Abstract:
A low-cost medical pump for ambulatory use provides reduced life components combined with a pump lockout enforcing a safe operating limit and preventing reuse after that limit is exceeded. An improved IV line clamp portion minimizes unsupported clamp structure length and provides a dual lock system preventing inadvertent clamp release.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Background of the Invention 
       [0001]    The present invention relates to compact infusion pumps for ambulatory use and in particular to an infusion pump design to reduce the costs of medical care delivery. 
         [0002]    Medical pumps, such as infusion pumps, are known for computer-controlled delivery of medication (henceforth medicaments) to patients over a period of time. Recently, battery-powered compact infusion pumps have become available that permit the patient to remain active (ambulatory), for example, in a home environment away from a clinic or hospital during the treatment. 
         [0003]    Typically the medicament is provided in a flexible bag that may be connected to an IV line which in turn attaches to a needle or port communicating with the patient. A nurse or other healthcare professional ministering to the patient receives the medicament, reviews the medicament description for correctness, and enters the desired dose and rate into the pump. The IV line is then installed in the portable pump and the assembly placed in a pack or other carrying apparatus that may be retained on the patient. The medicament may be delivered as the patient proceeds through normal life activities until the full dose is complete. The patient may then return the assembly to the nurse or health care professional who may provide a new bag of medicament and IV line, and may reprogram the pump for new treatment. 
         [0004]    Pumps suitable for ambulatory use can have high total operating costs driven in part by the cost of the pump itself which must meet exacting medical standards while being compact, lightweight, and ruggedized for portable use. The present inventors have determined further that the recovery rate of ambulatory pumps is historically low. Failure to recover the pump can occur when pumps are used in end-of-life treatment, or are damaged or lost in the field. 
         [0005]    High operating costs associated with ambulatory pumps necessarily limit the availability of the use of such medical devices to some individuals even though the pump could greatly improve the quality of care. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a cost-reduced ambulatory pump intended to increase availability and acceptability of ambulatory infusion. Lower cost is obtained by designing the pump with a component&#39;s short operating life specification, recognizing that the field operating life of such pumps is relatively short as biased by low pump recovery rates. Safety is ensured by incorporating absolute operating life limits into the pump that prevent the pump from being used in excess of its design life. In particular, maximum pump volume and maximum operating time may be monitored and used to block further use of the pump if that use would exceed safe operating limits. The pump also provides an improved IV line clamp system reducing the material costs of a significant mechanical component of the pump. 
         [0007]    Specifically, the invention provides an ambulatory infusion pump having a housing that holds an IV line support structure receiving an IV line set and a fluid pump communicating with the IV support structure to pump fluid through an IV line. The housing also includes an electronic computer commuting with the fluid pump and with a user interface for receiving programming commands from a clinician. During operation, the electronic computer monitors operation of the fluid pump to store at least one cumulative pump operation value indicating a cumulative operation of the fluid pump from a time of manufacture. The computer determines whether an amount of operation of the fluid pump necessary to implement received treatment protocol instructions will exceed the software-enforced service life of the ambulatory fluid pump reduced by at least one cumulative pump operation value, and if so, prevents further operation of the fluid pump. 
         [0008]    It is thus a feature of at least one object of the invention to provide look-ahead lockout of the programming of the pump, and when such programming is for a treatment protocol that would exceed the design pump operating life value, such design pump operating life is set to allow the safe use of durability components. 
         [0009]    The computer may further provide an indication to an individual providing the fluid pump operation instructions through the user interface that the pump has rejected the received treatment protocol instructions. 
         [0010]    It is thus a feature of at least one embodiment of the invention to clearly indicate the occurrence of the lockout, for example, so that it is not interpreted as the need for service, increasing pump-associated costs. 
         [0011]    The software-enforced service life and at least one cumulative pump operation value cannot be reset using the user interface. 
         [0012]    It is thus a feature of at least one embodiment of the invention to prevent unauthorized recycling of unsafe pumps or unsafe modification of the pump. 
