GB2571954A

GB2571954A - Infusion systems and methods

Info

Publication number: GB2571954A
Application number: GB1804043.6A
Authority: GB
Inventors: Batliner Martin; Meboldt Mirko; Thorvaldsen Daniel
Original assignee: Onefusion AG
Current assignee: Onefusion AG
Priority date: 2018-03-14
Filing date: 2018-03-14
Publication date: 2019-09-18
Also published as: WO2019175836A1; GB201804043D0

Abstract

A syringe pump 210, comprising: a biasing mechanism 212 to press against a syringe plunger 142 of an infusion set 140 urging an infusate flow through an infusion tube 146; a flow control valve 216 to adjustably restrict the infusate flow; a flow rate sensor 218 to measure the infusate flow rate; and a controller 214 configured to receive one or more flow rate sensor 218 signals and to modulate the infusate flow rate by controlling flow control valve 216. Pump 212 may comprise a user interface 226 to input one or more infusate flow rate set points to controller 214, where controller 214 may be configured to modulate the infusate flow rate based on the infusate flow rate set point. Pump 212 may comprise a displacement sensor to detect the syringe plunger 142 position relative to a syringe barrel 144, where controller 214 may calibrate flow rate sensor 218 using a displacement sensor signal. Pump 212 may comprise a load sensor 318 to measure biasing mechanism 212 force against syringe plunger 142, where controller 214 may calibrate flow sensor 218 using a signal from load sensor 318. Flow control valve 216 may deform infusion tube 146 to differing extents.

Description

INFUSION SYSTEMS AND METHODS

TECHNICAL FIELD

The disclosure relates to systems and methods for controllably infusing a patient with a therapeutic medical fluid.

BACKGROUND

In some conventional perfusion systems, a container holding a perfusion liquid is positioned in a pump, such as a syringe pump. A perfusion conduit, or perfusion tube, is connected to the container. At the free end of the perfusion conduit is a perfusion needle which is inserted into a vein of the patient who is to receive the perfusion. In some cases, a plunger of the syringe is actuated by a motor of the syringe pump. By controlling the motor, the flow velocity of the perfusion liquid passing through the perfusion tube, and therefore the volume of perfusion liquid administered to the patient per time unit, can be controlled. The intended purpose of such a perfusion device is to meet the physiological needs of the patient. To accomplish that, the volume of perfusion liquid supplied to the patient per time unit is regulated by controlling the motor of the syringe pump assembly. However, such a system does not actually measure the flow rate of the perfusion liquid that the patient receives.

SUMMARY

This disclosure describes systems and methods for controllably infusing a patient with a therapeutic medical fluid. The systems described include, but are not limited to, infusion systems that are configured to be supported by a structure spaced apart from the patient. This disclosure also describes portable infusion systems that are configured to be worn or carried by a patient such that the patient is ambulatory while using the syringe pump.

In some implementations, the syringe pump systems described herein include a housing structure. Such a housing structure can be configured to receive an infusion set that is releasably coupleable with the housing structure.

In some implementations, the syringe pump systems described herein include a biasing mechanism arranged to press against a syringe plunger of the infusion set to urge an infusate within a syringe of the infusion set to flow through an infusion tube to the patient. In some cases, an infusion set includes other types of reservoirs (other than a syringe with a plunger). For example, in some cases a reservoir such as a carpule with a movable element can be included as part of an infusion set. It should be understood that the syringe pump systems described herein are adaptable to be used with non-syringe reservoirs such as, but not limited to, carpule reservoirs and other types of containers.

In some implementations, the syringe pump systems described herein include a flow control valve that is arranged to adjustably restrict the flow of the infusate in the infusion tube. The flow control valve may be configured to deform the infusion tube to differing extents by manipulating the infusion tube from the outside (e.g., by pressing on the outer wall of the infusion tube) while not being affixed to the infusion tube. Alternatively, or in addition, the flow control valve may comprise a flow control mechanism that is integrated into the infusion set, and that may be manipulated from the outside (by the syringe pump systems) in such a way that the flow is restricted to differing extents.

In some implementations, the syringe pump systems described herein include at least one measurement system that provides a signal proportional to the infusate flow rate, a signal indicative of the force between a syringe plunger and a biasing mechanism of the syringe pump, and/or a signal indicative of the displacement of the syringe plunger relative to the syringe barrel. Such a measurement system may include a flow rate sensor that provides a signal indicative of the infusate flow. In some embodiments, such a flow rate sensor may be integrated into the infusion tube, or integrated into a disposable part that can be releasably coupled into the infusion tube. Alternatively, or in addition, the flow rate sensor may be configured to abut against the infusion tube from the outside, and to not be fixed to the infusion tube. In some embodiments, the flow rate sensor may be fixed to the infusion tube.

In some implementations, the flow rate sensor includes at least one heating element. Such a flow rate sensor may also include one or more temperature sensors spaced apart from the heating element(s). For example, in some implementations the flow rate sensor includes a first temperature sensor, a second temperature sensor, and a heating element between the first and the second temperature sensors.

Alternatively, or in addition, to the flow rate sensor, the syringe pump systems described herein may include a load sensor configured and positioned to measure the force exerted by the biasing mechanism onto the syringe plunger.

