Patent Publication Number: US-2021161515-A1

Title: Devices and methods for delivering powdered agents

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of priority to U.S. Provisional Patent Application No. 62/942,898, filed Dec. 3, 2019, the entirety of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Various aspects of the disclosure relate generally to devices and methods for delivering agents. More specifically, aspects of the disclosure relate to devices for delivery of powdered agents, such as hemostatic agents. 
     BACKGROUND 
     In certain medical procedures, it may be necessary to stop or minimize bleeding internal to the body. For example, an endoscopic medical procedure may require hemostasis of bleeding tissue within the gastrointestinal tract, for example in the esophagus, stomach, or intestines. 
     During an endoscopic procedure, a user inserts a sheath of an endoscope into a body lumen of a patient. The user utilizes a handle of the endoscope to control the endoscope during the procedure. Tools are passed through a working channel of the endoscope via, for example, a port in the handle, to deliver treatment at the procedure site near a distal end of the endoscope. The procedure site is remote from the operator. 
     To achieve hemostasis at the remote site, a hemostatic agent may be delivered by a device inserted into the working channel of the endoscope. Agent delivery may be achieved through mechanical systems, for example. Such systems, however, may require numerous steps or actuations to achieve delivery, may not achieve a desired rate of agent delivery or a desired dosage of agent, may result in the agent clogging portions of the delivery device, may result in inconsistent dosing of agent, or may not result in the agent reaching the treatment site deep within the GI tract. The current disclosure may solve one or more of these issues or other issues in the art. 
     SUMMARY 
     Each of the aspects disclosed herein may include one or more of the features described in connection with any of the other disclosed aspects. 
     In an example, a device for delivering an agent may comprise a source of agent; a mixing chamber for receiving fluid and the agent; an outlet in fluid communication with the mixing chamber to deliver the fluid and the agent; and an actuator configured to (1) deliver a first flow of the fluid substantially free from the agent through the outlet; (2) after delivering the first flow, deliver a second flow of the fluid and the agent through the outlet; and (3) after delivering the second flow, deliver a third flow of the fluid substantially free from the agent through the outlet. 
     Any of the devices disclosed herein may include any of the following features. The actuator may transition from a first configuration to a second configuration. In the first configuration, the source of agent may not be in fluid communication with the mixing chamber. In the second configuration, the source of agent may not be in fluid communication with the mixing chamber. The actuator may include a valve defining an opening. In the first configuration, the opening may not be in fluid communication with the source of agent. In the second configuration, the opening may not be in fluid communication with the source of agent. The valve may include a first portion and a second portion. A spring may connect the first portion to the second portion. The valve may be able to transition from the first configuration to the second configuration only when a flow of the fluid is flowing through the mixing chamber. The actuator may include a body pivotable via at least one of a piston or a wire. The actuator may include a first rigid member and a second rigid member. The first rigid member may be pivotably coupled to the second rigid member. The second rigid member may include a trigger. The actuator may include a rotatable member having at least one blade extending from the rotatable member. The actuator may further include a gear. The actuator may include a first actuator for controlling a flow of the agent from the source of agent and a second actuator for controlling a flow of the fluid. The first actuator and the second actuator may be configured to be independently activated. The first actuator may be activated only if the second actuator is activated. The actuator may include a spring and a button valve. The actuator may include a first portion; a second portion defining an opening; and a spring extending from the first portion to the second portion. In the first configuration and the third configuration, the opening may not be in fluid communication with the source of agent. In the second configuration, the opening may not be in fluid communication with the source of agent. The agent may include a powder. The actuator may define an opening. In the first configuration and the third configuration, the opening may not be in fluid communication with the source of agent. In the second configuration, the opening may be in fluid communication with the source of agent such that the powder can pass through the opening. 
     In another example, a device for delivering an agent may comprise: a source of fluid; a source of powderized agent; a mixing chamber for receiving the fluid and the powderized agent; and an actuator configured to transition from a first configuration to a second configuration. In the first configuration, the source of agent may not be in fluid communication with the mixing chamber and a first flow of fluid substantially free from agent is received in the mixing chamber. In the second configuration, the source of agent may be in fluid communication with the mixing chamber and the powderized agent and a second flow of fluid are received in the mixing chamber. 
     Any of the devices disclosed herein may have any of the following features. The actuator may be further configured to transition from the second configuration to the first configuration after transitioning form the first configuration to the second configuration. 
     In an example, a method of delivering an agent may comprise: activating an actuator to cause: delivering a first flow of fluid, wherein the fluid is substantially free from a agent; after delivering the first flow, delivering a second flow of the fluid combined with the agent; and after delivering the second flow, delivering a third flow of fluid, wherein the fluid is substantially free from a agent. 
     Any of the methods or devices disclosed herein may include any of the following features. The agent may include a hemostatic agent. The fluid may be a pressurized fluid. During the delivering of the first flow and the third flow, an opening of the actuator may not be in fluid communication with a source of the agent. During the delivering of the second flow, an opening of the actuator may be in fluid communication with the source of the agent. 
     It may be understood that both the foregoing general description and the following. It may be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. As used herein, the terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term “exemplary” is used in the sense of “example,” rather than “ideal.” The term “distal” refers to a direction away from an operator, and the term “proximal” refers to a direction toward an operator. The term “approximately,” or like terms (e.g., “substantially”), includes values +/−10% of a stated value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate aspects of the disclosure and together with the description, serve to explain the principles of the disclosure. 
         FIGS. 1A-1C  show aspects of an exemplary delivery device. 
         FIGS. 2A-7D  show various example actuation mechanisms for use of a delivery device, including in the delivery device of  FIGS. 1A-1C . 
     
    
    
     DETAILED DESCRIPTION 
     A dual-stage actuation mechanism may be used to deliver an agent (e.g., a powdered agent) from a delivery system to a site of a medical procedure. The actuation mechanism may function to, upon activation, first deliver a flow of fluid, without the agent, through the delivery system and to the site. Then, a combined flow of the fluid and the agent may be delivered. Following delivery of a desired amount of the agent, the fluid may again be delivered without the agent. Delivery of fluid alone, before and after delivery of the agent, may facilitate flushing of components of the delivery system and may prevent clogging of the delivery system. 
       FIG. 1A  shows a delivery system  10 , which may be a powder delivery system. Delivery system  10  may include a body  12 . Body  12  may have a variety of features, to be discussed in further detail herein. The features described herein may be used alone or in combination and are not mutually exclusive. Like reference numbers and/or terminology are used to denote similar structures, when possible. 
       FIG. 1B  shows a cross-section of an exemplary body  12 , which may be a component of delivery system  10 . Body  12  may include or may be configured to receive an enclosure  14  (or other source) storing an agent  16 . Enclosure  14  may be screwed onto body  12  for providing agent  16  to body  12 , or a lid/store of agent  16  may be screwed onto enclosure  14  for supplying agent  16  to enclosure  14 . Agent  16  may be, for example, a powdered agent, such as a hemostatic agent. Agent  16  may alternatively be another type of agent or form of agent (e.g., a liquid or gel agent) and may have any desired function. Enclosure  14  may be removably attached to other components of delivery system  10 , including components of body  12 . Body  12  may have an agent inlet  18  in fluid communication with enclosure  14  for receiving agent  16  from enclosure  14 . Body  12  may include a fluid inlet  20  for receiving fluid, such as pressurized fluid, from a source  24  (e.g., a disposable canister, a tank, a supply line, etc.). 
     Body  12  may include a nozzle  22 , shown separately in  FIG. 1C . Nozzle  22  may include a nozzle chamber  25 , which may be in fluid communication with source  24 . Nozzle chamber  25  may terminate in an opening  26 . A diameter of nozzle opening  26  may be between 0.015 and 0.030 inches (e.g., 0.020 inches). Opening  26  may be positioned approximately along a longitudinal axis of agent inlet  18 . Opening  26  may be positioned behind, slightly behind, slightly in front of, or directly in front of agent inlet  18 . 
     Opening  26  may be in fluid communication with a mixing body  27  defining a mixing chamber  28  for combining agent  16  with fluid from source  24 . Nozzle  22  may connect with mixing body  27  of body  12  via any suitable fastening method (e.g., nuts, bolts, being formed of a continuous material with mixing body  27 , etc.) An O-ring  29   a  may sit in an annular seat  29   b  of nozzle  22  so as to provide a seal between nozzle  22  and mixing body  27 . Mixing body  27  may connect with enclosure  14  via any suitable fastening method (such as screwing onto mixing body  27 , as shown) and may also include seals  31 ,  32  to provide seals between enclosure  14  and mixing body  27  or other portions of body  12 . 
     A combination of agent  16  and fluid may be delivered from outlet  34  of body  12 . Outlet  34  may be in fluid communication with a catheter  36  (see  FIG. 1A ) or other component for delivering the combination of agent  16  and fluid to a desired location within a body lumen of a patient. Mixing chamber  28  may be in fluid communication with outlet  34  and mixing chamber  28  and/or outlet  34  may be configured to allow for fluid connection with catheter  36 . A diameter/width of outlet  34  may be the same as or approximately the same as a diameter/width of catheter  36  or an internal lumen of catheter  36 . A lack of edges formed between mixing body  27  (including mixing chamber  28  and outlet  34 ) may reduce clogging of agent passing into catheter  36 . A catheter may have an inner diameter of 0.080 inches, 0.050 inches, or 0.030 inches, for example, and mixing chamber  28 , outlet  34 , and or/mixing body  27  may be dimensioned for compatibility with those sizes of catheter. 
     Delivery system  10  may include an actuation mechanism  30  for controlling a release of agent  16  and/or fluid via outlet  34 . For example, actuation mechanism  30  may include a trigger, button, slider, knob, lever, or other suitable mechanism. Actuation mechanism may cause agent  14  and/or fluid to enter mixing chamber  28 , where agent  14  and fluid may be combined. As discussed below, delivery system  10  may include more than one actuation mechanism  30 . For example, multiple actuation mechanisms  30  may be used to separately control a flow of fluid through fluid inlet  20  and a flow of agent from enclosure  14  through agent inlet  18 . 
       FIGS. 2A-2C  show cross-sectional views of an exemplary body, which may be a component of delivery system  10 . Body  112  may include an agent inlet  118 , which may be in fluid communication with enclosure  14  storing an agent  16 . Agent inlet  118  may be appropriately sized so as to allow passage of agent  16  therethrough. Agent inlet  118  may have approximately the same size as opening  152 , described below. Agent inlet  118  may be an opening formed in body  112 . Agent inlet  118  may be a portion of enclosure  14 , particularly where enclosure  14  is not detachable from body  112 . Alternatively, enclosure  14  may include an opening formed therein, which may be in fluid communication with agent inlet  118 . Body  112  also may include a fluid inlet  120  for receiving fluid from source  24  (see  FIG. 1C ). The arrow in  FIG. 2B  shows the direction of fluid flow into inlet  120 . Body  112  may also include a valve  138  for controlling flow of fluid through fluid inlet  120  and agent  16  through agent inlet  118 . Valve  138  may be operatively connected to actuation mechanism  30  (see  FIG. 1A ). 
     Valve  138  may include a first portion  140 . First portion  140  may have a first seal  142  and a second seal  144  received thereon. First seal  142  and/or second seal  144  may be, for example, O-ring seals. First portion  140  may also include a neck portion  148 , between first seal  142  and second seal  144 . Neck portion  148  may have a smaller cross-sectional diameter than other portions of first portion  140  (e.g., those receiving first seal  144  and second seal  146 ). 
     Valve  138  may also include a second portion  150 . Second portion  150  may define an opening  152 . Opening  152  may extend through an entire thickness of second portion  150  in a direction parallel to longitudinal axis of agent inlet  118  (but not through an entire width of second portion  150 ). Second portion  150  may have a third seal  154 , fourth seal  156 , and fifth seal  158  received thereupon. Third seal  154  may be on a first side of opening  152 , more proximate to first portion  140 . Fourth seal  156  may be on a second, opposite side of opening  152 . Fifth seal  158  also may be on the second side of opening  152 . First portion  140  may be closer to fourth seal  156  than to fifth seal  158 . 
     A first spring  162  may extend between and connect first portion  140  and second portion  150 . First spring  162  may be fixedly connected to an end  164  of first portion  140  and to an end  166  of second portion  150 . First portion  140  may taper to first end  164 , which may have a smaller cross-sectional diameter than other portions of first portion  140 . Second portion  150  may taper to first end  166 , which may have a smaller cross-sectional diameter than other portions of second portion  150 . First end  166  may be an end of second portion  150  that is closest to third seal  154 . A second spring  168  may extend from a second end  170  of second portion  150 . Second end  170  may be an end of second portion  150  that is closest to fifth seal  158 . First spring  162  may have a smaller spring constant than second spring  168  (i.e., first spring  162  may be a weaker spring than second spring  168 ). An equivalent force on first spring  162  and second spring  168  may cause first spring  162  to compress more than second spring  168 . 
     Valve  138  may be received within a cavity  200  of body  112 . Cavity  200  may be defined by surface(s)  202 . First cavity  200  may have a first opening  204 , which is at one end of cavity  200 . Cavity  200  may have a second opening  206 , which is in fluid communication with fluid inlet  120  and source  24 . A third opening  208  of cavity  200  may be in fluid communication with a fluid nozzle chamber  210 . A fourth opening  212  of cavity  200  may be in fluid communication with a mixing chamber  214 , which may have any of the features of mixing chamber  30 . Fourth opening  212  may be aligned or approximately aligned with agent inlet  118  so as to be in selective fluid communication with agent inlet  118 . Second spring  168  may contact surface  202  at an end  205  of cavity  200  that is opposite from the end of cavity  200  having first opening  204 . 
     Seals  142 ,  144 ,  154 ,  156 ,  158  may have dimensions and measurements on a durometer such that they form seals with surface(s)  202  of cavity  200 . Seals  142 ,  144 ,  154 ,  156 ,  158  may also permit sliding movement of valve  138  within cavity  200 . 
       FIG. 2A  shows body  112  in a first configuration, in which agent  16  is not permitted to flow into cavity  200  via agent inlet  118 , and fluid is not permitted to flow into cavity  200  via fluid inlet  120 . Fourth seal  156  and fifth seal  158  may be positioned on either side of agent inlet  118  so that agent  16  may not pass between seals  156 ,  158  and surface(s)  202 , thus preventing flow of agent  16 . First seal  142  and second seal  144  may be positioned on either side of fluid inlet  120 . Seals  142 ,  144 , may prevent movement of fluid from fluid inlet  120  between seals  142 ,  144  and surface(s)  202 . In the first configuration, springs  162 ,  164  may be in relaxed, uncompressed states. 
       FIG. 2B  shows body  112  in a second configuration, in which fluid is permitted to flow into cavity  200  via fluid inlet  120 . In operation, when actuation mechanism  30  is activated, first portion  140  of valve  138  may translate within cavity  200 , in a first direction toward end  205  of cavity  200 . Actuation mechanism  30  may be a separate component, or a surface of valve  138  may serve as an actuation mechanism and may receive a force from a user&#39;s hand. First portion  140  may exert a force first against spring  162 , causing first spring  162  to compress. Because first spring  162  is weaker than second spring  168  and/or because second portion  150  may not move until first spring  162  is compressed a selected amount, second portion  150  may not immediately move along with first portion  140 . 
     As shown in  FIG. 2B , in the second configuration, an entirety of second seal  144  may not be in contact with surface(s)  202 . For example, second seal  144  may be aligned with a portion of third opening  208 . Thus, fluid from fluid inlet  120  may pass between first portion  140  and surface(s)  202  (e.g., along neck portion  148 ). The fluid may then pass through third opening  208  into fluid nozzle chamber  210 . The fluid may then pass through a fluid nozzle opening  220 , into mixing chamber  214 . The fluid may then exit through outlet  134 . 
     In the second configuration of  FIG. 2B , second portion  150  may remain in the same position or in approximately the same position as in the first configuration ( FIG. 2A ). Therefore, for the reasons discussed above, agent  16  may not be permitted to flow into cavity  200  via agent inlet  118 . As a result, only the fluid from source  24  may exit outlet  134 . 
     As actuation mechanism  30  continues to be activated, second portion  150  may begin to move in the first direction (to the left in the Figures), after first spring  162  has been sufficiently compressed, when the force is sufficient to compress second spring  168 . Valve  138  may be thusly transitioned from the second configuration ( FIG. 2B ) to a third configuration of  FIG. 2C . In the third configuration, third seal  154  and fourth seal  156  may be disposed on opposite sides of agent inlet  118 , and opening  152  of second portion  150  may be aligned with agent inlet  118  so as to be in fluid communication with agent inlet  118 . Therefore, agent  16  may be permitted to pass into opening  152 , via agent inlet  118 . Agent may be unable to pass between third and fourth seals  154 ,  156  and surface(s)  202 , maintaining agent  16  in a desired location so that it will pass through opening  152 . 
     Meanwhile, first portion  140  may remain in the same position or in approximately the same position as in the second configuration ( FIG. 2B ). Therefore, fluid from source  24  may continue to flow as described above, with respect to  FIG. 2B . Second spring  168  and/or actuation mechanism  30  may be configured so that, after second spring  168  is compressed by a specified amount, neither of first portion  140  or second portion  150  may move further in the first direction, to maintain the third configuration of  FIG. 2C . In the third configuration, second spring  168  may be fully compressed or may be only partially compressed. 
     After agent  16  passes through opening  152 , agent  16  may pass through fourth opening  212 , into mixing chamber  214 . There, agent  16  may combine with fluid from source  24 . The combined agent  16  and fluid from fluid source  24  may then pass through outlet  134 , to be delivered to a desired location. 
     After actuation mechanism  30  is no longer activated, a restoring force of second spring  168  may return valve  138  to the second configuration, in which fluid from source  24  is delivered, but agent  16  is not delivered. Then, a restoring force of first spring  162  may return valve  138  to the first configuration, in which neither of fluid from source  24  nor agent  16  is delivered. 
     It will be appreciated, although the above description describes the second configuration ( FIG. 2B ) as resulting from compression of first spring  162  without compression of second spring  168 , that both first and second springs  162 ,  164  may be compressed in the second configuration so as to align seals  142 ,  144 ,  154 ,  156 ,  158  as described above to allow delivery of only fluid from source  24 . Furthermore, in transitioning from the second configuration ( FIG. 2B ) to the third configuration ( FIG. 2C ), first spring  162  may experience further compression (first spring  162  may not be fully compressed in the second configuration). 
     Furthermore, it will be appreciated that there are numerous configurations of valve  138  in between the first and second configurations and in between the second and third configurations, For example, configurations may exist in which a portion of agent inlet  118  is covered and a portion of agent inlet  118  is aligned with opening  152  so that opening  152  is in fluid communication with agent inlet  118 . In such a configuration, a relatively smaller amount of agent  16  may be permitted to pass through opening  152 , compared with the third configuration ( FIG. 2B ). As valve  138  transitions between the second configuration ( FIG. 2B ) and the third configuration ( FIG. 3B ), an increasing amount of agent inlet  118  may align with opening  152 , allowing an increasing amount of agent  16  to pass into opening  152 . 
     Body  112  may facilitate delivery of fluid from source  24  that is free from or substantially free from agent  16  through outlet  134  before delivery of agent  16  and after delivery of agent  16 . This delivery of fluid from source  24  that is free from or substantially free from agent  16  may flush system  10 , reducing or eliminating clogging. 
       FIGS. 3A and 3B  show an exemplary metering mechanism  250 , which may be used as a portion of delivery system  10 .  FIGS. 3A and 3B  both show views with enclosure  14  removed, looking in a direction toward agent inlet  18  and body  12  (i.e. enclosure  14  would be coming out of the top of the page of  FIGS. 3A and 3B ). 
     As shown in  FIGS. 3A and 3B , metering mechanism  250  may include a door  252 , which may pivot about a fixed pivot point A, and which may be a knife-edge door that has a very thin thickness in a direction parallel to a longitudinal axis of agent inlet  18 . As shown in  FIGS. 3A and 3B , door  252  may have a shape that includes any combination of straight and rounded sides. For example, door  252  may have three straight sides and one rounded side. Pivot point A may be located between one of the straight sides and the rounded side. 
     Metering mechanism  250  may also include a piston  254 . Piston  254  may be disposed partially within a chamber  256 , and a stem  258  of piston  254  may extend through an opening  260  in a wall of chamber  256 . A spring  262  may also be disposed within chamber  256 . Stem  258  of piston  254  may extend along a central axis of spring  258 . 
     Chamber  256  may be fluidly connected to a source of fluid, such as source  24 . When the fluid  24  enters chamber  256 , chamber  256  may be pressurized, and the fluid may exert a force on a head  264  of piston  254 , in a first direction toward opening  260 . The force from the fluid may cause piston  254  to move in the first direction. A seal (not shown) may be disposed between chamber  256  and one or both of stem  258  and head  264 , so that the fluid may not exit chamber  256 . As piston  254  moves in the first direction (to the left in  FIG. 3A ), piston  254  may compress spring  262 , generating a restorative force in a second direction, opposite the first direction. A movement of piston  254  in the first direction may stop when any of the following occurs (1) head  264  presses against surfaces of chamber  256 ; (2) a restorative force of spring  262  is equal to a force of the fluid on piston  254 ; and/or (c) spring  262  is fully compressed. 
     In a first configuration of metering mechanism  250 , shown in  FIG. 3A , spring  262  may be in a relaxed state (such as when no fluid is supplied to chamber  256 ). Door  252  may be in a first position.  FIG. 3B  shows a second configuration of metering mechanism  250 , in which spring  262  is compressed, and piston  254  has moved in the first direction (due to fluid supplied to chamber  256 ). Door  252  may be in a second position. 
     When a user activates actuation mechanism  30 , fluid (e.g., from source  24 ) may flow into chamber  256 . Piston  254  and door  252  may be configured such that, when fluid is supplied to chamber  256 , as piston  254  moves in the first direction, piston  254  exerts a force on door  252  in the first direction. The force of piston  254  may cause door  252  to rotate about pivot point A. As door  252  rotates, it may expose an opening  266 , which may be in fluid communication with a chamber (not shown) of body  12 . At first, after piston  254  begins moving in the first direction, only a portion of opening  266  may be exposed due to rotation of door  252 . As piston  254  continues to move in the first direction, door  252  may continue to rotate, and more of opening  266  may be exposed. When piston  254  is fully extended ( FIG. 3B ), an entirety of opening  266  may be exposed. In the first position of door  252  ( FIG. 3A ), door  252  covers opening  266 , so that opening  266  does not communicate with enclosure  14 , and no agent  16  can pass into opening  266 . 
     When actuation mechanism  30  is no longer activated, pressure may be released from chamber  256  (via, e.g., a release valve, which is not shown). Spring  262  may urge head  264  of piston  254  in the second direction, away from the opening  260 , due to the restoring force of spring  262 . Thus, piston  254  may no longer exert a force on door  252 . The restoring force of spring  262  may cause piston  254  to return to the first configuration ( FIG. 3A ). Door  252  may also be biased to return to the first configuration ( FIG. 3A ). For example, door  252  may be spring biased at, e.g., at pivot point A. 
     In use, when actuation mechanism  30  is activated, such activation may cause fluid to pass through fluid inlet  20  and out of outlet  34 . Meanwhile, as described above, actuation mechanism  30  may begin to expose opening  266 . A portion of opening  266  may not immediately be exposed due to a delay in pressurizing chamber  256 , or a delay in exposing opening  266  once chamber  256  is pressurized. Additionally or alternatively, a size of a portion of opening  266  that is exposed may initially be sized such that agent  16  does not flow through opening  260 , or only a small amount of agent flows through opening  260 . Thus, initially after actuation mechanism is activated, only fluid from source  24  may initially flow from outlet  34 , without any agent  16 . 
     Similarly, fluid may continue to be delivered via outlet  34 , after actuation mechanism  30  begins or finishes transitioning from the second configuration ( FIG. 3B ) to the first configuration ( FIG. 3A ). For example, actuation mechanism  30  may be configured so that chamber  256  is depressurized before fluid stops passing through fluid inlet  20 . Opening  266  may be covered partially or entirely by door  252 , while fluid continues to pass through fluid inlet  20 . 
     Metering mechanism  250  may facilitate delivery of fluid from source  24  that is free from or substantially free from agent  16  through outlet  34  before delivery of agent  16  and after delivery of agent  16 . This delivery of fluid from source  24  that is free from or substantially free from agent  16  may flush system  10 , reducing or eliminating clogging. 
       FIGS. 4A-4B  show cross-sectional views of an exemplary body  312  for use with delivery system  10 . Body  312  may include an agent inlet  318 , which may be in fluid communication with enclosure  14  storing an agent  16 . Body  312  also may include a fluid inlet  320  for receiving fluid from source  24  (see  FIG. 1B ). Body  312  may also include a metering mechanism  330  for controlling flow of fluid through fluid inlet  320  and agent  16  through agent inlet  318 . Metering mechanism  330  may have any of the features of metering mechanism  250 . 
     Metering mechanism  330  may include a door  332 , which may have any of the properties of door  252 . Door  332  may be configured to rotate about a hinge B. Door  332  may also be operatively connected to a wire  333 . For example, a portion of door  332  that is on an opposite side of door  332  from hinge B may be operatively connected to wire  333 . A first end  336  of wire  333  may be attached to a ridge  338  extending from an edge of door  332  in a direction parallel to a longitudinal axis of agent inlet  318 . 
     A second end  340  of wire  333  may be operatively connected to a valve  350 . Valve  350  may be operatively connected to an actuation mechanism  30  or may include a surface which serves as an actuation mechanism  30  by receiving contact from a finger of a user. Valve  350  may be received within a fluid channel  352 , which may be in fluid connection with fluid inlet  320  and a fluid nozzle chamber  322 . A longitudinal axis of valve  350  may be approximately perpendicular to a longitudinal axis of fluid channel  352 . Valve  350  may also be received within a valve channel  354 , which may have a longitudinal axis that is approximately parallel to a longitudinal axis of valve  350 . Valve  350  may include first, second and third seals  356 ,  358 ,  360 , which may be, for example, O-ring seals. Seals  356 ,  358 ,  360  may prevent air from entering valve channel  354  from fluid channel  352 . Valve  350  may be dimensioned and formed of a material such that, in the configuration of  FIG. 4A , valve  350  blocks fluid channel  352 , such that fluid from fluid inlet  320  may not pass valve  350  to enter fluid nozzle chamber  322 . For example, valve channel  354  may have a larger cross-sectional area than a cross-sectional area of fluid channel  352 , and valve  350  may occupy an entirety or approximately an entirety of valve  354 . 
     Door  332  may be biased such that, when no force is exerted on door  332  from wire  333  and door  332  is in a relaxed configuration, door  332  is approximately perpendicular or otherwise transverse to a central longitudinal axis of agent inlet  318 , such that agent  16  may not pass door  332  to pass through fluid inlet  320 . For example, door  332  may be spring-biased at pivot point B.  FIG. 4A  shows a first configuration of body  312 , in which door  332  is in a relaxed configuration, effectively closing agent inlet  318  so that agent inlet  318  is not in communication with a mixing chamber  372 . 
     Valve  350  may be movable in first and second directions, perpendicular to a longitudinal axis of fluid channel  352  and parallel to a longitudinal axis of valve channel  354 . As valve  350  moves in the first direction, narrowed portions  351  of valve  350  may move such that they are disposed within fluid channel  352 , and fluid may move past valve  350 . The narrowed portions may have a cross-sectional area that is smaller than that of fluid channel  352 , so that fluid may pass valve  350 . Therefore, movement of valve  350  in the first direction may activate flow of fluid from fluid inlet  320  into fluid nozzle chamber  322 . 
     Movement of valve  350  in the first direction may compress a spring  362 . When spring  362  is in a neutral, relaxed configuration, door  332  may also in its relaxed configuration (the configuration to which door  332  is biased), so that agent  16  may not flow past door  332  into agent inlet  318 . 
     As valve  350  moves in the first direction, valve  350  may move second end  340  of wire  333  in the first direction (to the right in  FIGS. 4A-4B ). As a result, first end  336  of wire  333  may move in the first direction. Alternatively, first end  336  of wire  333  may move in another direction such that a force from first end  336  of wire  333  causes door  332  to pivot about hinge B. Wire  333  may be routed over a pulley  364 , to accommodate space for other components of body  312  and/or delivery system  10 . 
     When first end  336  of wire  333  moves in the first direction, it may exert a force on ridge  338  in the first direction, which may cause door  332  to pivot such that an angle between door  332  and fluid inlet  320  increases (gets closer to 180 degrees) as door  332  pivots. As door  332  pivots, agent  16  may begin to flow past agent inlet  318  and door  332 . Valve  350  and/or door  332  may stop moving when any one or more of the following occurs: door  332  contacts a surface defining agent inlet  318  or other structure of body  312 , spring  362  reaches a maximum compression against a surface of valve channel  354 , or a surface of valve  350  reaches a stop (not shown).  FIG. 4B  shows body  312  in a second configuration, in which door  332  is fully open. 
     Upon initial activation of actuation mechanism  30 , door  332  may gradually pull away from agent inlet  318 , yet fluid may flow through a fluid nozzle chamber  322 , into a mixing chamber  372 , and out of outlet  334 , before any agent  16  or an appreciable amount of agent  16  is able to enter mixing chamber  372 . Opening of door  332  may occur after valve  350  permits flow of fluid from fluid inlet  320 . Once door  332  is opened a sufficient amount upon further activation of actuation mechanism  30 , agent  16  may enter mixing chamber  372  to be mixed with fluid and to be delivered out of outlet  334 . After actuation mechanism  30  is deactivated, door  332  may begin to return to its unbiased position. Closing of agent inlet  318  may allow a flow of fluid out of outlet  334  without any or an appreciable amount of agent  16  entering a mixing chamber  372 . A flow of fluid without agent  16 , or appreciable amounts of agent  16 , before and after a flow of fluid combined with agent  16  may lessen clogging of portions of system  10 . 
     Alternatively, other portions of body  312  may facilitate a flow of fluid without agent  16  before and after a flow of fluid combined with agent  16 . For example, properties of spring  362  and/or slack in wire  333  may delay opening of door  332 , and/or actuation mechanism  30  may be configured to permit a flow of fluid before movement of valve  350  in the first direction commences and after valve  350  returns to its unbiased configuration following delivery of agent  16  ( FIG. 3A ). Body  312  may facilitate delivery of fluid from source  24  that is free from or substantially free from agent  16  through outlet  334  before delivery of agent  16  and after delivery of agent  16 . This delivery of fluid from source  24  that is free from or substantially free from agent  16  may flush system  10 , reducing or eliminating clogging. 
       FIGS. 5A-5B  show cross-sectional views of an exemplary body  412 , which may be a portion of delivery system  10 . Body  412  may include a metering mechanism  430 . Metering mechanism  430  may include a slider  432  (a first rigid member), which may be made from any suitable material (e.g., plastic, metal, composites, polymers, etc.) Slider  432  may be made of rigid or substantially rigid material. Slider  432  may include an opening  436  formed therein. Slider  432  may be configured to translate or slide in first and second directions relative to a remainder of body  412 . A longitudinal axis of slider  432  may be transverse (e.g., perpendicular) to a longitudinal axis of an agent inlet  418 , and movement of slider  432  may be axial along the longitudinal axis of slider  432 . 
     Slider  432  may be pivotably coupled to an arm  438  (a second rigid member) via, e.g., a hinge  437 . Slider  432  may be received within a channel (not shown) or otherwise constrained so that slider  432  may only translate along the first and second directions (i.e., axial movement). Hinge  437  may be similarly translatable within that channel. Arm  438  may be rotatable about an axis C, extending into and out of the page as shown in  FIGS. 5A and 5B . Axis C is also shown in  FIG. 5C  relative to arm  438 . Arm  438  may include a trigger  440  at one end of arm  438 . Trigger  440  may be contacted by a user in order to rotate arm  438  about axis C and thereby translate slider  432 . Arm  438  may have an approximately rectangular shape, as shown in  FIG. 5C . An opening  439  in arm  438  may receive components of body  412  (e.g., a fluid nozzle chamber  462 ). A top bar  438   a  of arm  438  may connect to slider  432  at hinge  437 . 
     As trigger  440  is depressed, trigger  440  may compress a spring  450 . Spring  450  may be operatively coupled to a button valve  460 . Button valve  460  may be operative to allow and disallow flow from source  24  through a fluid inlet  420 . 
     A first configuration of metering mechanism  430  is shown in  FIG. 5A . In the configuration of  FIG. 5A , spring  450  may be in a relaxed, uncompressed state that biases trigger  440  to the configuration of  FIG. 5A . Opening  436  of slider  432  may be offset from agent inlet  418 , such that agent  16  may not pass through opening  436  and agent inlet  418 . 
     In use, an operator may depress trigger  440 , which may be an example of actuation mechanism  30 . A greater force may be required to compress spring  450  than to open button valve  460  to allow force of fluid from source  24  through fluid inlet  420 . For example, a compression of trigger  440  required to depress a button  461  of button valve  460  and open button valve  460  may be approximately 0.075 inches. Additionally or alternatively, spring  450  may partially compress to open button valve  460 , and further compression of spring  450  may be required in order to translate opening  436  sufficiently that it is in communication with agent inlet  418 . A further compression of trigger  440  required to compress spring  450  may be approximately 0.33 inches. Thus, a total throw of trigger  404  may be approximately 0.504 inches. A force depressing trigger  440  may initially translate spring  450  to open button valve  460  and to activate flow of fluid from source  24  through fluid inlet  420 . Fluid may flow into fluid inlet  420 , into a fluid nozzle chamber  462 . Fluid may pass through an opening  462  of fluid nozzle chamber  462 , into mixing chamber  464 . Fluid may then exit via outlet  34 . In the first configuration, agent  16  may not be delivered via outlet  434 , since opening  436  is not aligned with agent inlet  418 . 
     Thereafter, as force on trigger  440  is increased, spring  450  may be compressed (or may be further compressed). Compression of spring  450  will enable arm  438  to rotate about axis C (or further about axis C). Rotation of arm  438  may, in turn, cause slider  432  to translate in the first direction (to the left in the Figures), aligning opening  436  with agent inlet  418 , transitioning metering mechanism  430  to the second configuration of  FIG. 5B . In the second configuration, fluid from source  24  may continue to flow as described above, with respect to the first configuration ( FIG. 5A ). Because opening  436  is aligned with agent inlet  418  and in fluid communication with agent inlet  418 , agent  16  may also pass through opening  436  and agent inlet  418 . Agent  16  may then enter mixing chamber  464 , where it may mix with fluid from source  24 . The combined agent  16  and fluid may then be delivered via outlet  434 . 
     Trigger  440  may include an opening  470 , which may be, for example, an elliptical shape. Opening  470  may receive components (not shown) that couple trigger  440  to spring  450 , while allowing for necessary movement of trigger  440  relative to stationary spring  450  and button valve  460 . 
     When a user releases trigger  440 , spring  450  may first decompress, causing slider  432  to return to a configuration that misaligns opening  436  and agent inlet  418 . Because opening  436  may be offset from agent inlet  418 , agent  16  may not pass through agent inlet  418 . However, because button valve  460  may remain open, fluid may continue to flow from source  24  through fluid inlet  20  for a time, until button valve  460  then closes. 
     Body  412  may facilitate delivery of fluid from source  24  that is free from or substantially free from agent  16  through outlet  434  before delivery of agent  16  and after delivery of agent  16 . This delivery of fluid from source  24  that is free from or substantially free from agent  16  may flush system  10 , reducing or eliminating clogging. 
       FIGS. 6A-6B  show another example body  512 , which may be a component of system  10 . Body  512  may have any of the features of body  112  of  FIGS. 2A-2C . The discussion of  FIGS. 6A and 6B , herein, highlights differences between body  112  and body  512 . A fluid inlet  520  of body  512  may be in direct fluid communication with a fluid nozzle chamber  610 , without requiring fluid to first pass through a cavity  600 . A valve  538  may include only one stem portion  550 , which may have any of the properties of second portion  150 . Stem portion  550  may include an opening  552  (like opening  152 ) and may be sealingly slidable within cavity  600 . 
     Flow to fluid inlet  520  may be controlled via a valve  522 , which may be, for example, a button valve. Valve  522  may actuate independently of valve  538 . Thus, valve  522  may be opened, allowing a flow of fluid to enter fluid inlet  520  and exit outlet  534 . Meanwhile, valve  538  may separately be actuated to permit flow of agent  16  through agent inlet  518 . 
       FIG. 6A  shows a first configuration, in which valve  522  is closed and valve  538  is in a first configuration, in which opening  552  is not aligned (not in fluid communication) with an agent inlet  518 . In the first configuration, fluid may not pass through fluid inlet  20 , and agent may not pass through agent inlet  518 , so that neither fluid nor agent is delivered via outlet  534 . 
       FIG. 6B  shows a second configuration, in which valve  522  is open and valve  538  is in a second configuration, in which opening  552  is aligned with agent inlet  518  so as to be in fluid communication with agent inlet  518 . In the second configuration, fluid may pass through fluid inlet  520 , and agent  16  may pass through agent inlet  518 , so that fluid and agent  16  may combine in mixing chamber  514  and be delivered from outlet  534 . 
     Body  512  may be configured so that valve  538  may be actuated to the second configuration only when valve  522  is open. Thus, agent  16  may not enter mixing chamber  514  if fluid from source  24  is not also delivered to mixing chamber  514 . In operation, a user may actuate a first actuation mechanism  530  (which may be, for example, a button of valve  522 ). Fluid may flow through body  512  and out of outlet  534 . A user may then actuate a second actuation mechanism (not shown) to transition valve  538  to the second configuration to deliver a combination of agent  16  and fluid. A user may not be able to release first actuation mechanism  530  without first releasing the second actuation mechanism. After the second actuation mechanism is released, valve  538  may transition back to the first configuration of valve  538  due to a restorative force of a spring  568 , which may have any of the properties of second spring  168 . A user may then release first actuation mechanism  530  to close valve  522  and stop flow of fluid through fluid inlet  520 . 
     Body  512  may facilitate delivery of fluid from source  24  that is free from or substantially free from agent  16  through outlet  534  before delivery of agent  16  and after delivery of agent  16 . This delivery of fluid from source  24  that is free from or substantially free from agent  16  may flush system  10 , reducing or eliminating clogging. 
       FIGS. 7A-7D  show aspects of a body  712  that may form a part of delivery system  10 .  FIGS. 7A-7B  show cross-sectional views of body  712  in first and second configurations, respectively, and  FIGS. 7C-7D  show aspects of a turbine  750  that may be a component of body  712 . 
     As shown in  FIGS. 7A and 7B , a body  712  may have an agent inlet  718 , a fluid inlet  720 , and an outlet  734 , in fluid connection with one another via a chamber  752 . 
     Turbine  750  may be disposed in chamber  752 . Turbine  750  may include a plurality of blades  754  extending radially outward from a central body  756  (see  FIGS. 7C-7D ). Although three blades  754  are shown, it will be appreciated that other numbers of blades  754  may be utilized. Blades  754  may have any suitable shape, including the shape shown. Blades  754  may be formed from any suitable material, including rigid or flexible material, such as metals or plastics. Turbine  750  may also have a stop mechanism  758 , which may extend radially outward from central body  756 . Stop mechanism  758  may have any suitable shape, including a wedge shape, which may be a curved wedge shape. Stop mechanism  758  may be made from any suitable material, including rigid materials. 
