Patent Description:
One common method of administering fluids into a patient's blood flow is through an intravenous delivery system. In many common implementations, an intravenous delivery system may include a liquid source such as a liquid bag, a drip chamber used to determine the flow rate of fluid from the liquid bag, tubing for providing a connection between the liquid bag and the patient, and an intravenous access unit, such as a catheter that may be positioned intravenously in a patient. An intravenous delivery system may also include a Y-connector that allows for the piggybacking of intravenous delivery systems and for the administration of medicine from a syringe into the tubing of the intravenous delivery system.

It is a generally good practice to remove air from intravenous delivery systems that access a patient'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's blood stream while receiving the intravenous administration of fluids, the air bubbles can form an air embolism and cause serious injury to a patient.

Normally, 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 throughout the body.

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's blood stream.

In spite of the importance of removing air bubbles while priming an intravenous delivery system for use in the intravenous administration of fluids, the complete removal of air bubbles can be a time consuming process. The process may also lead to contamination of the intravenous delivery system by inadvertently touching a sterile end of the intravenous delivery system. Typically, when an intravenous delivery system is primed, a clamp is closed to prevent fluid from moving from a drip chamber through the tubing. The intravenous delivery system may then be 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 fluid out of the IV bag or bottle and into the drip chamber. The drip chamber may be allowed to fill about ⅓ to ½ full when the clamp is opened to allow fluid to flow through the tube to an end of the intravenous delivery system.

This initial process, however, typically traps air in tubing which must be removed. For example, the flow of the fluid through the tubing of the intravenous delivery system may be turbulent and can entrap air within the tube as the boundary layer between the fluid and the tubing is sheared. The flow rate out of the drip chamber may be higher than the flow rate of fluid entering the drip chamber. This can cause a bubble ladder to form as air is sucked from the drip chamber into the tubing.

Additionally, air bubbles may be generated as drops of fluid strike the surface of the pool of fluid 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.

To remove air bubbles from the intravenous delivery system, fluid from the IV bag or bottle may be allowed to flow through the tubing while an attendant taps the tubing to encourage the air bubbles out the end of the intravenous delivery system. As the fluid is allowed to flow out of the intravenous delivery system to clear air bubbles from the tubing, the fluid may be 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.

Another debubbling method is to directly remove air bubbles from the intravenous delivery system. More specifically, if the intravenous delivery system includes a Y-connector, air bubbles may be removed at the Y-connector by a syringe. This method still requires additional time and attention, and may also carry risk of contamination of the liquid to be delivered.

To address the difficulties of removing bubbles from an intravenous delivery system, various prior art intravenous delivery systems have employed a membrane for filtering air from the fluid as it flows through the intravenous delivery system. For example, oftentimes a membrane may be placed in the bottom of the drip chamber so that fluid flowing out of the drip chamber must pass through the membrane. The membrane can be configured to allow the passage of fluid while blocking the passage of air. In this way, bubbles are prevented from passing into the tubing leading to the patient. Similarly, a membrane can be included in the connector that couples the tubing to a catheter to block any air present in the tubing from passing into the patient's vasculature.

Additionally or alternatively, some known intravenous delivery systems utilize a vent cap, which may be coupled to the free end of the tubing prior to attachment of the catheter. Such vent caps are generally intended to vent air out of the intravenous delivery system. However, known vent caps generally accommodate only a very small quantity of the liquid. Air may be entrained in the liquid, and may remain trapped in the tubing when the intravenous delivery system is fully primed.

Thus, such vent caps are not always effective at venting air. In some instances, the clinician must take steps to manually release the air, which requires additional time and attention, and may also carry risk of contamination of the liquid, as detailed above.

Further, some known vent caps have valves that help retain liquid within the vent cap after detachment of the vent cap from the tubing. Such valves are often complex structures, and in many instances, such valves require the presence of corresponding hardware on the tubing to open the valve when the vent cap is attached to the tubing. Accordingly, such valves add to the complexity and cost of known intravenous delivery systems, and may also add failure points that can cause unexpected leakage in the event of improper attachment, manufacturing defects, and/or the like. <CIT> discloses a cap for use in printing a medical connector that has a distal end at which is disposed a distal connection tip with an aperture through which fluid may flow, and the connector having an internal valve.

The invention comprises an intravenous delivery system as defined in claim <NUM>. Embodiments of the present invention are generally directed to an intravenous delivery system with a vent cap that provides enhanced air venting. The intravenous delivery system may have a liquid source containing a liquid to be delivered to a patient, tubing, and the vent cap. The tubing may have a first end connectable to the liquid source, and a second end connectable to the vent cap.