Alternatively, or in addition, to the flow rate sensor, the syringe pump systems described herein may include a displacement sensor arranged to detect a position of the syringe plunger relative to the syringe barrel with which the syringe plunger is slidably coupled.

In some implementations of the syringe pump systems described herein, a biasing mechanism is included that may comprise a spring. Accordingly, the spring may function according to Hook’s Law as well as any other characteristics of springs. In some embodiments, a constant force spring can be used. In some other embodiments, the biasing mechanism may comprise a pneumatic cylinder. In some such embodiments, the pneumatic cylinder exerts force on the plunger by changing the gas pressure inside the pneumatic cylinder. In some such embodiments, the gas pressure inside the pneumatic cylinder is not actively changed, and the pneumatic cylinder exerts force on the plunger passively. In still other embodiments, the biasing mechanism may comprise a motor that is arranged to exert its force on the syringe plunger. This may, but not necessarily, be achieved also using a gear train and a drive system in conjunction with the motor.

In some implementations, the syringe pump systems described herein include a controller that is coupled to the housing, and in electric communication with other components of the syringe pump, e.g., the flow control valve and the measurement system. If the biasing mechanism is a motor, the controller is in electric communication with the motor. The controller may receive one or more signals indicative of the infusate flow rate measured by the measurement system of the syringe pump, and may modulate the infusate flow rate by controlling the flow control valve to adjustably restrict the flow of the infusate in the infusion tube. The controller may be configured to modulate the infusate flow rate based on an infusate flow rate set point entered via a user interface of the syringe pump. Alternatively, or in addition, the infusate flow rate set point can be translated into a load trajectory, which may be constant or may follow desired characteristics. The controller can be configured to modulate the flow control valve in such way that the load signal follows the load trajectory. Alternatively, or in addition, the controller can calibrate one or more signals of the measurement system (e.g., a flow rate sensor) based on another signal of the measurement system (e.g., a load sensor, displacement sensor, etc.), and can then modulate the flow control valve based on the calibrated signal.

In some implementations, the syringe pump systems described herein include a user interface. Among other things, the controller can be configured to receive one or more signals indicative of an infusate flow rate set point input via the user interface.

Before starting an infusion, a prefilled syringe, with the infusion tube attached, is inserted into the syringe pump. Once the installation is completed, the user may set a flow rate to start the infusion. In some embodiments, the flow control valve initially fully restricts the infusion tube so that no infusate is transported through the infusion tube. The syringe assembly (e.g., the syringe barrel, the contained liquid, and the syringe plunger) tends to exhibit a compliance (e.g., deflection, expansion, flexure, compressibility, etc.) when a force is exerted onto the syringe plunger by the biasing mechanism of the syringe pump. This means that when a force is exerted on the assembly in longitudinal direction that the assembly is being compressed. Similarly, the mechanical assembly of the syringe pump (including, for example, the parts of the biasing mechanism) can exhibit a compliance (e.g., mechanical backlash, deflection, compressibility, flexure, etc.) when force is exerted by the syringe pump to cause the infusate to flow.

While the flow control valve is still fully restricting the infusion tube, the biasing mechanism can be actuated to exert force onto the syringe plunger. In that way, the compliance of both the syringe assembly and the mechanical assembly of the syringe pump can occur prior to any flow of the infusate such that the effects of the compliance on the flow rate are suppressed. The flow control valve then is opened (based on a signal from the controller of the syringe pump) to reduce restriction of the infusion tube so that the infusion fluid can move through the tube to the patient. The flow control valve is then modulated by the controller, based on one or more signals of the measurement system (e.g., the flow rate sensor and/or the load sensor). The syringe plunger, which is under pre-tension from the biasing mechanism, now slides relatively to the barrel to push the infusion liquid out of the syringe into the infusion tube towards the patient.

Over the course of the infusion the syringe pump controller modulates the flow control valve based on the signal of the measurement system to attain the infusion rate set point, or to follow a trajectory that is known to the controller, and that may have been determined or calculated by the controller. The syringe plunger, which is under pre-tension from the biasing mechanism slides relatively to the syringe barrel to push the liquid out of the syringe into the infusion tube until the syringe plunger reaches the end of the barrel once the infusion reaches its end.

In embodiments in which the biasing mechanism comprises a spring, the force on the plunger is either kept constant, (with a constant force spring) or changes according to the spring characteristic, but is designed to stay above a force threshold that is high enough to suppress the compliance of the syringe assembly and exert enough force to urge the infusate out of the infusion set. In embodiments in which the biasing mechanism comprises a motor, the syringe pump controller actuates the motor to either maintain the force on the plunger or to follow a trajectory that ensures that the force between biasing mechanism and syringe plunger is high enough to suppress the compliance of the syringe assembly and enough to force infusate out of the infusion set.

In some implementations, the flow rate sensor includes a first temperature sensor, a second temperature sensor, and a heating element positioned between the first and the second temperature sensor. The flow sensor outputs a voltage signal that corresponds to a difference in temperature detected by the first and second temperature sensor (which corresponds to the infusate flow rate). In some embodiments, the controller modulates the flow control valve so that the flow sensor signal is controlled to be at a flow rate set point (which may correspond to a set voltage).

