Syringe and methods thereof for reduced maximum aspiration pressure

Abstract

Syringes and methods thereof reduce maximum aspiration pressure. An exemplary syringe can include a barrel, a plunger, and a volume-increasing means for increasing a volume of syringe dead space in the syringe, which, in turn, reduces the maximum aspiration pressure of the syringe. A tipped end portion of the barrel can taper from a barrel diameter of the barrel down to a syringe-tip diameter of a syringe tip that extends from the tipped end portion of the barrel. Such a tapered portion of the barrel can define a conical barrel surface and a corresponding conical barrel volume within the tipped end portion of the barrel. The plunger can be disposed in the barrel through a mouthed end portion of the barrel such that an elastomeric piston fitted over an end portion of a plunger shaft forms a circumferential seal with an inner surface of the barrel.

Description

SYRINGE AND METHODS THEREOFFOR REDUCED MAXIMUM ASPIRATION PRESSUREPRIORITY

[0001] This application claims the benefit of priority to U.S. Provisional Application No. 63 / 571,766, filed March 29, 2024, which is incorporated by reference in its entirety into this application.BACKGROUND

[0002] A higher aspiration pressure reflects a greater pressure differential between the inside of a syringe and its surroundings at atmospheric pressure, which can result in more air leaking into the syringe from the surroundings due to greater vacuum pressure within the syringe. Additionally, the higher aspiration pressure facilitates bubble formation in that the greater vacuum pressure within the syringe facilitates expansion and release of bubbles from the inner surface of the barrel, which bubbles become more apparent to clinicians, thereby causing concern. Indeed, fluid in the syringe such as of saline, which is often used by clinicians for aspiration during catheter placement procedures, or blood, which is witnessed when clinicians lose vascular access after blood flashback but continue to aspirate outside of any vessel, can develop observable bubbles in the syringe due to the higher aspiration pressure causing concern about leakage, air embolism, or pneumothorax.

[0003] Disclosed herein are syringes and methods thereof for reduced maximum aspiration pressure that address the foregoing.SUMMARY

[0004] Disclosed herein is a syringe including, in some embodiments, a barrel, a plunger, and a volume-increasing means for increasing a volume of syringe dead space in the syringe, wherein the volume-increasing means reduces a maximum aspiration pressure of the syringe. The barrel includes a tipped end portion and a mouthed end portion opposite the tipped end portion of the barrel. The tipped end portion of the barrel tapers from a barrel diameter of the barrel down to a syringe-tip diameter of a connecting portion of a syringe tip that extends from the tipped end portion of the barrel. Such a tapered portion of the tipped end portion of the barrel defines a conical barrel surface and a corresponding conical barrel volume within the tipped end portion of the barrel. The plunger is disposed in the barrel by way of a mouth in themouthed end portion of the barrel. The plunger includes an elastomeric piston fitted over an end portion of a plunger shaft that forms a circumferential seal with an inner surface of the barrel.

[0005] In some embodiments, the volume of syringe dead space increased by the volume-increasing means includes a syringe-tip volume within the syringe tip plus any remaining volume of the conical barrel volume that remains in the tipped end portion of the barrel. Such a remaining volume of the conical barrel volume remains in the tipped end portion of the barrel when a piston surface of the elastomeric piston substantially complements the conical barrel surface within the tipped end portion of the barrel. Further, such a remaining volume of the conical barrel volume remains in the tipped end portion of the barrel when the plunger is completely advanced into the barrel in a ready -to-aspirate state of the syringe such that the piston surface of the elastomeric piston mates with the conical barrel surface of the barrel.

[0006] In some embodiments, the volume-increasing means for increasing the volume of syringe dead space includes an increase in the syringe-tip volume. Such an increase in the syringe-tip volume is through an increase in a bore length of a bore of the syringe tip, an increase in a bore diameter of the bore of the syringe tip, or some combination thereof.

[0007] In some embodiments, the volume-increasing means for increasing the volume of syringe dead space includes an increase in the conical barrel volume within the tipped end portion of the barrel. Such an increase in the conical barrel volume is through an increase in a length of the tapered portion of the tipped end portion of the barrel that tapers from the barrel diameter of the barrel down to the syringe-tip diameter, thereby defining an elongated conical barrel volume within the tipped end portion of the barrel.

[0008] In some embodiments, the volume-increasing means for increasing the volume of syringe dead space includes an increase in the remaining volume of any conical barrel volume that remains in the tipped end portion of the barrel when the plunger is completely advanced into the barrel in the ready -to-aspirate state of the syringe.

[0009] In some embodiments, the volume-increasing means for increasing the volume of syringe dead space includes a modification to a shape of the elastomeric piston. Such a modification to the shape of the elastomeric piston increases space between the elastomericpiston and the conical barrel surface within the tipped end portion of the barrel when the plunger is completely advanced into the barrel in the ready -to-aspirate state of the syringe.

[0010] In some embodiments, the modification to the shape of the elastomeric piston includes a recess in the piston surface of a conical elastomeric piston that otherwise mates with the conical barrel surface within the tipped end portion of the barrel. The recess in the piston surface increases space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

[0011] In some embodiments, the modification to the shape of the elastomeric piston includes waffling in the piston surface of a conical elastomeric piston that otherwise mates with the conical barrel surface within the tipped end portion of the barrel. The waffling in the piston surface increases space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

[0012] In some embodiments, the modification to the shape of the elastomeric piston includes a cylindrical elastomeric piston instead of a conical elastomeric piston that mates with the conical barrel surface within the tipped end portion of the barrel. The cylindrical elastomeric piston increases space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

[0013] In some embodiments, the modification to the shape of the elastomeric piston further includes a recess in the piston surface of the cylindrical elastomeric piston. The recess in the piston surface further increases space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

[0014] In some embodiments, the modification to the shape of the elastomeric piston further includes waffling in the piston surface of the cylindrical elastomeric piston. The waffling in the piston surface further increases space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

[0015] In some embodiments, the modification to the shape of the elastomeric piston includes an inverted conical elastomeric piston instead of a conical elastomeric piston that mates with the conical barrel surface within the tipped end portion of the barrel. The inverted conical elastomeric piston increases space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to- aspirate state of the syringe.

[0016] In some embodiments, the modification to the shape of the elastomeric piston includes one or more protrusions extending from the piston surface of the elastomeric piston toward the conical barrel surface within the tipped end portion of the barrel. The one-or-more protrusions of the elastomeric piston prevent the piston surface of the elastomeric piston from mating with the conical barrel surface of the barrel.

