Patent Publication Number: US-2021162124-A1

Title: Priming method for infusion set, and infusion set

Description:
TECHNICAL FIELD 
     The present invention relates to a method for priming an infusion set that is to be used to administer a liquid such as a medical solution via a patient&#39;s vein. Also, the present invention relates to this infusion set. 
     BACKGROUND ART 
     In the medical field, infusion to administer medicines, nutrients, electrolytes, or the like via a patient&#39;s vein is widely performed. For example, in the case of administering an anti-cancer agent, it is necessary to sequentially administer, to a patient, not only a medical solution that contains the anti-cancer agent but also a plurality of liquids, such as a premedication and a physiological saline for washing out flow paths. The plurality of liquids are stored separately in a plurality of respective infusion bags. An infusion set that includes a main line and at least one sub-injection line is used to bring a plurality of infusion bags into communication with a needle that has been inserted into a patient&#39;s vein. 
     Before infusion is started, an operation, which is called priming, to replace air that is within a flow path in the infusion set with a priming solution needs to be performed. Patent Document 1 describes a priming method in which a priming solution (physiological saline) in an infusion bag is introduced into an entire infusion set that includes a main line and a side-injection line, with the infusion bag in which the priming solution is stored connected to the main line, and with an infusion set not connected to the side-injection line. 
     PRIOR ART DOCUMENTS 
     Patent Document 
     [Patent Document 1] JP 5774802B 
     [Patent Document 2] WO 2013/154050 
     [Patent Document 3] JP 2014-079355A 
     [Patent Document 4] JP 2013-252165A 
     [Patent Document 5] WO 2016/133139 
     DISCLOSURE OF INVENTION 
     Problem to be Solved by the Invention 
     In the above priming method, the same priming solution is introduced into both the main line and the side-injection line. It is desired, in some cases, that the lines are primed using liquids stored in infusion bags that are connected to the respective lines. 
     Meanwhile, when priming is performed using a medical solution (hazardous medical solution) that contains a hazardous medicine such as an anti-cancer agent, leakage of this hazardous medical solution or air that has come into contact therewith to the outside needs to be avoided since it may expose an operator to the medicine. 
     An object of the present invention is to enable an operator to prime an infusion set that includes a main line and a side-injection line without being exposed to a medicine. 
     Means for Solving Problem 
     A first infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; and a second open/close valve provided on the second flow path. 
     A first priming method of the present invention for priming the first infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; 
     and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the first container. 
     A second infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a collection flow path with one end connected to the section of the first flow path, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A second priming method of the present invention for priming the second infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the collection container. 
     A third infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a collection flow path with one end in communication with a gas storing portion in the drip chamber, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A third priming method of the present invention for priming the third infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the collection container through the gas storing portion in the drip chamber and the collection flow path. 
     A fourth infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a bypass flow path with one end in communication with a gas storing portion in the drip chamber, and another end in communication with a portion of the first flow path on the first connector side of the first open/close valve, or with the first connector; a bypass flow path open/close valve provided on the bypass flow path; a collection flow path with one end connected to the section of the first flow path, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A fourth priming method of the present invention for priming the fourth infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. The second priming step includes: a first part of the second priming step of moving, using the second liquid, air that has been present in the second flow path toward the collection container through the collection flow path, and a second part of the second priming step of moving, using the second liquid, air that is present forward of the second liquid in a direction in which the second liquid flows, toward the first container through the gas storing portion in the drip chamber and the bypass flow path. 
     A fifth infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a bypass flow path with one end in communication with a gas storing portion in the drip chamber, and another end in communication with a portion of the first flow path on the first connector side of the first open/close valve, or with the first connector; a bypass flow path open/close valve provided on the bypass flow path; a collection flow path with one end connected to a portion of the bypass flow path between the drip chamber and the bypass flow path open/close valve, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A fifth priming method of the present invention for priming the fifth infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the collection container through the gas storing portion in the drip chamber, the bypass flow path, and the collection flow path, or toward the first container through the gas storing portion in the drip chamber and the bypass flow path. 
     Effects of the Invention 
     According to the present invention, the first priming step of priming the first flow path using the first liquid is performed, and thereafter, the second priming step of priming the second flow path using the second liquid is performed. The first and second flow paths can be primed using the first and second liquids that are stored in the first and second container that are connected to the first and second flow paths, respectively. 
     In the second priming step, the second liquid moves air that has been present in the second flow path toward a predetermined container. In the case where the second liquid is a hazardous medical solution, it is unlikely that the second liquid or air that has come into contact therewith leaks out to the outside. For this reason, an operator can perform priming without being exposed to the medical solution. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows an infusion set according to Embodiment 1 of the present invention. 
         FIG. 2  shows an infusion set according to Embodiment 2 of the present invention. 
         FIG. 3  shows an infusion set according to Embodiment 3 of the present invention. 
         FIG. 4  shows an infusion set according to Embodiment 4 of the present invention. 
         FIG. 5  shows an infusion set according to Embodiment 5 of the present invention. 
         FIG. 6  shows an infusion set according to Embodiment 6 of the present invention. 
         FIG. 7  is a cross-sectional perspective view showing an example of a self-closing connector that may be used in the infusion set of the present invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     A first infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; and a second open/close valve provided on the second flow path. 
     A first priming method of the present invention for priming the first infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the first container. 
     In the first priming step of the first priming method, the second open/close valve may be closed and the first open/close valve and the variable valve may be opened to cause the first liquid to flow from the first container toward the downstream connector. This is advantageous for priming the entire first flow path from the first connector to the downstream connector using the first liquid in a simply manner. 
     In the first priming method, after the first priming step, in a state where the first liquid is being caused to flow from the first container toward the downstream connector with the second open/close valve closed and with the first open/close valve and the variable valve opened, the variable valve may be closed and the second open/close valve may be opened to start the second priming step. Thus, drip injection of the first liquid can be readily switched to priming of the second flow path. 