When the measurement system comprises a flow sensor, the flow sensor outputs a voltage signal corresponding to the infusate flow rate. If the flow sensor is configured to internally convert the voltage based on an internally stored calibration to a flow signal in ml/h and provides said signal to the controller, the flow control valve is modulated by the controller so that the flow signal follows the flow rate set point or a predefined flow rate set trajectory.

When the measurement system comprises a load sensor, the force between the syringe plunger and the biasing mechanism has a characteristic trajectory over the course of a full infusion. When the biasing mechanism comprises a spring, the force between the syringe plunger and the biasing mechanism can characteristically correspond to Hook’s law. When the volume in the syringe becomes smaller, the spring force may become proportionately smaller. This known characteristic, in combination with the information of the size of the syringe and the set infusate flow rate, allows the creation of a set load trajectory (which can correspond to a set infusate flow rate). When the controller modulates the flow control valve so that the load signal follows the set load trajectory, an infusate flow rate can be maintained.

In another implementation, one signal of the measurement system indicative of the flow may be used to calibrate another signal of the measurement system. The flow rate sensor may provide a voltage that changes proportionally to the infusate flow rate. A displacement sensor may provide the distance travelled by the syringe plunger relatively to the syringe barrel. Using the displacement sensor output signal(s) in combination with information about the syringe cross-sectional area, the controller can calculate the absolute infusate flow rate. This absolute infusate flow rate can be used to calibrate the voltage of the flow sensor so that the flow sensor provides accurate readings of the infusate flow rate. The displacement sensor may have a low resolution, and as such may only provide a signal update every now and then, whereas the flow rate sensor continuously provides a voltage that can be used by the controller to modulate the flow control valve. The displacement measurement may be provided by a dedicated displacement sensor. Alternatively, or in addition, the displacement measurement may be calculated from the motor position.

Hence, measurements of the displacement sensor can be used to calibrate the signal of the flow rate sensor. Alternatively, or in addition, measurements of a load sensor may be used to calibrate the signal of flow rate sensor. Alternatively, or in addition, the measurements of the displacement sensor may be used to calibrate the signal of the load sensor.

One particular advantage of the syringe pump systems described herein is that by exerting a force onto the syringe plunger with the biasing mechanism and controlling the infusate flow by means of the flow control valve, the compliance of the biasing mechanism, and the syringe of the infusion set (which is typically made from flexible plastic) is beneficially suppressed or factored out of the system. Another advantage is that modulations of the infusate flow by the flow control valve can be achieved by geometrically relatively small control actions of the flow control valve.

When starting an infusion, the syringe pump systems described herein can be under pre-tension (or pre-load) by the biasing mechanism such that the initial compliance of the system has previously occurred and therefore no longer effects the infusate flow. In combination with the small control actions of the flow control valve, the flow rate set point be reached fast.

Another advantage is that by suppressing or factoring out the compliance of the syringe, a change in pressure on the end of the infusion set (e.g., by vertical displacement of the syringe relatively to the patient) does not lead to unintended increase/decrease in flow, or an unintended overshoot in the negative direction.

Moreover, combining several measurement principles as described herein can be advantageous; as it may provide redundancy in the system. That is, in some embodiments two or more independent signals that are indicative of the infusate flow rate may be compared by the controller of the syringe pump system.

Another advantage of the syringe pump systems described herein lies in the economic implication, which stems from different embodiments, and are not limited to the example discussed below. The combination of two measurement systems, such as a reusable flow rate sensor that abuts a disposable infusion tube, in combination with a relatively inexpensive displacement sensor system (with a rather low resolution) that calibrates the flow rate sensor, may yield a more economic price point. This can be more economic than, for example, a high-end calibrated disposable flow rate sensor which has to be replaced after every infusion. Additionally, some embodiments require fewer parts than current systems on the market, which possibly yields reduced manufacturing costs.

Another advantage of the syringe pump systems described herein is that the infusate flow does not only rely on the step-wise movement of a stepper motor (which can result in peaks in the infusate flow rate with every step). As the system’s infusate flow rate is controlled via the flow control valve, the flow rate can be maintained by means of small fast corrective movements, which leads to a steady flow rate with minimal flow variations.

Another advantage is that an obstruction of the infusion tube or in the patient vein, which can lead to a blockage and a cease of fluid delivery, can be detected fast by the measurement systems employed.

Although this specification contains many specific configurations, which are viewed as particularly advantageous, it is apparent that modifications and variations are possible without departing from the scope and spirit of the disclosure described herein. Certain features, which are described in the context of a separate embodiment can also be implement in a combination of and with other embodiments. Although some embodiments are preferred and seen as advantageous is stated that the present disclosure is not limited to these preferred aspects of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cut-away axonometric view of an example syringe pump infusion system according to some embodiments.

FIG. 2 is a schematic diagram of an example syringe pump infusion system according to some embodiments.

FIG. 3 is perspective view of a cross-section of a perfusion tube that has an example flow sensing device abutted against the outside of the tube (but not affixed to the tube).

FIG. 4 shows a cut-away axonometric view of another example syringe pump infusion system according to some embodiments.

FIG. 5 is a schematic diagram of another example syringe pump infusion system according to some embodiments.

FIGS. 6 and 7 illustrate the adaptive calculation of an example load trajectory and the corresponding motor steps.

FIG. 8 is a schematic diagram of another example syringe pump infusion system according to some embodiments.

FIGS. 9 and 10 illustrate the adaptive calculation of another example load trajectory.

