Patent Publication Number: US-11644356-B2

Title: Priming valve to induce appropriate pressure and flow profile and improve sensor readiness

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 16/007,245, entitled “Priming Valve to Induce Appropriate Pressure and Flow Profile and Improve Sensor Readiness”, filed Jun. 13, 2018, which claims priority to U.S. Provisional Application Ser. No. 62/521,726, entitled “Priming Valve to Induce Appropriate Pressure and Flow Profile and Improve Sensor Readiness”, filed Jun. 19, 2017, the entire disclosures of each of which are hereby incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Disclosure 
     The present disclosure relates generally to a flow sensor system. More particularly, the present disclosure relates to a flow sensor system and a method of readying a flow sensor of the flow sensor system for characterizing at least one attribute of a fluid to be detected by the flow sensor. 
     2. Description of the Related Art 
     There is a need to improve volume accuracy in a bolus delivery using a medical device. It would be advantageous to provide a flow sensor system having a flow sensor with improved flow measurement characteristics. 
     SUMMARY OF THE INVENTION 
     The present disclosure provides a system for sensing a flow of a fluidic medicament. The system includes an intelligent injection port which may attach to an injection site (such as a “Y Site” or a stop cock) for manually administered IV injections. The system includes two main sub-assemblies: a single-use flow sensor and a reusable base unit, which fit together prior to use. The single-use flow sensor includes a flow tube sub-assembly. 
     In accordance with an example of the present invention, priming valve for a fluid sensor associated with a medical device may include a valve comprising a fluid flow path, a fluid inlet at a first end of the fluid flow path configured to couple to a fluid outlet of a fluid channel including at least one sensor configured to characterize at least one attribute of a fluid, a fluid outlet at a second end of the fluid flow path, a valve seat, and a connector that engages the valve seat to prevent fluid flow between the fluid inlet and the fluid outlet via the fluid flow path, wherein the connector is configured to move relative to the valve seat in response to a threshold pressure within the fluid flow path to allow the fluid to flow between the fluid inlet and the fluid outlet of the valve via the fluid flow path. 
     According to further examples, the threshold pressure is 5-50 psi. 
     According to further examples, the connector comprises a sidewall extending between an inlet end and an outlet end of the connector, wherein the valve seat comprises a sidewall extending between an inlet end and an outlet end of the valve seat, and wherein at least a portion of the valve seat extends within the connector such that an inner surface of the sidewall of the connector faces an outer surface of the sidewall of the valve seat. 
     According to further examples, the outer surface of the sidewall of the valve seat comprises a lip portion that extends radially outward from the sidewall of the valve seat, and wherein the inner surface of the sidewall of the connector is slidingly and sealingly engaged with the lip portion of the valve seat. 
     According to further examples, the lip portion of the valve seat comprises one of a molded lip seal and an o-ring. 
     According to further examples, an inner surface of the sidewall of the valve seat defines a first portion of the fluid flow path extending from the fluid inlet of the valve to at least one opening in the sidewall of the valve seat, wherein the at least one opening in the sidewall of the valve seat is located in a direction toward the fluid outlet of the valve with respect to the lip portion of the valve seat, and wherein the inner surface of the sidewall of the connector and the outer surface of the sidewall of the valve seat define a second portion of the fluid flow path extending from the opening toward the fluid outlet of the valve. 
     According to further examples, the connector is configured to move axially away from the inlet end of the valve seat in a direction toward the outlet end of the valve seat in response to the threshold pressure within the fluid flow path to allow the fluid to flow between the fluid inlet and the fluid outlet of the valve. 
     According to further examples, a portion of the sidewall of the connector extends radially inward at the inlet end of the connector. 
     According to further examples, the outer surface of the sidewall of the valve seat comprises at least one abutment surface that extends radially outward from the sidewall of the valve seat, wherein the at least one abutment surface is configured to engage the portion of the sidewall of the connector that extends radially inward to inhibit further movement of the connector axially away from the inlet end of the valve seat in the direction toward the outlet end of the valve seat. 
     According to further examples, the inner surface of the sidewall of the connector comprises at least one detent extending radially inward from the sidewall. 
     According to further examples, the outer surface of the sidewall of the valve seat comprises at least one abutment surface extending radially outward from the sidewall, wherein the at least one abutment surface is configured to engage the at least one detent to inhibit further movement of the connector axially away from the inlet end of the valve seat in the direction toward the outlet end of the valve seat. 
     According to further examples, the outer surface of the sidewall of the valve seat comprises at least one additional abutment surface extending radially outward from the sidewall, wherein the at least one additional abutment surface is located in a direction toward the inlet end of the valve seat with respect to the at least one abutment surface, and wherein the at least one additional abutment surface is configured to engage the at least one detent to inhibit movement of the connector axially toward the inlet end of the valve seat in a direction away from the outlet end of the valve seat. 
     According to further examples, the valve further comprises an additional fluid flow path between the fluid inlet and the fluid outlet of the valve. 
     According to further examples, the inner surface of the sidewall of the connector comprises an angled surface that extends radially inward toward the outlet end of the connector, wherein the outer surface of the sidewall of the valve seat comprises a valve seat surface, and wherein the angled surface of the connector engages the valve seat surface of the valve seat to prevent fluid flow between the fluid inlet and the fluid outlet via the fluid flow path. 
     According to further examples, the valve comprises a connection at the fluid outlet at the second end of the fluid flow path configured to connect to an inlet configured to deliver the fluid from the administrable fluid source to a fluid pathway that provides the fluid to said medical device. 