The vent cap may have a proximal end connectable to the distal end of the tubing to receive the liquid, and a distal end having a vent that is substantially impermeable to the liquid and substantially permeable to air. Further, the vent cap may have a chamber wall that defines a chamber that receives the liquid from the proximal end. The chamber may have a volume selected to enable the chamber to receive a quantity of liquid from the tubing in which the air, if entrained in the liquid, is likely to reside after the tubing has been primed sufficiently to advance the liquid through the second end of the tubing.

The desired volume of the chamber may be determined by the equation V = πr<NUM>l, where V is the volume, r is a radius of an interior of the tubing, and l is a length of tubing within which the air, if present in the liquid, is likely to reside after the tubing has been primed. In some embodiments, the length referenced in the equation may range from <NUM> millimeters to greater than <NUM> millimeters (<NUM> inches to greater than <NUM> inches). The volume may range from <NUM> milliliters to greater than <NUM> milliliters.

The chamber wall may have a generally tubular shape with an interior diameter that ranges from <NUM> millimeters to <NUM> millimeters, a length that ranges from <NUM> millimeters to <NUM> millimeters. The geometry of the chamber does not need to be tubular and can be cubic, frustoconical, etc. The proximal end of the vent cap may have a vent cap luer lock that mates with a tubing luer lock of the second end of the tubing. The chamber wall may be shaped to have a proximal flare that provides the chamber wall with an interior diameter greater than the largest interior diameter of the vent cap luer lock.

The vent cap may be detachably connectable to the second end of the tubing, for example, through the use of the vent cap luer lock and the tubing luer lock referenced above. The vent cap may be configured to retain substantially all of the liquid it has received after detachment of the vent cap from the tubing, without requiring the presence of a valve within the vent cap. More specifically, the chamber wall may be shaped to define an orifice adjacent to the chamber. The orifice may be sized to substantially prevent liquid outflow from the chamber. Additionally or alternatively, the orifice may be covered with a hydrophilic membrane that prevents outflow of the liquid. The vent may have a hydrophobic membrane that facilitates release of the air from the vent cap, while retaining the liquid.

The intravenous delivery system may also have other components. Such components may include a drip unit that receives the liquid from the liquid source and delivers it to the tubing, and/or an intravenous access unit that is connectable to the second end of the tubing to deliver the liquid to the patient.

According to one method, an intravenous delivery system may be prepared for use by, first, connecting the various components of the intravenous delivery system together, as indicated previously. This may entail connecting the first end of the tubing to the liquid source and/or the drip chamber, and/or connecting the second end of the tubing to the vent cap. The second end of the tubing may be connected to the vent cap via a vent cap luer lock and a tubing luer lock, as indicated previously.

The intravenous delivery system may then be primed by gravity feeding liquid from the liquid source to the vent cap through the tubing. In response to priming the intravenous delivery system, the vent cap may receive a quantity of the liquid from the tubing in which air, if entrained in the liquid, is likely to reside after the tubing has been primed sufficiently to advance the liquid through the second end of the tubing. In response to receipt of the quantity of liquid within the vent cap, the air may be vented out of the vent cap.

After the air has been vented out of the vent cap, the vent cap may be detached from the second end of the tubing. In some embodiments, this may entail retaining substantially all of the quantity of liquid within the vent cap, without requiring the presence of a valve within the vent cap. The intravenous access unit may then be connected to the second end of the tubing. The intravenous access unit may then be ready for use to access the patient's vascular system to deliver the liquid to the patient.

These and other features and advantages of the present invention may be incorporated into certain embodiments of the invention and 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. The present invention does not require that all the advantageous features and all the advantages described herein be incorporated into every embodiment of the invention.

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 that are illustrated in the appended drawings. These drawings depict only typical embodiments of the invention and are not therefore to be considered to limit the scope of the invention. Only <FIG> shows the embodiment of the invention as claimed.

The presently preferred embodiments of the present invention can be understood by reference to the drawings, wherein like reference numbers indicate identical or functionally similar elements. 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, as represented in the figures, is not intended to limit the scope of the invention as claimed, but is merely representative of preferred embodiments of the invention.

Moreover, the Figures may show simplified or partial views, and the dimensions of elements in the Figures may be exaggerated or otherwise not in proportion for clarity. In addition, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to a terminal includes reference to one or more terminals. In addition, where reference is made to a list of elements (e.g., elements a, b, c), such reference is intended to include any one of the listed elements by itself, any combination of less than all of the listed elements, and/or a combination of all of the listed elements.

