Abstract:
An infusion set assembly comprising a cannula housing having a base surface and a septum housing adapted to be pivotally attached to the cannula housing for movement between a position where an axis thereof is substantially perpendicular to the base surface and a position where the axis is substantially parallel to the base surface. The infusion set assembly further comprises an insertion needle assembly including an insertion needle and a cannula supported by the needle assembly with a tip of the insertion needle extending from a distal end of the cannula. An insertion guide housing is configured to support the insertion needle assembly with the needle substantially perpendicular to the base surface and adapted for movement between a position where the needle tip and cannula distal end are spaced from the base surface and a position where the needle tip and cannula distal end extend beyond the base surface.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to an infusion set, and more particularly to a low profile infusion set used for intermittent or continuous delivery of medication, such as insulin to a patient. 
       BACKGROUND OF THE INVENTION 
       [0002]    Patients who receive intermittent or continuous doses of medication, such as insulin, via subcutaneous injection, often have an infusion set affixed to their skin in a convenient location. Keeping an infusion set fixed in place is discreet, and reduces the need for repeatedly puncturing the skin with a needle, thereby reducing the risk of infection as well as reducing the formation of scar tissue. The infusion set typically includes a housing supporting a tubular cannula with a removable injection needle at one end for penetrating the skin, and a septum at the other end for receiving a needle attached to a supply tube from a medicinal source, e.g., an insulin pump. One well-known conventional infusion set is a “straight set”, in which the cannula and injection needle are inserted in an orientation substantially normal to the skin. The straight set requires a relatively short injection needle, which is less intimidating to some patients, and is relatively easy to insert through the skin. But, because the cannula and injection needle are supported to be oriented normal to the skin, the housing must be upright, conspicuous, and relatively bulky, and furthermore, the cannula, rigidly attached to a bottom of the housing can be subject to kinking and occlusion. 
         [0003]    Another known infusion set is a low profile angled set, in which the cannula and injection needle are supported in the housing to be oriented at an acute angle with respect to the skin. The housing of the low profile angled set is less bulky and is much more discreet than the housing of the straight set. However, because of the angled insertion, a much longer injection needle is required, and the longer needle is more intimidating and more difficult to insert, and is subject to inadvertent bending. 
         [0004]    Additional problems exist with both the conventional straight and angled sets. For example, a relatively long portion of cannula tubing is left exposed. A view of the injection site is often obscured. Adhesive mounting pads used on the sets can be awkward to use, often prematurely contacting the skin, causing wrinkling of the adhesive pad. Moreover, the needle or the cannula often touch non-sterile tissue or clothing prior to insertion, which increases the risk of infection. 
         [0005]    Another problem is that in infusion sets in which a self-adhesive pad is used to attach the unit to the skin, the self-adhesive pad must be well supported during insertion to avoid wrinkling the pad. If the user doesn&#39;t satisfactorily attach the pad to the skin without wrinkles, the infusion set may need to be removed and replaced. The user is more likely to have a problem applying and smoothing the adhesive pad with the needle/cannula already inserted since they must be careful not to dislodge the cannula. Furthermore, the insertion needle is usually left in place until the adhesive pad is completely attached and may cause pain or discomfort until it is removed. While a relatively small adhesive pad, that is just slightly larger than the infusion set base, would prevent the unsupported edges from drooping and prematurely contacting the skin, a smaller pad provides less adhesion and may allow the infusion set to become detached during use. 
       SUMMARY OF THE INVENTION 
       [0006]    Accordingly, the present invention is directed to an infusion set that mitigates or substantially obviates one or more of the shortcomings caused by the limitations and disadvantages of the related art. 
         [0007]    The features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by the apparatus, and the method of practicing the invention, particularly pointed out in the written description and claims below, as well as in the attached drawings. 
         [0008]    In accordance with an aspect of the invention, an infusion set assembly is provided with a multiple-part housing. A first portion or cannula housing is removably attachable to a surface of a user&#39;s skin. A second portion or septum housing is pivotally attached to the cannula housing, pivotable between a first position above the cannula housing and substantially normal to the surface of the skin and a second position alongside the cannula housing portion and substantially parallel to the skin surface. An elongated tubular cannula is provided, having a first end and a second end. An injection needle is removably mounted in the cannula and extends from the first end. The infusion set assembly is configured such that the injection needle and the first end of the cannula penetrate the skin surface at an injection site in an orientation that is substantially normal to the skin surface. After insertion of the cannula, the insertion needle is removed and the septum housing is pivoted to the second position. 