     In accordance with an example of the present invention, a flow sensor sub-assembly for sensing flow of a fluidic medicament may include at least one sensor of a fluid port configured to characterize at least one attribute of a fluid within an administrable fluid source, the fluid port comprising: a fluid channel, a fluid inlet at a first end of the fluid channel configured to couple to an outlet of an administrable fluid source, and a fluid outlet at a second end of the fluid channel; and a priming valve attached to the fluid outlet at the second end of the fluid channel, wherein the priming valve is configured to prevent fluid flow from the fluid outlet at the second end of the fluid channel when closed, and wherein the priming valve is configured to open to allow the flow of the fluid from the fluid outlet at the second end of the fluid channel in response a threshold pressure within the fluid channel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following descriptions of examples of the disclosure taken in conjunction with the accompanying drawings, wherein: 
         FIG.  1    is a distally-directed perspective view of a flow sensor system in accordance with one example of the present invention. 
         FIG.  2    is a distally-directed perspective view of a flow sensor system in accordance with one example of the present invention. 
         FIG.  3    is an exploded, perspective view of a flow sensor of a flow sensor system in accordance with an example of the present invention. 
         FIG.  4    is a perspective view of a flow sensor of a flow sensor system in accordance with an example of the present invention. 
         FIG.  5    is a graph showing signal level of a flow sensor of a flow sensor system as a function of time according to one example case. 
         FIG.  6    is a graph showing signal level of a flow sensor of a flow sensor system as a function of time according to another example case. 
         FIG.  7    is an exploded perspective view of a flow sensor system in accordance with one example of the present invention. 
         FIG.  8    is a schematic view of a priming valve in accordance with one example of the present invention. 
         FIG.  9    is a schematic view of a priming valve in accordance with one example of the present invention. 
         FIG.  10    is an exploded perspective view of a priming valve in accordance with one example of the present invention. 
         FIG.  11    is a schematic view of a priming valve in accordance with one example of the present invention. 
         FIG.  12    is a schematic view of a priming valve in accordance with one example of the present invention. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary examples of the disclosure, and such exemplifications are not to be construed as limiting the scope of the disclosure in any manner. 
     DETAILED DESCRIPTION 
     The following description is provided to enable those skilled in the art to make and use the described examples contemplated for carrying out the invention. Various modifications, equivalents, variations, and alternatives, however, will remain readily apparent to those skilled in the art. Any and all such modifications, variations, equivalents, and alternatives are intended to fall within the spirit and scope of the present invention. 
     For purposes of the description hereinafter, the terms “upper”, “lower”, “right”, “left”, “vertical”, “horizontal”, “top”, “bottom”, “lateral”, “longitudinal”, and derivatives thereof shall relate to the invention as it is oriented in the drawing figures. However, it is to be understood that the invention may assume various alternative variations, except where expressly specified to the contrary. 
     As used in the specification and the claims, the singular form of “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. 
     As used herein, “proximal” shall refer to a part or direction located away or furthest from a patient (upstream), while distal shall refer to a part or direction towards or located nearest to a patient (downstream). Also, a drug substance is used herein in an illustrative, non-limiting manner to refer to any substance injectable into the body of a patient for any purpose. Reference to a patient may be to any being, human or animal. Reference to a clinician may be to any person or thing giving treatment, e.g., a nurse, doctor, machine intelligence, caregiver, or even self-treatment. 
     As used herein, the phrase “inherently hydrophobic” refers to a surface that naturally excludes water molecules rather than by a process of drying, such as drying by hot air. 
     Unless otherwise indicated, all ranges or ratios disclosed herein are to be understood to encompass any and all subranges or subratios subsumed therein. For example, a stated range or ratio of “1 to 10” should be considered to include any and all subranges between (and inclusive of) the minimum value of 1 and the maximum value of 10; that is, all subranges or subratios beginning with a minimum value of 1 or more and ending with a maximum value of 10 or less, such as but not limited to, 1 to 6.1, 3.5 to 7.8, and 5.5 to 10. 
     Unless otherwise indicated, all numbers expressing quantities used in the specification and/or claims are to be understood as modified in all instances by the term “about.” 
     Flow Sensor System 
       FIGS.  1 - 4    illustrate an exemplary configuration of a flow sensor system  200  of the present disclosure. Referring to  FIGS.  1 - 4   , a flow sensor system  200  of the present disclosure includes two main assemblies which fit together prior to use: a flow sensor  210  and a base  220 . In one example, the flow sensor  210  can be a single-use flow sensor which is engageable with a reusable base  220 . The flow sensor system  200  is an intelligent injection port. The flow sensor system  200  is attachable to an injection site (“Y Site” or stop cock, for example) for manually administered IV injections. 
     The flow sensor system  200  of the present disclosure can reduce medication error at bedside during bolus delivery. The flow sensor system  200  of the present disclosure can also provide a record of and electronically measure bolus delivery, which allows monitoring bolus delivery and automatic documentation of bolus delivery as part of a patient&#39;s health record. The flow sensor system  200  of the present disclosure can also provide alerts when bolus delivery inconsistent with a patient&#39;s medical record is about to occur. 
     Referring to  FIGS.  1 - 4   , in one example, the base  220  is a non-sterile, reusable device that houses a battery, a scanner (either optical, mechanical, inductive, capacitive, proximity, or RFID), electronics, and a wireless transmitter. In some examples, the base  220  is battery powered and rechargeable. In some examples, each base  220  has a unique serial number imprinted on a surface of the base  220  or embedded therein that may be transmitted to a data system before use. The data system can be a local computer or tablet “computer”, a cellular phone, another medical device, or a Hospital Data System. 