The term "substantially" means that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

As used herein, the term "proximal", "top", "up" or "upwardly" refers to a location on the device that is closest to the clinician using the device and farthest from the patient in connection with whom the device is used when the device is used in its normal operation. Conversely, the term "distal", "bottom", "down" or "downwardly" refers to a location on the device that is farthest from the clinician using the device and closest to the patient in connection with whom the device is used when the device is used in its normal operation.

As used herein, the term "in" or "inwardly" refers to a location with respect to the device that, during normal use, is toward the inside of the device. Conversely, as used herein, the term "out" or "outwardly" refers to a location with respect to the device that, during normal use, is toward the outside of the device.

Referring to <FIG>, a front elevation view illustrates an intravenous delivery system <NUM> according to one embodiment. As shown, the intravenous delivery system <NUM> may have a number of components, which may include a liquid source <NUM>, a drip unit <NUM>, tubing <NUM> a retention unit <NUM>, a vent cap <NUM>, and an intravenous access unit <NUM>. The manner in which these components are illustrated in <FIG> is merely exemplary; those of skill in the art will recognize that a wide variety of intravenous delivery systems exist. Thus, the various components the intravenous delivery system <NUM> may be omitted, replaced, and/or supplemented with components different from those illustrated.

The liquid source <NUM> may have a container containing a liquid <NUM> to be delivered intravenously to a patient. The liquid source <NUM> may, for example, have a bag <NUM>, which may be formed of a translucent, flexible polymer or the like. The bag <NUM> may be shaped to contain the liquid <NUM>.

The drip unit <NUM> may be designed to receive the liquid <NUM> from the bag <NUM> in a measured rate, for example, as a series of drips occurring at a predictable, consistent rate. The drip unit <NUM> may be positioned below the bag <NUM> so as to receive the liquid <NUM> via gravity feed. The drip unit <NUM> may have a receiving device <NUM> that receives the liquid <NUM> from the liquid source <NUM>, a drip feature <NUM> that determines the rate at which the liquid <NUM> is received by the drip unit <NUM>, and a drip chamber <NUM> in which the liquid <NUM> is collected.

The tubing <NUM> may be standard medical grade tubing. The tubing <NUM> may be formed of a flexible, translucent material such as a silicone rubber. The tubing <NUM> may have a first end <NUM> and a second end <NUM>. The first end <NUM> may be coupled to the drip unit <NUM>, and the second end <NUM> may be coupled to the vent cap <NUM>, such that the liquid <NUM> flows from the drip unit <NUM> to the vent cap <NUM>, through the tubing <NUM>.

The retention unit <NUM> may be used to retain various other components of the intravenous delivery system <NUM>. As shown, the retention unit <NUM> may have a main body <NUM> and an extension <NUM>. Generally, the tubing <NUM> may be connected to the main body <NUM> proximate the first end <NUM>, and to the extension <NUM> proximate the second end <NUM>. Various racks, brackets, and/or other features may be used in addition to or in place of the retention unit <NUM>.

The vent cap <NUM> may have a proximal end <NUM> and a distal end <NUM>. The proximal end <NUM> may be coupled to the second end <NUM> of the tubing <NUM>. The distal end <NUM> may be exposed to the ambient air so that air from within the vent cap <NUM> can be vented from the intravenous delivery system <NUM> through the distal end <NUM>.

The intravenous access unit <NUM> may be used to supply the liquid <NUM> to the vascular system of the patient. The intravenous access unit <NUM> may have a first end <NUM> and an access end <NUM>. The first end <NUM> may be connectable to the second end <NUM> of the tubing <NUM> in place of the vent cap <NUM>. Thus, when the intravenous delivery system <NUM> is fully primed, the intravenous access unit <NUM> may be coupled to the second end <NUM> of the tubing <NUM> in place of the vent cap <NUM>. In alternative embodiments (not shown), various connectors such as Y-adapters may be used to connect the first end <NUM> of the intravenous access unit <NUM> to the tubing <NUM> without detaching the vent cap <NUM> from the second end <NUM> of the tubing <NUM>.

The intravenous delivery system <NUM> may be primed by connecting the components (except for the intravenous access unit <NUM>) together as illustrated in <FIG>, and then allowing the liquid <NUM> to gravity feed through the drip unit <NUM> and the tubing <NUM> into the vent cap <NUM>. If desired, the drip unit <NUM> may be squeezed or otherwise pressurized to expedite flow of the liquid <NUM> through the tubing <NUM>.

