Abstract:
A bubble free, self-priming IV set for use in the administration of liquids includes a coupling assembly for attaching the delivery system to a source of liquid and includes a coupling membrane for controlling the flow of liquid and air through the coupling assembly. The system also includes a drip chamber for receiving liquid through the coupling assembly, the drip chamber having a membrane for preventing air from leaving the drip chamber. A self leveling port is disposed within a wall of the drip chamber, the port being permeable to air, but impermeable to liquid. Finally, a patient conduit is in fluid communication with the drip chamber and further comprises a flow control plug disposed at the distal end of the conduit. The flow control plug is permeable to air but impermeable to liquid. Use of this system allows a clinician to attach a source of fluid to a patient without significant intervention, while the system self primes.

Description:
CROSS-REFERENCED RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part application of co-pending application Ser. No. 11/205,236 filed Aug. 16, 2005 and entitled “Bubble Free-Self Primed IV Set,” which in turn claims the benefit of U.S. Provisional Application No. 60/654,705, filed Feb. 18, 2005. This application is also a continuation-in-part application of co-pending application Ser. No. 10/768,760 filed Jan. 29, 2004 and entitled “Intravenous Delivery System.” Each of the above-referenced applications is incorporated herein by this reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates generally to tubing sets used in the administration of liquids to a patient that are commonly referred to as intravascular (“IV”) sets and more particularly concerns air bubble free (hereinafter referred to as simply “bubble free”), self-priming IV sets. An IV set is used broadly herein to describe, among other sets, tubing sets used in the arterial, intravenous, intravascular, peritoneal, and non-vascular administration of fluid. Of course, one of skill in the art may use IV set to administer fluids to other locations within a patient&#39;s body than those listed.  
         [0003]     One common method of administering fluids into a patient&#39;s blood flow is through an IV set. An IV set is an apparatus that generally includes a connector for connection to a fluid reservoir, a drip chamber used to determine the flow rate of fluid from the fluid reservoir, tubing for providing a connection between the fluid reservoir and the patient, and a connector for attachment to a catheter that may be positioned intravenously in a patient. An IV set may also include a Y-connector or other access point or device that allows for the piggybacking of IV sets and for the administration of medicine from a syringe into the tubing of the IV set.  
         [0004]     It is good practice to remove air from IV sets which access a patient&#39;s blood flow. While this concern is critical when accessing arterial blood, it is also a concern when accessing the venous side. Specifically, if air bubbles are allowed to enter a patient&#39;s blood stream while receiving the intravenous administration of liquids, the air bubbles can form an air embolism and cause serious injury to a patient.  
         [0005]     In a majority of adults, the right atrium and the left atrium are completely separated from each other so that the blood and air bubbles are moved from the right atrium, to the right ventricle, and then to the lungs where the air bubbles may be safely vented. The bubble free blood is then returned to the left atrium, where the blood is moved to the left ventricle and then sent as arterial blood flow throughout the body.  
         [0006]     However, in infants and in a small portion of the adult population, the right atrium and left atrium are not completely separated. Consequently, air bubbles can move directly from the right atrium into the left atrium and then be dispersed throughout the body. As a result, these air bubbles may cause strokes, tissue damage, and/or death. Therefore, it is important to prevent air bubbles from entering a patient&#39;s blood stream.  
         [0007]     In spite of the importance of removing air bubbles while priming an IV set for use in the intravenous administration of liquids, the complete removal of air bubbles can be a time consuming process. The process may also lead to contamination of the IV set by inadvertently touching a sterile end of the IV set. Typically, when an IV set is primed, a clamp is closed to prevent liquid from moving from a drip chamber through the tubing. The IV set is then attached to an IV bag or bottle. Once attached, the drip chamber, which is typically made of a clear flexible plastic, may be squeezed to draw the liquid out of the IV bag or bottle and into the drip chamber. The drip chamber is allowed to fill about ⅓ to ½ full when the clamp is opened to allow liquid to flow through the tube to an end of the IV set.  
         [0008]     This initial process, however, typically traps air in tubing which must be removed. For example, the flow of the liquid through the tubing of the IV set may be turbulent and can entrap air within the tube as the boundary layer between the liquid and the tubing is sheared. The flow rate out of the drip chamber may be higher than the flow rate of liquid entering the drip chamber. This can cause a bubble ladder to form as air is sucked from the drip chamber into the tubing.  