         [0009]    In accordance with another aspect of the invention, the cannula is initially supported by the insertion needle spaced from a bottom surface of the cannula housing. An adhesive assembly is provided on the bottom surface of the cannula housing for adhering the cannula housing portion to the skin. With the cannula initially maintained spaced from the adhesive surface, the user can fully attach the infusion set base and smooth the adhesive to the skin before the needle/cannula is inserted. If the adhesive pad is not satisfactorily attached or not smoothed without wrinkles, the infusion set can be removed without cannula/needle insertion. 
         [0010]    In accordance with yet another aspect of the invention, a disposable insertion guide housing portion is provided for supporting the cannula housing portion and the insertion handle portion above the injection site prior to injection, allowing the user to preposition the infusion set generally perpendicular to and above the skin surface at the injection site. The infusion set can be pre-packaged with the disposable insertion guide housing portion, ready to use, right off the shelf without needing to be assembled by the user. The guide housing portion also maintains the insertion needle hidden from view during the entire insertion process to lessen the user&#39;s anxiety, particularly in the case of children. 
         [0011]    In accordance with a further aspect of the invention, an insertion needle or solid trocar initially passes through the interior of the soft cannula such that its sharp cutting edges extend beyond the distal end of the cannula. The proximal end of the needle is attached to an insertion needle handle which is mounted within an insertion guide housing which positions and holds the needle and cannula distal end above the cannula housing. With the needle and cannula distal end spaced from the attachment surface, the cannula housing is attached to the skin at the insertion site on the skin. Thereafter, the insertion needle handle is pressed towards the skin such that the needle and cannula distal end are guided towards the cannula housing by the insertion guide housing. The needle and cannula distal end pass through the opening in the cannula housing, penetrate the skin, and are inserted perpendicularly into the tissue. The insertion needle is then withdrawn into the insertion guide housing leaving only the distal end of the cannula in the subcutaneous tissue. The insertion guide housing can then be removed and discarded with the insertion needle safely shielded inside. During the entire insertion process the insertion needle is never exposed. 
         [0012]    In accordance with a further aspect of the invention, the proximal end of the septum housing is pivoted approximately 90 degrees and latched to the main body of the cannula housing so as to prevent further rotation or movement. As the septum housing is pivoted, the portion of the cannula between the distal end of the septum housing and the opening in the base of the cannula housing is bent in a smooth arc over a mandrel on the cannula housing. The mandrel controls the bend radius of the cannula in the latched position to further prevent the cannula from kinking. Clearance between the cannula and opening in the main body allows the cannula to flex if the inserted cannula and the housing bottom are not perpendicular without kinking the cannula. Once the septum housing is latched, a needle hub assembly may be attached to the cannula housing assembly. 
         [0013]    In accordance with still another aspect of the invention, the septum housing supports the cannula and is initially detached from the cannula housing. Upon depression of the insertion needle handle, pivot pins on the septum housing engage mating pivot holes in the cannula housing. The pivot pins snap into the holes, pivotally interconnecting the septum housing to the cannula housing. 
         [0014]    In accordance with yet another aspect of the invention, the septum housing remains pivotally-attached to the cannula housing. The septum and cannula are mounted coaxially within a separate cannula cartridge which is mountable on the insertion needle with the needle extending from the cannula distal end. The cannula cartridge is initially mounted above and axially-aligned with a stepped bore in the septum housing. The axis of the stepped bore in the septum housing is aligned with the opening in the cannula housing and is perpendicular to the flat base of the cannula housing. When the insertion handle is pressed towards the skin, the cannula cartridge is advanced such that the cartridge enters the stepped bore of the septum housing, and the needle and cannula distal end pass through the opening in the bottom of the cannula housing penetrating the surface of the skin. As the handle is depressed, the cannula cartridge engages and is retained within the septum housing. After the insertion handle is retracted and removed, the septum housing can then be pivoted parallel to the surface of the skin and latched. 
         [0015]    It is to be understood that both the above general description and the following detailed description are exemplary and explanatory, and are intended to explain the principles of the claimed invention. The accompanying drawings are included to provide a further understanding of the invention and are incorporated and constitute part of the specification, illustrating presently preferred embodiments of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a perspective view of an infusion set assembly in accordance with a first exemplary embodiment of the invention; 
           [0017]      FIG. 2  is an exploded perspective view of the infusion set assembly of  FIG. 1 ; 
           [0018]      FIG. 3  is a cross-sectional view along line  3 - 3  of  FIG. 1 ; 
           [0019]      FIG. 4  is a cross-sectional view similar to  FIG. 3  with the insertion handle depressed and the cannula fully inserted; 
           [0020]      FIG. 5  is a cross-sectional view similar to  FIG. 4  with the insertion handle retracted after the cannula has been fully inserted; 
           [0021]      FIG. 6  is a cross-sectional view similar to  FIG. 5  with the insertion handle retracted into the insertion guide housing which is removed from the cannula housing after the cannula has been fully inserted; 
           [0022]      FIG. 7  is a perspective view of the cannula housing as illustrated in  FIG. 6 ; 
           [0023]      FIG. 8  is a perspective view of the cannula housing with the cannula fully inserted and the septum housing in the folded and latched position; 
           [0024]      FIG. 9  is a cross-sectional view along the line  9 - 9  of  FIG. 8 ; 
           [0025]      FIG. 10  is a top view of a needle hub assembly about to be removably attached to the inserted infusion set of  FIG. 8 ; 
           [0026]      FIG. 11  is an exploded view of an alternative embodiment of the insertion set assembly of the present invention; 
           [0027]      FIG. 12  is a cross-sectional side view of the insertion set assembly of  FIG. 11 ; 
           [0028]      FIG. 13  is a cross-sectional view similar to  FIG. 12  with the insertion handle depressed, the cannula cartridge assembly inserted into the septum housing, and the cannula fully inserted into the subcutaneous tissue; 
           [0029]      FIG. 14  is a cross-sectional view similar  FIG. 13  with the insertion handle retracted, the cannula cartridge assembly inserted into the septum housing, and the cannula fully inserted into the subcutaneous tissue; 
           [0030]      FIG. 15  is a cross-sectional view similar to  FIG. 14  with the insertion handle retracted and the insertion guide housing removed from the cannula housing assembly; 
           [0031]      FIG. 16  is a perspective view of an alternate insertion guide housing in accordance with an exemplary embodiment of the invention with the insertion needle handle fully retracted; and 
           [0032]      FIG. 17  is a perspective view of the insertion guide housing of  FIG. 16  with the cover closed. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    Preferred features of embodiments of this invention will now be described with reference to the figures. It will be appreciated that the spirit and scope of the invention is not limited to the embodiments selected for illustration. Also, it should be noted that the drawings are not rendered to any particular scale or proportion. It is contemplated that any of the configurations and materials described hereafter can be modified within the scope of this invention. 
         [0034]    Referring to  FIGS. 1-9 , infusion set assembly  1  that is a first exemplary embodiment of the present invention is shown. Infusion set assembly  1  generally includes cannula housing assembly  10 , septum housing assembly  80 , insertion guide housing  68 , and insertion needle assembly  38 . Desirably, infusion set assembly  1  is supplied in a sterile package in the pre-assembled configuration as shown in  FIGS. 1 and 3 . 
         [0035]    Referring to  FIG. 2-3 , septum housing assembly  80  includes septum housing  16  which is configured to support cannula  2 . Septum housing  16  is desirably manufactured from molded plastic, but may be any suitable material. A series of stepped bores  20 ,  21 ,  22  and  23  are defined in septum housing  16  and extend axially from a distal end of septum housing  16  to a proximal end thereof. Cannula  2  extends through stepped bore  21  and extends from the distal end of septum housing  16 . Ferrule  29  desirably includes a tapered distal portion  27  and a cylindrical proximal portion  28 . Ferrule  29  extends from stepped bore  22  to stepped bore  21  wherein tapered distal portion  27  extends within a flared proximal portion of cannula  2 . Ferrule distal portion  27  compresses cannula  2  against bore  20  of septum housing  16 , thereby creating a fluid-tight seal. 
         [0036]    Septum  30  is compressed slightly to fit within the inner bore of ferrule proximal portion  28  and thereby seals the proximal end of cannula  2 . Septum  30  may be spherical, as illustrated, or any other configuration to seal the ferrule proximal portion  28 . Septum retainer  32  is positioned in septum housing bore  23  to retain septum  30  and ferrule  29  within septum housing  16 . Septum retainer  32  may be press-fit, adhesive-bonded, ultrasonically welded or otherwise retained in bore  23 . Septum retainer  32  has a concentric septum aperture  34 , see  FIG. 7 , configured to facilitate passage of an insertion needle or infusion needle as will be described hereinafter. The details of septum  30 , ferrule  29  and cannula  2  are for illustrative purposes only and many other methods commonly known in the art may be used for securing and providing a septum seal over the proximal end of cannula  2 . 
         [0037]    Septum housing assembly  80  is configured to be pivotally connected to cannula housing assembly  10  after insertion of cannula  2  into a user. Cannula housing  15  of cannula housing assembly  10  includes a pair of pivot holes  26  configured to snap-fittingly receive pivot pins  25  on septum housing  16  to retain septum housing assembly  80  pivotally connected to cannula housing assembly  10 . Pivot holes  26  are desirably through holes opening both inwardly and outwardly, with the pivot pins  25  being received through the inward portions of holes  26 . Septum housing pivot pins  25  are located at the ends of flexible arms  24  on opposed sides of cannula housing  16 . Flexible arms  24  are configured to flex inward to permit each pivot pin  25  to snap into mating engagement with a respective pivot hole  26  in cannula housing  15 , as shown in  FIG. 2 . The forward edge of each pivot pin  25  is desirably beveled, as indicated at  45 , to further facilitate positioning of pivot pins  25  into the respective holes  26  more easily. In the present embodiment, pivotal interconnection between septum housing assembly  80  and cannula housing assembly  10  occurs after insertion of cannula  2 , as will be described in more detail hereinafter. 
         [0038]    Cannula housing  15  further includes a substantially planar bottom surface  12  with opening  14  extending therethrough for passage of cannula  2 . Elastomeric disk  18  or the like is desirably mounted about opening  14  and includes a through bore for passage of cannula  2 . Elastomeric disk  18  is configured to seal around the outside diameter of cannula  2  after insertion. Opening  14  may be sized to receive elastomeric disk  18  as shown, or alternatively, elastomeric disk  18  may be positioned against bottom surface  12  of cannula housing  15  and retained thereagainst, for example, by mounting pad  11  which is described hereinafter. Alternatively, elastomeric disk  18  may be omitted and the diameter of opening  14  through cannula housing  15  may be made just slightly larger than the outer diameter of cannula  2 . 
         [0039]    To protect cannula  2 , cannula housing  15  includes a cannula guide or curved mandrel  46 , positioned to support a portion of cannula  2  proximate opening  14 . Cannula guide  46  provides an arcuate path for cannula  2 . As septum housing  16  is pivoted about pivot pins  25  to a second position, as described hereinafter, cannula guide  46  supports an intermediate portion of cannula  2  along a gradual curve. The arcuate path is approximately a fraction of a 90° bend, with a radius in the range of approximately 1-4 mm and desirably about 2.25 mm. This slight curve prevents kinking of cannula  2 . 
         [0040]    Self-adhesive mounting pad  11  is attached to bottom surface  12  of cannula housing  15 . The adhesive surface of mounting pad  11  is initially covered by a removable backing paper or liner  17 . Liner  17  may be divided into multiple parts to make removal easier. Since cannula  2  is initially maintained spaced from bottom surface  12 , as shown in  FIG. 3 , the user can fully attach cannula housing assembly  10  and smooth mounting pad  11  to the skin before cannula  2  is inserted. If mounting pad  11  is not satisfactorily attached or not smoothed without wrinkles, cannula housing assembly  10  can be removed, and possibly reapplied, without disruption to an inserted cannula. 
         [0041]    Referring to  FIGS. 1-4 , insertion needle assembly  38  is configured to insert cannula  2  into the user&#39;s skin. Insertion needle assembly  38  includes handle  39  with insertion needle or trocar  49  attached thereto. Handle  39  is configured for guided movement within insertion guide housing  68 . As shown in  FIG. 3 , in axial cross-section, handle  39  has a generally square or rectangular shape with a rounded top surface. However, the cross-section may have various configurations configured to complement insertion guide housing  68 . While it is desirable that handle  39  and insertion guide housing  68  are configured to prevent handle  39  from rotating within insertion guide housing  68 , such is not necessary provided septum housing assembly  80  is prevented from rotating relative to cannula housing assembly  10  or a universal connection, for example, a ball and socket connection, is provided between septum housing assembly  80  and cannula housing assembly  10 . While handle  39  may have a solid outer cross-section, the illustrated example is defined by a series of ribs which reduces the overall mass and improves the molding characteristics of handle  39 . Flexible barbs  52  on opposed sides of handle  39  are configured to engage notches  75  in insertion guide housing  68 . As shown in  FIG. 3 , engagement of barbs  52  in notches  75  holds insertion needle assembly  38  in a retracted position until handle  39  is depressed. Barbs  52  are configured to flex inward as handle  39  is depressed, as shown in  FIG. 4 . 
         [0042]    Insertion needle  49  is adhesive-bonded or otherwise connected to handle  39  and is configured to be passed coaxially through retainer  32 , septum  30 , ferrule  29 , and cannula  2  such that needle tip  50  extends, for example, 2 or 3 mm, beyond the distal end of the cannula  2 . Insertion needle  49  may be a standard beveled needle as is common in the art or a solid trocar. In addition to being easier to manufacture, sharp tip  50  of a trocar can be shorter than a comparable needle since the bevels extend in 3 or 4 facets from the needle centerline to the outer edge rather than across the entire diameter of the needle. A shorter insertion needle tip  50  length will not protrude as far beyond the end of the cannula  2  and may reduce the risk of contacting underlying muscle tissue during insertion. 
         [0043]    Insertion needle  49 , cannula  2  and septum  30  are desirably configured such that friction between insertion needle  49  and septum  30  and cannula  2  is sufficient to retain septum housing assembly  80  to insertion needle assembly  38  without any additional retaining mechanism, however, an additional retaining mechanism may be provided if desired. Notch  44  in insertion needle handle  39  orients septum housing assembly  80  and aligns pivot pins  25  with pivot holes  26  in cannula housing  15 . 
         [0044]    Insertion guide housing  68  rests on the top surface of cannula housing  15  and is initially attached to cannula housing assembly  10  by flexible barbs  79  which engage the outward portions of pivot holes  26  in cannula housing  15 . Insertion guide housing can be released from cannula housing  15  by flexing barbs  79  outward. Insertion guide housing  68  desirably has flat sides  47  configured to be gripped to prevent rotation of infusion set assembly  1  during insertion, thus offering more control over the subsequent orientation of the infusion set on the surface of the skin. Insertion guide housing  68  may be molded in one piece from plastic such as polycarbonate, polypropylene, or other plastic or may be manufactured utilizing deferent techniques and different materials. 
         [0045]    Having described the components of infusion set assembly  1 , its operation will now be described with respect to FIGS.  1  and  3 - 9 . Infusion set assembly  1  is supplied in sterilized packaging in the configuration shown in  FIGS. 1 and 3  with insertion guide housing  68  attached to cannula housing assembly  10 , septum housing assembly  80  mounted to insertion needle assembly  38 , and handle  39  in the retracted position. Cannula  2  and insertion needle  49  are hidden from view and fully protected within insertion guide housing  68 . 
         [0046]    Referring to  FIG. 3 , barbs  52  on handle  39  engage notches  75  in insertion guide housing  68  to hold cannula  2  and sharp tip  50  of insertion needle  49  above opening  14  in cannula housing  15 . The user then removes backing paper  17  to expose the adhesive surface of mounting pad  11 . The user may carefully position, adhere, and smooth mounting pad  11  on the skin without the discomfort or anxiety associated with an inserted needle. 
         [0047]    Referring to  FIG. 4 , the top of insertion needle handle  39  is pressed, thereby disengaging barbs  52  from notches  75  and advancing needle  49  and septum housing assembly  80  towards the skin. Insertion needle  49  and cannula  2  pass through opening  14  in cannula housing  15  into the subcutaneous tissue. Pivot pins  25  on septum housing  16  flex inward upon contact with the top of cannula housing  15  until pins  25  engage the inward portions of pivot holes  26 . Pivot pins  25  desirably make an audible “click” as pins  25  snap outward into pivot holes  26  to alert the user that cannula  2  and needle  49  are fully inserted and septum housing  16  is securely connected to cannula housing  15 . 
         [0048]    Infusion set assembly  1  provides a ready to use, preloaded infusion set. Since the force to insert needle  49  is well below 0.5 pound, needle  49  and cannula  2  may easily be inserted with only finger pressure. Since the speed of insertion is controlled by the user, needle insertion may be stopped at any time if the user feels discomfort such as when penetrating muscle tissue. However, unlike insertion by hand, insertion guide housing  68  allows cannula housing  15  to be attached to the skin before inserting cannula  2 , thus ensuring that cannula  2  is inserted perpendicular to the surface of the skin. 
         [0049]    As pivot pins  25  engage pivot holes  26 , pivot pins  25  extend through holes  26  such that barbs  79  on insertion guide housing  68  are pushed outward by pivot pins  25 , thereby unlatching insertion guide housing  68  from cannula housing  15 . Insertion needle handle  39  may be retracted away from the skin into insertion guide housing  68  until barbs  52  engage notches  75  as shown in  FIG. 5 . Alternatively, insertion guide housing  68  can be removed from cannula housing  15  with handle  39  depressed, and thereafter, needle  49  retracted. In either case, insertion guide housing  68  is removed and discarded with insertion needle  49  safely shielded inside insertion guide housing  68  as shown in  FIG. 6 . 
         [0050]      FIG. 7  shows cannula housing assembly  10  after insertion guide housing  68  and needle  49  have been removed. At this time, septum housing assembly  80  is still generally perpendicular to cannula housing bottom surface  12 . Septum housing  16  is then pivoted from this upright position until it latches in the flattened position as shown in  FIGS. 8 and 9 . Latching barbs  54  on cannula housing  15  engage mating notches on the sides of the septum housing  16 . Desirably, septum housing  16  snaps into position with an audible “click”. As septum housing  16  pivots from the upright insertion position to the flattened, latch position, the portion of exposed cannula  2  between opening  14  in cannula housing  15  and bore  20  of septum housing  16  is bent in a smooth radius over curved mandrel  46 . Mandrel  46  desirably has a groove which is wider than the outer diameter of cannula  2  to accommodate cannula misalignment. Since septum housing pivot pins  25  are located at the ends of flexible arms  24 , opening  14  in cannula housing  15  is visible once septum housing  16  is in the flattened, latched position, allowing the infusion site to be viewed. Finger depression  42  is provided on the top of main body  15  to allow the user to hold the cannula housing assembly  10  in place while septum housing  16  is folded and latched. 
         [0051]    Once cannula  2  is inserted and septum housing  16  latched in the folded position, infusion set assembly  1  is ready for connection to an infusion source, for example, an infusion pump, through a needle hub assembly. A first exemplary embodiment of a needle hub assembly  90  useable with infusion set assembly  1  is illustrated in  FIG. 10 . Needle hub assembly  90  is configured to be removably attached to septum housing  16 . 
         [0052]    Needle hub assembly  90  includes a substantially flat housing  92 , a resilient band  97 , flexible arms  94  and  95 , and a needle  96 . The needle hub assembly  90  includes guide rails (not shown) extending along a lower surface of housing  92 , inward of flexible arms  94  and  95 . The guide rails are configured to align with and slide into grooves  36  in the sides of septum housing  16 . Sliding of the guide rails into grooves  36  guides needle  96  through septum retainer  32  and septum  30  such that needle  96  terminates in ferrule  29 . 
         [0053]    To retain needle hub assembly  90  in engagement with septum housing  16 , resilient band  97  extends between flexible arms  94  and  95  and is configured to flex over and be retained by a retaining bump  37  on septum housing  16 . Retaining bump  37  desirably has a ramped profile when viewed from the side (see  FIG. 3 ) such that resilient band  97  slides freely over retaining bump  37  as needle housing assembly  90  is connected to septum housing portion  16 . Resilient band  97  may make an audible click to give the user positive acknowledgment that needle hub assembly  90  and septum housing  16  are locked together. To remove needle hub assembly  90 , arms  94  and  95  are squeezed together such that resilient band  97  flexes upward to a central height greater than the height of retaining bump  37 . Needle hub assembly  90  is slid off of septum housing portion  16 , thereby removing needle  96  from septum  30 . Other types of engaging and locking assemblies may also be used. For example, a set of complementary barbs and notches (not shown) can be provided on opposing surfaces of needle hub assembly  90  and septum housing  16 . Other assemblies may also be utilized. 
         [0054]    Flexible tube  98  is attached to needle  96  and projects from a rear end of needle hub assembly  90 . Tube  98  can extend directly to a medication source, such as an insulin pump, or to an appropriate fitting such as a Luer fitting, which can be connected to an external infusion pump (not shown) or another medicine source. Operation of the medication source supplies medicine through tube  98 , through needle  96  and through cannula  2  to deliver the of medicine to the user. 
         [0055]    Referring to  FIGS. 11-15 , infusion set assembly  101  that is a second exemplary embodiment of the present invention is illustrated. Infusion set assembly  101  is similar to the previous embodiment, however, septum housing assembly  180  is initially pivotally attached to cannula housing assembly  110  while cannula  102 , ferrule  129  and septum  130  are mounted in a separate insertable cannula cartridge  178 . 
