WO2016183342A1

WO2016183342A1 - High accuracy syringe pumps

Info

Publication number: WO2016183342A1
Application number: PCT/US2016/032144
Authority: WO
Inventors: John P. RUKAVINA; Christopher Allen Lacy
Original assignee: Smiths Medical Asd, Inc.
Priority date: 2015-05-13
Filing date: 2016-05-12
Publication date: 2016-11-17

Abstract

A high accuracy syringe pump that includes a pump housing and a drive assembly. The drive assembly includes a plunger driver head, a drive arm, a lead screw, a motor, and a linear potentiometer. The plunger driver head selectively urges against a syringe that defines a first central longitudinal axis. The drive arm includes an elongate plunger tube having a generally parallel longitudinal axis. The drive arm is coupled to the plunger driver head and movement of the elongate plunger tube corresponds with movement of the plunger of the syringe along the first central longitudinal axis. The linear potentiometer includes a double coil wound non- conductive rod generally in alignment with the second longitudinal axis and around which the elongate plunger tube operably slides when moved with the drive arm. The linear potentiometer generates a frequency output proportional to an insertion distance of the rod inside the elongate plunger tube.

Description

HIGH ACCURACY SYRINGE PUMPS

TECHNICAL FIELD

This disclosure relates generally to medical devices. More particularly, this disclosure relates to syringe pumps that provide relatively high accuracy, control, and safety by incorporation of advanced sensors, such as precise and accurate linear potentiometers.

BACKGROUND

In the field of medication delivery devices including so-called "syringe pumps," typically a pre-filled medication syringe is mechanically driven under microprocessor control to deliver a prescribed amount or dose of a drug, fluid, fluid-like substance, or medicament (hereinafter, collectively, an "infusate") at a controlled rate to a patient through an infusion line or tubing that is fluidly connected to the syringe. Syringe pumps typically include a motor that rotates a lead screw. The lead screw in turn activates a plunger driver which forwardly pushes a plunger within a barrel of the syringe that has been removably installed in the pump. Pushing the plunger forward thus forces the infusate outwardly from the syringe, into the infusion line or tubing, and to the patient - typically, intravenously. Examples of syringe pumps are disclosed in U.S. Pat. No. 4,978,335 titled "Infusion Pump with Bar Code Input to Computer," U.S. Pat. No. 8,182,461 titled "Syringe Pump Rapid Occlusion Detection System," and U.S. Pat. No. 8,209,060 titled "Updating Syringe Profiles for a Syringe Pump." As used throughout this disclosure, the term "syringe pump" is intended to generally pertain to any device which acts on a syringe to controllably force infusates outwardly therefrom.

Syringe pumps are used to control the delivery of infusates to a patient that include, but are not limited to: therapeutic agents; nutrients; drugs; medicaments such as antibiotics, blood clotting agents, and analgesics; and other fluids. The devices can be used to introduce the infusates into patients' bodies utilizing any of several routes such as, for example, intravenously, subcutaneously, arterially, or epidurally.

It would therefore be useful and advantageous to provide devices and methods for syringe pumps that provide relatively high accuracy, control, and safety as compared to known pump devices and methods.

SUMMARY

This disclosure describes novel and inventive devices and methods for syringe pumps that provide relatively high accuracy, control, and safety in delivering infusates to patients. In the context of syringe pumps, infusate delivery from a syringe is typically directly proportional to movement of the plunger head of the syringe. Accordingly, embodiments described herein disclose devices and methods which measure and control plunger head movement of a syringe with greatly increased accuracy as compared to previously known pump devices and methods; and in doing so, they provide significantly enhanced capabilities related to pump control, use, and safety.

Embodiments can include a high accuracy syringe pump, including a pump housing and a drive assembly. The drive assembly can slideably move horizontally to extend and retract with respect to the pump housing and includes a plunger driver head, a drive arm, a lead screw, a motor, and a linear potentiometer. The plunger driver head has a surface structure that selectively and forcibly urges against a thumb press of a plunger of a syringe along a first central longitudinal axis when the syringe is installed in the syringe pump. The syringe is configured to contain an infusate and includes a barrel and the aforementioned plunger configured to slidably reside within the barrel and that together define the first central longitudinal axis. The drive arm includes an elongate plunger tube having a second longitudinal axis that is generally parallel to the first central longitudinal axis. The drive arm is coupled to the plunger driver head such that movement of the elongate plunger tube corresponds with generally equal and parallel movement of the plunger of the syringe along the first central longitudinal axis. The lead screw is operatively coupled to the drive arm and the motor is operatively coupled to the lead screw to govern movement of the lead screw and, consequently, the drive arm when the pump is operating to dispense an infusate from the syringe. Further, the linear potentiometer includes a double coil wound non-conductive rod generally in alignment with the second longitudinal axis and around which the elongate plunger tube operably slides when moved with the drive arm. The linear potentiometer generates a frequency output proportional to an insertion distance of the rod inside the elongate plunger tube.