[0017] In some embodiments, the volume-increasing means for increasing the volume of syringe dead space includes a hollow elastomeric piston with a slit through the piston surface leading to an otherwise enclosed space within the hollow elastomeric piston.

[0018] In some embodiments, the elastomeric septum and the slit through the piston surface thereof is configured to allow air to pass into the enclosed space within the hollow elastomeric piston at a relatively high aspiration pressure as well as prevent air to pass into the enclosed space within the hollow elastomeric piston at a relatively low aspiration pressure.

[0019] In some embodiments, the volume-increasing means for increasing the volume of syringe dead space includes addition of a cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel. Such a cylindrical barrel volume added to the conical barrel volume defines a cumulative barrel volume within a distal portion of the barrel.

[0020] In some embodiments, the addition of the cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel is through a decrease in a length of the plunger shaft of the plunger.

[0021] In some embodiments, the addition of the cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel is through a porous insert coupled to the piston surface of the elastomeric piston. The porous insert is configured to stopthe plunger from being completely advanced into the barrel in the ready -to-aspirate state of the syringe.

[0022] In some embodiments, the addition of the cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel is through a stop in the plunger shaft of the plunger. The stop in the plunger shaft is configured to stop the plunger from being completely advanced into the barrel in the ready -to-aspirate state of the syringe.

[0023] Also disclosed herein is a method for reducing a maximum aspiration pressure of a syringe. The method includes, in some embodiments, aspirating with the syringe. The syringe includes a barrel, a plunger, and a volume-increasing means for increasing a volume of syringe dead space in the syringe, wherein the volume-increasing means reduces the maximum aspiration pressure of the syringe while aspirating with the syringe. The barrel includes a tipped end portion and a mouthed end portion opposite the tipped end portion of the barrel. The tipped end portion of the barrel tapers from a barrel diameter of the barrel down to a syringe-tip diameter of a connecting portion of a syringe tip that extends from the tipped end portion of the barrel. Such a tapered portion of the tipped end portion of the barrel defines a conical barrel surface and a corresponding conical barrel volume within the tipped end portion of the barrel. The plunger is disposed in the barrel by way of a mouth in the mouthed end portion of the barrel. The plunger includes an elastomeric piston fitted over an end portion of a plunger shaft that forms a circumferential seal with an inner surface of the barrel.

[0024] These and other features of the concepts provided herein will become more apparent to those of skill in the art in view of the accompanying drawings and following description, which describe particular embodiments of such concepts in greater detail.BRIEF DESCRIPTION OF DRAWINGS

[0025] FIG. 1 illustrates a syringe in accordance with some embodiments.

[0026] FIG. 2 illustrates a detailed view of a tipped end portion of the syringe in accordance with some embodiments.

[0027] FIG. 3 illustrates an increase in a volume of syringe dead space through an increase in a bore length of a bore in a syringe tip of the syringe in accordance with some embodiments.

[0028] FIG. 4 illustrates an increase in the volume of syringe dead space through an increase in a bore diameter of the bore in the syringe tip in accordance with some embodiments.

[0029] FIG. 5 illustrates an increase in the volume of syringe dead space through an increase in a length of a tapered portion of a barrel of the syringe in accordance with some embodiments.

[0030] FIG. 6 illustrates an increase in the volume of syringe dead space through a recess in a conical elastomeric piston of a plunger of the syringe in accordance with some embodiments.

[0031] FIG. 7 illustrates an increase in the volume of syringe dead space through an inverted conical elastomeric piston of the plunger in accordance with some embodiments.

[0032] FIG. 8 illustrates an increase in the volume of syringe dead space through a porous insert coupled to the conical elastomeric piston of the plunger in accordance with some embodiments.

[0033] FIG. 9 illustrates an increase in the volume of syringe dead space through a cylindrical elastomeric piston of the plunger in accordance with some embodiments.

[0034] FIG. 10 illustrates an increase in the volume of syringe dead space through a recess in the cylindrical elastomeric piston of the plunger in accordance with some embodiments.

[0035] FIG. 11 illustrates an increase in the volume of syringe dead space through a porous insert coupled to the cylindrical elastomeric piston of the plunger in accordance with some embodiments.

[0036] FIG. 12 illustrates an increase in the volume of syringe dead space through a waffled piston surface of the cylindrical elastomeric piston of the plunger in accordance with some embodiments.

[0037] FIG. 13 illustrates another view of the waffled piston surface of the cylindrical elastomeric piston of the plunger in accordance with some embodiments.

[0038] FIG. 14 illustrates an increase in the volume of syringe dead space through one or more protrusions extending from the piston surface of the conical elastomeric piston of the plunger in accordance with some embodiments.

[0039] FIG. 15 illustrates an increase in the volume of syringe dead space through a hollow conical elastomeric piston of the plunger in accordance with some embodiments.

[0040] FIG. 16 illustrates an increase in the volume of syringe dead space through a decrease in a plunger length of the plunger in accordance with some embodiments.

[0041] FIG. 17 illustrates an increase in the volume of syringe dead space through an effective decrease in the plunger length by way of a stop in a plunger shaft of the plunger in accordance with some embodiments.DESCRIPTION

[0042] Before some particular embodiments are disclosed in greater detail, it should be understood that the particular embodiments disclosed herein do not limit the scope of the concepts provided herein. It should also be understood that a particular embodiment disclosed herein can have features that can be readily separated from the particular embodiment and optionally combined with or substituted for features of any of a number of other embodiments disclosed herein.

[0043] Regarding terms used herein, it should also be understood the terms are for the purpose of describing some particular embodiments, and the terms do not limit the scope of the concepts provided herein. Ordinal numbers (e.g., first, second, third, etc.) are generally used to distinguish or identify different features or steps in a group of features or steps, and do not supply a serial or numerical limitation. For example, “first,” “second,” and “third” features or steps need not necessarily appear in that order, and the particular embodiments including such features or steps need not necessarily be limited to the three features or steps. In addition, any of the foregoing features or steps can, in turn, further include one or more features or steps unless indicated otherwise. Labels such as “left,” “right,” “top,” “bottom,” “front,” “back,” and the like are used for convenience and are not intended to imply, for example, any particular fixed location, orientation, or direction. Instead, such labels are used to reflect, for example, relative location, orientation, or directions. Singular forms of “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise.

