Abstract:
A valve may include (a) a housing defining a valve lumen adapted for fluid connection with a lumen of a catheter; (b) a substantially conical valve member coupled to the housing and extending across the valve lumen to control flow therethrough; (c) a plurality of slits extending through the valve member and separated from one another circumferentially around the valve member; and (d) a ramp formed within a distal end of the valve lumen extending proximally from a distal tip of the valve member toward a ramp vertex separated from the distal tip by a predetermined distance.

Description:
PRIORITY CLAIM 
     This application claims the priority to the U.S. Provisional Application Ser. No. 60/853,917, entitled “Multi-Slit High Flow Valve,” filed Oct. 24, 2006. The specification of the above Provisional application is incorporated herewith by reference. 
    
    
     BACKGROUND 
     When repeated and prolonged access to the vascular system is required, it is often impractical and dangerous to insert and remove a needle for each session. Thus, patients are often fitted with semi-permanent catheters to facilitate vascular access and reduce discomfort. 
     When not in use, these semi-permanent catheters may be sealed, for example, by valves such as Pressure Actuated Safety Valves (PASV) which open only when fluid pressure exceeds a preselected threshold pressure. PASV&#39;s often include a slitted membrane with edges that separate from one another to open the valve only when fluid pressure applied thereto exceeds a threshold level and which are drawn together to seal the valve whenever the pressure falls below this threshold level. 
     In addition to typical fluid infusion and withdrawal procedures, certain patients require power injections of fluids to, for example, perform CT and/or MR studies. Using the same peripherally inserted central catheter (PICC) for the typical infusion/withdrawal procedures as well as the power injections simplifies these procedures. However, as power injections require considerably higher flow rates and pressures than most other procedures, using the same PICC for power injections subjects the PICC to stress levels which are not sustainable by conventional PASV&#39;s. Some recent designs of high flow membranes for PASV&#39;s have been found suitable for power injection including, for example, U.S. Published Patent Application No. 20050043703 to Greg Nordgren (“the &#39;703 application), which is hereby incorporated by reference in its entirety. The &#39;703 application describes conical, high flow rate, multi-slit membranes for PASV&#39;s. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present invention is directed to a valve comprising a housing defining a valve lumen adapted for fluid connection with a lumen of a catheter and a substantially conical valve member coupled to the housing and extending across the valve lumen to control flow therethrough in combination with a plurality of slits extending through the valve member and separated from one another circumferentially around the valve member and a ramp formed within a distal end of the valve lumen extending proximally from a distal tip of the valve member toward a ramp vertex separated from the distal tip by a predetermined distance. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an exemplary embodiment of the multi-slit high flow valve membrane according to the invention; and 
         FIG. 2  shows a second exemplary embodiment of the multi-slit high flow valve according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be further understood with reference to the following description and to the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to valves used selectively sealing a proximal end of a catheter and more specifically relates to high flow multi-slit membranes used in catheter valves. 
     When an internal shape of a conic valve mirrors the external shape (i.e., the internal space is conic), difficulties may arise when attempting to pass a guidewire through the catheter. The tips of guidewires or other instruments may become trapped in the concave vertex of the valve instead of passing through a slit. According to the exemplary embodiments of the present invention, the internal shape of the cone tip of the valve membrane is modified to divert and direct a guidewire or other instrument inserted therethrough into one of the slits. According to exemplary embodiments of the present invention, a valve membrane for a high flow PASV comprises a ramp feature within the conic tip to divert the instrument away from a vertex of the conic tip toward one or more of the slits. 
     As shown in  FIG. 1 , a high flow multi-slit membrane for use in a PASV valve  100  according to the invention comprises a tubular housing  102  with a generally conical valve member  104  extending from a distal end thereof. Those skilled in the art will understand that the valve member  104  may be integrally formed with the housing  102  or may be bonded thereto by welding, molding operations, etc. Furthermore, an outer surface of the valve member  104  preferably mates with a distal end of the housing  102  to form a smooth junction. In addition, those skilled in the art would understand that the housing  102  may be integrally formed with or connected to a catheter within which the valve  100  is to be deployed. Alternatively, the housing  102  and the valve member  104  may be located within a connector to be coupled to a proximal end of the catheter. The valve member  104  presents a concave face to flow impinging upon it from the lumen  110  of the tubular housing  102  with multiple slits  106  being formed in the membrane  104  to permit the passage of fluid when they are open. When the slits  106  are closed, the membrane  104  prevents passage of fluids therethrough. Typically, the membrane  104  and slits  106  are designed to open only when a fluid pressure exerted thereagainst is at least a desired threshold pressure. When the pressure is below this threshold pressure, the valve is closed. This valve  100  is bi-directional with the pressure required to aspirate fluids preferably being greater than that required for injection. For example, the pressure required to aspirate fluids from the valve  100  may be three times that required to inject fluids through the valve  100 . 