Embodiments can also include a high accuracy syringe pump having a pump housing, a drive assembly, a display, and a diagnostic tool. The drive assembly can slideably move horizontally to extend and retract with respect to the pump housing and includes a plunger driver head, a drive arm, a linear potentiometer, and a motor. The plunger driver head selectively urges against a thumb press of a plunger of a syringe when the syringe is installed in the syringe pump and the syringe is configured to contain an infusate and includes a barrel and the aforementioned plunger that is configured to slidably reside within the barrel. The drive arm is coupled to the plunger driver head, including a metal plunger tube, such that a distance moved by the plunger driver head against the plunger of the syringe is equivalent to the distance moved by the metal plunger tube. The linear potentiometer includes a coil wound non-conductive rod located partially within the metal plunger tube. The linear potentiometer generates a frequency output proportional to an insertion distance of the rod inside the metal plunger tube. The motor is operatively coupled to drive the plunger driver head. The display provides infusate delivery information and controls for the syringe pump. The diagnostic tool evaluates operation of the drive assembly based on data from the linear potentiometer and the motor.

Another embodiment can include a method of accurately delivering a desired quantity of infusate from a syringe pump. The method includes providing a syringe pump that includes a pump housing and a drive assembly that can slideably move horizontally to extend and retract with respect to the pump housing. The drive assembly includes a plunger driver head, a drive arm, a lead screw, a motor and a linear potentiometer. The plunger driver head has a surface structure that selectively and forcibly urges against a thumb press of a plunger of a syringe along a first central longitudinal axis when the syringe is installed in the syringe pump, wherein the syringe is configured to contain an infusate and includes a barrel and the aforementioned plunger configured to slidably reside within the barrel and that together that define the first central longitudinal axis. The drive arm includes an elongate plunger tube having a second longitudinal axis that is parallel to the first central longitudinal axis. The drive arm is coupled to the plunger driver head such that movement of the elongate plunger tube corresponds with generally equal and parallel movement of the plunger of the syringe along the first central longitudinal axis. The lead screw is operatively coupled to the drive arm and the motor is operatively coupled to the lead screw to govern movement of the lead screw and, consequently, the drive arm when the pump is operating to dispense an infusate from the syringe. Further, the linear potentiometer includes a double coil wound non-conductive rod generally in alignment with the second longitudinal axis and around which the elongate plunger tube operably slides when moved with the drive arm. The linear potentiometer generates a frequency output proportional to an insertion distance of the rod inside the elongate plunger tube. The method further includes receiving the syringe in the syringe pump filled with a total volume of infusate. The method also includes characterizing the syringe including determining the total volume of infusate contained in the syringe. The method further includes characterizing the syringe including determining a volume of infusate that the syringe delivers per distance of plunger driver travel. The method can include receiving a first frequency output from the linear potentiometer corresponding to an initial position of the plunger of the syringe and determining a second frequency output associated with a distance of plunger travel necessary to infuse a particular quantity of infusate from the syringe. Further, the method can include receiving and monitoring frequency outputs from the linear potentiometer and delivering the infusate from the syringe according to a set of infusate delivery profile instructions until the second frequency output is received.

BRIEF DESCRIPTION OF THE DRAWINGS

Devices for, and methods of, syringe characterization are illustrated by way of example and not limitation in the figures of the accompanying drawings in which:

Figure 1 is a front perspective view of a syringe pump, according to an embodiment. Figure 2 is a rear perspective view of the syringe pump of Figure 1 according to an embodiment, permitting observation of interior components of a drive assembly that are generally obstructed by a housing of the syringe pump.

Figure 3 is a partial perspective view of a syringe pump drive assembly, according to an embodiment.

Figure 4 is a partial perspective view of a syringe pump drive assembly, according to an embodiment.

Figure 5 is a partial side view of a syringe pump drive assembly, according to an embodiment.

Figure 6 is an example of a linear potentiometer for use in a syringe pump drive assembly, according to an embodiment

Figure 7 is a flow chart of a method of accurate infusate delivery from a syringe pump, according to an embodiment.

DETAILED DESCRIPTION

Devices and methods described in greater detail by way of examples herein provide accurate control and correspondingly precise measurement of syringe pump infusate delivery movement through novel and inventive syringe pump arrangements incorporating advanced linear potentiometers and software. Such functionality can provide numerous abilities and advances not contemplated by existing syringe pump devices, as will be described by example herein.

In an example of an embodiment of a device for, and method of, accurate infusate delivery from a syringe pump, the aforementioned functionality is achieved by way of a syringe pump that includes a drive assembly, or "drive train", having a configuration enabling a highly accurate linear potentiometer and corresponding capabilities. Embodiments of this arrangement contemplate enhanced pump control and assessment, such as advanced infusate delivery and drive assembly diagnostics, that would not be readily achieved without the type of device arrangement and methods described herein.

