Abstract:
A valve comprises a first housing including a first lumen extending therethrough and defining a first disk-facing surface and a second housing including a second lumen extending therethrough and defining a second disk-facing surface, the second housing being mated to the first housing so that the second disk-facing surface faces the first disk-facing surface in combination with a flexible disk gripped between gripping portions of the first and second disk-facing surfaces, the disk including a slit extending therethrough which, when acted upon by a fluid pressure of at least a predetermined threshold level opens to permit fluid flow between the first and second lumens and which, when acted upon by a fluid pressure less than the threshold level remains sealed preventing fluid flow between the first and second lumens and a relief well between opposing portions of the first and second housings radially outside the gripping portions, a width of the relief well exceeding a width of a radially outer portion of the flexible disk so that the radially outer portion of the disk is free to move therewithin.

Description:
BACKGROUND 
     Pressure activated safety valves may be incorporated into medical devices such as peripherally inserted central catheters (PICCs), ports, dialysis catheters and tunneled central catheters which provide long term access to the vascular system. Pressure activated safety valves generally include a slitted, flexible disk extending across a lumen. The flexible disk is generally constructed so that, when subjected to a threshold fluid pressure, edges of the slit separate from one another to permit flow through the lumen. When the pressure applied to the disk drops below the threshold level, the slit reseals to prevent leakage from or to the vascular access device. It would be desirable at times to employ within these vascular access devices fluid pressures in excess of the pressures to which these known flexible membranes have been traditionally exposed to with hand injections (e.g., when flushing an obstructed lumen, administering high-flow rate fluids, etc.). 
     SUMMARY OF THE INVENTION 
     The present invention is directed to a valve comprising a first housing including a first lumen extending therethrough and defining a first disk-facing surface and a second housing including a second lumen extending therethrough and defining a second disk-facing surface, the second housing being mated to the first housing so that the second disk-facing surface faces the first disk-facing surface in combination with a flexible disk gripped between gripping portions of the first and second disk-facing surfaces, the disk including a slit extending therethrough which, when acted upon by a fluid pressure of at least a predetermined threshold level opens to permit fluid flow between the first and second lumens and which, when acted upon by a fluid pressure less than the threshold level remains sealed preventing fluid flow between the first and second lumens. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a section view of a device, according to a first exemplary embodiment of the present invention; 
         FIG. 2  shows an enlarged view of the device of  FIG. 1 ; 
         FIG. 3  shows a cross-sectional side view of capture area of a device, according to a second exemplary embodiment of the present invention; 
         FIG. 4  shows a perspective view of a portion of a second housing of the device of  FIG. 3 , according to a further embodiment; 
         FIG. 5  shows a perspective view of a portion of the second housing of the device of  FIG. 3 , according to an alternate embodiment; 
         FIG. 6  shows a cross-sectional a side view of a capture area of a device, according to a third embodiment of the present invention; 
         FIG. 7  shows a cross-sectional side view of a capture area of a device, according to a fourth embodiment of the present invention; 
         FIG. 8  shows a cross-sectional side view of a capture area of the device of  FIG. 7 , according to an alternative embodiment; 
         FIG. 9  shows a cross-sectional side view of a capture area of the device of  FIG. 8 , according to a further embodiment; 
         FIG. 10  shows a cross-sectional side view of a capture area of a device, according to a fifth embodiment of the present invention; 
         FIG. 11  shows a cross-sectional side view of a capture area of a device according to a sixth embodiment of the present invention; 
         FIG. 12  shows a cross-sectional side view of a capture area of a device according to a seventh embodiment of the present invention; 
         FIG. 13  shows a cross-sectional side view of a capture area of a device, according to an eighth embodiment of the present invention; and 
         FIG. 14  shows a cross-sectional side view of a capture area of a device, according to a ninth exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The present invention relates to apparatus for controlling fluid flow through medical devices specifically for sealing devices which remain in place in the body to provide long term access to the vascular system. To improve the performance of pressure activated safety valves, embodiments of the present invention include features for fixing a disk and tuning the valve performance to withstand the increased pressures and flow rates associated with certain procedures. 
