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`US 20090099521Al
`
`c19) United States
`c12) Patent Application Publication
`Gravesen et al.
`
`c10) Pub. No.: US 2009/0099521 Al
`Apr. 16, 2009
`(43) Pub. Date:
`
`(54) CANNULA INSERTION DEVICE AND
`RELATED METHODS
`
`(76)
`
`Inventors:
`
`Peter Gravesen, Nordborg (DK);
`Heiko Arndts, Flensborg (DE)
`
`Correspondence Address:
`GOODWIN PROCTER LLP
`PATENT ADMINISTRATOR
`53 STATE STREET, EXCHANGE PLACE
`BOSTON, MA 02109-2881 (US)
`
`(21) Appl. No.:
`
`12/250,760
`
`(22) Filed:
`
`Oct. 14, 2008
`
`(30)
`
`Foreign Application Priority Data
`
`Oct. 16, 2007
`(DE) ...................... 10 2007 049 446.9
`Publication Classification
`
`(51)
`
`Int. Cl.
`A61M 5120
`(2006.01)
`(52) U.S. Cl. ........................................................ 604/136
`ABSTRACT
`(57)
`
`A cannula insertion device includes a housing defining an
`opening for receiving therethrough a cannula and further
`defining a channel, and a cannula forming a lumen, the can(cid:173)
`nula adapted for sliding movement within the housing from a
`retracted position to an extended position. When the cannula
`is in the retracted position, the lumen is located remotely from
`the channel and the channel is in fluidic communication with
`the opening. When the cannula is in the extended position, the
`lumen is in fluidic communication with the channel.
`
`27a
`
`18
`
`6
`
`Page 1 of 25
`
`

`

`Patent Application Publication Apr. 16, 2009 Sheet 1 of 15
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`Patent Application Publication Apr. 16, 2009 Sheet 2 of 15
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`Page 3 of 25
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`Patent Application Publication Apr. 16, 2009 Sheet 5 of 15
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`Page 6 of 25
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`Patent Application Publication Apr. 16, 2009 Sheet 9 of 15
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`Page 10 of 25
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`Patent Application Publication Apr. 16, 2009 Sheet 10 of 15
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`Page 11 of 25
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`Patent Application Publication
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`Apr. 16, 2009 Sheet 12 of 15
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`Page 13 of 25
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`Patent Application Publication
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`Apr. 16, 2009 Sheet 13 of 15
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`Page 14 of 25
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`Patent Application Publication
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`Apr. 16, 2009 Sheet 14 of 15
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`Page 16 of 25
`
`

`

`US 2009/0099521 Al
`
`Apr. 16, 2009
`
`1
`
`CANNULA INSERTION DEVICE AND
`RELATED METHODS
`
`CROSS-REFERENCE TO RELATED
`APPLICATION
`
`[0001] This application claims priority to and the benefit of
`German Patent Application Serial No. 10 2007 049 446.9,
`filed Oct. 16, 2007, the disclosure of which is hereby incor(cid:173)
`porated by reference herein in its entirety.
`
`FIELD OF THE INVENTION
`
`[0002] This invention relates generally to systems and
`methods for inserting a cannula into a patient and, more
`specifically, to a device that automatically inserts a cannula,
`as well as connects the cannula lumen to a channel within an
`infusion device.
`
`BACKGROUND
`
`[0003]
`In many cases, it is necessary to insert a catheter or
`cannula into the body, or a body part of, a patient. By means
`of the so-inserted cannula, it is then possible to infuse medici(cid:173)
`nally-required fluid or material. Another reason for the
`employment of a cannula may be to aid in insertion of a
`micro-dialysis probe into the body.
`[0004] To insert a cannula into a patient, a rigid needle is
`placed within the lumen of the cannula, and the needle and
`cannula combination is forced into the skin of a patient. Once
`the cannula combination is fully inserted, the needle is
`retracted, leaving the cannula in place. When performed
`manually, the penetration of the catheter-carrying needle into
`the body, however, may be considered uncomfortable for a
`patient, or may cause some other anxiety. Also, the subse(cid:173)
`quent manual withdrawal of the needle is often regarded by
`some patients as painful.