As the liquid <NUM> flows through the tubing <NUM>, air may become entrained in the liquid <NUM>. This air may move from the first end <NUM> of the tubing <NUM>, toward the second end <NUM> of the tubing <NUM>, along with the column of liquid <NUM>. This entrained air may gather into bubbles proximate the second end <NUM> of the tubing <NUM>. The vent cap <NUM> may be designed to receive a volume of the liquid <NUM> sufficient to permit passage of such air bubbles into the vent cap <NUM>, so that they can be vented from the intravenous delivery system <NUM> through the distal end <NUM> of the vent cap <NUM>. The manner in which the vent cap <NUM> accomplishes this will be shown and described in connection with <FIG>.

Referring to <FIG>, a front elevation, section view illustrates a portion of the tubing <NUM> and the vent cap <NUM> of the intravenous delivery system <NUM> of <FIG>. As shown, the second end <NUM> of the tubing <NUM> may have an air-carrying portion <NUM> in which air, if present in the liquid <NUM>, tends to reside until vented from the intravenous delivery system <NUM>. The air-carrying portion <NUM> may have a volume with a generally cylindrical shape defined by and contained within the generally tubular shape of the tubing <NUM>. Thus, the air-carrying portion <NUM> may have a length <NUM> and a diameter, which may be an interior diameter <NUM> of the second end <NUM> of the tubing <NUM>. The volume of the air-carrying portion <NUM> may be determined by the equation Vt = πrt<NUM>lt, where lt is the length <NUM> of the air-carrying portion <NUM>, and rt is the radius of the air-carrying portion <NUM>, which is half of the interior diameter <NUM> of the second end <NUM> of the tubing <NUM>.

According to one example, the interior diameter <NUM> of the second end <NUM> of the tubing <NUM> may be about <NUM> millimeters. The length <NUM> may fall within the range of <NUM> millimeter to <NUM> millimeters (<NUM> inches to <NUM> inches). More specifically, the length <NUM> may fall within the range of <NUM> millimeters to <NUM> millimeters (<NUM> inches to <NUM> inches). Yet more specifically, the length <NUM> may be about <NUM> millimeters (<NUM> inches). It has been observed that, in prior art intravenous delivery systems that have problems with residual air after priming, air bubbles tend to reside within the segment of tubing adjacent to the vent cap <NUM>, within about <NUM> millimeters (<NUM> inches) of the vent cap <NUM>. Setting the length <NUM> of the air-carrying portion <NUM> equal to approximately <NUM> millimeters (<NUM> inches) reflects this observation. The volume Vt of the air-carrying portion <NUM> may fall within the range of <NUM> milliliters to <NUM> milliliters. More specifically, the volume Vt of the air-carrying portion <NUM> may fall within the range of <NUM> milliliters to <NUM> milliliters. Yet more specifically, the volume Vt of the air-carrying portion <NUM> may be about <NUM> milliliters.

The second end <NUM> of the tubing <NUM> may have a connector designed to facilitate detachable coupling of the second end <NUM> to the proximal end <NUM> of the vent cap <NUM>. Various types of connectors may be used. In some examples, luer type connectors of a type known in the art may be used. As embodied in <FIG>, the connector may take the form of a tubing luer lock <NUM>, which may be secured to the tubing material of the second end <NUM>. The tubing luer lock <NUM> may have a male tapered fitting <NUM> that extends distally, toward the vent cap <NUM>. The tubing luer lock <NUM> may further have a female threaded interface <NUM>.

Similarly, the proximal end <NUM> of the vent cap <NUM> may have a vent cap luer lock <NUM> designed to mate with the tubing luer lock <NUM> such that the vent cap <NUM> may be easily and detachably coupled to the second end <NUM> of the tubing <NUM>. The vent cap luer lock <NUM> may have a female tapered fitting <NUM> that receives the male tapered fitting <NUM> of the tubing luer lock <NUM> in a manner that generally forms a seal with the male tapered fitting <NUM>. The vent cap luer lock <NUM> may further have a male threaded interface <NUM> that mates with the female threaded interface <NUM> of the tubing luer lock <NUM> such that the vent cap luer lock <NUM> can be rotated into threaded engagement with the tubing luer lock <NUM>.