     As described in more detail below, exemplary embodiments of the present invention provide features for enhancing the performance of a pressure activated valve including a feature fixing a slitted, flexible disk in a desired position, a relief well to accommodate portions of the flexible disk moved out of the fixation area and a slit bias feature creating a bias aiding in tuning the performance of the valve (e.g., to select a threshold activation pressure). 
     As shown in  FIGS. 1 and 2 , a device  100  according to a first exemplary embodiment comprises a first housing  102  and a second housing  104  coupled to one another to hold a disk  106  therebetween. The device  100  may further comprise an additional capture component  108 , such as an o-ring. As shown in  FIG. 1 , the first housing  102  may, for example, be located at a proximal end  122  of the device  100  while the second housing  104  may be located at a distal end  124  of the device  100 . As shown in  FIG. 2 , the first housing  102  includes a lumen  110  extending therethrough and a disk-facing surface  112 . The second housing  104  includes a lumen  114  extending therethrough and a disk-facing surface  116 . It will be understood by those of skill in the art that the first housing  102  and the second housing  104  are brought together to hold a disk  106  therebetween such that a pressure activated slit in the disk is positioned between the lumens  110 ,  114  to control fluid communication therebetween. A circumference of the disk-facing surface  112  of the first housing  102  and the disk-facing surface  116  of the second housing may be substantially the same as a circumference of the disk  106  so that the first housing  102 , the second housing  104  and the disk  106  are substantially aligned within the device  100 . 
     The disk  106  may, if desired, operate as a bidirectional valve allowing fluid flow through the device  100  in either direction. Alternatively, the disk  106  may be structured or, one or both of the first and second housings  102 , 104 , respectively, may include a structure preventing the disk  106  from deforming in one direction and opening to permit fluid flow through the valve in that direction. Thus, fluid flow would be permitted only in the other direction. Fluid may be being administered to the body via the device  100  when a fluid pressure applied to the proximal end  116  of the device  100  exceeds a threshold value at which the disk  106  deforms so that the slit of the disk  106  opens to permit fluid flow therethrough to the distal end  118  of the device  100 . So long as the fluid pressure remains at least as great as the threshold level, the slit remains open and fluid passes through the disk  106  and the lumen  112  to the body. Fluid may be withdrawn from the body when a negative fluid pressure applied to the proximal end  116  exceeds the threshold level deforming the disk  106  and the slit thereof proximally to permit fluid flow from the distal end  118  of the device  100  to the proximal end  116  thereof. The fluid may be drawn from the body through the lumen  112  of the second housing  104 . This fluid flow will be maintained so long as the fluid pressure remains at least the threshold value. As soon as the fluid pressure applied against the disk  106  in either direction drops below the threshold level, the disk  106  returns to the sealed configuration in which edges of the slit therethrough abut one another preventing fluid flow therethrough. 
     The disk  106  may be flexible such that the disk  106  may be held between the first housing  102  and the second housing  104  in a substantially planar configuration or in a deformed configuration, as shown in  FIG. 2 . The capture component  108 , shown as an o-ring, may be housed between the first housing  102  and the second housing  104  such that when the disk  106  is held between the disk-facing surface  112  and the disk-facing surface  116 , an outer edge  118  of the disk  106  is deformed so that an outer edge  118  extends away from a plane of a central portion  120  of the disk  106  into a relief well  120  formed around a circumference of the disk-facing surface  112  of the first housing  102 . If it is desired to have a substantially neutral valve (i.e., a valve with substantially equal threshold pressure levels regardless of the direction of flow), the disk-facing surfaces  110  and  114 , between which the disk  106  is fixed, may be formed substantially planar to hold the central portion  120  in place without bending it in one direction or the other. It will be understood by those of skill in the art, however, that other factors such as diameter, may also affect the tuning of the valve. In addition, either or both of those portions of the disk-facing surfaces  110 ,  114  contacting the disk  106  and forming fixation features of the first and second housings  102 ,  104 , respectively, may be coated, textured, covered or overmolded with a thermoplastic elastomer or thermoset plastic such as silicone to enhance the coefficient of friction to aid in valve disk retention during high flow applications. 