         [0009]     Additionally, air bubbles may be generated as drops of liquid strike the surface of the pool of liquid within the drip chamber. These air bubbles can be pulled into the tubing of the IV set from the drip chamber. This problem may be aggravated in pediatric applications where the drip orifice may be smaller which may result in increased turbulence.  
         [0010]     To remove air bubbles from the IV set, liquid from the IV bag or bottle is allowed to flow through the tubing while an attendant taps the tubing to encourage the air bubbles out the end of the IV set. As the liquid is allowed to flow out of the IV set to clear air bubbles from the tubing, the liquid is generally allowed to flow into a waste basket or other receptacle. During this procedure the end of the tubing may contact the waste basket or be touched by the attendant and thus, become contaminated. An additional shortcoming of this debubbling process is that it requires attention and time that could have been used to perform other tasks that may be valuable to the patient.  
         [0011]     Another debubbling method is to directly remove air bubbles from the IV set. More specifically, if the IV set includes a Y-connector, air bubbles may be removed at the Y-connector by a syringe.  
         [0012]     In some cases, a small pore filter may be used in the drip chamber to prevent air from entering the IV tubing from the drip chamber. However, the bubbles formed from the dripping action may become trapped on the filter, thus, reducing the flow of liquid through the filter to the IV tubing. However, the filter is normally positioned so that air may be trapped between the bottom of the filter and the bottom of the drip chamber.  
         [0013]     Accordingly, a need exists for an IV set that is self-priming and bubble free, and which does not require constant attention and supervision. Additionally, a need exists for an IV set that prevents bubbles from entering the tubing during use, while providing flow rates that satisfy the needs of the patient.  
       BRIEF SUMMARY OF THE INVENTION  
       [0014]     The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not been fully solved by currently available IV sets. Thus, the present invention provides an IV set for use in intravenous administration of liquids that prevents air from being passed to a patient during the intravenous administration of liquids.  
         [0015]     In accordance with the invention as embodied and broadly described herein in the preferred embodiment, an IV set is provided. According to one embodiment, the IV set may include a drip chamber having a chamber inlet and a chamber outlet and a bubble isolation membrane or other device disposed within the drip chamber that prevents air bubbles from exiting the chamber outlet. Typically, IV sets are gravity fed so that the chamber inlet is disposed in a top surface and the chamber outlet is disposed in a bottom surface of the drip chamber.  
         [0016]     The side wall of the drip chamber may include an opening located at a height above the bottom wall, and a vent plug is provided for covering the opening. The vent plug allows air contained in the drip chamber which becomes displaced upon filling of the drip chamber to escape from the drip chamber through the vent plug.  
         [0017]     Additionally, the TV set may include a means for venting air out of the patient conduit tube, such a flow control plug that has an air vent coupled to the outlet end of the patient conduit. The flow control plug may include a hydrophobic material, which allows air to exit the IV set while preventing liquid from exiting. The air vent may also include several small holes which allow air to pass while limiting the passage of liquid through the end plug. The end plug and the air vent acts as a flow restrictor to the exiting air, so that when a liquid is moving through the tube, the velocity of the liquid flow is controlled such that the flow is generally laminar. The laminar flow of the liquid through the tube prevents air from becoming entrapped within the tube during priming and helps to completely eliminate the air from the tube during priming.  
         [0018]     The bubble isolation device or membrane includes means for preventing bubbles from exiting the chamber outlet and may include an active portion that comprises a hydrophilic filter or an absorbent structure, such as a sponge. The bubble isolation device may also include an absorbent structure that includes a woven material and/or a mat of material. The mat may be sintered or adhered together by an adhesive. Additionally, the bubble isolation device may include a concave surface that is disposed within the drip chamber so that the liquid entering the drip chamber through the chamber inlet is directed toward the concave surface.  
         [0019]     Where the active portion of the bubble isolation device or membrane includes a hydrophilic filter or an absorbent structure, the bubble isolation device may be shaped to match the profile and abuts the bottom surface of the drip chamber so that the active portion completely covers the chamber outlet. By disposing the bubble isolation device against the bottom surface of the drip chamber, air is prevented from being trapped between the bubble isolation device and the bottom surface of the drip chamber.  
         [0020]     Where the bubble isolation device includes a concave surface, the bubble isolation device may be disposed to partition the chamber into a bubble isolation chamber and a calm fluid chamber. The bubble isolation chamber is above the concave surface and the calm fluid chamber is positioned below the concave surface but above the bottom surface of the drip chamber. The concave surface directs bubbles toward the surface of the liquid to be expelled as new bubbles are formed by the droplets of liquid striking the surface of the liquid.  