The distal end <NUM> of the vent cap <NUM> may have a vent designed to be substantially permeable to air. This means that the vent permits passage of air therethrough at a flow rate sufficient to release all of the air from the intravenous delivery system <NUM> within a few minutes. Further, the vent may be designed to be substantially impermeable to liquids. This does not require that the vent provide a seal that is completely impervious to liquid passage, but rather, that the vent restricts liquid flow sufficient that, within a few minutes, only a relatively small percentage (for example, less than <NUM>%) of the liquid within the intravenous delivery system <NUM> is able to escape.

As shown in <FIG>, the vent may take the form of a hydrophobic membrane <NUM>, which may be ultrasonically welded or otherwise attached to the remainder of the vent cap <NUM>. The hydrophobic membrane <NUM> may generally repel the liquid <NUM>, which may tend to cause the liquid <NUM> to remain displaced from the hydrophobic membrane <NUM>, as shown, if there is any air present in the vent cap <NUM>. Generally, air within the vent cap <NUM> may readily move to the hydrophobic membrane <NUM>, but if the column of liquid <NUM> stops moving with air still within the air-carrying portion <NUM> of the second end <NUM> of the tubing <NUM>, such air may remain lodged in the air-carrying portion <NUM>. Thus, the vent cap <NUM> may be designed to receive a volume of liquid <NUM> at least equal to the volume of the air-carrying portion <NUM>, as will be set forth in greater detail below.

Notably, the hydrophobic membrane <NUM> is only one example of many different vents that may be used within the scope of the present disclosure. Other structures (not shown) may be used in addition to or in the alternative to the hydrophobic membrane <NUM>. Such structures include, but are not limited to, a hydrophilic filter, a perforated cap, and a cap with one or more tortuous passageways. A hydrophilic filter may have passageways that permit air to flow therethrough, but may resist leakage of liquid due to attraction of the liquid <NUM> to the hydrophilic filter, and the formation of a liquid barrier that may therefore occur along the surface of the hydrophilic filter. A perforated cap may have a plurality of apertures, each of which is small enough to resist egress of the liquid <NUM> therethrough (due to surface tension effects), but large enough to permit passage of air therethrough. In a cap with one or more tortuous passageways the each passageway may be narrow, and may follow a lengthy and/or curved pathway that resists outflow of the liquid <NUM> due to surface tension effects and/or the head loss that occurs along the length of the passageway, while still permitting air to escape.

Returning to the embodiment of <FIG>, the vent cap <NUM> may have a chamber wall <NUM> that extends between the proximal end <NUM> and the distal end <NUM> of the vent cap <NUM>. The chamber wall <NUM> may define an exterior wall of the vent cap <NUM>, and may also define a chamber <NUM> within the vent cap <NUM>. As embodied in <FIG>, the chamber wall <NUM> may have a generally tubular shape, with some optional variations in diameter.

These variations in diameter may include a proximal flare <NUM> at which the chamber wall <NUM> joins the female tapered fitting <NUM> of the vent cap luer lock <NUM>. At the proximal flare <NUM>, the exterior of the diameter of the vent cap <NUM> may increase abruptly along the distal direction, i.e., from the proximal end <NUM> of the vent cap <NUM> to the main portion of the chamber wall <NUM>. The proximal flare <NUM> may help to define the chamber <NUM> such that the chamber <NUM> has a volume sufficient to enable passage of substantially all of the liquid <NUM> from the air-carrying portion <NUM> into the chamber <NUM>, as the priming of the intravenous delivery system <NUM> is completed and the leading edge of the liquid <NUM> advances from the distal end of the air-carrying portion <NUM> into the chamber <NUM>.

More specifically, the chamber <NUM> may have a generally cylindrical shape defined within the generally tubular shape of the chamber wall <NUM>. The chamber <NUM> may have a length <NUM> extending from the proximal flare <NUM> to the hydrophobic membrane <NUM>, and diameter, which may be an interior diameter <NUM> of the chamber wall <NUM>. The chamber <NUM> may not have a precisely cylindrical shape; however, the volume of the chamber <NUM> may be approximated by the formula Vc = πrc<NUM>lc, where lc is the length <NUM> of the chamber <NUM>, and rc, is the radius of the chamber <NUM>, which is half of the interior diameter <NUM> of the chamber <NUM>.

