Patent Publication Number: US-2007106226-A1

Title: Syringe with internal sleeve

Description:
BACKGROUND OF THE INVENTION  
      Field of the Invention: This invention relates generally to pumping devices adapted to resist contamination internal to the pump mechanism. In particular, the invention relates to medical syringes.  
      State of the Art: Syringes are known in the medical field, and typically include a plunger arranged for reciprocal travel inside of a barrel effective alternately either to inspire or eject fluid through a discharge orifice. A stopper carried at an end of the plunger forms a wiping fluid seal against the inside of the barrel. Retracting the plunger causes a vacuum, or pressure lower than ambient, effective to inspire treatment fluid into the barrel. Depressing the plunger causes an increased pressure inside the barrel, higher than ambient, effective to expel the treatment fluid from the barrel.  
      Syringes are commonly used during medical procedures as pump devices. A typical use for a syringe includes inspiring a treatment fluid into the syringe&#39;s barrel through the discharge opening by retracting the plunger, then depressing the plunger to expel the treatment fluid through the discharge opening. Often, a needle, or other device, may be affixed to the discharge end of the syringe to guide or otherwise manipulate the fluid discharged through the syringe&#39;s discharge opening. Other times, a syringe may be incorporated into a fluid flow circuit, such as by way of a length of tubing affixed to the syringe&#39;s discharge opening.  
      Multi-use of a syringe entails making a plurality of strokes of a plunger inside a syringe barrel. It is known that undesired particles, such as pathogens or microorganisms, can cross the wiping stopper seal during multiple strokes of the syringe, thereby compromising sterility inside the syringe barrel. Loss of sterility in a closed fluid system can place a patient at risk of nosocomical infection, or line sepsis, such as vascular line sepsis. Any sort of wiping seal, or vented barrier structure, is ineffective to resist entrance of microorganisms from the proximal syringe end for contact with an interior of the syringe barrel. Therefore, in many medical procedures, a syringe is typically removed from its sterile packaging, used only once, and then discarded.  
      Medical procedures do exist where multi-use of a syringe connected in-circuit at its discharge end to a closed fluid system is desirable. Often, the environment in which the syringe will be placed into service is not sterile, and can even be severely contaminated with pathogens, microorganisms, urine, feces, and other undesired particles. Use of a currently commercially available syringe in such an environment presents serious risk of infecting the patient with undesired particles that enter the syringe&#39;s proximal end and cross its wiping seal.  
      At least four different medical product companies currently offer embodiments of syringes that include protection of some sort to resist entrance of particles into the proximal end of the syringe. Utah Medical Products, of Midvale Utah, offers a closed needleless arterial blood collection kit under the product name Deltran®, which includes a proximally projecting plunger protection sheath. Edwards Lifesciences, LLC, of Irvine Calif. offers a closed injectate delivery system including a proximally projecting contamination shield integrated into the plunger. Becton, Dickinson and Company, of Franklin Lakes, N.J. offers a cardiac output injectate kit under the product number 682260, which includes Touchguard™ sheath for the plunger. And finally, Hospira, of Lake Forrest, Ill. offers a Thermodilution Cardiac Output Injectate System (product invoice THERMOSET—ICED) having a syringe incorporating a Contamination Sheath.  
      Certain commercially available syringes include a proximally projecting shroud that covers the plunger and is vented to the atmosphere. A vented shroud may advantageously permit sterilization incorporating a vacuum cycle, such as commonly employed with an ETO gas sterilization treatment. However, air inherently flows into, and out of, such a vented shroud during actuation of the plunger. The air flowing into a syringe through a vented shroud will inevitably transport undesired particles into the interior of the syringe. Therefore, all such vented syringes lack a truly effective hermetic proximal seal or barrier.  
      Commercially available shrouds often are formed from silicone material. Unfortunately, such silicone material has an affinity for dirt, or contaminants. A proximally projecting shroud presents a sizable exposed surface of material that can be characterized as a “dirt magnet.” The presence of a large exposed silicone surface can frustrate effective cleaning of the local environment surrounding that surface.  