[0044] “Proximal” is used to indicate a portion, section, piece, element, or the like of a medical device intended to be near or relatively nearer to a clinician when the medical device is used on a patient. For example, a “proximal portion” or “proximal section” of the medical device includes a portion or section of the medical device intended to be near the clinician when the medical device is used on the patient. Likewise, a “proximal length” of the medical device includes a length of the medical device intended to be near the clinician when the medical device is used on the patient. A “proximal end” of the medical device is an end of the medical device intended to be near the clinician when the medical device is used on the patient. The proximal portion, the proximal section, or the proximal length of the medical device need not include the proximal end of the medical device. Indeed, the proximal portion, the proximal section, or the proximal length of the medical device can be short of the proximal end of the medical device. However, the proximal portion, the proximal section, or the proximal length of the medical device can include the proximal end of the medical device. Should context not suggest the proximal portion, the proximal section, or the proximal length of the medical device includes the proximal end of the medical device, or if it is deemed expedient in the following description, “proximal portion,” “proximal section,” or “proximal length” can be modified to indicate such a portion, section, or length includes an end portion, an end section, or an end length of the medical device for a “proximal end portion,” a “proximal end section,” or a “proximal end length” of the medical device, respectively.

[0045] “Distal” is used to indicate a portion, section, piece, element, or the like of a medical device intended to be near, relatively nearer, or even in a patient when the medical device is used on the patient. For example, a “distal portion” or “distal section” of the medical device includes a portion or section of the medical device intended to be near, relatively nearer, or even in the patient when the medical device is used on the patient. Likewise, a “distal length” of the medical device includes a length of the medical device intended to be near, relatively nearer, or even in the patient when the medical device is used on the patient. A “distal end” of the medical device is an end of the medical device intended to be near, relatively nearer, or even in the patient when the medical device is used on the patient. The distal portion, the distal section, or the distal length of the medical device need not include the distal end of the medical device. Indeed, the distal portion, the distal section, or the distal length of the medical device can be short of the distal end of the medical device. However, the distal portion, the distal section, or the distal length of the medical device can include the distal end of the medical device. Should context not suggest the distal portion, the distal section, or the distal length ofthe medical device includes the distal end of the medical device, or if it is deemed expedient in the following description, “distal portion,” “distal section,” or “distal length” can be modified to indicate such a portion, section, or length includes an end portion, an end section, or an end length of the medical device for a “distal end portion,” a “distal end section,” or a “distal end length” of the medical device, respectively.

[0046] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art.

[0047] As set forth above, a higher aspiration pressure reflects a greater pressure differential between the inside of a syringe and its surroundings at atmospheric pressure, which can result in more air leaking into the syringe from the surroundings due to greater vacuum pressure within the syringe. Additionally, the higher aspiration pressure facilitates bubble formation in that the greater vacuum pressure within the syringe facilitates expansion and release of bubbles from the inner surface of the barrel, which bubbles become more apparent to clinicians, thereby causing concern. Indeed, fluid in the syringe such as of saline, which is often used by clinicians for aspiration during catheter placement procedures, or blood, which is witnessed when clinicians lose vascular access after blood flashback but continue to aspirate outside of any vessel, can develop observable bubbles in the syringe due to the higher aspiration pressure causing concern about leakage, air embolism, or pneumothorax.

[0048] Disclosed herein are syringes and methods thereof for reduced maximum aspiration pressure that address the foregoing.Syringes

[0049] FIGS. 1 and 2 illustrate a syringe 100 in accordance with some embodiments.

[0050] A vacuum -generating device such as the syringe 100 can be modified by way of a volume-increasing means for increasing a volume of dead space in the vacuum-generating device and, thereby, reducing a maximum aspiration pressure of the vacuum-generating device. With the understanding that the syringe 100 is a vehicle to describe such a volume-increasing means, the syringe 100 can be modified by way of the volume-increasing means to increase a volume of syringe dead space in the syringe 100. Such a volume-increasing means likewise reduces a maximum aspiration pressure of the syringe 100.

[0051] The syringe 100 can include a barrel 102, a plunger 104, and the volumeincreasing means for increasing the volume of the syringe dead space in the syringe 100.

[0052] The barrel 102 can include a distal or tipped end portion of the barrel 102, and the barrel 102 can include a proximal or mouthed end portion of the barrel 102 opposite the tipped end portion of the barrel 102. The tipped end portion of the barrel 102 can include a syringe tip 106 extending therefrom, to which syringe tip 106 a needle hub of a needle can be fluidly connected. The mouthed end portion of the barrel 102 can include a barrel flange 108 or barrel collar around a mouth 110 of the barrel 102, through which mouth 110 the plunger 104 is disposed in a barrel chamber 112 of the barrel 102 in at least a ready-to-aspirate state of the syringe 100. Notably, the barrel chamber 112 can be defined by the barrel wall 116 and an extension thereof into the tapered portion 122 of the barrel 102, the barrel chamber 112 extending from the connecting portion 114 of the syringe tip 106 to the mouth 110 of the barrel 102. In addition, the barrel flange 108 or barrel collar can outwardly extend from the mouthed end portion of the barrel 102 for actuating the syringe 100, for example, aspirating the syringe 100, together with the plunger flange or plunger collar 134 of the plunger 104.

[0053] The tipped end portion of the barrel 102 can taper from a barrel diameter of the barrel 102 down to a syringe-tip diameter of a connecting portion 114 of the syringe tip 106. Such a barrel diameter can be an outer barrel diameter coextensive with an outer surface of a barrel wall 116 of the barrel 102, and the syringe-tip diameter can be an outer syringe-tip diameter coextensive with an outer surface of a syringe-tip wall 118 of the syringe tip 106, particularly that of the connecting portion 114 of the syringe tip 106 as the syringe tip 106 can have the taper set forth below. Alternatively, the barrel diameter can be an inner barrel diameter coextensive with an inner surface 119 of the barrel wall 116, and the syringe-tip diameter can be a bore diameter coextensive with an inner surface of a bore 120 through the syringe tip 106, particularly that of the connecting portion 114 of the syringe tip 106 as the bore 120 through the syringe tip 106 need not be a cylindrical bore as set forth below. Notably, such a tapered portion 122 of the tipped end portion of the barrel 102 can define a conical barrel surface 123 within the tipped end portion of the barrel 102, which, in turn, can correspond to a conical barrel volume 124 within the tipped end portion of the barrel 102 having a length, height, or the like coextensive with that of the conical barrel surface 123.