FIG. 11 is a schematic diagram of another example syringe pump infusion system according to some embodiments.

FIG. 12 is a schematic diagram of another example syringe pump infusion system according to some embodiments.

FIG. 13 illustrates a patient receiving an infusion while the elevation of the syringe pump is changed.

FIG. 14 compares the start-up performance of the syringe pump infusion systems described herein (“System 1”) and a conventional system (“System 2”).

FIG. 15 compares the performance, when a syringe pump is vertically displaced relatively to the patient, of the syringe pump infusion systems described herein (“System 1”) and a conventional system (“System 2”).

FIG. 16 compares the performance at steady state flow of the syringe pump infusion systems described herein (“System 1”) and a conventional system (“System 2”).

DETAILED DESCRIPTION OF THE DRAWINGS

This disclosure describes infusion devices and methods for controllably infusing a patient with a therapeutic medical fluid.

Referring to FIG. 1, an example syringe pump infusion system 100 includes an example syringe pump 110 and an example infusion set 140. The infusion set 140 is releasably coupleable with the syringe pump 110. Here, the infusion set 140 is depicted in a coupled arrangement with the syringe pump 110.

The infusion set 140 includes a syringe plunger 142, a syringe barrel 144, an infusion tube 146, and an infusion needle 148. A distal end portion of the syringe plunger 142 includes a piston seal member 143 that is slidably coupled within the syringe barrel 144. The infusion tube 146 is coupled to the distal end of the syringe barrel 144, and is in fluid communication with an internal space defined by the syringe barrel 144. The infusion needle 148 is coupled to the distal end of the infusion tube 146, and is in fluid communication with the infusion tube 146 (and with the internal space defined by the syringe barrel 144). The infusion needle 148 can be percutaneously engaged with the vasculature of a patient that is using the syringe pump infusion system 100.

During operation of the syringe pump infusion system 100, the internal space defined by the syringe barrel 144 can contain a therapeutic medical fluid (or “infusate”). When the syringe plunger 142 is pushed distally to pressurize the infusate within the syringe barrel 144, the infusate is urged to flow into the vasculature of the patient via the infusion tube 146 and the infusion needle 148.

The syringe pump 110 includes a biasing mechanism 112 arranged to press against the syringe plunger 142. In the depicted embodiment, the biasing mechanism 112 includes a motor and a gear train including a rack and pinion. In some embodiments, the motor is a stepper motor.

The syringe pump 110 can also include a controller 114 and a user interface 116. In some embodiments, a patient or clinician can enter or program a desired infusate flow rate set point via the user interface 116. Thereafter, in some embodiments the controller 114 will operate the biasing mechanism 112 so as to deliver the infusate at or near to the desired infusate flow rate.

FIG. 2 schematically depicts another example syringe pump infusion system 200. The syringe pump infusion system 200 includes an example syringe pump 210 and the example infusion set 140. The infusion set 140 is releasably coupleable with the syringe pump 210. Here, the infusion set 140 is depicted in a coupled arrangement with the syringe pump 210.

The syringe pump 210 includes a biasing mechanism 212 arranged to press against the syringe plunger 142. In the depicted embodiment, the biasing mechanism 212 includes a motor (and a gear train can be included as part of the biasing mechanism 212). The syringe pump 210 also includes a controller 214 and a user interface (not depicted). It should be understood that, as used herein, a “controller” can broadly include hardware and software. For example, the controller 214 can include one or more components such as, but not limited to, processors, memory, circuitry, discrete devices, inputs, outputs, power sources, programs, executable instructions, and the like.

In the depicted embodiment, the syringe pump 210 also includes a flow control valve 216. The flow control valve 216 is arranged to adjustably restrict the flow of the infusate in the infusion tube 146. For example, in some embodiments the flow control valve 216 is configured to deform the infusion tube 146 to differing extents to thereby induce a flow restriction or fluidic pressure loss in the infusion tube 146. In some embodiments, the flow control valve 216 can press on an outer wall of the infusion tube 146 to pinch the infusion tube 146 to differing extents. In such a case, the infusion tube 146 can be releasably coupleable with the flow control valve 216 such that the flow control valve 216 does not get wetted by the infusate.

The flow control valve 216 is in electrical communication with the controller 214. Accordingly, the controller 214 can control the flow control valve 216 to adjustably restrict the flow of the infusate in the infusion tube 146. In other words, the controller 214 can modulate the infusate flow rate by controlling the extent to which the flow control valve 216 deforms the infusion tube 146.

The syringe pump 210 also includes a measurement system. In the depicted embodiment, the measurement system comprises a flow rate sensor 218. In some embodiments, as an alternative to, or in addition to, the flow rate sensor 218, the measurement system can comprise a load sensor (e.g., as described further below). The flow rate sensor 218 is configured to measure a flow rate of the infusate in the infusion tube 146. The flow rate sensor 218 is in electrical communication with the controller 214. That is, the controller 214 is configured to receive one or more signals indicative of the infusate flow rate measured by the flow rate sensor 218.