The dimensions of the chamber <NUM> may be determined by setting the volume Vc of the chamber <NUM> equal to the volume Vt of the air-carrying portion <NUM> of the tubing <NUM>. Thus, the equation πrc<NUM>lc = πrt<NUM>lt may be used to determine the dimensions of the chamber <NUM>. For example, given the exemplary dimensions of the air-carrying portion <NUM>, as set forth above, rt may be about <NUM> millimeters, or <NUM> meters, and lt may be about <NUM> inches, or about <NUM> meters. If the interior diameter <NUM> of the chamber <NUM> is to be <NUM> millimeters, the radius rc of the chamber <NUM> will be about <NUM> millimeters, or about <NUM> meters. Solving the equation above for lc provides that the length <NUM> of the chamber <NUM> should be about <NUM> millimeters, or <NUM> meters. In some embodiments, the length <NUM> of the chamber <NUM> may range from <NUM> millimeters to <NUM> millimeters, or more specifically, from <NUM> millimeters to <NUM> millimeters.

The variations in diameter of the chamber wall <NUM> may also include a distal flare <NUM>. At the distal flare <NUM>, the exterior diameter of the vent cap <NUM> may again increase abruptly along the distal direction, i.e., from the main portion of the chamber wall <NUM> to the distal end <NUM> of the vent cap <NUM>. The distal flare <NUM> may define a seat on which the hydrophobic membrane <NUM> may be secured, for example, via ultrasonic welding, as indicated previously. The vent cap <NUM> may be oriented upright, so that the hydrophobic membrane <NUM> is above the chamber <NUM>. In this manner, air <NUM> within the chamber <NUM> may float toward the hydrophobic membrane <NUM>, in the direction shown by the arrow <NUM>, and may exit the vent cap <NUM> through the hydrophobic membrane <NUM>.

In some alternative embodiments (not shown), a vent cap may have a chamber that is configured to facilitate and/or expedite air flow to the vent. For example, in place of a cylindrical shape, such a chamber may have different geometry that helps to wick the water away and/or allow the air to coalesce. Additionally or alternatively, an absorbent material such as a hydrophilic fibrous mat may be positioned within the chamber to facilitate such wicking and/or coalescing.

The intravenous delivery system <NUM> may be prepared for use according to a variety of methods. One example of the use of a system, such as the intravenous delivery system <NUM>, will be described in greater detail in connection with <FIG>, as follows.

Referring to <FIG>, a flowchart diagram illustrates a method <NUM> of preparing an intravenous delivery system for use, according to one embodiment. The method <NUM> will be described with reference to the intravenous delivery system <NUM> of <FIG> and <FIG>. However, those of skill in the art will recognize that the method <NUM> may be carried out with different intravenous delivery systems. Similarly, the intravenous delivery system <NUM> may be prepared for use through the use of methods other than that of <FIG>.

The method <NUM> may start <NUM> with a step <NUM> in which the various components of the intravenous delivery system <NUM> are connected together, except for the intravenous access unit <NUM>. Some of the components of the intravenous delivery system <NUM>, such as the tubing <NUM> and the vent cap <NUM>, may be packaged, sold and/or provided to the end user in a condition in which they are already connected together. The step <NUM> may only include interconnection of components of the intravenous delivery system <NUM> that have not already been connected together.

In a step <NUM>, the intravenous delivery system <NUM> may be primed. As indicate previously, this may be done by simply allowing the liquid <NUM> to flow through the tubing <NUM> to the vent cap <NUM> via gravity, or by squeezing or otherwise pressuring the drip unit <NUM>.

In a step <NUM>, the liquid <NUM> may be received in the vent cap <NUM>. As mentioned previously, the liquid <NUM> disposed within the air-carrying portion <NUM> when the liquid <NUM> has advanced to the distal end of the air-carrying portion <NUM> may be received within the chamber <NUM> of the vent cap <NUM>. The chamber <NUM> of the vent cap <NUM> may be deliberately sized to accomplish this.

In a step <NUM>, the air <NUM> may be vented from the intravenous delivery system <NUM>. This may entail permitting passage of the air <NUM> to the top of the chamber <NUM>, and through the hydrophobic membrane <NUM> of the vent cap <NUM>. The intravenous delivery system <NUM> may now be ready for attachment and use of the intravenous access unit <NUM>.

In a step <NUM>, the vent cap <NUM> may be detached from the second end <NUM> of the tubing <NUM>. This may entail detaching the vent cap luer lock <NUM> of the vent cap <NUM> from the tubing luer lock <NUM> of the second end <NUM> of the tubing <NUM>.

