ASPIRATION SYRINGE

Abstract: An aspiration syringe (10) suitable for one-handed operation has a barrel (12) defining a bore (14), a plunger (16) consisting of a small cross-section plunger shaft (18) extending into the bore (14) and a first seal (20) within the bore (14), carried by the distal end of the shaft (18) for axial movement within the bore (14), and an end closure (22) across the bore (14) proximal of the first seal (20), the plunger shaft (18) extending in sliding, sealed engagement therethrough. The first seal (20) engages the wall defining the bore (14) in vacuum-tight sealing engagement. The transverse cross-sectional area of the shaft (18) is much less than the transverse cross-sectional area of the bore (14) to provide a syringe-actuating vacuum chamber (40) of substantial volume within the bore (14) between the seal (20) and the end closure (22). Movement of the plunger shaft (18) to carry the first seal (20) distally, from a first position, away from the end closure (22), creates a vacuum condition within the vacuum chamber (40) sufficient that when the plunger shaft (18) is released, the first seal (20) is propelled by pressure differential acting across the first seal (20), while the distal end of the syringe (10) is exposed to fluid, to automatically move the plunger (16) proximally toward the end closure (22) and cause entry of fluid (44) into the distal portion (46) of the bore (14) distal of the first seal (20). A method of drawing fluid samples is also described.

Description: The invention relates to an aspiration syringe according to the first part of claim 1 . Such a syringe is used for drawing samples, e.g., fluid or tissue, through a needle into the syringe body. WO - A1 - 84 / 02 278 ( KÖZPONTI VALTO) describes such an aspiration syringe. The technical problem of the invention regarding this prior art is to provide an aspiration syringe that creates vacuum for drawing a sample by quick, one-handed manipulation to generate continuous vacuum while allowing the user to have both hands free after onset. The solution to this problem is accomplished by the characterizing part of claim 1 . The remaining claims go further in specifying the invention. A plurality of ways of carrying out the invention is described in detail below with reference to drawings, namely : Fig. 1 is a side view of the aspiration syringe of the invention, as packaged prior to use; Fig. 2 is a perspective view of the aspiration syringe of the invention, with the needle introduced through a patient's skin by a physician and the plunger depressed preparatory to taking a sample; Fig. 3 is a side view of the aspiration syringe during sample taking; and Fig. 4 is an end section view taken at the line 4-4 of Fig. 3. Referring to Fig. 1, an aspiration syringe 10 of the invention consists of a syringe barrel 12 defining a bore 14, a plunger 16 consisting of a small cross-section plunger shaft 18, e.g., a hollow steel cannula, extending into the bore 14 and a first seal member 20 within the bore, and an end closure across bore 14, consisting of a second seal member 22 disposed within the bore proximal of the first seal member 20. The first seal member is carried by the distal end of the shaft 18 for axial movement within the bore. The plunger shaft extends through the second seal member 22 in sliding, sealed engagement. The syringe barrel is a standard syringe encasement, e.g., of 10 cc volume sized and constructed at the distal end for receiving a disposable aspiration needle 24, and defining a small bore for passage of fluids between the needle and the syringe bore 14. The proximal end of the syringe barrel defines an aperture sized for receiving the first and second seal members 20, 22 into the syringe barrel, the seal members being of the double ring type and each adapted to engage the wall 13 of the syringe barrel defining the bore in vacuum-tight, sealing engagement. The second, proximal seal member 22 is attached to a disk 26, sized to engage upon the end surface of the syringe barrel, about the proximal opening, to hold the second seal member fixed in position at the distal end of the syringe bore. The disk 26 also acts as a stiffener to enhance the sealing performance of seal member 28. A similar but smaller diameter disk 27 serves to enhance the sealing performance of first seal member 20. Extending radially outward about the proximal end of the syringe barrel is flange 28. The plunger shaft 18 terminates proximally in thumb tab 30. The syringe 10 is provided generally as shown in Fig. 1, with the first distal seal member 20 disposed closely adjacent to the second, proximal seal member 22, on the plunger shaft 18, and the seals and plunger 16 inserted into the proximal end of the plunger until the disk 26 engages upon the proximal surface of syringe barrel. A disposable needle 24, shown dashed line in Fig. 1, is attached to the distal end of the syringe barrel 12. Referring to Fig. 2, to aspirate a sample, the physician, using only one hand (36), grasps the syringe barrel 12 with adjacent fingers 32, 34 on either side of the barrel and engaging flange 28, and thumb 38 engaged upon the end surface of thumb tab 30. The physician presses thumb tab 30, e.g., with thumb 38, to move the plunger 16 in the distal direction (arrow F, Fig. 1), toward the proximal end of the syringe barrel, movement of the plunger shaft 18 carrying the first seal member 20, which engages the wall 13 defining the vacuum chamber 40 with low friction, distally from its first position (Fig. 1), away from the second seal member 22, to create a vacuum condition within a vacuum chamber 40, e.g., of about 10 cc volume, within the bore 14, between the two seal members, while expelling air (arrow A) from within the bore 14, via the needle 24. After the thumb tab is fully depressed, a stroke, e.g., of at least about 2 inches, the physician injects needle 24 into the body 42 of the patient to a position where a fluid sample is to be taken. The relationship of the outer diameter, D₁, of the plunger shaft 18 to the inner diameter, D₂, e.g., about 0.5 inch, of the bore of the vacuum chamber 40 is selected to provide a ratio of transverse cross-sectional areas of shaft to vacuum chamber bore of the order of 1:20 or less, and preferably 1:50 or less, to provide a substantial syringe-actuating pressure differential between the vacuum chamber 40 and the sample chamber 44, across the first seal member 20. Preferably the differential is of the order of at least about 6,8 kPa (20 inches of mercury). The physician is thus able to release the syringe, freeing both of his hands for other purposes, the vacuum condition (indicated in Fig. 3 by " - ") within the chamber 40 being sufficient that when the plunger 16 is released, the first seal member 20 is propelled proximally (arrow P, Fig. 3) by pressure differential acting across the first seal member 20, to automatically withdraw the plunger proximally, toward the second seal member, returning the first seal member substantially to its first position, and causing entry of a sample 44 from body 42 into the distal sample chamber 46 of syringe bore 14. Vacuum is applied continuously, with the syringe unattended, to draw fluid sample into sample chamber 46 until the first seal member 20 returns at least substantially to its first position adjacent the second seal member 22. The needle 24 of syringe 10 is then withdrawn from the body and, when desired, the sample 44 is easily removed from the chamber 46 by again depressing thumb tab 30 (arrow F). Other embodiments of the invention are within the following claims.

