Abstract:
A cannula assembly including a cannula body having a perfusion lumen extending therethrough; a removable introducer to be carried in the perfusion lumen, the removable introducer including a first hole, a second hole and a central lumen extending therebetween to allow fluid entering the first hole to flow through the central lumen and exit the second hole into the perfusion lumen; and a cap member including at least one venting means that allows air displaced by the fluid entering the first hole to be vented from the cannula body.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/030,533, filed Feb. 21, 2008, entitled “Improved Cannula”, which is also hereby incorporated herein by reference. 
     
    
     BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present invention relates generally to medical devices and methods, and more specifically to an improved cannula for aortic, femoral, and axillary use that may use an introducer for vascular insertion. 
         [0004]    2. Related Art 
         [0005]    The cannula of choice for most applications is femoral cannula that is flexible and uses an introducer to provide structural support to facilitate insertion. Current market trends have identified that surgeons are now using femoral cannula for aortic applications. The reason for this trend is that patients are expecting smaller incisions resulting from medical procedures which translate to faster recovery times and less scarring. The femoral cannula with an introducer fits the need for small incision procedures. 
         [0006]    Unfortunately, femoral cannula designs do not provide automatic air venting capabilities, and most do not have satisfactory cannula to introducer edge transitions to facilitate smooth insertions into diseased aortas. For example, currently surgeons who use femoral cannula for aortic applications are forced to accept cannula with gaps between the introducer outer diameter (OD) and the cannula inner diameter (ID), which creates a larger step transition that may “catch” tissue and possibly tear a fragile diseased aorta (See  FIG. 6 ). Also, a surgeon must manually vent air from the cannula before the surgeon may push the surgeon may release air emboli into the aorta increasing the risk for a patient stroke. Moreover, the manual venting releases excessive amounts of blood within the sterile field and may spray clinicians within the area. 
       SUMMARY 
       [0007]    The present invention is directed to an improved cannula with an introducer in which a structure for automatic venting of the cannula is embodied in the length of the introducer and a cap of the cannula body. Moreover, the automatic venting allows the cannula to introducer transition edge to have a reduced profile to facilitate smooth insertions into diseased aortas. 
         [0008]    The introducer is formed to incorporate an opening or hole that allows blood to fill the cannula body via the introducer tip opening or hole, which is typically designed for tracking guidewires within the vasculature. A self venting cap is provided which allows for a semi-seal between the introducer and the cannula body, while allowing air to escape when being displaced by blood filling the cannula body, thereby protecting the clinician and minimizing blood loses while in use. 
         [0009]    Further, the self venting cap allows the cannula to be designed with a minimal cannula to introducer transition edge, using, for example, a tight or “interference” fit, with virtually no gap, between the introducer OD and the cannula ID to minimize the height of the cannula tip stepped edge. 
         [0010]    In one aspect, a cannula assembly is provided including a cannula body having a perfusion lumen extending therethrough. A removable introducer, including a tip hole, a side hole and a central lumen extending therebetween, is carried in the perfusion lumen. The introducer allows fluid entering the tip hole to flow through the central lumen and exit a side hole into the perfusion lumen. A cap member, including at least one vent channel, allows air displaced by the blood entering the tip hole of the introducer to be vented from the cannulae body. 
         [0011]    The foregoing and other features and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The features, objects, and advantages of the invention will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, wherein: 
           [0013]      FIG. 1  is a side view of a cannula assembly in accordance with an embodiment of the present invention; 
           [0014]      FIG. 2A  is a simplified side view of a portion of the cannula assembly of  FIG. 1  in accordance with an embodiment of the present invention; 
           [0015]      FIG. 2B  is a simplified side view of a portion of the introducer of  FIG. 2A  in accordance with an embodiment of the present invention; 
           [0016]      FIG. 2C  is a view of the tip of the cannula assembly in accordance with an embodiment of the present invention; 
           [0017]      FIGS. 3A and 3B  are axial and perspective views, respectfully, of the cap member in accordance with an embodiment of the present invention; 
           [0018]      FIG. 4  is a simplified view of the use of the cannula assembly in a human aorta in accordance with an embodiment of the present invention; 
           [0019]      FIG. 5  is a simplified view of the cannula assembly, shown in partial section, in accordance with an embodiment of the present invention; 
           [0020]      FIG. 6  is a tip view of a typical cannula with an introducer; 
           [0021]      FIGS. 7A and 7B  are simplified illustrations of another embodiment of the cannula assembly; 
           [0022]      FIGS. 8A and 8B  are simplified illustrations of another embodiment of the cannula assembly; 
           [0023]      FIGS. 9A and 9B  are simplified illustrations of another embodiment of the cannula assembly; and 
           [0024]      FIGS. 10A-10H  are simplified illustrations of various embodiments of the cap member and means for venting the cap member in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The following description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Various changes to the described embodiments may be made in the function and arrangement of the elements described herein without departing from the scope of the invention. 
         [0026]      FIG. 1  is a side view of a cannula assembly  100  in accordance with an embodiment of the present invention. Cannula assembly  100  includes a cap member  102  disposed at a distal end of cannula assembly  100 , and a cannula body  104  concentrically surrounding an introducer  106 . 
