Abstract:
A device and method is provided to gain access to interior body regions. The system includes a safety needle assembly, a blade assembly, an obturator assembly, and a dilator assembly. The safety needle assembly accesses an interior body region, after which the blade assembly expands the pathway created by the safety needle assembly. The obturator then further expands the pathway and delivers the dilator assembly to the desired location. The safety needle assembly, obturator assembly, and blade assembly are removed, leaving the dilator assembly in place for future procedures.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Pursuant to 35 U.S.C. §120, this application is a continuation-in-part of, and claims priority to, co-pending U.S. patent application Ser. No. 14/624,818, filed Feb. 18, 2015, which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to devices and methods to access interior body regions. More particularly, it relates to devices and methods used to create space to insert a tube into a patient. 
       BACKGROUND 
       [0003]    Embodiments of the invention relate to devices to create access to interior body regions and methods of using the devices. 
         [0004]    There are many instances in which a practitioner must access the chest, abdomen, or pelvis, and insert a drainage tube, or chest tube. Examples of these instances include: collapsed lung, lung infection, bleeding in the chest cavity, fluid or air buildup due to other medical conditions or trauma, and prior surgery. 
         [0005]    The traditional way of inserting a chest tube begins with the practitioner prepping the side of the body for the chest tube by sterilizing the area. Using a scalpel, the practitioner then makes a small incision (skin nick), between the ribs closest to the desired location in the chest. Then, using a combination of blunt dissection and surgical clamps, the practitioner will slowly open the space and extend it into the chest cavity. Once the practitioner confirms she has reached the desired space, the chest tube is inserted and sutured in place to prevent slippage. 
         [0006]    Critics claim that the traditional method of chest tube insertion is barbaric and does not take advantage of advances in technology that can make the insertion process safer and more effective. Some companies have designed devices, called trocars, to facilitate safer and easier chest tube placement without using multiple, separate components. 
         [0007]    Many groups of trocars include a combination of a safety needle, an obturator and a dilator. The doctor advances the device against the skin and interior body regions using the safety needle. As the doctor advances the device through the body, the obturator expands the pathway created by the safety needle. When the device reaches the desired area, the practitioner removes the safety needle and the obturator from the dilator, leaving the dilator in place. The practitioner then pushes the chest tube through the dilator and removes the dilator, leaving the chest tube in the desired location. 
         [0008]    Problems arise with these types of trocars, however, because the obturator does not actually work very well in expanding the pathway created by the relatively small safety needle. The skin provides a tough membrane that resists expansion, and additional skin nicks (using a separate scalpel) are required around the safety needle to allow the obturator to properly expand the skin layer and continue to penetrate deeper into the body. 
         [0009]    To address this issue, other groups of trocars employ a retractable blade instead of a safety needle. The blade is used to create a larger skin nick and advance through other tissues as needed until reaching the desired location. The obturator easily expands the pathway as it passes through the skin layer while the practitioner advances the device, and then the blade is retracted and the blade/obturator combination is removed, leaving the dilator in place for the chest tube. 
         [0010]    While these groups of trocars address the issue of requiring an additional scalpel to allow the obturator to expand the skin layer, they do not include the safety needle that prevents the doctor from progressing too quickly or too far and causing harm to the patient. Without the safety needle as part of the system, the patient is at a greater risk of complications. 
         [0011]    What is needed in the market is an all-in-one trocar device that provides the ability to create a skin nick and maintain safety as the device is inserted deeper into the body, while quickly accessing the desired location for chest tube placement. 
       BRIEF SUMMARY OF THE INVENTION 
       [0012]    Benefits achieved in accordance with principles of the disclosed invention include a device that provides access to interior body regions. 
         [0013]    Some aspects of the present invention relate to a safety needle assembly, a blade assembly, an obturator assembly, and a dilator assembly. The safety needle assembly, blade assembly, obturator assembly, and dilator assembly are assembled to create an access device. 
         [0014]    In some aspects of the present invention, the blade assembly includes multiple blades, while in other aspects of the present invention, the blade assembly includes a single blade. 
         [0015]    In other aspects of the present invention, the safety needle assembly includes a hub through which fluid may be drawn in order to confirm the device has reached the proper location within the body. 
         [0016]    In further aspects of the present invention, the blade assembly and safety needle assembly are longitudinally coaxial, while in still further aspects of the present invention, the blade assembly and safety needle assembly are not longitudinally coaxial. 