The syringe pump infusion system 200 is configured to deliver an infusion to a patient while controlling the infusate flow rate to a set-point in a closed-loop manner. For example, an infusate flow rate set-point can be entered via the user interface and received by the controller 214. Then, with the flow control valve 216 maintaining the infusion tube 146 fully closed, the motor 212 can be activated by the controller 214 to press against the syringe plunger 142. Since the flow control valve 216 is fully closing the infusion tube 146, no infusate will flow through the infusion tube 146. Yet, one or more compliances in the syringe pump infusion system 200 (e.g., backlash of the motor 212 and/or its drive system, the flexure/expansion of the syringe barrel 144, etc.) takes place. In this manner, the compliances in the system 200 are effectively factored out of having effects on the infusate flow rate. Thereafter, the controller 214 causes the flow control valve 216 to gradually open to allow the infusate to flow. The flow rate sensor 218 can detect the flow rate of the infusate flowing in the infusion tube 146 and provide one or more signals indicative of the measured infusate flow rate to the controller 214. Then, the controller 214 can compare the measured infusate flow rate from the flow rate sensor 218 to the set point. In some cases the comparison of the measured infusate flow rate with the set point can be performed using special sophisticated algorithms or methods such as proportional-integral-derivative (PID) control methods. Based on the comparison of the measured infusate flow rate from the flow rate sensor 218 and the set point, the controller 214 can then modulate the infusate flow rate by controlling the flow control valve 216 to adjustably restrict the flow of the infusate in the infusion tube 146.

Referring also to FIG. 3, in some embodiments the flow rate sensor 218 is configured to abut against an outside of the infusion tube 146, while the infusion set 140 is releasably coupled with the syringe pump 210, such that the flow rate sensor 218 is not fixed to the infusion tube 146. A variety of different types of such flow rate sensors can be used. In the depicted example embodiment, the flow rate sensor 218 may comprise a first temperature sensor 220a, a second temperature sensor 220b, and a heater element 222 positioned between the first and second temperature sensors 220a-b. In operation, the heater element 222 heats some of the infusate within the infusion tube 146. The flow rate sensor 218 provides a voltage signal to the controller 214, which corresponds to a difference in temperature detected by the first and second temperature sensors 220a-b. The controller 214 can be programmed to correlate the voltage received from the flow rate sensor 218 to an infusate flow rate. In some embodiments, the controller 214 is programmed with a characteristic nonlinear curve equation which is known for the purpose of correlating the voltage received from the flow rate sensor 218 to an infusate flow rate.

Other types of flow rate sensors configured to abut against an outside of the infusion tube 146 can also be used (as an alternative to the flow rate sensor 218 depicted in FIG. 3). For example, in some embodiments, a single heater element and a single temperature sensor are included as part of the flow rate sensor. The single temperature sensor is positioned downstream of the heater element. The flow sensor is positioned to measure the temperature of the fluid within the perfusion conduit. The heater element is wired in a circuit to be kept at a constant temperature above the fluid within the perfusion conduit. This way, if there are temperature changes within the medium, the flow sensor is less dependent on them. The flow of the perfusion liquid causes a temperature change of the heater element, the faster the flow the more the heater element is cooled down. The voltage drop across the heater element can thus be used to measure the flow rate within the tubing.

In another example, a flow rate sensor includes a single heater element and a single temperature sensor are included as part of the flow rate sensor. The single temperature sensor is positioned downstream of the heater element. In some such embodiments, the heater introduces a certain amount of heat to the infusate and thereby increases the temperature in a local part of the infusate (i.e., essentially the infusate adjacent to the heater). By the infusate flow prevailing inside the tubing, this heated part of the infusate is moved downstream. Once the heated infusate reaches the temperature sensor, the temperature at the sensor increases, registering the arrival of the heated infusate. The time difference between the heater pulse and the temperature increase at the temperature sensor is related to the infusate velocity and the infusate flow rate within the tubing. If the distance between the heater and the temperature sensor and the cross-section of the tubing are known, the infusate flow rate can be determined, using those parameters.

While the flow rate sensor 218 depicted in FIG. 3 is not fixed to the infusion tube 146, in some embodiments, other styles of flow rate sensors can be used. Some such flow rate sensors can be in-line with the infusion tube 146.

Referring to FIG. 4, the syringe pump infusion system 200 (which is described above in reference to the schematic illustration of FIGS. 2 and 3) is depicted here in a realistic form factor. It can be observed that the syringe pump infusion system 200 (as depicted here in FIG. 4) is similar to that of FIG. 1, but with the addition of the flow control valve 216 and the flow rate sensor 218.

The realistic form factor of the syringe pump infusion system 200 is provided as an example of how schematically-depicted syringe pump infusion systems described herein can be implemented. That is, while some other syringe pump infusion systems described herein may only be described in reference to a schematic illustration, it should be understood that each of the syringe pump infusion systems described herein can be implemented in a realistic form factor—as exemplified here in regard to the syringe pump infusion system 200.

FIG. 5 schematically depicts another example syringe pump infusion system 300. The syringe pump infusion system 300 includes an example syringe pump 310 and the example infusion set 140. The infusion set 140 is releasably coupleable with the syringe pump 310. Here, the infusion set 140 is depicted in a coupled arrangement with the syringe pump 310.

The syringe pump infusion system 300 includes a biasing mechanism (the motor 212), the controller 214, the flow control valve 216, and a measurement system comprising a load sensor 318. Note that the load sensor 318 is also depicted in FIG. 4, which provides a more realistic implementation in addition to the schematic depiction of FIG. 5. In some embodiments, the measurement system of the syringe pump infusion system 300 may also include the flow rate sensor 218 (FIGS. 2 and 3), however its inclusion is purely optional.