         [0056]    As shown in  FIGS. 11-15 , insertion needle handle assembly  38  and insertion guide housing  68  in the present embodiment are essentially the same as in the first exemplary embodiment. Insertion needle assembly  38  includes handle  39  with insertion needle or trocar  49  attached thereto. Handle  39  is configured for guided movement within insertion guide housing  68 . Flexible barbs  52  on opposed sides of handle  39  are configured to engage notches  75  in insertion guide housing  68 . As shown in  FIG. 12 , engagement of barbs  52  in notches  75  holds insertion needle assembly  38  in a retracted position until handle  39  is depressed. Barbs  52  are configured to flex inward as handle  39  is depressed, as shown in  FIG. 13 . Insertion needle  49  is adhesive-bonded or otherwise connected to handle  39  and is configured to be passed coaxially through insertable cannula cartridge  178 , as will be described. 
         [0057]    Cannula housing assembly  110  is also similar to cannula housing assembly  10  of the previous embodiment and includes cannula housing  115  with a substantially planar bottom surface  112  with opening  114  extending therethrough for passage of cannula  102 . Elastomeric disk  118  or the like is desirably mounted about opening  114  and includes a through bore for passage of cannula  102 . Elastomeric disk  118  is configured to seal around the outside diameter of cannula  102  after insertion. 
         [0058]    Self-adhesive mounting pad  111  is attached to bottom surface  112 . The adhesive surface of mounting pad  111  is initially covered by a removable backing paper or liner  117 . Liner  117  may be divided into multiple parts to make removal easier. As in the previous embodiment, cannula  102  will initially be maintained spaced from bottom surface  112 , as shown in  FIG. 12 , and the user can fully attach cannula housing assembly  110  and smooth mounting pad  111  to the skin before cannula  102  is inserted. If mounting pad  111  is not satisfactorily attached or not smoothed without wrinkles, cannula housing assembly  110  can be removed, and possibly reapplied, without disruption to an inserted cannula. 
         [0059]    As in the previous embodiment, cannula housing  115  includes pivot holes  126  configured to receive pivot pins  125  extending from flexible arms  124  of septum housing  116 . In the current embodiment, in the initial configuration as shown in  FIG. 12 , septum housing  116  is pivotally connected to cannula housing  115  via pivot pins  125 . Septum housing  116  is initially oriented such that the axis thereof is substantially perpendicular to bottom surface  112  of the cannula housing  115 . 
         [0060]    Stepped bores  120  and  122  extend through septum housing  116  and are configured to receive insertable cannula cartridge  178 . Referring to  FIGS. 11 and 12 , cartridge  178  is configured to receive cannula  102 , ferrule  129 , septum  130  and septum retainer  132 . Cartridge  178  is desirably a molded plastic assembly, but may be manufactured using various materials and various methods. Cannula  102  extends from the distal end of cartridge  178 . Ferrule  129  is attached to and supports cannula  102 . Ferrule  129  may be a separate component positioned within cartridge  178 , or alternatively, may be formed as a portion of cartridge  178  as illustrated. Septum  130  is positioned in ferrule  129  to seal the proximal end of cannula cartridge  178 . Septum retainer  132  is bonded, ultrasonically welded or otherwise secured in cannula cartridge  178  to retain septum  130  and cannula  102 . Cannula cartridge  178  desirably has one or more outwardly extending barbs  177  on the distal end thereof to retain the cannula cartridge  178  in septum housing  116  by snap fit, however, various methods of securing cartridge  178  in place can be used. 
         [0061]    The assembled cannula cartridge  178  is mounted on insertion needle assembly  38  with insertion needle  49  passing coaxially through retainer  132 , septum  130 , ferrule  129 , and cannula  102  such that needle tip  50  extends beyond the distal end of cannula  102 , for example, by 2 or 3 mm. Needle  49 , septum  130  and cannula  102  are desirably configured such that friction between insertion needle  49  and septum  130  and cannula  102  is sufficient to hold cannula cartridge  178  on insertion needle assembly  38  without any additional locking mechanism, however, a locking mechanism may be provided if desired. Cannula cartridge  178  is generally symmetrical about the cannula axis so it is not necessary to key or otherwise orient cannula cartridge  178  on insertion needle assembly  38 . 