     Referring to  FIGS.  1 - 4   , in one example, the base  220  is removably connectable to the flow sensor  210  and includes at least one deflectable wing tab  280  defining an opening for receiving at least a portion of the flow sensor  210  therein and for securing the flow sensor  210  within a portion of the base  220  prior to use. In one example, a pair of wing tabs  280  secure the flow sensor  210  within the base  220 . The wing tabs  280  may be flexible to the extent that they may be outwardly deflected to allow for passage of the flow sensor  210  thereover. In one example, the flow sensor  210  is a pre-sterilized disposable device having an injection port  130  and a distal tubing connection, such as a Luer tip  109 , which may be optionally covered by a Luer cap  108 . 
     With reference to  FIG.  3   , the flow sensor  210  may include a flow tube sub-assembly  10  consisting of a flow tube  100  having an outlet end  101  and an inlet end  102 . The outlet end  101  may be provided in fluid communication with an outlet tubing  110  having an outlet connection  105  including a Luer tip  109  which may be optionally covered by a flow restrictor, as described herein. In a preferred example, the outlet connection  105  is a plastic connector with a Luer tip  109 , however, any suitable method to inject the medicament into a patient is envisaged to be within an aspect of an example of the invention. For example, it may be desirable to replace the outlet connection  105  and tubing  110  with a needle for direct injection/infusion into a patient. 
     The inlet end  102  may be coupled to the reservoir of a medication pen or infusion reservoir. The inlet end  102  of the flow tube  100  may be provided in fluid communication with an injection port  130 , and may optionally include a connection such as a threaded Luer lock  131  which is engageable with a source of a fluid to be injected. A pierceable septum (not shown) may be provided with the injection port  130  for maintaining sterility prior to use. In one example, the flow tube  100  is comprised of a medical grade stainless steel and is approximately 50 mm long with a 1.0 mm inner diameter and a 1.6 mm outer diameter. 
     In one example, the flow sensor system  200  supports injections using any Luer-lock type syringe or liquid medicament container. Additionally, the flow sensor system  200  is designed to work with encoded syringes that have a special barcode identifier on the Luer collar of the syringe, called “encoding”. Preferably, encoded syringes include commercially-available drugs in prefilled syringes with a special barcode that stores information about the medication contained within the syringe. Encoded syringes are ready-to-use, passive, and disposable. The encoding syringes store the drug name and concentration contained within the syringe. Additional characteristics such as drug source, container size, drug manufacturer source, drug category color, among others, may also be included. When an encoded syringe is attached to the injection port  130  of the flow sensor  210 , this barcode information is read by a scanner in the base  220  and wirelessly transmitted by the flow sensor system  200  to the data system. Preferably, the 2-D barcodes will be added to syringes during the filling process. The flow sensor system  200  also accommodates syringes not having encoding. 
     The present disclosure provides a flow sensor sub-assembly for sensing flow of a fluidic medicament. The flow sensor  210  also includes a first piezo element or an upstream transducer  150  and a second piezo element or a downstream transducer  151 . The first piezo element  150  may be provided with an inlet fitting  180 , as shown in  FIG.  3   , for coupling with the injection port  130 . Similarly, the second piezo element  151  may be provided with an outlet fitting  190 , for coupling with the outlet tubing  110 . The first and second piezo elements  150  and  151  are configured to transmit an ultrasonic signal therebetween indicative of a flow of the fluidic medicament in the flow tube  100 . In an example, the first piezo element  150  and the second piezo element  151  are annular in shape and encircle the flow tube  100  at each respective mounting point. 
     The flow sensor  210  includes a first spring contact  750   a  and a second spring contact  750   b . In one example, the spring contacts  750   a ,  750   b  are secured to a base  700  that has a circuit for conducting an electrical signal to and from the spring contacts  750   a ,  750   b  to a microprocessor. The first spring contact  750   a  is in electrical communication with a first piezo element  150  and the second spring contact  750   b  is in electrical communication with a second piezo element  151 . The first spring contact  750   a  has a first contact force against the first piezo element  150  and the second spring contact  750   b  has a second contact force against the second piezo element  151 . The first contact force may be equivalent to the second contact force. The first and second piezo elements  150 ,  151  vibrate due to fluid flow through the flow tube  100  of the flow sensor  210 . Vibration of the first and second piezo elements  150 ,  151  creates an ultrasonic signal which can be detected and communicated electronically to the microprocessor. The microprocessor is configured to correlate the ultrasonic signal to a fluid flow rate through the flow tube  100  and provide a fluid flow rate output to the user. 
     Method of Readying a Flow Sensor 
     Referring to  FIGS.  1 - 2   , use of a flow sensor system  200  of the present disclosure will now be described. In one example, as the drug is injected, the flow sensor system  200  measures the volume dosed ultrasonically. In order to improve transmission of ultrasonic signals in the flow sensor  210 , the present disclosure proposes various examples of increasing a fluid pressure in the flow sensor  210 . 