In general, accuracy and control of infusate delivery are two desired aspects of effective operation for a syringe pump. Based on the fundamental characteristics of its design, a syringe is intended to provide infusate delivery that is generally directly proportional to the movement of an associated thumb press of a plunger, and thus the plunger, of the syringe. Accordingly, the syringe pump embodiments described herein, that can accurately measure and control movement of the plunger thumb press, can provide significantly more capabilities in terms of accuracy and control of a delivery profile and patient treatment generally. Moreover, features providing enhanced safety are made possible as well.

Figure 1 illustrates an example of an embodiment of a syringe pump 10 that is configured for accurate infusate control. Syringe pump 10 includes a housing 12 configured to receive a syringe 20 having a barrel 30 and a plunger 40 with a plunger tip 50 and a thumb press 60. Housing 12 shown is largely box shaped and provides structure to surround interior drive components of pump 10 and for externally receiving syringe 20. Syringe 20 is of a detectable size or diameter. Examples of syringe pump size detection and characterization are discussed in PCT Patent Pub. WO2014/089008 A2 titled "Syringe Characterization", which is hereby incorporated by reference. Syringe 20 is configured to contain a medication or other infusate to be delivered to a patient from syringe pump 10. Specifically, syringe pump 10 is configured to act on syringe 20 by way of a plunger driver head 70 being selectively and forcibly urged against thumb press 60 of plunger 40. Movement of plunger driver head 70 generally is controlled by a drive assembly 100 which permits slideable movement thereof horizontally to extend and retract with respect to housing 12. Barrel 30 and plunger 40 together define a central longitudinal axis 80 of syringe 20.

Syringe pump 10 also includes software (not explicitly illustrated) and display means that can, in an embodiment, be provided by way of suitable computing components (not explicitly illustrated) and a display screen or graphical user interface 90 located on, for example in Figure 1, a front portion of syringe pump 10. Using interface 90, users can effectively observe and control, and otherwise interact with programming and operation of, pump 10. In some embodiments, such pump programming operations can interact with a infusate delivery "engine" that determines a quantity of infusate being delivered from syringe 20, among other pump information and parameters, based in part on sensor data, as from a distance sensor, for example.

For purposes of this disclosure, the term "engine" can be defined as a real-world device, component, or arrangement of components implemented using hardware, or as a combination of hardware and software, such as by a microprocessor system and a set of particular program instructions that adapt or prompt the engine to implement the particular functionality, which (while being executed) transform a microprocessor system into a special-purpose device. A engine can also be implemented as a combination of the two, with certain functions facilitated by hardware alone, and other functions facilitated by a combination of software-controlled hardware. In certain implementations, at least a portion, and in some cases, all, of a engine can include the processor(s) of one or more computers that execute an operating system, system programs, and application programs, while also implementing the engine using multitasking, multithreading, distributed (e.g., cluster, peer-peer, cloud, etc.) processing where appropriate, or other such techniques. In addition, an engine can itself be composed of more than one sub- engines, each of which can be regarded as an engine, whether collectively or individually.

Referring now to Figures 2-5, and with continued reference to Figure 1, therein illustrated are various partial views of embodiments of a drive assembly 100 of syringe pump 10. Drive assembly 100 of pump 10 includes a plunger driver head 70, a linear potentiometer 110, plunger tube 120, lead screw 130, lead screw housing 140, gears 150, and motor 160. In general, drive assembly 100 is supported between a first support plate 170 and a second support plate 180, respectively located at opposite sides of housing 12. Extending through second support plate 180 is a plunger head drive arm 190. Plunger head drive arm 190 generally refers to a combination of elongate components extending across drive assembly 100 and can include plunger tube 120 and a lead screw housing 140, for example. Plunger tube 120 can comprise a hollow tube, extending across a top portion of plunger head drive arm 190, but may also be integrally formed with lead screw housing 140 in some embodiments as well.

Plunger driver head 70 is shown in Figure 3 as a plate or generally oblong disc-like component that is attached near one edge of its surface to an end of plunger head drive arm 190. With reference also to Figure 1, an opposite edge of plunger driver head 70 provides a surface structure 200 (as identified in Figure 3) to selectively engage and forcibly urge thumb press 60 of syringe 20 along longitudinal axis 80. This surface structure 200 can simply include a generally flat surface of plunger driver head 70 or can include various projections or recessed areas for providing engagement with thumb press 60 when syringe 20 is installed in pump 10. Accordingly, plunger driver head 70 is able to controllably push thumb press 60, and thus plunger 40 within barrel 30 of syringe 20, in response to turning by lead screw 130 that consequently draw plunger driver head 70 toward housing 10. Turning of lead screw 130, accordingly, is controlled by rotational motion provided by motor 160 which drives gears 150 that engage and enable rotational movement of lead screw 130. As shown most visibly in Figures 2-4, linear potentiometer 110 extends between first support plate 170 and plunger tube 120. Specifically in this example embodiment, linear potentiometer 110 is anchored to first support plate 170 at an end thereof and extends into the aperture opening 202 of plunger tube 120 of plunger head drive arm 190 at an opposite end. The elongate plunger tube 120 has a longitudinal axis 204 through its center that is generally parallel to longitudinal axis 80 (as shown in, e.g., Figure 2) and which is in alignment with a longitudinal axis of linear potentiometer 110. Further, linear potentiometer 110 is located in a substantially parallel orientation with central longitudinal axis 80 of syringe 20 when installed in syringe pump 10. Likewise in this example embodiment (as shown in, e.g., Figure 3), lead screw 130 and motor 160 are anchored to first support plate 170. Lead screw 130 is located in a substantially parallel orientation with central longitudinal axis 80 of syringe 20 and linear potentiometer 110 as well. Embodiments use a linear potentiometer 110 that is a very accurate type of linear potentiometer which is specifically integrated into a syringe pump 10.