         [0021]     The IV set may also include a particulate filter to prevent solid material from exiting the tube. Additionally, the IV set may include a zero dead space access port disposed between the inlet end and the outlet end of the tube. A zero dead space access port is designed to substantially prevent the entrapment of air within the access port as liquid flows through the access port.  
         [0022]     The system may include a further membrane within or above the drip chamber that provides an anti-run dry feature. In the vent fluid ceases to flow within the drip chamber the membrane maintains a safe level of residual fluid within the drip chamber.  
         [0023]     A method for priming the IV set described above may include the steps of coupling the chamber inlet to a source of the liquid, wetting the bubble isolation device with liquid, and using the bubble isolation device to prevent air bubbles from reaching the chamber outlet. Additionally, the method may include the steps of opening the clamp to permit liquid to flow through the tube, using the end plug to restrict the venting of air from the tube as liquid flows through the tube so that the fluid flow through the tube is laminar, and using the end plug to prevent liquid from exiting the outlet end of the tube.  
         [0024]     The method may include the steps of providing a self priming intravenous delivery system. The intravenous delivery system comprises a coupling assembly for attaching the delivery system to a source of liquid and including a coupling membrane for controlling the flow of liquid and air through the coupling assembly. The system also includes a drip chamber for receiving liquid through the coupling and having a membrane disposed therein for preventing air from leaving the drip chamber. As discussed above, the drip chamber may include a self leveling port disposed within a wall of the drip chamber being permeable to air until liquid contact, but impermeable to liquid. The system also includes a patient conduit in fluid communication with the drip chamber and comprising a flow control plug disposed at the distal end of the conduit, wherein the flow control plug is permeable to air but impermeable to liquid. A source of fluid is attached to the coupling assembly such that fluid flows into and through the delivery system but such that air is prevented from exiting the system once the system is primed. The priming of the device takes place without user intervention. The method may also include providing an adjustable clamp on the patient conduit and further comprising the step of closing the clamp.  
         [0025]     As the configuration of the IV set varies, the method may also include additional steps. For example, where the bubble isolation device is an absorbent structure, the method may further include absorbing the liquid in the absorbent structure so that liquid does not pass the chamber outlet until the absorbent structure is saturated. Where the IV set includes a particulate filter, the method may include using the particulate filter to prevent material from the bubble isolation device from exiting the tube. Alternatively, where the tube includes a zero dead space access port, the method may include expelling all air from the zero dead space access port with the front of the liquid flowing through the tube.  
         [0026]     Where the configuration of the TV set includes an end plug, the method may include the step of using the end plug to restrict the venting of air from the tube as liquid flows through the tube so that the volume of fluid flowing through the chamber inlet is greater than or about equal to the liquid flow through the chamber outlet until the self leveling port is closed. Alternatively, where the bubble isolation device includes a concave surface, the method may further include the steps of using the bubble isolation device to partition the chamber into a bubble isolation chamber and a calm fluid chamber and using the concave surface to retain the air bubbles in the bubble isolation chamber.  
         [0027]     These and other features and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0028]     In order that the manner in which the above-recited and other features and advantages of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scopes the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
         [0029]      FIG. 1  is a perspective view of an IV set coupled to an IV bag.  
         [0030]      FIG. 2  is cross sectional view of the IV set of  FIG. 1 .  
         [0031]      FIG. 3  is a cross sectional view of an alternative embodiment of an IV set. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]     The presently preferred embodiments of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the self-priming intravenous delivery system of the present invention, as represented in  FIGS. 1 through 3 , is not intended to limit the scope of the invention, as claimed, but is merely representative of presently preferred embodiments of the invention.  
         [0033]     For this application, the phrases “connected to,” “coupled to,” and “in communication with” refer to any form of interaction between two or more entities, including mechanical, electrical, magnetic, electromagnetic, and thermal interaction. The phrase “attached to” refers to a form of mechanical coupling that restricts relative translation or rotation between the attached objects.  
         [0034]     The phrase “attached directly to” refers to a form of attachment by which the attached items are either in direct contact, or are only separated by a single fastener, adhesive, or other attachment mechanism. The term “abutting” refers to items that are in direct physical contact with each other, although the items may not be attached together. The terms “integrally formed” refer to a body that is manufactured integrally, i.e., as a single piece, without requiring the assembly of multiple pieces. Multiple parts may be integrally formed with each other if they are formed from a single work piece.  