         [0013]    The indication may be a visual display 
         [0014]    It is thus a feature of at least one embodiment of the invention to make use of a pre-existing user program element to provide an indication of pump lockout. 
         [0015]    The software-enforced service life and at least one cumulative pump operation value may be stored in nonvolatile memory. 
         [0016]    It is thus a feature of at least one embodiment of the invention to reduce the chance of inadvertent or intentional resetting of the service limits by removing power from the pump. 
         [0017]    The software-enforced service life and at least one cumulative pump operation value are stored so that they cannot be altered without disassembly of the pump to access internal electronic components. 
         [0018]    It is thus a feature of at least one embodiment of the invention to provide hardware barriers to reuse of the pump beyond its safe service life. 
         [0019]    The software-enforced service life and at least one cumulative pump operation value may be in units of volume of fluid pumped by the fluid pump. 
         [0020]    It is thus a feature of at least one embodiment of the invention to provide a measure of pump operation which reveals wear of the critical pump element. 
         [0021]    The software-enforced service life may be less than 100 liters. 
         [0022]    It is thus a feature of at least one embodiment of the invention to limit pump operation to permit the use of lower-cost pump elements subject to more rapid wear, for example, employing lower-cost motors, simpler bearings and less expensive material subject to wear. 
         [0023]    Alternatively or in addition, the software-enforced service life and at least one cumulative pump operation value may be units of time of operation of the fluid pump. 
         [0024]    It is thus a feature of at least one embodiment of the invention to provide a measurement of pump field life that reveals exposure of the pump to environmental contaminants and the aging of pump components regardless of wear. 
         [0025]    The software-enforced service life may be less than 1000 hours. 
         [0026]    It is thus a feature of at least one embodiment of the invention to limit pump operation to accommodate pump element contamination and material aging. 
         [0027]    The software-enforced service life and at least one cumulative pump operation value may be a combination of volume of fluid pumped by the fluid pump and time of operation of the fluid pump, and the program may compare both a volume of fluid to be pumped by the fluid pump against a volume of fluid of the software-enforced service life and compare a time of operation of the fluid pump against a time of operation of the ambulatory fluid pump, each service life reduced by respective cumulative pump operation values. When the amount of operation of the fluid pump necessary to implement the treatment protocol exceeds either adjusted software-enforced service lives, operation of the fluid pump is prevented. 
         [0028]    It is thus a feature of at least one embodiment of the invention to combine two measures of service life together to provide a more robust definition of the life of the pump. 
         [0029]    The program may further operate to allow entry through the user interface of a maximum flow rate for delivering medicament. 
         [0030]    It is thus a feature of at least one embodiment of the invention to permit other safeguards to be determined by the clinician programming the pump. 
         [0031]    The user interface may consist solely of manually operated electronic switches for the purpose of receiving user input. 
         [0032]    It is thus a feature of at least one embodiment of the invention to provide a cost-reduced control commensurate with the desired low-cost design of the pump. 
         [0033]    The computer program may further execute to require entry of a password sequence through the user interface for accepting or changing treatment protocol instructions. 
         [0034]    It is thus a feature of at least one embodiment of the invention to provide pump programming consistent with use in an unsupervised setting. 
         [0035]    The password sequence may make use of manually operated switches labeled for other purposes. 
         [0036]    It is thus a feature of at least one embodiment of the invention to provide for password-secured settings without the need for additional password input capabilities. 
         [0037]    In some embodiments, the housing may provide a generally rectangular volume having a an upper active portion and a lower clamp portion attachable to the upper active portion to hold the IV line therebetween extending along a longitudinal axis, and the upper active portion and lower clamp portion may releasably attach to each other at multiple points along opposed longitudinal interfacing edges. 
         [0038]    It is thus a feature of at least one embodiment of the invention to provide a more robust IV line clamping system by minimizing the unsupported span of the clamp portion. 