In certain embodiments, the linear potentiometer 110 includes an inner wrapped coil which causes current to flow in a clockwise direction and an outer wrapped coil which causes current to flow in a counterclockwise direction. For example, possible linear potentiometers that could be used in embodiments of the proposed syringe pumps include DIST (Distributed Impedance Sensor Technology) sensors and related technology manufactured by LRT Sensors, LLC. of Huntingdon Valley, PA. In such embodiments, as shown in Figure 6, linear potentiometer 110 can be a sensor that comprises a double coil 210 wound on a rounded non- conductive fiberglass rod 220. The wire is wound in a first coil as a helix having a large pitch. At the end of rod 220, the pitch is reversed and a second coil as a returning helix is laid over the first coil. An end of rod 220 comprises electronics 230 including a transistor connected to a resulting helical wire assembly from the first and second coils that produce a resonant circuit and oscillation. The opposite end of rod 220 comprises rod tip 232, which is the portion of rod 220 that is first concealed by plunger tube 120 during pump operation.

This arrangement results in two coils in series with one having a generally clockwise current flow and the other having a generally counterclockwise current flow. When energized, resulting magnetic fields of the coils are generally parallel to the sensor, but in opposite directions, and accordingly cancel out each other. Electric fields from the currents are generally perpendicular to rod 220 and accordingly are additive. This provides an electromagnetic field outside the coils that is largely electric. Consequently, the advantageous linear potentiometer 110 discussed requires no magnets or magnetic material in various embodiments. As a further advantageous result of its construction, potentiometer 110 is generally insensitive to external magnetic fields and may accordingly permit satisfactory operation in environments subject to high magnetic fields.

A frequency of the circuit is determined by inductance and capacitance of the helical wire assembly. In general, operating a circuit at its resonant frequency produces a very stable output. The inductance of the assembly is low and constant, due to relatively few turns of the first and second coils, but a ratio of capacitance to inductance is higher than in an inductive sensor and is based on an interaction of a strong electric field of the sensor with any nearby conductive surface. Accordingly, one way in which to cause capacitance and resonant frequency of the sensing element to change significantly is to cover the coil and rod with a conductive structure. In embodiments of syringe pump 10, the helical wire assembly and rod 220 are partially and slideably covered by elongate plunger tube 120 made of conductive material. Even one MHz change in resonant frequency can result when plunger tube 120 moves over potentiometer 110. Changes in frequency are linear with movement of plunger tube 120. These changes can be transmitted and converted to digital signals for further processing as desired.

Having an output that is a digital frequency rather than an output that is analog or a voltage provides advantages as well. Sensors with analog outputs are susceptible to noise, attenuations, and distortions. Accordingly, analog sensors may require system electronics to be near the sensor or utilize extensive correction software to correct for these errors. Unlike analog sensors, DIST sensors, or similar technologies, would allow high accuracies to be maintained as these sensors are generally not susceptible to such noise, attenuations and distortions.

A DIST sensor used as a linear potentiometer 1 10 is advantageous as it is an extremely simple device only requiring a single wire for power and transmission of information. Digital output frequency can be "piggybacked" or carried on or with DC power so that only one wire is required and the receiver can be located remotely. This wire provides great flexibility in locating signal analysis electronics based in part on its significant length of signal wire. In general, problems are minimized by only using one wire. Accordingly, a DIST sensor is a simple, economical and compact device that can help make accurate linear measurements with only a single wire for power and signal.

DIST sensors do not require use of extremely fine wire as in other sensor constructions and can instead use a heavy wire since it is generally designed to maximize capacitance. A more robust wire is advantageous as a heavy wire wound on a flexible rod can withstand extremely high levels of shock and vibration and overcomes these susceptibilities of other sensors.