         [0035]     Referring to  FIG. 1 , a perspective view illustrates an intravenous (IV) delivery system  10  according to the invention. As shown, the IV system  10  may be connected to a source of liquid  12 , which in this configuration is an IV bag  14 . Alternatively, the source of liquid  12  may be an IV bottle (not shown) or other container known in the art.  
         [0036]     The IV system  10  may be connected to the IV bag  12  by a coupling  20  for connecting the IV system  10  to the IV bag  14 . As shown, the coupling  20  may be a spike  22  for spiking the IV bag  14  and/or a threaded coupling (not shown).  
         [0037]     The IV system  10  may include a drip chamber  24  for determining the flow rate from the source of liquid  12 . The drip chamber  24  may include a top end  26 , a bottom end  28 , and a sidewall  30  extending between the top end  26  and the bottom end  28 . The top end  26  may include an inlet orifice  32  that may be shaped and sized to encourage liquid entering the drip chamber  24  to form droplets, facilitating the determination of the liquid&#39;s flow rate. The bottom end  28  may also include an outlet orifice  34  that permits liquid to exit the drip chamber  24 .  
         [0038]     The drip chamber  24  may also include an access orifice  36 . The access orifice  36  may be positioned in the top end  26  or in the sidewall  30 . In some configurations, the access orifice  36  may be positioned at or near an operable liquid height  38  of the drip chamber  24 . The operable liquid height  38  of the drip chamber  24  is deep enough so that air will not be sucked from the surface of the liquid into the outlet orifice  34 , yet shallow enough that each droplet that falls from the inlet orifice  32  may be discerned in order to determine the flow rate of liquid into the drip chamber  24 . For example, the operable liquid height  38  may range from about ⅓ to about ⅔ full. However, the preferable operable liquid height  38  of drip chamber  24  may range from about ⅓ to about ½ full.  
         [0039]     A self leveling port  40  may be connected to the access orifice  36 . The access port  40  may be used to removably connect the access orifice  36  to various devices  42 , such as a cap  44 , another IV set, a syringe, and other devices known in the art. As shown, the access port  40  may be a Luer fitting, known in the art.  
         [0040]     A valve  46  may also be connected to the drip chamber  24  to selectively control access to the drip chamber  24  through the access orifice  36 . The valve  46  may be a stop cock, a slide valve, a butterfly valve, or any other type of valve known in the art. The valve  46  may be opened to allow gravity to pull liquid from the source of liquid  12  into the drip chamber  24  without deforming the sidewall  30  of the drip chamber  24  to induce a vacuum. The valve  46  may remain open until the operable liquid height  38  is reached. When the valve  46  is closed, fluid may only enter and exit through the inlet orifice  32  and outlet orifice  34 . Thus, when the valve  46  and the outlet orifice  34  are closed, the pressure within the drip chamber  24  may rise until the liquid is unable to enter the drip chamber  24  from the inlet orifice  32 .  
         [0041]     In configurations of the IV system  10  where the self leveling port  40  and the valve  46  are connected to the access orifice  36 , the valve  46  may be disposed to prevent fluid from the self leveling port  40  from reaching the access orifice  36 . For example, the valve  46  may be used to control the flow from another IV system connected to the self leveling port  40  into the drip chamber  24 .  
         [0042]     Additionally, a filter  48  may be connected to the access orifice  36 , permitting air to flow through the filter  48  while restricting the flow of liquid. Where the access orifice  36  is disposed at an operable liquid height  38 , the filter  48  may be used as a fail safe to prevent the height of liquid within the drip chamber  24  from exceeding the operable liquid height  38  of the drip chamber  24 . More specifically, once the filter  48  is covered by the liquid within the drip chamber  24 , the liquid and air in the drip chamber  24  is prevented from exiting the access orifice  36 . Thus, the pressure may rise within the drip chamber  24  and prevent liquid from entering the drip chamber  24  from the source of liquid  12 . In this configuration the filter  48  results in the self leveling port  40  being permeable to air, but impermeable to liquid, and becomes impermeable to air upon contact with liquid.  
         [0043]     The IV system  10  may also include a membrane  50  disposed in the drip chamber  24 . The membrane  50  is configured such that air is prevented from leaving the drip chamber  24 . Thus, the membrane  50  acts as a bubble trap to trap any air bubbles that may otherwise flow out of the drip chamber  24  into the patient conduit  52 .  
