngeal cuff may be pre-filled with a fluid such as air, or other non-toxic gas, or a non-toxic liquid. In this context the term fluid has a broad meaning and includes any suitable gas, liquid, vapour or combination thereof and will be determined and designed by an expert in this field of anatomy/anaesthesia in conjunction with the materials specialist. The laryngeal cuff will be constructed of such a material which will not allow nitrous oxide (anaesthetic gas) to diffuse through the material to any significant amount so that the extra luminal pressure is kept constant. It follows therefore that the laryngeal cuff should be substantially impermeable to the fluid with which is filled and to anaesthetic gases. 
         [0067]    Alternatively, the laryngeal cuff can be formed from a soft, foamed material or can be foam filled. In either case this provides a soft deformable but shaped surface around the face of the laryngeal cuff to engage over the anatomy of the larynx inlet region. Such a foam filled device will minimise any potential damage to the structures in that region whilst still providing a substantially complete seal. 
         [0068]    Further in the alternative the laryngeal cuff is pre-filled during manufacture with a fluid in which case the lining of the cuff should be made from a material that does not absorb anaesthetic gases such as Nitrous Oxide, such that the pressure inside the cuff does not rise during use. 
         [0069]    In another alternative embodiment the laryngeal cuff may be formed from a material which is adapted to absorb a liquid, such as water, mucous or blood or similar liquid material and in doing so to swell in size so as to confirm to the anatomical mucocartilagenous framework of the patient&#39;s laryngeal inlet. Such materials will be selected by the materials specialist but include CRM (cotton rayon mixes) as used in TAMPAX® tampons, or compressed Gel Foam 5. 
         [0070]    In a further, alternative embodiment, the laryngeal cuff could take the form of a conventional, inflatable laryngeal cuff. The technology to form an inflatable laryngeal cuff is well known and need not be described here. 
         [0071]    Finally the laryngeal cuff may be hollow, but not inflatable in the traditional sense of the word, and instead Positive Pressure Ventilation is employed to “inflate” and self-pressurise the laryngeal cuff. 
         [0072]    The device may be constructed from any suitable plastics material as selected by the materials specialist. Latex-free medical grade silicone rubber is one preferred material. The cuff should be soft in texture to avoid undue damage to the surrounding tissue. Other suitable materials for construction of this type of device include, but are not limited to, Poly Vinyl Chloride (PVC), Thermoplastic Elastomers such as the styrenic block copolymers (eg Styrene Butadiene Styrene (SBS), Styrene Ethylene Butylene Styrene (SEBS)), and Thermoplastic Olefin Blends (TPO), Thermoplastic PolyUrethanes (TPU), Copolyester (COPE), Polyether Block Amides (PEBAX) and foamed versions thereof, where appropriate. 
         [0073]    A further important factor involved in the choice of a suitable material is transparency. Ideally the material or materials of construction should be substantially clear or transparent. This enables the anaesthetist or operator to see the inner lumen of the airway to check for blockages or other problems. Such transparent materials are known to the materials specialist.