Abstract:
A thin-walled, spiral-cut sleeve is placed on a portion of a ventricular catheter that may be moved into the compression fitting (or similar securing mechanism) of a bolt in a patient. The wall of the sleeve is sufficiently thick so as to prevent the compression fitting from collapsing the drainage lumen of the catheter. A spiral cut in the sleeve allows the sleeve to flex axially, reducing torque forces on the bolt.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to International patent Application No. PCT/US2010/023777, International Filing Date 10 Feb. 2010, entitled Flexible Anti-Collapsible Catheter Sleeve, which claims priority to U.S. patent application Ser. No. 12/431,631 filed Apr. 28, 2009 entitled Flexible Anti-Collapsible Catheter Sleeve (now abandoned), which claims priority to U.S. Provisional Application Ser. No. 61/151,415 filed Feb. 10, 2009 entitled Flexible Anti-Collapse Catheter Sleeve, all of which are hereby incorporated herein by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Ventricular catheters are typically used for monitoring pressure and draining fluid (e.g., cerebrospinal fluid) in mammalian bodies, an example of which is seen in U.S. Pat. No. 6,673,022, the contents of which are incorporated by reference. Hence, these catheters typically have one or more passages within them to allow for drainage, air communication, wires or other components. 
         [0003]    The ventricular catheter for intracranial use is typically fixed in place with a bolt and compression fitting. One end of the bolt is screwed into or otherwise fixed in the skull of a patient and the other end of the bolt connects to the compression fitting. Once the catheter has been placed in the brain, the compression fitting is tightened to fix the location of the catheter relative to the bolt to prevent axial movement of the catheter within the patient. Since the compression fitting applies pressure to a portion of the catheter, an exoskeleton or similar rigid support structure must be placed over any portion of the catheter that may be contacted by the compression element. This exoskeleton or rigid support structure prevents the catheter&#39;s lumen (e.g., such as a drainage lumen) from collapsing. 
         [0004]    Previous exoskeleton designs have employed a rigid sleeve or support tube fixed over that portion of the catheter that may be subjected to the force of the compression fitting. This rigid sleeve prevents collapse of the catheter lumens but also remains relatively unbendable. In this respect, the rigid tube maintains the orientation of the catheter in line with the axis of the passage through the bolt and compression fittings. Since the length that the catheter that must be advanced into the brain varies from person to person, the rigid tube must be long enough to accommodate these various catheter positions. Hence, the rigid tube causes at least a portion of the catheter to rigidly stick up from the bolt and compression fitting. 
         [0005]    In some arrangements of this system, the bolt, fitting and catheter can rigidly extend away from the patient for some distance. For example, the bolt and fitting may extend above the scalp about 1.5 inches while the rigid tube extends above the bolt by another 1 inch. 
         [0006]    This combined length of the bolt, the fitting and the rigid tube is problematic for at least two reasons. First, it increases the likelihood that the assembly will be inadvertently hit. For example, the catheter provides a longer and more rigid area for a nurse or agitated patient to contact. 
         [0007]    Second, the length of the tube increases the length of the lever arm which conveys torque to the skull. In this respect, the force of contact from the rigid tube is much greater than it would be against the bolt alone. In some cases, the torque increase allows even a relatively minor force to pop out the bolt from the skull, causing serious complications. 
         [0008]    In addition to torque forces, the increased area of the rigid tube may increase the likelihood of applying downward, axial force on the catheter. This force may overcome the holding force of the compression fitting, pushing the catheter into the patient&#39;s brain and likely causing damage. 
       SUMMARY OF THE INVENTION 
       [0009]    According to a preferred embodiment of the present invention, an exoskeleton consisting of a thin-walled spiral-cut sleeve or series of rings is placed on a portion of a ventricular catheter that may be moved into the compression fitting (or similar securing mechanism) of a bolt in a patient. The exoskeleton prevents the compression fitting from collapsing the lumens (e.g., the drainage lumen) of the catheter. Spacing between the rigid areas (such as a spiral cut) allows the exoskeleton to flex axially so that the catheter can bend freely. The flexibility of the exoskeleton lowers the profile of the system and precludes the possibility that a downward force on the catheter will push the catheter into the brain. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other aspects, features and advantages of which embodiments of the invention are capable of will be apparent and elucidated from the following description of embodiments of the present invention, reference being made to the accompanying drawings, in which 
           [0011]      FIG. 1  illustrates a catheter and exoskeleton according to the present invention; 
           [0012]      FIG. 2  illustrates the catheter and exoskeleton of  FIG. 1  with a bolt and compression fitting; 
           [0013]      FIG. 3  illustrates a magnified cross sectional view of the compression fitting from  FIG. 2 ; 
           [0014]      FIG. 4  illustrates the catheter, exoskeleton, bolt and compression fitting of  FIG. 2 ; 
           [0015]      FIG. 5  illustrates the exoskeleton of  FIG. 1 ; 
           [0016]      FIG. 6  illustrates the exoskeleton of  FIG. 5  in a bent configuration; and 
           [0017]      FIG. 7  illustrates an exoskeleton according to the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0018]    Specific embodiments of the invention will now be described with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. The terminology used in the detailed description of the embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, like numbers refer to like elements. 