Claims: Aspiration syringe (10) comprising a barrel (12) defining a bore (14), a plunger (16) comprising a plunger shaft (18) having a transverse cross-sectional area being much less than the transverse cross-sectional area of said bore (14), and extending into said bore (14), and a first seal member (20) within said bore (14), carried by the distal end of said shaft (18) for axial movement within said bore (14), and adapted to engage the wall defining said bore (14) in sealing engagement, and an end closure across said bore (14) proximal of said first seal member (20), said shaft (18) extending in sliding engagement therethrough, characterized in that said plunger shaft (18) extends through said end closure in sealed engagement, and said first seal member (20) engages the wall defining said bore (14) in vacuum-tight sealing engagement, thereby to provide a syringe-actuating vacuum chamber (40) of substantial volume within said bore (14) between said first seal member (20) and said end closure, whereby movement of said plunger shaft (18) to carry said first seal member (20) distally, from a first position, away from said end closure, creates a vacuum condition within said vacuum chamber (40) sufficient that when said plunger shaft (18) is released, said first seal member (20) is propelled by pressure differential acting across said first seal member (20), while the distal end of said syringe (10) is exposed to fluid, to automatically move said plunger (16) proximally toward said end closure and cause entry of fluid into the portion of said bore (14) distal of said first seal member (20). Aspiration syringe of claim 1 , characterized in that the transverse cross-sectional area of said shaft (18) is less than 5 % of the transverse cross-sectional area of said bore (14). Aspiration syringe of claim 2 , characterized in that said transverse cross-sectional area is about 2 % less. Aspiration syringe of claim 1 , characterized in that said bore (14) and said plunger (16) are sized to enable stroke of said plunger (16) sufficient to create within said vacuum chamber (40) a vacuum condition of the order of at least 6,8 kPa (20 inch of mercury) . Aspiration syringe of claim 1 , characterized in that said first seal member (20) in said first position is disposed in close proximity to said end closure. Aspiration syringe of claim 1 , characterized in that said first seal member (20) is adapted, upon release, to return to said first position. Aspiration syringe of any preceding claim , characterized in that said end closure comprises a second seal member (22) disposed within said bore (14) and fixed against movement relative to said barrel (12). Aspiration syringe of claim 7 , characterized in that said first seal member (20) and said second seal member (22) are of double sealing ring type. Aspiration syringe of claim 1 , characterized in that said vacuum chamber (40) has a volume of the order of about 10 cm³ . Aspiration syringe of claim 9 , characterized in that said bore (14) has a diameter of the order of about 1,25 cm (0.5 inch), and said plunger (16) has a maximum stroke of at least about 5 cm (2 inch).

Inventors: CLEMENT, THOMAS P.
Applicants: VAN-TEC INCORPORATED
Application year: 1987
Main classification: A61M1
IPC codes: A61B10, A61B5, A61M5