[0054] The syringe tip 106 extending from the tipped end portion of the barrel 102 can be configured to insert into a needle hub of a needle to fluidly connect the needle to the syringe100. Such a needle can be a common or standard needle in which the needle hub has a standard size and taper such as Luer taper (e.g., a 6% taper). Accordingly, the syringe tip 106 can be sized and tapered with the Luer taper for insertion into the needle hub of the foregoing needle or a similar fitting of another medical device. The outer syringe-tip diameter of the syringe-tip wall 118 of the syringe tip 106 can thusly vary from a smaller outer syringe-tip diameter about a distal or syringe-tip opening 126 of the syringe tip 106 to a larger outer syringe-tip diameter about the connecting portion 114 of the syringe tip 106 that connects it to the tipped end portion of the barrel 102. Likewise, the bore diameter of the bore 120 through the syringe tip 106 can vary from a smaller bore diameter about the syringe-tip opening 126 of the syringe tip 106 to a larger bore diameter about the connecting portion 114 of the syringe tip 106 that connects it to the tipped end portion of the barrel 102, thereby providing a conical bore instead of the cylindrical bore set forth above, and, thereby, increasing the volume of the syringe dead space in the syringe 100. Indeed, the syringe tip 106 can vary in accordance with any volumeincreasing means disclosed herein for increasing the volume of the syringe dead space in the syringe 100.

[0055] The syringe 100 can further include a threaded collar 128 extending from the tipped end portion of the barrel 102 around at least a portion of the syringe tip 106. Such a threaded collar 128 can include internal threads configured to screw together with a needlehub flange of a needle hub of a needle. When present, the threaded collar 128 of the syringe 100 advantageously provides a so-called Luer lock-style connection with the needle-hub flange of the needle hub of the foregoing needle for added security against inadvertent disconnection over that provided by an otherwise Luer slip-style connection.

[0056] The plunger 104 can include a plunger shaft 130 and a piston 132 such as an elastomeric piston fitted over a distal end portion, for example, a distal end, of the plunger shaft 130. Thus, the plunger 104 can include a distal or pistoned end portion of the plunger 104. In addition, the plunger 104 can include a proximal, flanged, or collared end portion of the plunger 104 opposite the pistoned end portion of the plunger 104. Notably, the proximal end portion of the plunger 104 can include a plunger flange for the flanged end portion of the plunger 104 or a plunger collar 134 for the collared end portion of the plunger 104. Whether the plunger flange or the plunger collar 134 is present, it can outwardly extend from its corresponding flanged or collared end portion of the plunger 104 for actuating the syringe 100, for example, aspirating the syringe 100, together with the barrel flange 108 or barrel collar of the barrel 102.

[0057] The plunger shaft 130 can be a one-piece plunger shaft including orthogonal struts 136 that meet along their inward facing longitudinal edges at a central axis of the plunger shaft 130. However, the plunger shaft 130 can take other forms, so it should be understood the plunger shaft 130 is not limited to such orthogonal struts 136.

[0058] The piston 132 can include one or more rings configured to respectively form one or more seals, for example, one or more circumferential seals, with the inner surface 119 of the barrel wall 116. The one-or-more rings can include at least a leading ring 138 configured to form a leading seal with the barrel wall 116. The one-or-more rings can also include a trailing ring 140 configured to form a trailing seal with the barrel wall 116. Indeed, when present with the leading ring 138, the trailing ring 140 provides a backup seal with the barrel wall 116. Together, the leading ring 138 and the trailing ring 140 can ensure some seal between the piston 132 and the barrel wall 116 remains intact while the syringe 100 is actuated, for example, aspirated, thereby allowing the syringe 100 to consistently aspirate a liquid such as saline or blood when the plunger 104 is withdrawn from the barrel 102.

[0059] Adverting to the volume-increasing means to increase the volume of syringe dead space in the syringe 100, it should be understood that the volume of syringe dead space increased by the volume-increasing means includes a combination of a syringe-tip volume 142 within the syringe tip 106 and any remaining volume of the conical barrel volume 124 that remains in the tipped end portion of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. The syringe-tip volume 142 within the syringe tip 106 extends from the syringe-tip opening 126 of the syringe tip 106 to the conical barrel volume 124 within the tipped end portion of the barrel 102. The remaining volume of the conical barrel volume 124 remains despite a piston surface 143 of the piston 132 substantially complementing the conical barrel surface 123 within the tipped end portion of the barrel 102 such that the piston surface 143 of the piston 132 mates with the conical barrel surface 123 of the barrel 102 in the ready-to-aspirate state of the syringe 100. Notably, the foregoing volume of syringe dead space is typically minimized in syringes to provide precise dosing of injectable medicines and the like, so increasing the syringe dead space is contrary to that which is typical in syringe designs.

[0060] The increase in volume of the syringe dead space effectuated by the volumeincreasing means need not be large to reduce the maximum aspiration pressure of the syringe 100. Indeed, a relatively small increase in an initial volume of the syringe dead spacesubstantially reduces the maximum aspiration pressure of the syringe 100 as shown by the following equations beginning with Equation 1 for the ideal gas law:PV = nRT, (Equation 1) where P is the pressure of a gas, V is the volume of the gas, n is the number of moles of the gas, R is the ideal or universal gas constant, and T is the temperature of the gas. Assuming the syringe 100 is a closed, leak-free syringe along with a constant temperature, Equation 2 can be derived from the ideal gas law:(Equati on 2) where P is the local atmospheric pressure,is the initial internal volume of the syringe 100 (the plunger 104 is completely advanced into the barrel 102) plus the internal volume of the syringe 100, P2is the pressure inside the syringe 100 upon aspirating syringe 100, and V2is defined by Equation 3 :V2= ki + dV, (Equation 3) where dV is the change in volume due to aspiration of the syringe 100. Aspiration pressure p aspiration is given by Equation 4:Paspiration ^2 Pi (Equation 4)Substituting the righthand side of Equation 3 for V2in Equation 2 gives Equation 5:P- V- = P2(^i + dV (Equation 5)Solving for P2in Equation 5 gives Equation 6: (Equation 6)From the relationship given in Equation 6, P2approaches P1increases for larger values of V1. For smaller values ofvalues of P2are smaller. Since PaSpiration = P2 ~ Pi inaccordance with Equation 4, the scenario in which larger values of result in P2approaching P15the magnitude of Paspiration is minimized. For the scenario in which smaller values ofresult in smaller values of P2, the magnitude of Paspiration is larger. As such, a relatively smallincrease in the initial volume of the syringe dead space substantially reduces the maximum aspiration pressure of the syringe 100.