         [0039]    The upper active portion and lower clamp portion may releasably attach along a front longitudinal edge by inter-engaging sliding hooks and tabs wherein a front face of the housing exposes a slide operator movable in a first direction to slide the hooks, and a safety stop movable against a spring in a second direction different from the first direction to a state allowing sliding of the hooks. 
         [0040]    It is thus a feature of at least one embodiment of the invention to better prevent accidental disengagement of the clamp portion and IV line during ambulatory use. 
         [0041]    These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0042]      FIG. 1  is a simplified perspective view of the ambulatory pump assembly as provided to a patient; 
           [0043]      FIG. 2  is a front elevational view of the ambulatory pump showing inter-assembly of an upper active portion and lower clamp portion of the housing as separated by operation of dual release elements and showing a user interface comprising a display and manually operated buttons; 
           [0044]      FIG. 3  is a simplified block diagram of the electronics of the pump of  FIGS. 1 and 2  as controlled by internal electronic computer executing a stored program; 
           [0045]      FIG. 4  is a flowchart of the stored program of  FIG. 3  and the data structures used by that program; 
           [0046]      FIG. 5  is a first fragmentary cross-sectional view taken along  5 - 5  of  FIG. 1  and a second perpendicular cross-section aligned therewith showing operation of the dual release elements of  FIG. 2 ; and 
           [0047]      FIG. 6  is a perspective fragmentary view of the upper active portion and lower clamp portion as released showing various elements thereof. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0048]    Referring now to  FIG. 1 , an ambulatory pump  10  may operate in conjunction with a medicament bag  12  communicating with an IV line  14 . The medicament bag  12  may be, for example, a flexible plastic bag of the type used to hold IV solutions, and the IV line  14  provides a flexible tube allowing the flow of medicament from the medicament bag  12  and a patient connector  16  that may communicate with the patient through a needle or port or the like. The IV line  14  may include a bubble filter  17  for removing included air bubbles, limiting the need for air bubble sensing. 
         [0049]    The ambulatory pump  10  provides a two-part housing having an upper electronics portion  18  that may attach to a lower clamp portion  20  to receive the IV line  14  therebetween along a longitudinal axis  22  being generally the longest dimension of the housing of the ambulatory pump  10 . As so received, the ambulatory pump  10  may pump liquid through the IV line  14  by peristaltic action. 
         [0050]    In one embodiment, the ambulatory pump  10  is constructed to weigh less than a half pound and preferably less than 1.5″×2″×5″ so as to be easily carried by the patient, for example, in a pouch  24  also sized to receive the medicament bag  12 . 
         [0051]    Referring now to  FIG. 2 , the housing of the upper active portion may present on its front surface a user interface  26  comprising, for example, a liquid crystal type display  28  for displaying symbols and alphanumeric characters under computer control. The user interface  26  also provides multiple membrane switch pushbuttons  30  that may be activated by a user. Generally, the pushbuttons include a limited number of controls including, in one embodiment, run and stop pushbuttons  30   a  and  30   b , respectively, that will stop and start operation of the pump as will be described below; a rate pushbutton  30   c  allows setting of the maximum pumping rate of the ambulatory pump  10  in milliliters per hour by cycling through menu standard rates with each push (?). The pushbuttons also include a “volume to be infused” pushbutton  30   d  allowing user control of the maximum volume to be infused during a treatment protocol, also by cycling through standard settings with each push, as well as an information pushbutton  30  allowing the display of detailed information about the pump including remaining pump life (?). Pushbutton  30   f  allows the unit to be turned on and off to conserve power. A bolus pushbutton  30  allows short operation of the pump to deliver medicament in fixed patient controlled bolus quantities (?). 
         [0052]    A lower edge of the upper electronics portion  18  provides for a clamp release slide  32  as will be described below and safety lock  34  that must be simultaneously activated to remove the lower clamp portion  20 . 