In a step <NUM>, the intravenous access unit <NUM> may be attached to the second end <NUM> of the tubing <NUM>. The first end <NUM> of the intravenous access unit <NUM> may have a luer lock that mates with the tubing luer lock <NUM> of the second end <NUM> of the tubing <NUM>. Thus, performance of this step may entail mating the luer lock of the first end <NUM> of the intravenous access unit <NUM> with the tubing luer lock <NUM> of the second end <NUM> of the tubing <NUM>.

The intravenous delivery system <NUM> is only one of many different possible embodiments of an intravenous delivery system, according to the present disclosure. In alternative embodiments, various different vent cap configurations may be provided. Such alternative vent cap configurations may advantageously be designed to retain the liquid <NUM> within the chamber <NUM> after detachment of the second end <NUM> of the tubing <NUM>, without requiring the presence of a valve as part of the vent cap <NUM>. Two such alternative embodiments will be shown and described in connection with <FIG>, as follows.

Referring to <FIG>, a front elevation, section view illustrates a vent cap <NUM> according to one alternative embodiment. The vent cap <NUM> may be a component of an intravenous delivery system like that of <FIG>, and may thus be detachably coupled to tubing, such as the distal end <NUM> of the tubing <NUM> of <FIG>. The vent cap <NUM> may have a proximal end <NUM> and a distal end <NUM>. The vent cap <NUM> may have some features similar to the corresponding features of the vent cap <NUM>, such as the vent cap luer lock <NUM> and the hydrophobic membrane <NUM>.

Like the vent cap <NUM>, the vent cap <NUM> may have a chamber wall <NUM> with a generally tubular shape that defines a chamber <NUM>. The chamber wall <NUM> may have a proximal flare <NUM> and a distal flare <NUM> that cooperate to define the extents of the chamber <NUM> and provide a seat for the hydrophobic membrane <NUM>. Like the chamber <NUM>, the chamber <NUM> may have a volume selected to enable the chamber <NUM> to receive substantially all of the liquid <NUM> contained in the air-carrying portion <NUM> of the distal end <NUM> of the tubing <NUM>, as the priming process reaches completion. This is likely the liquid <NUM> within which entrained air, if present, will reside. The air may be vented from the vent cap <NUM> through the hydrophobic membrane <NUM>, as in the vent cap <NUM>.

The vent cap <NUM> may be designed such that, after detachment of the vent cap <NUM> from the distal end <NUM> of the tubing <NUM>, the vent cap <NUM> retains substantially all of the liquid <NUM> contained within the chamber <NUM>, or in other words, substantially preventing flow of the liquid <NUM> out of the vent cap <NUM> through the orifice <NUM>. In this application, retaining "substantially all" of the liquid and "substantially preventing" flow of the liquid <NUM> through the orifice <NUM> do not require retention of <NUM>% of the liquid <NUM>. Rather, these phrases relate to retention enough of the liquid <NUM> that after detachment of the vent cap <NUM> from the distal end <NUM>, leakage of liquid <NUM> from within the chamber <NUM> is limited to a few drops of the liquid <NUM>.

The phrase "without requiring the presence of a valve within the vent cap" does not mean that there is no valve within a vent cap, but rather means that a function, such as prevention of outflow of the liquid <NUM> from the vent cap, does not require the use of a valve. A "valve" is device having at least one movable member that enables the valve to move between an open state, in which fluid flow through the valve is permitted, and a closed state, in which fluid flow through the valve is more restricted than in the open state.

In the embodiment of <FIG>, this may be accomplished through the use of an orifice <NUM>, which may be formed in the chamber wall <NUM> between the chamber <NUM> and the vent cap luer lock <NUM>. The orifice <NUM> may have a size selected such that substantially all of the liquid <NUM> is retained in the chamber <NUM> after detachment of the vent cap <NUM> from the distal end <NUM> of the tubing <NUM>. More specifically, the surface tension at the boundary between the liquid <NUM> and the ambient air proximate the orifice <NUM> may be sufficient to counteract any forces tending to remove the liquid <NUM> from the chamber <NUM> through the orifice <NUM>. Such forces may include gravity, as the vent cap <NUM> will likely be positioned with the orifice <NUM> below the liquid <NUM> in the chamber <NUM>, as illustrated in <FIG>, at the time it is detached from the distal end <NUM> of the tubing <NUM>.

Retention of the liquid <NUM> within the chamber <NUM> after detachment of the vent cap <NUM> from the tubing <NUM> may beneficially minimize spillage of the liquid <NUM>, and may help keep the clinical environment sterile. The orifice <NUM> represents only one mechanism for accomplishing this without requiring the presence of an internal valve. Another example will be shown and described in connection with <FIG>.

