Abstract:
The present invention is a syringe tip cap comprising a bottom portion, a top portion, an annular skirt extending therebetween and a plug that projects proximally from the bottom portion so as to be telescoped into the passage of a syringe tip. The plug provides means to allow air to be vented from the syringe with contacting the user. The syringe tip cap of the present invention also provides the user with an indication by tactile and visual feedback that the syringe has been vented.

Description:
This application claims priority from provisional application No. 60/151,877, filed Aug. 31, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a syringe tip cap for use in blood collection and transport procedures and more particularly to a syringe tip cap for use with an arterial blood-sampling syringe or whole blood collection syringe. 
     2. Description of Related Art 
     Arterial blood samples are commonly obtained from a patient by using an arterial blood gas syringe or a whole blood collection syringe for arterial blood gas or other analytical analysis. 
     In the field of arterial blood gas syringes, it is important to prevent exposure of a collected blood sample to the atmosphere and to allow for the removal of trapped gases from the syringe once sampling is effected. 
     Conventional arterial blood gas syringes include a syringe barrel, a syringe tip, a luer connection, a standard needle and a plunger rod with a piston member on the distal end thereof. 
     When the syringe is being used to draw a blood sample, the needle is conventionally removed after draw and the syringe tip covered by a cap to isolate the sample during storage and/or transportation. Various tip cap structures have been disclosed having features designed to protect both the sample and the technician during capping, transportation and storage. Venting of these prior art structures is performed by inverting the syringe (tip up), removing the cap and visualizing advancement of the blood sample through the tip consequent to pressure applied to the plunger in order to remove any air left in the syringe tip and then transport the sample to the site of analysis. 
     While recent advances have contributed to improved technician safety during venting, further improvements are needed, particularly for syringe assemblies intended for arterial blood gas analysis, where residual gas left in a syringe after sampling may interfere with the analysis as well as to protect the user from exposure to the blood sample. 
     SUMMARY OF THE INVENTION 
     The present invention is a tip cap for use with an arterial blood gas syringe or whole blood collection syringe. Desirably, the syringe comprises a barrel, a syringe tip, a luer connection, a needle and a plunger rod with a piston member on the distal end of the plunger rod. In instances where the syringe is used to draw a sample by an arterial line, then the needle is not included. 
     Preferably, the syringe may also include a suitable additive such as an anticoagulant. 
     The syringe tip is preferably a slightly tapered conical tip projecting from the distal end of the syringe barrel. A passage extends through the syringe tip and communicates with the syringe barrel. The luer connection projects from the distal end of the syringe barrel and coaxially surrounds the syringe tip. 
     The tip cap preferably comprises a bottom portion, a top portion, and an annular skirt extending from the top portion to the bottom portion having an inner surface and an outer surface. The bottom portion comprises an inner and an outer end wall. The top portion comprises a rim. The annular skirt defines a diameter greater than the outside diameter of the syringe barrel. The outer surface of the annular skirt may include ribs such as protrusions or flats to enhance handling and gripping of the tip cap by the user. 
     The cap further includes an inner plug that projects proximally from the bottom portion inner end wall and is dimensioned to be telescoped into the passage of the syringe tip of the syringe barrel. The plug provides means to allow air to be vented from the syringe with depression of the syringe plunger. In addition, the plug provides tactile means to the user to indicate that the syringe has been vented. 
     The tip cap further comprises an intermediate wall projecting proximally from the inner end wall of the bottom portion of the tip cap and is in spaced surrounding relationship to the plug. 
     Preferably, the intermediate wall comprises an outer surface that is substantially cylindrical and an inner surface that is defined by six intersecting planar surfaces whereby the inner surface of the intermediate wall is substantially a hexagonal cross-section. 
     Preferably, the hexagonal cross-sectional of the inner surface of the intermediate wall provides a frictional fit with the conically tapered tip of the syringe. In addition, the outer surface of the intermediate wall preferably comprises vertical interference strips that assist the user in locating the cap onto the syringe, and more particularly whereby the strips engage with the luer connection on the syringe. The strips are of varying lengths to provide tactile feel to the user whereby the increasing resistance between the strips and the luer connection indicates to the user that the tip cap is at various positions. Preferably, the strips are vertical and of varying lengths to identify the venting position. The first position is the venting position and the second position is the secured position or final position whereby the tip cap and the syringe are removably secured. 
     Additionally, the tip cap further comprises a generally cylindrical internal sealing ring extending from the inner surface of the annular skirt and the inner end wall of the bottom portion. The internal ring further comprises an inner wall surface and outer wall surface. Most preferably, the internal sealing ring is separated from the outer surface of the intermediate wall by a first annular space. In addition, there is a second annular space between the inner surface of the annular skirt and the inner wall surface of the internal sealing ring. 
     The inner wall surface of the internal sealing ring further comprises indentations or grooves. The indentations provide the means to relieve pressure that may be caused when the syringe tip is pushed into the tip cap. In addition, the indentations may substantially reduce blood leakage from the syringe when the capped syringe is stored in ice water. 