     Preferably, the variable valve is closed when an interface between the first liquid and air that has flowed out, following the first liquid, from the first container reaches the section of the first flow path in a state where the first liquid is being caused to flow from the first container toward the downstream connector. This mode is advantageous for reducing the likelihood that air mixes between the first liquid and the second liquid in the case where the whole quantity of the first liquid in the first container is administered to a patient, and subsequently the second liquid is sequentially administered to the patient. 
     The first infusion set may further include: a third flow path having, at one end, a third connector, which is to be connected to a third container for storing a third liquid, another end of the third flow path being connected to the section of the first flow path; and a third open/close valve provided on the third flow path. The first priming method may further include a third priming step of causing the third liquid to flow from the third container into the third flow path and priming the third flow path using the third liquid. In the third priming step, the third liquid may move air that has been present in the third flow path toward the first container. Thus, the third flow path can be primed using the third liquid stored in the third container that is connected to the third flow path. In the case where the third liquid is a hazardous medical solution, it is unlikely that the third liquid or air that has come into contact therewith leaks out to the outside. For this reason, the operator can prime the third flow path using the third liquid without being exposed to the medicine. 
     In the third priming step of the first priming method, the third liquid may move, toward the first container, air that has flowed out of the second container following the second liquid. This mode reduces the likelihood that, in the case where the second liquid is a hazardous medical solution, air that has come into contact with the second liquid leaks out to the outside. 
     In the first priming method, after the second priming step, when an interface between the second liquid and air that has flowed out, following the second liquid, from the second container reaches the section of the first flow path in a state where the second liquid is being caused to flow from the second container toward the downstream connector with the first open/close valve and the third open/close valve closed and with the second open/close valve and the variable valve opened, the second open/close valve and the variable valve may be closed and the third open/close valve and the first open/close valve may opened to start the third priming step. This mode is advantageous for reducing the likelihood that air mixes between the second liquid and the third liquid in the case where the whole quantity of the second liquid in the second container is administered to the patient, and subsequently the third liquid is sequentially administered to the patient. 
     The first infusion set may further include: a bypass flow path with one end in communication with a gas storing portion in the drip chamber, and another end in communication with a portion of the first flow path on the first connector side of the first open/close valve, or with the first connector; and a bypass flow path open/close valve provided on the bypass flow path. In the second priming step, the second liquid may move air that has been present in the second flow path toward the first container through the gas storing portion in the drip chamber and the bypass flow path. According to this mode, the second liquid and air that has been present in the second flow path can be reliably separated from each other using the drip chamber. 
     In the first priming step of the first priming method, the second open/close valve and the bypass flow path open/close valve may be closed and the first open/close valve and the variable valve may be opened to cause the first liquid to flow from the first container toward the downstream connector. This is advantageous for priming the entire first flow path from the first connector to the downstream connector using the first liquid in a simply manner. 
     In the first priming method, after the first priming step, in a state where the first liquid is being caused to flow from the first container toward the downstream connector with the second open/close valve and the bypass flow path open/close valve closed and with the first open/close valve and the variable valve opened, the first open/close valve and the variable valve may be closed and the second open/close valve and the bypass flow path open/close valve may be opened to start the second priming step. Thus, drip injection of the first liquid can be readily switched to priming of the second flow path. 
     Preferably, the first open/close valve and the variable valve are closed when an interface between the first liquid and air that has flowed out, following the first liquid, from the first container reaches the section of the first flow path or when dripping of the first liquid in the drip chamber ends in a state where the first liquid is being caused to flow from the first container toward the downstream connector. This mode is advantageous for reducing the likelihood that air mixes between the first liquid and the second liquid in the case where the whole quantity of the first liquid in the first container is administered to a patient, and subsequently the second liquid is sequentially administered to the patient. 
     The first infusion set may further include: a third flow path having, at one end, a third connector, which is to be connected to a third container for storing a third liquid, another end of the third flow path being connected to the section of the first flow path; and a third open/close valve provided on the third flow path. The first priming method may further include a third priming step of causing the third liquid to flow from the third container into the third flow path and priming the third flow path using the third liquid. In the third priming step, the third liquid may move air that has been present in the third flow path toward the first container through the gas storing portion in the drip chamber and the bypass flow path. In the case where the third liquid is a hazardous medical solution, it is unlikely that the third liquid or air that has come into contact therewith leaks out to the outside. For this reason, the operator can prime the third flow path using the third liquid without being exposed to the medicine. 
     In the third priming step of the first priming method, the third liquid may move air that has flowed out of the second container following the second liquid, toward the first container through the gas storing portion in the drip chamber and the bypass flow path. This mode reduces the likelihood that, in the case where the second liquid is a hazardous medical solution, air that has come into contact with the second liquid leaks out to the outside. 
     After the second priming step, when an interface between the second liquid and air that has flowed out, following the second liquid, from the second container reaches the section of the first flow path, or when dripping of the second liquid in the drip chamber ends, in a state where the second liquid is being caused to flow from the second container toward the downstream connector with the first open/close valve, the third open/close valve, and the bypass flow path open/close valve closed and with the second open/close valve and the variable valve opened, the second open/close valve and the variable valve may be closed and the third open/close valve and the bypass flow path open/close valve may be opened to start the third priming step. This mode is advantageous for reducing the likelihood that air mixes between the second liquid and the third liquid in the case where the whole quantity of the second liquid in the second container is administered to a patient, and subsequently the third liquid is sequentially administered to the patient. 
     A second infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a collection flow path with one end connected to the section of the first flow path, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A second priming method of the present invention for priming the second infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the collection container. 
     In the first priming step of the second priming method, the second open/close valve and the collection flow path open/close valve may be closed and the first open/close valve and the variable valve may be opened to cause the first liquid to flow from the first container toward the downstream connector. This is advantageous for priming the entire first flow path from the first connector to the downstream connector using the first liquid in a simply manner. 
     In the second priming method, after the first priming step, in a state where the first liquid is being caused to flow from the first container toward the downstream connector with the second open/close valve and the collection flow path open/close valve closed and with the first open/close valve and the variable valve opened, the first open/close valve and the variable valve may be closed and the second open/close valve and the collection flow path open/close valve may be opened to start the second priming step. Thus, drip injection of the first liquid can be readily switched to priming of the second flow path. 
