Abstract:
An improved arterial syringe safety vent is dually optimized for needle safety and arterial blood degassing efficiency. The safety vent of the invention includes a housing, a needle lock to capture a needle, and a venting portion comprising a hydrophilic filter. The needle lock of the invention is adapted to lock a needle tip between a membrane and a venting potion to prevent accidental needle stick. In en exemplary embodiment the safety vent of the invention engages a needle capture device in a manner that allows movement of the housing in relation to the needle capture device so that the tip of a needle captured by the needle capture device can be locked in a position that prevents exposure of the needle tip. The safety vent of the invention is self-supporting to permit single-handed operation.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. patent application Ser. No. 11/226,888, filed on Sep. 13, 2005, for an “Arterial Syringe Safety Vent”. 

   FEDERALLY SPONSORED RESEARCH 
   Not Applicable 
   SEQUENCE LISTING OR PROGRAM 
   Not Applicable 
   BACKGROUND—FIELD OF THE INVENTION  
   The present invention relates to the sample collection and preparation of arterial blood for subsequent blood gas analysis, specifically to a more efficient and safer blood degassing procedure for the arterial blood sample prior to analysis. 
   BACKGROUND—DISCUSSION OF PRIOR ART  
   Arterial blood samples are used to determine the amount of blood gas (oxygen and carbon dioxide) or variables that depend upon the blood gas levels in a patient&#39;s blood. Typically, a blood sample is collected from a patient via an arterial syringe. During the course of a routine sample collection, the arterial syringe&#39;s needle is inserted into a patient&#39;s artery. Once the needle is inserted, the design of the arterial syringe allows for a patient&#39;s blood to flow into the syringe. This filling process usually occurs until the blood reaches the syringe&#39;s stopple or plunger. Once filled, the syringe&#39;s needle is removed from the patient&#39;s artery. 
   With the patient&#39;s blood sample now located in the syringe&#39;s barrel, it becomes very important to expel any entrapped air bubbles that might have been captured and/or created during the sample collection process. The air bubbles can typically be located at various locations in the syringe (at or near the syringe&#39;s stopple, needle, or needle hub). Nonetheless, it is highly desirable to purge the arterial blood sample of these external air bubbles in an effort to maintain the sample&#39;s integrity. 
   U.S. Pat. No. 5,554,127 to Crouther et al disclose a device and method for degassing a drawn blood sample. The &#39;127 patent describes a device composed of a thimble shaped rigid plastic cap further containing a hydrophilic porous plastic core positioned on the thimble&#39;s interior. There are several disadvantages of this system. In practice, a user of this device is required to pierce the hydrophilic porous plastic core with the syringe&#39;s needle in order to initiate the degassing procedure. If the needle&#39;s gage is large, this requirement can be difficult to perform. Additionally, because the core used in the thimble cap is a porous plastic, the core can shed plastic particles that can subsequently get lodged into syringe&#39;s needle. This porous plastic particulate can potentially damage subsequent analytical equipment or could lead to unpredictable discharge flow rates from a syringe&#39;s partially clogged needle. 
   The &#39;127 patent further teaches that the syringe, thimble cap, and blood sample should be inverted (needle pointing upward) at the start of the degassing process. In this arrangement, the primary venting material, i.e., the hydrophilic porous plastic core is located at a point lower than the tip of the syringe&#39;s needle tip. As the needle&#39;s plunger is pressed, blood will immediately flow down towards the hydrophilic porous plastic core and will subsequently wick into the hydrophilic porous plastic core. Once the core&#39;s pores are filled with fluid, fluid/gas from the syringe will no longer pass into the thimble cap. In short, this required syringe orientation will dramatically limit the amount of fluid/gas that can be purged from the syringe and will likely not provide adequate degassing of the drawn blood sample. 
   The use of this device also introduces healthcare providers to additional blood exposure risks. Following the degassing process with the thimble cap, the &#39;127 patent teaches that healthcare providers are required to remove the needle/needle hub and thimble cap from the syringe. Then, the &#39;127 patent instructs the healthcare provider to cover the open end of the syringe with an auxiliary syringe cap to prevent the sample&#39;s exposure to air. Following the removal of the thimble cap and prior to the assembly of the auxiliary syringe cap, healthcare providers can be exposed to the blood located in the syringe, which presents obvious safety hazards. 
   Similarly, the procedure of removing the needle/needle hub and thimble cap from the arterial syringe and subsequently capping the arterial syringe is a two handed operation. Healthcare workers would benefit from an arterial blood degassing procedure that only requires one hand. If this option were available, the healthcare worker could use one hand to degas the arterial blood sample while using the second hand to assist with the patient&#39;s bandage at the needle&#39;s entry/exit point. 
