Abstract:
An infusion set includes a needle hub with a needle to be inserted in a through passageway of the cannula housing through a sealing surface of a soft cannula. The infusion set includes a guide for centering the needle relative to the cannula sealing surface, a dirt trap, and the through passageway, as well as a locking device for locking the cannula housing and the needle hub together to prevent inadvertent disengagement. The guide includes co-operating guide pins and guide openings and a draft angle on the needle hub. The pins are located on each side of the needle and the through passageway. The connecting tube includes an inner tube of polyethylene and shrink fitted tubing at each end suitable for a solvent bonding layer. The composite can be reinforced with monofilament strands sandwiched between the two tubular layers to prevent kinking, or the inner tube can be formed in a triangular shape. The triangular shape composite is incased in a thin polyester shrink tube.

Description:
The present application is related and claimed priority to U.S. application Ser. No. 60/195,702, filed Apr. 7, 2000, by Joel Douglas, U.S. application Ser. No. 60/188,624, filed Mar. 13, 2000, by Joel Douglas, and U.S. application Ser. No. 60/176,538, filed Jan. 18, 2000, by Joel Douglas, the entire contents of each of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to medical connectors and infusion sets. 
     2. Brief Description of the Related Art 
     In general, whenever a therapeutic fluid is to be delivered subcutaneously to a patient form an external source, a passageway, such as that provided by a hollow needle or other type of cannula or catheter device, must be first inserted through the skin of the patient in order to provide a passageway or channel through which the fluid may pass from its source external to the patient to the desired subcutaneous location under the skin of the patient. Once this passageway has been installed, the desired infusion system may be used in conjunction with an appropriate catheter connecting the external source of fluid with the passageway leading to the subcutaneous delivery point to deliver the fluid to the patient at an appropriate delivery rate. 
     Unfortunately, several problems associated with infusing fluids into the patient as described above are usually encountered. Most systems require the patient to use a syringe that is fitted with a thread or luer fitting. The patient must fill the syringe and attach the catheter to it. However, in doing so the medication can become contaminated and is therefore no longer sterile. Non-sterile solutions can lead to infection. In addition the inconvenience of having to fill the syringe in the first place, and then attach and prime the catheter is difficult for many patients. 
     In the early 1990&#39;s prefilled insulin cartridges were first introduced by insulin manufacturing companies for use in insulin pens. These cartridges are prefilled and make their use very convenient for the patient. The difficulty is that the prefilled cartridges need to have a septum to allow the medication to remain sterile. 
     The recent popularity of insulin infusion pumps as an alternative to multiple daily injections for insulin-dependent diabetics requires the use of such an injection set to deliver insulin from a small, portable insulin infusion pump to the subcutaneous injection location. However, these devices require the patient to fill a syringe, which defeats the sterility of the mixture. Furthermore, there exists a substantial problem with the use of injection sets, as described above, in that flexible PVC is not completely insulin-compatible. This is in contrast to hard PVC, which is safe for use with insulin. While the exact nature of the reaction exhibited by insulin in contact with flexible PVC has not been determined with certainty, it is believed that the insulin, which is pH sensitive, reacts with CO 2 , the flow of which therethrough is not inhibited by flexible PVC. In addition, the large quantities of plasticizer used in flexible PVC may result in a leaching problem when used with insulin. 
     Since flexible PVC is not a barrier for CO 2 , the CO 2  which flows through the flexible PVC tubing will react with the insulin, causing the insulin to aggregate and to precipitate out of solution. Such precipitation of the insulin will likely cause clotting and blockage in the tube or in the needle, thereby inhibiting the flow of insulin to the subcutaneous depot. 
     Heat will also accelerate the clotting process of insulin in flexible PVC tubing without the pH change caused by CO 2 . The reason for this has not been finally determined, but it may be due to zinc in the insulin forming zinc chloride. In any event, heat will further compound the situation faced by delivery of insulin through flexible PVC tubing. 
     The amount of insulin exiting the injection set will therefore vary considerably, with portions of the insulin becoming attached to the interior of the tube and eventually coating the interior of the tube, even if blockage does not occur. Over time, the situation will improve somewhat assuming blockage of the tube per se does not occur, but the amount of insulin actually delivered to the patient will vary considerable even with the best of circumstances. It may therefore be appreciated that the use of a flexible PVC tubing injection set to deliver insulin from an insulin infusion pump is neither desirable nor medically acceptable. 
     Other substances exhibit reactions when delivered through flexible PVC tubing. Lipids and proteins have adverse reactions with flexible PVC delivery systems, and nitroglycerin also reacts to some degree with a flexible PVC environment. 