DIST sensors can also provide a possibility of easy modification for multiple redundancy. In certain embodiments, it may be desirable to deploy multiple sensors making identical measurements of the same motion. In a dual redundant system, when both sensors produce the same result, the data are assumed to be accurate. In a triple redundant system, when at least two of the sensors agree, the system can continue operation based on the values of the two sensors, and the third can generally be ignored. In an embodiment the DIST sensor can make, for example, double or triple redundant measurements without any need for separate linkages and only a small increase in the physical size of the sensor. For a double redundant system, the nonconductive shaft of the sensor can be extended and a second coil wound on the extension. Accordingly, when there are two sensors on the same rod, a single conductive elongate plunger tube that extends over the rod serves two functions. As the conductive, elongate plunger tube uncovers the first coil, it simultaneously covers the second coil. If space is not readily available or if the system is otherwise constrained or limited in space or volume, electronics for the second coil could be combined with, for example, electronics 230 for the first coil using a hollow nonconductive rod and running a shielded wire through the rod. Accordingly, the redundant system requires no additional space and both coils are measuring the same moving surface with no requirement for mechanical alignment or attachments. In a suitably constructed embodiment, a triple redundant system can be achieved by adding a third coil. Specifically, this coil can be wound on a larger diameter hollow non conductive tube that fits over the moving conductive surface. The outer coil will also resonate in response to the conductive surface moving on its inner surface. Accordingly, three separate measurements on the same moving surface are achieved and all three coils can be calibrated at the same time. Although the diameter of the sensor increases somewhat, the length remains unchanged with this design.

Figures 4 and 5 further show partial views of embodiments of syringe pump drive assembly 100 in which a structural relationship and arrangement of components permitting effective use of a type of linear potentiometer such as potentiometer 1 10 can be more fully understood. Specifically, in these embodiments, linear potentiometer 110 and plunger tube 120 are axially aligned with one another. Further, linear potentiometer 110 and plunger tube 120 are vertically located above lead screw 130. Accordingly, respective axes of rod 220 of linear potentiometer 110, elongate plunger tube 120, and lead screw 130 are generally parallel to each other and project outwardly from the generally flat surface of first support plate 170 in a generally perpendicular orientation.

Accordingly, linear potentiometer 110 can be a sensor that generates a frequency output that is proportional to a distance of insertion 236 of the sensor (i.e. rod 220) inside a metal or aluminum tubing such as plunger tube 120. This insertion distance 236 of the sensor can be understood to represent the covered length of rod 220 extending between the aperture opening 202 of the plunger tube 120 and the location of rod tip 232 within the plunger tube 120. See Figure 3, for example. This insertion distance 236 of the sensor (i.e. rod 220) determines frequency output. Accordingly, as a location of plunger tube 120 - relative to, for example, plate 170 - changes when it slidingly moves with drive arm 190, the frequency output also changes. This frequency can be measured to within one Hz in various embodiments. A corresponding change in distance for plunger movement for such a one Hz measurement would be roughly one micron in certain embodiments. Such a level of accuracy allows for detection of displacement of within one micron, whereas previously known syringe pumps may be capable of a resolution of within only about 500 microns.

In general, therefore, it is to be understood that the linear potentiometer and associated electronics and processing hardware/software of an infusate delivery engine, as described by example or otherwise contemplated herein for syringe pump 10, enable determination of specific positions of a plunger relative to a barrel of a syringe installed in pump 10. In certain embodiments, linear potentiometers may include position sensing technology similar to that described in U.S. Pat. No. 7,216,054 to Pchelnikov et al. or U.S. Pat. No. 8,692,541 to Nyce et al., the disclosures of which are hereby incorporated by reference. Accordingly, linear potentiometer 110, such as embodied in an aforementioned DIST sensor, is integrated into an architecture of drive assembly 100 of syringe pump 10. The architecture must be constructed to support an arrangement in which frequency output is proportional to a displacement of linear potentiometer 110 inside plunger tube 120. As depicted in Figures 2-5, some embodiments are accordingly constructed such that lead screw 130 that drives movement of thumb press 60, and consequently, plunger 40, are located in a generally parallel arrangement such that movement of plunger 40 will directly correspond to movement of potentiometer 110 and result in detection of resulting frequency output signals. Accordingly, movement of plunger 40 along longitudinal axis 80 moves plunger tube 120 an approximately equal distance in the same direction. Further, linear potentiometer 110 is located such that it is firmly coupled to first support plate 170 at its end. Lead screw 130 is coupled to a stepper motor 160 via gears 150 that may be housed in a gear box (not shown). Lead screw 130 drives plunger tube 120 in relation to linear potentiometer 110 as well as lead screw housing 140. Both plunger tube 120 and lead screw housing 140 comprise components of plunger head drive arm 190. Therefore, motor 160 is operatively coupled to lead screw 130 to govern movement of lead screw 130 and, therefore also, drive arm 190.

Consequently, infusate delivery and determination occurs when plunger head drive arm 190 acts to advance plunger 40 within syringe 20. Drive arm 190 causes linear potentiometer 110 to sense a present position of drive arm 190, by measuring frequency output as previously described. With a position of drive arm 190 thus known, a location of plunger tip 50 is determined and the software can accurately provide valuable information on delivery of infusate from the syringe by the pump.