     During manufacture, flow sensor  210  may be calibrated on a calibration bench. For example, a fluid, such as water, is flowed through the flow sensor  210  to calibrate the ultrasonic signal transmission between the first and second piezo elements  150  and  151 . Prior to packaging the flow sensor  210  for shipping, the flow sensor  210  may be dried, such as using hot air, to eliminate any residual fluid that may remain in the flow sensor  210 . Without intending to be bound by theory, hot air drying of the fluid path surfaces of the flow sensor  210  contributes to making these fluid path surfaces exhibit their inherently hydrophobic characteristics. In this manner, when the flow sensor  210  is readied for use by priming the flow sensor  210  with a priming fluid, the interior fluid path surface of the flow sensor  210  may not be fully wetted with the priming fluid. Because the flow sensor  210  is configured to generate ultrasonic signals corresponding to a flow rate of the fluid through contact with the internal flow path of the flow sensor  210 , the inherently hydrophobic characteristics of the interior surface of the fluid path contribute to a decrease in the ability of the flow sensor  210  to transmit ultrasonic waves. It has been found that wetting the internal surfaces of the flow path through the flow sensor  210 , such as by increasing a pressure or maintaining a pressure within the flow path, increases the ultrasonic signal transmission capability of the flow sensor  210 . 
     With reference to  FIG.  1   , a first method of readying the flow sensor  210  will now be described. In this example, the flow sensor system  200  is prepared for use by attaching the injection port  130  of the flow sensor system  200  to an administrable fluid source, such as a syringe  900  containing a fluid. In some examples, the syringe  900  may contain a priming fluid, such as saline. Prior to connecting the syringe  900 , the injection port  130  is desirably cleaned by swabbing the hub according to normal hospital procedure. The syringe  900  can be attached to the injection port  130  by rotating the syringe  900  about its longitudinal axis until the syringe  900  stops, i.e., a secure connection between the syringe  900  and the injection port  130  is made. The syringe  900  has a plunger  920  for delivering the priming fluid from an interior of the syringe  900  when the plunger  920  is pushed in a distal direction. 
     The outlet connection  105  is capped with a flow restrictor, such as a cap  910 . In some examples, the cap  910  is configured to interface with the Luer tip  109  of the outlet connection  105 . The cap  910  can be attached to the Luer tip  109  by rotating the cap  910  about its longitudinal axis until the cap  910  stops, i.e., a secure connection between the cap  910  and the Luer tip  109  is made. Once connected to the Luer tip  109 , the cap  910  blocks fluid flow from the outlet connection  105 . 
     Next, the plunger  920  of the syringe  900  is pushed in the distal direction to deliver fluid from the syringe  900 . Because the cap  910  prevents fluid from flowing out of the outlet connection  105 , the priming fluid from the syringe  900  builds fluid pressure within the flow sensor  210 . In some examples, the increased fluid pressure of 5-50 psi within the flow sensor  210  can be maintained for a predetermined period of time. For example, the predetermined period of time may be approximately 1-60 seconds. 
     While the flow sensor  210  is pressurized by the fluid from the syringe  900 , at least one first signal is generated by the flow sensor  210  to characterize at least one attribute of fluid. In various examples, the at least one attribute may be fluid flow rate and/or fluid pressure. The manual increase of fluid pressure within the flow sensor  210 , while keeping the outlet connection  105  capped, helps eliminate any air between the interior surface of the flow path of the flow sensor  210  and the fluid. In this manner, the interior surface of the flow path of the flow sensor  210  is fully wetted to allow for an increased ultrasonic signal transmission of the flow sensor  210 . 
     Next, the pressure on the plunger  920  of the syringe  900  can be released, and the cap  910  is removed from the Luer tip  109 . The outlet connection  105  is attached to an inlet of a fluid pathway (not shown) configured for delivering fluid from an administrable fluid source, such as the syringe  900 , to a patient. In some examples, the fluid pathway may be a catheter configured for connecting to a patient. Prior to connecting the fluid pathway to the patient, fluid from the syringe  900  is first expelled from the fluid pathway, such as during the priming of the fluid pathway. As the fluid is delivered from the syringe  900 , the fluid flows through the flow sensor  210  and out of the fluid pathway. In some examples, 2-7 ml of fluid may be delivered from the syringe  900  through the fluid pathway. The flow sensor  210  may generate at least one second signal of the same type as the first signal in order to characterize at least one attribute of the fluid. For example, the second signal may characterize the pressure and/or flow rate of fluid through the flow sensor  210 . In some examples, the second signal may be increased (i.e., have higher strength) than the first signal due to the internal surfaces of the flow path of the flow sensor  210  being fully wetted. For example, the second signal may be increased over the first signal by 120%, 160%, or 180%, inclusive of the values therebetween. The flow sensor  210  is now primed and ready for use in a fluid delivery procedure. 
     In various examples, the flow sensor  210  may be in communication with a controller  930 . The controller  930  may be configured for receiving information from the flow sensor  210 , such as receiving the at least one first signal and the at least one second signal. The controller  930  may be configured to determine that the at least one attribute of the fluid based on the received data from the at least one first signal and the at least one second signal matches at least one condition specified by at least one rule. For example, the controller  930  may be configured for identifying a type of fluid flowing through the flow sensor  210  based on a flow rate of the fluid through the flow sensor  210  for a given fluid pressure at a given fluid temperature. Without intended to be bound by theory, each fluid, such as a fluid medicament, has a unique ultrasonic signature as the fluid flows through the flow sensor  210 . The ultrasonic signature may be a function of fluid pressure, temperature, and material composition of the fluid. 
