Syringes for infusion pumps

Abstract

Embodiments of syringes and components thereof described herein provide reduced compliance from bending or deformation of not only the syringe barrel but also the syringe plunger rod and plunger seal. Additionally, embodiments of syringes and components thereof described herein provide an improved seal between the barrel and syringe plunger rod, and provide improved resistance to pressure. Embodiments of syringes and components thereof described herein are advantageously suited for use with infusion pumps, which may subject the syringe to numerous start / stop operations over extended periods of time, and which sometimes have very low flow rates.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 407,512, filed September 16, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates generally to syringes, and more particularly to syringes for use with infusion pumps. [Background technology]

[0003] Infusion pumps are highly useful medical devices for providing patients with controlled amounts of prescribed fluids, medications, and other therapeutic agents (collectively referred to as "infusates"). Medications, such as antibiotics, chemotherapy drugs, vasoactive agents, insulin, blood products, and painkillers, as well as nutrients and other nutritional supplements, are commonly delivered to patients via infusion pumps. Infusion pumps have been used in hospitals, nursing homes, and other short- and long-term care facilities, as well as in home care settings. Infusion pumps can be particularly useful for delivering therapeutic agents that require long administration times. There are many types of infusion pumps, including high-volume pumps, patient-controlled analgesia (PCA) pumps, elastomeric pumps, syringe pumps (syringe drivers), enteral pumps, and insulin pumps. Infusion pumps are typically useful for a variety of drug delivery routes, including intravenous, intraarterial, subcutaneous, intraperitoneal, intraosseous, intraportal, near nerves, and intraoperative, intradural or intrathecal, etc.

[0004] Syringe pumps have many desirable features and are generally recognized as the most precise and accurate acute care infusion pumps available. Syringe pumps can support lower flow rates than large volume or portable pumps, sometimes supporting flow rates as low as 0.01 mL / h (with appropriately sized small syringes). Unlike large volume and portable pumps, which are proprietary or use dedicated consumables, syringe pumps typically accommodate a wide range of commonly used or "off-the-shelf" syringe brands and sizes and are typically coupled to an extensive set of non-proprietary syringes for delivering infusions to patients.

[0005] However, conventional off-the-shelf syringes are not specifically designed for use in syringe pumps, as only a very small percentage of syringes used worldwide are used with pumps. Typically, off-the-shelf syringes are designed for manual, hand-operated use. However, when used with a syringe pump, the pump must identify or be configured accordingly with the relevant features of the off-the-shelf syringe for proper pump operation. Challenges with syringe pump systems can arise from both the pump and the syringe. Some syringe pumps, especially at low flow rates (less than 5 mL per hour, especially less than 0.1 mL / h), may have performance limitations, including, but not limited to, the length of start-up time to reach the target flow rate, non-uniformity of the flow profile during infusion delivery, the length of time to an occlusion alarm, and the risk of mis-delivery of a bolus or reflux. Furthermore, some off-the-shelf syringes may contribute to inaccuracies due to syringe compliance (e.g., deformation under pressure). Syringe compliance can cause, among other issues, increased time for the syringe pump to reach the programmed target flow rate, increased time for the syringe pump to recognize an occlusion, and increased unintended bolus volumes or no-flow periods due to changes in syringe pump height while in operation. Additional inaccuracies can arise from changes in backpressure when multiple pumps are added to the same infusion line.

[0006] Prefabricated syringes have characteristics that can change over time, intentionally or unintentionally, thereby affecting pump performance. Furthermore, prefabricated syringes can contribute to nonuniformity and short-term inaccuracies in flow rates, particularly due to the "stick-slip" phenomenon. Under the "stick-slip" phenomenon, the delivered flow rate becomes discretized after the flow rate unintentionally reaches zero (or decreases). Some prefabricated syringes exhibit high frictional forces, which, combined with the mechanical compliance of the pump, can cause stick-slip or delay the onset of flow. In experiments relevant to this disclosure, a commercially available 50 mL syringe was operated in a syringe pump at a flow rate of 0.5 mL per hour for 84 hours. After approximately 30 hours of achieving the nominal flow rate, spontaneous episodes of stick-slip flow began to occur, resulting in nonuniform fluid delivery from the syringe, as shown in Figure 1.

