Abstract:
A bite block  20  for use during transoral medical procedures has a main lumen  42  and a side mount  110  for receiving a separately inserted airway  160 . The airway  110  may be a commercially available nasopharangeal airway which is inserted in mount  110  and extends into the oral cavity so as to effectively function as oral pharangeal airway.

Description:
RELATED APPLICATION DATA 
     This application claims the benefit of U.S. Provisional App. Ser. No. 61/221,545, filed Jun. 29, 2009, which is hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention is generally related to bite blocks for use during surgical procedures. More particularly, but not exclusively, it relates to novel bite blocks for use during transoral procedures. 
     BACKGROUND 
     Bite blocks are used in a variety of transoral procedures and generally serve to hold the patient&#39;s mouth open and provide an access path for surgical instruments. However, many commercially available bite blocks suffer from a number of defects, such as being are too easily dislodged, being uncomfortable, or failing to provide adequate working area for the instruments which are introduced during the transoral procedure. Furthermore, during some transoral procedures the operating physician may find it desirable to take steps to positively maintain an airway without unduly restricting the ability to operate the instruments. 
     Accordingly, there are needs for improvements in the art. In one form the present application provides improved bite block designs and methods of construction that address one or more of the needs outlined above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a bite block with an airway mount according to one embodiment of the present invention. 
         FIG. 2  is a right side elevational view of the  FIG. 1  bite block. 
         FIG. 3  shows the cross sectional profile as indicated in  FIG. 2 . 
         FIG. 4  is a front elevational view of the  FIG. 1  bite block. 
         FIG. 5  is a top cross sectional view of the  FIG. 1  bite block. 
         FIG. 6  is a perspective view of a nasopharyngeal airway. 
         FIG. 7  shows a top view of the  FIG. 6  airway inserted into the mounting hole of the  FIG. 1  bite block, wherein the bite block is shown in cross section as per  FIG. 5 . 
         FIG. 8  shows an enlarged cross sectional view of an airway in a mounting hole of a bite block according to another embodiment. 
     
    
    
     SUMMARY 
     The present invention provides novel bite blocks for use in performing transoral procedures. While the actual nature of the invention covered herein can only be determined with reference to the claims appended hereto, certain aspects of the invention that are characteristic of the embodiments disclosed herein are described briefly as follows. 
     In one form, what is provided is the combination of a bite block and a nasopharyngeal airway (NPA) wherein, rather than being inserted nasally, the NPA is mounted to the bite block and extends into the oral cavity so as to effectively function as an oral pharyngeal airway. The bite block may include a main bite block body defining an operating lumen and an airway mount configured such that the airway is outside the main operating lumen. The bite block may include an outer face defining a pair of side openings on either side of a main instrument lumen and the airway mount for the NPA may be provided in one of the side openings of the outer face. The airway mount may be molded integrally with the bite block and positioned such that the NPA is generally aligned with the centerline of the main instrument lumen. 
     In another from, what is provided is a bite block having a main instrument lumen and a relatively small diameter airway mount wherein the airway mount is configured to hold a relatively small diameter piece of flexible tubing which would extend into the oral cavity past the distal end of the main instrument lumen, wherein the airway mount has an effective inner diameter which is between 25% and 50% of the effective inner diameter of the main instrument lumen. The bite block may include an outer face adapted to be positioned outside the patient&#39;s mouth during use and defining a pair of side openings wherein one of the side openings is provided with the airway mount. The mount may be configured to hold a nasopharyngeal airway such that it extends into the oral cavity and functions as an oral pharyngeal airway. 
     In another form, what is provided is a bite block for use with a nasopharyngeal airway. The bite block comprises a main bite block body defining upper and lower outer surfaces adapted to be positioned between a patient&#39;s upper and lower teeth respectively and defining an operating lumen for providing instrument access. The bite block also includes an outer face adapted to be positioned outside the patient&#39;s mouth during use. The outer face defines a pair of side openings, and a mount is configured so as to hold a nasopharyngeal airway in one of the side openings such that the nasopharyngeal airway functions as an oral pharyngeal airway. The mount may be molded integrally with the bite block. The mount may be disposed within one of the side openings such that it contacts the interior surface of the side opening in at least two separate locations. The mount may be asymmetrical with respect to the longitudinal axis of the bite block. The mount may be configured to mate with the flared end of the nasopharyngeal airway in a friction fit or snap fit arrangement. The mount may define opposing interior surfaces which are curved and tapered in correspondence with the curvature and taper of the proximal end portion of the nasopharyngeal airway. 
     These and other aspects are described more fully below. 