   U.S. Pat. No. 5,125,415 to Bell discloses a popular device manufactured by Smith&#39;s Medical (Keene, N.H.). The &#39;415 patent describes a syringe tip cap that is designed to fit onto the end of syringe following the sample collection routine. The main advantage of the &#39;415 patent over the &#39;127 patent involves the location of the hydrophilic vent material in the syringe tip cap. With the needle and tip cap positioned above the syringe&#39;s plunger, degassing of the arterial blood sample can occur without premature wetting of the tip cap&#39;s hydrophilic vent. As a result, a more complete degassing process is available with this design. However, the &#39;415 patent like the &#39;127 patent requires that the syringe&#39;s needle/needle hub assembly be removed prior to assembly of the tip cap onto the syringe. Therefore, like the &#39;415 patent, the &#39;127 patent allows for a time when blood is located in a non-capped syringe that can expose healthcare providers to potential risks. Further, the &#39;415 patent falls short of providing the healthcare worker with a single-handed fluid degassing solution. Lastly, the &#39;415 patent does not make any provisions for needle safety. 
   U.S. Pat. No. 4,982,842 to Hollister discloses a needle safety device also manufactured by Smith&#39;s Medical that is routinely sold in conjunction with the device described by the &#39;415 patent The market presence of this device suggests its effectiveness as an efficient means to offer needle safety to healthcare workers, however, the device fails to integrate blood sample degassing functionality. Instead, users of the device regularly use the degassing device described in the &#39;415 patent to purge gas from the blood sample. 
   U.S. Pat. No. 6,491,667 to Keane et all again disclose syringe tip caps for use with arterial syringes. However, like the previously discussed prior art, this patent also requires that the syringe&#39;s needle be removed prior to assembly of the tip cap. Therefore, this design also fails to provide needle safety and fluid degassing functionality in a singular device. 
   OBJECTS AND ADVANTAGES 
   Accordingly, several objects and advantages of my invention are to provide an improved arterial syringe degassing method and device that:
     a. can be performed with only one hand;   b. incorporates needle safety functionality,   c. allows for efficient degassing of an arterial blood, and   d. offers the user with tactile and visual feedback with regards to degassing operation.
 
Still, further objects and advantages will become apparent from a consideration of the ensuing description and drawings.
   

   SUMMARY 
   In accordance with the present invention, an arterial syringe safety vent is presented which is dually optimized for needle safety and blood degassing efficiency that can be operated with a single hand. 

   
     DRAWINGS 
     Drawing Figures 
     The arterial syringe safety vent will be best understood by reference to the following drawings in which: 
       FIG. 1  is an exploded view of an exemplary embodiment of an arterial syringe safety vent shown with an arterial syringe; 
       FIG. 2  is a cross sectional view of the prior art arterial syringe of  FIG. 1 ; 
       FIG. 3  is a cross sectional view of the arterial syringe safety vent of  FIG. 1 ; 
       FIG. 4  is a cross sectional view of an arterial syringe safety vent shown with the arterial syringe of  FIG. 2 ; 
       FIG. 5  is an exploded view of a further exemplary embodiment of an arterial syringe safety vent shown with the arterial syringe of  FIG. 2 ; 
       FIG. 6  is a cross-sectional view of the exemplary embodiment shown in  FIG. 5 ; 
       FIG. 7  shows a an exemplary embodiment of an arterial syringe safety vent. 
       FIG. 8  depicts an embodiment of an arterial syringe apparatus of the present invention with a captured needle; 
       FIG. 9  shows an exemplary embodiment of the present invention; 
       FIG. 10  shows a cross-sectional view of the embodiment shown in  FIG. 9 ; and 
       FIG. 11  shows a cross-sectional view of an exemplary embodiment of the invention engaging a needle capture device. 
   

   REFERENCE NUMERALS IN DRAWINGS 
     10  Arterial syringe 
     11  Syringe plunger 
     12  Syringe barrel 
     13  Needle 
     14  Needle hub 
     15  Needle hub flutes 
     20  Arterial syringe safety vent 
     20   a  Arterial syringe safety vent (alternative embodiment) 
     20   b  Arterial syringe safety vent (second alternative embodiment) 
     21  Legs 
     22  Needle opening 
     23  Filter opening 
     24  Capture flutes 
     25  Filter 
     26  Gripping ring(s) 
     27  Penetrable membrane 
     28  Air Gap 
     40  Universal arterial syringe safety vent 
     41  Needle capturing clamshell 
     42  Locking joint 
     43  Leaf spring 
     44  Positioning Barb 
     45  Catch 
     51  Rails 
     52  Needle capture system 
     53  Hinge 
     54  Positioning catch 
   DETAILED DESCRIPTION 
   Description—FIG.  1 - 4 , Preferred Embodiment 
     FIG. 1  illustrates in exploded view arterial syringe  10  and arterial syringe safety vent  20 . Arterial syringe  10  shown in  FIG. 2  is of standard tubular design fitted with a plunger  11  slidably received therein so that the inside walls of the tube and the outer edge of plunger  11  produce a tight fit with the inner walls of syringe barrel  12 . A needle assembly composed of needle  13  and needle hub  14  are attached to syringe&#39;s barrel  12  by means of a traditional slip lure lock (shown) or male-female lure lock (not shown). Extending away from the axis of needle hub  14  are four needle hub flutes  15  located in equal spacing around the perimeter of hub  14 . The size, length, and profile of needle  13 , needle hub  14 , and hub flutes  15  are typical of those supplied by hypodermic needle manufacturers such as Kendall (a division of Tyco International, Princeton, N.J.), Terumo Medical Corporation (Somerset, N.J.), and Becton Dickinson (Franklin Lakes, N.J.). 