[0007] While significant improvements have been made and continue to be made in the structure, construction, and operation of syringe pumps, there remains a need for improvements in the syringes themselves for use with syringe pumps. The present disclosure addresses these concerns. Summary of the Invention

[0008] The embodiments described or contemplated herein substantially provide, among other advantages, ease of use, operation, accuracy, and improved patient safety in the delivery of infusion fluids.

[0009] Among the features and advantages of embodiments, syringe pumps operating on syringes according to embodiments described herein are characterized by reduced pump start-up time and reduced syringe exchange time. Among the features and advantages of embodiments, the time to detection of a syringe pump blockage is reduced. Among the features and advantages of embodiments, the completeness of delivery of an infusion dose is improved.

[0010] Features and advantages of embodiments include improved consistency of medication flow delivered from the syringe and reduced delivery anomalies such as stick-slip. Syringe embodiments described herein improve both short-term and long-term pump accuracy over the full range of pump operation and reduce performance dependency on environmental conditions such as backpressure, temperature, or fluid changes.

[0011] Among the features and advantages of embodiments, unintended bolus volumes and periods of no flow (eg, due to syringe pump height changes during operation) are reduced.

[0012] Embodiments of syringes and components thereof described herein provide reduced compliance from bending or deformation of not only the syringe barrel but also the syringe plunger rod and plunger seal. Additionally, embodiments of syringes and components thereof described herein provide an improved seal between the barrel and syringe plunger rod, and provide improved resistance to pressure. Embodiments of syringes and components thereof described herein are advantageously suited for use with infusion pumps, which may subject the syringe to numerous start / stop operations over extended periods of time, and which sometimes have very low flow rates.

[0013] The above summary is not intended to describe each illustrated embodiment or every implementation of the subject matter of the present application. The figures and the detailed description that follow more particularly exemplify various embodiments.

[0014] The subject matter of the present application may be more fully understood by considering the following detailed description of various embodiments in connection with the accompanying drawings. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a graph of flow rate over time for a prior art syringe, illustrating the non-uniform fluid delivery from the syringe. [Figure 2]FIG. 2 is a perspective view of an example syringe pump for use with embodiments of the present disclosure. [Figure 3] FIG. 3 is an exploded perspective view of a syringe according to an embodiment of the present disclosure. [Figure 4] FIG. 4 is a perspective view of a plunger rod according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a perspective view of a sealing element of a plunger rod according to an embodiment of the present disclosure. [Figure 6] FIG. 6 is a perspective view of a plunger rod having a sealing element coupled thereto, according to an embodiment of the present disclosure. [Figure 7] FIG. 7 is a cross-sectional view of a distal end of a syringe according to an embodiment of the present disclosure. [Figure 8] FIG. 8 is another perspective view of a plunger rod having a sealing element coupled thereto in accordance with an embodiment of the present disclosure. [Figure 9] FIG. 9 is a perspective view of a distal end of a syringe according to an embodiment of the present disclosure. [Figure 10] FIG. 10 is a graph showing prior art syringe compliance compared to syringes according to embodiments of the present disclosure. [Figure 11] FIG. 11 is a graph of test results showing force versus distance for a prior art syringe compared to a syringe according to an embodiment of the present disclosure. [Figure 12] FIG. 12 is a graph of test results showing flow rates over time for a prior art syringe operating in a syringe pump compared to a syringe according to an embodiment of the present disclosure for a first set of test conditions. [Figure 13] FIG. 13 is a graph of test results showing flow rates over time for a prior art syringe operating in a syringe pump compared to a syringe according to an embodiment of the present disclosure for a second set of test conditions. [Figure 14]FIG. 14 is a graph of test results showing flow rate over time for a prior art syringe compared to a syringe according to an embodiment of the present disclosure for a third set of test conditions. DETAILED DESCRIPTION OF THE INVENTION

[0016] While the embodiments are susceptible to various modifications and alternative forms, specifics thereof are shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the subject matter to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the subject matter of the present disclosure, in accordance with the appended claims.

