Patent Description:
Programmable infusion pumps are used to carry out controlled delivery of liquid food for enteral feeding and medications for various purposes, for example pain management. In a common arrangement, an infusion pump receives a disposable administration set comprising flexible tubing having a tubing segment designed to be engaged by a pumping mechanism of the infusion pump. The administration set may further comprise a pair of mounting components fixedly attached to the flexible tubing at predetermined locations at or near opposite ends of the tubing segment, whereby the mounting components are receivable by respective mating features on the infusion pump to secure the tubing segment in proper position for operative engagement by the pumping mechanism. One of the mounting components may provide additional functionality beyond helping to properly locate the tubing segment. For example, one of the mounting components may be configured as a free-flow prevention device operable to selectively stop and permit flow of the infusion liquid through the tubing. Upon loading the administration set in the pump, the free-flow prevention device is actuated from its normal flow-stopping closed position to its open position allowing flow. An example of the arrangement described above is disclosed in <CIT> to Moubayed et al.

Documents <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT> disclose free flow prevention devices or infusions systems.

It is known to provide different types of administration sets all of which are intended for use with a particular infusion pump model or models. The various types of administration sets may be distinguishable from one another according to design specifications that are chosen based on the specific intended use of the administration set. For example, the tubing segment of the administration set may be dimensioned with a specific inner diameter and wall thickness for carrying certain liquid formulations of known viscosity, and may be formed of a material having a specific durometer. The material durometer, inner diameter, and wall thickness of the tubing segment are held within close manufacturing tolerances to ensure that the administration set provides intended flow characteristics when the tubing segment is acted upon by the pumping mechanism of the infusion pump.

Various types of administration sets may also be distinguishable from one another based on coupling hardware and other structural features provided as part of the administration set. For example, an end of the administration set may be provided with a bag for storing liquid, a vented vial spike, or a non-vented spike. As another example, the administration set may include a filter of a predetermined pore size, or it may not include a filter. Other structural features that may or may not be included in a particular administration set are an anti-siphon valve and a Y-connector having a check valve.

For safety reasons, it is desirable to ensure that the type of administration set chosen for use with a particular infusion pump to deliver an intended infusion protocol is the proper administration set. As an initial matter, it is desirable to confirm that an administration set is installed in the infusion pump. The installed administration set should be authentic from the standpoint that it is approved by the infusion pump manufacturer for use with the infusion pump. The installed administration set should also be of a type that is configured for delivering a selected infusion protocol which the infusion pump is programmed to execute.

What is needed is an administration set detection and authentication scheme that is easily implemented without adding hardware to the administration set or the infusion pump, that determines whether or not an administration set is installed and is authentic, and that distinguishes among different types of authentic administration sets to identify the type of administration set that is installed.

In accordance with the present invention, a free-flow prevention device for controlling flow of an infusion liquid through tubing of an administration set comprises a movable plunger that includes a cam surface defining an uneven profile along a direction of movement of the plunger, wherein the shape of the cam surface profile indicates the administration set is authorized for use with the infusion pump and may further indicate the type of administration set.

A sensor in the infusion pump is arranged to sense movement of the plunger as a platen of the infusion pump is latched thereby moving the plunger from a closed position to an open position. As the plunger is moved, the cam surface of the plunger displaces a follower in contact with the cam surface, and the sensor detects displacement of the follower to generate a profile signal in the time domain representative of the cam surface profile.

A processor compares the profile signal to stored reference values corresponding to various predetermined authorized profiles, and determines whether or not the administration set is loaded in the infusion pump and whether or not the administration set is authorized for use with the infusion pump. If the administration set is not properly loaded or is not authorized, the processor sends a command disabling operation of the infusion pump. The processor may also determine the specific type of the administration set from among a plurality of administration set types, and send a command disabling operation of the pump if the determined type of the administration set is incompatible with a desired infusion protocol entered into the infusion pump by a user.

The invention is defined according to claim <NUM>, with dependent claims <NUM>-<NUM> defining further embodiments.

The nature and mode of operation of the present invention will now be more fully described in the following detailed description of the invention taken with the accompanying drawing figures, in which:.