     One solution which has been proposed to the problem has been through the use of polyethylene tubing, which does not cause a reaction with insulin passing therethrough. Polyethylene is a barrier to CO 2 , and the major problem of CO 2  passing through the tubing is thereby eliminated. Additionally, the problem of clotting of the insulin due to heat is also substantially minimized. 
     Several problems have arisen with the use of epoxy bonded polyethylene infusion sets, all of which are due to the relative disadvantage of the epoxy bonding process to a solvent bonding process. First of all, an epoxy bond is simply not as strong as a solvent bond. Secondly, epoxy bonds have substantial aging problems, which limit shelf life of the injection set. Since the epoxy bond loses its mechanical bonding properties over time, the injection set will become less sturdy, with the potential for the tubing coming loose from the needle increasing substantially over time. Thirdly, batch control of epoxy used in epoxy bonding is time consuming and cumbersome. Finally, epoxy bonding or “potting” is a more expensive process than solvent bonding, resulting in a product having an economic disadvantage relative to a product made by solvent bonding. 
     It is thereby apparent that there exists a substantial need for an injection set for delivery of insulin (or other fluids exhibiting reactions when flowed through flexible PVC tubing), which injection set utilizes polyethylene tubing to inhibit reaction and subsequent degradation of insulin flowing therethrough. 
     SUMMARY OF THE INVENTION 
     According to a first exemplary embodiment, a medication infusion set comprises a base tube having an exterior surface, a proximal end, a distal end, and an inner lumen extending between the proximal and distal ends, the base tube formed of a material selected from the group consisting of polyethylene and polypropylene, a rigid cannula having a proximal end, a distal end, and a lumen extending between the proximal and distal ends, the cannula proximal end positioned in the base tube lumen, and a tube of a heat shrinkable material positioned on the base tube exterior surface at least in a region of the base tube in which the cannula is inserted, the heat shrinkable tube having been heat shrunk to the exterior of the base tube and compressing the base tube and the cannula together to form a seal. 
     According to a second exemplary embodiment, an infusion device comprises a housing including a proximal end, a distal end, two lateral sides, and a bore extending between the proximal end and the distal end, a soft cannula having a proximal end, a distal end, and a lumen extending between the proximal end and the distal end, the cannula positioned in part in the housing bore with the cannula distal end outside of the housing, and a locking device attached to a lateral side of the housing, the locking device including a locking finger and a lever, the lever extending distally and the locking finger extending proximally, the locking finger including a distally facing surface. 
     According to a third exemplary embodiment, a connecting device comprises a hub including a proximal end face, a distal end face, two lateral sides, and a bore extending between the proximal end and the distal end, rigid cannula including a proximal end, a distal end, and a lumen extending between the proximal end and the distal end, the rigid cannula mounted in the hub bore with the rigid cannula distal end exterior of the hub, a pin extending distally from the hub distal end face and offset laterally from the rigid cannula, and a proximally facing surface on one of the lateral sides positioned between the proximal end face and the distal end face. 
     According to a fourth exemplary embodiment, a process of forming a medical infusion set comprises the steps of inserting an end of a rigid cannula into the lumen of a length of tubing, and heat shrinking a tube of heat shrinkable material over the portion of the tubing in which the end of the rigid cannula is positioned to compress the tubing onto the rigid cannula. 