     In use, the user draws a blood sample from a patient into an arterial blood gas syringe via a needle or intravenous line. Then either the needle is removed from the syringe and placed in a sharps container or the syringe is removed from the IV line. Then the user urges the tip cap over the distal end of the syringe barrel, with a slight twisting motion, whereby the luer connection will cooperate with the strips of the intermediate wall whereby the cap will progressively screw onto the syringe via the cooperation between the luer connection the strips and the plug telescopes into the conical passage of the tip of the syringe barrel. Alternatively, the cap may also be pushed onto the syringe. 
     The strips provide two stopping points for connecting the tip cap and the syringe. The first stopping point occurs when the user feels the tactile stopping point of the strips. At this first point, a venting position has been reached whereby the user points the syringe tip with the cap upwardly and lightly tapping the syringe barrel to move air bubbles to the distal end of the syringe barrel. The user then gently depresses the plunger so that air bubbles contained within the blood sample will be expelled via the venting mechanism of the plug. When all of the trapped air is removed from the blood sample, a resistance to further depress the plunger will be experienced by the user due to the design of the plug. 
     The second stopping point occurs when the planar interior surface of the intermediate wall gradually is urged into tight engagement with the outer surface of the conically tapered tip as the tip cap is telescoped onto the syringe barrel. Thus, the plug achieves a sealing of the passage through the tip while the intermediate wall achieves a frictional retention. 
     Preferably, the cap engages onto at least two of the four thread strips. Thereafter, the cap engages with two more threads, positioned slightly further down. The increase from two to four threads indicates to the user an increase in resistance to turn and therefore indicating the venting position. 
     The cap and syringe may be separated in a reverse twist off manner by applying a rotational force to the cap. Most preferably, an upward rotational force is applied to the cap and a downwardly force applied to the syringe along the longitudinal axis. 
     An advantage of the tip cap of the present invention is that it provides the user with tactile feedback when venting of air from the blood sample in the syringe is substantially complete as well as to visually alert the user that venting is complete. 
     Still another advantage of the tip cap of the present invention is that there is visual tactile feedback to the user whereby the user can view the syringe tip in the tip cap. 
     Another advantage of the tip cap of the present invention is that the outer surface of the tip cap contains features to enhance handling and grip for the user. 
     A notable advantage of the tip cap of the present invention is that the internal ring surrounds the luer connection of the syringe, assists in preventing any residual blood sample in the syringe luer connection from leaking out of the tip cap and luer connection, most notably during storage in ice water. 
     Another advantage of the present invention is that inclusions of water in the tip cap escape through channels. 
     A further advantage of the present invention is that the tip cap has a LED light transmission feature due to the structure and materials of construction. 
     Advantages of the tip cap of the present invention further include the attributes of the intermediate wall and the plug: (i) the strips lock the tip cap into place and substantially prevent the tip cap from being inadvertently removed from the syringe tip; (ii) the strips lock the tip cap into place with the luer connection and prevent the tip cap from being removed laterally from the syringe; (iii) the strips allow ease of use whereby the tip cap is easily screwed or urged into place with the syringe; (iv) the strips and the plug allow the tip cap to be partially seated with the syringe so that the sample in the syringe can be vented; (v) the strips and the plug provide the tip cap to be removable locked with the syringe to prevent accidental detachment of the tip cap and the syringe; (vi) the plug provides the means to vent air from the sample in the syringe without contacting the user; and (vii) the plug allows the syringe to be sealed from the atmosphere. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the tip cap of the present invention. 
         FIG. 2  is an enlarged cross sectional view of the cap of FIG.  1 . taken along line  2 — 2  thereof. 
         FIG. 3  is a perspective view of a syringe without the needle. 
         FIG. 4  is a perspective view of the syringe of  FIG. 1  connected to the tip cap of FIG.  2 . 
         FIG. 5  is an enlarged elevational view, partially in section of the syringe and tip cap of  FIG. 4 , taken along line  5 — 5  thereof. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to the drawings in which like reference characters refer to like parts throughout the several views thereof,  FIGS. 1 and 2  illustrate a tip cap  20  of the present invention. 
     Cap  20  as shown in  FIGS. 1 and 2 , has a closed bottom portion  22  having an outer end wall  24  and an inner end wall  26 , a top open end  28  having a rim  29  and an annular outer skirt  30  extending from the closed bottom surface to the top open end. Annular skirt  30  includes an inner wall surface  32 , an outer wall surface  34  and ribs, flats and/or protrusions  54  on the outer wall surface. 
     As shown in  FIG. 2 , tip cap  20  further includes a plug  40  that projects proximally from inner end wall  26  of closed bottom portion  22 . Plug  40  is dimensioned to be telescoped into the passage of the syringe tip of a syringe barrel. Plug  40  includes a top end  42 , a first end  44 , a sidewall  46  extending between top end  42  and first end  44 , a bottom end  48 , a tapered sidewall  50  extending from first end  44  to bottom end  48  and a flat surface  52  extending vertically along sidewall  46 . 