         [0017]    Yet other aspects of the present invention relate to a method of accessing interior body regions in which the safety needle assembly is advanced through skin and into interior body regions to create a pathway. The blades of the blade assembly are deployed and the blade assembly is advanced into the skin to create a skin nick, after which the blades are retracted. The access device is then advanced into the tissue, and the obturator assembly increases the diameter of the pathway created by the safety needle. After the access device is in the proper location, the safety needle assembly, blade assembly, and obturator assembly are removed from the dilator assembly, leaving the dilator assembly in the body to provide a conduit through which other devices may be inserted. 
       BRIEF SUMMARY OF THE DRAWINGS 
       [0018]    The accompanying drawings, which are incorporated in and form a part of the specification, illustrate example embodiments and, together with the description, serve to explain the principles of the invention. In the drawings: 
         [0019]      FIG. 1  illustrates an insertion device according to aspects of the present invention; 
         [0020]      FIG. 2  illustrates a safety needle according to aspects of the present invention; 
         [0021]      FIG. 3  illustrates a blade assembly according to aspects of the present invention; 
         [0022]      FIG. 4  illustrates an obturator assembly according to aspects of the present invention; 
         [0023]      FIGS. 5A-B  illustrate an alternate embodiment of a blade assembly and an obturator assembly according to aspects of the present invention; 
         [0024]      FIG. 6  illustrates a first step in inserting the insertion device according to aspects of the present invention; 
         [0025]      FIG. 7  illustrates a second step in inserting the insertion device according to aspects of the present invention. 
         [0026]      FIG. 8  illustrates a final step in inserting the insertion device according to aspects of the present invention. 
         [0027]      FIGS. 9-10  illustrate an alternate embodiment of an insertion device according to aspects of the present invention; 
         [0028]      FIG. 11  illustrates the process by which an obturator assembly is assembled for an alternate embodiment of the insertion device; 
         [0029]      FIG. 12  illustrates the assembly process to create an alternate embodiment of the insertion device; 
         [0030]      FIG. 13  illustrates a cross section of a dilator and an obturator of an alternate embodiment of the insertion device; and 
         [0031]      FIG. 14  illustrates a cross section of a dilator, obturator, and blade assembly of an alternate embodiment of the insertion device. 
     
    
     DETAILED DESCRIPTION 
       [0032]      FIG. 1  illustrates an insertion device according to aspects of the present invention. 
         [0033]    As shown in the figure, insertion device  100  includes safety needle  102 , blade assembly  104 , obturator assembly  106 , dilator assembly  108 , and handle hole  110 . 
         [0034]    Specific aspects of safety needle  102 , blade assembly  104 , obturator assembly  106 , and dilator assembly  108  will be further described with reference to  FIGS. 2, 3, 4, and 8 , respectively. 
         [0035]    In general, insertion device  100  is assembled by inserting safety needle assembly  102  through handle hole  110  and into blade assembly  104  until safety needle assembly  102  is distal to the distal end of blade assembly  104 . Then, the combination of safety needle assembly  102  and blade assembly  104  is inserted through obturator assembly  106 . Then, obturator assembly  106 , blade assembly  104 , and safety needle assembly  102  are connected to dilator assembly  108 . A more detailed description of the assembly and operation of insertion device  100  will be further described with reference to  FIGS. 2-8 . 
         [0036]      FIG. 2  illustrates a safety needle according to aspects of the present invention. 
         [0037]    As shown in the figure, safety needle  102  includes cannula  202 , cannula tip  204 , stylet  206 , stylet port  208 , stylet tip  214 , housing  210 , hub  212 , and connection means  216 . 
         [0038]    Cannula  202  is preferably constructed from a generally rigid material, such as metal or plastic, but other rigid materials may be considered. It may be extruded, welded, molded, or manufactured by any other method that would result in a generally rigid material. Cannula  202  is connected to hub  210  such that there is no relative movement between hub  210  and cannula  202 . The connection may be via any mechanical means (a non-limiting example of which includes overmolding), adhesive means (a non-limiting example of which includes UV adhesive), or any other means that would create a bond between housing  210  and cannula  202  to prevent relative motion between the two components. 
         [0039]    Cannula tip  204  is designed to penetrate through tissue, and therefore it is relatively sharp. Cannula tip  204  may be manufactured by any known means to create a beveled tip, a conical tip, a crown tip, or any other geometry that is known in the art to provide a tip sharp enough to penetrate tissue. 
         [0040]    Stylet  206  is preferably constructed from a generally rigid material, such as metal or plastic, but other rigid materials may be considered. It may be extruded, welded, molded, or manufactured by any other method that would result in a generally rigid material. Stylet  206  is connected to housing  210  such that there may be relative motion between the two components. The outer diameter of stylet  206  is smaller than the inner diameter of cannula  202 , and stylet  206  is slidably positioned inside of cannula  202 . 