     In various examples, the controller  930  may generate at least one operation modification signal in response to the characterized at least one attribute matching at least one condition specified by at least one rule. For example, the controller  930  can execute a flow algorithm based on data representing characteristics or attributes of the fluid flow received from the piezo elements  150 ,  151 . In some examples, the syringe  900  may have indicia that, when read by a reading device of the flow sensor system  200  that is in operative communication with the controller  930 , causes the controller  930  to initiate a predetermined operating cycle. In some examples, the indicia may be a 2D or 3D barcode, QR code, or any other indicia capable of storing information that, when read by a reading device of the flow sensor system  200 , is configured to be interpreted as a set of instructions to be performed by the controller  930 . For example, the indicia, when read by the reading device, can cause the controller  930  to initiate a priming cycle for priming the flow sensor  210 . In some examples, the priming cycle may comprise generating at least one signal, such as a first signal and a second signal discussed herein. 
     The controller  930  may transmit, by a transmitter (not shown) the operation modification signal to at least one device. In some embodiments, if a fluid type is determined to be a different type than a desired fluid type, or if a flow rate is determined to be a different flow rate than a desired flow rate, the controller  930  can transmit an operation modification signal to a display and/or a data processing module that causes the module to display an alarm or alert or causes the module to transmit a signal back to the system  200  that stops the fluid flow. The controller  930  can further control the wireless transmitter to transmit injection data representing a type of medication, a dose of a medication, and/or a time of a dose of a medication to the display and/or data processing module. In some embodiments, the controller  930  can automatically transmit the data to the module in response to an automated injection. 
     With reference to  FIG.  5   , a graph depicting a percentage of signal strength of five flow sensors  210  as a function of time is shown in accordance with one example. Each flow sensor  210  was initially calibrated using a standard calibration routine. The signal readings from each of the flow sensors  210  after calibration are shown as point A on the graph. The flow sensors  210  were then dried with hot air and flushed with a priming fluid without being pressurized. Ultrasonic signal transmission readings were then recorded, shown as point B on the graph. From the graph in  FIG.  5   , it can be readily observed that signal strength drops for each of the flow sensors  210  after the flow sensors  210  have been dried with hot air. In order to increase the signal level, each flow sensor  210  was capped with a cap  910  and pressurized with a priming fluid, such as saline, for 60 seconds. After the expiration of the pressurization period, another signal reading was taken. Point C in  FIG.  5    illustrates that the signal level increases from Point B after the flow sensors  210  have been pressurized with a priming fluid. 
     With reference to  FIG.  2   , instead of capping the outlet connection  105  with a cap  910 , such as described herein with reference to  FIG.  1   , the outlet connection  105  may be connected to a vented flow restrictor, such as a vented cap  940 . In some examples, the vented cap  940  may be a needle having an inner diameter sufficiently small to be capable of generating back pressure in the flow sensor  210  when fluid is delivered from the syringe  900 . For example, the vented cap  940  may be a needle having an outlet of approximately 30 G (0.16 mm ID). In other examples, the vented cap  940  may have an inner diameter of 0.1-0.2 mm. The priming fluid delivered from the syringe  900  builds back pressure within the flow sensor  210 . In some examples, the increased fluid pressure of 5-50 psi within the flow sensor  210  can be maintained for a predetermined period of time. For example, the predetermined period of time may be approximately 1-60 seconds. 
     While the flow sensor  210  is pressurized by the fluid from the syringe  900 , at least one first signal is generated by the flow sensor  210  to characterize at least one attribute of fluid. In various examples, the at least one attribute may be fluid flow rate and/or fluid pressure. The manual increase of fluid pressure within the flow sensor  210 , while keeping the outlet connection  105  capped, helps eliminate any air between the interior surface of the flow path of the flow sensor  210  and the fluid. In this manner, the interior surface of the flow path of the flow sensor  210  is fully wetted to allow for an increased ultrasonic signal transmission of the flow sensor  210 . 
     Next, the pressure on the plunger  920  of the syringe  900  can be released, and the vented cap  940  is removed from the Luer tip  109 . The outlet connection  105  is attached to an inlet of a fluid pathway (not shown) configured for delivering fluid from an administrable fluid source, such as the syringe  900 , to a patient. In some examples, the fluid pathway may be a catheter configured for connecting to a patient. Prior to connecting the fluid pathway to the patient, fluid from the syringe  900  is first expelled from the fluid pathway, such as during the priming of the fluid pathway. As the fluid is delivered from the syringe  900 , the fluid flows through the flow sensor  210  and out of the fluid pathway. In some examples, 2-7 ml of fluid may be delivered from the syringe  900  through the fluid pathway. The flow sensor  210  may generate at least one second signal of the same type as the first signal in order to characterize at least one attribute of the fluid. For example, the second signal may characterize the pressure and/or flow rate of fluid through the flow sensor  210 . In some examples, the second signal may be increased (i.e., have higher strength) than the first signal due to the internal surfaces of the flow path of the flow sensor  210  being fully wetted. For example, the second signal may be increased over the first signal by 120%, 160%, or 180%, inclusive of the values therebetween. The flow sensor  210  is now primed and ready for use in a fluid delivery procedure. 
     With reference to  FIG.  6   , a graph depicting signal level of three flow sensors  210  (labeled 1, 2, 3) as a function of time is shown in accordance with another example. Each flow sensor  210  was provided with a vented cap  940  having a 30 G needle. A signal count was recorded (Point D) during a delivery of 2 ml of fluid from the syringe  900 . The vented cap  940  was then removed from each flow sensor  210  and a signal count illustrative of a pressure drop was recorded (Point E). From the graph in  FIG.  6   , it can be readily observed that signal strength drops for each of the flow sensors  210  after the vented cap  940  is removed from the flow sensors  210 . After removing the vented cap  940 , 7 ml of fluid was delivered from the syringe  900  through each flow sensor  210 . During this step, signal count increased and stabilized at a high value (Point F). A signal level of a fourth flow sensor  210  (labeled 4 in  FIG.  6   ), which has been primed without using the vented cap  940 , is shown as a comparative example. The signal strength of the fourth flow sensor  210  is significantly lower than a signal strength of flow sensors  210  that were readied using the vented cap  940  in a manner described herein with reference to  FIG.  2   . 