     Preferably, the first open/close valve and the variable valve are closed when an interface between the first liquid and air that has flowed out, following the first liquid, from the first container reaches the section of the first flow path in a state where the first liquid is being caused to flow from the first container toward the downstream connector. This mode is advantageous for reducing the likelihood that air mixes between the first liquid and the second liquid in the case where the whole quantity of the first liquid in the first container is administered to a patient, and subsequently the second liquid is sequentially administered to the patient. 
     The second infusion set may further include: a third flow path having, at one end, a third connector, which is to be connected to a third container for storing a third liquid, another end of the third flow path being connected to the section of the first flow path; and a third open/close valve provided on the third flow path. The second priming method may further include a third priming step of causing the third liquid to flow from the third container into the third flow path and priming the third flow path using the third liquid. In the third priming step, the third liquid may move air that has been present in the third flow path toward the collection container through the collection flow path. Thus, the third flow path can be primed using the third liquid stored in the third container that is connected to the third flow path. In the case where the third liquid is a hazardous medical solution, it is unlikely that the third liquid or air that has come into contact therewith leaks out to the outside. For this reason, the operator can prime the third flow path using the third liquid without being exposed to the medicine. 
     In the third priming step of the second priming method, the third liquid may move air that has flowed out of the second container following the second liquid, toward the collection container through the collection flow path. This mode reduces the likelihood that air that has come into contact with the second liquid leaks out to the outside in the case where the second liquid is a hazardous medical solution. 
     In the second priming method, after the second priming step, when an interface between the second liquid and air that has flowed out, following the second liquid, from the second container reaches the section of the first flow path in a state where the second liquid is being caused to flow from the second container toward the downstream connector with the first open/close valve, the third open/close valve, and the collection flow path open/close valve closed and with the second open/close valve and the variable valve opened, the second open/close valve and the variable valve may be closed and the third open/close valve and the collection flow path open/close valve may be opened to start the third priming step. This mode is advantageous for reducing the likelihood that air mixes between the second liquid and the third liquid when the whole quantity of the second liquid in the second container is administered to a patient, and subsequently the third liquid is sequentially administered to the patient. 
     A third infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a collection flow path with one end in communication with a gas storing portion in the drip chamber, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A third priming method of the present invention for priming the third infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the collection container through the gas storing portion in the drip chamber and the collection flow path. 
     In the first priming step of the third priming method, the second open/close valve and the collection flow path open/close valve may be closed and the first open/close valve and the variable valve may be opened to cause the first liquid to flow from the first container toward the downstream connector. This is advantageous for priming the entire first flow path from the first connector to the downstream connector using the first liquid in a simply manner. 
     In the third priming method, after the first priming step, in a state where the first liquid is being caused to flow from the first container toward the downstream connector with the second open/close valve and the collection flow path open/close valve closed and with the first open/close valve and the variable valve opened, the first open/close valve and the variable valve may be closed and the second open/close valve and the collection flow path open/close valve may be opened to start the second priming step. Thus, drip injection of the first liquid can be readily switched to priming of the second flow path. 
     Preferably, the first open/close valve and the variable valve are closed when an interface between the first liquid and air that has flowed out, following the first liquid, from the first container reaches the section of the first flow path or when dripping of the first liquid in the drip chamber ends in a state where the first liquid is being caused to flow from the first container toward the downstream connector. This mode is advantageous for reducing the likelihood that air mixes between the first liquid and the second liquid in the case where the whole quantity of the first liquid in the first container is administered to a patient, and subsequently the second liquid is sequentially administered to the patient. 
     The third infusion set may further include: a third flow path having, at one end, a third connector, which is to be connected to a third container for storing a third liquid, another end of the third flow path being connected to the section of the first flow path; and a third open/close valve provided on the third flow path. The third priming method may further include a third priming step of causing the third liquid to flow from the third container into the third flow path and priming the third flow path using the third liquid. In the third priming step, the third liquid may move air that has been present in the third flow path toward the collection container through the gas storing portion in the drip chamber and the collection flow path. Thus, the third flow path can be primed using the third liquid stored in the third container that is connected to the third flow path. In the case where the third liquid is a hazardous medical solution, it is unlikely that the third liquid or air that has come into contact therewith leaks out to the outside. For this reason, the operator can prime the third flow path using the third liquid without being exposed to the medicine. 
     In the third priming step of the third priming method, the third liquid may move air that has flowed out of the second container following the second liquid, toward the collection container through the gas storing portion in the drip chamber and the collection flow path. This mode reduces the likelihood that air that has come into contact with the second liquid leaks out to the outside in the case where the second liquid is a hazardous medical solution. 
     In the third priming method, after the second priming step, when an interface between the second liquid and air that has flowed out, following the second liquid, from the second container reaches the section of the first flow path or when dripping of the second liquid in the drip chamber ends in a state where the second liquid is being caused to flow from the second container toward the downstream connector with the first open/close valve, the third open/close valve, and the collection flow path open/close valve closed and with the second open/close valve and the variable valve opened, the second open/close valve and the variable valve may be closed and the third open/close valve and the collection flow path open/close valve may be opened to start the third priming step. This mode is advantageous for reducing the likelihood that air mixes between the second liquid and the third liquid in the case where the whole quantity of the second liquid in the second container is administered to a patient, and subsequently the third liquid is sequentially administered to the patient. 
     A fourth infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a bypass flow path with one end in communication with a gas storing portion in the drip chamber, and another end in communication with a portion of the first flow path on the first connector side of the first open/close valve, or with the first connector; a bypass flow path open/close valve provided on the bypass flow path; a collection flow path with one end connected to the section of the first flow path, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A fourth priming method of the present invention for priming the fourth infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. The second priming step includes: a first part of the second priming step of moving, using the second liquid, air that has been present in the second flow path toward the collection container through the collection flow path; and a second part of the second priming step of moving, using the second liquid, air that is present forward of the second liquid in a direction in which the second liquid flows, toward the first container through the gas storing portion in the drip chamber and the bypass flow path. 