         [0053]    Referring now to  FIG. 3 , the ambulatory pump  10  may include a microcontroller  36  being an electronic computer having a self-contained nonvolatile memory  38  holding an operating program  40  and necessary storage variables as will be described below. The nonvolatile memory may comprise, for example, flash memory and/or read only memory, or other similar nonvolatile memory as context requires, which may store data values to be retained even in the absence of electrical power. 
         [0054]    The microcontroller  36  also provides various inputs and output lines communicating, for example, with the display  28  for providing display information thereon and various pushbuttons  30  for receiving data related to their activation by user. In addition, the microcontroller  36  may provide control lines to the pump assembly  42  having, for example, an internal DC electric motor (not shown) operating through a gear system to activate peristaltic plunger elements  44  that may press against the contained IV line  14  to push fluid therethrough. As is understood in the art, generally the peristaltic plunger elements  44  extend in an undulating serpentine fashion to compress and release the tubing thereby moving fluid therethrough. 
         [0055]    The microcontroller  36  may also communicate electrically with various sensors. For example, upstream and downstream pressure sensors  46  and  48  which can be used to ensure proper operation of the pump by detecting abnormal pressures. Generally each of the pressure sensors  46  and  48  may provide a spring-loaded plunger that presses into the outer wall of the IV line  14  to sense pressure. This through-wall measurement avoids the need for separate connections to the fluid-contacting pressure sensor and the problems of sterilization of a fluid-contacting pressure sensor. In such a through-tubing sensing system, the spring-loaded plunger deforms a portion of a wall of the IV line  14  as held against a backstop. Under a known spring biasing force, the amount of deflection of the wall may be measured to deduce internal pressure. Generally, lower pressures of the contained medicament will allow greater deflection of the wall of the IV line  14  and higher pressures of contained medicament will allow less deflection of the wall of the IV line  14 . The system may be calibrated for a particular material of the IV line  14 . 
         [0056]    All electrical components in the upper electronics portion  18  maybe supplied with power by a contained storage battery  49  that may provide its power directly or through standard power processing circuits such as regulators and the like. 
         [0057]    Referring now to  FIG. 4 , during normal operation, a clinician will enter a total volume to be infused  52  and an infusion rate  54 , as shown by process block  50 , by using the user interface  26  shown in  FIG. 2 . In order to prevent tampering or inadvertent change in these values, their entry is accomplished through a password which must be entered first, indicated by process block  56 . The password may employ a predetermined sequence of pressing of the pushbuttons  30  (for example, after the unit is turned on but before it is programmed) such as pressing the run pushbutton  30   a  once and the stop pushbutton  30   b  twice. Such use of the pushbuttons  30  may be without regard to the actual labels of the button as, in this example, “run” and “stop”. 
         [0058]    The total volume to be infused  52  and the infusion rate  54  are then used to compute a total infusion time  58  that may, but need not be, a continuous time period but which may also be a cumulative time necessary for the infusion, contemplating that the infusion may be started and stopped by the patient. The total volume to be infused  52  and the infusion time  58  represent received protocol instructions (either direct or indirect) from a clinician describing the intended operating limits of the fluid pump in a treatment protocol. 
         [0059]    At succeeding process block  60 , the total volume to be infused  52  is compared against a preset software-enforced volume limit  62  of the pump  10  after the software-enforced volume limit  62  is reduced by the cumulative pumped volume  66 . The cumulative pumped volume  66  is set to zero when the ambulatory pump  10  is manufactured and then increases with operation of the pump assembly  42 . Similarly, the total infusion time  58  is compared against a preset software-enforced time limit  64  as reduced by the cumulative pump operation time  68 . The cumulative pump operation time is also set to zero when the ambulatory pump  10  is manufactured and then increases with operation of the ambulatory pump  10  determined from activation of the on pushbutton  30   f  not necessarily including activation of the pump assembly  42 . The net effect of process block  60  is to see if the intended treatment protocol can be performed before the service life of the pump has been exceeded. 