[0017] 2, an example of a syringe pump 100 for use with embodiments of the present disclosure is depicted. Syringe pump 100 may include a housing 102, a user interface 104, a syringe drive assembly 106, and a syringe receptacle 108.

[0018] Syringe drive assembly 106 can be used to control the delivery of a prescribed amount or dose of infusion fluid to a patient from a syringe (not shown in FIG. 2 ) mounted in pump 100 by mechanically advancing a plunger within the syringe to deliver a controlled amount of infusion fluid through an infusion line fluidly connected to the syringe. In one example, a motor within pump 100 rotates a lead screw, which in turn moves a plunger driver head assembly of syringe drive assembly 106 toward syringe receptacle 108. This movement then pushes the plunger within the barrel of a syringe positioned within receptacle 108, while the barrel is held substantially in place. Moving the syringe plunger forward acts to displace a volume of infusion fluid within the syringe out of the syringe, into the infusion line, and ultimately to the patient.

[0019] 2, syringe receptacle 108 provides a cavity extending across the front of syringe pump 100 that allows easy and consistent viewing of a syringe installed therein. Syringe receptacle 108 is shaped and sized to accept various sizes and brands of syringes for installation therein for delivery of infusion fluids.

[0020] 3-9, an example syringe 200 according to one embodiment of the present disclosure is depicted including a barrel 210, a plunger rod 240, and a sealing element 270. As in FIG. 6, the sealing element 270 is coupled to the plunger rod 240, which is operable to translate along the longitudinal axis of the barrel 210 and expel infusion fluid into the barrel 210. The barrel 210 generally includes a tip 212 at its distal end and a neck 216, a body 218, and a flange 220 at its proximal end. The tip 212 includes an opening therein and can be configured as desired for connection to various types of extension sets, such as luer locks, tips for enteral feeding catheters (including ENFits), and tips for epidural catheters (including NRFits), as well as other types of extension sets, including those conforming to current ISO standards. Neck 216 may be tapered as depicted in the drawings, although other variations are contemplated. Body 218 of barrel 210 may be sized and shaped for a variety of common syringe volumes, e.g., from 1 mL to 100 mL. Flange 220 may be configured to interface with a corresponding retention feature on a syringe pump, for example, to help secure syringe 200 within the pump during operation. An opening is present at the proximal end of barrel 210, leading to a cavity 224 defined within barrel 210 and thus within inner wall 226. Cavity 224 is configured to hold an infusion solution therein. In embodiments, a coating 228 (not labeled in the drawings) may be applied to inner wall 226. In embodiments, coating 228 may include silicone oil, a non-silicone oil alternative, or other coating for lubricity. In one embodiment, coating 228 may include a tribofilm.

[0021] 4, plunger rod 240 includes a substantially rigid nose portion 242 at its distal end and a plunger face (or stopper) 244, a press portion 246, and a shaft 247 at its proximal end. As shown schematically in the figure, shaft 247 includes a plurality of ribs 248 arranged in a "+" configuration. Other configurations of ribs 248 are also contemplated. In one embodiment, nose portion 242 extends into tip portion 212 of barrel 210 when the syringe is fully depressed, advantageously allowing the infusion fluid within tip 212 to be expelled without causing bending of plunger face 244. Additionally, the profile of plunger face 244 may be configured to match the profile of neck 216 of barrel 210. In one embodiment, plunger face 244 may include dimples on its surface to prevent or reduce inadvertent bonding (e.g., suction cup bonding) between plunger face 244 and the inside of neck 216. In embodiments, the stiffness of plunger face 244 significantly reduces compliance compared to prior approaches that have featured elastomeric materials or the like that tend to compress or expand during use.