     Turbine  750  may be fixedly connected to an axle  760  and may be rotatable about axle  760 . Axle  760  may extend from central body  756  and may also be fixedly connected to a round gear  762 , which may include teeth. Via axle  760 , turbine  750  and gear  762  may rotate together, in unison. Gear  762  may be formed of any suitable material and may include any suitable number of teeth. Turbine  750  and gear  762  may have any suitable size. 
     Gear  762  may interact with a linear rack  764 . Linear rack  764  may be movable relative to gear  762 , along a direction transverse to a longitudinal axis of agent inlet  718  (e.g., perpendicular to agent inlet  718 , left/right in the Figures). Rack  764  may include an opening  764   a  formed therein. A spring  770  may extend from an end of rack  764  furthest from gear  762 , and a first end of spring  770  may be fixed relative to rack  764 . A second end of spring  770  may be fixed relative to a surface  772  defining chamber  752 . 
     In a first configuration, shown in  FIG. 7A , actuation mechanism  30  ( FIG. 1 ) may not be activated, and fluid may not flow from source  24  to fluid inlet  720 . Turbine  750 , gear  762 , and rack  764  may each be stationary. Spring  770  may be in a relaxed state. Rack  764  may be positioned so that opening  764   a  is not aligned with (not in fluid communication with) agent inlet  718 . Rack  764  may include seals  765  to prevent agent from moving between an outer surface of rack  764  and a surface of chamber  752 . In the first configuration, agent  16  may not enter chamber  752  because opening  764   a  is not aligned with (not in fluid communication with) agent inlet  718 . 
     When an actuation mechanism ( FIG. 1 ) is activated, flow from source  24  to fluid inlet  720  may be permitted. Fluid from fluid inlet  720  may interact with blades  754  to cause turbine  750  to rotate. Rotation of turbine  750  may cause corresponding rotation of gear  762 . Rotation of gear  762  may cause rack  764  to translate in a first direction (to the left in the Figures), such that opening  764   a  moves closer to agent inlet  718 . Spring  770  may be compressed as rack  764  translates, because a force from fluid on turbine  750  may overcome a restorative force of spring  770 . As shown in  FIG. 7B , in a second configuration of body  712 , opening  764   a  may be aligned with (in fluid communication with) agent inlet  718 . Thus, agent  16  may be permitted to flow through opening  764   a  and into chamber  752 . In chamber  752 , agent  16  may mix with the fluid from source  24  and then exit through outlet  734 . However, before opening  764   a  is aligned with (in fluid communication with) agent inlet  718 , only fluid from source  24  may flow through chamber  752  and exit outlet  734 . 
     Activation of actuation mechanism  30  may cause, either immediately or following a delay, a tab  780  to extend from a surface  772  of body  712 . Tab  780  may extend in a direction perpendicular to axle  760 .  FIG. 7C  shows turbine  750  and tab  780  prior to extension of tab  780  (e.g., prior to activation of actuation mechanism  30 ).  FIG. 7D  shows turbine  750  and tab  780  after tab  780  has been extended from surface  772 . Tab  780  may interact with stop mechanism  758  to prevent further rotation of turbine  750  after stop mechanism  758  contacts tab  780 . Tab  780  and stop mechanism  758  may stop gear  762  from continuing to rotate and thereby stop rack  764  from translating past a desired position, where opening  764   a  aligns with agent inlet  718 . 
     When actuation mechanism  30  is released, a flow of fluid through fluid inlet  720  may be eliminated or reduced, thereby eliminating or reducing a force on blades  754 . A restorative force of spring  770  may overcome a force of fluid (if any) on turbine  750 , causing rack  764  to translate in a second direction, opposite the first direction. Rack  764  may, in turn, cause rotation of gear  762 , which may cause rotation of turbine  750 , in a direction opposite to a direction of rotation while translating from the first configuration to the second configuration. Tab  780  may also retract. Opening  764   a  may no longer be aligned with (in fluid communication with) agent inlet  718 , so agent  16  may no longer flow through agent inlet  718 . Where some flow of fluid through fluid inlet  720  continues, fluid may continue to exit outlet  734 , after a flow of agent  16  has ceased. Alternatively, body  712  may include a purge line, which requires actuation by another mechanism (e.g., a button). Alternatively, actuation mechanism  30  may have three positions. In a first position of actuation mechanism  30 , no flow of fluid through fluid inlet  720  may occur. In a second position, fluid may be permitted to flow, but tab  780  or another component may interact with rack  764  to stop movement of rack  764  before opening  764   a  aligns with agent inlet  718 , thereby preventing flow of agent  16 . In a second position, tab  780  or another component may be retracted/deactivated to permit rotation of turbine  750  and permit flow of agent  16  while fluid flows through fluid inlet  720 . Alternatively, gear ratios between gear  762  and linear rack  764 , a length of rack  764 , and a strength of spring  770  may be chosen such that, when actuation mechanism  30  is activated, a known duration and/or amount of fluid from fluid inlet  720  may flow prior to alignment of opening  764   a  and agent inlet  718 , providing a flow of fluid without agent  16 . Following alignment of opening  764   a  and agent inlet  718 , agent  16  may flow via agent inlet  718 . If a user desires flow of fluid following a delivery of agent  16 , the user may release actuation mechanism  30  and reactivate actuation mechanism  30 . The user may only activate actuation mechanism for an amount of time such that fluid flows but agent does not flow (because opening  764   a  and agent inlet  718  do not align). 
     Body  712  may facilitate delivery of fluid from source  24  through outlet  734  before delivery of agent  16  and after delivery of agent  16 . This delivery of fluid from source  24  may flush system  10 , reducing or eliminating clogging. 
     While principles of the disclosure are described herein with reference to illustrative examples for particular applications, it should be understood that the disclosure is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and substitution of equivalents all fall within the scope of the examples described herein. Accordingly, the invention is not to be considered as limited by the foregoing description.