     In the first priming step of the fourth priming method, the second open/close valve, the bypass flow path open/close valve, and the collection flow path open/close valve may be closed and the first open/close valve and the variable valve may be opened to cause the first liquid to flow from the first container toward the downstream connector. This is advantageous for priming the entire first flow path from the first connector to the downstream connector using the first liquid in a simply manner. 
     In the fourth priming method, after the first priming step, in a state where the first liquid is being caused to flow from the first container toward the downstream connector with the second open/close valve, the bypass flow path open/close valve, and the collection flow path open/close valve closed and with the first open/close valve and the variable valve opened, the first open/close valve and the variable valve may be closed and the second open/close valve and the collection flow path open/close valve may be opened to start the first part of the second priming step and cause the second liquid to flow from the second container into the second flow path. After starting the first part of the second priming step, when the second liquid reaches the section of the first flow path, the collection flow path open/close valve may be closed and the bypass flow path open/close valve may be opened to start the second part of the second priming step and cause the second liquid to flow into the drip chamber. Thus, drip injection of the first liquid can be readily switched to priming of the second flow path. 
     Preferably, the first open/close valve and the variable valve are closed when an interface between the first liquid and air that has flowed out, following the first liquid, from the first container reaches the section of the first flow path or when dripping of the first liquid in the drip chamber ends in a state where the first liquid is being caused to flow from the first container toward the downstream connector. This mode is advantageous for reducing the likelihood that air mixes between the first liquid and the second liquid in the case where the whole quantity of the first liquid in the first container is administered to a patient, and subsequently the second liquid is sequentially administered to the patient. 
     The fourth infusion set may further include: a third flow path having, at one end, a third connector, which is to be connected to a third container for storing a third liquid, another end of the third flow path being connected to the section of the first flow path; and a third open/close valve provided on the third flow path. The fourth priming method may further include a third priming step of causing the third liquid to flow from the third container into the third flow path and priming the third flow path using the third liquid. The third priming step may include: a first part of the third priming step of moving, using the third liquid, air that has been present in the third flow path toward the collection container through the collection flow path; and a second part of the third priming step of moving, using the third liquid, air that is present forward of the third liquid in a direction in which the third liquid flows, toward the first container through the gas storing portion in the drip chamber and the bypass flow path. Thus, the third flow path can be primed using the third liquid stored in the third container that is connected to the third flow path. In the case where the third liquid is a hazardous medical solution, it is unlikely that the third liquid or air that has come into contact therewith leaks out to the outside. For this reason, the operator can prime the third flow path using the third liquid without being exposed to the medicine. 
     In the third priming step of the fourth priming method, the third liquid may move air that has flowed out of the second container following the second liquid, toward the collection container through the collection flow path, or toward the first container through the gas storing portion in the drip chamber and the bypass flow path. This mode reduces the likelihood that, in the case where the second liquid is a hazardous medical solution, air that has come into contact with the second liquid leaks out to the outside. 
     In the fourth priming method, after the second priming step, when an interface between the second liquid and air that has flowed out, following the second liquid, from the second container reaches the section of the first flow path, or when dripping of the second liquid in the drip chamber ends, in a state where the second liquid is being caused to flow from the second container toward the downstream connector with the first open/close valve, the third open/close valve, the bypass flow path open/close valve, and the collection flow path open/close valve closed and with the second open/close valve and the variable valve opened, the second open/close valve and the variable valve may be closed and the third open/close valve and the collection flow path open/close valve may be opened to start the first part of the third priming step and cause the third liquid to flow from the third container into the third flow path. After starting the first part of the third priming step, when the third liquid reaches the section of the first flow path, the collection flow path open/close valve may be closed and the bypass flow path open/close valve may be opened to start the second part of the third priming step and cause the third liquid to flow into the drip chamber. This mode is advantageous for reducing the likelihood that air mixes between the second liquid and the third liquid in the case where the whole quantity of the second liquid in the second container is administered to the patient, and subsequently the third liquid is sequentially administered to the patient. 
     A fifth infusion set of the present invention includes: a first flow path having, at one end, a first connector, which is to be connected to a first container for storing a first liquid, and having a downstream connector at another end; a first open/close valve, a drip chamber, and a variable valve that are provided in this order on the first flow path from the first connector side toward the downstream connector side; a second flow path having, at one end, a second connector, which is to be connected to a second container for storing a second liquid, another end of the second flow path being connected to a section of the first flow path between the first open/close valve and the drip chamber; a second open/close valve provided on the second flow path; a bypass flow path with one end in communication with a gas storing portion in the drip chamber, and another end in communication with a portion of the first flow path on the first connector side of the first open/close valve, or with the first connector; a bypass flow path open/close valve provided on the bypass flow path; a collection flow path with one end connected to a portion of the bypass flow path between the drip chamber and the bypass flow path open/close valve, the collection flow path having, at another end, a collection container connector, which is to be connected to a collection container; and a collection flow path open/close valve provided on the collection flow path. 
     A fifth priming method of the present invention for priming the fifth infusion set includes: a first priming step of causing the first liquid to flow from the first container into the first flow path and priming the first flow path using the first liquid; and a second priming step of causing the second liquid to flow from the second container into the second flow path and priming the second flow path using the second liquid. In the second priming step, the second liquid moves air that has been present in the second flow path toward the collection container through the gas storing portion in the drip chamber, the bypass flow path, and the collection flow path, or toward the first container through the gas storing portion in the drip chamber and the bypass flow path. 
     In the first priming step of the fifth priming method, the second open/close valve, the bypass flow path open/close valve, and the collection flow path open/close valve may be closed and the first open/close valve and the variable valve may be opened to cause the first liquid to flow from the first container toward the downstream connector. This is advantageous for priming the entire first flow path from the first connector to the downstream connector using the first liquid in a simply manner. 