`[0005] Automatic cannula insertion devices have been
`developed to address these issues. Typically, a cannula is
`included in a stand-alone device called an insertion or injec(cid:173)
`tion set. In addition to the cannula and needle, the insertion set
`often includes a housing to which the cannula is attached
`during use. The housing may have an adhesive pad for adher(cid:173)
`ing the housing to the skin of the patient during use, as well as
`an internal void or chamber that is penetrated by an inlet and
`a septum. The needle passes through the septum, void, and
`into the lumen of the cannula. After insertion, the needle is
`withdrawn from the septum, which seals the void. Thereafter,
`a tube is connected to the inlet, thereby placing the lumen (via
`the void) in fluidic communication with an infusion device,
`intravenous (IV) drip bag, or other medical equipment. The
`above-described insertion sets may be acceptable for some
`patients, but the attached tube and medical device can be
`obtrusive, which may be undesirable in some cases. It would
`be desirable then, to incorporate the functionality of an inser(cid:173)
`tion set into an infusion device to minimize the attendant
`tubing and complications involved in connecting the insertion
`set to the infusion device.
`
`SUMMARY OF THE INVENTION
`
`[0006] The invention relates to an insertion device for a
`cannula, wherein the cannula is carried on a needle, as well as
`a cannula configuration that allows for automatic alignment
`of an inlet on the cannula with a channel in an infusion device,
`without having to separately connect a tube thereto. In com-
`
`bination with a drive apparatus, the needle can be displaced
`from a retracted position into an extended position, thus form(cid:173)
`ing a fluidic connection.
`[0007] During an insertion procedure described herein, a
`cannula is used in conjunction with a needle. The needle is
`used to penetrate the body. Subsequently, the needle is with(cid:173)
`drawn from the body, allowing the cannula to remain in its
`inserted position. Consequently, one advantage of the inven(cid:173)
`tion is to increase the comfort of a patient during the insertion
`and withdrawal of a catheter or cannula. This benefit may be
`achieved with a device for the insertion of a cannula of the
`type described herein, wherein the needle, after reaching its
`extended state, can be withdrawn quickly and automatically
`by a retraction apparatus.
`[0008] One embodiment of the invention allows the needle
`to not only quickly penetrate the body tissue (i.e., blood
`vessel, organ, or other body part) of a patient, but due to aid
`from the retraction apparatus, the needle is quickly with(cid:173)
`drawn from the body tissue and simultaneously, the inserted
`cannula remains within the body tissue. In this way, since the
`needle is relatively quickly withdrawn from the body tissue, a
`much more comfortable sensation is experienced than that
`associated with a slower insertion and withdrawal. Further,
`any sensation is transient. The retraction apparatus is acti(cid:173)
`vated, in any case, when the needle is already within the
`patient's tissue, that is to say, when the needle is in its
`extended position. Thereby, it is possible for the operator to
`insert the needle and its associated cannula to a sufficient
`depth to reach a desired position within the body tissue.
`[0009]
`In one embodiment, the driving element or needle
`plunger is subject to the force of a spring. The spring can be
`prestressed and restrained by an arresting apparatus from
`which it is released to carry out its driving function. The
`spring acts upon a drive mechanism, which includes at least
`one first part (e.g., a plunger), which is in driving contact with
`a free end of the spring and the drive mechanism includes one
`separate second part ( e.g., a support structure), indirectly
`activated by the spring. Thus, the second part is made slid(cid:173)
`ingly displaceable in a first direction by means of the motion
`of the first part and, conversely, separates itself therefrom
`upon a movement of the first part in an opposite direction.
`Such an arrangement reduces the weight, which contributes
`to momentum during the retraction of the needle. Simulta(cid:173)
`neously, the needle, upon its movement from the retracted
`position into the extended position, stabilizes the cannula
`sufficiently when so projected, so that that the insertion pro(cid:173)
`cedure can be reliably carried out.
`[001 OJ
`In certain embodiments, the needle, which is seated
`in the second part, is releasably held. Accordingly, the needle
`can disengage itself from the second part at the outset of a
`retracting motion and can be withdrawn without obstruction.
`In this way, the needle is not permanently affixed to the drive
`mechanism, an advantage which can be usefully employed to
`even move the needle more quickly, i.e., through more rapid
`increments of retractive motion.
`[0011] At the time that the needle is disconnected from the
`second part, nothing more than the weight of the needle need
`be placed in motion, an advantage which allows undimin(cid:173)
`ished acceleration. Since the movement of a needle within the
`body tissue can be uncomfortable, it is helpful if the displace(cid:173)
`ment of the needle can be accelerated so that it can be
`removed from the tissue in a minimal amount of time.
