Abstract:
An intravenous (IV) pump is disclosed. The IV pump includes a housing, a permanent magnet, an electromagnet, and a switch configured to selectably energize or de-energize the electromagnet. The permanent magnet generates a magnetic field and the electromagnet, when energized, generates a magnetic field that approximately cancels the magnetic field of the permanent magnet.

Description:
BACKGROUND 
     1. Field 
     The present disclosure generally relates to administration of medical fluid by infusion and, in particular, relates to a system and method of pumping infusion fluids. 
     2. Background 
     Infusion pumps have become commonplace within the healthcare world as a way to precisely administer intravenous (IV) fluids. Use of a pump in place of a simple roller clamp with an elevated fluid container to control the flow of the IV fluid allows more accurate and consistent control of the rate of delivery of the fluid to the patient. 
     Infusion sets designed for use with IV pumps may have a pumping chamber incorporated into the set, wherein the pumping chamber fits into a compartment in the IV pump. After completion of the infusion treatment, removal of the IV set and, in particular, the pumping chamber from the IV pump can be difficult. Some IV pumps use mechanical retention features to hold the pumping chamber in the proper position within the pump and provide an integrated lever that the nurse may use to pry the pumping chamber free from the pump. With such prying, however, there is an increased risk of damaging the IV set and consequently exposing the nurse and the patient to the content of the IV set. 
     SUMMARY 
     The IV set release system disclosed herein enables a user to remove an IV set from an IV pump without risk of damaging the IV set and potentially exposing the nurse or patient to the medication or other medical fluid. By reducing the retention force at the time of removal, this system provides improved retention during operation while also providing for safe and easy removal of the IV set at the conclusion of treatment. 
     An IV pump is disclosed that includes a housing, a permanent magnet attached to the housing, and an electromagnet attached to the housing. The permanent magnet generates a magnetic field and the electromagnet generates, when energized, a magnetic field that approximately cancels the magnetic field of the permanent magnet. The IV pump also includes a switch that is coupled to the electromagnet and configured to selectably energize or de-energize the electromagnet. 
     In another embodiment, an IV pump is disclosed that includes a housing and an attached electromagnet. The electromagnet generates, when energized, a magnetic field of either a first polarity or a second polarity, wherein the second polarity is opposite the first polarity. The IV pump also includes a switch that is coupled to the electromagnet and configured to energize the electromagnet to selectably generate a field of either the first polarity or the second polarity. 
     In another embodiment, an IV pump is disclosed that includes a housing, a first permanent magnet fixedly attached to the housing and a second permanent magnet movably attached to the housing, the second permanent magnet having a first position and a second position. The first permanent magnet generates a first magnetic field and the second permanent magnet generates a second magnetic field. The second magnetic field augments the first magnetic field when the second permanent magnet is in the first position and opposes the first magnetic field when the second permanent magnet is in the second position. 
     In another embodiment, an IV system is disclosed that includes an IV set with an attached ferromagnetic element, an IV pump that has a housing configured to accept a portion of the IV set, a permanent magnet attached to the housing, and an electromagnet attached to the housing. The permanent magnet attracts the ferromagnetic element of the IV set, and the electromagnet generates, when energized, a magnetic field that approximately cancels the magnetic field of the permanent magnet. The IV pump also includes a switch coupled between a power source and the electromagnet, the switch configured to energize and de-energize the electromagnet. 
     In another embodiment, an IV pump is disclosed that includes a housing, a magnetic attractive feature coupled to the housing wherein the magnetic attractive feature is configured to attract a pumping cassette comprising a magneto-sensitive material, and a magnetic cancellation feature coupled to the housing, wherein the magnetic cancellation feature is configured to controllably cancel the attraction of pumping cassette by the magnetic attractive feature. 
     A method of releasing an IV pump cassette from an IV pump is disclosed. The method includes the steps of substantially canceling a magnetic attractive force between a portion an IV pump and a portion of an IV set when the IV pump and IV set are in an attracted state, and removing the IV set from the IV pump when the magnetic attractive force is substantially cancelled. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide further understanding and are incorporated in and constitute a part of this specification, illustrate disclosed embodiments and together with the description serve to explain the principles of the disclosed embodiments. In the drawings: 
         FIG. 1  depicts a patient receiving medical fluid through an intravenous line using an IV pump. 