[0061] In an example, an initial internal system volume of the syringe 100 (e.g., a 5- mL syringe) attached to a medical device can be approximately 0.25 mL when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. Assuming an atmospheric pressure at sea level of 14.7 PSI, an aspiration pressure of -11.8 PSI can be generated when the syringe 100 is aspirated to 1 mL. If the initial internal volume is increased by 0.25 mL such as by the volume-increasing means for increasing the volume of syringe dead space, this lowers the aspiration pressure to -9.8 PSI when the syringe 100 is aspirated to 1 mL. This 2 PSI difference can have a significant impact on the leak performance of the syringe 100.

[0062] FIGS. 3-17 illustrate various volume-increasing means for increasing the volume of syringe dead space in the syringe 100. The volume-increasing means illustrated in FIGS. 3-17 are generally divided among groups directed to increases in the syringe-tip volume 142 (FIGS. 3 and 4), the conical barrel volume 124 (FIGS. 5-15), and a cylindrical barrel volume 144 proximal of the conical barrel volume 124 in the tipped end portion of the barrel 102 (FIGS. 16 and 17); however, division of the volume-increasing means in accordance with the foregoing groups does not preclude, for example, an increase in the syringe-tip volume 142 from also increasing the conical barrel volume 124 or, for example, an increase in the conical barrel volume 124 from also increasing the cylindrical barrel volume 144. Indeed, each volume of the syringe-tip volume 142, the conical barrel volume 124, and the cylindrical barrel volume 144 touches or even overlaps at least one other volume of the syringe-tip volume 142, the conical barrel volume 124, and the cylindrical barrel volume 144 to some degree such that an increase in some volume of the syringe-tip volume 142, the conical barrel volume 124, or the cylindrical barrel volume 144 can change some other volume of the syringe-tip volume 142, the conical barrel volume 124, or the cylindrical barrel volume 144 whether that change is an increase or decrease in the other volume. Further, division of the volume-increasing means in the foregoing groups does not preclude, for example, an increase in a combination of two or more volumes selected from the syringe-tip volume 142, the conical barrel volume 124, and the cylindrical barrel volume 144, wherein the increase in the combination of volumes is not due to adjacent volumes simply touching or overlapping.

[0063] Notably, the various volume-increasing means for increasing the volume of syringe dead space in the syringe 100 do not include adapters (e.g., Luer-to-Luer adapters) or the like configured to fit onto the syringe 100. Indeed, each such adapter or the like might add an additional volume to the syringe 100, but the additional volume is an external volume to that of the volume of syringe dead space in the syringe 100.

[0064] FIGS. 3 and 4 illustrate various volume-increasing means for increasing the volume of syringe dead space in the syringe 100 by way of the syringe-tip volume 142 in accordance with some embodiments.

[0065] As shown, the volume-increasing means for increasing the volume of syringe dead space can include an increase in the syringe-tip volume 142. Such an increase in the syringe-tip volume 142 can be through an increase in a bore length of the bore 120 through the syringe tip 106, an increase in a bore diameter of the bore 120 through the syringe tip 106, or some combination thereof. As set forth above, the bore 120 through the syringe tip 106 can be cylindrical or conical. Any increase to the bore diameter of the bore 120 can therefore be an increase in a constant bore diameter of the cylindrical bore, an increase in a minimum bore diameter of the conical bore, or an increase in a maximum bore diameter of the conical bore. Notably, any increase in the minimum or maximum bore diameter of the conical bore, as well as increases in both the minimum and maximum bore diameters of the conical bore, is accompanied by increases in intervening bore diameters of the conical bore.

[0066] FIG. 5 illustrates a volume-increasing means for increasing the volume of syringe dead space in the syringe 100 by way of the conical barrel volume 124 in accordance with some embodiments.

[0067] As shown, the volume-increasing means for increasing the volume of syringe dead space can include an increase in the conical barrel volume 124 within the tipped end portion of the barrel 102. Such an increase in the conical barrel volume 124 can be through an increase in a length of the tapered portion 122 of the tipped end portion of the barrel 102 that tapers from the barrel diameter of the barrel 102 down to the syringe-tip diameter, thereby defining an elongated conical barrel volume within the tipped end portion of the barrel 102.

[0068] Notably, the foregoing increase in the conical barrel volume 124 within the tipped end portion of the barrel 102 is differentiated from the following increases in the conical barrel volume 124 in that the elongated conical barrel volume results from a modification tothe tipped end portion of the barrel 102 instead of modifications to the piston 132 of the plunger 104.

[0069] FIGS. 6-15 illustrate various other volume-increasing means for increasing the volume of syringe dead space in the syringe 100 by way of the conical barrel volume 124 in accordance with some embodiments.

[0070] As shown, the volume-increasing means for increasing the volume of syringe dead space can include an increase in the remaining volume of the conical barrel volume 124 that remains in the tipped end portion of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. Such an increase in the remaining conical barrel volume 124 when the plunger 104 is completely advanced into the barrel 102 can include a modification to the piston 132 such as a modification to a shape of the piston 132. The modification to the piston 132 increases space between the piston 132 and the conical barrel surface 123 within the tipped end portion of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100, thereby increasing the remaining volume of the conical barrel volume 124 that remains in the tipped end portion of the barrel 102 when the plunger 104 is completely advanced into the barrel 102. However, it should be understood that, in some embodiments, the cylindrical volume can also be increased by the modification to the piston 132.

[0071] FIG. 9 illustrates an increase in the volume of syringe dead space through a cylindrical piston 145 for the piston 132 of the plunger 104 in accordance with some embodiments.

[0072] As shown, the modification to the piston 132 can include a modification to the shape of the piston 132 such that it is the cylindrical piston 145 of FIG. 9 instead of a conical piston such as the conical piston 132 of FIG. 2, which mates with the conical barrel surface 123 within the tipped end portion of the barrel 102. The cylindrical piston 145 increases space between the piston 132 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. Notably, the cylindrical piston 145 can be reduced in its length, height, or the like such that it approaches an ‘O’-ring fitted over the distal end portion of the plunger shaft 130. Indeed, the cylindrical piston 145 can instead be an ‘O’-ring or a pair of ‘O’-rings, thereby providing the leading ring 138 the trailing ring 140.