         [0044]     As illustrated in  FIG. 1 , the drip chamber  20  is connected to a patient conduit  52 . The conduit  24  is a tube used to convey fluid  14  from the drip chamber  20  and the IV bag  12  to a patient.  
         [0045]     A clamp  54 , a zero dead space access port  56 , and a flow control plug  58  may be attached to the tube  24 . The clamp  54  permits the flow of liquid  14  exiting the drip chamber  20  to be controlled and stopped. The zero dead space access port  56  permits another IV set (not shown) to be piggybacked onto the IV set  10  or to have medication directly added to the fluid  14  by a syringe (not shown). The zero dead space access port  56  is also designed not to trap air as the liquid  14  flows through it. The flow control plug  58  helps to protect an end  60  of the IV system from contamination and also helps to prevent air bubbles from moving through the tube  24  with the liquid  14 . In particular, the flow control plug  58  controls fluid flow in the patient conduit  52  during priming to reduce air bubble formation.  
         [0046]     Before the IV system  10  is attached to a source of liquid  14 , the clamp  54  is typically opened, unlike conventional systems where the clamp is closed to prevent the flow of fluid through the patient conduit  52 . As shown, the clamp  54  is a roller clamp  62 . Other types of clamps may be used. The clamp may be pre-programmed to allowed fluid flow at a specific rate. Once the IV system  10  is attached to a source of liquid  14 , it is unnecessary to produce a vacuum by squeezing the drip chamber  24  as is conventional.  
         [0047]     Referring to  FIG. 2 , a cross sectional view illustrates the IV system and specifically the drip chamber  24  of  FIG. 1 . As shown, the membrane  50  conforms to the shape of the bottom end  28  of the drip chamber  20  and completely covers the chamber outlet  64 . By positioning the membrane  50  to completely cover the chamber outlet  64 , air is prevented from being trapped between the membrane  50  and the bottom end  28  as the fluid  14  moves through the membrane  50 .  
         [0048]     While in use, air bubbles  80  are generated as the droplets  82  strike the surface  84  of the pool  86 . The membrane  50  prevents the air bubbles  80  from reaching the chamber outlet  64  so that the air bubbles  80  are able to return to the surface  84  of the pool  86  and be discharged or vented through the self leveling port  40 . Also, the membrane may be made of molded open-cell foam that has a general pore size of about 10 to 20 microns with the preferred pore size being about 12 to 15 microns.  
         [0049]     Also shown, the connection  90  between the patient conduit  52  and the drip chamber  24  is a zero dead space connection. In other words, the inlet end  92  is shaped to be attached flush to the chamber bottom end  28  so that air may not be entrapped at the connection  90  as the fluid  14  passes the connection  90  and purges the air from the patient conduit  52 .  
         [0050]      FIG. 3  depicts an alternative embodiment of a self priming IV delivery system  100  used for administering an IV-solution to a patient. As illustrated above, a source of liquid  112  is provided. The liquid is located in a container  114  such as a vented rigid container or bottle, or a collapsible plastic bag, as is discussed above . . . . The IV system  100  is a hermetically sealed system and includes a solution coupling spike assembly  116  having a lancing or piercing member  118  for piercing a seal on the container  114 . As set forth above, other primary components of the IV system  10  include a drip chamber  120 , and a patient conduit  122  having a termination end  124  and supporting a flow controller such as a roller clamp  126  for controlling the flow of liquid in the patient conduit  122 .  
         [0051]     The venting conduit  126  provides a sealable opening at an outer end for communicating with the surrounding atmosphere, i.e. with the environment in which the IV system  100  is disposed. When the spike assembly  116  is connected to a rigid container  112 , such as a glass bottle, venting of the container is provided through the conduit  30  to allow the liquid to flow. If, on the other hand, the container  112  is a collapsible bag, venting is not required and the conduit  126  can remain sealed. As the liquid is drawn out by the piercing member  118  of the spike assembly  116 , the liquid flows down into a funnel-shaped portion  128  having an outlet end  130  which supports a drip orifice  132  or which otherwise directs the liquid to the drip orifice for providing the liquid, in the form of a succession of individual drops, to the drip chamber  120 .  