         [0027]    Introducer  106  may have a blunt distal end  112  and a handle  114  at a proximal end  116  of cannula assembly  100  to abut cap member  102  as introducer  106  moves into the end of cap member  102  and into cannula assembly  100  in a slip-lock relationship. Introducer  106  may also include a cap  120  that is used to close-off introducer  106 , for example, when a guidewire is not being used to track introducer  106  within the vasculature. Cap  120  may include a porous cap or plug to ensure that the central lumen of introducer  106  may vent air and seal when blood comes in contact with the cap. 
         [0028]      FIG. 2A  illustrates a distal portion  200  of cannula assembly  100  that includes a portion of cannula body  104  and a portion of introducer  106  as part of the assembly. In one embodiment, cannula body  104  includes a central perfusion lumen  202 , which extends from a barbed proximal end  108  ( FIG. 1 ) to a distal end of cannula body  104 , also referred to as cannula tip  204 . Introducer  106  may be removably received via cap member  102  into perfusion lumen  202  to facilitate the introduction of cannula assembly  100  into the body vasculature as will be later described. Cannula body  104  may be formed of any suitable flexible plastic material and may include a reinforcing coiled spring (not shown) embedded in the wall of cannula body  104 . 
         [0029]    As further illustrated in  FIGS. 2B and 2C , introducer  106  may be formed as a tube having a tip hole  208  defined at the distal end  206  that serves as entry into a central lumen  210  defined axially through introducer  106 . 
         [0030]    In one embodiment, introducer  106  further defines at least one opening or hole  212  (hereinafter “hole  212 ”), to a plurality of holes  212 , defined through the wall of introducer  106  to be in communication with central lumen  210 . Hole  212  may be positioned anywhere along the length of introducer  106  between the distal tip of cannula  204  and proximal end of cannula assembly  100 . 
         [0031]    In this embodiment, hole  212  of introducer  106  allows fluid, typically blood, entering introducer  106  through tip hole  208  to fill central lumen  210 . In one embodiment, blood fills central lumen  210  until it reaches hole  212 . The blood is then able to exit hole  212  and fill or prime perfusion lumen  202  of cannula body  104  which surrounds introducer  106 . 
         [0032]      FIGS. 7A and 7B  illustrate another embodiment of cannula assembly  100  that allows a fluid, such as blood, to enter perfusion lumen  202 . In this embodiment, introducer  702  includes an introducer tip  706  having a proximal end portion  710  that is sized to engage a distal end of cannula body  104  as described above. Introducer  702  also includes a portion  704  having a reduced OD relative to proximal end portion  710  of introducer tip  706 . In this embodiment, distal tip  204  of cannula body  104  includes at least one opening  708  defined thereon to be in communication with perfusion lumen  202 . Opening  708  is positioned to be adjacent to portion  704  when introducer  702  is assembled for deployment. Because of the reduced OD of portion  704 , blood is allowed to enter into opening  708  and fill perfusion lumen  202 . 
         [0033]      FIGS. 8A and 8B  illustrate yet another embodiment of cannula assembly  100  that allows a fluid, such as blood, to enter perfusion lumen  202 . In this embodiment, introducer  802  includes at least one channel or groove  804  formed or cut axially along the OD of introducer  802 . Groove  804  may extend from a position within perfusion lumen  202  to a position distal to distal cannula tip  204  of cannula body  104  (shown dashed). Blood contacting introducer  802  may enter perfusion lumen  202  through groove  804 . 
         [0034]      FIGS. 9A and 9B  illustrate yet another embodiment of cannula assembly  100  that allows a fluid, such as blood, to enter perfusion lumen  202 . In this embodiment, cannula body  104  includes at least one channel or groove  902  formed or cut axially along the ID of cannula body  104 . Groove  902  may extend from a position within perfusion lumen  202  to the extent of distal cannula tip  204  of cannula body  104 . Blood contacting cannula tip  204  may enter perfusion lumen  202  through groove  902 . 
         [0035]    Referring now to  FIG. 6 , a cannula body  600  with an introducer  602  is shown having a gap  604  defined between the OD of introducer  602  and the ID of cannula body  600 . In this device, gap  604  is provided to allow blood to enter cannula body  600 . However, gap  604  may create a step edge  606 , in some instances having a height of approximately 0.030 inches that may catch and damage tissue during insertion. Beneficially, in the present invention, blood is allowed to fill perfusion lumen  202  of cannula body  104  via, for example, the embodiments shown, for example, in  FIGS. 2B-2C ,  7 A- 7 B,  8 A- 8 B and  9 A- 9 B that do not create a substantial step edge. 
         [0036]    Instead, a tip transition  214  ( FIG. 2A ), defined as the point at which introducer  106  exits distal cannula tip  204  of catheter body  104 , may be made with a tapered down edge on cannula tip  204 , to provide substantially an “interference fit.” The interference fit allows tip transition  214  to be made with an outer edge profile from about 0.000 to about 0.005 inches. The low profile, tip transition  214  translates to safer insertion of cannula body  104  into diseased arteries. 