     In the fifth priming method, after the first priming step, in a state where the first liquid is being caused to flow from the first container toward the downstream connector with the second open/close valve, the bypass flow path open/close valve, and the collection flow path open/close valve closed and with the first open/close valve and the variable valve opened, the first open/close valve and the variable valve may be closed, the second open/close valve may be opened, and the collection flow path open/close valve or the bypass flow path open/close valve may be opened to start the second priming step. Thus, drip injection of the first liquid can be readily switched to priming of the second flow path. 
     Preferably, the first open/close valve and the variable valve are closed when an interface between the first liquid and air that has flowed out, following the first liquid, from the first container reaches the section of the first flow path or when dripping of the first liquid in the drip chamber ends in a state where the first liquid is being caused to flow from the first container toward the downstream connector. This mode is advantageous for reducing the likelihood that air mixes between the first liquid and the second liquid in the case where the whole quantity of the first liquid in the first container is administered to a patient, and subsequently the second liquid is sequentially administered to the patient. 
     The fifth infusion set may further include: a third flow path having, at one end, a third connector, which is to be connected to a third container for storing a third liquid, another end of the third flow path being connected to the section of the first flow path; and a third open/close valve provided on the third flow path. The fifth priming method may further include a third priming step of causing the third liquid to flow from the third container into the third flow path and priming the third flow path using the third liquid. In the third priming step, the third liquid may move air that has been present in the third flow path toward the collection container through the gas storing portion in the drip chamber, the bypass flow path, and the collection flow path, or toward the first container through the gas storing portion in the drip chamber and the bypass flow path. Thus, the third flow path can be primed using the third liquid stored in the third container that is connected to the third flow path. In the case where the third liquid is a hazardous medical solution, it is unlikely that the third liquid or air that has come into contact therewith leaks out to the outside. For this reason, the operator can prime the third flow path using the third liquid without being exposed to the medicine. 
     In the third priming step of the fifth priming method, the third liquid may move air that has flowed out of the second container following the second liquid, toward the collection container through the gas storing portion in the drip chamber, the bypass flow path, and the collection flow path, or toward the first container through the gas storing portion in the drip chamber and the bypass flow path. This mode reduces the likelihood that, in the case where the second liquid is a hazardous medical solution, air that has come into contact with the second liquid leaks out to the outside. 
     In the fifth priming method, after the second priming step, when an interface between the second liquid and air that has flowed out, following the second liquid, from the second container reaches the section of the first flow path or when dripping of the second liquid in the drip chamber ends in a state where the second liquid is being flowed from the second container toward the downstream connector with the first open/close valve, the third open/close valve, the bypass flow path open/close valve, and the collection flow path open/close valve closed and with the second open/close valve and the variable valve opened, the second open/close valve and the variable valve may be closed, the third open/close valve may be opened, and the collection flow path open/close valve or the bypass flow path open/close valve may be opened to start the third priming step. This mode is advantageous for reducing the likelihood that air mixes between the second liquid and the third liquid in the case where the whole quantity of the second liquid in the second container is administered to a patient, and subsequently the third liquid is sequentially administered to the patient. 
     In the above-described first to fifth infusion sets of the present invention, the second connector may include a bar-shaped male member in which a flow path is formed, and a cover capable of being compressed and deformed in a longitudinal direction of the male member. When the second connector is connected to the second container, the cover may be compressed and deformed, and the male member may pass through the cover. When the second connector is separated from the second container, the cover may be restored to an initial state thereof and close a hole provided at or near a leading end of the male member and in communication with the flow path in the male member. According to this mode, even if the second connector is unintentionally separated from the second container, the likelihood that the second liquid leaks out to the outside can be reduced. This is advantageous for preventing the operator from being exposed to the medicine during priming in the case where the second liquid is a hazardous medical solution. 
     In the above-described first to fifth infusion sets of the present invention, the third connector may include a bar-shaped male member in which a flow path is formed, and a cover capable of being compressed and deformed in a longitudinal direction of the male member, similarly to the second connector. This is advantageous for preventing the operator from being exposed to the medicine during priming in the case where the third liquid is a hazardous medical solution. 
     Hereinafter, the present invention will be described in detail while illustrating preferable embodiments. Needless to say, however, the present invention is not limited to the following embodiments. The drawings that are referenced in the following description show main members that constitute the embodiments of the present invention in a simplified manner for convenience of description. Accordingly, the present invention may include any member that is not shown in the following diagrams. Also, members shown in the following diagrams may be changed or omitted within the scope of the present invention. In the drawings referenced in the description of the embodiments, members that correspond to members that are shown in a diagram referenced in a preceding embodiment are assigned the same reference signs as those in the drawing illustrating the preceding embodiment. Redundant descriptions of such members are omitted, and description of the preceding embodiment should be considered where appropriate. 
     Embodiment 1 
       FIG. 1  shows a schematic configuration of an infusion set  1  according to Embodiment 1 of the present invention. The infusion set  1  is used to sequentially administer, to a patient, a first liquid to a fourth liquid, which are stored respectively in a first container  20   a  to a fourth container  20   d.    
     For example, the first liquid stored in the first container  20   a  may be a medical solution that contains a premedication, the second and third liquids stored in the second and third containers  20   b  and  20   c  may be hazardous medical solutions that contain an anti-cancer agent, and the fourth liquid stored in the fourth container  20   d  may be a physiological saline for washing out flow paths. The first container  20   a  to the fourth container  20   d  are sealed infusion bags, each of which is constituted by two soft sheets that are adhered to each other at their peripheral edge portions. The first container  20   a  to the fourth container  20   d  include ports  21   a  to  21   d , respectively, for drawing out the stored liquids. Openings of the ports  21   a  to  21   d  are sealed by rubber plugs (which are not visible in  FIG. 1 ). In addition to the aforementioned liquids, a small amount of air is stored in the first to fourth containers  20   a  to  20   d .  FIG. 1  only shows portions of the first to fourth containers  20   a  to  20   d  near the ports  21   a  to  21   d.    