      By experimentation, Applicants have determined that an unvented, proximally projecting shroud can sometimes interfere with actuation of the plunger by “ballooning” or inflating as the plunger is depressed toward a fully discharged position. The puffed-up portion of such an inflated shroud can interfere with the plunger&#39;s stroke, or create difficulty in gripping the plunger for retraction from a depressed position. The inflation problem is exacerbated in situations where the shroud volume (defined between a retracted shroud and plunger) is larger than the receiving volume available inside a barrel at a plunger-depressed position. Therefore, simply removing, or sealing, the shroud vent may not produce a desirable, hermetically sealed syringe.  
      There are disadvantages associated with handling a syringe&#39;s plunger indirectly through a proximally projecting external “boot” or shroud arranged to cover the plunger. Such a shroud generally interferes to obfuscate a user&#39;s tactile senses and thereby reduce feedback as the user manipulates the plunger. Shrouds, or rearwardly projecting “boots” are particularly intrusive and cumbersome when the plunger is substantially depressed. At such position, the shroud covering the plunger typically is bunched-up, or wrinkled. The bunched-up portion of shroud material can interfere with the user obtaining a sufficient purchase on the plunger to effect a retracting motion of the plunger.  
      Certain advances in the art of protecting proximal ends of syringes against contaminants are disclosed in US patents, including U.S. Pat. No. 6,830,564 to Gray, and U.S. Pat. No. 4,713,060 to Riuli. The entire disclosures of the aforementioned patents are hereby incorporated as though set forth herein in their entireties as background related to syringe construction. In the latter &#39;060 patent, Riuli discloses a flexible cover arranged to project proximally from the syringe&#39;s barrel and to cover the plunger. However, as illustrated in  FIG. 4 , the flexible cover is bunched-up at the fully depressed plunger. As previously discussed, such bunched-up cover material disadvantageously can make the plunger difficult to grasp.  
      In the former &#39;564 patent, Gray discloses several embodiments of syringes adapted in various ways to reduce entrance of contaminants into the syringe barrel cavity. Certain of Gray&#39;s embodiments include proximally projecting coverings for plunger structure which are arranged to fold at selected hinging locations. Other embodiments include proximally projecting covers arranged to cover the plunger and add one or more wiping seals, or provide a labyrinth barrier to particles at the barrels proximal end. One embodiment provides a proximal end seal arranged to wipe the shaft of the plunger. The disclosed embodiments are either expensive and difficult to manufacture, cumbersome to use, and/or fail to provide adequate resistance to undesired particles entering the barrel cavity from the proximal end.  
      It would be an improvement to provide a syringe including a sealing arrangement, for its proximal end, which is truly effective to resist contamination of the inside of the syringe from its proximal end. Such an improved syringe would then be capable of sustaining multiple-use in closed systems, in even a non-sterile medical environment, without placing the patient at risk of syringe-induced contamination. It would be a further improvement to provide a syringe having a hermetically sealed proximal end that does not interfere with operation of the syringe&#39;s plunger.  
     BRIEF SUMMARY OF THE INVENTION  
      The invention may be embodied as a syringe, including a barrel, a plunger and a sleeve. The barrel may be constructed in conventional fashion to extend along an axis between a proximal end and a distal end, and to have a discharge opening associated with the distal end. The plunger is conventionally arranged for reciprocal actuation of a stopper along the axis of the barrel. The sleeve is typically disposed between a shaft portion of the plunger and the barrel to cause distally directed motion of a portion of the sleeve inside the barrel as the plunger is actuated in a direction effective to cause a discharge from the syringe. A sleeve typically includes a tubular barrier element arranged to resist contact between a portion of an inside surface of the barrel and undesired particles attempting to enter the syringe from a proximal end of the barrel. Preferably, the sleeve is adapted to form a hermetic seal, for an interior working portion of the barrel, against intrusion of undesired particles from a proximal end of the syringe.  