         [0041]    Referring now to  FIG. 6 , housing  210  is a generally rigid component that is either machined or molded out of plastic. Housing  210  is connected to cannula  202  and to hub  212 . The center of housing  210  is open to accommodate spring  610  and allow spring  610  to be compressed and uncompressed during use. 
         [0042]    Stylet  206  is connected to spring  610  via any mechanical, chemical or adhesive means that would create a bond between the two components. In an alternate embodiment, stylet  206  and spring  610  may both be connected to an intermediate part, such that stylet  206  and spring  610  are effectively bonded together. Spring  610  is connected to housing  210  and hub  212  via any mechanical, chemical or adhesive means that would create bond between the two components. In yet another alternate embodiment, spring  610  may freely float in between stylet  206  and hub  212  such that no bond between components is required. 
         [0043]    Referring back to  FIG. 2 , stylet tip  214  is designed to avoid penetrating through tissue, and therefore it is relatively blunt and closed at the distal end. Stylet tip  214  may be manufactured by any known means to create a curved tip, a bullet tip, a flat tip, or any other geometry that is known in the art to create a closed distal tip that will avoid penetrating tissue. 
         [0044]    Stylet port  208  is an open section in stylet  206  that is proximal to stylet tip  214  and distal to cannula tip  204  when spring  610  is uncompressed. Stylet port  208  may be manufactured by traditional grinding or machining techniques or by more advanced techniques, including electric discharge machining (EDM), chemical etching, or laser machining 
         [0045]    Referring back to  FIG. 6 , hub  212  is a generally rigid component that is either machined or molded out of plastic. Hub  212  is connected to spring  206  and to housing  210 . Hub  212  includes connection means  216  such that hub  212  may be connected to an external source for fluid drainage or administration. 
         [0046]    Referring back to  FIG. 2 , connection means  216  is shown as a threaded connection, however any suitable connection means (a non-limiting example of which includes a snap fit) that provide for connection of a fluid drainage or administration device is acceptable. 
         [0047]    Referring to  FIGS. 2 and 6 , in operation, a user grasps hub  210  or another component that may be coupled to hub  210  and advances safety needle assembly  102  toward a patient&#39;s skin. The first component of safety needle assembly  102  that contacts the skin is stylet tip  214 . As the user continues to push safety needle assembly  102  into the skin, the blunt stylet tip  214  transfers the pushing force through stylet  206 , compresses spring  610 , causes cannula  202  to move relative to stylet  206 , and allows cannula tip  204  to move toward the skin. 
         [0048]    When the pushing force is sufficient enough, cannula tip  204  will contact the skin and the sharp tip will penetrate the skin and soft tissues underneath the skin. When cannula tip  204  reaches an area of little or no resistance, spring  610  will uncompress, allowing stylet  206  to move forward again such that stylet tip  214  is distal to cannula tip  204 , and stylet port  208  is exposed to the area. Areas of little or no resistance include fluid (or air) filled spaces such as the plerua, lungs, or any other fluid filled space the user desires to reach. 
         [0049]    To confirm that safety needle assembly  102  is in the correct location, the user may connect a fluid drainage device to connection means  216  and use the fluid drainage device to pull fluid or air from the area as means of confirmation. Fluid drainage devices that may be used include syringes, suction canisters, wall suction, and any other means that may operate to pull fluid from the patient to confirm appropriate placement of safety needle assembly  102 . 
         [0050]      FIG. 3  illustrates a blade assembly according to aspects of the present invention. 
         [0051]    As shown in the figure, blade assembly  104  includes shaft  302 , distal tip  304 , blades  306  and  308 , handle  310 , follower shaft  312 , and follower  314 . 
         [0052]    Shaft  302  is a rigid tube and is preferably made of metal, however any other rigid material would suffice. Shaft  302  is connected to follower shaft  314  such that there is no relative motion between the two components. The connection may be made via mechanical, adhesive, or chemical means. Shaft  302  is also connected to blades  306  and  308 . The connection is preferably a welded connection, however other connection means may be employed. For example, shaft  302  may contain one or more slots at its distal end and blades  306  and  308  may contain one or more matching slots such that blades  306  and  308  may be assembled on to shaft  302  by sliding slotted sections of blades  306  and  308  on to the corresponding slots at the distal end of shaft  302 . 
         [0053]    Distal tip  304  is at the distal end of shaft  302  and is operable to provide a leading edge for blades  306  and  308 . Distal tip  304  may be produced by any conventional tip grinding or finishing process, and it may be a beveled tip, a conical tip, a crown tip, or any other tip that would provide an appropriate leading edge for blades  306  and  308 . 