    
    
     Still other objects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention of the present application will now be described in more detail with reference to preferred embodiments of the apparatus and method, given only by way of example, and with reference to the accompanying drawings, in which 
     FIG. 1 illustrates a perspective view of a first embodiment of an infusion set and connector in accordance with the present invention; 
     FIG. 2 illustrates a longitudinal cross-sectional view of the set of FIG. 1; 
     FIGS. 3 and 4 illustrate top plan views, with portions broken away in FIG. 4, of another embodiment of an infusion set in accordance with the present invention 
     FIG. 5 is a top plan view of a portion of the devices illustrated in FIG. 4; 
     FIG. 6 is a front elevational view of the device in FIG. 5; 
     FIG. 7 is a rear (upsidedown) elevational view of the device in FIG. 5; 
     FIG. 8 is a left side elevational view of the device in FIG. 5; 
     FIG. 9 is a cross-sectional view, taken at line  9 — 9  in FIG. 5; 
     FIGS. 10 and 11 illustrate enlarged views of portions of the device illustrated in FIG. 5; 
     FIG. 12 illustrates a top plan view of a portion of the device illustrated in FIG. 4; 
     FIG. 13 illustrates a side elevational (upsidedown) view of the portion in FIG. 12; 
     FIG. 13 a  illustrates another portion of the device in FIG. 12; 
     FIG. 14 illustrates a front elevational view of the device in FIG. 12; 
     FIG. 15 illustrates a top plan view of an insertion device in accordance with the present invention; 
     FIG. 16 illustrates a side elevational view of the device illustrated in FIG. 15; 
     FIG. 17 illustrates a top plan view of a plug in accordance with the present invention; 
     FIG. 18 illustrates a front elevational view of the plug illustrated in FIG. 17; 
     FIG. 19 illustrates a cross-sectional view taken at line  19 — 19  in FIG. 18; 
     FIG. 20 illustrates a longitudinal cross-sectional view of a cannula in accordance with the present invention; 
     FIG. 21 illustrates a perspective view of a pen needle in accordance with the present invention; 
     FIG. 22 illustrates a longitudinal cross-sectional view of the pen needle illustrated in FIG. 21; 
     FIG. 23 illustrates yet another device in accordance with the present invention; 
     FIG. 24 illustrates a perspective view of a portion of the device illustrated in FIG. 23; 
     FIG. 25 illustrates a longitudinal cross-sectional view of the portion of FIG. 24; 
     FIG. 26 illustrates a portion of the device illustrated in FIG. 25; 
     FIG. 27 illustrates yet another aspect of the present invention; 
     FIG. 28 illustrates an enlarged top plan view of a portion of the device illustrated in FIG. 23; 
     FIG. 29 illustrates a side view, partially in cross-section, of the portion illustrated in FIG. 28; 
     FIG. 30 illustrates a longitudinal cross-sectional view along line  30 — 30  in FIG. 29; 
     FIG. 31 illustrates a cross-sectional view of a tube in another aspect of the present invention; 
     FIGS. 32 and 33 illustrate yet further aspects of the invention; and 
     FIGS. 34 and 35 illustrate portions of a device in accordance with the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures. 
     The present invention relates to a disposable injection set that offers the ability for the patient to infuse from a prefilled insulin cartridge without compromising the sterility of medication to be infused. Also, utilization of prefilled medication cartridges to provide a source of infusion material makes it easy and convenient to use by the average patient. The utilization of a cannula to pierce the septum of the medication cartridge provides the sterile means for connecting the catheter to the cartridge and by combining it with the soft or flexible catheter with needles fixed on both ends permits the development of a convenient and sterile infusion device. The cannula that is inserted into the skin of a patient is held at its insertion location with a low profile holding pad or housing. The opposite end has a threaded connector with a cannula fixed in it that permits communication between the fluid in the reservoir and the catheter. The cannula on the threaded connector is positioned so that the tubing of the catheter is fixed over the cannula and attached by adhesive to the catheter tubing. The adhesive is selected from a set of epoxies or solvent adhesive that are capable of bonding to the soft tubing. The adhesive needs to create the appropriate bond and be capable of being sterilized. The solvent bondable shrink tube is then placed over the end of the tube and heated to produce a secure joint, and the adhesive is applied to the outer surface of the shrink tube and inserted into the connector. 
     Turning now to the drawing figures, FIGS. 1 and 2 illustrates a perspective view and a longitudinal cross-sectional view, respectively, of a first embodiment  100  of an infusion apparatus in accordance with the present invention. Generally, the apparatus  100  includes a medication delivery device  102 , into which a medication ampule  108  is releasably installed, and a catheter infusion set  104 . The medication delivery device  102  can be any of numerous such devices which receive a medication ampule  108 , including “pen” type injectors, programmable medication pumps, and those described in U.S. application Ser. No. 60/156,535, filed Sep. 29, 1999, U.S. application Ser. No. 60/170,570, filed Dec. 13, 1999, U.S. application Ser. No. 60/177,762, filed Jan. 24, 2000, and filed Sep. 29, 2000, “Reusable Medication Delivery Device”, to Joel Douglas et al., the entire contents of each of which are incorporated by reference herein. 
     The device  102  includes a holder  106  which releasably holds the medication ampule  108  therein so that the ampule&#39;s septum  112  is exposed and accessible to be pierced and accessed in a known fashion. Similarly, the piston  110  of the ampule  108  is accessible so that it can be moved to expel medication from the ampule, again in a known fashion. The device  102  includes external threads  114  so that a medical connector, described in greater detail below, can be releasably attached to the device to access the ampule&#39;s contents through the septum  112 . 