     Flow Sensor System Relief Valve 
     With reference to  FIG.  7   , instead of capping the outlet connection  105  with a cap  910 , such as described herein with reference to  FIG.  1   , or a vented flow restrictor, such as a vented cap  940  described herein with reference to  FIG.  2   , the outlet connection  105  may be connected to a priming valve  950  as shown in  FIG.  7   . In some examples, the priming valve  950  is configured to interface with the Luer tip  109  of the outlet connection  105 . The priming valve  950  can be attached to the Luer tip  109  by rotating the priming valve  950  about its longitudinal axis until the priming valve  950  stops, i.e., a secure connection between the priming valve  950  and the Luer tip  109  is made. 
     Once connected to the Luer tip  109 , the priming valve  950 , when closed, prevents fluid flow from the outlet connection  105  as described in more detail herein. The priming valve  950  is configured to open to allow fluid flow from the outlet connection  105  in response a threshold pressure within the flow sensor  210 . For example, the outlet tubing  110  includes a fluid channel between a fluid inlet in fluid communication with the outlet end  101  of the flow tube  100  of flow sensor sub-assembly  10  and the outlet connection  105 , and the priming valve  950  attached to the outlet connection  105  can be configured to open to allow the flow of the fluid from the outlet connection  105  in response a threshold pressure within the fluid channel of the outlet tubing  110 . 
     Referring now to  FIGS.  8  and  9   , the priming valve  950  includes a fluid flow path  952 , a fluid inlet  954  at a first end of the fluid flow path  952  configured to couple to the outlet connection  105 , a fluid outlet  956  at a second end of the fluid flow path  952 , a valve seat  970 , and a connector  980  that engages the valve seat  970  to prevent fluid flow between the fluid inlet  954  and the fluid outlet  956  via the fluid flow path  952 . The connector  980  is configured to move relative to the valve seat  970  in response to a threshold pressure within the fluid flow path  952  to allow fluid flow between the fluid inlet  954  and the fluid outlet  956  of the priming valve  950  via the fluid flow path  952 . In some implementations, the threshold pressure can be 5-50 psi. For example, the connector  980  may be configured to remain engaged with the valve seat  970  until a pressure of 50 psi is present in the fluid flow path  952  that causes the connector  980  to move relative to the valve seat  970 . 
     The valve seat  970  includes a sidewall  972  extending between an inlet end  972   a  and an outlet end  972   b  of the valve seat  970 . The connector  980  includes a sidewall  982  extending between an inlet end  982   a  and an outlet end  982   b  of the connector  980 . In some implementations, the sidewalls  972 ,  982  can be cylindrical sidewalls forming a cylindrically shaped valve seat  970  and a cylindrically shaped connector  980 . At least a portion of the valve seat  970  extends within the connector  980 , e.g., coaxially within the connector  980  as shown in  FIGS.  8  and  9   , such that an inner surface  983   a  of the sidewall  982  of the connector  980  faces an outer surface  973   b  of the sidewall  972  of the valve seat  970 . 
     The outer surface  973   b  of the sidewall  972  of the valve seat  970  comprises a lip portion  974  that extends radially outward from the sidewall  972  of the valve seat  970 . For example, a diameter of the valve seat  970  at the lip portion  974  is greater than a diameter of the remainder of the valve seat  970 . The inner surface  983   a  of the sidewall  982  of the connector  980  is slidingly and sealingly engaged with the lip portion  974  of the valve seat  970 . For example, the lip portion  974  of the valve seat  970  may include a molded lip seal, e.g., as shown in  FIG.  10   , or an o-ring configured to form a fluid tight seal with the inner surface  983   a  of the sidewall  982  of the connector  980  while still enabling the sidewall  982  of the connector  980  to slide along the lip portion  974 . 
     An inner surface  973   a  of the sidewall  972  of the valve seat  970  defines a first portion of the fluid flow path  952  extending from the fluid inlet  954  of the priming valve  950  to at least one opening  990  in the sidewall  972  of the valve seat  970 . The at least one opening  990  in the sidewall  972  of the valve seat  970  is located in a direction toward the fluid outlet  956  of the priming valve  950  with respect to the lip portion  974  of the valve seat  970 . For example, as shown in  FIGS.  8  and  9   , two openings  990  are located on opposite sides of the sidewall  972  and to the right of the lip portion  974  towards the fluid outlet  956 . Evenly spaced openings, such as the two openings  990  shown in  FIGS.  8  and  9    enable the pressure in the fluid flow path to be more evenly distributed within the priming valve  970  and on the connector  980 . The inner surface  983   a  of the sidewall  982  of the connector  980  and the outer surface  973   b  of the sidewall  972  of the valve seat  970  define a second portion of the fluid flow path  952  extending from the opening(s)  990  toward the fluid outlet  956  of the priming valve  950 . 
     The connector  980  is configured to move axially away from the inlet end  972   a  of the valve seat  970  in a direction toward the outlet end  972   b  of the valve seat  970  in response to the threshold pressure within the fluid flow path  952  to allow the fluid to flow between the fluid inlet  954  and the fluid outlet  956  of the valve  950  via the fluid flow path  952 . 