     In another embodiment, the disk  106  may be non-planar. For example, rather than a planar surface as shown in  FIG. 2 , the disk  106  may have a concave or convex shape. It will be understood by those of skill in the art, however, that the disk  106  may take a variety of other non-planar shapes and forms so long as the disk  106  may be fixed between the first housing  102  and the second housing  104 . It will also be understood by those of skill in the art that the disk  106  may include more than one slit which may be pressure activated. Additionally, either of or both of the first and second housings  102 ,  104 , respectively, may include more than one lumen extending therethrough. With flow through each of these lumens controlled by separate slits or by one or more common slits extending across multiple lumens. 
     The following alternate embodiments, shown in  FIGS. 3-14 , are substantially the same as the device  100  described above, but may include alternate geometrical aspects forming the fixation feature, the relief well and the slit bias. For example, the first and second housings of the following embodiments align such that the lumen of the first housing is in fluid communication with the lumen of the second housing with a flexible disk secured therebetween so that a slit of the disk is positioned between the lumens to control fluid flow therebetween. Additionally, the figures show a capture area of the device in which the disk would be held such that the device is depicted via surfaces of a distal portion of the first housing and a proximal portion of the second housing. 
     As shown in  FIG. 3 , a device  200 , according to another embodiment of the present invention comprises a first housing  202  and a second housing  204  for securing a disk (shown in broken lines) therebetween. The first housing  202  includes a lumen  206  extending therethrough and a surface  208 , which faces a disk received in the space between the first and second housings  202 ,  204 , respectively. The surface  208  may be substantially planar so that an entire area thereof contacts the disk. The second housing  204  includes a lumen  210  extending therethrough and a surface  212  facing the space in which the disk will be received. The surface  212  may further include at least one protrusion  214  forming a fixation feature pressing against the surface  208  a portion of the disk abutting thereagainst. The protrusion  214  may be formed as an annular ring encircling the lumen  210  radially within an outer circumference  216  of the second housing  204  with a circumference greater than an inner circumference of a wall  218  of the lumen  210 . The protrusion  214  be formed by a continuous ring on the disk-facing surface  208  or, in an alternative embodiment, the protrusion  214  may be formed as a series of projections extending discontinuously around the lumen  210  (e.g., as a series of arcs extending along a curve around the lumen  210 . For example, as shown in  FIG. 4 , the non-continuous ring shape may be formed by a series of castellated teeth of the disk-facing surface  208  of the second housing  204 . In another embodiment, as shown in  FIG. 5 , the non-continuous protrusion  214  may be formed by a series of saw teeth. Such non-continuous geometries provide localized areas of grip on the disk. It will be understood by those of skill in the art that the protrusion  214  may be formed by any variety of geometrical shapes. 
     A space  220  radially outside the protrusion  214  (i.e., between the protrusion  214  and the outer circumference  216 ) forms a relief well into which a radially outer portion of the flexible disk will extend, substantially unsecured and enabled to flex accommodating the vibrations associated with high pressure fluid flow through the slit. Additionally, a space  222  radially within the protrusion  214  would allow a central portion of the disk, including the slitted portion, to flex toward the second housing  204 , until the central portion of the disk contacts the surface  212 . Thus, the device  200  will be able to withstand increased fluid pressures when fluid flows through the device in a positive direction (from the first to the second housing). It will be understood in the art, however, that the slit is not biased in any particular direction when there is no fluid flow through the device  200 . Those skilled in the art will also understand that the designation of the first housing  202  as upstream (i.e., proximal) of the second housing  204  is exemplary only and may be reversed as may the location of the protrusion  214 . That is, the second housing  204  may be formed as either the proximal or distal end of the valve of the device  200  and the protrusion  214  may be formed on either of the first and second housings  202 ,  204 , respectively, in either the proximal or the distal of the two. 