     The catheter infusion set  104  includes a proximal connector  116  having a cylindrical collar or shroud  118 , which has internal threads  120  which mate with external threads  114 . A piercing element  122 , e.g., a needle, extends proximally from the connector  116 . A distal catheter, cannula, needle, or other tubular element  124  extends from the distal end of the set  104 , and is in fluid communication with the piercing element  122  via a tube  130 . As can be seen in FIG. 1, the catheter  124  extends at an angle a to the longitudinal axis of the device (when laid straight). Angle a is preferably between about 15 degrees and about 90 degrees, and more preferably is about 30 degrees, so that the catheter can reside comfortably in the subcutaneous tissue layers of a patient. A holding pad  126  having an adhesive face  128  is connected to the catheter  124  by any of numerous ways, preferably by an adhesive  136  (see FIG.  2 ). At the proximal end of the set  104 , the tube  130  is secured to a distal portion  138  of the connector  116 . 
     As discussed above, the materials used for tube  130  effect the way that the connection between the tube and the connector  116  can be made. According to one aspect of the present invention, a tube  132  is heat shrunk over the exterior of the tube  130  in the area where the distal portions of piercing element  122  extend into the lumen of the tube  130 . In one aspect of the invention, the tube  132  secures the piercing element  122  and the tube  130  together. In another aspect, the tube  132  presents an outer surface to which the distal portions  138  of the connector  116  can be solvent bonded, as at  134 , which outer surface is different from that of the tube  130 . The tube  132  can extend only a short way distally along tube  130 , or can extend distally along the entire length of tube  130 . According to other aspects of the present invention, tube  132  can be formed of any of a number of materials which permits good solvent bonding to the connector  116 , such as PVC, polyester, or PTFE. 
     The operation of the exemplary embodiment of the present invention described above and illustrated in FIGS. 1 and 2 will now be described with reference thereto. A user or patient inserts a medication ampule  108 , such an insulin cartridge, into the delivery device  102 , with the ampule&#39;s septum  112  accessible through the device. The collar  116  is screwed or otherwise placed over the end of the device  102  so that the piercing element  122  pierces the septum  112  and places the interior of the ampule in fluid communication with the cannula  124 . The user can then prime the set  104 , if desired. If the set  104  is already in place subcutaneously, the user manipulates the device  102  to move the piston  110  to deliver an amount of medication to the patient through the cannula  124 . 
     FIGS. 3 and 4 illustrate top plan views, with portions broken away in FIG. 4, of another embodiment  200  of an infusion set in accordance with the present invention. Set  200  includes a cannula housing  202  which holds a soft cannula  204  for positioning subcutaneously in a patient. A connecting hub  206  is releasably positioned to the proximal end of the cannula housing  202 . A length of tubing  208  preferably flexible, is secured to the proximal portions of the connecting hub. A proximal connector  210  is secured to the proximal end of the tubing  208 . The connector  210  includes a cylndrical collar or shroud  212 , a hub  222 , and a piercing element  214 . A distal portion  226  of the piercing element  214  extends proximally through the hub  222  and is in fluid communication with the tubing  208 . An extension  216  of the connector  210  extends around the proximal portions of the tubing  208  and connects the tubing to the connector  210 . In one aspect of the present invention, a shrink tube, such as tube  132  described above, is inserted into extension  216  to facilitate bonding. 
     The connecting hub  206  includes distally extending pins  216 ,  218  which are inserted into and mate with complementarily placed and configured holes or bores in the cannula housing  202 , described in greater detail below. A distally extending hollow tube  220  extends from the connecting hub  206 , and includes proximal portions  224  which are in fluid communication with tubing  208 . The proximal portions  224  can be secured to the tubing  208  in any suitable manner, including utilizing a shrink tube such as tube  132  and solvent bonding. Hollow tube  220  may be sharpened at its distal most end, e.g., be a needle, or can alternatively be blunt. 
     Turning now to FIGS. 5-9, several views of the cannula housing  202  are illustrated. Specifically, FIG. 5 is a top plan view of the cannula housing; FIG. 6 is a front elevational view; FIG. 7 is a rear (upsidedown) elevational view; FIG. 8 is a left side elevational view; and FIG. 9 is a cross-sectional view, taken at line  9 — 9  in FIG.  5 . 