     The infusion set  1  includes a first flow path  10   a , which serves as a main line. The first flow path  10   a  is constituted by a soft tube that is transparent and hollow. The first flow path  10   a  has a first connector  11   a  and a downstream connector  19  at an upstream end and a downstream end thereof, respectively. The first connector  11   a  and the downstream connector  19  are in communication with each other via the first flow path  10   a . The first connector  11   a  is a puncture needle (which may also be called a spike) that has an acute tip, and is inserted into the rubber plug provided in the port  21   a  of the first container  20   a . The downstream connector  19  is connected to a connector  32 , which is provided at an upstream end of a soft tube  30 . A needle  31 , which is to be inserted into a patient&#39;s vein, is provided at a downstream end of the tube  30 . 
     A first open/close valve  12   a , a drip chamber  14 , and a variable valve  17  are provided in this order from the first connector  11   a  side toward the downstream connector  19  side, on the first flow path  10   a . The first open/close valve  12   a  switches between a state of allowing a liquid in the first flow path  10   a  to flow and a state of not allowing this liquid to flow, by opening and closing the first flow path  10   a . Although the first open/close valve  12   a  is not limited, but may be a clamp that is known in the medical field, for example. The drip chamber  14  makes flowing of a liquid through the first flow path  10   a  visible. The variable valve  17  adjusts the flow rate of the liquid flowing through the first flow path  10   a  by compressing the first flow path  10   a  in a diameter direction and adjusting the cross-sectional area of the first flow path  10   a . Although the variable valve  17  is not limited, but may be a roller clip that is known in the medical field, for example. 
     The infusion set  1  also includes a second flow path  10   b , a third flow path  10   c , and a fourth flow path  10   d , which serve as side-injection lines. The second to fourth flow paths  10   b  to  10   d  are constituted by soft tubes that are transparent and hollow, similarly to the first flow path  10   a . The second, third, and fourth flow paths  10   b ,  10   c , and  10   d  have second, third, and fourth connectors  11   b ,  11   c , and  11   d , respectively, at their upstream ends. The second to fourth connectors  11   b  to  11   d  are lever lock connectors each including a male member and a lock lever with a claw (e.g. see Patent Document 2). The second to fourth connectors  11   b  to  11   d  are connected to the ports  21   b  to  21   d  of the second to fourth containers  20   b  to  20   d  via adapters  22   b  to  22   d , respectively. Each of the adapters  22   b  to  22   d  includes a puncture needle, which has an acute tip capable of being inserted into a corresponding one of the rubber plugs in the ports  21   b  to  21   d , an engaging claw, which is to engage with a corresponding one of the ports  21   b  to  21   d , and a mixture injection port, which has an elastic partition member called a septum (e.g. see Patent Document 3). The male members of the second to fourth connectors  11   b  to  11   d  are inserted into the elastic partition members of the mixture injection ports, and the claws of the second to fourth connectors  11   b  to  11   d  engage with the mixture injection ports of the ports  21   b  to  21   d . Connecting the second to fourth flow paths  10   b  to  10   d  to the ports  21   b  to  21   d  via the second to fourth connectors  11   b  to  11   d  and the adapters  22   b  to  22   d  is advantageous in reducing the likelihood of a hazardous medicine, such as an anti-cancer agent, leaking out to the outside and an operator being exposed to the medicine. 
     The second to fourth flow paths  10   b  to  10   d  are brought into communication with a section of the first flow path  10   a  between the first open/close valve  12   a  and the drip chamber  14  (this section will be referred to as a “branch section”). In  FIG. 1 , one branch flow path  10   x  branches from a first branching portion  18   a , which is provided on the first flow path  10   a  and has a T-shape (or a Y-shape), second and third branching portions  18   b  and  18   c , which have a T-shape (or a Y-shape), are provided in this order on the branch flow path  10   x , a second flow path  10   b  branches from the second branching portion  18   b , and a third flow path  10   c  and a fourth flow path  10   d  branch from the third branching portion  18   c . In the present invention, the second to fourth flow paths (side-injection lines)  10   b  to  10   d  mean portions from the second to fourth connectors  11   b  to  11   d , respectively, to the first flow path (main line)  10   a . Accordingly, in the configuration in  FIG. 1 , each of the second to fourth flow paths  10   b  to  10   d  has a flow path portion that is shared with the other flow paths, and a unique flow path portion that is distinguished from the other flow paths. 
     Second, third, and fourth open/close valves  12   b ,  12   c , and  12   d  are provided on the second, third, and fourth flow paths  10   b ,  10   c , and  10   d , respectively. As shown in  FIG. 1 , if the second to fourth flow paths  10   b  to  10   d  have, as a portion thereof, a flow path portion shared by the other flow paths, the second to fourth open/close valves  12   b  to  12   d  are provided in unique flow path portions of the second to fourth flow paths  10   b  to  10   d  that are distinguished from the other flow paths. The second to fourth open/close valves  12   b  to  12   d  switch between a state of allowing liquids in the second to fourth flow paths  10   b  to  10   d  to flow and a state of not allowing the liquids to flow by opening and closing the second to fourth flow paths  10   b  to  10   d , similarly to the first open/close valve  12   a . The second to fourth open/close valves  12   b  to  12   d  are not limited, but may be clamps that are known in the medical field, for example. 
     A description will be given of a priming method for the infusion set  1  according to Embodiment 1 that is configured as described above. All operations in the following priming method are manually performed by an operator. However, some of the operations may be automatically performed. Similar to general infusion, the first to fourth liquids flow in the infusion set  1  using gravity. 
     The first container  20   a  to the fourth container  20   d , in which the first liquid to the fourth liquid are stored, respectively, are suspended from, for example, an irrigator stand (not shown), with the ports  21   a  to  21   d  facing downward. The adapters  22   b  to  22   d  are attached to the ports  21   b  to  21   d.    
     An infusion set  1  with the first to fourth open/close valves  12   a  to  12   d  and the variable valve  17  in a closed state is prepared. The first connector  11   a  in the infusion set  1  is connected to the port  21   a  of the first container  20   a , and the second to fourth connectors  11   b  to  11   d  in the infusion set  1  are connected to the adapters  22   b  to  22   d , respectively. The first flow path  10   a  is suspended in a substantially vertical direction due to gravity such that the first connector  11   a , the first open/close valve  12   a , the drip chamber  14 , and the variable valve  17  are arranged in this order from the upper side toward the lower side. The second to fourth containers  20   b  to  20   d  are arranged at positions higher than the first open/close valve  12   a . The downstream connector  19  is connected to the connector  32 . 