         [0052]     The spike assembly  116  also includes a check valve  136  disposed at an outlet end of the venting conduit  126  and an air filter  138  disposed between the check valve  136  and the surrounding atmosphere, as shown. When the venting conduit is opened, as in the case of the piercing member  118  being coupled to a rigid container  114 , the check valve allows filtered air, through air filter  138 , to enter the venting conduit to cause liquid to flow out of the container, but prevents air, and consequently, liquid, from exiting the container  112  through the venting conduit  126 . A membrane  140 , which may be configured as a fine mesh screen, is also preferably included in the spike assembly  116 . The membrane may be formed of any suitable material—such as polyamide nylon 6,6, polyamide nylon 11, or polyester-polyethylene teraphthalate with a hydrophilic coating applied by a plasma coating process—and causes a sealing off of the funnel portion  128  of the spike assembly from the fluid conduit  142  when the contents of the container  114  have been drained into the spike assembly  116 . The sealing off is caused by the surface tension of the medicament forming a barrier on the membrane  140  which will prevent air present in the container  112  from being passed through to the drip chamber  120  and to the patient conduit  122 . Thus, upon emptying of the container  114 , the air present in the container will be confined to an area  144  above the membrane  140 .  
         [0053]     When a subsequent dose of medicament is required, the spike  118  of the spike assembly  116  is removed from the empty container  112  and attached to a full container. In order to start the flow of liquid from the subsequent container, the air confined in area  144  must be removed, and a venting membrane  146  is included in the spike assembly for this purpose. As liquid again flows from the second container  112 , air will be forced out through the membrane  146 . Membrane  146  may be comprised of a porous hydrophobic material such as polyethylene (PE), polypropylene (PP), or polytetrafluoroethylene (PTFE), so that air is allowed to pass from area  144  to the surrounding atmosphere while preventing liquid in the funnel portion  128  from spilling through the membrane, such as in the event of an overflow condition. Once the air is removed, the roller clamp  150  is opened to allow the fluid to flow into the patient line  122 . A check valve  148  prevents air from the surrounding atmosphere from entering area  144  through membrane  144  when fluid flows from the container  112 .  
         [0054]     The drip chamber  120  includes a top wall providing an inlet opening, a bottom wall  154  providing an outlet opening  156 , and at least one side wall  158  comprised of a transparent or translucent material so that medicament in the drip chamber can be readily viewed. A drip orifice or opening  132  may be formed on, attached to, or may depend from the top wall  150  or, alternatively, may be formed on the outlet end  130  of the spike assembly  116 . As explained above, the drip orifice  132  establishes the size of the liquid drops  134  as the liquid enters the drip chamber  120 . By adjusting the rate of flow of the drops  134  into the drip chamber  120 , and knowing the size of the individual drops which is dictated by the drip orifice size, a medicament dosage rate can be established. The drip chamber  120  also includes an opening or hole  160  formed in the side wall  158  and vertically displaced from the drip chamber bottom  154  by a predetermined amount “x”. The opening  160  may be formed as part of a primary molding process in which the drip chamber  120  is formed, or as a secondary process wherein the opening  160  is punched-out or otherwise removed from the side wall  158 . As explained more fully below, the opening  60  is dimensioned to accommodate a sealing off by of a vent plug  162  to provide a self-priming function to the drip chamber  120 .  
         [0055]     The term “vent plug” as used herein means an obstruction for sealing off the opening  160 . This can be accomplished, by way of non-limiting example, by a member dimensioned for seating within the opening  160  or by a cover or shield, such as a band of material. The vent plug may include various other types of plugs, including mechanically or chemically actuated plugs. The plug may be a bimetallic strip which is water activated. The vent plug may be activated by temperature, pressure, or chemical action. The vent plug may also be mechanically triggered.  
         [0056]     The fluid drops  134  form a reservoir  164  at the bottom of the drip chamber  120 . The liquid is then provided to the patient conduit  122  for conveying the liquid to the termination end  124 , at which an end cap  170  that may be detachably or permanently connected, allows coupling of the patient line to an IV needle (not shown). The end cap  170  includes a side wall  171 , a front wall  173  in which a vent  172  is formed, and a termination end vent plug  174 . Also disposed on the patient conduit  122  is the roller clamp  150  having an adjustable control such as a knurled wheel  176  for regulating the flow of liquid in the patient conduit  122 .  