     The cannular housing  202  include a generally frustoconical, distally extending portion  230 , through which a bore  232  extends. The bore  232  is widened at its distal end to form a cannula recess  234 , for reasons which will be discussed further below. The proximal end of the bore  232  widens in a frustoconically shaped proximal portion  236 . The proximal portion  236  is tapered in order to guide a tube, such as tube  220 , when inserted into the bore  232  through proximal opening  238 . The housing  202  also includes blind bores for receiving the pins from the connecting hub. When there are two pins,  216  and  218  as illustrated in FIG. 3, there are two such blind bores  244 ,  246 , which are sized and positioned to receive the pins. As will be readily appreciated by one of ordinary skill in the art, while one such pin-bore combination is less preferable because it guides the housing  202  and hub  206  together less effectively, and more than two pin-bore combinations may provide better registration between the hub and the housing, any number of pins and bores are within the spirit and scope of the present invention. 
     The proximal end of the housing  202  includes a pair of guide extensions  242 , one on each lateral side of the housing, which together delimit an open proximal space  240  sized and shaped to receive portions of the connecting hub  206 . Each guide extension  242  includes an laterally inwardly directed, slightly tapered guide surface  248 ,  250 . The guide surfaces  248 ,  250  are sized and oriented so that they provide initial guidance to the outer surfaces of the hub  206  when the hub and housing  202  are brought together, described in greater detail below. 
     The housing also includes at least one, and preferably two locks  252 ,  254 , positioned on the lateral sides of the housing. The locks  252 ,  254  are provided to releasably lock the hub  206  to the housing  202  when the hub and housing are properly mated together (see FIG.  4 ). The locks  252 ,  254  include releasable locking fingers  256 ,  258  which extend proximally from regions where the locks join with the housing  202 . The fingers  256 ,  258  include a locking bearing surface  260  which is distally directed for bearing against portions of the hub  206  which face proximally (again, see FIG.  4 ). Adjacent to the locking bearing surface(s)  260 , each finger  256 ,  258  is provided with an angled cam surface  262 . The cam surfaces provide a place for the connecting hub  206  to bear against the fingers  256 ,  258  and push them laterally outward, to spread the fingers and permit the connecting hub to enter the space  240  when moved distally relative to the housing  202 . 
     The locks  252 ,  254  also include levers  264  ion their proximal ends, opposite the fingers  256 ,  258 . The cantilevered levers  264  are positioned laterally spaced from the housing  202  so that there are spaces  266  between the levers and the housing into which the levers can be flexed. Flexure of the levers  264  laterally inward cause the fingers  256 ,  258  to flex laterally outward, thus permitting the connecting hub  206  to enter and exit the space  240  more easily. As will be readily appreciated by one of ordinary skill in the art, pulling proximally on the connecting hub  206 , when positioned in the space  240 , with sufficient force will also result in the fingers  256 ,  258  spreading apart and the hub being released from the housing  202  and the locks  252 ,  254 . 
     As illustrated in FIGS. 6,  8 , and  9 , the soft cannula  204 , in some aspects of the present invention, is angled relative to the bottom surface  268  of the housing  202  at an angle β, wherein β can be any acute angle, and can be the same as α. 
     FIGS. 10 and 11 illustrate enlarged views of portions of the connecting hub  206 . Specifically, FIG. 10 illustrates the locks  254 , including the channel  270  between the finger  258  and the housing  202 . FIG. 11 illustrates the bore  232 , without the soft cannula  204  positioned in the bore. 
     FIGS. 12-13 a  illustrate the connecting hub  206 . More specifically, FIG. 12 illustrates a top plan view of the connecting hub  206 ; FIG. 13 illustrates a side elevational (upsidedown) view; FIG. 13 a  illustrates a portion of the hub; and FIG. 14 illustrates a front elevational view. As discussed above, pins  216 ,  218  and tube  220  extend from the hub  206 . The hub  206  includes locking surfaces  280  which are oriented and positioned so that the bearing,surfaces  260  of the locking fingers  256 ,  258  will bear against the locking surfaces  280  when the hub is positioned in the space  240 . Cam surfaces  282  are also provided on the distal end of the hub  206  to bear against the cam surfaces  262  of the fingers  256 ,  258 , as described above. 
     The hub  206  includes a proximal portion  284  to which the tubing  208  is attached, preferably in a permanent manner. A longitudinally extending lumen or bore  286  extends from the proximal end to the distal end of the hub  206 . The lumen is sized to receive the tubing  208  therein, with the proximal end  224  of the tube  220  in fluid communication with the lumen of the tubing. Although a straight bore  286  can be used, it is preferable that the bore include a shoulder  292  along its length, with a proximal portion  288  and an intermediate portion  290  on either side of the shoulder. The intermediate portion  290  can be of a smaller inner diameter than the proximal portion  288  so that the tubing  208  is radially compressed. Intermediate portion  290  can also have a slightly tapered inner diameter, so that the radial compression of the tubing is greater at the shoulder than elsewhere along the bore  286 . The bore  286  also includes a distal portion  296 , in which a needle hub or positioning block  294  is mounted. 