`[0012]
`In one embodiment, the activation of the needle is
`subjected to force by a separate retraction spring ( compres-
`
`Page 17 of 25
`
`

`

`US 2009/0099521 Al
`
`Apr. 16, 2009
`
`2
`
`sion type) dedicated thereto, which acts in a direction from
`the second part toward the first part. It is possible, then, that
`this retraction spring serving the needle can be employed to
`force the now-released needle away from the second part in a
`direction that withdraws it from the penetrated body tissue.
`The second part can include at least one holding element that
`retains the needle therein, and permits the needle to be sub(cid:173)
`sequently retracted from an extended position. The concept of
`"retraction" or "withdrawal," as used herein, is used to
`describe removal of the needle from the lumen of the cannula
`after full insertion or extension of the cannula. The method of
`construction of the holding element, that is, as to whether its
`retaining characteristic is due to mechanical, magnetic, or
`other induced forces, is of secondary importance for the pur(cid:173)
`pose of this description. During the interim within which the
`needle has not yet reached its extended position, the holding
`element acts to affix the needle within the second part. As
`soon as the second part has reached its final and extended
`position, the retention of the needle is no longer necessary.
`Accordingly, at this time, the holding element releases the
`needle, so that it departs from the second part and extricates
`itself therefrom.
`[0013]
`In one embodiment, the holding element is located
`in the exposed surface of an end of the second part, from
`which the needle projects. From this end surface of the second
`part, when in extended position, the tip of the needle comes
`into contact with another surface. This so designated "other
`surface" can well be a surface of the patient's tissue, wherein
`the cannula is in the process of being inserted. Otherwise, the
`contacted surface can even be a lining of a device housing. In
`any case, by means of an impact of the second part against a
`target surface, the holding element is released, i.e., the reten(cid:173)
`tion of the needle therein is ended.
`[0014]
`In one embodiment, the first part possesses an acti(cid:173)
`vation element, which, at the completion of needle extension,
`acts upon the needle holding element. In this case, the first
`part is employed to relieve the holding element of the second
`part from its retaining function. By means of the mechanical
`structure of the holding element the needle is released when
`the position of the holding element changes. If the principle of
`construction of the holding element is electromagnetic in
`character, then the activation means may open a switch,
`which will interrupt a supply of current to the magnetic sys(cid:173)
`tem. In such a case, the magnet becomes deprived of its
`power. Additionally, it is contemplated to displace a working
`magnet thereby terminating its holding ability. Additional
`methods for this removal of holding power are contemplated.
`[0015]
`In an embodiment of the invention, the activation
`means of the first part and also the holding element possess
`complementary, coacting, inclined surfaces. Motion of the
`activation means toward the holding element, which is carried
`out in a direction parallel to the needle, can be diverted to a
`motion not parallel, but rather angular therefrom. In this
`alteration, the angular direction could even be at a right angle.
`[0016] The needle is supported by the said retraction spring
`to lie against the first part. This constructive support can be
`used with or without a holding element. The retraction spring
`assures that the needle can be secured by means of one or
`more projections on the second part. This securement would
`hold the needle in place during the movement of the drive
`mechanism. When the needle and catheter begin to penetrate
`into the body tissue, the needle itself is subjected to a reaction
`force, which, without an element for holding, finally causes
`the needle to act contrary to the force of the retraction spring.
`
`Nevertheless, by means of an appropriate dimensioning of the
`retraction spring, arrangement can be made such that the
`needle-catheter combination penetrates sufficiently far into
`the subject body tissue.
`[0017] The first part may possess a second holding means
`to which the needle becomes secured during a withdrawal
`from the extended position. This holding means retains the
`needle firmly within the first part, so that the needle retracts by
`means of the reversing motion of the first part of the drive
`mechanism.
`[0018]
`In this arrangement, a second holding means con(cid:173)
`sists of a cavity in the first part. The needle, or if necessary, a
`thickened section of the needle, is then simply retainingly
`inserted into the first part and subsequently held there by a
`force of friction. The necessary frictional forces can be
`increased by an appropriate surfacing of the interior of the
`cavity and/or increasing the size of the active exterior of the
`needle.