         [0062]    Insertion guide housing  68  is attached to cannula housing  115  in a manner similar to that of the previous embodiment. Since pivot pins  125  on septum housing  116  are already engaged in pivot holes  126 , pivot holes  126  are made deeper than in the previous embodiment to allow barbs  79  on insertion guide housing  68  and pivot pins  125  on septum housing  116  to simultaneously be positioned in pivot holes  126 . To remove insertion guide housing  68 , sides  81  of housing  68  are squeezed together, springing barbs  79  outward. Insertion guide  68  may then be lifted off cannula housing  115 . 
         [0063]    Having described the components of infusion set assembly  101 , operation thereof will be described with reference to  FIGS. 12-15 . Infusion set assembly  101  is desirably supplied in a sterilized package in the configuration as shown in  FIG. 12 . Cannula cartridge  178  is positioned on insertion needle  49  with needle tip  50  extending from the distal end of cannula  102 . Septum housing  116  is pivotally connected to cannula housing  115  and positioned with the axis of septum housing  116  substantially perpendicular to cannula housing bottom surface  112 . Handle  39  is in a retracted position with a portion of needle  49  extending into septum housing bores  120 ,  122 , but not extending beyond bottom surface  112 . To utilize infusion set assembly  101 , backing paper  117  is removed from the adhesive surface of mounting pad  111 . The user may carefully position, adhere, and smooth mounting pad  111  on the skin without the discomfort or anxiety associated with an inserted needle. 
         [0064]    Pressing the insertion needle handle  39  towards the skin disengages barbs  52  from notches  75  of insertion guide housing  68 , thereby advancing insertion needle  49  and cannula cartridge assembly  178  towards septum housing  116 . Sharp tip  50  of needle  49  passes through opening  114  in cannula housing  115 , penetrating the skin. As barbs  177  on cannula cartridge  178  enter bore  120  in septum housing  116 , barbs  177  flex inward towards cannula  102 . 
         [0065]    Cannula cartridge  178  is configured such that at approximately the moment insertion needle  49  and cannula  102  are fully inserted, barbs  177  have passed completely through bore  120  and spring outward and latch cannula cartridge  178  in septum housing  116  as shown in  FIG. 13 . Desirably, springing of barbs  177  makes an audible “click” to alert the user that cannula  102  has been fully inserted and cannula cartridge  178  is secured in septum housing  116 . 
         [0066]    Insertion needle handle  39  is then retracted until barbs  52  again engage notches  75  in insertion guide housing  68 , as shown in  FIG. 14 . Squeezing opposed sides  81  of insertion guide housing  68  releases barbs  79  from pivot holes  126  of cannula housing  115  such that insertion guide housing  68  can be removed. Insertion guide housing  68  can then be discarded with needle tip  50  safely shielded inside guide housing  68  as shown in  FIG. 15 . Once guide housing  68  is removed, infusion set assembly  101  is in the same configuration as illustrated in  FIG. 7  with respect to the first exemplary embodiment. Septum housing  116  may then folded and latched via barbs  154  in a manner similar to that shown in  FIGS. 8 and 9  and as described in the previous embodiment. As in the previous embodiments, as septum housing  116  pivots from the upright insertion position to the flattened, latch position, a portion of cannula  102  is bent in a smooth radius over curved mandrel  146 . Needle hub assembly  90  may then be attached to septum housing  116  in a manner similar to that described with respect to  FIG. 10 , to permit the flow of medication. 
         [0067]    An alternate insertion guide housing  68 ′ with a cover  82  is illustrated in  FIGS. 16-17 . In the present embodiment, the length of the insertion guide housing  68 ′ and handle  39 ′ are shorter than in the previous embodiments in order to minimize the overall size of the device as well as the bulk of disposable material. The use of this version is similar to the previously described embodiments, however, by shortening these components, the sharp tip  50  of needle  49  is closer to the open end of insertion guide housing  68 ′ in the retracted position. To protect the user from an accidental needle stick, cover  82  can be snapped to the bottom of insertion guide housing  68 ′. Cover  82  can be a separate component, or desirably, integrally attached to insertion guide housing  68 ′, for example, by integral hinge  84  as shown. Cover  82  includes attachment loops  83  configured to engage insertion guide housing barbs  79  to latch cover  82  in the closed position. Other latching mechanisms may also be utilized. 
         [0068]    While the described invention has been taught with specific reference to the above-described embodiments, those skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and the scope of the invention. 
         [0069]    Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.