The load sensor 318 is arranged to measure the force exerted by the biasing mechanism against the syringe plunger 142. The force exerted by the biasing mechanism against the syringe plunger 142 is indicative of the infusate flow rate. The controller 214 is configured to receive (from the load sensor 318) one or more signals indicative of the force exerted by the biasing mechanism against the syringe plunger 142, and to modulate an infusate flow rate by controlling the flow control valve 216 to adjustably restrict the flow of the infusate in the infusion tube 146.

FIGS. 6 and 7 illustrate aspects pertaining to how the syringe pump infusion system 300 (and other syringe pump infusion systems described herein) can be started up and operated. In preparation for delivering an infusion from the syringe pump infusion system 300, and with the flow control valve 216 fully closing the infusion tube 146, the motor 212 is incrementally actuated (as depicted by the steps on the left side of FIG. 7). As the incremental actuation of the motor 212 is continued, the motor 212 begins to exert an increasing amount of load against the syringe plunger 142 (as depicted in FIG. 6 by the portion of the plotted line extending from the graph’s origin to the line LI). When the load sensor 318 measures a load that surpasses an initial threshold LI, the controller 214 discontinues the incremental actuation of the motor 212. The load may continue to rise some more so that it surpasses the threshold LI. The peak of the load exerted against the syringe plunger 142 can be referred to as the pre-start load level.

Based on an infusate flow rate set-point entered via the user interface and received by the controller 214, one or more desired linear load trajectories are determined by the controller 214. The first determined desired linear load trajectory has the pre-start load level as its starting point, an endpoint which lies just below LI, and a time delta of TO. The time TO is determined by the controller 214 in correspondence to the inner cross-sectional area of the syringe barrel 144 and the displacement of the syringe plunger 142 relative to the syringe barrel 144, which corresponds to the infusate flow rate set-point. The determined desired linear load trajectories are depicted by the solid lines in FIG. 6.

When the actual flow of the infusate is initiated, the controller 214 causes the flow control valve 216 to open (to reduce its restriction of the infusion tube 146) to let infusate flow through the infusion set 140. The motor 212 remains deactivated for now (as depicted by FIG. 7). The force exerted against the syringe plunger 142 gradually declines as the infusate flows through the infusion set 140 into the patient (as depicted by the declining dashed lines in FIG. 6). The controller 214 is configured to modulate the flow control valve 216 so that the signal from the load sensor 318 closely follows the calculated load set trajectories. Once the load signal falls below the threshold LI, the controller 214 actuates the motor 212 (e.g., to move one or more steps, in the case of a stepper motor), and the resulting new peak value of the force against the syringe plunger 142 is then the starting point for new desired linear load trajectory (which is calculated anew after every motor actuation). This is process repeated as long as the infusion is continued.

FIG. 8 schematically depicts another example syringe pump infusion system 400. The syringe pump infusion system 400 includes an example syringe pump 410 and the example infusion set 140. The infusion set 140 is releasably coupleable with the syringe pump 410. Here, the infusion set 140 is depicted in a coupled arrangement with the syringe pump 410.

The syringe pump infusion system 400 includes a biasing mechanism comprising a spring 412, the controller 214, the flow control valve 216, and the load sensor 318. In some embodiments, the syringe pump infusion system 400 may also include the flow rate sensor 218 (FIGS. 2 and 3), however its inclusion is purely optional.

The load sensor 318 is arranged to measure the force exerted by the spring 412 against the syringe plunger 142. The force exerted by the spring 412 against the syringe plunger 142 is indicative of the infusate flow rate. The controller 214 is configured to receive (from the load sensor 318) one or more signals indicative of the force exerted by the spring 412 against the syringe plunger 142, and to modulate an infusate flow rate by controlling the flow control valve 216 to adjustably restrict the flow of the infusate in the infusion tube 146.

Referring to also to FIGS. 9 and 10, given that the spring 412 follows Hook’s law, different forces detected by the load sensor 318 correspond to different volumes of infusate within the syringe barrel 144. That is, depending on the volume within the syringe barrel 144, the signal output by the load sensor 318 varies and is a known characteristic of the system 400.

Based on an infusate flow rate set-point entered via the user interface and received by the controller 214, and based on the fact that force signals from the load sensor 318 correspond to known infusate volumes within the syringe barrel 144, a desired linear load trajectory is determined by the controller 214 (as shown in FIG. 9). From relative changes in the load signal the dispensed volume can be inferred given that the cross-section of the syringe barrel 144 is known. As depicted in FIG. 10, the controller 214 is configured to receive the signals from the load sensor 318 indicative of the force exerted by the spring 412 against the syringe plunger 142 and to modulates the infusate flow rate by controlling the flow control valve 216 in such way that the load signal (the dashed line in FIG. 10) approximately follows the calculated desired linear load trajectory.

Referring to FIG. 11, schematically depicts another example syringe pump infusion system 500. The syringe pump infusion system 500 includes an example syringe pump 510 and the example infusion set 140. The infusion set 140 is releasably coupleable with the syringe pump 510. Here, the infusion set 140 is depicted in a coupled arrangement with the syringe pump 510.