     In some examples, a portion of the sidewall  982  of the connector  980  can extend radially inward at the inlet end  982   a  of the connector  980 . For example, as shown in  FIGS.  8  and  9   , retainer  984  can extend radially inward at the inlet end  982   a  of the connector  980 . The retainer  984  extends radially inward farther than the lip portion  974  extends radially outward. The outer surface  973   b  of the sidewall  972  of the valve seat  970  comprises at least one abutment surface  976  that extends radially outward from the sidewall  972  of the valve seat  970 . For example, a height of the lip portion  974  facing toward the fluid inlet  954  of the priming valve  950  can form the at least one abutment surface  976 . The at least one abutment surface  976  is configured to engage the retainer  984  to inhibit further movement of the connector  980  axially away from the inlet end  972   a  of the valve seat  970  in the direction toward the outlet end  972   b  of the valve seat  970 . For example, the connector  980  is enabled to move relative to the valve seat  970  a sufficient distance to open the fluid flow path  952  at the fluid outlet  956  of the priming valve  950  to a desired or predetermined width, (e.g., to achieve a desired flow rate based on the threshold pressure in the fluid flow path  952  and/or a flow rate and volume of a fluid delivered/to be delivered via the fluid flow path  952 ), after which the connector  980  is prevented from any further movement in that direction by the retainer  984  engaging the at least one abutment surface  956 . The retainer  984  may be formed by applying heat and/or ultrasonic waves to the sidewall  982  of the connector  980  to extend the sidewall  982  radially inward. 
     In another example, as shown in  FIG.  11   , the inner surface  983   a  of the sidewall  982  of the connector  980  can include at least one detent  986  extending radially inward from the sidewall  982 . The at least one detent  986  may be located at any position along the sidewall  982  between the inlet end  982   a  of the sidewall  982  and the lip portion  974  of the valve seat  970  when the priming valve  950  is in the closed position. The at least one abutment surface  976  is configured to engage the at least one detent  986  to inhibit further movement of the connector axially away from the inlet end  972   a  of the valve seat  970  in the direction toward the outlet end  972   b  of the valve seat  970 . A location of the at least one detent  986  may be selected to enable the connector  980  to move relative to the valve seat  970  a sufficient distance to open the fluid flow path  952  at the fluid outlet  956  of the priming valve  950  to a desired or predetermined width, (e.g., to achieve a desired flow rate based on the threshold pressure in the fluid flow path  952  and/or a flow rate and volume of a fluid delivered/to be delivered via the fluid flow path  952 ), after which the connector  980  is prevented from any further movement in that direction by the at least one detent  986  engaging the at least one abutment surface  956 . 
     In one implementation, the outer surface  973   b  of the sidewall  972  of the valve seat  970  may include at least one additional abutment surface  978  extending radially outward from the sidewall  972 . The at least one additional abutment surface  978  is located in a direction toward the inlet end  972   a  of the valve seat  970  with respect to the at least one abutment surface  976 . The at least one additional abutment surface  978  is configured to engage the at least one detent  986  to inhibit movement of the connector  980  axially toward the inlet end  972   a  of the valve seat  970  in a direction away from the outlet end  972   a  of the valve seat  970 . The at least one detent  986  and the additional abutment surface  978  may be configured such that when a predetermined pressure or the threshold pressure is applied to the fluid flow path  952  the at least one detent can overcome the additional abutment surface  978 , e.g., through deformation of the additional abutment surface  978 , the detent  986 , and/or the sidewall  982  of the connector  980 , enabling further movement of the connector  980  axially away from the inlet end  972   a  of the valve seat  970  in the direction toward the outlet end  972   b  of the valve seat  970 . After overcoming the additional abutment surface  978 , engagement of an opposite face of the additional abutment surface  978  with the at least one detent  976  can act to inhibit the connector  980  from returning to the closed position by inhibiting movement of the connector axially toward the inlet end  972   a  of the valve seat  970  in the direction away from the outlet end  972   b  of the valve seat  970 . It is noted that it can be beneficial to form the connector  980  as two separate pieces, e.g., as shown in  FIG.  11   , if detents  986  are included to retain the valve seat  970 , with the two separate pieces being welded together after the valve seat  970  is assembled onto the inlet end  982   a  (left half in  FIG.  11   ) of the connector. 
     In some examples, the priming valve  950  may include an additional fluid flow path  992  between the fluid inlet  954  and the fluid outlet  956  of the priming valve  950 . The additional fluid flow path  992  can be sized and shaped to provide a visual indication of mist formation and/or to control back pressure within the fluid flow path  952 . In some implementations, the additional fluid flow path  992  may be a needle having an inner diameter sufficiently small to be capable of generating back pressure in the flow sensor  210  when fluid is delivered from the syringe  900 . For example, the additional fluid flow path  992  may be a needle having an outlet of approximately 30 G (0.16 mm ID). In other examples, the additional fluid flow path  992  may have an inner diameter of 0.1-0.2 mm. The priming fluid delivered from the syringe  900  builds back pressure within the flow sensor  210 . In some examples, the increased fluid pressure of 5-50 psi within the flow sensor  210  can be maintained for a predetermined period of time. For example, the predetermined period of time may be approximately 1-60 seconds. 