[0022] With continued reference to FIG. 4 , the plunger rod 240 further includes a sealing region 250, which in the illustrated embodiment is adjacent the plunger face 244. The sealing region 250 is configured to receive a sealing element 270 thereon and generally includes an inner ring 252, a lower (or first) flange 254, and an upper (or second) flange 256. Further, with reference to FIG. 7 , the sealing element 270 is coupleable to the sealing region 250 such that the sealing element 270 is bounded by the lower flange 254 and the upper flange 256. The inner ring 252 provides support for the sealing element 250 between the flanges 254 and 256. The plunger 240 further includes a reinforcing ring 258 adjacent the sealing region 250. The reinforcing ring 258 may have a diameter similar to the diameters of the lower flange 254 and the upper flange 256. The reinforcing ring 258 is configured to limit lateral distortion of the plunger rod 240 relative to the barrel 210, thereby reducing syringe leakage due to normal forces exerted on the syringe while installed in the pump or while external to the pump, and reducing the force required to actuate the syringe plunger.

[0023] Suitable materials for plunger rod 240 include medical-grade plastics that are rigid and easy to process, for example, via injection molding. One such well-known material is polycarbonate.

[0024] 5-7 , sealing element 270 includes a body 272, an inner diameter 274, and an outer diameter 278. In embodiments, inner diameter 274 may include a circumferential channel 276 configured to cooperatively engage inner ring 252 of plunger rod 240. Outer diameter 278 includes one or more sealing portions. As shown schematically in the figures, sealing element 270 includes a first sealing portion 280 and a second sealing portion 282 disposed on outer diameter 278. Sealing portions 280 and 282 may include smooth surfaces, as shown, or in other embodiments, may include texture or convex or concave dimples to tailor the frictional characteristics of sealing element 270 as desired. Similarly, while sealing portions 280 and 282 are depicted as generally symmetrical, it should be understood that asymmetric configurations are contemplated, if desired. Additionally, the sealing element 270 includes a flange 284 configured to provide a robust surface against the upper flange 256 of the plunger rod 240, thereby helping to retain the sealing element 270 within the sealing region 250 of the plunger rod 240. The flange 284 also supports die cutting to separate multiple sealing elements from the compression molded sheet material of the integrally manufactured elements. Suitable materials for the sealing element 270 may include isoprene rubber or isobutylene-isoprene rubber.

[0025] Figure 8 shows another perspective view of a plunger rod having a sealing element coupled thereto. Figure 9 is a perspective view of a distal end of a syringe according to an embodiment of the present disclosure.

[0026] Several prototype syringes according to embodiments of the present disclosure were prepared and tested. Referring now to FIG. 10 , volume displacement tests were performed on a prior art 60 mL syringe and an improved 60 mL syringe constructed according to embodiments of the present disclosure. The volume displacement test was performed using a liquid-filled syringe with the syringe plunger fixed at a specific test position. A rigid liquid-filled tube was attached to the syringe, and an air pressure source was connected to the end of the tube. As the air pressure was increased, the water-air boundary was displaced toward the syringe. This displacement was measured and converted to a “displacement volume” and plotted as shown in FIG. 10 . Those skilled in the art will understand that, in the context of FIG. 10 , the “compliance” of a syringe is a parameter related to the volume displaced with respect to the applied pressure at a selected pressure.

[0027] 10, line 302 shows the volume displacement (y-axis) of a prior art syringe with its plunger / stopper positioned at the outlet (empty, e.g., all fluid expelled) versus the applied pressure (x-axis). Line 302 therefore shows the volume displacement of the plunger element alone. Line 304 shows the volume displacement with the stopper / plunger in the volume position (fully extended), and the difference between line 304 and line 302 therefore shows the volume displacement of the barrel element alone of the prior art syringe.