`[0019] The first part and the second part are located in a
`housing. This housing possesses in the area remote from the
`drive spring, an end face that blocks the travel of the second
`part. If the second part makes contact with the end face of the
`housing, or places itself very close thereto, it will be held in
`position by the above described holding means. This prevents
`the second part from following the first part as it withdraws.
`[0020] A storage means for medicaments or a communi(cid:173)
`cating fluidic connection for the cannula is located in the
`second part. In one embodiment, the second part is secured to
`the cannula, so that after the withdrawal of the needle, the
`cannula remains in its extended position in the tissue of the
`patient. The medicament can then be infused through the
`cannula into the body. An input or outtake branching can also
`be joined to the cannula line. By means of the input or outtake
`device, a medicament can be applied or blood or the like can
`be withdrawn from the body.
`[0021] The drive mechanism functions with the aid of an
`inclined surface on which is formed a path for movement of
`the needle, since the inclined surface moves in a direction
`transverse ( or angular) to that of the needle. This path, which
`accommodates the perpendicular travel of the needle, ends in
`a steplike termination. With such a termination as described,
`the functional movement of the needle is thus decoupled from
`its penetrative direction. The needle is forced by the inclined
`surface and accordingly slides along this inclined surface,
`being augmented by the intervention of the drive mechanism.
`Because of the inclined surface, the needle is subjected to an
`angular resultant force, which causes the needle to move.
`Upon an activation of the drive mechanism, an additional
`force may be applied to alter the direction of motion of the
`needle.
`[0022] The above "step" is formed by a recess in the
`inclined surface. The needle, or an integral element thereof,
`drops into the recess once it has reached its final, extended
`position. This recess also blocks any additional movement of
`the inclined surface. The inclined surface possesses a helical
`configuration and moves in a rotatable body. This rotatable
`body comprises, for example, a cylindrical shape, and can
`form a part of the drive mechanism. When this body is rotated,
`then an effective area of the inclined surface forms a slidingly
`spiral path for the needle alone or for both the needle and the
`drive mechanism together. As the needle moves from its with(cid:173)
`drawn position into its extended position it may move with the
`drive mechanism. In this way, a relatively long length of the
`sliding path on the helical inclined surface is achieved with
`
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`US 2009/0099521 Al
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`Apr. 16, 2009
`
`3
`
`minimum space and an excessive dimensioning of the inser(cid:173)
`tion mechanism is thereby avoided.
`[0023]
`In one aspect, the invention relates to a cannula
`insertion device including a housing defining an opening for
`receiving therethrough a cannula and further defining a chan(cid:173)
`nel, and a cannula forming a lumen, the cannula adapted for
`sliding movement within the housing from a retracted posi(cid:173)
`tion to an extended position, wherein when the cannula is in
`the retracted position, the lumen is located remotely from the
`channel and the channel is in fluidic communication with the
`opening, and when the cannula is in the extended position, the
`lumen is in fluidic communication with the channel. In an
`embodiment of the above aspect, the cannula insertion device
`further includes a base connected to the cannula, the base
`defining an internal chamber in fluidic communication with
`the lumen. In another embodiment, the base further defines a
`chamber extension in fluidic communication with the internal
`chamber. In yet another embodiment, when the cannula is in
`the extended position, the chamber extension is aligned with
`the channel. In still another embodiment, a wall of the base
`defines the chamber extension.
`[0024]
`In another embodiment of the above aspect, the base
`includes a resilient sheath, the sheath defining a port substan(cid:173)
`tially aligned with the chamber extension. In another embodi(cid:173)
`ment, when the cannula is in the extended position, the port is
`aligned with the channel. In yet another embodiment, when
`the cannula is in the extended position, the sheath seals the
`opening. In still another embodiment, the cannula insertion
`device further includes a plunger for driving the cannula from
`the retracted position to the extended position. In another
`embodiment, the cannula insertion device further includes a
`needle disposed in the lumen when the cannula is in the
`retracted position. In another embodiment, the needle is
`adapted to be automatically withdrawn from the lumen when
`the cannula is in the extended position. In another embodi(cid:173)
`ment, the needle is adapted to be automatically disconnected
`from the plunger when the cannula is in the extended position.