[0073] FIGS. 6 and 10 illustrate increases in the volume of syringe dead space through recesses in the piston 132 of the plunger 104 in accordance with some embodiments.

[0074] As shown, the modification to the piston 132 can include a modification to the shape of the piston 132 such that it includes a recess 146 in the piston surface 143 of the piston 132. If not for the recess 146 in the conical piston 132 shown in FIG. 6, the conical piston 132 would mate with the conical barrel surface 123 within the tipped end portion of the barrel 102. The recess 146 in the piston surface 143 of the conical piston 132 thusly increases space between the conical piston 132 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. As to the recess 146 in the piston surface 143 of the cylindrical piston 145 shown in FIG. 10, the recess 146 in the piston surface 143 further increases space between the cylindrical piston 145 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100.

[0075] FIG. 7 illustrates an increase in the volume of syringe dead space through an inverted conical piston 147 for the piston 132 of the plunger 104 in accordance with some embodiments.

[0076] As shown, the modification to the piston 132 can include a modification to the shape of the piston 132 such that it includes the inverted conical piston 147 instead of the conical piston 132 that mates with the conical barrel surface 123 within the tipped end portion of the barrel 102. Like the recess 146 in the piston surface 143 of the conical piston 132, the inverted conical piston 147 increases space between the piston 132 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100.

[0077] FIGS. 12 and 13 illustrate an increase in the volume of syringe dead space through a waffled piston surface for the piston surface 143 of the cylindrical piston 145 of the plunger 104 in accordance with some embodiments.

[0078] As shown, the modification to the piston 132 can include a modification to the shape of the piston 132 or the piston surface 143 thereof such that it includes waffling 148 for the waffled piston surface of the piston 132. While not shown for the conical piston 132, the conical piston 132 would mate with the conical barrel surface 123 within the tipped end portion of the barrel 102 if not for the waffled piston surface of the conical piston 132. The waffling148 in the piston surface 143 of the conical piston 132 thusly increases space between the conical piston 132 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. As to the waffling 148 in the piston surface 143 of the cylindrical piston 145 shown in FIGS. 12 and 13, the waffling 148 in the piston surface 143 further increases space between the cylindrical piston 145 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100. Further, the waffling 148 in the piston surface 143 of the conical piston 132 or the cylindrical piston 145 prevents all the air from being flushed from the syringe 100 even if it is filled with a fluid (e.g., saline) before a procedure. The waffling 148 in the piston surface 143 of the conical piston 132 or the cylindrical piston 145 does this by creating air pockets small enough that surface tension of the fluid causes the fluid to bridge over pockets in the waffled piston surface.

[0079] FIG. 14 illustrates an increase in the volume of syringe dead space through one or more protrusions 150 extending from the piston surface 143 of the conical piston 132 of the plunger 104 in accordance with some embodiments.

[0080] As shown, the modification to the piston 132 can include a modification to the shape of the conical piston 132 or the piston surface 143 thereof such that it includes the one- or-more protrusions 150 extending from the piston surface 143 of the conical piston 132 toward the conical barrel surface 123 within the tipped end portion of the barrel 102. The one-or-more protrusions 150 of the conical piston 132 prevent the piston surface 143 of the conical piston 132 from mating with the conical barrel surface 123 of the barrel 102, thereby increasing space between the conical piston 132 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is advanced into the barrel 102 as far as possible in the ready -to-aspirate state of the syringe 100. Notably, while the one-or-more protrusion are not shown extending from the cylindrical piston 145 or the piston surface 143 thereof, it should be understood the cylindrical piston 145 can be so modified to a similar effect as the conical piston 132. In addition, whether the conical piston 132, the cylindrical piston 145, or either piston surface 143 thereof includes the one-or-more protrusions 150 extending therefrom, the one-or-more protrusions 150 can stop the plunger 104 from being completely advanced into the barrel 102 in the ready -to- aspirate state of the syringe 100, thereby adding to the conical barrel volume 124 somecylindrical barrel volume 144 proximal of the conical barrel volume 124 for an additional increase in the volume of syringe dead space.

[0081] FIGS. 8 and 11 illustrate an increase in the volume of syringe dead space through a porous insert 152 coupled to the piston 132 of the plunger 104 in accordance with some embodiments.

[0082] As shown, the modification to the piston 132 can include a modification to the shape of the piston 132 or the piston surface 143 thereof such that it includes the porous insert 152 coupled to the piston surface 143 of the piston 132. If not for the porous insert 152 coupled to the piston surface 143 of the conical piston 132 shown in FIG. 8, the conical piston 132 would mate with the conical barrel surface 123 within the tipped end portion of the barrel 102. Indeed, the porous insert 152 is configured to provide a porous interface and, thus, space by way of pores throughout the porous interface, between the conical piston 132 and the conical barrel surface 123 within the tipped end portion of the barrel 102. The porous insert 152 coupled to the piston surface 143 of the conical piston 132 thusly increases space between the conical piston 132 and the conical barrel surface 123 of the barrel 102 when the plunger 104 is advanced into the barrel 102 as far as possible in the ready -to-aspirate state of the syringe 100. As to the porous insert 152 coupled to the piston surface 143 of the cylindrical piston 145 shown in FIG. 11, the porous insert 152 coupled to the piston surface 143 of the cylindrical piston 145 is likewise configured to provide a porous interface and, thus, space by way of pores throughout the porous interface, between the cylindrical piston 145 and the conical barrel surface 123 within the tipped end portion of the barrel 102. Notably, whether the conical piston 132, the cylindrical piston 145, or either piston surface 143 thereof includes the porous insert 152 coupled thereto, the porous insert 152 can stop the plunger 104 from being completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100, thereby adding to the conical barrel volume 124 some cylindrical barrel volume 144 proximal of the conical barrel volume 124 for an additional increase in the volume of syringe dead space.

[0083] FIG. 15 illustrates an increase in the volume of syringe dead space through a hollow conical piston 154 for the piston 132 of the plunger 104 in accordance with some embodiments.