     FIG. 13 a  illustrates that, in one aspect of the invention, the block  294  can have a beveled side  300  to assist in aligning the tube  220  at the same angle as the soft cannula  204 . FIGS. 13 and 14 illustrate that the hub  206  can optionally have a slanted top surface  298 . 
     FIGS. 15 and 16 illustrate a top plan view and a side elevational view, respectively, of an insertion device  302  used to insert the soft cannula into the patient, preferably subcutaneously The device  302  includes a needle or stylet  304  extending distally from an insertion handle  306 . The insertion handle  306  is substantially the same shape and size as the hub  206 , and includes a pair of pins  308 ,  310 , substantially similar to pins  216 ,  218  . The needle or stylet  304  is of a length so that the sharpened distalmost end of the needle or stylet extends beyond the distalmost end of the soft cannula  204  when the insertion handle  306  is mounted on the housing  202 , in the same manner as the connecting hub  206  is mounted to the housing in FIG. 4. A proximal end of the needle or stylet  304  is preferably within the handle  306 . According to yet another aspect of the present invention, the needle  304  can include a score line  314  along its length so that the needle can be broken off and used as an infusion needle. The handle  306  would then require a lumen similar to lumen  286  in FIG.  12 . 
     FIGS. 17-19 illustrate several views of a plug in accordance with one aspect of the present invention. More specifically, FIG. 17 illustrates a top plan view of a plug  330 ; FIG. 18 illustrates a front elevational view of the plug, and FIG. 19 illustrates a cross-sectional view taken at line  19 — 19  in FIG.  18 . The outside size and shape of plug  330  is the same as the insertion handle  306  and the connecting hub  206 , described above. The plug  330  includes a pair of pins  332 ,  334  to mate with blind bores  244 ,  246 , described above. The plug  330  includes a central plugging element  336  having a preferably conical or frustoconical tip  338  extending distally from the plugging element  336 . The plugging element  336  is formed of a somewhat soft material which is somewhat compressible, so that when the plug  330  is mounted to the housing  220  in the manner of hub  206  and handle  306 , the plugging element will enter into and seal the proximal portions of bore  232 . By way of example and not of limitation, element  338  can be formed of a medical grade silicon rubber. Thus, the plug  330  can be used to seal the bore  232 , and therefore access to the patient&#39;s body by dirt and pathogens is greatly restricted when connecting hub  206  is disconnected from the housing  202 . 
     The size and taper of plugging element  336  and tip  338  are preferably selected to plug and seal with tapered portion  236 , although the size and taper can also be selected to seal and plug the bore  232  at the junction of bore  232  and taper  236 , the junction of taper  236  and proximal opening  238 , the opening  238  itself, or any combination of these structures by forming plugging element  336  with a complementary shape. According to yet another aspect of the present invention, the material out of which plugging element  336  is formed can be doped with an antimicrobial or similar compound to inhibit the growth of microorganisms on the plugging element itself or on the surfaces against which it seats. 
     FIG. 20 illustrates a cross-sectional view of soft cannula  204 . The soft cannula  204  includes a longitudinally extending lumen  350 , which extends between a proximal end  352  and a distal end  354 . A positioning and retention bead, ring, or lug  356  is formed on the outer surface of the cannula  204 , and is sized to fit into recess  234  of the housing  202 . The bead  356 , in one aspect of the present invention, is sized relative to the recess  234  so that the bead can securely hold the cannula  204  in the housing  202 . In another aspect of the present invention, the bead  356  assists in positioning the distal end  354  of the cannula  204  at a predetermined distance from the housing  202 . In yet another aspect of the present invention, the cannula  204  is permanently mounted in the bore  232  by any of numerous ways, such as solvent or adhesive bonding, ultrasonic welding, heat staking, or the like. 