<FIG> shows an infusion pump <NUM> and <FIG> shows a disposable administration set <NUM> designed to be removably received by infusion pump <NUM>. Administration set <NUM> comprises tubing <NUM> for conveying an infusion liquid, and a free-flow prevention device <NUM> operable to selectively stop and permit flow of the infusion liquid through the tubing <NUM>. Administration set <NUM> may also comprise a locator pin <NUM>. Free-flow prevention device <NUM> and locator pin <NUM> may be fixedly attached to tubing <NUM> at separate locations along the tubing. For example, free-flow prevention device <NUM> and locator pin <NUM> may be bonded to tubing <NUM> by a bonding agent. As may be seen in <FIG>, infusion pump <NUM> has a first recess <NUM> sized to removably receive free-flow prevention device <NUM>, and a second recess <NUM> sized to removably receive locator pin <NUM>. Administration set <NUM> is loaded into infusion pump <NUM> by inserting free-flow prevention device <NUM> into first recess <NUM> and locator pin <NUM> into second recess <NUM> such that a segment <NUM> of tubing <NUM> wraps around a pumping mechanism <NUM> of pump <NUM>. Free-flow prevention device <NUM> may include a breakaway detent tab <NUM> for maintaining free-flow prevention device <NUM> in an open condition prior to loading of administration set <NUM> in pump <NUM>. In the illustrated embodiment, pumping mechanism <NUM> is a peristaltic pumping mechanism having a plurality of extendable and retractable pumping fingers <NUM> that are moved by rotation of a motor-driven eccentric cam <NUM> to engage tubing segment <NUM> in sequential peristaltic fashion such that liquid is pumped through tubing <NUM>.

As may be seen in <FIG>, infusion pump <NUM> includes a platen <NUM> pivotally mounted at a pivot pin <NUM>. Platen <NUM> has a platen surface 30A that comes into contact with tubing segment <NUM> opposite pumping fingers <NUM> when platen <NUM> is pivoted down toward pumping mechanism <NUM>. A locking latch <NUM> is pivotally mounted at a free end of platen <NUM> by a pivot pin <NUM>. As will be described in detail below, locking latch <NUM> is operable to secure platen <NUM> in a closed position on infusion pump <NUM> with platen surface 30A contacting tubing segment <NUM> in preparation for starting a pumping protocol. Locking latch <NUM> further serves as an actuating member for moving a plunger <NUM> of free-flow prevention device <NUM>, visible in <FIG>, relative to a carrier <NUM> of free-flow prevention device <NUM>.

<FIG> illustrate closure of platen <NUM> and operation of locking latch <NUM> after administration set <NUM> is positioned in pump <NUM>. Platen <NUM> is pivoted counterclockwise until a drive arm <NUM> of locking latch <NUM> contacts a top portion of plunger <NUM>, and then locking latch <NUM> is pivoted clockwise relative to platen <NUM> such that a curved surface <NUM> at the end of drive arm <NUM> forces plunger <NUM> to move downward relative to carrier <NUM>. As locking latch <NUM> is pivoted, a jaw opening <NUM> on each side of the locking latch securely mates with a corresponding lateral protrusion <NUM> of the infusion pump body to lock platen <NUM> in its closed operating position.

In accordance with the present invention, the movement of plunger <NUM> is sensed in the time domain and provides information for detecting and authenticating administration set <NUM>. In an embodiment of the invention, plunger <NUM> includes a cam surface <NUM> defining an uneven profile along a direction of movement of the plunger, wherein the uneven profile of cam surface <NUM> indicates that administration set <NUM> is authorized for use with infusion pump <NUM>, and further indicates the type of administration set <NUM>. The basic operation of free-flow prevention device <NUM> may be understood from <FIG>. Plunger <NUM> is mounted in carrier <NUM> for sliding reciprocal motion relative to the carrier between a closed position (<FIG>) in which respective tube openings in the plunger and carrier are misaligned to pinch tubing segment <NUM> closed to prevent flow through tubing <NUM>, and an open position (<FIG>) in which respective tube openings in the plunger and carrier are substantially aligned so that tubing segment <NUM> is not pinched closed and flow is permitted through tubing <NUM>. A spring <NUM> acts between carrier <NUM> and plunger <NUM> to bias plunger <NUM> toward the closed position shown in <FIG>. As may be understood, plunger <NUM> must be moved against the biasing force of spring <NUM> to move plunger from the closed position to the open position. As explained above with reference to <FIG>, such force is provided by pivoting locking latch <NUM> relative to platen <NUM> so that curved surface <NUM> at the end of drive arm <NUM> moves plunger <NUM> downward relative to carrier <NUM>. Plunger <NUM> is held in the open position when platen <NUM> is secured by locking latch <NUM>. When locking latch <NUM> is pivoted counterclockwise in <FIG> to allow platen <NUM> to be opened, plunger <NUM> is allowed to move under force of spring <NUM> to the closed position to prevent free flow. In addition to the basic operation of free-flow prevention device <NUM>, the movement of plunger <NUM> provides a detectable signature that depends on the profile of the plunger's cam surface <NUM>.