      In general, a perimeter of the sleeve is anchored to structure associated with the barrel effective to form a sealed interface. Such sealed interface provides a proximal barrier around a perimeter of the barrel to resist contamination of the inside of the syringe by undesired particles attempting to enter the syringe from its proximal end. Sometimes, a sleeve is anchored to, and/or by, structure associated with a proximal end of the barrel. One operable sleeve may be characterized as a sock forming an uninterrupted barrier established at a sealed interface around a perimeter of a proximal end of the barrel. Certain sleeves are sized in length such that a distally directed motion of the sleeve causes a resilient extension of a tubular portion of the sleeve when the syringe is in a fully discharged configuration.  
      In one currently preferred embodiment, a plunger includes a shaft adapted at its distal end to carry a stopper. The sleeve is configured as an uninterrupted sock having a toe carried at a distal end of a tube, with a portion of the sock being disposed between cooperating portions of the plunger&#39;s shaft and the inside of a barrel of an assembled syringe. The stopper may be configured to trap the toe of the sock between the stopper and the distal end of the plunger&#39;s shaft.  
      In any case, a syringe structured according to certain principles of the invention includes a sleeve having a portion adapted for reciprocal motion inside a portion of the syringe barrel. An exemplary sleeve includes a tube element structured to form an axially extending barrier. A distal length of such tube is extendable into the barrel for disposition between a distal portion of the plunger&#39;s shaft and a working portion of the barrel. A distal portion of the tube is configured in harmony with the shaft to form a distal barrier. A proximal portion of the tube can be anchored to structure associated with the barrel effective to form a proximal perimeter barrier. In combination, the distal barrier, the axially extending barrier, and the proximal perimeter barrier are structured to resist contact between undesired particles, entering through the proximal end of the barrel, and an inside surface of the working portion of the syringe&#39;s barrel.  
      Sometimes, a syringe may also include anti-removal structure to resist accidental retraction of the plunger from engagement inside the barrel. One arrangement forming operable anti-removal structure includes a radially protruding rim carried proximate a distal end of the plunger. A circumference of that rim desirably has an outside diameter sized in harmony with an inside diameter of a ring carried by the barrel to form an annulus in which to accommodate a thickness of the sleeve in a sufficiently close fit to provide anti-removal feedback for a plunger in the barrel while still permitting assembly of the plunger into the barrel, and repetitive actuation of the syringe, without causing undue damage to the sleeve.  
      Certain embodiments of the invention may also include anti-rotation structure arranged to resist rotation of the plunger about a syringe&#39;s axis. Embodiments of syringes according to the invention may optionally include sleeve containment structure arranged to resist egress of a sleeve from substantial confinement inside the syringe&#39;s barrel. Sometimes, anti-rotation structure may additionally operate, in-part, as sleeve containment structure. Also, anti-rotation structure can be arranged to additionally resist accidental withdrawal of the plunger from an installed position inside the barrel. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      In the drawings, which illustrate what are currently considered to be the best modes for carrying out the invention:  
       FIG. 1  is an exploded assembly plan view of a first embodiment constructed according to certain principles of the instant invention;  
       FIG. 2  is a cross-section view taken through a midline along an axis of the embodiment illustrated in  FIG. 1  in a first assembled position;  
       FIG. 3  is a plan view of the embodiment illustrated in  FIG. 1  in a second assembled position;  
       FIG. 4  is an end view of one embodiment of structure arranged to resist rotation of a plunger installed in a syringe;  
       FIG. 5  is a plan view, partially in section, of a second embodiment of a syringe constructed according to certain aspects of the invention; and  
       FIG. 6  is a plan view, partially in section, of a portion of a third embodiment of a syringe constructed according to certain aspects of the invention. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS  
      A first embodiment of an improved syringe constructed according to certain principles of the invention is indicated generally at  100  in  FIGS. 1 through 3 . With particular reference to  FIG. 1 , syringe  100  includes a plunger  102  sized for reciprocal actuation inside barrel  104 . In the illustrated embodiment  100 , plunger  102  is first inserted into a sleeve  106 . Then stopper  108  is secured over sleeve  106  in engagement with holding structure, generally indicated at  110 , carried at distal end  112  of plunger  102 . The resulting assembly is then inserted into barrel  104  from its proximal end  114 . A proximal end  116  of sleeve  106  may then be anchored to barrel  104  to form a sealed interface. As best illustrated in  FIG. 2 , one operable anchoring arrangement includes stretching proximal end  116  of sleeve  106  over ears  118  to form a proximal barrier, generally indicated at  122 .  