Referring to <FIG>, a front elevation, section view illustrates a vent cap <NUM> according to another alternative embodiment. The vent cap <NUM> may be a component of an intravenous delivery system like that of <FIG>, and may thus be detachably coupled to tubing, such as the distal end <NUM> of the tubing <NUM> of <FIG>. The vent cap <NUM> may have a proximal end <NUM> and a distal end <NUM>. The vent cap <NUM> may have some features similar to the corresponding features of the vent cap <NUM> and the vent cap <NUM>, such as the vent cap luer lock <NUM> and the hydrophobic membrane <NUM>.

Like the vent cap <NUM> and the vent cap <NUM>, the vent cap <NUM> may have a chamber wall <NUM> with a generally tubular shape that defines a chamber <NUM>. The chamber wall <NUM> may have a proximal flare <NUM> and a distal flare <NUM> that cooperate to define the extents of the chamber <NUM> and provide a seat for the hydrophobic membrane <NUM>. Like the chamber <NUM> and the chamber <NUM>, the chamber <NUM> may have a volume selected to enable the chamber <NUM> to receive substantially all of the liquid <NUM> contained in the air-carrying portion <NUM> of the distal end <NUM> of the tubing <NUM>, as the priming process reaches completion. This is likely the liquid <NUM> within which entrained air, if present, will reside. The air may be vented from the vent cap <NUM> through the hydrophobic membrane <NUM>, as in the vent cap <NUM> and the vent cap <NUM>.

Like the vent cap <NUM>, the vent cap <NUM> may be designed such that, after detachment of the vent cap <NUM> from the distal end <NUM> of the tubing <NUM>, the vent cap <NUM> retains substantially all of the liquid <NUM> contained within the chamber <NUM>. The vent cap <NUM> may have an orifice <NUM> formed in the chamber wall <NUM> between the chamber <NUM> and the vent cap luer lock <NUM>. The orifice <NUM> need not have any particular size. Rather, retention of the liquid <NUM> within the chamber <NUM> may be accomplished through the use of a hydrophilic membrane <NUM> that covers the orifice <NUM> and defines a boundary between the chamber <NUM> and the vent cap luer lock <NUM>. Due to the hydrophilic composition of the hydrophilic membrane <NUM>, the liquid <NUM> may adhere to the hydrophilic membrane <NUM>. This adherence may be sufficient to counteract forces, such as gravity, tending to cause the liquid <NUM> to exit the chamber <NUM> through the orifice <NUM>.

Claim 1:
An intravenous delivery system (<NUM>) comprising:
a liquid source (<NUM>) containing a liquid;
tubing (<NUM>) comprising:
a first end (<NUM>) connectable to the liquid source (<NUM>) to receive the liquid from the liquid source (<NUM>); and
a second end (<NUM>);
a drip unit (<NUM>) comprising a drip chamber (<NUM>), wherein the drip unit is connected to the liquid source to receive drops of the liquid from the liquid source within the drip chamber, wherein the drip unit is connected to the first end of the tubing to supply the liquid to the tubing via gravity feed and
a vent cap (<NUM>) comprising:
a proximal end (<NUM>) connectable to the second end (<NUM>) of the tubing (<NUM>) to receive the liquid from the tubing (<NUM>);
a distal end (<NUM>) comprising a hydrophobic membrane (<NUM>) that is substantially impermeable to the liquid and substantially permeable to air ;
a chamber (<NUM>), defined by a chamber wall (<NUM>) wherein the chamber is in communication with the hydrophobic membrane to facilitate passage of air from the liquid out of the vent cap through the hydrophobic membrane, wherein the hydrophobic membrane is positioned adjacent to the chamber,
a vent cap luer lock (<NUM>) extending from the proximal flare (<NUM>) and having a threaded interface (<NUM>), wherein the luer lock comprises a female tapered fitting (<NUM>), wherein the chamber wall (<NUM>) is shaped to have a proximal flare (<NUM>) that provides the chamber wall with an interior diameter greater than the largest interior diameter of the vent cap luer lock (<NUM>) , and
an orifice (<NUM>) formed in the chamber wall between the chamber and the vent cap luer lock,
CHARACTERIZED IN THAT
the chamber comprises a hydrophilic membrane (<NUM>) that covers the orifice and defines a boundary between the chamber (<NUM>) and the vent cap (<NUM>) luer lock (<NUM>) to retain the liquid (<NUM>) within the chamber.