         [0037]      FIGS. 3A and 3B  are axial and perspective views of cap member  102  shown as part of cannula assembly in  FIG. 1 . Cap member  102  provides a seal between introducer  106  and cannula body  104 , such that a fluid entering cannula body  104  may be substantially maintained within cannula body  104  and perfusion lumen  202 . 
         [0038]    In one embodiment, cap member  102  includes channel vents  302  formed within the inner surface  304  of cap member  102 . As explained below, channel vents  302  provide a means for allowing air to escape from within cannula body  104 . 
         [0039]    In an operational embodiment, as shown in  FIG. 4 , cannula assembly  100  including introducer  106  is introduced into the aorta. In this embodiment, introducer  106  is inserted in a slip-lock relationship through cap member  102  into perfusion lumen  202  of cannula body  104 . Introducer  106  is moved down through perfusion lumen  202  so that distal end  206  exits the distal end of cannula body  104  (tip transition  214 ,  FIG. 2A ) to create a “tip” on the end of cannula body  104  to facilitate its entry into the aorta. 
         [0040]    Referring now to  FIGS. 2A-2C ,  3 A,  3 B,  4  and  5 , in one embodiment, as introducer  106  enters the aorta, blood B enters tip hole  208  and begins to fill central lumen  210 . The blood B continues to fill central lumen  210  until it reaches hole  212 . Blood B may then spill from hole  212  into perfusion lumen  202 , which causes perfusion lumen  202  to fill with blood B. 
         [0041]    However, in order for blood B to fill perfusion lumen  202 , air that is present inside perfusion lumen  202  needs to be vented. Otherwise, arterial pressure compresses and traps the air and the cannula body does not fill, usually requiring a surgeon to manually break a seal between the cannula body and the environment. 
         [0042]    Thus, in the present invention, air being displaced by blood B entering perfusion lumen  202  is pushed through perfusion lumen  202  until it reaches cap member  102 . As displaced air reaches the proximal end of cannula body  104 , the air is pushed out from barbed end  108  disposed within cap member  102  and allowed to vent from cap member  102  through channel vents  302 . Channel vents  302  allow blood B to escape perfusion lumen  202  and cannula body  104  as well, with minimal blood loss. Placement of channel vents  302  on the distal end of cap member  102  directs any leaking or weeping blood down and away from the clinicians at the proximal end. 
         [0043]    As shown in  FIGS. 10A-H , alternative means may be used to allow air to vent from within cap member  102  to the environment. As shown in  FIGS. 10A and 10B , cap member  102  may be formed or manufactured entirely of a porous material that allows air to permeate through the entire cap member  102 . Alternatively, only a portion of cap member may be made of the porous material or, a separately manufactured porous insert  1002  may be inserted into cap member  102 . Porous materials may include, for example, sintered plastic resin, fabric or filter membranes. 
         [0044]    As shown in  FIG. 10C , cap member  102  may be formed or manufactured having one to a plurality of pin holes  1004  that allow air to vent from within cap member  102 . In various embodiments, pin holes  1004  may be located on the top proximal surface  1006  of cap member  102  or along the axial surface  1008 . 
         [0045]    As shown in  FIGS. 10D and 10F , one to a plurality of slits  1010  may be cut into proximal surface  1006  that allow air to vent from within cap member  102 . In one embodiment, slits  1010  may be made to open wider by applying manual pressure to cap member  102 , such as by “squeezing” cap member  102 . In another embodiment, a slit  1012  may be used in place of the proximal opening  1011  of the lumen which receives introducer  106  into cap member  102 . Since slit  1012  is longer than the diameter of introducer  106 , spaces  1014  are created at the ends of slit  1012  that allow air to vent from cap member  102 . 
         [0046]    As shown in  FIG. 10F , opening  1011  of the lumen to receive introducer  106  into cap member  102  may include channels or grooves  1016  formed thereon to allow air to escape from within cap member  102 . 
         [0047]    As shown in  FIG. 10G , barbed end  108  of cannula body  104  may have channels or grooves  1018  formed or cut into the barbs to allow air to vent from cap member  102 . 
         [0048]    As shown in  10 H, introducer  106  may include one to a plurality of channels or grooves  1022  formed or cut into the proximal end of introducer  106  at a point just distal and adjacent to handle  114 . Grooves  1022  may extend into cap member  102  a distance that is appropriately determined to allow air to escape from within cap member  102  via grooves  1022 . 
         [0049]    Referring again to  FIG. 1 , in one embodiment, T-port connector  110  may include a porous material or valved assembly within cap  110   a  at the end of connector  110  that allows air to vent from perfusion lumen  202  in accordance with an alternative embodiment of the present invention. 
         [0050]    The invention has been disclosed in an illustrative manner. Accordingly, the terminology employed throughout should be read in an exemplary rather than a limiting manner. Although minor modifications of the invention will occur to those of ordinary skill in the art, it shall be understood that what is intended to be circumscribed within the scope of the patent warranted hereon are all such embodiments that reasonably fall within the scope of the advancement to the art hereby contributed, and that scope shall not be restricted, except in light of the appended claims and their equivalents.