         [0057]     As fully discussed above, a problem with existing IV systems having drip chambers lies in the setup and “priming” of the drip chamber to establish a desired or prescribed medicament flow rate at which the medicament will enter the patient. As explained above, this typically requires a heath care professional, such as a nurse, to allow the medicament in the drip chamber to reach a certain level, typically ⅓ of the drip chamber volume. In order to accomplish this, the patient conduit  122  needs to be obstructed or otherwise partially closed off so that the liquid will fill the drip chamber  120  at a faster rate than the liquid enters the patient conduit  122  to form the reservoir  164 . Thus, the health care professional will be required to tighten the roller clamp  150  for this purpose. Moreover, to set the reservoir level at approximately ⅓ of the drip chamber volume, an equal volume of air in the drip chamber must be removed. In pre-existing IV systems, this was accomplished by squeezing the flexible drip chamber side wall  158 . In the event the squeezing of the drip chamber side wall  158  caused an excessive amount of air to be removed, this resulted in an excessive amount of liquid collected in the reservoir  164  which then needed to be removed in a tedious manner as explained above. Also, if the liquid entered the reservoir and/or patient line too rapidly, air bubbles will be formed on the inner surface of the patient conduit and then have to be removed, typically by tapping the chamber  120  and/or patient conduit  122 .  
         [0058]     In accordance with the present invention, the manual priming activity previously performed by health care professionals can be eliminated by the IV system  100 . When the spike assembly  116  is first connected to a liquid container  112 , liquid will begin to flow through the liquid conduit  142  into the funnel region  128 , whereupon the drip orifice  132  will cause liquid drops  134  to be formed and fall, under the force of gravity, into the drip chamber  120 . To facilitate formation of the reservoir  164  and, specifically, to prevent the liquid from draining into the patient conduit  122  before the reservoir  164  can be formed to a desired depth relative to the drip chamber bottom  154 , liquid flow through the patient conduit  122  must be obstructed so that the medicament level will rise in the drip chamber at a rate which exceeds the flow of the medicament into the patient line. This can be accomplished by adjustment of the roller clamp  150 , such as by manipulating adjustment wheel  176  or, as is contemplated by the preferred embodiment, through the vent  172  formed in the front wall  173  of the end cap  170 . Thus, if the roller clamp  150  is in its fully opened state, the narrow opening of the vent  172  will restrict liquid flow in the patient conduit  122  to a rate which is slower than the rate that the fluid enters the drip chamber  120  so that the reservoir  164  can form in the drip chamber and so that fluid will enter the patient line at a slow rate to prevent the formation of air bubbles therein.  
         [0059]     With flow in the patient conduit  122  restricted by the roller clamp  150  and/or by the end cap  170 , liquid drops  134  continue to enter the drip chamber  120  so that the reservoir  164  will rise to a height of “x”. This height corresponds to the opening  160  at which the vent plug  162  is disposed. In one embodiment, the vent plug  162  is comprised of an absorptive material which allows displaced air from the drip chamber  120 —which is displaced by the increased level of the reservoir  164 —to pass from the drip chamber to the surrounding atmosphere but which, upon contacting liquid, expands or swells to seal off the opening  160 . When this occurs, liquid in the reservoir  164  is prevented from escaping through the vent plug  162  and air from the surrounding atmosphere is prevented from reentering the drip chamber  120  through the vent plug  162 .  
         [0060]     In this manner, the IV system  100  functions as a self-priming device which automatically allows the reservoir to fill to a desired level (e.g., ⅓ of the drip chamber volume) once the spike assembly  116  is attached to the liquid container  114  so that a health care professional no longer needs to compress the drip chamber side wall  158  to cause liquid to flow therein. Because the drip chamber no longer needs to be compressed for priming, the problem of over-filling the drip chamber is avoided. Consequently, the material used to form the drip chamber  120  is no longer limited to a flexible material but can now include rigid materials.  
         [0061]     Suitable absorptive materials for the vent plug  162  include, by way of non-limiting example, porous PE, PP, or PTFE, embedded, doped or coated with carboxymethylcellulose (CMC), polyacrylate, or other known or hereafter discovered super-absorbent polymers.  
         [0062]     To allow air present in the patient conduit  122  to escape through the termination end  124  so that, upon connection of the termination end  124  to a patient, such air will not enter the patient, the termination end vent plug  174  is provided. The termination end vent plug  174  is comprised of porous PE, PP, or PTFE, embedded, doped or coated with a super-absorbent polymer and creates a barrier when liquid impinges upon it. Alternatively, the termination end vent plug  174  can be formed of a hydrophobic material. Once the patient conduit  122  is completely filled with liquid, all air is removed therefrom and the termination end vent plug  174  forms a barrier to prevent spillage of the liquid through the vent  172 . In this state, the IV system  100  is ready for attachment to a patient IV connection. This can be accomplished by detaching the end cap from the patient line and then coupling the line to a patient. The termination end vent plug  174  allows air from the patient conduit  122  to pass from the patient line to the surrounding atmosphere through vent  172  in the end cap  170 . However, once the termination end vent plug becomes wet through contact with the liquid in the patient conduit  126 , air is prohibited from reentering the patient line through the vent  172 .  