         [0054]    Blades  306  and  308  are preferably constructed from metal, more preferably from stainless steel, however any material suitable for medical applications would suffice. Blades  306  and  308  are operable to cut the skin of a patient, and as such are sufficiently sharp to cut skin. The specific shape, grind angles, and tip angles may be of any dimensions such that the effect of cutting skin may be accomplished. Blades  306  and  308  are attached to shaft  302  as previously described. 
         [0055]    Handle  310  includes handle top  320  and cam  316 . Handle  310  is preferably made of plastic via either machining or molding, however any other suitable materials or manufacturing methods may be used. Handle top  320  is designed to be gripped by a user in order to rotate handle  310  relative to follower shaft  312  and follower  314 . Rotating handle top  320  and the motion of follower shaft  312  and follower  314  will be further discussed with reference to operation of blade assembly  104  below. Cam  316  is a slot within handle  310  in which follower  314  travels. Cam  316  may be constructed with any geometry that will provide the desired motion of follower  314 . 
         [0056]    Follower  314  and follower shaft  312  are both preferably made of plastic via either machining or molding, however any other suitable materials or manufacturing methods may be used. In some embodiments, follower  314  and follower shaft  312  may be a single component, however they are shown here as two separate components. Follower  314  and follower shaft  312  are bonded together by any suitable means that will effectively prevent relative motion between the two components. In addition, shaft  302  is bonded to follower  314  and follower shaft  312  to prevent relative motion between the three components. 
         [0057]    In operation, a user will turn handle  310  to effect a linear movement of shaft  302 . The user will grasp handle top  320  with one hand and dilator assembly  108  (not shown) with the other hand. Handle  310  therefore only rotates, and does not move in a linear direction when handle top  320  is turned.  FIG. 3  shows blade assembly  104  with blades  306  and  308  fully deployed. To retract blades  306  and  308 , the user would turn handle top  320  in the appropriate direction. Turning handle top  320  causes cam  316  to rotate. As cam  316  rotates, follower  314  moves in a linear manner such that follower  314  moves closer to handle top  320 . To deploy blades  306  and  308 , the user would turn handle top  320  in the opposite direction. 
         [0058]      FIG. 4  illustrates an obturator assembly according to aspects of the present invention. 
         [0059]    As shown in the figure, obturator assembly  106  includes obturator tip  402 , obturator shaft  404 , handle cover  408 , and obturator hub  410 . All components of obturator assembly  106  are preferably made from plastic via either machining or molding processes, however any suitable material or manufacturing method may be used to create the component. 
         [0060]    Obturator tip  402  is operable to enlarge an opening in the skin, and includes blade slot  412 . Blade slot  412  is operable to provide a pathway for blades  306  and  308  to be deployed beyond the distal-most portion of obturator tip  402  and to be fully retracted within obturator tip  402 . Obturator tip  402  is connected to obturator shaft  404  by any suitable means that would prevent relative motion between the two components. In an alternate embodiment, obturator tip  402  and obturator shaft  404  may be a single component. 
         [0061]    Obturator shaft  404  is operable to travel within the enlarged opening created by obturator tip  402 , and includes obturator slot  406 . Obturator slot  406  is present to reduce weight and manufacturing costs. In an alternate embodiment, obturator slot  406  may be omitted entirely such that obturator shaft  404  is a continuous tube with no openings in its diameter. 
         [0062]    Obturator hub  410  is connected to obturator shaft  404  by any means that would create a bond to prevent relative motion between the two components. Obturator hub  410  is operable to constrain the linear motion of follower  314  (not shown), such that blades  306  and  308  can only extend from obturator tip  402  by a defined distance. 
         [0063]    Handle cover  408  is operable to attach to obturator hub  410  and cover cam  316  (not shown) such that a user cannot interfere with the operation of cam  316 . Handle cover  408  may be a single component or multiple components that can be attached together. Additionally, in an alternate embodiment, handle cover  408  and obturator hub  410  may be a single component. 
         [0064]    Returning to  FIG. 1 , and with reference to  FIGS. 2-4 , assembly of insertion device  100  will be described. 
         [0065]    To assemble insertion device  100 , safety needle  102  is inserted through handle hole  110  and extends through the inner diameter of shaft  302  of blade assembly  104 , extending beyond distal tip  304 . The combination of safety needle  102  and blade assembly  104  is inserted through the inner diameter of obturator shaft  404  until obturator hub contacts cam  316  of blade assembly  104 . Handle cover  408  is then installed to cover cam  316 . Finally, the entire assembly is inserted through the inner diameter of dilator assembly  108  to complete the assembly process. There are no connections between dilator assembly  108  and the rest of the components; a simple press-fit interaction serves to keep dilator assembly  108  connected to the rest of the components. In an alternate embodiment, dilator assembly  108  may detachably lock to obturator assembly  106 . Dilator assembly  108  will be further described with reference to  FIGS. 6-8 . 
         [0066]      FIGS. 5A-B  illustrate an alternate embodiment of a blade assembly and an obturator assembly according to aspects of the present invention. 
         [0067]    As shown in the figures, obturator tip  502  includes cutout  504  to accommodate safety needle  102 . A blade slot similar to blade slot  412  provides space for blade  506  to deploy and retract. 
         [0068]    In this embodiment, blade  506  is a single blade instead of multiple blades as previously described. The single blade may be attached to shaft  302  by any means previously described. If attaching multiple blades to the outer diameter of shaft  302  is difficult to accomplish, this alternate embodiment may be employed, as methods to attach a single blade to a shaft are well known in the art. 
         [0069]    In attaching blade  506  to shaft  302 , a difficulty is encountered as safety needle  102  and blade  506  cannot be longitudinally coaxial with each other as is possible with the multiple blade design. Therefore, it is necessary to create cutout  504  to accommodate safety needle assembly  102 . In this embodiment, blade  506  slides along the outer diameter of safety needle assembly  102 . 
         [0070]    Testing has proven that, even though safety needle  102  is not concentric with respect to the rest of insertion device  100 , the ability of blade  506  to enlarge the pathway created by safety needle  102  is not impacted, and the performance of insertion device  100  is not diminished. 
         [0071]    In yet another alternate embodiment, and with further reference to  FIGS. 3-4 , it may be desirable to eliminate the need to turn handle  320  to deploy and retract blades  306  and  308 . In such an embodiment, blade assembly  104  may contact a spring that rests on obturator hub  410 . There may be a window in handle cover  408  such that the user&#39;s finger could reach blade assembly  104  through the window. Access to blade assembly  104  may also be available via obturator slot  406 . When the user desires to deploy the blades, the user would extend a finger into the window and press down on blade assembly  104 , compressing the spring and exposing the blades. After using the blades, the user would remove his/her finger from blade assembly  104 , which would then automatically retract blades  306  and  308  into obturator assembly  106  as the spring uncompressed. 
         [0072]      FIG. 6  illustrates a first step in inserting the insertion device according to aspects of the present invention. 
         [0073]    As shown in the figure, system  600  includes skin  602 , soft tissue  604 , and ribs  606  and  608 . 
         [0074]    Prior to inserting device  100  into a patient, a user will palpate the skin to determine the appropriate insertion point between ribs  606  and  608 . Once the desired location is found, the user begins to insert insertion device  100 . While not shown in  FIG. 6 , when first inserting insertion device into the patient, blades  306  and  308  are not deployed and are located within obturator assembly  106  (similar to the device as shown in  FIG. 7 ). 
         [0075]    When inserting insertion device  100  into the patient, safety needle  102  is the first component to contact the patient&#39;s skin  602 . As described with reference to  FIG. 2 , pushing safety needle  102  against the patient&#39;s skin  602  causes stylet  206  to retract, exposing the sharp cannula tip  204  to the skin. As the user continues to push, cannula tip  204  cuts through skin  602  and soft tissue  604 . Soft tissue  604  may include muscle, fat, fascia, or any other soft tissues with which safety needle  102  may come in contact with during the procedure. 
         [0076]    A skilled user can generally tell when the desired location is reached, as a distinct decrease in resistance occurs. The decrease in resistance is an indication that safety needle  102  has reached the desired, fluid-filled location. To confirm that safety needle  102  has reached the desired location, the user will attach a fluid drainage device to hub  212  via connection means  216 . The user will then attempt to drain fluid from the area. If the desired fluid is drawn from the area, the user may continue with the procedure. If the desired fluid is not drawn from the area, the user may need to continue in attempts to find the desired location. 
         [0077]    Assuming the desired fluid has been located, the user then deploys blades  306  and  308  by turning handle  320  until handle  320  cannot be turned any more, meaning blades  306  and  308  are fully deployed. The user then advances insertion device  100  until blades  306  and  308  enter skin  602  to create a skin nick. If desirable, after creating the skin nick, the user may pull insertion device back such that blades  306  and  308  are not in skin  602 , rotate insertion device  100   90  degrees, and then advance insertion device again until blades  306  and  308  enter skin  602 . After one or more skin nicks are created, the user turns handle  320  in the opposite direction until it cannot be turned any more, meaning blades  306  and  308  are fully retracted. The user can then further advance insertion device  100 , which is further described with reference to  FIG. 7 . 
         [0078]    In an alternate method, the user may deploy blades  306  and  308  first, create a skin nick, and then retract blades  306  and  308 . The user may then proceed with inserting safety needle  102  into the patient as previously described, or the user may decide to forego using safety needle  102  and instead insert obturator assembly  106 , blade assembly  104 , and dilator assembly  108  into the desired space within the patient. 
         [0079]      FIG. 7  illustrates a second step in inserting the insertion device according to aspects of the present invention. 
         [0080]    As shown in the figure, insertion device  100  is pushed further into the patient. As insertion device  100  advances, obturator tip  402  expands the pathway created by safety needle  102  and the one or more skin nicks. The user holds safety needle  102  with one hand while advancing obturator assembly  106 , blade assembly  104 , and dilator assembly  108 . The distance between housing  210  and handle  320 , noted as “d”, will increase as the user continues to advance obturator assembly  106 , blade assembly  104 , and dilator assembly  108 . 
         [0081]    When obturator tip  402  reaches stylet tip  214 , the user may stop advancement. The user may use an appropriate imaging technique to determine when obturator tip  402  reaches stylet tip  214 . In an alternate embodiment, cannula  202  may include an indicator mark, such that when handle  320  no longer covers the indicator mark, obturator tip  402  has reached stylet tip  214 . 
         [0082]    The user can then remove components to prepare the patient for insertion of a catheter. Safety needle assembly  102 , blade assembly  104 , and obturator assembly  106  may all be removed from dilator assembly  108  at the same time. To remove the components, the user will grip dilator shaft  702  with one hand and handle cover  408  with the other hand. Dilator shaft  702  will be further described with reference to  FIG. 8 . While holding dilator shaft  702  steady, the user will pull back on handle cover  408 . This will serve to detach Safety needle assembly  102 , blade assembly  104 , and obturator assembly  106  from the press-fit connection to dilator assembly  108 . As the user continues to pull back on handle cover  408 , all components will be removed from dilator assembly  108 , leaving dilator assembly  108  in the body. 
         [0083]      FIG. 8  illustrates a final step in inserting the insertion device according to aspects of the present invention. 
         [0084]    As shown in the figure, dilator assembly  108  is in the patient. Dilator assembly  108  includes dilator shaft  702  and dilator hub  704 . Dilator shaft  702  is preferably made of plastic and may be extruded, molded, or manufactured in any other known way to create the desired geometry. Dilator hub  704  is also preferably made of plastic by any known method to create the desired geometry. Dilator hub  704  and dilator shaft  702  are connected by any known methods that would serve to prevent any relative motion between the two components. 
         [0085]    At this point in the procedure, the user will typically place a catheter through the lumen of dilator shaft  702  to reach the desired location within the body. Essentially, dilator shaft  702  is simply a conduit through which another device (i.e., a catheter) is placed. Once the catheter is placed in the desired location, dilator assembly  108  is removed from the patient. The user then completes the procedure by closing skin  602  around the catheter. 
         [0086]      FIGS. 9-10  illustrate an alternate embodiment of an insertion device according to aspects of the present invention. As shown in  FIG. 9 , insertion device  900  includes dilator assembly  902 , obturator assembly  904 , and safety needle assembly  906 . As shown in  FIG. 10 , insertion device  1000  includes blade assembly  1002 . 
         [0087]    Specific aspects of dilator assembly  902 , obturator assembly  904 , safety needle assembly  906 , and blade assembly  1002  will be further described with reference to  FIGS. 11-14 . 
         [0088]      FIG. 11  illustrates the process by which an obturator assembly is assembled for an alternate embodiment of the insertion device. 
         [0089]    As shown in the figure, blade assembly  1002  includes blades  1102  and  1104 , blade tube  1106 , extension tube  1108 , button  1110 , lock  1112 , cap  1114 , lumen  1116 , and shaft  1118 . Obturator blank  1100  includes obturator tip  1124 , blade slot  1120 , and button slot  1122 . 
         [0090]    Shaft  1118  is a rigid tube and is preferably made of metal, however any other rigid material would suffice. Shaft  1118  is connected to blade tube  1106  such that there is no relative motion between the two components. The connection may be made via mechanical, adhesive, or chemical means. Shaft  1118  is also connected to blades  1102  and  1104 . The connection is preferably a welded connection, however other connection means may be employed. As a non-limiting example, shaft  1118  may contain one or more slots at its distal end and blades  1102  and  1104  may contain one or more matching slots such that blades  1102  and  1104  may be assembled on to shaft  1118  by sliding slotted sections of blades  1102  and  1104  on to the corresponding slots at the distal end of shaft  302 . 
         [0091]    Blades  1102  and  1104  are preferably constructed from metal, more preferably from stainless steel, however any material suitable for medical applications would suffice. Blades  1102  and  1104  are operable to cut the skin of a patient, and as such are sufficiently sharp to cut skin. The specific shape, grind angles, and tip angles may be of any dimensions such that the effect of cutting skin may be accomplished. Blades  1102  and  1104  are attached to shaft  1118  as previously described. 
         [0092]    Blade tube  1106  is a rigid tube and is preferably made of metal, however any other rigid material would suffice. Blade tube  1106  is connected to shaft  1118  as previously described, and blade tube  1106  is also connected to extension tube  1108  such that there is no relative motion between the two components. The connection may be made via mechanical, adhesive, or chemical means. 
         [0093]    Extension tube  1108  is a rigid tube and is preferably made of metal, however any other rigid material would suffice. Extension tube  1108  is connected to blade tube  1106  as previously described, and extension tube  1108  is also connected to cap  1114  such that there is no relative motion between the two components. The connection may be made via mechanical, adhesive, or chemical means. 
         [0094]    Cap  1114  is a rigid body and is preferably made of metal, however any other rigid material would suffice. Cap  1114  is operable to connect to extension tube  108  and to connect to button  1110 . 
         [0095]    Button  1110  is a deflectable body and is preferably made of any resilient material that can be deflected and then return to its original position. Button  1110  is connected to cap  1114  as previously described. Button  1110  also includes lock  1112 , which protrudes from the side of button  1110  and is operable to secure blade assembly  1002  in a specific location. The operation of button  1110 , lock  1112 , and blade assembly  1002  will be further described with reference to  FIGS. 13-14 . 
         [0096]    The individual components of blade assembly  1002  may all be manufactured separately and connected together as described above, but in alternate embodiments blade assembly  1002  may be a single, continuous component. In other alternate embodiments, various combinations of the individual components may be combined into single components for ease of manufacturing. 
         [0097]    Obturator blank  1100  is preferably made from plastic via either machining or molding processes, however any suitable material or manufacturing method may be used to create the component. Obturator tip  1124  is operable to enlarge an opening in the skin, and includes blade slot  1120 . Blade slot  1120  is operable to provide a pathway for blades  1102  and  1104  to be deployed beyond the distal-most portion of obturator tip  1124  and to be fully retracted within obturator tip  1124 . 
         [0098]    Button slot  1122  is an opening within the shaft of obturator blank  1100 , and it is operable to provide an opening in which button  1110  may travel. The operation of button  1110  and its interaction with button slot  1122  will be further described with reference to  FIGS. 13-14 . 
         [0099]    In operation, blade assembly  1002  is inserted into obturator blank  1100  to create obturator assembly  904 . In some embodiments, obturator blank  1100  is created by molding  2  halves of the component that are not attached. The  2  halves may then be assembled around blade assembly  1002  before being connected by mechanical or chemical means. 
         [0100]      FIG. 12  illustrates the assembly process to create an alternate embodiment of the insertion device. 
         [0101]    As shown in the figure, safety needle assembly  906  is inserted through obturator assembly  904 . More specifically, safety needle assembly  906  is inserted through blade assembly  1002 , which is part of obturator assembly  904 . Safety needle assembly  906  is substantially similar in construction and operation to safety needle  102  from  FIGS. 2, 6, and 7 . Safety needle assembly  906  is releasably attached to obturator assembly  904  such that the components can be easily attached and detached. In some embodiments, and as a non-limiting example, there may be a tongue-in-groove connection between the two components such that a nominal amount of force is required to connect and disconnect, however in other embodiments there are no additional mechanisms to secure the components together. 
         [0102]    The combination of safety needle assembly  906  and obturator assembly  904  is then inserted through dilator assembly  902 . Dilator assembly  902  includes dilator shaft  1204  and dilator hub  1202 . Dilator shaft  1204  is preferably made of plastic and may be extruded, molded, or manufactured in any other known way to create the desired geometry. Dilator hub  1202  is also preferably made of plastic by any known method to create the desired geometry. Dilator hub  1202  and dilator shaft  1204  are connected by any known methods that would serve to prevent any relative motion between the two components. 