[0084] As shown, the volume-increasing means for increasing the volume of syringe dead space includes the hollow piston 154 with a slit 156 through the piston surface 143 leadingto an otherwise enclosed space within the hollow piston 154. While the conical piston 132 can mate with the conical barrel surface 123 within the tipped end portion of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100, the elastomeric septum and the slit 156 through the piston surface 143 thereof is configured to allow air to pass from the enclosed space within the hollow piston 154 at a relatively high aspiration pressure, thereby adding some volume to at least the conical barrel volume 124 for an additional increase in the volume of syringe dead space. Advantageously, the hollow piston 154 and the slit 156 through the piston surface 143 thereof is also configured to prevent air from passing from the enclosed space within the hollow piston 154 at a relatively low aspiration pressure. Such control over allowing air to pass from the enclosed space within the hollow piston 154 at relatively high aspiration pressure or preventing the air to pass therefrom at relatively low aspiration pressure can be through some combination of features selected from a modulus of elasticity of the hollow piston 154, a slit length of the slit 156 through the piston surface 143 thereof, and a thickness of each flap of the hollow conical piston 154 on either side of the slit 156.

[0085] FIGS. 16 and 17 illustrate various volume-increasing means for increasing the volume of syringe dead space in the syringe 100 by way of the cylindrical barrel volume 144 in accordance with some embodiments.

[0086] As shown, the volume-increasing means for increasing the volume of syringe dead space can include addition of the cylindrical barrel volume 144 proximal of the conical barrel volume 124 in the tipped end portion of the barrel 102. Such a cylindrical barrel volume 144 added to the conical barrel volume 124 defines a cumulative barrel volume within a distal portion of the barrel 102 when the plunger 104 is completely advanced into the barrel 102 in the ready -to-aspirate state of the syringe 100, thereby increasing the remaining volume of the conical barrel volume 124 that remains in the tipped end portion of the barrel 102 by the cumulative barrel volume when the plunger 104 is completely advanced into the barrel 102.

[0087] FIG. 16 illustrates an increase in the volume of syringe dead space through a decrease in a plunger length of the plunger 104 in accordance with some embodiments.

[0088] As shown, the addition of the cylindrical barrel volume 144 proximal of the conical barrel volume 124 in the tipped end portion of the barrel 102 can be through some decrease in the length of the plunger shaft 130 of the plunger 104. Notably, like any volume-increasing means for increasing the volume of syringe dead space, the length of the plunger shaft 130 can be customized to obtain a target maximum aspiration pressure of the syringe 100. For example, the plunger shaft 130 can be shorter or longer in instances where a greater or lesser pressure-lowering effect is desired.

[0089] FIG. 17 illustrates an increase in the volume of syringe dead space through an effective decrease in the plunger length by way of a stop 158 in the plunger shaft 130 of the plunger 104 in accordance with some embodiments.

[0090] As shown, the addition of the cylindrical barrel volume 144 proximal of the conical barrel volume 124 in the tipped end portion of the barrel 102 can be through the stop 158 in the plunger shaft 130 of the plunger 104. The stop 158 in the plunger shaft 130 is configured to stop the plunger 104 from being completely advanced into the barrel 102 in the ready-to-aspirate state of the syringe 100. Such a stop 158 can be a longitudinal insert transversely inserted through a through hole through one or more struts of the orthogonal struts 136 of the plunger shaft 130. Advantageously, the insert can be removably inserted through the through hole through the one-or-more orthogonal struts 136 of the plunger shaft 130 such that the insert can be removed to allow full strokes of the plunger 104 through the barrel chamber 112.

[0091] Notably, the volume-increasing means for increasing the volume of syringe dead space can include addition of some volume to the cylindrical barrel volume 144 through a modification of the barrel 102. While not shown, such a modification of the barrel 102 can include one or more longitudinal grooves in the barrel wall 116 or a bulb or bulge in the barrel wall 116 proximal of the tapered portion 122 of the barrel 102. As to the one-or-more longitudinal grooves in the barrel wall 116, the piston 132 can also be modified with one or more radial protrusions configured to occupy the one-or-more longitudinal grooves in the barrel wall 116, thereby forming a seal between the piston 132 and the barrel wall 116 for aspirating the syringe 100. As to the bulb or bulge in the barrel wall 116, the length of the plunger shaft 130 of the plunger 104 can be decreased as set forth above to maintain the seal between the piston 132 and the barrel wall 116 for aspirating the syringe 100. Thus, the volume added to the cylindrical barrel volume 144 by way of the bulb or bulge in the barrel wall 116 can be in addition to that already added by the decrease in the length of the plunger shaft 130 of the plunger 104.

[0092] Advantageously, limiting the maximum aspiration pressure allows more options for leak testing at higher-elevation (lower-pressure) locations. The current aspiration pressure that can be generated with a 5-mL syringe as the syringe 100 when aspirated to 1 mL at sea level is nearly identical to the typical atmospheric pressure in Salt Lake City, UT. Many vacuum pumps are unable to generate enough vacuum pressure at such a location to be representative of the pressure the syringe 100 would encounter during aspiration at sea level, thereby complicating design verification and other testing plans. If the maximum aspiration pressure that could be generated within the syringe 100 was limited to a value such as -10 PSI, this would be a more feasible pressure to test at than an aspiration pressure magnitude that is approaching (or exceeds) local atmospheric pressure for a location such as Salt Lake City, UT.Methods

[0093] Methods can include methods for making or using syringes for reducing the maximum aspiration pressure of the syringes. In an example, a method of making the syringe 100 can include molding the barrel 102, the plunger 104, and the piston 132; and assembling the syringe 100. In another example, a method of using the syringe 100 can include aspirating the syringe 100 with the reduced maximum aspiration pressure of the syringe 100 in accordance with the volume-increasing means for increasing the volume of dead space in the syringe 100.

[0094] While some particular embodiments have been disclosed herein, and while the particular embodiments have been disclosed in some detail, it is not the intention for the particular embodiments to limit the scope of the concepts provided herein. Additional adaptations or modifications can appear to those of ordinary skill in the art, and, in broader aspects, these adaptations or modifications are encompassed as well. Accordingly, departures may be made from the particular embodiments disclosed herein without departing from the scope of the concepts provided herein.