     DESCRIPTION 
     Referring now to  FIGS. 1-5 , a bite block  20  includes a main bite bock body  30  adapted to be positioned in a patient&#39;s mouth such that the upper and lower surfaces  32 ,  36  are facing the upper and lower teeth (not shown) respectively. Bite block  20  includes a front face  40  which is adapted to be outside the patient and upper and lower flanges  34 ,  38 , which are adapted to be inside the patient&#39;s mouth just behind the upper and lower teeth (not shown). The side ends of the face  40  are provided with a pair of fasteners  48  for connection to a head strap (not shown) which would wrap about the patient&#39;s head and serve to secure the bite block in position. The fasteners  48  are illustrated as conventional T-shaped fasteners that may be coupled to a conventional elastic head strap. 
     Front face  40  of bite block  20  also defines a pair of side or wing openings  50 ,  60 , on the right and left sides of instrument lumen  42  respectively, wherein the front fact includes an arrow  70  which, when in use, would be pointing toward the patient&#39;s forehead. These side openings  50 ,  60  may be used to provide additional access to the oral cavity during a procedure, for example for purposes of providing suction. To facilitate this use, one or both of the side openings  50 ,  60  may be sized and configured to allow passage of rigid tubes having an outer diameter up to at least about 14 mm. 
     Front face  40  of bite block  20  also defines a pair of side or wing openings  50 ,  60 , on the right and left sides of instrument lumen  42  respectively, wherein the front fact includes an arrow  48  which, when in use, would be pointing toward the patient&#39;s forehead. These side openings  50 ,  60  may be used to provide additional access to the oral cavity during a procedure, for example for purposes of providing suction. To facilitate this use, one or both of the side openings  50 ,  60  may be sized and configured to allow passage of rigid tubes having an outer diameter up to at least about 14 mm. 
     An airway mount  110  is disposed in the left side opening  60 , and the purpose of the airway mount  110  is to secure an airway to the bite block  20  such that the airway extends from the side opening  60  distally into the oral cavity and substantially past the distal end of the main lumen  42  so as to effectively provide a positive airway during a procedure. The airway mount  110  may be designed to accommodate any flexible tube having sufficient diameter, length, and rigidity to positively maintain an airway. 
     In a preferred form, the airway mount  110  is specifically designed to accommodate a nasopharyngeal (NPA), which are commercially available airways designed to be used nasally. Nasopharyngeal airways  160 , which are sometime referred to as nasal trumpets, have the shape of an elongated flexible tube with a flared, or trumpet, end  162 . In the conventional use of an NPA, the elongated tube is inserted into a patient&#39;s nasal passage with the flared end  162  abutting against the nostril and serving to prevent the NPA from going into the nasal cavity. Surprisingly, applicants have found that NPAs work well when inserted into the oral cavity so as to function as an oral pharyngeal airway. 
     In the illustrated embodiment, airway mount  110  is in the form of a ring defining a relatively small diameter mounting hole  165  that is generally aligned with the horizontal centerline of the bite block main lumen  42 . The internal surfaces of the mounting hole  165  are oriented so as to define a longitudinal mounting axis generally parallel to the longitudinal axis defined by the main lumen  42 , and the inner diameter of the hole  165  is chosen to accommodate the elongated tube section of a standard NPA  160  but not the flared end  162 . In one form, the effective inner diameter of mounting hole  165  is in between about 7-12 mm or about 9. In other forms, the effective inner diameter of hole  165  is between about 25% and 50% of the effective inner diameter of the main lumen  42 . In other forms, the inner diameter of mounting hole  165  in the range of 9-15 mm, 5-12 mm, 5-15 mm, 6-14 mm, 7-13 mm, 8-12 mm or 8-11 mm. 
     When inserted as shown in  FIG. 7 , the airway  160  is maintained in position via a friction fit. The upper and lower sections  110   a ,  110   b  of the mounting ring extend from interior surfaces of the left side opening  60  near the main body  30  and are curved distally to match the overall curvature of the outer face, as shown in  FIG. 5 . Accordingly, the ring is in the form of an oval which encircles the airway  160  at an acute angle to the longitudinal axis of the airway  160  such that different portions of the mounting ring contact the outer surface of the airway in different longitudinal positions. In other words, the mounting hole  165  is asymmetric relative to the longitudinal axis of the airway  160  with the right side of the mounting hole  165  near the main lumen (at  165  in  FIG. 5 ) contacting a portion of the airway  160  which is proximal to the portion contacted by the left side of the mounting hole  165  opposite the main lumen  30 . The asymmetry helps to maintain the airway  160  in position and to provide increased frictional resistance to the airway being accidentally expelled by the patient&#39;s tongue. Alternatively, the airway mount  110  may be symmetrical with respect to the longitudinal axis of the airway  160 . 