[0028] Tests were then performed on the improved syringe described herein by way of example and shown in Figures 3-9 referenced above. Line 306 represents the volumetric displacement when the plunger / stopper is positioned (empty) at the outlet. Therefore, line 306 represents the volumetric displacement of the plunger element alone. Line 308 represents the volumetric displacement when the plunger is fully extended from the barrel; therefore, the difference between lines 308 and 306 represents the volumetric displacement of the barrel element alone. Thus, the fully positioned improved syringe exhibits approximately an 80% reduction in volumetric displacement relative to the prior art syringe. Volumetric displacement represents the syringe's ability to expand under pressure to accommodate an incremental fluid volume. When operating with a syringe pump, which applies pressure to the syringe plunger to displace fluid toward the patient in a controlled manner, the reduced volumetric displacement translates into faster start-up times because less mechanical plunger displacement is required to pressurize the system and reach mechanical equilibrium prior to steady-state delivery. Similarly, a reduced volume displacement also reduces the time to occlusion alarm because the syringe's ability to absorb increments of fluid under pressure is reduced, causing it to reach the threshold pressure sooner than a syringe with a larger volume displacement.

[0029] Referring now to FIG. 11, tests were also conducted to determine the stick-slip phenomenon of a prior art syringe and a syringe constructed in accordance with an embodiment of the present disclosure. The initial application of force to the plunger rod must overcome the static friction between the plunger seal and the inside of the barrel. The force required to overcome the static friction and allow the plunger to begin moving is the actuation force, expressed as Fs. After Fs, the required force fluctuates slightly by decreasing and then increasing to Fmax. Fmax is the maximum force observed while the plunger is moving. By measuring Fs, Fmax, and calculating the mean value Fmean, the percentage difference between the values ​​of each parameter can be determined. A relatively small difference between the values ​​of these three parameters tends to result in a reduced stick-slip phenomenon, while a large difference between the values ​​tends to result in an increased stick-slip phenomenon. In FIG. 11, the x-axis represents distance and the y-axis represents force. Meanwhile, the upper line represents an improved syringe in accordance with an embodiment of the present disclosure, and the lower line represents a prior art syringe.

[0030] Various syringe embodiments were constructed and tested, and the results showed that for syringes constructed according to embodiments of the present disclosure and having a tribofilm coating applied to the inner surface of the barrel, the percentage difference measured (between Fs, Fmax, and Fmean) was only 1%. In contrast, prior art syringes were also tested, and the percentage difference between Fs, Fmax, and Fmean was 36%. Thus, the present disclosure represents a significant improvement in syringe operation.

[0031] 12-14, each shows flow rate error test results for an improved syringe according to an embodiment of the present disclosure (left graph) versus a prior art syringe (right graph), with notable data provided in a table. For example, the test parameters for FIG. 12 were a flow rate of 0.1 mL / h, a temperature of 35 degrees Celsius, and a back pressure of 600 mmHg. As is evident from the graphs and tabular data, the improved syringe is advantageously characterized by significantly faster start-up time, faster time to steady-state flow rate, and reduced steady-state delivered dose error.

[0032] Similarly, Figure 13 shows the results of tests conducted at a flow rate of 0.1 mL / h, a temperature of 23 degrees Celsius, and a back pressure of 0 mmHg. As is evident from the graphs and tabular data, the improved syringe advantageously features significantly faster start-up times, faster time to steady-state flow rate, and only a slight increase in steady-state delivery error.

[0033] Finally, Figure 14 shows the results of tests conducted at a flow rate of 10 mL / h, a temperature of 35 degrees Celsius, and a back pressure of 600 mmHg. As is evident from the graphs and tabular data, the improved syringe is advantageously characterized by a faster start-up time, a faster time to steady-state flow rate, and only a slight increase in steady-state delivery error.

[0034] Various embodiments of systems, devices, and methods are described herein. These embodiments are provided by way of example only and are not intended to limit the scope of the subject matter claimed herein. Furthermore, it should be understood that various features of the described embodiments can be combined in various ways to create various additional embodiments. Furthermore, while various materials, dimensions, shapes, configurations, positions, etc. are described for use with the embodiments of the present disclosure, others in addition to those disclosed may be utilized without departing from the scope of the subject matter claimed herein.