   Arterial syringe safety vent  20  shown in  FIG. 3  is preferably made from a clear injection moldable material such as styrene-butadiene-copolymer, available from Chevron Phillips Chemical (The Woodlands, Texas), and composes legs  21  that enable the base to rest on a horizontal surface. Located on opposing ends of arterial syringe safety vent  20  are needle opening  22  and filter opening  23 . Capture flutes  24  are located in equal spacing around the perimeter of needle opening  22 . The size, shape, and taper of these capture flutes  24  are sized to create an interference fit with arterial syringe flutes  15 ,  FIG. 1 . 
   Filter opening  23  is sized to receive filter  25 . Preferably, the inner diameter of the filter opening  23  is approximately 0.010″ less than the outside diameter of filter  25  to facilitate a press fit. Alternatively, one or multiple gripping ring(s)  26  can be added to further secure filter  25  in place. 
   Filter  25  is preferably made from a blend of any sinterable thermoplastic material (such as polyethylene) and a cellulose additive and comprises a nominal pore size less than 75 microns. Filter  25  is available from various porous plastic manufacturers such as Porex (Fairburn, Ga.), Micropore Plastics (Stone Mountain, Ga.), MA Industries (Peachtree City, Ga.). 
   Located between needle opening  22  and filter opening  23 , arterial syringe safety vent  20  further incorporates penetrable membrane  27  and air gap  28  of sufficient volume to facilitate arterial blood collection during the degassing operation. 
     FIG. 4  is a cross sectional view of  FIG. 1  that shows arterial syringe  10  captured and locked into arterial syringe safety vent  20 . 
   Description—FIG.  5 - 6 , First Alternative Embodiment 
   Illustrated as a first alternative embodiment of this invention,  FIG. 5  and  FIG. 6  show arterial syringe  10  with an universal arterial syringe safety vent  40  in exploded and cross section view respectively. Universal arterial syringe safety vent  40  is composed of an arterial syringe safety vent  20   a  and a needle-locking clamshell  41  positioned around the perimeter of needle opening  22 . Needle locking clamshell  41  is composed of two symmetrical halves fitted to one another by a locking joint  42  and further comprises leaf spring  43 , positioning barb  44  and catch  45 . 
   Description—FIG.  7 - 11 , Second Alternative Embodiment 
   Illustrated as a second alternative embodiment of this invention, 
     FIG. 7-11  describe an arterial syringe safety vent  20   b  working in conjunction with a needle safety system such as the one manufactured by Smith&#39;s Medical (Keene, N.H.) described by U.S. Pat. No. 4,982,842. In this arrangement, arterial syringe safety vent  20   b  embodies the basic features of the previously described preferred embodiment, i.e., filter  25 , penetrable membrane  27 , air gap  28 . However, this embodiment does not incorporate any needle capture functionality into the arterial syringe safety vent  20   b . Instead, this embodiment adds blood sample degassing functionality to the needle capture system described in the &#39;842 patent via rails  51  which facilitates movement of arterial syringe safety vent  20   b  in an axial direction relative to needle  13  and needle capture system  52 . 
   Operation—FIGS.  1 - 4   
   A blood gas sample is first drawn from a patient and collected into arterial syringe  10 . Using one hand, the healthcare worker can insert arterial syringe&#39;s needle  13  into needle opening  22  of arterial syringe safety vent  20 . As needle  13  travels down arterial syringe safety vent  20 , needle hub  14  will come into contact with capture flutes  24  and the tip of needle  13  will come into contact with penetrable membrane  27 . As arterial syringe  10  is further depressed into arterial syringe safety vent  20 , needle  13  will pierce and travel through penetrable membrane  27 . Penetrable membrane  27  will subsequently create a seal around the outside diameter of needle  13 . Shortly thereafter and as arterial syringe  10  is further depressed into arterial syringe safety vent  20 , an interference fit occurring between needle hub flutes  15  and capture flutes  24  will lock arterial syringe  10  to arterial syringe safety vent  20 . 