Infusion pump <NUM> comprises a sensor <NUM> arranged to sense the movement of plunger <NUM> relative to carrier <NUM>. Sensor <NUM> generates a profile signal in the time domain representative of the profile of cam surface <NUM>. In an embodiment of the invention illustrated by <FIG>, sensor <NUM> may be a strain gauge and infusion pump <NUM> may comprise a follower <NUM> biased for continuous engagement with cam surface <NUM> of plunger <NUM> when free-flow prevention device <NUM> is loaded in the infusion pump, wherein cam surface <NUM> slidably engages follower <NUM> to displace the follower laterally as plunger <NUM> is moved from the closed position to the open position. Sensor <NUM> has one end portion attached by a fastener <NUM> to a fixed structural member of pump <NUM> (not shown), and another end portion engaged by follower <NUM>, such that lateral displacement of follower <NUM> causes corresponding deflection of sensor <NUM>. Sensor <NUM> and follower <NUM> may be arranged such that sensor <NUM> is slightly deflected even when plunger <NUM> is in the closed position represented by <FIG> and <FIG>, such that a preload is applied by sensor <NUM> on follower <NUM> to maintain engagement of the follower with cam surface <NUM>. The output signal generated by sensor <NUM> is proportional to the amount of deflection of the sensor. The behavior of the signal generated by sensor <NUM> in the time domain will depend on the profile shape of cam surface <NUM>. Thus, by providing various predetermined profiles of cam surface <NUM> that share at least one feature among all profiles and differ from one another with respect to at least one other feature, the cam surface profiles may be used to confirm authenticity of an administration set <NUM> as being compatible with pump <NUM>, and also to determine the specific type of the administration set from among a plurality of different administration set types all of which are compatible with pump <NUM>.

In <FIG>, the profile of cam surface <NUM> includes a first plateau <NUM> and a second plateau <NUM> having different respective "elevations" E1 and E2. As used herein in reference to the profile of cam surface <NUM>, the term "elevation" means a lateral distance from a central axis <NUM> along which plunger <NUM> moves. First plateau <NUM> and second plateau <NUM> may have different respective lengths L1 and L2 in the direction of movement of plunger <NUM>. The profile of cam surface <NUM> may further include a topographical feature <NUM> between first plateau <NUM> and second plateau <NUM>. In the embodiment shown in <FIG>, topographical feature <NUM> takes the form of a ramp between first plateau <NUM> and second plateau <NUM>. Topographical feature <NUM> may take other forms, for example a bump or a recess.

<FIG> shows a voltage signal <NUM> versus time generated by sensor <NUM> in response to the downward motion of plunger <NUM> depicted by <FIG>. As may be seen, signal <NUM> has a first portion <NUM> of relatively low amplitude corresponding to first elevation E1, and a second portion <NUM> of relatively high amplitude corresponding to second elevation E2. Signal <NUM> also includes a transition portion <NUM> between first and second portions <NUM> and <NUM> characterized by changing amplitude.

<FIG> shows an alternative plunger <NUM> having another possible profile of cam surface <NUM>. In plunger <NUM>, the topographical feature <NUM> of cam surface <NUM> is a bump that rises in elevation and then drops down slightly as it transitions from first plateau <NUM> to second plateau <NUM>. First plateau <NUM> has the same elevation E1 as that of the plunger <NUM> shown in <FIG>, however second plateau <NUM> has a different elevation E3 that is slightly less than the elevation E2 of plunger <NUM>. <FIG> illustrates a voltage signal <NUM> versus time generated by sensor <NUM> in response to the downward motion of plunger <NUM>. A first portion <NUM> of sensor signal <NUM> has the same amplitude as the first portion <NUM> of sensor signal <NUM> due to matching elevations of the first plateaus <NUM>. A second portion <NUM> of sensor signal <NUM> has an amplitude greater than the amplitude of first portion <NUM>, but less than the amplitude of second portion <NUM> of signal <NUM>, owing to the fact that elevation E3 is less than elevation E2. A transition portion <NUM> of signal <NUM> is characterized by a significant increase in amplitude followed by a modest decrease in amplitude as determined by bump <NUM> in cam surface <NUM> of plunger <NUM>.