     Initially, the first flow path  10   a  is primed using the first liquid (e.g. a premedication) in the first container  20   a . That is to say, the first open/close valve  12   a  and the variable valve  17  are opened. The first liquid in the first container  20   a  flows from the first connector  11   a  into the first flow path  10   a . When the first liquid reaches the tip of the needle  31  that is provided further downstream of the downstream connector  19 , the first open/close valve  12   a  and/or the variable valve  17  are closed once. A flow path that extends from the first container  20   a  to the needle  31  through the first flow path  10   a  and the tube  30  is filled with the first liquid. 
     Next, the needle  31  is inserted into a patient&#39;s vein. 
     Next, the first open/close valve  12   a  and the variable valve  17  are opened again. A drip of the first liquid is started. The flow rate of the first liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the first liquid takes a predetermined value. 
     Upon the first liquid in the first container  20   a  running out, air in the first container  20   a  flows out, following the first liquid, from the port  21   a  into the first flow path  10   a . An interface (gas-liquid interface or liquid surface) between the first liquid and the air moves down in the first flow path  10   a . When the gas-liquid interface reaches the first branching portion  18   a , the variable valve  17  is closed. The drip of the first liquid is temporarily discontinued. A portion from the first branching portion  18   a  to the first container  20   a  is filled with the air that has flowed out of the first container  20   a , and a portion on the downstream side (on the downstream connector  19  side) of the first branching portion  18   a  is filled with the first liquid. 
     Next, the second open/close valve  12   b  is opened. The second liquid in the second container  20   b  flows into the second flow path  10   b . Since the variable valve  17  and the third and fourth open/close valves  12   c  and  12   d  are closed, the second liquid moves air that has been present in the second flow path  10   b  toward the first container  20   a  through the first branching portion  18   a  and the first flow path  10   a  in this order. 
     When an interface (gas-liquid interface or liquid surface) between the air and the second liquid reaches the first branching portion  18   a , the first open/close valve  12   a  is closed, and the variable valve  17  is opened. The second liquid moves down the first flow path  10   a  through the first branching portion  18   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. The flow rate of the second liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the second liquid takes a predetermined value. Air that has been present in the second flow path  10   b  before opening the second open/close valve  12   b  is confined to a portion of the first flow path  10   a  on the upstream side (on the first container  20   a  side) of the first branching portion  18   a , and the first container  20   a.    
     Upon the second liquid in the second container  20   b  running out, air in the second container  20   b  flows out, following the second liquid, from the port  21   b  into the second flow path  10   b . An interface (gas-liquid interface or liquid surface) between the second liquid and the air moves down in the second flow path  10   b . When the gas-liquid interface reaches the first branching portion  18   a , the second open/close valve  12   b  and the variable valve  17  are closed. The drip of the second liquid is temporarily discontinued. A portion from the first branching portion  18   a  to the second container  20   b  is filled with the air that has flowed out of the second container  20   b , and a portion on the downstream side (on the downstream connector  19  side) of the first branching portion  18   a  is filled with the second liquid. 
     Next, the first open/close valve  12   a  and the third open/close valve  12   c  are opened. The third liquid in the third container  20   c  flows into the third flow path  10   c . Since the variable valve  17  and the second and fourth open/close valves  12   b  and  12   d  are closed, the third liquid moves air that has been present in the third flow path  10   c  toward the first container  20   a  through the first branching portion  18   a  and the first flow path  10   a  in this order. 
     When an interface (gas-liquid interface or liquid surface) between the air and the third liquid reaches the first branching portion  18   a , the first open/close valve  12   a  is closed, and the variable valve  17  is opened. The third liquid moves down the first flow path  10   a  through the first branching portion  18   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. The flow rate of the third liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the third liquid takes a predetermined value. Air that has been present in the third flow path  10   c  before opening the third open/close valve  12   c  is confined to a portion of the first flow path  10   a  on the upstream side (on the first container  20   a  side) of the first branching portion  18   a , and the first container  20   a.    
     Then, the fourth flow path  10   d  is primed using the fourth liquid in the fourth container  20   d , and subsequently a drip of the fourth liquid is given, in accordance with the same procedure. After the fourth liquid in the fourth container  20   d  has run out, the fourth open/close valve  12   d  and the variable valve  17  are closed. The drips of the first liquid to the fourth liquid thus end. The needle  31  is pulled out of the patient. The infusion set  1  is discarded with the first container  20   a  to the fourth container  20   d  and the tube  30  connected thereto. 
     As described above, with the infusion set  1  according to Embodiment 1, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed, line-by-line, after a drip of the first liquid has started and immediately before a drip of the liquids (second liquid to fourth liquids) corresponding to the respective side-injection lines starts. Furthermore, the liquids stored in the container connected to the respective side-injection lines are used as priming solutions for the side-injection lines. 
     When priming is performed for an infusion set in which at least one side-injection line branches from one main line, such as the infusion set  1  according to Embodiment 1, conventionally, a method called back-priming (also referred to as “priming-back”) is often employed in which, for the side-injection line, a priming solution is caused to flow back from the main line to the side-injection line. Back-priming needs to be performed before a container is connected to the side-injection line. If, after the container has been connected to the side-injection line, air remaining in a portion of a flow path of the infusion set is found, it is necessary to remove the container from the side-injection line and perform back-priming again, making the operation complex. In addition, if back-priming is performed, the entire infusion set including the main line and the side-injection line is filled with the same priming solution. Accordingly, in the case of giving a drip of a liquid in the container connected to the side-injection line to the patient, a drip of the priming solution is necessarily given before the drip of the liquid. 