The syringe pump infusion system 500 includes a biasing mechanism comprising the spring 412, the controller 214, the flow control valve 216, the flow rate sensor 218, and a displacement sensor 520. In some embodiments, the syringe pump infusion system 500 may also include the load sensor 318 (FIGS. 5 and 8), however its inclusion is purely optional.

The displacement sensor 520 can advantageously be used to calibrate the flow rate sensor 218 in the following manner. The displacement sensor 520 provides a signal to the controller 214 indicative of the distance travelled by the syringe plunger 142 relative to the syringe barrel 144, or indicative of the position of the syringe plunger 142 relative to the syringe barrel 144 at a particular point in time. Using such a signal(s), and in combination with the known cross-sectional area of the syringe barrel 144, the controller 214 can determine the actual infusate flow rate. This determined actual infusate flow rate can be used to calibrate the flow rate sensor 218. In some embodiments, the displacement sensor 520 may have a low resolution (and as such may only provide a signal update relatively infrequently in the context of the operation of the syringe pump infusion system 500), whereas the flow rate sensor 520 can continuously provide a voltage which can be used by the controller 214 to modulate the flow control valve 216. Accordingly, the controller 214 can receive one or more signals indicative of the infusate flow rate measured by the calibrated flow rate sensor 218, and can modulate the infusate flow rate by controlling the flow control valve 216 to adjustably restrict the flow of the infusate in the infusion tube 146.

Referring to FIG. 12, schematically depicts another example syringe pump infusion system 600. The syringe pump infusion system 600 includes an example syringe pump 610 and the example infusion set 140. The infusion set 140 is releasably coupleable with the syringe pump 610. Here, the infusion set 140 is depicted in a coupled arrangement with the syringe pump 610.

The syringe pump infusion system 600 includes a biasing mechanism comprising the spring 412, the controller 214, the flow control valve 216, and the flow rate sensor 218. In some embodiments, the syringe pump infusion system 600 may also include the load sensor 318 (FIGS. 5 and 8), or the displacement sensor 520 (FIG. 11), however inclusion of either one or both of those is purely optional.

The controller 214 is configured to receive a signal indicative of the flow rate from the flow rate sensor 218 and to modulate the infusate flow rate by controlling the flow control valve 216 to conform the infusate flow rate measured by the flow rate sensor 218 to a flow rate set point entered via the user interface of the syringe pump infusion system 600.

FIG. 13 depicts a patient 10 receiving an infusion of a therapeutic medical fluid from an example syringe pump infusion system 700 that includes a syringe pump 710. It should be understood that the syringe pump infusion system 700 is representative of any of the syringe pump infusion systems described herein.

In the depicted example implementation, the syringe pump 710 is supported by a structure 740 that is spaced apart from the patient 10. In some other implementations, the syringe pump infusion system 700 is configured to be worn or carried by the patient 10 such that the patient is ambulatory while using the syringe pump infusion system 700.

At the venous port 12 of the patient 10, a venous pressure is present and in the infusion set 140 a hydrostatic pressure is present. The hydrostatic pressure is dependent (in part) on the relative height difference between venous port 12 and the syringe pump 700.

In the event that the syringe pump 710 is vertically displaced from hl to h2, a change in the hydrostatic pressure in the infusion set 140 is induced. For example, if the syringe pump 710 is raised to a higher elevation relative to the patient 10 (as depicted by a movement from hl to h2) hydrostatic pressure in the infusion set 140 increases. Such an increase could lead to an increase in the infusate flow rate. However, the syringe pump infusion systems described herein are designed and configured to compensate for syringe pump elevation changes such that the infusate flow rate is maintained in accordance with the set-point.

FIG. 14 illustrates advantages of the syringe pump infusion systems described herein when starting up from zero flow to a flow rate set point. The dashed line (labelled “System 1”) shows the start-up graph of the syringe pump infusion systems described herein and the solid line (labelled “System 2”) shows the start-up of a typical existing conventional syringe pump systems.

It can be seen that the syringe pump infusion systems described herein advantageously reach the flow rate set point essentially immediately, and as such shows fast start-up performance. This is possible due because the biasing mechanism in combination with the flow control valve 216 suppresses the negative effects of the compliances of both the syringe barrel 144 and the syringe pump mechanical assembly (e.g., backlash) prior to start the infusion. Additionally, the restriction of the infusate flow by the flow control valve 216 can be achieved fast geometrically by relative small control actions of the flow control valve 216.

FIG. 15 shows the responsiveness of the syringe pump infusion systems described herein (“System 1”) in comparison to a typical existing conventional syringe pump system (“System 2”) to a change in pressure difference between the syringe and the patient’s vein. Such a pressure change can be induced, for example, by a vertical displacement of the syringe/pump relative to the patient (e.g., as shown in FIG. 13). The pump infusion systems described herein (System 1) are virtually unaffected by the elevation change, and show no unintended change in flow or even overshoot in the negative directions with a time to recover to steady state.