     In the exemplary embodiment shown in  FIG. 1 , the slits  106  extend substantially longitudinally (i.e., in a plane including a longitudinal axis of the valve  100 ) along the surface of the valve member  104 , and may be spaced evenly around a circumference thereof or in any desired pattern. The slits  106  generally do not extend into a vertex portion  108  of the member  104 , so that the member  104  remains sealed whenever the pressure is below the threshold value. A ramp  110  is formed inside the vertex portion  108  to direct objects inserted therethrough to the one or more of the slits  106 . 
     Thus, instead of becoming stuck at the vertex of the interior of the cone tip  108 , the end of a guidewire (or other instrument) encounters a surface  112  of the ramp  110  which deflects it away from the longitudinal axis of the valve  100  toward the distal ends of the slits  106 . As would be understood by those skilled in the art, the surface  112  may be formed in any shape serving to deflect an instrument inserted through the valve away from the longitudinal axis as it approaches the vertex portion  108 . For example, the surface  112  may comprise a dome shaped portion with a surface that is convex away from the cone tip  108 . 
     In addition to facilitating passage of a guidewire, valves according to the present invention improve the flow of fluid therethrough. For example, the exemplary ramp  110  eliminates a location in which blood may pool (e.g., the concavity of the vertex portion  108 ), thereby reducing the risk of thrombus formation. The improved design also promotes an optimal flow through the valve by eliminating a stagnation spot in the tip cone where the fluid flow stagnates. 
     Additional benefits of the exemplary embodiment of the valve according to the invention include increased total slit area compared to a conventional flat membrane, thus permitting the higher flow rates necessary for power injection. The exemplary valve also shows a reduced overall diameter for a given size of valve, consequently reducing the size of the housing required. In addition, as described above, the exemplary conic valve may be manufactured by molding, which is an easily repeatable and cost effective process. 
     As shown in  FIG. 3 , a valve  200  according to a second embodiment of the invention comprises a housing  202  defining a lumen  204  extending therethrough. As in the embodiment described above, a valve portion  206  of the valve  200  is generally conical in shape and, in most applications, will form the distal end of the valve  200 . A concave side of the interior of the valve portion  206  faces incoming fluid in the lumen  204  with multiple slits  208  extending through the valve portion  206  to permit flow from the lumen  204  to an exterior of the valve  200 . As described above in regard to the slits  106  of the valve  100 , the slits  208  are open only when subject to a fluid pressure of at least a threshold level and remain closed at all other times. As in the embodiment previously described, the slits  208  extend in a substantially longitudinal direction along the surface of the valve membrane  204 , converging toward a tip  210  of the cone of the valve portion  206 . Those skilled in the art will understand that a valve including only a single slit may also be employed. However, the flow rates for such single slit valves will be lower than that for multi-slit valves. In addition, the slits may be curved or in any other desired shape so long as the do not open through the distal-most tip of the housing. 
     An elongated ramp  212  which extends inside the valve portion  206  upstream from the tip  210  may be, for example, conical with a proximal tip  214  that extends proximally beyond distal ends  216  of the slits  226 . The surface  218  of the elongated ramp  212  is shaped to direct an object such as the tip of a guidewire moving distally through the lumen  204  away from the tip  210 . The slope of the surface  218  (i.e., for a conical ramp  212 , an angle of the cone) is preferably selected to direct a distal tip of an instrument inserted through the lumen  204  radially away from a longitudinal axis of the valve  200  toward the distal ends  216  of the slits  208  preventing the instrument from becoming trapped in the tip  210 . 
     As an alternative to the conic shape described for the ramp  212 , other shapes may be used to more positively guide the tip of an instrument into the slits  208 . Those skilled in the art will understand that any shape for the ramp  212  may be used which slopes toward the slits  208  to guide the tip of an instrument thereto. 
     The present invention has been described with reference to specific exemplary embodiments. Those skilled in the art will understand that changes may be made in details, particularly in matters of shape, size, material and arrangement of parts. Accordingly, various modifications and changes may be made to the embodiments. The specifications and drawings are, therefore, to be regarded in an illustrative rather than a restrictive sense.