     According to another embodiment of the present invention, as shown in  FIG. 6 , a device  300 , comprises a first housing  302  and a second housing  304  for holding a flexible disk (shown in broken lines) therebetween. The device  300  is substantially similar to the device  200 , described above with the first housing  302  including a lumen  306  extending therethrough and a surface  308  which faces a space in which a disk will be received. The surface  308  includes a protrusion  310 , which may extend around the lumen  306  continuously or non-continuously as described above in regard to device  200 . As described above in regard to the protrusion  214 , the protrusion  310  has a circumference less than that of an outer circumference  312  of the first housing  302  but greater than an inner circumference  314  of the first housing  302  which forms the lumen  306 . The second housing  304  includes a lumen  316  extending therethrough and a surface  318  which faces the space within which a disk will be received. The device  300  differs from the device  200 , however, in that the surface  318  also includes a protrusion  320  which extends either continuously or discontinuously about the lumen  316 . A circumference of the protrusion  318  is less than an outer circumference  322  of the second housing  304  but greater than an inner circumference  324  of the second housing  304  which forms the lumen  316 . It will be understood by those of skill in the art that the protrusion  310  of the first housing  302  preferably substantially aligns with the protrusion  320  of the second housing  304  such that a disk held therebetween is gripped by the first and second housings  302 ,  304 , respectively, with the protrusions  310  and  320  pressing portions of the disk inward toward one another. Thus, the protrusions  310 ,  320  form a fixation feature which holds the disk therebetween. 
     When the protrusions  310 ,  312  are aligned to hold the disk therebetween, a space  326  radially outside the protrusions  310 ,  320  forms a relief well allowing an outer portion of the disk to remain substantially unsecured therein to flex in either direction (i.e., toward the first housing  302  or toward the second housing  304 ) to accommodate the vibrations associated with high pressure fluid flow. A space  328  formed radially within the protrusions  310 ,  320  (i.e., between the protrusions  310 ,  320  and the lumens  306 ,  316 ) allows a central portion of the disk, including the slitted portion, to flex to accommodate high pressure fluid flow. In other words, the central portion of the disk may flex toward the first housing  302  until the disk contacts the disk-facing surface  308  and/or toward the second housing  304  until the disk contacts the disk-facing surface  318 . Thus, it will be understood by those of skill in the art that the space  328  allows the disk to accommodate a high pressure fluid flow in either direction. However, it will also be understood by those of skill in the art, that when there is no fluid flow through the device  300 , the disk need not be biased in any particular direction, either positive or negative. 
     As shown in  FIGS. 7 and 8 , a device  400 , according to another embodiment of the present invention, comprises a first housing  402  and a second housing  404  for holding a flexible disk (shown in broken lines) therebetween. The first housing  402  includes a lumen  406  extending therethrough and a disk-facing surface  408  which includes a protrusion  410  extending from the surface  408 . The protrusion  410  extends around the lumen  406  either continuously or non-continuously in the same manner described above radially within an outer circumference  412  of the first housing  402  and radially outside an inner circumference  414  of the first housing  402  which forms the lumen  406 . An outer annular space between the outer circumference  412  and the protrusion  410  forms a relief well  428  while an annular space between the protrusion  410  and the inner circumference  414  forms a relief well  430 . The protrusion  410  may also include a pointed tip  426 , as shown in  FIG. 7 . The protrusion  410  may also be angled such that the pointed tip  426  is offset radially outward from a proximal end  432  at which the protrusion  410  meets the surface  408 . It will be understood by those of skill in the art that the pointed tip  426  may provide an improved grip of the disk  106  over a flat-surfaces protrusion  410 . 
     The second housing  404  includes a lumen  416  extending therethrough and forms a disk-facing surface  418  radially outside the lumen  416 . The disk-facing surface  418  optionally includes an indentation  420  (or a series of indentations  420  if the protrusion  410  is non-continuous) corresponding to a shape of the protrusion  410  formed on the first housing  402  and angled similarly thereto. Thus, portions of a disk received between the first and second housings  402 ,  404 , respectively, and pinched by the protrusion(s)  410  will be pushed into the indentation(s)  420 , locking the disk in position with a slit therethrough aligned with the lumens  406  and  416  while the relief wells  428  and  430  allow for flexing of the disk and the accommodation of vibrations under high pressure fluid flow. Alternatively, a device  400  may include only a protrusion  410  without a corresponding indentation  420  and the same modification may be made to any of the devices  400 ,  400 ′ and  400 ″ described below. 
     Alternatively, a device  400 ′ as shown in  FIG. 8  may include a protrusion  410 ′ and a corresponding indentation  420 ′ (or a series of non-continuous protrusions  410 ′ and indentations  420 ′) without the pointed tip of the device  400 . Specifically, as shown in  FIG. 8 , the protrusion(s)  410 ′ and the indentation(s) may be substantially rectangular in cross-section to form similar radially outer and inner relief wells  428 ′ and  430 ′, respectively. In this case, a portion of a disk received between the first and second housings  402 ′,  404 ′, respectively, will be pushed by the protrusion(s)  410 ′ into the indentation(s)  420 ′, locking the disk in position with a slit therethrough aligned with the lumens  406 ′ and  416 ′ and so that the relief wells  428 ′ and  430 ′ allow for flexing of the disk and the accommodation of vibrations under high pressure fluid flow. 
     In a further embodiment of the device  400 ″ as shown in  FIG. 9  is constructed in substantially the same manner as the device  400 ′ except that the first housing  402 ″ includes a second protrusion  434 ″ on a disk facing surface  408 ″ thereof which may be either continuous or non-continuous in the same manner described above for the protrusions of the previous embodiments while the second housing  404 ″ includes a second indentation  436 ″ on a disk-facing surface  418 ″ thereof which may correspond in shape and position to the second protrusion  434 ″. The device  400 ″ defines a radially outer relief well  428 ″ between the first protrusion  410  and an outer circumference  422 ″ of the first housing  402 ″ and a radially inner relief well  430 ″ between the second protrusion  434 ″ and the lumen  406 ″. It will be understood by those of skill in the art that the first and the second housings  402 ,  404 , respectively may include any number of protrusions and indentations as desired to more secure retain a disk gripped therebetween. 
     As shown in  FIG. 10 , a device  500 , according to another embodiment of the present invention, comprises first and second housings  502 ,  504 , respectively include disk facing surfaces  508 ,  518  respectively for holding a flexible disk therebetween. The device  500  is substantially similar to the device  400 , as described above except that, while the disk-facing surface  508  includes a protrusion  510  shaped and positioned substantially similarly to the projection  410  shown in  FIG. 7 , the disk-facing surface  518  of the second housing  504  includes no corresponding indentation and, in this case, is substantially planar such that, when a flexible disk is positioned between the first and second portions  502 ,  504 , respectively, with a slit thereof aligned with the lumens  506  and  516 , portions of the disk contacting the protrusion(s)  510  are pinched against the flat surface  518  locking the disk in position while radially outer and inner relief wells  522 ,  524 , respectively, allow for flexing of the disk and the accommodation of vibrations under high pressure fluid flow. 
     According to another exemplary embodiment shown in  FIG. 11 , a device  600  comprises a first housing  602  and a second housing  604  for holding a flexible disk (shown in broken lines) therebetween. The first housing  602  includes a lumen  606  extending therethrough and a disk-facing surface  608 . The disk-facing surface  608  includes an inner portion  610  immediately surrounding the lumen  606  and an outer portion  612  extending radially from the inner portion  610  at a distal end of the lumen  606 . The outer portion  612  may be substantially planar and oriented in any desired relationship to an axis of the lumen  606  (e.g., substantially perpendicular thereto). The inner portion  610  is angled such that a proximal opening  606 ′ of the lumen  606  is smaller than a distal opening  606 ″ thereof. That is, in this embodiment, the lumen  606  is substantially conical flaring outward distally. 
     The second housing  604  includes a lumen  614  extending therethrough to a proximal disk-facing surface  616 . The lumen  614  may for example be substantially cylindrical and approximately equal in diameter to the proximal opening  606 ′ of the lumen  606 . The disk-facing surface  616  includes a radially inner portion  618  separated from a radially outer portion  620  by a protrusion  622  which may be formed as described in regard to any of the above embodiments. The inner portion  618  is angled so that, when the first and second housings  602 ,  604 , respectively, are mated to one another with a slitted, flexible disk gripped therebetween, it is substantially parallel to the inner portion  610  of the first housing  602 . Furthermore, as would be understood by those skilled in the art, although distal opening  606 ″ is wider than the proximal opening  614 ′, the flexible disk (shown in broken lines) will preferably have a slit which is no wider than the opening  614 ′ and which, when gripped between the first and second housings  602 ,  604 , respectively, will be entirely radially within the opening  614 ′ so that fluids will pass from the lumen  606  to the lumen  614  without leaking along the inner portion  618 . 
     As in the above-described embodiments, the protrusion  622  extends continuously or non-continuously around the lumen  614  separated therefrom by the inner portion  618  and separated from an outer circumference  624  of the second housing  604  by an annular space forming a relief well  626 . It will be understood in the art that when the first and the second housings  602 ,  604 , respectively, are mated together to secure a flexible disk therebetween, the flexible disk will bend to accommodate the angled inner portions  610 ,  618  with a portion of the flexible disk secured between the outer portions  612 ,  620  fixed to the outer portion  612  of the disk-facing surface  608  by the protrusion  622 . Additionally, it will be understood by those of skill in the art that in order to accommodate the angled inner portions  610 ,  618  a central portion of the disk, including the slitted portion, bends in a proximal direction. 
     As shown in  FIG. 12 , a device  700  according to another embodiment of the invention comprises a first housing  702  and a second housing  704  for holding a flexible disk (shown in broken lines) therebetween. The first housing  702  includes a lumen  706  extending therethrough to a distal opening  706 ′ surrounded by a disk-facing surface  708 . An inner portion  710  of he disk-facing surface  708  is substantially conical, angling proximally away from the opening  706 ′ to meet a substantially planar outer portion  712  extending radially outward therefrom. The second housing  704  includes a substantially conical lumen  714  extending therethrough from a proximal opening  714 ′ to a smaller distal opening  714 ″. The proximal opening  714 ′ is surrounded by a disk-facing surface  716  separated from the opening  714 ′ by a protrusion  722 . The inner portion  718  comprises a wall immediately surrounding the lumen  714  and is shaped, for example, to correspond to the shape of the inner portion  710  of the first housing  702 . That is, in this embodiment, the inner portion  718  is angled such that the lumen  714  is recessed relative to the outer portion  720 . As in the previously described embodiments, the protrusion  722  may extend continuously or non-continuously around the opening  714 ′ within an outer circumference  724  of the second housing  704  to define a relief well  726  within which will be received a radially outer portion of a slitted, flexible disk to be gripped between the first and second housings  702 ,  704 , respectively. As described above, the disk will be pinched between the projection  722  and the outer portion  712  and between the inner portions  710  and  718  leaving the radially outer portion of the disk free to vibrate when exposed to high flow rates. 
     As will be understood by those of skill in the art, the flexible disk will bend to accommodate the angled inner portions  710 ,  718  of the disk facing surfaces  708 ,  716  creating a positive slit bias reducing the pressure required for flow proximal to distal as compared to that required for flow from the distal to the proximal. 