     As further shown in  FIG. 2 , a primary internal ring  60  projects proximally from inner end wall  26  and is in spaced surrounding relationship with plug  40 . Primary internal ring  60  includes an outer surface  62 , an inner surface  64 , a bottom section  56 , a top section  57 , a sidewall  58  extending between bottom section  56  and top section  57 . Outer surface  62  of primary internal ring  60  is substantially cylindrical and inner surface  64  is defined by a partial planar surface  66  that includes a plurality of planar surfaces  67  that form a substantially hexagonal cross-section. 
     Outer surface  62  of primary internal ring  60  further includes a plurality of vertical interference strips  68  of varying lengths, whereby interference strips  63  extend proximally from top section  57  downwardly on outer surface  62  and interference strips  65  extend proximally from bottom section  56  partially upwardly on outer surface  62  at a distance below strips  63 . 
     As further shown in  FIG. 2 , a secondary internal ring  70  extends from inner wall surface  32  of annular skirt  30  and from inner end wall  26  of closed bottom portion  22 . Secondary internal ring  70  is separated from outer surface  62  of primary internal ring  60  by a first annular space  72 . Secondary internal ring  70  includes a top section  75 , a bottom section  76  and a sidewall  74  extending from the top section to the bottom section. Sidewall  74  includes outer surface  80 , inner surface  82  and indentations  84  on inner surface  82 . Section compartments  88  are located between outer surface  80  and inner wall surface  32  of annular skirt  30 , whereby the compartments are sectioned by sidewalls  86 . Sidewalls  86  allow adequate molding conditions. 
     As shown in  FIG. 3 , syringe  100  includes a barrel  102  with a distal end  103 , a syringe tip  104  and a luer connection  106  located at the distal end of the barrel with an annular space  107  between the syringe tip and the luer connection, a plunger rod  108  with a distal end  110  and a piston member  112  on the distal end of the plunger rod and a passageway  114  that extends through the syringe tip and into the barrel. Syringe tip  104  may be a slightly tapered conical tip. 
     Once a fluid sample is contained in syringe  100 , tip cap  20  is removably secured to syringe  100 . The tip cap is screwed onto the luer connection of the syringe whereby the luer connection progressively moves in communication with strips  63 , plug  40  moves into communication with the conical tip of the syringe and the luer connection fits into first annular space  72 . The movement of the tip cap stops at a first stopping point where the top strips terminate and before the bottom strips begin and at first end  44  of the plug. This first stopping point is easily felt by the user and indicates to the user that a venting position has been reached and that before the cap is removably secured to the syringe, the user should try and remove excess air bubbles from the fluid sample. 
     At this first stopping position, the user points the syringe tip with the tip cap upwardly whereby the user gently taps the barrel of the syringe to move air bubbles from the fluid sample to the tip of the syringe. The user then gently depresses the plunger so that air bubbles contained within the sample will be expelled through the tip cap via indents  52  of plug  40 . When substantially all of the trapped air has been expelled, a resistance to further depress the plunger will be felt by the user, which is an indication that the syringe has been vented. 
     Then the user proceeds to continue screwing the cap fully onto the syringe, whereby the luer connection further cooperates with the bottom strips on the primary ring and the planar surfaces provide a friction fit with the conically tapered tip of the syringe, whereby the primary is gradually urged into tight engagement with the outer surface of the conically tapered tip. The plug achieves a scaling of the passageway through the tip, whereby the plug fits snugly in the passageway of the syringe tip and with bottom end  48  of the plug thereby indicating to the user that the tip cap is securely engaged with the syringe. The removably secured arrangement of the tip cap and the syringe is shown in  FIGS. 4 and 5 . 
     As shown in  FIGS. 4 and 5 , flats  54  are positioned on the outer wall surface of annular skirt  30 . The flats substantially prevent the cap from rolling and provide a convenient grasping surface for ready removal and placement of the cap on the syringe. Although a smooth outer circumference without flats is within the purview of the instant invention, a cap with an outer surface with flats is preferred. In addition, outer end wall  24  of cap  20  is flat to allow the syringe when connected to the tip cap to be placed on a flat surface unattended, in an upright position thereby allowing ease of manipulation of the syringe by the user. 
     The tip cap of the invention may be made of a clear molded thermoplastic material so that the syringe tip may be readily viewed in the tip cap. Representative materials include, for example, polyethylene, polypropylene and polyvinyl chloride. Although it is within the purview of the invention to provide caps which are transparent, it is within the purview of this invention to provide caps which are color coded for defining the kind of examination to be conducted on the specimen collected. 
     The syringe may incorporate a hydrophilic material or a silicon may be applied to the internal surface thereof for enhancing the flow of blood introduced into the syringe.