<FIG> shows a further alternative plunger <NUM> having yet another possible profile of cam surface <NUM>. In plunger <NUM>, the topographical feature <NUM> of cam surface <NUM> is a bump that rises in elevation and then drops down significantly as it transitions from first plateau <NUM> to second plateau <NUM>. First plateau <NUM> has the same elevation E1 as that of the plungers <NUM> and <NUM>, however second plateau <NUM> has a different elevation E4 that is less than elevation E2 of plunger <NUM> and elevation E3 of plunger <NUM>. <FIG> illustrates voltage signal <NUM> versus time generated by sensor <NUM> in response to the downward motion of plunger <NUM>. A first portion <NUM> of sensor signal <NUM> has the same amplitude as the first portions <NUM> of sensor signals <NUM> and <NUM> due to matching elevations of the first plateaus <NUM>. A second portion <NUM> of sensor signal <NUM> has an amplitude greater than the amplitude of first portion <NUM>, but less than the amplitude of second portion <NUM> of signal <NUM> because elevation E4 is less than elevation E3. A transition portion <NUM> of signal <NUM> is characterized by a significant increase in amplitude followed by a decrease in amplitude as determined by bump <NUM> in cam surface <NUM> of plunger <NUM>.

Thus, signals <NUM>, <NUM>, and <NUM> corresponding to plungers <NUM>, <NUM>, and <NUM> share similar signal portions, but are distinguishable from one another by other signal portions exhibiting different amplitudes and behaviors in the time domain. The similar signal portions may be used to determine the presence and authenticity of an administration set, whereas the different signal portions may be used to determine the specific type of administration set from a plurality of authentic administration sets authorized for use with infusion pump <NUM>.

<FIG> is a schematic diagram showing signal processing electronics of infusion pump <NUM> used to evaluate profile signals generated by sensor <NUM>. An analog signal from sensor <NUM> is converted to a digital signal by an analog-to-digital converter <NUM> and stored in a volatile memory <NUM>. The digitized signal is then read by a processor <NUM> programmed to evaluate the signal. Processor <NUM> executes programming instructions stored in a non-volatile memory <NUM> associated with the processor <NUM>. Memory <NUM> also stores predetermined reference values representing the various respective profile signals of each type of authorized administration set. The reference values may be stored, for example, in a lookup table that provides expected amplitude values at predetermined moments in time for each profile signal. Processor <NUM> executes programming instructions stored in memory <NUM> causing the processor to compare the digitized profile signal from sensor <NUM> to the stored reference values and determine whether or not the administration set is loaded in the infusion pump, and whether or not the administration set is authorized for use with the infusion pump, based on the comparison. Processor <NUM> may be in communication with a pump controller <NUM>, or may itself act as the pump controller, whereby operation of pump <NUM> may be controlled based on an evaluation of the profile signal generated by sensor <NUM>. Pump controller <NUM> is in communication with a user interface display screen <NUM> and a keypad <NUM> for inputting commands and parameters to the controller.

The flow diagram of <FIG> shows, in accordance with an embodiment of the invention, decision logic executed by processor <NUM> and/or controller <NUM> to evaluate a profile signal and control infusion pump <NUM> based on results of the evaluation. In block <NUM>, the digitized profile signal stored in memory <NUM> is read by processor <NUM>. A first comparison is performed in block <NUM> looking at a portion of the signal used to indicate presence and authenticity of an administration set. For example, a comparison of first portion <NUM>, <NUM>, <NUM> of the signal to corresponding stored reference values may be conducted. In decision block <NUM>, flow branches based upon whether the comparison finds a match. If a match is not found, the administration set is determined to be improperly loaded and/or inauthentic, and flow is directed to blocks <NUM> and <NUM> to display an error message on display screen <NUM> and command controller <NUM> to disable operation of pump <NUM>. Thus, the patient is protected from improper loading of an administration set even if the administration set is authorized, and the patient is also protected from use of an unauthorized administration set. If a match is found in block <NUM>, then the administration set is deemed to be properly loaded and authentic, and flow continues to block <NUM>.

In block <NUM>, a further comparison is performed looking at a portion of the profile signal used to indicate the specific type of administration set. For example, a comparison of second portion <NUM>, <NUM>, <NUM> of the signal to corresponding stored reference values, and/or a comparison of transition portion <NUM>, <NUM>, <NUM> of the signal to corresponding stored reference values may be conducted. In decision block <NUM>, flow branches based upon whether the further comparison finds a matching type. If a match is not found, the administration set is determined to be improperly loaded and/or inauthentic, and flow is directed to blocks <NUM> and <NUM>. If a match is found in block <NUM>, the corresponding administration set type is identified and reported as a parameter to pump controller <NUM> in accordance with block <NUM>.