     Optionally, airway mount  110  may also be configured with means to enhance the friction fit with a standard NPA so as to reduce the chance that the NPA would be extruded by the patient. With reference to  FIG. 8 , the airway mount may include oppositely disposed mounting members  220 ,  230  which provide an engagement surface for the trumpet end of the NPA. The engagement surface may be inwardly tapered so as to match the outer taper of the trumpet end of the NPA. As illustrated, the mounting members  220 ,  230  have a thickness greater than the thickness of the adjacent face plate  40  so as to increase the surface area provided for engagement with the body of the airway  160 . The tapered engagement surface may optionally be provided with gripping teeth  240  or a rubberized surface to further enhance the friction fit. As shown, the mounting members also include rounded shoulders  250  which extend above the adjacent surface of the face plate  40 . These shoulders  250  are designed to mate with the underside of the flared end  162  of the NPA in a press fit engagement. 
     The airway mount  110  may be located in other locations within the left side hole  60 , such as in the upper or lower lobes of the side hole  60 , or in the right side hole  50 . Alternatively, airway mount  110  may be aligned with one of the side openings  50 ,  60  but coupled to a different portion of the bite block  20 , such the main body  30  or some other portion of the front face  40 . The airway mount  110  can be provided as an attachment to the bite block, but preferably the mount  110  is molded integrally with the bite block. Alternatively or in addition, a strap may be used to secure the NPA to the biteblock. 
     Bite block  20  may be formed from any number of biocompatible or food grade synthetic or polymeric materials. The material may be selected such that bite block  20  may be formed by a conventional molding process, such as injection molding. Preferably, the material is selected to be relatively resilient plastic. 
     In one form, the bite block material has a Shore D Durometer hardness (calculated per ASTM D2240) less than 65, more typically in the range about 45 to about 60. In another form, the bite block material is a low density polymer mixture, for example having a density below 9.4 g/cm 3 . One suitable material is Paxothene NA207-66 available from USI Corporation (Taipei, Taiwan), which is a low density polyethylene (LDPE) having a density of 0.921 g/cm 3  and a Shore D hardness of 53. 
     Referring to the cross sectional schematic depicted in  FIG. 3 , the side wall thickness T 1  and the upper and lower wall thickness T 2  of the main body  30  are preferably chosen such that the resulting structure resists compression under an applied bite load up to about 33 lbs. Such a compressive force may cause slight deformation to the inner dimensions, but preferably, block body  30  is designed such that the effective inner diameter of instrument lumen  42  is at least 20 mm under a bite load of about 30 lbs. For example T 1  and T 2  may be in the range of about 3-7 mm, for example, between 4-6 mm. In one implementation, T 1  is about 5.7 mm and T 2  is about 5.0 mm. In comparison, for conventional bite blocks constructed from high density polyethylene (HDPE), which would typically have a Shore D hardness above 65, a typical wall thickness may be only about 2 mm. 
     Upper and lower lip portions  34 ,  38  rise above the upper and lower surface portions  32 ,  36  to form a retaining flange or lip. With reference to  FIG. 2 , the rise R from the tooth landing to the top of a respective retaining lip is preferably in the range of 3-5 mm, for example, about 3.5 mm. The overall height H between the upper and the lower retaining flanges is preferably in the range of about 35 mm to about 45 mm, for example between 40 and 45 mm, for example about 41 mm. By comparison, known commercially available bite blocks have a slightly lower lip rise (R) and an overall retaining flange height (H) of around 31.5 mm. The larger overall height H makes it harder for the patient to expel the block, because the patient would need to open his mouth wider to clear the flange. 
     Nasopharyngeal airways (NPAs) which may be used are commercially available from a number of manufacturers. One example may be the 26Fr ARGYLE Nasopharyngeal Airway (Covidien LP, Argyle, NY), which has a length L of about 11 cm, an inner diameter of about 6.5 mm, and outer diameter (W) of about 8.7 mm. 
     While the inventions have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character. Only certain embodiments have been shown and described, and all changes, equivalents, and modifications that come within the spirit of the invention described herein are desired to be protected. Any experiments, experimental examples, or experimental results provided herein are intended to be illustrative of the present invention and should not be considered limiting or restrictive with regard to the invention scope. Further, any theory, mechanism of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention and is not intended to limit the present invention in any way to such theory, mechanism of operation, proof, or finding. Thus, the specifics of this description and the attached drawings should not be interpreted to limit the scope of this invention to the specifics thereof.