Accordingly, by using novel and inventive subject matter hereof, as described by example or otherwise contemplated herein, resolution and accuracy of determination of movement and location of plunger tube 120 and thus plunger head drive arm 190 is increased, which in turn, ultimately controls the accuracy and capability of syringe pump 10. Also, the novel and inventive subject matter hereof provides an architecture in which a relatively solid or stable link between rotary position of stepper motor 160 and linear distance of plunger 40 travel is established. Previously known syringe pumps generally have very limited ability to accurately link these two parameters. For example, certain previously known rotary encoders on syringe pump stepper motors only resolve ninety degrees of rotation with an optical sensor. Likewise, certain previously known position sensors can only resolve five hundred microns of plunger travel.

Unlike previously known devices, the novel and inventive subject matter hereof provides an increased capability to determine rotary motion with addition of a high accuracy rotary encoder (not shown). Such a high accuracy rotary encoder would be capable of resolving 0.25 degrees (1440 counts per revolution) of stepper motor angle. The addition of such a high accuracy rotary encoder as well as a high accuracy linear potentiometer 110 would enable a user to closely match the rotary and linear motion of drive assembly 100 of syringe pump 10. Such a system could result in a resolution increase of roughly four hundred times that of previously known devices for both rotary and linear motion.

In certain embodiments, implementation of novel and inventive subject matter hereof will result in increased accuracy of infusate delivery based on increased accuracy of measurement of travel of plunger tube 120 and thus plunger head drive arm 190. This accuracy is made possible by accumulation of precise and reliable measurements generally, and specifically by increased determination of movements of plunger head drive arm 190 as infusate delivery is directly proportional to movement of thumb press 60 of plunger 40 of syringe 20 in pump 10.

Further, in some embodiments, implementation of novel and inventive subject matter hereof will result in increased control of infusate delivery based on a resulting ability to provide programmed linear distance movements within drive assembly 100 of pump 10. In some embodiments, implementation of novel and inventive subject matter hereof will result in reduced start up time based on monitoring movement of plunger tube 120 and thus plunger head drive arm 190. Due to a drive time dependent nature of start up of pump 10, an ability to quickly resolve or determine position of plunger 40 of syringe 20 in pump 10 can efficiently accelerate start up. Similarly, some embodiments will enable an increased ability to determine an amount of infusate remaining in a syringe at an end of travel or full displacement of plunger 40. With less accurate pumps, small remaining quantities of infusate in syringes in those pumps can be difficult to establish and definitively determine. This can result in waste if syringes are replaced earlier than necessary. This can be particularly important when the infusate is costly or not readily available as being difficult to supply or replace. This can also potentially result in deleterious under-deliveries of infusates to patients.

In certain embodiments, syringe pump 10 includes additional features that provide increased safety to patients and users. For example, syringe pump 10 may be equipped with tools or components allowing users to diagnose health (or mechanical integrity) of drive assembly 100 of pump 10. This may be a diagnostic tool of the infusate delivery engine that evaluates operation, performance, and health of drive assembly 100 based on data from linear potentiometer 110 and motor 160. Namely, the increased resolution and relationship of stepper motor rotation and movement and quantity of infusate delivery by syringe pump 10 enables operation of drive assembly 100 to be evaluated by pump 10 itself. As a safety matter, a drive assembly 100 that proves to be inconsistent or otherwise unreliable can be quickly identified and replaced. This type of error is often difficult to detect in most previously known infusion pumps. This diagnostic ability provides a useful and desirable safety capability that is important to ensuring patients receive appropriate care.

In some embodiments, the health of the drive assembly 100 can be "mapped" or "calibrated" by using the very accurate linear potentiometer 110 and a high-resolution rotary encoder. Along the length of drive arm 190 travel, typically about 3 to 4 inches of linear travel, each change in linear distance can be mapped by a corresponding change in rotary turns of the encoder. This mapping results in a graphical or digital table that may be used to diagnose "bad" linear motion of the drive assembly 100. For example, if the pump 10 is dropped or otherwise subject to an unusual or significant external force, and a certain location along the longitudinal axis 204 of travel has "poor" correlation between the linear travel and rotary motion, it is likely that some damage has occurred to the mechanical system. This damage can be in the form of damage to the lead-screw 130, gears 150, plunger tube 120 (i.e. bent), etc. These anomalies would be found if there was a "baseline" correlation established between very accurate linear position and high-resolution rotary encoding. Furthermore, display screen or graphical user interface 90 can provide infusate delivery information and controls for syringe pump 10. Interface 90 can comprise, for example, suitable touch screen or LCD technology. Examples of touch screen devices generally are disclosed in U.S. Pat. Applic. Pub. Nos. 2006/0097991 titled "Multipoint Touchscreen" and in 2011/0193788 titled "Graphical Objects that Respond to Touch or Motion Input." Examples of novel and inventive infusion pump technologies employing touch screen devices are disclosed in: U.S. Pat. No. 5,485,408 titled "Pump Simulation Apparatus"; U.S. Pat. Applic. Pub. No. 2009/0270810 titled "Security Features for a Medical Infusion Pump."