FIG. 16 shows the steady state flow rate of the syringe pump infusion systems described herein (“System 1”) in comparison to the steady state flow rate of a typical existing conventional syringe pump system (“System 2”). With a spring as a biasing mechanism (as in some of the syringe pump infusion systems described herein), the infusate flow does not rely on the step-wise movement of a stepper motor (as in typical existing conventional syringe pump systems). The syringe pump infusion systems described herein control the infusate flow rate via the flow control valve 216, which can maintain the infusate flow rate by means of small fast corrective movements of the flow control valve 216. In contrast, the step-wise movement of a stepper motor (as in typical existing conventional syringe pump systems) results in the cyclically variable flow rate as shown (“System 2”). Accordingly, the syringe pump infusion systems described herein are particularly advantageous for maintaining a steady infusate flow rate with minimal flow variations.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any invention or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described herein as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system modules and components in the embodiments described herein should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single product or packaged into multiple products.

Particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. For example, the actions recited in the claims 5 can be performed in a different order and still achieve desirable results. As one example, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

Claims

1. A syringe pump, comprising:

a biasing mechanism arranged to press against a syringe plunger of an infusion set, while the infusion set is releasably coupled with the syringe pump, to urge an infusate in the infusion set to flow through an infusion tube of the infusion set;

a flow control valve arranged to adjustably restrict the flow of the infusate in the infusion tube;

a flow rate sensor configured to measure an infusate flow rate in the infusion tube; and a controller configured to: (i) receive one or more signals indicative of the infusate flow rate measured by the flow rate sensor and (ii) modulate the infusate flow rate by controlling the flow control valve to adjustably restrict the flow of the infusate in the infusion tube.

2. The syringe pump of claim 1, further comprising a user interface, and wherein the controller is configured to receive one or more signals indicative of an infusate flow rate set point input via the user interface.

3. The syringe pump of claim 2, wherein the controller is configured to modulate the infusate flow rate based on the infusate flow rate set point.

4. The syringe pump of claim 1, wherein the biasing mechanism comprises a spring.

5. The syringe pump of claim 1, wherein the biasing mechanism comprises a motor.

6. The syringe pump of claim 1, wherein the biasing mechanism comprises a pneumatic cylinder.

7. The syringe pump of claim 1, further comprising a displacement sensor in signal communication with the controller and arranged to detect a position of the syringe plunger relative to a syringe barrel with which the syringe plunger is slidably coupled.

8. The syringe pump of claim 7, wherein the controller is configured to calibrate the flow rate sensor using a signal from the displacement sensor.

9. The syringe pump of claim 1, further comprising a load sensor in signal communication with the controller and arranged to measure force exerted by the biasing mechanism against the syringe plunger.

10. The syringe pump of claim 9, wherein the controller is configured to calibrate the flow rate sensor using a signal from the load sensor.

11. The syringe pump of claim 1, wherein the flow control valve is configured to deform the infusion tube to differing extents.

12. The syringe pump of claim 1, wherein the syringe pump is configured to be worn or carried by a patient such that the patient is ambulatory while using the syringe pump.

13. The syringe pump of claim 1, wherein the syringe pump is configured to be supported by a structure spaced apart from a patient using the syringe pump.

14. The syringe pump of claim 1, wherein the flow rate sensor is configured to abut against an outside of the infusion tube, while the infusion set is releasably coupled with the syringe pump, such that the flow rate sensor is not fixed to the infusion tube.

15. A syringe pump, comprising:

a biasing mechanism arranged to exert force against a syringe plunger of an infusion set, while the infusion set is releasably coupled with the syringe pump, to urge an infusate in the infusion set to flow through an infusion tube of the infusion set;

a load sensor arranged to measure the force exerted by the biasing mechanism against the syringe plunger;

a flow control valve arranged to adjustably restrict the flow of the infusate in the infusion tube; and a controller configured to: (i) receive, from the load sensor, one or more signals indicative of the force exerted by the biasing mechanism against the syringe plunger and (ii) modulate an infusate flow rate by controlling the flow control valve to adjustably restrict the flow of the infusate in the infusion tube.

16. The syringe pump of claim 15, further comprising a user interface, and wherein the controller is configured to receive one or more signals indicative of an infusate flow rate set point input via the user interface.

17. The syringe pump of claim 16, wherein the controller is configured to modulate the infusate flow rate based on the infusate flow rate set point.

18. The syringe pump of claim 15, wherein the biasing mechanism comprises a spring.

19. The syringe pump of claim 15, wherein the biasing mechanism comprises a motor.

20. The syringe pump of claim 15, further comprising a displacement sensor in signal communication with the controller and arranged to detect a position of the syringe plunger relative to a syringe barrel with which the syringe plunger is slidably coupled.

21. The syringe pump of claim 15, wherein the biasing mechanism comprises a stepper motor in signal communication with the controller, and wherein the controller is configured to detect a position of the syringe plunger relative to a syringe barrel with which the syringe plunger is slidably coupled based on a known step size of the stepper motor.

22. The syringe pump of claim 15, further comprising a flow rate sensor in signal communication with the controller and configured to measure the infusate flow rate in the infusion tube.

23. The syringe pump of claim 22, wherein the controller is configured to calibrate the flow rate sensor using the one or more signals from the load sensor.

24. The syringe pump of claim 15, wherein the flow control valve is configured to deform the infusion tube to differing extents.

25. The syringe pump of claim 15, wherein the syringe pump is configured to be worn or carried by a patient such that the patient is ambulatory while using the syringe pump.

26. The syringe pump of claim 15, wherein the syringe pump is configured to be supported 5 by a structure spaced apart from a patient using the syringe pump.