      The proximal perimeter barrier  122 , formed between the sleeve  106  and the barrel  104 , is formed completely around a perimeter of the barrel  104 . Furthermore, the proximal barrier is typically arranged to form a static seal. By static seal, it is meant that no relative motion between components at the sealing barrier is required. An effective static seal may be characterized as a hermetic seal. Desirably, the proximal seal  122  is a hermetic seal effective to resist entrance of undesired particles, such as pathogens or microorganisms, into the barrel  104  (from its proximal end  114 ), for contact with its inside working surface, generally indicated at  126  in  FIG. 2 . Working surface  126  may be defined as that portion of barrel  104  that is wiped, or contacted, by stopper  108  during conventional actuation of syringe  100 .  
      With particular reference to  FIGS. 1 and 2 , in some cases, the barrel  104  with its installed sleeve  106  may be inserted into optional auxiliary finger support or finger loop structure  128 . It is within contemplation that optional finger structure  128  can include socket structure, generally indicated at  130 , configured to cause an additional clamping force effective to reinforce the seal formed at proximal perimeter barrier  122 . It is further within contemplation that such reinforcement structure may be provided as an alternatively configured socket  130 , such as simply socket  130  without including additional structure arranged to form finger holes  134 .  
      In some situations, it may be desirable to resist rotation of a plunger  102  that is installed in a barrel  104 . For example, the sleeve  106  may suffer damage due to excessive twisting about an axis of the barrel  104 . As one way to resist such damage, certain syringes may include structure configured to resist rotation of an installed plunger  102 . One such anti-rotation structure is illustrated in  FIG. 4 , and is generally indicated at  138 .  
      The illustrated anti-rotation structure  138  may be characterized as a clamshell plate having a substantially constant thickness in a direction into the page. Left side  140  and right side  142  are rotatably connected at hinge  144 . In the closed position illustrated, an opening  146  is defined in which to receive an axially extending shaft portion of a plunger, such as plunger  102 , for reciprocal actuation of the plunger in a barrel. The illustrated opening  146  provides structure configured in harmony with the plunger  102  effective to interfere with radially protruding structure of the plunger, thereby to resist rotation of the plunger. The left side  140  and right side  142  can be swung open about hinge  144 , and subsequently closed to surround a shaft portion of plunger  102  disposed within opening  146 .  
      Opening  146  may be arranged to permit a limited amount of rotation of a plunger  102 . Sometimes, it is desirable to permit a plunger to rotate a certain amount during actuation of a syringe. For example, in use of a syringe having a thumb hole  148  in plunger  102  (e.g., as illustrated in  FIG. 1 ), a user may feel more comfortable if the plunger  102  is permitted to rotate a certain amount as it travels along an axis of barrel  104 . Also, a certain amount of rotation of plunger  102  may be desirable to accommodate both left- and right-handed use of a syringe.  
      A closed anti-rotation structure  138  (or assembled components of anti-rotation structure), may conveniently be retained in a closed position inside a socket  130 , disposed proximally on top of an installed barrel  104 . Walls of the socket  130  can be arranged to resist an opening rotation of left side  140  and right side  142  about hinge  144 . As illustrated, anti-rotation structure  138  is maintained inside socket  130  by an installed capture behind one or more cantilevered arms  150 . Other known retention structure is workable, including friction fits between components, other arrangements causing a structural interference, adhesives, welding, heat staking, or other conventional fastening arrangements. An installed anti-rotation structure  138  may also be structured and arranged to cause a reinforcing clamping force on a proximal perimeter barrier  122  to further resist entrance of undesired particles into the barrel  104 .  
      Commercially available syringes typically include structure arranged to resist accidental extraction of the plunger from inside the barrel. In certain such syringes, a radially protruding rim  156  (see  FIG. 1 ) is structured in harmony with a cooperating barrel ring  158  disposed to protrude radially inward adjacent the proximal entrance of barrel  104 . A user of such commercially available syringe obtains feedback in the form of increased resistance to further retraction of the plunger as the rim  156  and barrel ring  158  come into contact at a fully retracted position. Such an arrangement of anti-separation structure is also operable in syringes according to the instant invention, although it is currently preferred to size the rim  156  and barrel ring  158  to accommodate the sleeve  106  for repetitive actuation without imparting damage to the sleeve. Anti rotation structure  138  is also one example of alternative structure effective to resist accidental complete extraction of a plunger  102  from engagement inside barrel  104 .  