It is also to be appreciated and understood that types, components, dimensions, fabrication processes, and other particulars and parameters of aforedescribed example embodiments can be substituted for others as desired, or that accessories can be added thereto.

Now referring to Figure 7, an example of operation of a syringe pump system including a precise and accurate linear potentiometer, as aforedescribed, is illustrated. In Figure 7, an embodiment described by a flow chart of a method 300 of accurate infusate delivery from a syringe pump is disclosed for delivering a desired amount of infusate. First, at 310 a syringe pump such as pump 10 is provided that includes a pump housing 12 and a drive assembly 100 that slideably extends and retracts with respect to the pump housing 12. The drive assembly 100 includes a plunger driver head 70, a drive arm 190, a lead screw 130, a motor 160 and a linear potentiometer 130. Further, the method at 310 includes receiving syringe 20 in syringe pump 10 filled with a total volume of an infusate.

At 320, the method also includes characterizing syringe 20 that, accordingly, includes determining the total volume of the infusate contained in syringe 20. This characterization can be performed in a variety of ways as discussed above. At 330 the method further includes characterizing syringe 20 including determining a volume of infusate that syringe 20 delivers per distance of plunger driver travel or displacement of plunger 40 in barrel 30 of syringe 20, caused by operation of pump 10. Acquiring this data could allow for, or could supplement or enhance, various infusate delivery calculations and options such as are disclosed in, for example, WIPO application no. PCT/US2015/13049 filed on 27 January, 2015, titled "Pump Startup Algorithms and Related Systems and Methods", WIPO application no. PCT/US2014/63683 filed on 03 November, 2014, titled "Pump Delivery Calculation Systems and Methods", and US provisional application no. 62/140,168 filed on 30 March, 2015, titled "Within-Time Infusion Modes for Infusion Pumps", which are each hereby incorporated herein by reference thereto. Copies of each of these patent applications are included in an appendix to this application. At 340 the method can include receiving a first frequency output from linear potentiometer 110 corresponding to an initial position of plunger 40 of syringe 20 and, at 350, determining a second frequency output associated with a distance of travel or displacement of plunger 40 that is necessary to infuse a particular quantity of infusate. Further, at 350, the method can include receiving and monitoring frequency outputs from linear potentiometer 110 and, at 360, delivering the infusate from syringe 20 according to a set of infusate delivery profile instructions until the second frequency output is received. Other infusate delivery operations are possible as well.

Irrespective of a particular embodiment, it is to be appreciated and understood that in embodiments of devices, systems, and methods for syringe pumps that provide relatively high accuracy, control, and safety, as disclosed by example or otherwise contemplated herein, the linear potentiometer, and the software together function to provide more accurate and precise determination of a volume of infusate that is delivered from the syringe based on a linear displacement or travel of the syringe's plunger.

Regardless of particular components or modes of action, it is to be appreciated and understood that devices, systems, and methods for syringe pumps that provide relatively high accuracy, control, and safety, such as have been described by example or otherwise contemplated herein, can be able, for a particular linear displacement or travel of the syringe's plunger, determine with increased accuracy and precision how much infusate is ultimately delivered to a patient, among other information.

While devices, systems, and methods for syringe pumps that provide relatively high accuracy, control, and safety have been particularly shown and described with reference to the accompanying figures and specification, it should be understood, however, that other modifications thereto are of course possible; and all are intended to be within the true spirit and scope of novel and inventive devices, systems, and methods described herein. Thus, configurations and components of various features could be modified or altered depending upon particular embodiments. For example, sequencing of various method steps described by example or otherwise contemplated herein could be re-ordered as may be desired in a particular embodiment.

It is also to be understood in general that any suitable alternatives may be employed to provide novel and inventive devices, systems, and methods for syringe pumps that provide relatively high accuracy, control, and safety that have been described by example or are otherwise contemplated herein. Compositions, sizes, and strengths of various aforementioned components of devices, systems, and methods for syringe pumps that provide relatively high accuracy, control, and safety that have been described by example or are otherwise contemplated herein are all a matter of technical choice depending upon intended uses thereof.

Accordingly, these and other various changes or modifications in form and detail may also be made, without departing from the true spirit and scope of devices, systems, and methods for syringe pumps that provide relatively high accuracy, control, and safety, that may be defined by the appended claims.

Claims

CLAIMS What is claimed is:

1. A high accuracy syringe pump, comprising:

a pump housing;

a drive assembly that slideably extends and retracts with respect to the pump housing, including:

a plunger driver head having a surface structure that selectively urges against a syringe along a first central longitudinal axis when the syringe is installed in the syringe pump, wherein the syringe is configured to contain an infusate and includes a barrel and a plunger that define the first central longitudinal axis;

a drive arm, including an elongate plunger tube having a second longitudinal axis that is generally parallel to the first central longitudinal axis, coupled to the plunger driver head such that movement of the elongate plunger tube corresponds with generally equal and parallel movement of the plunger of the syringe along the first central longitudinal axis;

a lead screw operatively coupled to the drive arm;

a motor operatively coupled to the lead screw to govern movement of the lead screw and the drive arm; and

a linear potentiometer including a double coil wound non-conductive rod generally in alignment with the second longitudinal axis and around which the elongate plunger tube operably slides when moved with the drive arm, the linear potentiometer generating a frequency output proportional to an insertion distance of the rod inside the elongate plunger tube.

2. The high accuracy syringe pump of claim 1, wherein the syringe pump includes a display that provides infusate delivery information and controls.

3. The high accuracy syringe pump of claim 1, wherein the syringe pump include a infusate delivery engine that determines a quantity of the infusate being delivered from the syringe based in part on data from the linear potentiometer.

4. The high accuracy syringe pump of claim 3, wherein the infusate delivery engine includes a diagnostic tool that evaluates performance of the drive assembly of the syringe pump.

5. The high accuracy syringe pump of claim 1, wherein the frequency output is measured to within one Hz by the linear potentiometer.

6. The high accuracy syringe pump of claim 1, wherein one micron movements of the plunger are detected by the syringe pump.

7. The high accuracy syringe pump of claim 1, wherein the double coil wound non- conductive rod is rounded and made of fiberglass.

8. The high accuracy syringe pump of claim 1, wherein the elongate plunger tube is made of metal or aluminum.

9. The high accuracy syringe pump of claim 1, wherein motor is a stepper motor equipped with a high accuracy rotary encoder.

10. A high accuracy syringe pump, comprising:

a pump housing;

a plunger driver head that selectively urges a syringe when the syringe is installed in the syringe pump, wherein the syringe is configured to contain an infusate and includes a barrel and a plunger;

a drive arm coupled to the plunger driver head, including a metal plunger tube, such that a distance moved by the plunger driver head against the plunger of the syringe is equivalent to the distance moved by the metal plunger tube;

a linear potentiometer including a coil wound non-conductive rod located partially within the metal plunger tube, the linear potentiometer generating a frequency output proportional to an insertion distance of the rod inside the metal plunger tube; and

a motor operatively coupled to drive the plunger driver head; a display that provides infusate delivery information and controls for the syringe pump; and

a diagnostic tool that evaluates operation of the drive assembly based on data from the linear potentiometer and the motor.

11. The high accuracy syringe pump of claim 10, wherein the coil wound non-conductive rod is double coil wound.

12. The high accuracy syringe pump of claim 10, wherein the syringe pump include an infusate delivery engine that determines a quantity of the infusate being delivered from the syringe based in part on data from the linear potentiometer.

13. The high accuracy syringe pump of claim 10, wherein the frequency output is measured to within one Hz by the linear potentiometer.

14. The high accuracy syringe pump of claim 10, wherein movements of the plunger of one micron are detected by the syringe pump.

15. The high accuracy syringe pump of claim 10, wherein the coil wound non-conductive rod is rounded and made of fiberglass.

16. The high accuracy syringe pump of claim 10, wherein motor is a stepper motor equipped with a high accuracy rotary encoder.

17. A method of accurately delivering a desired quantity of infusate from a syringe pump, comprising:

providing a syringe pump, including:

a pump housing;

a drive arm, including an elongate plunger tube having a second longitudinal axis that is parallel to the first central longitudinal axis, coupled to the plunger driver head such that movement of the elongate plunger tube corresponds with generally equal and parallel movement of the plunger of the syringe along the first central longitudinal axis;

a lead screw operatively coupled to the drive arm;

a linear potentiometer including a double coil wound non-conductive rod generally in alignment with the second longitudinal axis and around which the elongate plunger tube operably slides when moved with the drive arm, the linear potentiometer generating a frequency output proportional to an insertion distance of the rod inside the elongate plunger tube; and

receiving the syringe in the syringe pump filled with a total volume of infusate;

characterizing the syringe including determining the total volume of infusate contained in the syringe;

characterizing the syringe including determining a volume of infusate that the syringe delivers per distance of plunger driver travel;

receiving a first frequency output from the linear potentiometer corresponding to an initial position of the syringe;

determining a second frequency output associated with a distance of plunger travel necessary to infuse a particular quantity of infusate;

receiving and monitoring frequency outputs from the linear potentiometer; and delivering the infusate from the syringe according to a set of infusate delivery profile instructions until the second frequency output is received.

18. The apparatuses as described herein.

19. The components and systems described herein.

0. The methods described herein.

The individual steps and combinations of steps described herein.