     The cannula  204 , in yet another aspect of the present invention, includes a restriction surface  358  formed on the inner surface of the lumen  350  near or at the proximal end  352  of the cannula. The restriction surface  358  is formed by a reduction in the inner diameter of the lumen  350  to a diameter which is only slightly smaller to slightly larger than the outer diameter of tube  220 . By forming the inner diameter of the lumen  350  and the outer diameter of tube  220 , and optionally of needle or stylet  304 , so that they are nearly the same, the clearance between the two surfaces is too small for liquids such as blood and aqueous solutions of medications to flow. According to yet another aspect of the present invention, the change in diameter can be formed on the outside of the tube  220 , and optionally on the outside of needle or stylet  304 . Thus, one aspect of the present invention is a seal against the passage of fluid in and out of the housing  202  along the cannula  204 , other than through the lumen  350 . 
     The operation of the exemplary embodiment of the present invention described above and illustrated in FIGS. 3-20 will now be described with reference thereto. The operation of the set  200  is similar in many respects to set  104 . Initially, the housing  202  is mounted to the handle  306  So that the distal end of the needle or stylet  304  extends distally from the distal end of the soft cannula  204 . As discussed above, the restriction  358  and the external surface of the needle or stylet  304  provide a fluid seal. The flaps  436  of the dust door  430  have been previously pushed aside by the needle or stylet  304 . The soft cannula  204  and housing  202  can then be inserted into a patient, e.g., subcutaneously, in a manner well-appreciated by one of ordinary skill in the art. The handle  306  is then retracted proximally by pressing laterally inwardly on one or both of the levers  264 , which releases the handle from the housing  202 . The flags  436  return to their generally planar configuration, inhibiting dust and dirt from entering the device. 
     The connecting hub  206 , with the tubing  208  and connector  210 , is then inserted into the space  240 , laterally displacing the locking fingers  256 ,  258 . With the pins  216 ,  218  in the bores  244 ,  246 , the guide surfaces  248 ,  250  guide the outer surfaces of the hub  206  as the hub moves distally. The locking fingers  256 ,  258  then snap over the locking surfaces  280 , securing the hub  206  to the housing  202  with the tube  220  extending through the soft cannula  202 . The outer surface of the tube  220  and the restriction  358  form a fluid seal, as described, and the flaps  436  again are moved aside by the tube  220 . The connector  210  can then be attached to a septum of a medication ampule, and medication delivered through the tubing  208 , through the soft cannula  202 , and to the patient. 
     After the medication infusion described above, the hub  206  can be removed proximally by pressing on the levers  264 , as described above, to release the hub from the housing  202 . The plug  330  can then be installed in place, as described above, with the plugging element  338  moving aside the flaps  436  and forming a seal with one of the proximal structures of the housing  202 . The housing  202  and cannula  204  are then prepared for later infusion, while sterility of the site is enhanced or maintained. 
     FIGS. 21 and 22 illustrate a pen needle  370  according to yet another aspect of the present invention. FIG. 21 illustrates a perspective view of the pen needle  370 ; FIG. 22 illustrates a longitudinal cross-sectional view. The pen needle  370  includes a cylindrical collar or shroud  372  having an open end  378 , a hub  374  forming a part of a closed end  380  of the collar, and a two-ended needle  376  extending through the hub with one end within the collar. The pen needle  370  also includes an annular groove  376  formed in the inner surface of the collar, and receives in the groove a dust door described in greater detail below. The pen needle  370  can be used in the place of set  104 , described above with reference to FIGS. 1 and 2, by placing the collar  372  around the septum of an ampule so that the needle  376  pierces the septum. The other end of the needle  376  can be inserted into a patient, and an infusion of medication delivered to the patient. 
     FIG. 23 illustrates yet another infusion set  400  in accordance with other aspects of the present invention. The infusion set  400  can be used with a medication delivery device  102  as described above which includes a medication ampule having a septum. The infusion set  400  includes an infusion needle or cannula  402  at a distal end, a holding pad  404  to secure the infusion needle to a patient, tubing  406  extending proximally from and in fluid communication with the infusion needle  402 , and a proximal connector  408  connected to the proximal end of the tubing. As discussed in greater detail above, the tubing  406  may be attached to the proximal connector using shrink tubing and solvent bonding, for example. 
     FIGS. 24-26 illustrate details of the infusion set  400  of FIG.  23 . More specifically, FIG. 24 illustrates a perspective view of the connector  408 ; FIG. 25 illustrates a longitudinal cross-sectional view of the connector; and FIG. 26 illustrates a portion of the connector. The connector  408  includes a cylindrical collar or shroud  412  which has an open end  414  and a closed end  416 . An annular shoulder  418  is formed in the closed end  416 , and a distal tubular extension  420  extends distally from the closed end. The extension  420  includes a lumen  422  communicating the open portion of the collar  412  with the distal end of the connector. The lumen  422  can have a constant inner diameter, or can include a distal reduced inner diameter portion  424  which, as described above with reference to bore  286 , can assist in forming a seal with the tubing  406  when the tubing is inserted into the lumen  422 . A fluid transfer device  426  is mounted in the connector  408  in the annular shoulder  418 , and is secured to the connector, such as by glueing, ultrasonic welding, or the like. 