     As shown in  FIG. 13 , a device  800  according to another embodiment of the invention comprises a first housing  802  and a second housing  804  for holding a flexible disk (shown in broken lines) therebetween. The first housing  802  includes a lumen  806  extending therethrough and a disk-facing surface  808  including a recessed portion  810  extending around an outer-most perimeter of the disk-facing surface  808 . That is, a portion of the first housing  802  radially outside the disk-facing surface  808  is recessed away from the second housing relative to the disk-facing surface  808 . The second housing  804  includes a lumen  812  extending therethrough and a disk-facing surface  814  which includes a non-continuous or continuous protrusion  816  as described above extending around an outer-most perimeter of the disk-facing surface  814 . A radially inner surface of the protrusion  816  is radially further from the lumens  806 ,  812  than the outer perimeter of the disk-facing surface  808  so that an annular gap extends there between when the first housing  802  is coupled to the second housing  804  with a flexible disk gripped therebetween. It will be understood by those of skill in the art that although the protrusion  816  is described as formed on the disk-facing surface  814  of the second housing  804 , an o-ring may be included in the device  800  as an alternative to the protrusion  816 . In this alternative embodiment, the o-ring may be placed between the first and the second housings  802 ,  804  when the disk is being fixed therebetween in substantially the same position described for the protrusion  816 . 
     A circumference of the disk-contacting portion  818  of the disk-facing surface  808  may be smaller than a circumference of the protrusion  816  on the disk-facing surface  814  such that when the first and second housing  802 ,  804  are mated, a relief well  822  is formed by an annular space between an inner surface  824  of the protrusion  816  and an outer surface  826  of the disk-contacting portion  818 . The disk may be fixed between the first and the second housings  802 ,  804 , respectively, such that the disk-contacting portion  818  secures the disk to a disk-contacting portion  820  of the disk-facing surface  814  radially within the protrusion  816 . It will be understood by those of skill in the art that the disk may be positioned therebetween such that the disk is substantially planar or, in the alternative, such that outer edges of the disk are deformed, as shown in  FIG. 13 , by the protrusions  816 . Thus, an unsecured radially outer portion of the disk may flex within the relief well  822  to accommodate high pressure fluid flow therethrough. As the remaining portion of the disk is firmly secured between the disk-contacting portion  818  and the disk-contacting portion  820 , it will be understood by those of skill in the art that the a neutral slit bias exists, meaning that, in this embodiment, the device  800  opens to permit flow from proximal to distal at substantially the same threshold pressure as it opens to permit flow from distal to proximal. 
     As shown in  FIG. 14 , a device  900  according to another embodiment of the invention comprises a first housing  902  and a second housing  904  for securing a flexible disk (shown in broken lines) therebetween. The device  900  is substantially similar to the device  800  described above except that the first housing  902  includes a protrusion  910  extending continuously or non-continuously around an outer-most perimeter of a disk-facing surface  908  as described above while the second housing  904  includes a recessed portion  914  extending around an outer-most perimeter of a disk-facing surface  912 , radially outside a disk-contacting portion  920  of the disk-facing surface  914 . Similarly to the device  800 , the first housing  902  includes a lumen  906  extending therethrough while the second housing  904  includes a lumen  912  extending therethrough. A circumference of the disk-contacting portion  920  of the disk-facing surface  914  is smaller than a circumference of the protrusion  910  on the disk-facing surface  908  such that, when the first and second housing  902 ,  904 , respectively, are mated to one another, a relief well  922  is formed by an annular space between an inner surface  924  of the protrusion  910  and an outer surface  926  of the disk-contacting portion  920 . Thus when a disk is fixed between the first and the second housings  902 ,  904 , respectively, with the disk-contacting portion  920  securing the disk to a disk-contacting portion  918 , an outer edge of the disk is free to flex within the relief well  922  when a high pressure fluid flow passes therethrough. Similarly, it will be understood by those of skill in the art that although the protrusion  910  is described as formed on the first housing  902 , an o-ring may be included in the device  900  in place of the protrusion  910  between the first and the second housings  902 ,  904 , respectively, in the same position occupied by the protrusion  910 . 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the structure and the methodology of the present invention, without departing from the spirit or scope of the invention. For example, in any of the embodiments any of the features mentioned for a first housing may be moved to a second housing and vice versa. In addition, features mentioned with respect to controlling flow in the distal to proximal direction may be reversed to obtain the same effect in proximal to distal flow and vice versa. Thus, it is intended that the present invention cover any modifications that come within the scope of the appended claims and their equivalents.