      In certain syringes structured according to the instant invention, an annulus between a rim  156  and a barrel ring  158  is desirably provided in which to receive the thickness of the sleeve  106 . Such annulus may be sized to facilitate assembly of a plunger  102  and sleeve  106  into a barrel  104 , and still provide anti-removal feedback at a fully retracted plunger position. Also, the portions of the rim  156  and barrel ring  158  which contact the sleeve  106  desirably include sufficiently large radii to resist formation of a stress concentration pressure point in the sleeve wall, and corresponding damage or reduction in useable life of a syringe&#39;s sleeve  106 .  
      Sometimes, it is desirable to construct the various components of a syringe from materials sized to provide substantially the same “feel” to a user as is provided by commercially available syringes. The “feel” includes the force necessary to depress or retract a plunger  102  with respect to the barrel  104 . The sizes, and materials of construction, of a rim  156 , sleeve  106 , stopper  108 , and inside surface  126  may be adjusted to create substantially the same “feel” as commercially available syringes lacking an effective proximal end barrier.  
      However, sometimes it is desirable to structure a syringe to take advantage of the disparity between strength of a user&#39;s hand in a syringe discharge direction, compared with the reduced strength of the user&#39;s hand in a syringe filling direction. In such case, a resilient sleeve  106  may be structured to be shorter in a length direction “L” than a barrel  104 . Such a “short” sleeve  106  therefore assists in retracting the plunger  102  to fill the syringe. The additional force to axially “stretch” such a sleeve  106  to discharge treatment fluid from a syringe can easily be accommodated by the user&#39;s superior strength of motion in the discharge direction.  
      In certain cases, socket structure  130  may be configured to define an axially extending compartment in which to hold an everted portion  160  (see  FIG. 3 ) of sleeve  106 , thereby to resist contact between the sleeve  106  and potentially damaging objects external to the syringe. Anti-rotation structure  138 , or an alternatively structured aperture having a close-fit to the plunger  102 , can trap, or confine, the sleeve  106  inside the barrel  104  or socket  130 . Anti-rotation structure  138  may alternatively be structured to help define an axially extending cavity in which to confine a sleeve  106 . In addition to providing an enhanced safety aspect, a syringe structured to hold the sleeve  106  substantially inside the barrel  104  or in a socket, such as socket  130 , may also provide a more pleasing appearance.  
      A workable sleeve  106  maybe manufactured from material capable of being formed into a membrane effective as a barrier to resist undesired particles. One effective sleeve  106  can be characterized as a condom. A currently preferred sleeve material for certain medical applications includes Nitrile. It is within contemplation for a sleeve to be formed from polymerized plastic material, such as commonly available poly bag material. Latex is an operable sleeve material, although not currently preferred due to its potential for causing allergic reactions in certain patients. Sleeves  106  may be formed using a variety of known manufacturing techniques, including extrusion, injection molding, casting, and dip molding or spray application on a male mandrel.  
      Preferred sleeves  106  include a substantially cylindrical length portion disposed between proximal and distal ends. Such length portion forms an axially extending barrier against undesired particles. One currently preferred sleeve  106  (e.g., see  FIGS. 1-3 ), is configured to provide an uninterrupted barrier that can be sealed with respect to a barrel  104  at its proximal end. Such sleeve  106  may be characterized as an approximately tubular sock having a toe, generally indicated at  166 , disposed at its distal end  168 . Toe  166  inherently forms one embodiment of a distal barrier to entrance of undesired particles into the syringe. Anchoring the perimeter of such sock to structure associated with a barrel  104  can form a hermetically sealed interface around a perimeter of the barrel  104  and provide a total barrier to resist entrance of pathogens, or undesired particles, from the proximal end of a syringe. An inside surface of an installed sleeve  106  maybe defined as the surface adjacent to surface  126  of barrel  104 . Undesired particles may contact the exterior surface of the sock, and may even technically be drawn “into” the barrel  104  as a distal portion of the sock moves distally inside the barrel. However, the undesired particles cannot cross the barrier, formed by the sock, to contact the inside working surface  126  of the barrel.  