         FIG. 2  illustrates attachment of an infusion cassette to the IV pump of  FIG. 1  according to certain embodiments of the present disclosure. 
         FIG. 3  is a cross-section of a portion of the IV pumping module of  FIG. 2  showing an IV cassette  24  having a magneto-sensitive element and an IV pump having a permanent magnet according to certain embodiments of the present disclosure. 
         FIGS. 4A and 4B  are cross-sections depicting an IV pumping module having a permanent magnet and an electromagnet according to certain embodiments of the present disclosure. 
         FIGS. 5A and 5B  are cross-sections showing an IV pump having two permanent magnets according to certain embodiments of the present disclosure. 
         FIG. 6  is a cross-section showing an IV pump having a spring element to assist in removing a cassette according to certain embodiments of the present disclosure. 
         FIG. 7  is a cross-section showing another embodiment of an IV pump configured to assist in removing a cassette according to certain embodiments of the present disclosure. 
         FIGS. 8A-8B  are perspective views of a pumping module having a receiver to catch a cassette during removal according to certain embodiments of the present disclosure. 
         FIG. 9  is a flowchart depicting the process of releasing a cassette from an IV pumping module according to certain embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     IV pumps are frequently configured to accept a portion of a disposable IV set and to provide a pumping action through manipulation of this portion of the IV set so that the permanent IV pump mechanisms are not exposed to the fluid being pumped. This avoids the risk of exposure of the healthcare provider to the medication or blood product that is being administered as well as reducing the risk of infection of the patient. After completion of treatment, the disposable IV set is removed from the IV pump and discarded. Since the pumping performance may be improved if the IV set is strongly held to the IV pump. Current designs may make it more difficult to remove the IV set from the IV pump without damaging the IV set. 
     Certain exemplary embodiments of the present disclosure include a system that comprises an IV set that incorporates a ferromagnetic element and an IV pump that is configured to first attract the ferromagnetic element to a defined position and retain the IV set during operation, and then to reduce the attractive force to release the IV set at the completion of treatment. In certain embodiments, a magnetic element replaces the ferromagnetic element and the IV pump includes an electromagnet that applies a force to the magnetic element to further assist in removing the IV set. 
     In the following detailed description, numerous specific details are set forth to provide a full understanding of the present disclosure. It will be apparent, however, to one ordinarily skilled in the art that embodiments of the present disclosure may be practiced without some of the specific details. In other instances, well-known structures and techniques have not been shown in detail so as not to obscure the disclosure. 
       FIG. 1  depicts a patient  10  receiving medical fluid through an IV set  18  using an IV pump  12 . The fluid is provided, in this example, in a flexible bag  14  that is commonly hung above the IV pump  12  to provide a positive pressure at the pump  12 . The IV pump  12  shown herein has a control unit  16  and an attached pumping module  20 . The IV set  18  connects the fluid container  14  to the patient  10 , and passes through the pumping module  20 . The flow rate of the medical fluid is controlled by the pumping action of pumping module  20  under the control of control unit  16 . In some configurations of IV pumps, the pumping module  20  is integrated with the control unit  16 . The control unit  16  can also be located remotely from the pumping module  20  in certain embodiments. Hereinafter, the use of the phrase “pumping module” refers to the pumping portion of any IV pump, whether integrated or separate. 
       FIG. 2  illustrates attachment of an infusion cassette  24  to the IV pump  20  of  FIG. 1  according to certain embodiments of the present disclosure. The term “cassette” is used herein to refer to a portion of an IV set  18  that is configured to be attached or positioned within a portion of the IV pump  20  during use. This cassette  24  may comprise rigid elements or may be completely made of flexible materials, or a combination of rigid and flexible materials. The cassette  24  comprises a magneto-sensitive element  26  comprising a magneto-sensitive material, i.e. a material that is attracted by a magnetic field. This magneto-sensitive material may or may not be permanently magnetized. This magneto-sensitive material is incorporated into the structure of magneto-sensitive element  26  in this embodiment. In other embodiments, the magneto-sensitive material is applied as a coating to the surface of magneto-sensitive element  26 . The pumping module  20  has a recess  28  that is configured to accept and retain cassette  24  such that pumping elements (not shown) of pumping module  20  can manipulate cassette  24  to pump fluid. Pumping module  20  further comprises a magnetic actuator  30  configured to attract the attractive element  20  of cassette  24  and provide at least a portion of the retention force to retain cassette  24  within the recess  28 . Although only a single magneto-sensitive element  26  and magnetic actuator  30  are depicted in  FIG. 2 , certain embodiments of the present disclosure have a plurality of such pairs. 