Pump controller <NUM> may be programmed to operate in a predetermined manner based on the identified type of administration set and an infusion protocol entered in pump <NUM> by a user. For example, in block <NUM>, the identified type of administration set may be checked against a predetermined list of valid set types associated with the entered infusion protocol and stored in memory <NUM>. In decision block <NUM>, flow branches based upon whether or not the administration set type is valid for the selected infusion protocol. If not, flow is directed to block <NUM> to display an error message on display screen <NUM> indicating the administration set is the wrong type, and then to block <NUM> to disable operation of pump <NUM>. If the detected administration set type is valid for use in delivering the selected infusion protocol, then pump operation continues in a normal manner. Thus, the present invention protects the patient if the wrong type of administration set is loaded for a desired infusion protocol, even if the administration set is authentic.

Comparisons between the sensed profile signal and the stored predetermined reference values representing various recognized profile signals may be made in different ways. Amplitude values of the sensed profile signal may be sampled at predetermined times and compared to corresponding stored values. Comparisons may also involve determining a time duration that the sensed profile signal remains at a given amplitude level before the amplitude changes, and comparing such duration to an expected duration represented by the stored reference value information. For this type of comparison, it is helpful to design locking latch <NUM> and free-flow prevention device <NUM> such that plunger <NUM> moves at a substantially fixed velocity relative to carrier <NUM> so that the time duration is indicative of the plateau length L1 or L2 in the direction of movement of plunger <NUM>. A first time interval T1 of the profile signal may be evaluated to determine whether or not the administration set is loaded and is authorized, and a second time interval T2 of the profile signal different from the first time interval T1 may be evaluated to determine the type of the administration set. As shown in <FIG>, the first and second time intervals T1 and T2 may overlap one another, but this is an option, not a requirement.

Comparisons may involve some portions of the sensed profile signal, while disregarding at least one other portion of the profile signal. For example, a spike or dip in the amplitude of the profile signal at the transition portion <NUM> due to a bump or recess in cam surface <NUM> may be used as a primary comparison feature, a secondary comparison feature for confirmation, or not at all. Evaluation logic may also be "single step" in nature, whereby the entire sensed profile signal is compared to stored reference values to find a complete match; if no match is found, an error message is displayed and the pump is disabled. If a match is found, the administration set type is known and can be validated with respect to an entered infusion protocol. As will be understood, evaluation of a sensed profile signal, and logic implemented based on the evaluation, are subject to wide design variation.

The particular configuration of sensor <NUM> is also subject to design choice. While a strain gauge is illustrated in the drawings, sensor <NUM> may be a magnetic or capacitive displacement sensor, an optical displacement sensor, or an acoustic displacement sensor. Any type of sensor capable of measuring displacement of follower <NUM> may be used in practicing the present invention.

Claim 1:
An apparatus comprising:
an infusion pump (<NUM>) including a pumping mechanism (<NUM>), an actuating member (<NUM>), a follower (<NUM>) and a sensor (<NUM>); and
an administration set (<NUM>) including tubing (<NUM>) for conveying an infusion liquid and the free-flow prevention device (<NUM>), the free-flow prevention device operable to selectively stop and permit flow of the infusion liquid through the tubing, wherein the free-flow prevention device comprises:
a carrier (<NUM>);
a plunger (<NUM>) movable relative to the carrier between an open position permitting flow of the infusion liquid through the tubing and a closed position stopping flow of the infusion liquid through the tubing; and
means (<NUM>) biasing the plunger toward the closed position;
wherein the plunger includes a cam surface (<NUM>) defining an uneven profile along a direction of movement of the plunger, wherein a shape of the cam surface profile indicates whether the administration set is authorized for use with an infusion pump; and
wherein in use, during movement of the plunger, the cam surface is configured to cause displacement of the follower (<NUM>) in contact with the cam surface
wherein a segment (<NUM>) of the tubing is loadable into the infusion pump for engagement by the pumping mechanism;
wherein the free-flow prevention device is loadable into the infusion pump and is operated by the actuating member, the actuating member being movable from a non-pumping position to a pumping position thereby moving the plunger from the closed position to the open position;
wherein the sensor is arranged to sense movement of the plunger, and the sensor generates a profile signal (<NUM>) in the time domain representative of the cam surface profile; and
wherein the infusion pump further comprises:
a memory (<NUM>) storing predetermined reference values; and
a processor (<NUM>) arranged to receive the profile signal, wherein the processor is programmed to compare the profile signal to the stored reference values and determine whether or not the administration set is loaded in the infusion pump and whether or not the administration set is authorized for use with the infusion pump, based on the comparison.