         [0060]    If either the use-adjusted, software-enforced volume limit  62  or software-enforced time limit  64  have been exceeded, as determined at decision block  70 , the program  40  proceeds to process block  72  and provides a warning that the treatment protocol may not be implemented as displayed on the display  28  of  FIG. 2 . The program  40  then returns the process block  50  without operation of the pump assembly  42  and a new password and new values must be entered if operation is to be continued. Decision block  70  may also check for adequate remaining battery energy for the protocol using an internal time-to-ampere-hour conversions based on the current drain of the ambulatory pump and comparing that against the estimated total ampere-hours of the battery. 
         [0061]    If at decision block  70 , the treatment protocol may be performed within the service limits of the pump  10 , then the program proceeds to decision block  74  and may begin operation as indicated by process block  76 , when the run pushbuttons  30   a  is pressed. The program loops until the run pushbutton  30   a  is pressed or the unit is switched off. 
         [0062]    It will generally be understood that except through operation of the program  40  executing on the microcontroller  36 , the values  66 ,  68 ,  62 , and  64  contained in memory  38  may not be changed and the program  40  does not allow these values to be changed by the operator through the user interface  26 . More generally, these values may not be changed by removing power from the ambulatory pump  10  (e.g. removing battery  49  shown in  FIG. 3 ) and generally require disassembly of the pump  10  to obtain direct access to the pin structure of the microcontroller  36  and specialized equipment to access the memory directly if that is even possible. It is contemplated that these values may be stored in a way that cannot be changed without destruction of the ambulatory pump  10  or microcontroller  36 . 
         [0063]    The operation of the pump at process block  76  will normally monitor the pressure sensors  48  and  46  to ensure there is no upstream or downstream occlusion of medicament flow. Any such obstruction will cause a ceasing of the operation of the pump assembly  42  which may be reactivated after correction by the user. During process block  76 , pump flow-rate is controlled by controlling the speed of the pump assembly  42  in open loop fashion according to the entered infusion rate  54 . During operation, the pump&#39;s  76  accumulated time and pumping volume per process block  77  are used to update cumulative pumped volume  66  and cumulative pump operation time  68 . 
         [0064]    Periodically during operation of the pump at process block  76  (or enforced on an interrupt basis), decision block  78  may be polled to see if the stop pushbutton  30   b  has been pressed in which case the pump assembly  42  stops and the program  40  returns to decision block  74 . 
         [0065]    If the stop pushbutton  30   b  of decision block  78  has not been pressed, the program  40  proceeds to decision block  80  to determine whether the total volume through the ambulatory pump  10  during this treatment protocol has reached the total volume to be infused  52 . If so, the program  40  loops back to process block  50 , but if not the program returns to process block  76 . 
         [0066]    It should be noted that the updating of the cumulative values per process block  77  looks at actual rather than estimated hours and volumes pumped in contrast to the calculation of process block  60 . 
         [0067]    Referring now to  FIGS. 2 and 6 , the upper surface of the lower clamp portion  20  may provide for a shallow tray having upstanding peripheral longitudinally-opposed end walls  90  and  92 , these walls separating the opposed upstanding peripheral longitudinally-extending sidewalls  94  and  96 . The end walls  90  may include notches receiving retention bushings  98   a  and  98  formed in the IV line  14  to prevent longitudinal movement of the IV line  14  with respect to the lower clamp portion  20  along the longitudinal axis  22 . 
         [0068]    Between the bushings  98   a  and  98   b , the material of the IV line  14  may be replaced with a silicon material that is softer and more conducive to peristaltic pumping and through-wall pressure sensing. The portion of the IV line  14  within the tray of the lower clamp portion  20  may be held by guides  100  which form notches to align and retain the IV line  14  with the peristaltic plunger elements  44  and the downwardly extending operators of the pressure sensors  46  and  48  held in the bottom wall  101  of upper electronics portion  18 . The guides  100  may also provide for backstops holding the IV line  14  against the pressure of the downwardly extending operators of the pressure sensors  46  and  48  and the peristaltic plunger elements  44 . 