       FIG. 3  is a cross-section of a portion of the IV pumping module  20  of  FIG. 2  showing an IV cassette  24  having a magneto-sensitive element  26  and an IV pump  20  having a permanent magnet  30  according to certain embodiments of the present disclosure. It can be seen that the permanent magnet  30  is configured to attract and retain the magneto-sensitive element  26 , thereby attaching and retaining the cassette  24  to the pumping module  20 . This same retention feature, however, increases the effort required to remove the pumping cassette  24  from pumping module  20  after treatment is complete. It is desirable to reduce this retention force when it is time to remove pumping module  24 . 
       FIGS. 4A and 4B  are cross-sections showing an exemplary embodiment of an IV pumping module  20  having a permanent magnet  30  and an electromagnet  40  according to certain embodiments of the present disclosure. Like the pumping module  20  of  FIG. 3 , the pumping module  20  of  FIG. 4A  has a permanent magnet  30  that attracts and retains the magneto-sensitive element  26  of the cassette  24 . In addition, the pumping module  20  of  FIG. 4A  includes an arrangement that helps to release the cassette  24  from pump module  20 . This release aids the nurse in removing the cassette  24  with less risk of rupturing the cassette  24  and exposing the medical fluids to the nurse and patient. 
     The release arrangement includes an electromagnet  40  that, in the depicted embodiment of  FIG. 4A , is wrapped around the permanent magnet  30  such that the magnetic fields created by electromagnet  40  and permanent magnet  30  are approximately coincident. Electromagnet  40  is powered by a power source  44 , represented herein as a battery. In certain embodiments, power source  44  is an external source of electrical power. A switch  46  is coupled between power source  44  and electromagnet  40  such that switch  46  controls the flow of current through the windings  48  of electromagnet  40 . 
       FIG. 4A  depicts the cassette  24  magnetically attached to the pumping module  20  and, thus, in position to be acted upon by the pumping module  20  to pump fluid. Permanent magnet  30  is located with one of its north-south poles flush with the surface of recess  28  at a position that corresponds to the location of a magneto-sensitive element  26  of cassette  24  when the cassette  24  is properly located in recess  28 . In this example, the windings  48  of electromagnet  40  are shown in cross-section as circles with dots in the center for wire sections having current flowing toward the viewer and with crosses in the center for wire sections having current flowing away from the viewer. In  FIG. 4A , switch  46  is open and the power source  44  is not connected to the electromagnet  40  and, therefore, no current is flowing through the windings  48 . The permanent magnet  30  generates a magnetic field  42 , shown as a series of broken lines representing the magnetic field lines. Magneto-sensitive element  26  of cassette  24  has been attracted by magnetic field  42  such that cassette  24  is attached and retained in the recess  28  of the pumping module  20 . 
       FIG. 4B  depicts a configuration of the IV pump  20 , for example, following completion of a pumping operation. Switch  46  is closed and power source  44  is connected to the electromagnet  40  and, therefore, current is flowing through the windings  48 . The direction that current flows will govern the polarity of the field that is generated. Depending on the orientation of the permanent magnet  30 , shown with the north pole on the left in  FIG. 4A , the current is controlled to flow in a specified direction through the windings  48  in order to generate a magnetic field that opposes the magnetic field generated by permanent magnet  30 , with the strength of the two fields being approximately equal. When the two fields are of opposite polarity and equal strength, as shown in the configuration of  FIG. 4B , there is no net magnetic field and therefore no attractive force applied to magneto-sensitive element  26 . As the magnetic field  42  provides the only retention force, in this example, the cancellation of the magnetic field  42  by the electromagnet  40  allows the cassette  24  to slip out of the recess  28  by gravity, for example, as depicted by the arrow in  FIG. 4B . Alternately, a nurse can easily remove the cassette  24  by hand without danger of rupturing the cassette  24 . 