[0035] Those skilled in the relevant arts will recognize that the subject matter herein may include fewer features than those shown in the individual embodiments above. The embodiments described herein are not meant to be an exhaustive representation of ways in which various features of the subject matter herein may be combined. Thus, the embodiments are not mutually exclusive combinations of features; rather, various embodiments may include combinations of different individual features selected from different individual embodiments, as would be understood by one skilled in the art. Furthermore, elements described in connection with one embodiment can be implemented in other embodiments even when not described in such embodiment, unless otherwise specified.

[0036] Although a dependent claim may refer to a particular combination with one or more other claims therein, other embodiments may include combinations of the subject matter of that dependent claim with each of the other dependent claims, or combinations of one or more features of the other dependent or independent claims. Unless it is stated that a particular combination is not intended, such combinations are suggested herein.

[0037] The incorporation by reference of the above documents is limited so that no subject matter contrary to what is expressly disclosed herein is incorporated. The incorporation by reference of the above documents is further limited so that no claims contained therein are incorporated by reference. Additionally, the incorporation by reference of the above documents is further limited so that no definitions provided therein are incorporated by reference except as expressly included herein.

[0038] For purposes of claim interpretation, it is expressly intended that the provisions of 35 U.S.C. § 112(f) shall not apply unless the specific words "means for" or "step for" appear in the claim.

Claims

1. A syringe, the syringe comprising: a barrel including a body, a tapered distal end extending to a tip, and a proximal end open to a cavity defined within the barrel, the cavity having an interior wall coated with a lubricant; a plunger rod including a shaft, a plunger face, a distal elongated nose extending from the plunger face, a proximal press portion, and a sealing region, the sealing region having a first flange, a second flange, and an internal support disposed between the first flange and the second flange; a sealing element having a first sealing portion, a second sealing portion, and an inner channel, the sealing element configured to be operably coupled with the sealing region of the plunger rod such that the inner channel of the sealing element is disposed on the inner support portion of the plunger rod; the plunger rod is configured to be operably coupled within the cavity of the barrel and is translatable along a length of the barrel to selectively expel fluid from the cavity of the barrel and out of the tip; A syringe in which the elongated nose of the plunger rod is configured to extend into the tip of the barrel when the plunger rod is fully pressed into the barrel, thereby ejecting any liquid remaining in the tip without causing deformation of the plunger face.

2. A syringe, the syringe comprising: a barrel including a body, a tapered distal end extending to a tip, and a proximal end open to a cavity defined within the barrel, the cavity having an interior wall coated with a lubricant; a plunger rod including a shaft, a plunger face, a distal elongated nose extending from the plunger face, a proximal press portion, and a sealing region; a sealing element having a first sealing portion and a second sealing portion, the sealing element configured to be operably coupled with the sealing region of the plunger rod; the plunger rod is configured to be operably coupled within the cavity of the barrel and is translatable along a length of the barrel to selectively expel fluid from the cavity of the barrel and out of the tip; A syringe in which the elongated nose of the plunger rod is configured to extend into the tip of the barrel when the plunger rod is fully pressed into the barrel, thereby ejecting any liquid remaining in the tip without causing deformation of the plunger face.

3. 3. The syringe of claim 2, wherein the sealing region of the plunger rod comprises a first flange, a second flange, and an inner support disposed between the first flange and the second flange.

4. 4. The syringe of claim 3, wherein the sealing element further comprises an inner channel, the sealing element being configured to be operably coupled with the sealing region of the plunger rod such that the inner channel of the sealing element is positioned on the inner support portion of the plunger rod.

5. 5. The syringe of claim 4, wherein the plunger rod further comprises a reinforcing ring disposed on the shaft, the reinforcing ring configured to limit lateral distortion of the plunger rod relative to the barrel.

6. The syringe of claim 5 , wherein the first flange is adjacent to the plunger face.

7. The syringe of claim 6 , wherein the reinforcing ring is disposed proximal to the second flange.

8. The syringe of claim 2 , wherein the tip of the barrel is configured to be coupled with an extension set.

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