         [0063]     When connecting the already-primed IV system  100  to a subsequent medicament container, the health care professional simply closes the patient conduit  122  via the roller clamp  150 , disconnects the spike  118  from the empty container, and attaches it to a full container. Any amount of liquid that may exist in the spike  118  during disconnection and reconnection to a medicament container is de minimis and will have little effect on the level of the reservoir  64 . Once connected and the patient line reopened by opening the roller clamp, air in region  144  will be removed through membrane  146  and liquid will begin to flow into the drip chamber and into the patient conduit  122 .  
         [0064]     Another benefit of the inventive self-priming IV system  100  is that the occurrence of a high liquid flow rate into the drip chamber is reduced or altogether avoided because the primary cause of such a condition—the manual compressing of the drip chamber side wall  158 —is no longer performed. Nevertheless, to prevent the vent plug  162  from prematurely contacting the liquid, such as when the drops  134  enter the drip chamber  120  and cause a splatter or splashing effect against the surface of the reservoir, a splash guard  178  formed of, for example, a liquid impervious plastic shield, can be readily affixed about the vent plug  162  to the internal surface of the side wall  158  of the drip chamber. As shown, the splash guard  176  is connected to the drip chamber side wall  158  by, for example, adhesive at a location above the vent plug  162 , and extends to a point below the vent plug  162  and offset from the side wall  158  so that an opening  177  is formed to allow the rising reservoir  164  to contact the vent plug  162  in an intended manner.  
         [0065]     It should be appreciated that the inventive drip chamber  120  and the vented end cap  170  can be used together in an IV system, or can be used separately, with the benefits attributed to each such feature being realized by that feature&#39;s use. For example, the drip chamber  16  can be used in conjunction with the roller clamp  150  by using the roller clamp to partially close off and restrict liquid flow in the patient conduit  126 . This allows the reservoir  164  to fill to a desired level to moisten the vent plug  162  and also allows a slow rate of liquid to fill the patient conduit  126  and expel air therefrom through the termination end  124  without causing air bubbles to form on the inner surface of patient conduit  122 . Such a system, however, still requires caregiver attention because the roller clamp  150  will need to be manipulated to adjust a desired flow rate for priming the drip chamber  120 . Likewise, end cap  170  can be used at the termination end of a patient conduit  122  attached to any known IV delivery system, such as a system containing a drip chamber  120  or a system containing an infusion pump (not shown). The end cap  170 , as explained above, will reduce the rate of liquid flow in the patient conduit  122  so that air bubbles will not be formed on the inner surface of the fluid conduit. Moreover, termination end vent plug  174  will prevent seepage of the liquid from the termination end  124  once the patient line becomes filled in the intended manner. If the end cap  170  is of a removable configuration, such as via a Luer-type connection as is known in the art, then once the patient conduit  122  is filled, roller clamp  150  will be closed and end cap  170  can then be removed without causing seepage of the liquid contained in the patient conduit  122 , whereupon the conduit can then be attached to the intravenous needle connected to a patient. Thereafter, roller clamp  150  can be re-opened to allow intended operation of the IV system.  
         [0066]     An additional feature illustrated in  FIG. 3  is an extension conduit  180  is disposed between the spike assembly and drip chamber to transport the liquid from the spike assembly  116 , and in particular, from the outlet  130  of the funnel portion  128 , to the drip chamber  120 . The extension conduit is comprised of a flexible tube material such as plastic, having a length “L”, and which is preferably transparent or translucent. The extension conduit  180  has an inlet end  182  connected to the spike assembly outlet, and an outlet end  184  connected to, or otherwise disposed in, the drip chamber top wall  150 . In this embodiment the drip orifice  132  may be formed in the outlet end  184  of the conduit or, may be formed in the drip chamber top wall  150 . The length “L” of the conduit is sufficient to separate the relative distance between the spike assembly  116  and the drip chamber  120  so that the drip chamber is disposed at a height which is more readily viewable by the health care professional. This feature is desirable because the liquid bag or bottle may be positioned higher than the eye level of the health care professional making observation of the drip chamber and the counting of drops for flow rate adjustments will be difficult. The extension conduit  180  can be used in connection with any known IV system for separating a drip chamber from a spike assembly.  
         [0067]     The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.