      The embodiment  100  in  FIGS. 1-3  illustrates a sleeve  106  in association with a syringe that is substantially a stock commercially available syringe. Such an arrangement provides an advantage by incorporating a minimal number of additional components with certain commercially mass-produced, and low cost, components. However, it is within contemplation to make additional modifications to certain portions of a syringe to form alternative embodiments structured according to principles of the instant invention. Certain of such modifications are illustrated in  FIGS. 5 and 6 .  
       FIG. 5  illustrates an alternative syringe, generally indicated at  169 , constructed according to certain principles of the instant invention. Syringe  169  includes an alternative proximal anchoring arrangement for a sleeve  106 , generally indicated at  170 . Anchor  170  includes a ring  172  structured to clamp an everted proximal portion of sleeve  106  against a cylindrical extension  174  of barrel  104 ′. Such ring  172  may be self-biased to exert a radial clamping force. It is within contemplation for a ring  172  to be structured alternatively to trap a proximal portion of a sleeve against an inside cylindrical surface of a barrel  104  or  104 ′. In such case, the alternative ring may also operate to resist unintentional retraction of a plunger from within the barrel. Also, an alternatively structured ring may operate to contain the sleeve  106  inside the barrel, or other protective area. Furthermore, an alternatively structured ring may include anti-rotation structure to resist rotation of an installed plunger.  
       FIG. 5  also illustrates an alternative stopper arrangement, generally indicated at  180 , that forms an alternative distal perimeter seal and distal anchor arrangement. A resilient ring  182 , such as an O-ring, is engaged in a receiving trough  184  carried on distal end of plunger  102 ′. Such ring  182  represents an alternative structure effective to affix, or anchor, a distal portion of sleeve  106  to a plunger  102 ′. Ring  182  desirably forms a static distal perimeter seal disposed between the sleeve  106  and trough structure in plunger  102 ′. Such a static perimeter seal serves as an effective back-up seal to the primary distal seal provided by the uninterrupted membrane forming toe  166  (which is an absolute barrier to undesired particles). Additionally, illustrated ring  182  forms a separate wiping seal in cooperation with working surface  126  to control inspiration and discharge of treatment fluids.  
       FIG. 6  illustrates a portion of another alternative syringe, generally indicated at  188 , constructed according to certain principles of the instant invention. Syringe  188  includes a second alternative distal perimeter seal arrangement, generally indicated at  190 . Distal perimeter seal  190  includes a resilient ring  192 , such as an O-ring, disposed to compress the perimeter of an open distal portion of sleeve  106 ′ against the circumferentially extending surface of trough  194  carried at a distal end of plunger  102 ′. Therefore, distal perimeter seal  190  is a static seal effective to resist entrance of undesired particles into the syringe for contact with surface  126 .  
      The anti-removal rim  156 , barrel ring  158 , and stopper  108  may be configured identically to corresponding components of a comparable commercially available syringe. Desirably, trough  194  is disposed proximal to anti-removal rim  156 , as illustrated. Such positioning eliminates pinching contact of the sleeve  106 ′ between surface  126  and/or barrel rim  158  effective to enhance robustness and working life of the sleeve  106 ′. Furthermore, in such a syringe  188  having such a configuration, the “feel” during actuation of the syringe may be substantially the same as that produced in a comparable syringe lacking any proximal barrier.  
      Embodiments of the invention may be constructed and arranged such that, at a plunger-depressed position, the internal sleeve  106 ,  106 ′ is disposed substantially parallel to and congruent with, the inner wall forming the barrel. Therefore, very little air is trapped between such a sleeve and the working surface of the barrel. Such an arrangement forms a device capable of withstanding a vacuum cycle, such as associated with ETO sterilization, without the potential for sheath swelling, and potential rupture, associated with an unvented external sheath.