         [0069]    The IV line  14  may pass through a spring bias clamp element  102  that automatically clamps the IV line  14  when the lower clamp portion  20  is separated from the upper electronics portion  18 . 
         [0070]    Rear sidewall  96  includes upwardly extending open hinge collars  104  spaced along its edge that may attached to and hinge about hinge pin  106  supported at a rear edge of the bottom wall  101  of the upper electronics portion  18 , spaced below the bottom wall  101  and generally parallel to the longitudinal axis  22 . 
         [0071]    Front sidewall  94  includes longitudinally-extending tabs  107  that may be engaged by corresponding hooks  108  extending down from the front edge of the bottom wall  101  of the upper electronics portion  18  and activated by release slide  32  as will be described to move generally along the longitudinal axis  22 . When the lower clamp portion  20  is attached by the interconnection of open hinge collars  104  and hinge pin  106  and pivoted upward toward the bottom  101 , the hooks  108  may pass over and attach to the tabs  107  to retain the upper electronics portion  18  and lower clamp portion  20  together with the IV line  14  in proper alignment and clamp therebetween. 
         [0072]    By attaching the lower clamp portion  20  to the upper electronics portion  18  at multiple points across the narrower dimension of the lower clamp portion  20 , reduced flexure of the lower clamp portion  20  may be obtained (as opposed to attachment at end walls  92  and  90 ) against the forces of the peristaltic plunger elements  44  and pressure sensors  46  and  48  providing better alignment against minor tolerances and reduced flexure caused by the reduced unsupported span of the polymer material of the lower clamp portion  20 . This allows reduced material costs for the lower clamp portion  20  and provides increased accuracy, for example, in the pressure sensing. 
         [0073]    Referring now to  FIG. 5 , the downwardly extending hooks  108  may be attached to a common driver bar  110  that is longitudinally spring biased by a spring  112  into engagement with the tabs  107  tending to hold the lower clamp portion  20  against the upper electronics portion  18 . The bar  110  may communicate with release slide  32  which may be pressed rightward against the biasing spring  112  to allow release of the hooks  108  from the tabs  107 . Leftward motion of the bar  110  is only possible, however, when safety lock  34  is pressed inward against biasing spring  112  in a direction perpendicular to the longitudinal axis  22  allowing a longitudinally-extending opening  114  in the safety lock  34  to align with the driver bar  110  permitting rightward movement of an extension of the common driver bar  110  through the longitudinally-extending opening  14 . Because the motion of the clamp release slide  32  and safety lock  34  are in different directions and they are located in separated positions, accidental release of the lower clamp portion  20  is greatly reduced. 
         [0074]    Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. Indication is used herein to mean any type of sense to indication including an audio alarm, visual display or other computer-controlled activation (motor buzz, etc.) 
         [0075]    When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
         [0076]    References to “a microprocessor” and “a processor” or “the microprocessor” and “the processor,” can be understood to include one or more microprocessors or other types of computers, gate arrays or the like that can execute programs and communicate with each other. Furthermore, references to memory, unless otherwise specified, can include one or more processor-readable and accessible memory elements and/or components that can be internal to the processor-controlled device, external to the processor-controlled device, and can be accessed via a wired or wireless network. The term manual pushbuttons means buttons that may be operated by finger touch or the like including touchscreen and passive switch and mechanical switch. 
         [0077]    It will be appreciated that the look-ahead operation of the ambulatory pump  10  described herein is consistent both with anticipatory locking of the pump so that the pump does not exceed the service values, as well as setting the service values to a value below the actual longest desired service value by amount of the typical treatment protocol and allowing the treatment protocol to exceed the service value once, and then locking out pump. In this latter case, the pump lockout anticipates that the next treatment protocol would exceed the remaining operating time or volume (which is a negative value) and need not actually accept a new protocol. 
         [0078]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications, are hereby incorporated herein by reference in their entireties.