       FIGS. 5A and 5B  are cross-sections showing an exemplary embodiment of an IV pump  20  having a permanent magnet  30  and a permanent magnet  50  according to certain embodiments of the present disclosure. Permanent magnet  50  is coupled to a turntable  54  that can rotate at least 180 degrees about axis  56 . Turntable  54  is coupled to a rotary actuator  58  that has a first position such that the north pole of permanent magnet  50  is aligned with the north pole of permanent magnet  30  and a second position such that the north pole of permanent magnet  50  is aligned with the south pole of permanent magnet  30 . The rotary actuator  58  is controlled to move between the first and second positions. Other arrangements for rotatably mounting a magnet, such as embedding the magnet in a disk, and moving the magnet from one position to a second position, such as with a solenoid or motor, will be known to those of ordinary skill in the art. 
     In the position shown in  FIG. 5A , rotary actuator  58  is in the first position and, consequently, the poles of permanent magnet  50  are aligned with those of permanent magnet  30 , producing a combined magnetic field  52 . As with the configuration of  FIG. 4A , magnetic field  52  attracts magneto-sensitive element  26  and attaches and retains cassette  24  in recess  28  of pumping module  20  so that cassette  24  can be used in a pumping operation. 
     In  FIG. 5B , rotary actuator  58  has moved to the second position and, consequently, the north pole of permanent magnet  50  is adjacent to the south pole of permanent magnet  30 . In this configuration, the magnetic fields of permanent magnets  30  and  50  are tightly coupled as shown with the magnetic field  52  being totally within permanent magnets  30  and  50  and, as a result, there is no external field. In the absence of a net external magnetic field, there is no attraction force applied to magneto-sensitive element  26  and cassette  24  slips out of the recess  28 , as depicted by the arrow in  FIG. 5B . 
       FIG. 6  is a cross-section showing an embodiment of an IV pump  20  having a biasing element  60  to assist in removing the cassette  24  according to certain embodiments of the present disclosure. In the embodiment of  FIG. 6 , the biasing element is a helical spring, although other types of biasing element can also be used, such as elastically compressible foam or a flexible cantilever. In this example, the pumping module  20  comprises a permanent magnet  30  and an electromagnet  40  that are configured as in  FIG. 4A  to attract and retain the magneto-sensitive element  26  of the cassette  24 . Biasing element  60  is in compression when the cassette  24  is fully seated in the recess  28 , with a compressive force that is small compared to the force applied by the permanent magnet  30 . When the electromagnet  40  is energized, the magnetic field of the permanent magnet  30  is approximately cancelled, and the compressive force of the biasing element  60  is larger than the residual force of the two opposing magnetic fields. Thus, the force applied by biasing element  60 , indicated by the arrow, is sufficient to force the cassette  24  out of the recess  28 , further assisting in the removal of cassette  24  from the pumping module  20 . 
       FIG. 7  is a cross-section showing an embodiment wherein the cassette  24  has a magnetic element  62  and the electromagnet  40  of the pumping module  20  can apply force to the magnetic element  62  to assist in removing the cassette  24  according to certain embodiments of the present disclosure. Cassette  24  is retained in pumping module  20  by the magnetic field generated by electromagnet  40 , when the polarity of the magnetic field is such that the poles are in the same direction as those of the magnetic element  62 , i.e. the south pole of the magnetic field of the electromagnet field  64  is adjacent to the north pole of the magnetic element  62 . However, in the situation illustrated in  FIG. 7 , the direction of the current flowing through the windings of electromagnet  50  is such as to create a magnetic field  64  that repulses magnetic element  62 , i.e. the north poles of the two fields are adjacent, as shown in  FIG. 7 . This creates a force, indicated by the arrow, pushing cassette  24  out of recess  28 , assisting in the removal of cassette  24  from the pumping module  20 . Hence, the current can be made to flow in the electromagnet  40  to cause attraction and retention of the cassette  24 , and also in a direction to cause repulsion and ejection of the cassette  24 . 