         [0019]    Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0020]      FIGS. 1 and 2  illustrates a catheter  100  having a flexible exoskeleton  102  that allows the catheter  100  to freely bend while preventing the interior contents of the catheter  100  from being crushed by a fastening mechanism such as a compression fitting  114 . The exoskeleton  102  reduces the height and therefore the torque that forces (such as accidental contact) can exert on the bolt  116 . Hence, the risk of popping out the bolt  116  from, for example, the patient&#39;s skull, is greatly reduced. 
         [0021]    Preferably, the exoskeleton  102  can be an integral part of the catheter  100  by, for example, adhesive bonding. 
         [0022]    As seen in the present example, a distal section  106  of the catheter  100  includes a plurality of drainage apertures which connect to a drainage passage within the catheter  100 . The catheter  100  preferably includes a pressure sensor  104  for measuring a pressure within a patient. A tube  108  within which the pressure signal is conveyed, splits off from the catheter  100  at splitter  112 . The proximal end of the catheter is terminated in a luer fitting  110 . The luer fitting is connected to a standard drainage bag system (not shown). 
         [0023]    As best seen in  FIG. 2 , the exoskeleton  102  is located along a length of the catheter  100  where a compression fitting  114  or similar position fixing mechanism may press against or otherwise compress the catheter  100 . Since different patients and different insertion locations may require the catheter  100  to be inserted to different depths, the flexible region extends along much of the length of the catheter  100 . Preferably, this exoskeleton  102  length is about 4 inches. 
         [0024]      FIG. 4  illustrates the exoskeleton  102  and catheter  100  in a bent or flexed position proximal to the bolt  116  and compression fitting  114 . As compared with the non-flexed position in  FIG. 2 , the exoskeleton  102  reduces torque-amplified forces on the bolt  116  and compression fitting  114  (coupled to the bolt  116 ) that would otherwise be present if the exoskeleton  102  was non-flexible (as in the prior art). 
         [0025]      FIG. 3  illustrates a magnified view of a typical compression fitting  114 . As the upper portion  120  is screwed onto the lower portion  122 , an inner member  119  presses down on a compression element  118 . As the compression element  118  is compressed or squeezed downwards, it expands outward against the exoskeleton  102  of the catheter  100 . Additionally, a set screw  124  can be further used to further secure the exoskeleton  102  from axial movement. 
         [0026]    As previously discussed, prior art exoskeletons are rigid, especially along the length that is squeezed or pressed on by the compression fitting  114 . This leaves the prior art exoskeletons unable to bend. However, the exoskeleton  102  resists crushing while allowing flexibility (i.e., axial flexibility along a length of said exoskeleton  102 ) by preferably includes a plurality of rigid sections or areas that are interspersed with non-rigid areas or even no material. These rigid sections can be connected together as a unitary rigid element or can be distinct from each other. The rigid sections are arranged along the length of the exoskeleton  102  to withstand being crushed by a radial force typically generated by a compression fitting  114 . Spaces between the rigid sections allow the exoskeleton  102  to flex as needed. 
         [0027]      FIGS. 5 and 6  best show a preferred embodiment of the flexible exoskeleton  102 , including a spiral cut  102 A forming a generally larger spiral of rigid material  102 B. This spiral cut  102 A introduces axial flexibility into the exoskeleton  102  while retaining much of the strength along the diameter to resist crushing under pressure from the compression fitting  114 . 
         [0028]    The width of the rigid material  102 B can be varied to increase or decrease the crush resistance and flexibility of the exoskeleton  102 . Generally, the flexibility can be increased and the crush resistance can be decreased by increasing the number of turns in the spiral cut  102 A. Conversely, the crush resistance can be increased and the flexibility can be decreased by decreasing the number of turns in the spiral cut  102 A. Preferably, the flexible section  102  sized to fit an 8 French catheter is composed of a rigid material such as polyimide with a thickness of about 0.006″. The spiral cut  102 A is preferably about 0.01″ wide and forms about 10 turns per inch. 
         [0029]    Preferably, the exoskeleton  102  can be formed by cutting the spiral cut  102 A into the tube via a laser or mechanical cutting device. Alternately, this spiral shape can be preformed by molding techniques. 
         [0030]    While a spiral cut  102 A has been described, it should be understood that other cut shapes are contemplated within the present invention. For example, right angle cuts forming a stair pattern, a spiral wave pattern, a circumferential wave pattern, or similar variations on these patterns. 
         [0031]      FIG. 7  illustrates another preferred embodiment of an exoskeleton  130  that includes a plurality of rigid rings  130  (some of which are shown cross sectioned in this figure) which are fixed in place by a flexible tube  130 B. The rings  130  are preferably composed of a rigid polyimide or metal and are preferably adhered or embedded within the flexible tube  130 B. The flexible tube  130 B is preferably composed of a flexible plastic. Alternately, the rings  130  may be only connected by a plurality of longitudinal wires connected to the inner or outer diameter of the rings  130 A or may simply be adhered to the exterior of the catheter  100  in a evenly spaced arrangement. 
         [0032]    Although the invention has been described in terms of particular embodiments and applications, one of ordinary skill in the art, in light of this teaching, can generate additional embodiments and modifications without departing from the spirit of or exceeding the scope of the claimed invention. Accordingly, it is to be understood that the drawings and descriptions herein are proffered by way of example to facilitate comprehension of the invention and should not be construed to limit the scope thereof.