     The inner surface  983   a  of the sidewall  982  of the connector  980  can include an angled surface  987  that extends radially inward toward the outlet end  982   b  of the connector  980  and beyond the outlet end  972   b  of the valve seat  970 . The outer surface  973   b  of the sidewall  972  of the valve seat  970  includes a valve seat surface  977 , and the angled surface  987  of the connector  980  can engage the valve seat surface  977  of the valve seat  970  to prevent fluid flow between the fluid inlet  954  and the fluid outlet  956  via the fluid flow path  952 . The priming valve  950  may include a valve outlet connection  999  at the fluid outlet  954  at the second end of the fluid flow path  952  configured to connect to an inlet configured to deliver the fluid from the administrable fluid source to a fluid pathway that provides the fluid to a medical device. For example, the valve outlet connection  999  may be a Luer-Lok connection or Luer Slip connection. 
     Method of Readying a Flow Sensor System with a Relief Valve 
     The priming valve  950  can be used instead of the cap  910  or the vented cap  940  in use of a flow sensor system  200  of the present disclosure as described herein in the section titled “Method of Readying a Flow Sensor”, accordingly its use therein is described only briefly below. For example, while the flow sensor  210  is pressurized by the fluid from the syringe  900 , at least one first signal is generated by the flow sensor  210  to characterize at least one attribute of fluid. In various examples, the at least one attribute may be fluid flow rate and/or fluid pressure. The manual increase of fluid pressure within the flow sensor  210 , while keeping the outlet connection  105  capped, helps eliminate any air between the interior surface of the flow path of the flow sensor  210  and the fluid. In this manner, the interior surface of the flow path of the flow sensor  210  is fully wetted to allow for an increased ultrasonic signal transmission of the flow sensor  210 . 
     When the fluid pressure within the flow sensor  210  reaches the threshold pressure of the priming valve  950 , which until this point has been closed to prevent fluid flow from the outlet connection  105 , the priming valve opens to allow the flow of the fluid from the outlet connection  105 . The priming valve is formed and configured such that the threshold pressure results in the interior surface of the flow path of the flow sensor  210  being fully wetted to allow for an increased ultrasonic signal transmission of the flow sensor  210  before the priming valve  950  opens to release the pressure. In some examples, the increased fluid pressure of 5-50 psi within the flow sensor  210  can be maintained for a predetermined period of time before the threshold pressure is reached. For example, the predetermined period of time may be approximately 1-60 seconds. The opening of the priming valve  950  can provide an indication to a medical practitioner that sufficient pressure within the flow sensor  210  has been achieved to ensure that the flow sensor  210  is fully wetted. 
     Next, the pressure on the plunger  920  of the syringe  900  can be released and the valve outlet connection  999  is attached to an inlet of a fluid pathway (not shown) configured for delivering fluid from an administrable fluid source, such as the syringe  900 , to a patient. Alternatively, after the pressure on the plunger  920  of the syringe  900  is be released, and the priming valve  950  can be removed from the Luer tip  109 , and the outlet connection  105  is attached to an inlet of a fluid pathway (not shown) configured for delivering fluid from an administrable fluid source, such as the syringe  900 , to a patient. In some examples, the fluid pathway may be a catheter configured for connecting to a patient. Prior to connecting the fluid pathway to the patient, fluid from the syringe  900  is first expelled from the fluid pathway, such as during the priming of the fluid pathway, which can be performed with the priming valve still attached to the outlet connection  105 , thereby providing an additional ease of use for medical practitioners. As the fluid is delivered from the syringe  900 , the fluid flows through the flow sensor  210  and out of the fluid pathway. In some examples, 2-7 ml of fluid may be delivered from the syringe  900  through the fluid pathway. The flow sensor  210  may generate at least one second signal of the same type as the first signal in order to characterize at least one attribute of the fluid. For example, the second signal may characterize the pressure and/or flow rate of fluid through the flow sensor  210 . In some examples, the second signal may be increased (i.e., have higher strength) than the first signal due to the internal surfaces of the flow path of the flow sensor  210  being fully wetted. For example, the second signal may be increased over the first signal by 120%, 160%, or 180%, inclusive of the values therebetween. The flow sensor  210  is now primed and ready for use in a fluid delivery procedure. 
     Method of Using the Flow Sensor System 
     To use a primed flow sensor system  200 , a user attaches the flow sensor  210  to the base  220  by joining the flow sensor  210  (tubing side) and base  220  front sections first, and then snapping the two together. Preferably, an audible snapping sound is heard to indicate a secure connection between the flow sensor  210  and the base  220 . In one example, connecting the flow sensor  210  to the base  220  automatically powers on the flow sensor system  200 . In one example, the connection of the flow sensor  210  to the base  220  is verified by a blinking light on the base  220 . In other examples, other indicators may be used. 
     The flow sensor system  200  is now ready for delivery of IV medications. In one example, in the event of a flow sensor system  200  failure (excluding the IV fluid pathway), the flow sensor system  200  will still allow standard medication or fluid delivery through the port. 
     Next, giving an injection using the flow sensor system  200  will be discussed. First, the injection port  130  is cleaned by swabbing the hub according to normal hospital procedure. Next, a syringe  900  can be attached to the injection port  130  of the flow sensor  210  by completely rotating the syringe  900  until the syringe  900  stops, i.e., a secure connection between the syringe  800  and the injection port  130  is made. Ideally, the caregiver double checks each medication name and concentration on the syringe  900  prior to attachment to the injection port  130  to assure the correct medication is given. 
     The flow sensor  210  can be disposed after the flow sensor  210  is used to sense the flow of at least one fluidic medicament. The flow sensor base  220  can be used with a plurality of different flow sensors  210 . 
     While this disclosure has been described as having exemplary designs, the present disclosure can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as they become within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.