       FIGS. 8A-8B  are perspective views of an embodiment of a pumping module  20  having a sloped receiver  70  under the recess  28  to catch the cassette  20  when removing the cassette  20  according to certain embodiments of the present disclosure.  FIG. 8A  depicts the pumping module  20  of  FIG. 4A  with the electromagnet  50  (not visible) de-energized such that an attractive force is applied by the permanent magnet  30  to magneto-sensitive element  26  and the cassette  24  is retained in recess  28 . A sloped receiver is attached to the pumping module  20  at the bottom, having a slot  72  configured such that the tubing of IV set  18  passes through the slot while the IV pump  12  is in operation. In  FIG. 8B , the electromagnet  50  has been energized, cancelling the magnetic field of permanent magnet  30 , and therefore cancelling the attractive force applied to magneto-sensitive element  26 . Cassette  24  is therefore released and slides out of recess  28 , whereupon cassette  24  is caught by sloping receiver  70 . In this example, slot  72  captures the tubing of IV set  18  and guides the cassette  24  into the sloping receiver  70 . This enables the nurse to press the switch  46 , or other control element of IV pump  12 , that energizes electromagnet  50  with one hand without requiring her to have her other hand ready to catch the released cassette  24 . This simplifies the workflow as well as avoids the risk of the cassette  24  becoming damaged or contaminated by falling on the floor. 
       FIG. 9  is a flowchart depicting the process of releasing a cassette  24  from an IV pumping module  20  according to certain embodiments of the present disclosure. In step  105 , the magnetic attractive force between a portion of an IV set  18  and a portion of an IV pump  12  is cancelled by one or more of the arrangements disclosed herein. In step  110 , the IV set  18  is removed from the IV pump  12 . The portion of the IV set  12  is, in this example, the cassette  24  described in at least  FIG. 4A  herein. 
     It can be seen that the disclosed embodiments of the retention and release mechanisms provide a secure and releasable attachment of a cassette of an IV set to a pumping module of an IV pump. By actively cancelling the magnetic field and therefore reducing the retention force, the amount of effort required to remove the cassette is decreased, reducing the risk of damage to the cassette and the risk of injury to the nurse and patient. This releasable attachment may be accomplished through a plurality of combinations of permanent magnets and electromagnets. 
     The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. While the foregoing has described what are considered to be the best mode and/or other examples, it is understood that various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” Unless specifically stated otherwise, the terms “a set” and “some” refer to one or more. Pronouns in the masculine (e.g., his) include the feminine and neuter gender (e.g., her and its) and vice versa. Headings and subheadings, if any, are used for convenience only and do not limit the invention. 
     It is understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged. Some of the steps may be performed simultaneously. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
     Terms such as “top,” “bottom,” “front,” “rear” and the like as used in this disclosure should be understood as referring to an arbitrary frame of reference, rather than to the ordinary gravitational frame of reference. Thus, a top surface, a bottom surface, a front surface, and a rear surface may extend upwardly, downwardly, diagonally, or horizontally in a gravitational frame of reference. 
     The term “magneto-sensitive” is used herein to refer to a material that is attracted by a magnetic field and may or may not be magnetized. Example of magneto-sensitive materials include ferromagnetic materials such as iron, some steels, nickel, and cobalt and ferrites such as barium ferrite BaO:6Fe 2 O 3 . Iron, for example, may be magnetized or unmagnetized. Unmagnetized iron is attracted by a magnetic field but does not generate its own magnetic field. Pairs of materials will be attracted to each other if the first material is magnetized and the second material is a magneto-sensitive material, which implies that the second material may be magnetized as well. Two non-magnetized magneto-sensitive materials will not be attracted to each other. 
     A phrase such as an “aspect” does not imply that such aspect is essential to the subject technology or that such aspect applies to all configurations of the subject technology. A disclosure relating to an aspect may apply to all configurations, or one or more configurations. A phrase such as an aspect may refer to one or more aspects and vice versa. A phrase such as an “embodiment” does not imply that such embodiment is essential to the subject technology or that such embodiment applies to all configurations of the subject technology. A disclosure relating to an embodiment may apply to all embodiments, or one or more embodiments. A phrase such an embodiment may refer to one or more embodiments and vice versa. 
     The word “exemplary” is used herein to mean “serving as an example or illustration.” Any aspect or design described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects or designs. 
     All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.” Furthermore, to the extent that the term “include,” “have,” or the like is used in the description or the claims, such term is intended to be inclusive in a manner similar to the term “comprise” as “comprise” is interpreted when employed as a transitional word in a claim.