`[0025]
`In another aspect, the invention relates to a method
`of inserting a cannula, the method including the steps of
`providing a housing defining an opening for receiving there(cid:173)
`through a cannula and further defining a channel, providing a
`cannula forming a lumen, the cannula adapted for sliding
`movement within the housing from a retracted position to an
`extended position, and extending the cannula from the
`retracted position, in which the lumen is located remotely
`from the channel and the channel is in fluidic communication
`with the opening, to the extended position, in which the lumen
`is in fluidic communication with the channel. In an embodi(cid:173)
`ment of the above aspect, the method further includes the step
`of piercing a skin of a patient with a needle and the cannula as
`the cannula moves from the retracted position to the extended
`position. In another embodiment, the method further includes
`the step of withdrawing the needle from the lumen automati(cid:173)
`cally when the cannula is in the extended position. In yet
`another embodiment, a plunger extends the cannula from the
`retracted position to the extended position, the plunger in
`contact with the needle. In still another embodiment, the
`method includes the step of disconnecting the needle from the
`plunger when the cannula is in the extended position. In
`another embodiment, the method includes the step of sealing
`the opening with the cannula when the cannula is in the
`extended position.
`
`BRIEF DESCRIPTION OF THE FIGURES
`[0026] Other features and advantages of the present inven(cid:173)
`tion, as well as the invention itself, can be more fully under-
`
`stood from the following description of the various embodi(cid:173)
`ments, when read together with the accompanying drawings,
`in which:
`[0027] FIG. 1 is a schematic sectional side view of an
`insertion device in a retracted position in accordance with one
`embodiment of the invention;
`[0028] FIG. 2 is a schematic sectional side view of the
`insertion device of FIG. 1 in an intermediate position;
`[0029] FIG. 3 is a schematic sectional side view of the
`insertion device of FIG. 1 in a second intermediate position;
`[0030] FIG. 4 is a schematic perspective view of a portion
`of an insertion device in accordance with another embodi(cid:173)
`ment of the invention;
`[0031] FIG. 5 is a schematic sectional side view of an
`insertion device in accordance with another embodiment of
`the invention;
`[0032] FIG. 6 is a schematic side view of an insertion
`device in a retracted position in accordance with another
`embodiment of the invention;
`[0033] FIG. 7 is a schematic side view of the insertion
`device of FIG. 6 in a withdrawn position;
`[0034] FIG. 8 is a schematic perspective view of an inser(cid:173)
`tion ramp in accordance with one embodiment of the inven(cid:173)
`tion;
`[0035] FIG. 9 is a schematic side view of an insertion
`device in a retracted position in accordance with another
`embodiment of the invention;
`[0036] FIG. 10 is a schematic side view of the insertion
`device of FIG. 9 in an extended position;
`[0037] FIG. 11 is a schematic side view of the insertion
`device of FIG. 9 in a withdrawn position;
`[0038] FIG. 12 is a schematic top sectional view of the
`insertion device of FIG. 9;
`[0039] FIG. 13 is a schematic top sectional view of the
`insertion device of FIG. 11;
`[0040] FIG. 14 is a schematic diagram of an exemplary
`infusion device microcircuit;
`[0041] FIG. 15A is a schematic perspective view of an
`automatically-aligning cannula in accordance with one
`embodiment of the present invention;
`[0042] FIG. 15B is a schematic top view of the cannula of
`FIG.15A;
`[0043] FIG. 16 is a schematic side sectional view of the
`cannula ofFIG. 15A in a retracted position from an associated
`housing;
`[0044] FIG. 17 is a schematic side sectional view of the
`cannula of FIG. 15A in an extended position;
`[0045] FIG. 18 is a schematic side sectional view of the
`cannula of FIG. 15A in the retracted position;
`[0046] FIG. 19 is another schematic side sectional view of
`the cannula of FIG. 15A in the extended position; and
`[0047] FIGS. 20A-20C are schematic side sectional views
`depicting a method of inserting an automatically-aligning
`cannula in accordance with one embodiment of the invention.
`
`DETAILED DESCRIPTION
`
`[0048] FIG. 1 depicts an embodiment of an insertion device
`for a catheter 1 having a housing 2, within which a needle 3 is
`affixed by a needle holder 4. On the end remote from the
`needle holder 4, the needle 3 carries a catheter or cannula 5. In
`this document, the terms "catheter" and "cannula" are used
`interchangeably and without limitation to described any tube(cid:173)
`like implement to deliver fluids to any body part of a patient.
`In the attached figures, for the sake of clarity, the representa-
`
`Page 19 of 25
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`US 2009/0099521 Al
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`Apr. 16, 2009
`
`4
`
`tion of the catheter 5 is enlarged. In general, the diameter of
`the catheter 5 is only slightly larger than the outside diameter
`of the needle 3.