     Turning to FIG. 26, the fluid transfer device  426  includes a sharpened proximal end  428  to pierce a septum of a medication ampule, such as septum  112 . The distal end  432  of the shaft  430  can be either sharpened or blunt. A lumen  434  extends between the sharpened proximal  428  and distal  432  ends. A mounting block  436  is mounted to the shaft  430 , and has a size and a shape to fit to annular shoulder  418 . 
     FIG. 27 illustrates, in a manner similar to FIG. 2, how a tube  450  can be joined to a needle or rigid cannula  452 . With the end of the needle  454  within the lumen  458  of the tube  450 , a tube  456  of shrinkable material is positioned over the outside of the tube so that it overlaps both the tube and the needle. By shrinking the tube  456 , the tube  450  is clamped down onto the shank of the needle  452 , securing the two together. Thereafter, the outer surface of the tube  456  can be used to secure the assembly to another component, such as by solvent bonding. 
     FIG. 28 illustrates a top plan view of the distal infusion end of set  400 , FIG. 29 illustrates a side view, partially in section of the distal end of set  400 , and FIG. 30 illustrates a cross-section view taken at line  30 — 30  in FIG.  29 . As can be seen in FIG. 29, tubing  406  is formed to be kink-resistant, as described in greater detail below. A hub  438  fluidly communicates the tubing  406  with the needle or cannula  402 . FIG. 30 illustrates that the holding pads  404  include an outer adhesive layer  410 , to secure the device to a patient. 
     FIG. 31 illustrates a cross-sectional view of tubing  406  according to one aspect of the present invention. The tubing  406  is formed to have a cross-sectional shape that makes the tubing resistant to kinking. In FIG. 31, the tubing  406  has a triangular cross-section. A piece of shrink tube  422  is illustrated positioned around the tube  406  prior to being shrunk down onto the outer surface of the tubing, for the reasons presented herein. By way of example and not of limitation, inner tube  406  can be formed of a polyethylene or polypropylene, and the outer shrink tube  422  can be formed of a PVC, polyester, or PTFE. FIGS. 32 and 33 illustrate yet further aspects of the present invention. In FIG. 32, tubing  406  is formed of a base tube  420 , a shrink tube  422  around the base tube, and at least one filaments, wires, or the like  424  between the base tube and the shrink tube. The filaments  424  strengthen the tube and assist in preventing kinking. In FIG. 33, the filaments  424  have been removed, with the shrink tube  422  acting to assist in preventing kinking. The shrink tube is  422  is then shrunk over the base tube  420 , resulting in a strengthened tubing  406 . 
     FIGS. 34 and 35 illustrate a dust door  430  according to yet another aspect of the present invention. The door  430  is formed of a thin sheet  432  of relatively strong and pliable material, which includes intersecting slits  434  which together form two or more flaps  436 . By way of example and not of limitation, sheet  432  can be formed of Mylar of about 0.003 inches thickness. The door  430  is, in certain aspects of the present invention, preferably installed in opening  238 ,  378 , or the open end of collar  116 , and prevents dust and dirt from entering these openings. Referring to FIG.  5  and opening  238 , when it is desired to insert, for example, tube  220  into the bore  232 , the flaps  436  are pushed aside by the advancing tube  220  without interfering with assembly of the device and without piercing the flaps. When the tube  220  is retracted, the flaps  436  resume their generally planar configuration. 
     The operation of the exemplary embodiment of the present invention described above and illustrated in FIGS. 23-35 will now be described with reference thereto. The use of the embodiments of FIGS. 23-35 is similar to the use of the embodiments of FIGS. 1 and 2. A user or patient inserts a medication ampule  108 , such an insulin cartridge, into the delivery device  102 , with the ampule&#39;s septum  112  accessible through the device. The connector  408  is screwed or otherwise placed over the end of the device  102  so that the piercing element  428  pierces the septum  112  and places the interior of the ampule in fluid communication with the cannula  402 . The user can then prime the set  400 , if desired. If the set  400  is already in place subcutaneously, the user manipulates the device  102  to move the piston  110  to deliver an amount of medication to the patient through the cannula  124 . 
     While the invention has been described in detail with reference to preferred embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention.