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  Positive displacement flush syringeUSPTO Application #: 20080021414Title: Positive displacement flush syringe Abstract: A positive displacement flush syringe includes a barrel having a chamber for retaining fluid and an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber. A plunger having a stopper which is slidably positioned in said chamber for driving fluid out of the chamber by movement of the stopper relative to the barrel is provided. Further, structure is provided to move fluid distally in the passageway after fluid has been delivered from the chamber and the stopper is in contact with the distal wall of the chamber. (end of abstract)
Agent: David W. Highet, Vp And ChiefIPCounsel Becton, Dickinson And Company - Franklin Lakes, NJ, US Inventor: THOMAS ADAM ALHEIDT USPTO Applicaton #: 20080021414 - Class: 604220000 (USPTO) Related Patent Categories: Surgery, Means For Introducing Or Removing Material From Body For Therapeutic Purposes (e.g., Medicating, Irrigating, Aspirating, Etc.), Treating Material Introduced Into Or Removed From Body Orifice, Or Inserted Or Removed Subcutaneously Other Than By Diffusing Through Skin, Material Introduced Or Removed Through Conduit, Holder, Or Implantable Reservoir Inserted In Body, Means Moved By Person To Inject Or Remove Fluent Material To Or From Body Inserted Conduit, Holder, Or Reservoir, Injector Or Aspirator Syringe Supported Only By Person During Use (e.g., Hand Held Hypodermic Syringe, Douche Tube With Forced Injection, Etc.), With Piston Or Plunger For Expelling Material From Body Or Injector Reservoir, The Patent Description & Claims data below is from USPTO Patent Application 20080021414. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001] This application is a divisional of U.S. application Ser. No. 10/754,870 filed Jan. 9, 2004. BACKGROUND OF THE INVENTION [0002] The present invention relates to syringe assemblies and particularly to syringe assemblies for use in flush procedures, for vascular access devices (VAD's). [0003] VAD's are commonly used therapeutic devices. There are two general classifications of VAD's, peripheral catheters and central venous catheters. If not properly maintained, VAD's can become occluded. To ensure VAD's are used properly and do not become occluded, standards of practice have been developed. These standards include a cleaning procedure, which is commonly referred to as a flush procedure or flushing a catheter. [0004] VAD standards of practice usually recommend flush procedures be performed after catheter placement, before fluid infusion, and before and after drug administration, blood sampling, transfusions and parenteral nutrition. The goal of these flush procedures is to confirm catheter patency, avoid drug incompatibilities, ensure the complete drug dose administration, prevent thrombus formation and minimize the risk of blood stream infections. Flush procedures require different types and amounts of flush solutions. The most commonly used flush solutions are saline and or heparin lock solution. The type of flush solution and amount vary depending on the specific type of catheter. Flush solution volumes between 5 and 10ml are most common but can range from 1 to 20 ml. Flush procedures also require that care be taken to prevent blood reflux into the catheter. Reflux in I.V. therapy is the term commonly used to describe the fluid that is drawn back into the catheter after a flush procedure. The concern is that the reflux fluid contains blood or solution that could cause the catheter to occlude. To ensure that reflux does not occur, flush procedures suggest two techniques: 1) at the end of the flush solution delivery, the user maintains pressure on the syringe plunger while clamping the I.V. line; or 2) while delivering the last 0.5 ml of flush solution disconnect the syringe from the I.V.port or clamp the I.V. line. Either technique maintains positive pressure on the fluid in the VAD to prevent reflux of fluid and blood. [0005] For flush procedures, the I.V. line refers to the system containing a VAD, tubing set with clamp and may terminate with a port or valve. The most common types of I.V. ports are covered by pierceable septums or pre-slit septums and are known in the art and sometimes referred to as "PRN" from the Latin pro re nata meaning "as the need arises". The septum is preferably made of rubber or another elastomeric material, which permits insertion of a sharp needle cannula in order to infuse fluids or to withdraw fluids from the catheter. Upon withdrawal of the needle cannula the septum seals itself. Ports having pre-slit septums are used with blunt cannula or the frustoconically shaped tip of a syringe barrel. The syringe tip or the blunt cannula (which is usually attached to a syringe) is gently pushed through the pre-slit septum to establish fluid communication. [0006] I.V. valves, another type of terminal I.V. access device that does not require a needle having a sharp tip, are activated by the frustoconically shaped tip of a syringe barrel to allow fluid communication between the interior of the syringe and the catheter. These valves may contain structure for delivering fluid from a storage compartment in the valve to the catheter, and are referred to in the art as positive displacement valves. Such a valve is taught in U.S. Pat. No. 6,206,861B1. Positive displacement valves were developed to overcome the reflux caused by the disconnection of a syringe tip or cannula from a port or valve. Unfortunately, the positive displacement valves were not designed to compensate for the worst-case syringe stopper induced reflux. When using a traditional syringe assembly containing an elastomeric stopper, the stopper is often compressed when it contacts the distal end of the syringe barrel at the completion of the flush procedure. If the user releases the pressure on the plunger after the flush solutions is delivered, the compressed stopper may expand back to its normal size drawing fluid back into the catheter. This fluid is referred to as syringe stopper induced reflux. Traditional syringe assemblies were designed to accurately deliver medications. Traditional syringe assemblies supplied by various suppliers may appear similar but can vary significantly in terms of performance especially stopper induced reflux. Because the catheter is inserted into the patient the users cannot see the reflux when it occurs and therefore cannot take corrective actions to address a potential problem. [0007] Disconnection induced reflux and syringe stopper induced reflux would not be an issue if all users practice the positive pressure flushing techniques described hereinabove every time they flushed a VAD. However, user experience, environmental circumstance and patient condition vary significantly within the hospital setting and even more when one considers other areas that flush procedures are performed such as clinics and home care. As a result, VAD's are frequently occluded resulting in the need for additional professional time, declotting drugs, removal of catheters and new procedures to place new catheters. All of these interventions come at a cost to the healthcare system and its patients. It is desirable to have syringe assemblies that are designed for flush procedures to enhance best clinical practice. Specifically, syringe assemblies that are configured to automatically minimize or eliminate reflux without depending entirely on user technique. Further, the prior art focuses on syringe assemblies designed to deliver medications and not syringe assemblies that automatically provide additional small amount of flush solution in the I.V. line at the completion of the flush procedure. [0008] Therefore there is a need for a simple, straight forward, automatic, easy-to-manufacture syringe assembly which helps reduce or eliminate reflux of blood into the catheter during and after the flush procedure has occurred even if flush procedures are not precisely followed. For example, prematurely releasing the compressive force on the plunger and/or removing the syringe from the I.V. line before it is clamped, may cause reflux of blood into the catheter, thus increasing the chance of VAD occlusion. SUMMARY OF THE INVENTION [0009] The present invention is directed to a syringe assembly for use in flush applications. The syringe assembly has structure to provide an additional positive displacement of flush solution after the flush solution has been substantially delivered from the cavity in the syringe barrel through the application of an additional distally-directed force to the plunger. [0010] An I.V. flush syringe assembly comprises a barrel including a cylindrical side wall having an inside surface defining a chamber for retaining fluid, an open proximal end, and a distal end including a distal wall with an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber. A plunger including an elongate body portion having a proximal end, a distal end, and a resilient stopper is slidably positioned in fluid-tight engagement with the inside surface of the barrel for drawing fluid into and driving fluid out of the chamber by movement of the stopper relative to the barrel. The elongate body portion extends outwardly from the open proximal end of the barrel. The barrel includes structure for moving fluid distally in the passageway after fluid has been delivered from the chamber and the stopper is in contact with the distal wall. [0011] Structure for positively displacing additional fluid after the stopper has contacted the distal wall of the barrel comprises the stopper including a distal end having a distal surface and a proximal end having a cavity therein defining an inside surface. The distal end of the plunger is connected to the stopper by a complementary detent structure defining a first detent position and a second detent position. The detent structure is configured so that an additional distally-directed force applied to the plunger after fluid has been delivered from the chamber causes the plunger to move distally with respect to the stopper from the first detent position to the second detent position so that a distal tip on the distal end of the plunger contacts the inside surface of the stopper forcing part of the distal end of the stopper toward and preferably into the passageway to move fluid distally in the passageway. [0012] The stopper may include a conically-shaped distal surface and a complementary conically-shaped inside surface of the barrel distal wall wherein the total included angle of the inside surface of the barrel at the distal wall is preferably greater than the total included angle of the stopper distal surface. [0013] The stopper may include a distally-directed projection on the distal end of the stopper shaped to fit in the passageway when the plunger and the stopper are engaged in the second detent position. [0014] The inside surface of the stopper may include a proximally-directed protuberance configured to contact the distal tip of the plunger when the plunger and the stopper are engaged in the second detent position. [0015] The syringe assembly may be configured so that the inside surface of the stopper includes a first discontinuity, and a second discontinuity located distally from the first discontinuity. The distal end of the plunger includes a discontinuity positioned so that when the stopper and the plunger are in the first detent position the plunger discontinuity engages the first discontinuity in the stopper, and when the stopper and the plunger are in the second detent position, the plunger discontinuity engages the second discontinuity in the stopper. The discontinuity on the plunger may be a raised projection and the raised projection may be shaped like an annular ring or flange. The first discontinuity in the stopper may be a recess for containing the discontinuity on the plunger such as an annular recess. The first discontinuity may also be an inwardly directed projection and the plunger discontinuity a recess for accepting the projection. [0016] The syringe assembly may also include flush solution in the chamber and a tip cap releasably connected to the tip of the syringe barrel for sealing the passageway. The flush solution may be selected from the group consisting of saline flush solution and heparin lock solution. [0017] The syringe assembly may further include a needle assembly including a cannula having a proximal end, a distal end, and a lumen therethrough. A hub having an open proximal end containing a cavity and a distal end attached to the proximal end of the cannula so that the lumen is in fluid communication with the cavity of the hub. The needle assembly is removably attached to the tip of the barrel through engagement of the tip to the cavity of the hub so that the lumen is in fluid communication with the chamber of the barrel. [0018] The stopper may be made of material selected from the list consisting of thermoplastic elastomers, natural rubber, synthetic rubber, thermoplastic materials and combinations thereof. [0019] The syringe assembly may further include a spring between the distal tip of the plunger and the distal end of the plunger. The spring is configured to compress when the plunger moves to the second detent position with respect to the stopper. [0020] The syringe assembly may also include the barrel and plunger having complementary detent structures defining a primary detent position and a secondary detent position to hold the position of the plunger relative to the barrel. The primary detent position being positioned to engage when fluid has been delivered from the chamber and the stopper is in contact with the distal wall. The secondary detent position is configured to engage upon application of an additional distally directed force to the plunger after the stopper has made contact with the distal wall. The complementary detent structure between the barrel and the plunger can include the barrel having a first discontinuity and a second discontinuity located distally from the first discontinuity, and a proximal end of the plunger including a discontinuity positioned so that when the plunger and the barrel are in the primary detent position the plunger discontinuity engages the first barrel discontinuity and when the plunger and the barrel are in the secondary detent position the proximal plunger discontinuity engages the secondary barrel discontinuity. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading... Full patent description for Positive displacement flush syringe Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Positive displacement flush syringe patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. 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