`[0049] The needle 3, in a manner not shown, is so envel(cid:173)
`oped by a guide in the housing 2, that it can only move in a
`direction parallel to its longitudinal axis L. The design allows
`the needle 3 to be displaced into an extended position. In this
`extended position of the needle 3, depicted in FIG. 2, the
`catheter 5 is positioned at least partially outside the housing 2
`and thus penetrating into body tissue 6. Designated here as
`"body tissue" is to be understood, for example, the skin, vein,
`or organ of a patient.
`In order to move the needle 3 in conjunction with the
`[0050]
`catheter 5, a drive mechanism Vis provided. Alternative drive
`mechanisms are also described in FIGS. 6-13. The drive
`mechanism V depicted in FIGS. 1-3 possesses a drive spring
`16 which powers the drive mechanism V. Described in greater
`detail, the drive spring 16 acts upon a first part or plunger 17,
`which is positioned against a second part or support structure
`18. This support structure 18 can be loosely affixed to the first
`part or plunger 17 or, alternately, secured thereto by an addi(cid:173)
`tional spring (not shown), which would abut the housing 2. In
`another embodiment, a holding means can be installed to
`combine the first and second parts, respectively 17 and 18.
`This holding means may be any type of chemical, mechani(cid:173)
`cal, electromagnetic, or other fastener. In any case, the two
`parts 17 and 18 are made to move under the force of the drive
`spring 16 in the direction of the tissue 6 of a patient, as
`depicted by arrow 27a.
`In the support structure 18, the needle 3 is retained,
`[0051]
`in particular by means of two needle holding elements 19.
`These holding elements 19 project outward from the patient
`proximal end face 20 of the support structure 18. The two
`holding elements 19 each include endwise, remote from the
`end face 20, a hook 21, which is shown in FIGS. 1 and 2 as
`located on the top of the needle holder 4. The needle holder 4
`supports itself against the support structure 18 by means of a
`retraction spring 22. However, this needle holder 4 can only
`be displaced in the direction of the plunger 17 to such extent
`that it is permitted by the needle holding elements 19.
`[0052] Each of the hooks 21 on the needle holders 19 pos(cid:173)
`sesses on the end proximate to the plunger 17 an inclined
`outer surface 23. The plunger 17 is equipped on the side
`proximate to the support structure 18 with projections having
`inclined surfaces 24, which are complementary to the above(cid:173)
`mentioned surfaces 23. When the parts 17 and 18 are suffi(cid:173)
`ciently displaced by the force of the drive spring 16, the
`needle holding elements 19, projecting out of the end face 20
`of the support structure 18, make contact with a base wall 25
`of the housing 2. The holding elements 19 are detachably
`connected to the support structure 18. Accordingly, as the
`holding elements 19 make contact with the base wall 25,
`spring 16 continues to drive support structure 18 toward the
`base wall 25, causing the holding elements 19 to detach from
`the support structure 18. The continued movement of the
`support structure 18 in the direction of the base wall 25 forces
`the needle holding elements 19 in the direction of the plunger
`17, until the complementary inclined surfaces 23, 24 contact
`one another. At this point, the holding elements 19 are dis(cid:173)
`placed outward and thus free the needle holder 4 from the
`support structure 18. With this arrangement, the needle 3,
`activated by the force of a retraction spring 22, is moved in the
`direction of the plunger 17. At this point of operation, the
`compressed retraction spring 22 initially displaces the needle
`
`3 with a relatively greater acceleration. Accordingly, the
`needle 3 is forced backward out of the body tissue 6.
`[0053] The first part includes a recess 26, into which the
`needle holder 4 can retreat under the force of the retraction
`spring 22. This recess 26 is, in this case, simply shown as a
`cavity sized to match the needle holder 4. Other types of
`recesses are also contemplated. In function, the recess 26
`accepts the needle holder 4 with the thereto affixed needle 3
`and, at the same time, firmly secures the needle 3, so that, after
`the initial movement, the needle 3 can be retracted along with
`plunger 17 out of its extended position. The needle holder 4
`may be secured within the recess 26 by mechanical, chemical,
`magnetic, friction, or other means. At the same time, the
`needle 3 is relieved of the catheter 5, which remains in its
`embedded position in the patient's tissue 6. This displacement
`of parts is sh