         [0103]    Obturator assembly  904  is releasably attached to dilator assembly  902  such that the components can be easily attached and detached. In some embodiments, and as a non-limiting example, there may be a tongue-in-groove connection between the two components such that a nominal amount of force is required to connect and disconnect, however in other embodiments there are no additional mechanisms to secure the components together. 
         [0104]      FIG. 13  illustrates a cross section of a dilator and an obturator of an alternate embodiment of the insertion device. 
         [0105]    As shown in the figure, the cross section shows obturator blank  1100  assembled with dilator assembly  902 . Obturator blank  1100  includes slots  1302  and  1304 . Slots  1302  and  1304  are operable to mate with lock  1112  of blade assembly  1002 . 
         [0106]      FIG. 14  illustrates a cross section of a dilator, obturator, and blade assembly of an alternate embodiment of the insertion device. 
         [0107]    As shown in the figure, the cross section shows an assembly of obturator blank  1100 , dilator assembly  902 , and blade assembly  1002 . Lock  1112  (not shown) is engaged with slot  1304 , locking blade assembly  1002  in place. If the user desires to move blade assembly  1002 , the user would deflect button  1110  (typically using finger pressure) to disengage lock  1112  from slot  1304 . Then, keeping pressure on button  1110  to maintain it in the deflected position, the user would pull button  1110  back towards slot  1302  until slot  1302  engaged with lock  1112 , thus locking blade assembly  1002  in a different position. 
         [0108]    Operation of the device during a medical procedure will now be described with reference to  FIGS. 9, 10, and 14 . In a medical procedure, the user will receive the device with blades  1104  and  1102  in the retraced position, where lock  1112  is engaged with slot  1302 . At this point, the only component protruding through obturator assembly  904  is safety needle assembly  906 . After the doctor determines the appropriate place to insert the device, safety needle assembly  906  is inserted to the desired location in a manner similar to that described with reference to  FIG. 6  and safety needle  102 . 
         [0109]    In order to create a larger incision in which dilator assembly  902  can fit, the user then depresses button  1110 , disengaging lock  1112  from slot  1302 . The user then advances button  1110  toward the distal end of the device, causing blade assembly  1002  to advance. When lock  1112  engages with slot  1304  the user releases button  1110 , locking blade assembly  1002  in place, exposing blades  1102  and  1104 . The user then advances the device until blades  1102  and  1104  enter the skin to create a skin nick. If desirable, after creating the first skin nick, the user may choose to pull the device back until blades  1102  and  1104  are not in the skin, rotate the device  90  degrees, and then advance the device again until blades  1102  and  1104  enter the skin again to create a second skin nick. 
         [0110]    After the user creates the desired skin nicks, the user depresses button  1110 , disengaging lock  1112  from slot  1304 . The user then retracts button  1110  toward the proximal end of the device, causing blade assembly  1002  to retract, fully retracting blades  1102  and  1104  inside the device. 
         [0111]    An advantage of this configuration is that it provides the ability of the user to actuate the blades with one hand, making the procedure more convenient compared to procedures performed with trocars requiring two hands to operate. 
         [0112]    As described with reference to  FIG. 7 , the user will then advance obturator assembly  904  and dilator assembly  902  further into the patient while holding safety needle assembly  906  to prevent it from moving further into the patient. When the tip of obturator assembly  904  reaches the tip of safety needle assembly  906 , the user may stop advancing the combination of obturator assembly  904  and dilator assembly  902 . The user may use an appropriate imaging technique to determine when obturator tip  1124  reaches the tip of safety needle assembly  906 . In an alternate embodiment, markers on the device may indicate when obturator tip  1124  reaches the tip of safety needle assembly  906 , eliminating the need to use an imaging technique. 
         [0113]    The user can then remove components to prepare the patient for insertion of a catheter. Safety needle assembly  906  and obturator assembly  904  may be removed from dilator assembly  902  at the same time, or separately as the user desires. To remove the components at the same time, the user would grip dilator assembly  902  with one hand and obturator assembly  904  with the other, and simply hold dilator assembly  902  still while pulling obturator assembly  904  until only dilatory assembly  902  is left in the patient. Alternatively, the user may first remove safety needle assembly  906 , then remove obturator assembly  904 . 
         [0114]    As discussed with reference to  FIG. 8 , at this time, only dilator assembly is left in the patient, and the user will typically place a catheter through the lumen of the dilator shaft  1204  to reach the desired location in the body. Once the catheter is in the desired location, dilator assembly  902  is removed from the patient, and the user completes the procedure by closing the skin around the catheter. 
         [0115]    The foregoing description of various preferred embodiments have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The example embodiments, as described above, were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.