   Once secure in place, the healthcare worker positions arterial syringe  10  and arterial syringe safety vent  20  upright so that arterial syringe safety vent  20  is above arterial syringe  10  to gather air bubbles close to needle hub  14 . Syringe plunger  11  can then be depressed to force the blood sample into air gap  28 . As blood flows into air gap  28 , the gas present in the arterial blood sample will vent through filter  25  while the blood begins to accumulate on penetrable membrane  27 . As syringe plunger  11  is further depressed, the blood sample will fill air gap  28  towards filter  25 . Eventually, as more blood is expelled from arterial syringe  10 , the blood will fully occupy air gap  28  and come into contact with filter  25 . Once the blood is in contact with filter  25 , the pores of filter  25  will fill with fluid due to its hydrophilic properties (created by the cellulose additive). As the blood and the cellulose contained within filter  25  mix, the viscosity of the blood will increase thereby prohibiting additional fluid flow through filter  25 . Once this occurs, air and fluid will cease to flow through filter  25  and the external air previously entrapped within the arterial blood sample will be purged. 
   Operation, First Alternative Embodiment—FIGS.  5 - 6   
   As was previously described, a blood gas sample is first drawn from a patient and collected into arterial syringe  10 . Using one hand, the healthcare worker can insert needle  13  of arterial syringe  10  into needle opening  22  of universal arterial syringe safety vent  40 . As needle  13  travels down arterial syringe safety vent  20   a,  needle hub  14  will come into contact with inner diameter of needle locking clamshell  41 . 
   As needle hub  14  travels farther down needle opening  22 , leaf springs  43  will allow the inner diameter of needle locking clamshell  41  to increase and catch  45  will be in contact with needle hub  14 . Once needle hub  14  passes catch  45 , the tension in leaf springs  43  will cause catch  45  to move towards its center, thus reducing the inner diameter of needle locking clamshell  41  to a distance less than the diameter of needle hub  14 . In this position, needle locking clamshell  41  will effectively prevent removal of needle  13  and needle hub  14  from universal arterial syringe safety vent  40 . 
   The remaining blood degassing operation associated with this alternative embodiment is identical to the previous described embodiment, i.e., the needle penetrates penetrable membrane, the needle is inverted, and the gas expelled from the collected blood sample. 
   Operation, Second Alternative Embodiment—FIGS.  7 - 11   
   As was previously described, a blood gas sample is first drawn from a patient and collected into arterial syringe  10 . Needle capture system  52  and arterial syringe safety vent  20   b  is then rotated about hinge  53  to capture needle as described by U.S. Pat. No. 4,982,842 (shown in  FIG. 8 ).  FIG. 9  shows the same needle capture orientation without arterial syringe  10  and  FIG. 10  shows a cross section of  FIG. 9 . Once needle  13  is captured by needle capture system  52 , arterial syringe safety vent  20   b  is slid towards needle  13  along rails  51 . As the needle travels towards arterial syringe safety vent  20   b , needle  13  will pierce penetrable membrane  27 . Once pierced, the syringe safety vent  20   b  is further depressed until positioning catch  54  is engaged to secure arterial syringe safety vent  20   b  into final position relative to needle capture system  52 . From this point, the remaining blood degassing operation associated with this second alternative embodiment is identical to the previous described embodiments. 
   CONCLUSION, RAMIFICATIONS, AND SCOPE  
   Thus the reader will see that the arterial syringe safety vent of the invention provides a highly efficient and safe degassing device that facilitates single-handed operation. 
   While my above description contains many specificities, these should not be construed as limitations, but rather as an exemplification of three embodiments thereof. Many other variations are possible that can be built upon the previously discussed arterial syringe safety vent featuring a penetrable membrane, air gap, and filter arrangement. For example, a custom syringe could be manufactured that improves needle capture efficiency. Such a custom syringe might incorporate one or multiple undercuts or bosses specially designed to lock onto a modified arterial syringe safety vent housing. Similarly, the undercut(s) or boss(es) of the custom syringe could be designed to facilitate a male-female thread arrangement to the arterial syringe safety vent. 
   Another variation to the basic design of this invention might feature a safety vent comprised of two different materials. For example, the vent&#39;s base could be molded from a standard polyethylene or polypropylene material while the penetrable membrane was molded from a thermoplastic elastomer, such as Santoprene (available from Advanced Elastomer System, LP, Akron, Ohio), to create a more pliable seal around the syringe&#39;s needle. 
   In yet another variation, manufacturing capabilities might dictate the arterial syringe safety vent production as an assembly from two separately manufactured components, i.e., the penetrable membrane might be independently molded and later affixed into the arterial syringe safety vent&#39;s base by means of traditional ultrasonic, mechanical entrapment, or adhesive/chemical bonding arrangement. 
   In short, there are numerous needle capture, material, and manufacturing variations that can be built off the basic platform of the current invention; accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.