Claims

CLAIMSWhat is claimed is:

1. A syringe, comprising: a barrel including a tipped end portion and a mouthed end portion opposite the tipped end portion of the barrel, the tipped end portion of the barrel tapering from a barrel diameter of the barrel down to a syringe-tip diameter of a connecting portion of a syringe tip that extends from the tipped end portion of the barrel, thereby defining a conical barrel surface and a corresponding conical barrel volume within the tipped end portion of the barrel; a plunger disposed in the barrel by way of a mouth in the mouthed end portion of the barrel, the plunger including an elastomeric piston fitted over an end portion of a plunger shaft that forms a circumferential seal with an inner surface of the barrel; and a volume-increasing means for increasing a volume of syringe dead space in the syringe, the volume-increasing means reducing a maximum aspiration pressure of the syringe.

2. The syringe of claim 1, wherein the volume of syringe dead space increased by the volume-increasing means includes a syringe-tip volume within the syringe tip plus any remaining volume of the conical barrel volume that remains in the tipped end portion of the barrel when a) a piston surface of the elastomeric piston substantially complements the conical barrel surface within the tipped end portion of the barrel and b) the plunger is completely advanced into the barrel in a ready-to-aspirate state of the syringe such that the piston surface of the elastomeric piston mates with the conical barrel surface of the barrel.

3. The syringe of claim 2, wherein the volume-increasing means for increasing the volume of syringe dead space includes an increase in the syringe-tip volume through an increase in a bore length of a bore of the syringe tip, an increase in a bore diameter of the bore of the syringe tip, or some combination thereof.

4. The syringe of either claim 2 or 3, wherein the volume-increasing means for increasing the volume of syringe dead space includes an increase in the conical barrel volume within the tipped end portion of the barrel through an increase in a length of a tapered portion of the tipped end portion of the barrel that tapers from the barrel diameter of the barrel downto the syringe-tip diameter, thereby defining an elongated conical barrel volume within the tipped end portion of the barrel.

5. The syringe of any of claims 2-4, wherein the volume-increasing means for increasing the volume of syringe dead space includes an increase in the remaining volume of any conical barrel volume that remains in the tipped end portion of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

6. The syringe of claim 5, wherein the volume-increasing means for increasing the volume of syringe dead space includes a modification to a shape of the elastomeric piston, thereby increasing space between the elastomeric piston and the conical barrel surface within the tipped end portion of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

7. The syringe of claim 6, wherein the modification to the shape of the elastomeric piston includes a recess in the piston surface of a conical elastomeric piston that otherwise mates with the conical barrel surface within the tipped end portion of the barrel, the recess in the piston surface increasing space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to- aspirate state of the syringe.

8. The syringe of claim 6, wherein the modification to the shape of the elastomeric piston includes waffling in the piston surface of a conical elastomeric piston that otherwise mates with the conical barrel surface within the tipped end portion of the barrel, the waffling in the piston surface increasing space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to- aspirate state of the syringe.

9. The syringe of claim 6, wherein the modification to the shape of the elastomeric piston includes a cylindrical elastomeric piston instead of a conical elastomeric piston that mates with the conical barrel surface within the tipped end portion of the barrel, the cylindrical elastomeric piston increasing space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to- aspirate state of the syringe.

10. The syringe of claim 9, wherein the modification to the shape of the elastomeric piston further includes a recess in the piston surface of the cylindrical elastomeric piston, the recess in the piston surface further increasing space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

11. The syringe of claim 9, wherein the modification to the shape of the elastomeric piston further includes waffling in the piston surface of the cylindrical elastomeric piston, the waffling in the piston surface further increasing space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

12. The syringe of claim 6, wherein the modification to the shape of the elastomeric piston includes an inverted conical elastomeric piston instead of a conical elastomeric piston that mates with the conical barrel surface within the tipped end portion of the barrel, the inverted conical elastomeric piston increasing space between the elastomeric piston and the conical barrel surface of the barrel when the plunger is completely advanced into the barrel in the ready-to-aspirate state of the syringe.

13. The syringe of any of claims 6-12, wherein the modification to the shape of the elastomeric piston includes one or more protrusions extending from the piston surface of the elastomeric piston toward the conical barrel surface within the tipped end portion of the barrel, the one-or-more protrusions of the elastomeric piston preventing the piston surface of the elastomeric piston from mating with the conical barrel surface of the barrel.

14. The syringe of any of claims 2-6, 9, and 13, wherein the volume-increasing means for increasing the volume of syringe dead space includes a hollow elastomeric piston with a slit through the piston surface leading to an otherwise enclosed space within the hollow elastomeric piston.

15. The syringe of claim 14, wherein the elastomeric septum and the slit through the piston surface thereof is configured to allow air to pass into the enclosed space within the hollow elastomeric piston at a relatively high aspiration pressure as well as prevent air to pass into the enclosed space within the hollow elastomeric piston at a relatively low aspiration pressure.

16. The syringe of any of claims 2-15, wherein the volume-increasing means for increasing the volume of syringe dead space includes addition of a cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel, thereby defining a cumulative barrel volume within a distal portion of the barrel.

17. The syringe of claim 16, wherein the addition of the cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel is through a decrease in a length of the plunger shaft of the plunger.

18. The syringe of claim 16, wherein the addition of the cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel is through a porous insert coupled to the piston surface of the elastomeric piston configured to stop the plunger from being completely advanced into the barrel in the ready -to-aspirate state of the syringe.

19. The syringe of claim 16, wherein the addition of the cylindrical barrel volume proximal of the conical barrel volume in the tipped end portion of the barrel is through a stop in the plunger shaft of the plunger configured to stop the plunger from being completely advanced into the barrel in the ready -to-aspirate state of the syringe.

20. A method for reducing a maximum aspiration pressure of a syringe, comprising: aspirating with the syringe, the syringe including: a barrel including a tipped end portion and a mouthed end portion opposite the tipped end portion of the barrel, the tipped end portion of the barrel tapering from a barrel diameter of the barrel down to a syringe-tip diameter of a connecting portion of a syringe tip that extends from the tipped end portion of the barrel, thereby defining a conical barrel surface and a corresponding conical barrel volume within the tipped end portion of the barrel; a plunger disposed in the barrel by way of a mouth in the mouthed end portion of the barrel, the plunger including an elastomeric piston fitted over an end portion of a plunger shaft that forms a circumferential seal with an inner surface of the barrel; and a volume-increasing means for increasing a volume of syringe dead space in the syringe, the volume-increasing means reducing the maximum aspiration pressure of the syringe while aspirating with the syringe.

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