     In the priming method for the infusion set  1  according to Embodiment 1, priming is performed after the containers (first to fourth containers  20   a  to  20   d ) have been connected to all of the main line (first flow path  10   a ) and the side-injection lines (second to fourth flow paths  10   b  to  10   d ). Moreover, the main line and the side-injection lines are primed immediately before a drip of the liquid in the container connected to each of those lines is given. Since priming is performed line-by-line, operational errors, such as air remaining in a line being overlooked, are unlikely to occur. 
     In Embodiment 1, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed using the liquids stored in the containers that are connected to the respective side-injection lines. Accordingly, in the case of sequentially giving drips of the first to fourth liquids, the problem does not occur that a drip of a priming solution used in common is necessarily given before the drip of each liquid as with the conventional technique. 
     If the liquids (second and third liquids) stored in the containers (second and third containers  20   b  and  20   c ) connected to the side-injection lines (second and third flow paths  10   b  and  10   c ) are hazardous medical solutions such as an anti-cancer agent, there is a possibility that air that has come into contact with these hazardous medical solutions contain vapor of the hazardous medical solutions. In Embodiment 1, air that has been present in the side-injection lines (second and third flow paths  10   b  and  10   c ) before being primed is confined to the infusion set  1  and the first container  20   a  due to priming of these side-injection lines (second and third flow paths  10   b  and  10   c ) and does not leak out to the outside. In addition, air that has flowed out, following the liquids (second and third liquids), from the containers (second and third containers  20   b  and  20   c ) to the side-injection lines (second and third flow paths  10   b  and  10   c ) is also confined to the infusion set  1  and the first container  20   a  due to priming of other side-injection lines (third and fourth flow paths  10   c  and  10   d ) that is to be performed immediately after the outflow of the air, and does not leak out to the outside. Thus, in Embodiment 1, even if a side-injection line is primed using a hazardous medical solution, the hazardous medical solution and vapor thereof do not leak out to the outside. This is advantageous for reducing the likelihood that the operator who performs priming is exposed to the medicine. 
     In the above-described priming method for the infusion set  1 , the variable valve  17  is switched to an open or closed state when an interface (gas-liquid interface) between any of the first to fourth liquids and air reaches the first branching portion  18   a . However, in the present invention, the time when the gas-liquid interface reaches the first branching portion  18   a  need not accurately coincide with the time when the variable valve  17  is switched. Commonly, the variable valve  17  need only be switched to an open or close state when the gas-liquid interface reaches a section (branch section) of the first flow path  10   a  between the first open/close valve  12   a  and the drip chamber  14 . 
     Embodiment 2 
     An infusion set  2  and a priming method for the infusion set  2  according to Embodiment 2 of the present invention will be described, mainly regarding differences from Embodiment 1.  FIG. 2  shows a schematic configuration of the infusion set  2 . The infusion set  2  includes a bypass flow path  10   g  that brings a gas storing portion of the drip chamber  14  into communication with a portion of the first flow path  10   a  on the upstream side (on the first connector  11   a  side) of the first open/close valve  12   a  or the first connector  11   a , and an open/close valve (bypass flow path open/close valve)  12   g  that is provided on the bypass flow path  10   g.    
     The bypass flow path  10   g  is not limited, but may be constituted by a hollow, soft tube, similarly to the first to fourth flow paths  10   a  to  10   d . A lower end of the bypass flow path  10   g  is brought into communication with a portion in which air is present above a liquid surface in the drip chamber  14  (this portion will be called a gas storing portion). Ordinarily, the drip chamber  14  is constituted by a chamber in which a liquid is stored and that is transparent and has a cylindrical shape, and a cap for closing an opening at an upper end of the chamber. In the infusion set  2  in  FIG. 2 , a lower end of the bypass flow path  10   g  is connected to the cap. As long as the bypass flow path  10   g  is in communication with the gas storing portion in the drip chamber  14 , the lower end of the bypass flow path  10   g  may be connected to the chamber. The bypass flow path  10   g  brings the gas storing portion in the drip chamber  14  into communication with a portion of the first flow path  10   a  on the upstream side (on the first container  20   a  side) of the first open/close valve  12   a , when the first open/close valve  12   a  is closed. In the infusion set  2  in  FIG. 2 , an upper end of the bypass flow path  10   g  is connected to a base end of the first connector  11   a , but may alternatively be connected to a portion of the first flow path  10   a  between the first open/close valve  12   a  and the first connector  11   a.    
     The open/close valve  12   g  is not limited, but may be a clamp that is known in the medical field, similarly to the first to fourth open/close valves  12   a  to  12   d.    
     A description will be given of a priming method for the infusion set  2  according to Embodiment 2 that is configured as described above. 
     The first container  20   a  to the fourth container  20   d , in which the first liquid to the fourth liquid are stored, respectively, are suspended from, for example, an irrigator stand (not shown), with the ports  21   a  to  21   d  facing downward. The adapters  22   b  to  22   d  are attached to the ports  21   b  to  21   d.    
     An infusion set  2  with the first to fourth open/close valves  12   a  to  12   d , the open/close valve  12   g , and the variable valve  17  in a closed state is prepared. The first connector  11   a  in the infusion set  2  is connected to the port  21   a  of the first container  20   a , and the second to fourth connectors  11   b  to  11   d  in the infusion set  2  are connected to the adapters  22   b  to  22   d , respectively. The first flow path  10   a  is suspended in a substantially vertical direction due to gravity such that the first connector  11   a , the first open/close valve  12   a , the drip chamber  14 , and the variable valve  17  are arranged in this order from the upper side toward the lower side. The second to fourth containers  20   b  to  20   d  are arranged at positions higher than the first open/close valve  12   a . The downstream connector  19  is connected to the connector  32 . 
     Initially, the first flow path  10   a  is primed using the first liquid (e.g. a premedication) in the first container  20   a . That is to say, the first open/close valve  12   a  and the variable valve  17  are opened. The first liquid in the first container  20   a  flows from the first connector  11   a  into the first flow path  10   a . When the first liquid reaches the tip of the needle  31  that is provided further downstream of the downstream connector  19 , the first open/close valve  12   a  and/or the variable valve  17  are closed once. A flow path that extends from the first container  20   a  to the needle  31  through the first flow path  10   a  and the tube  30  is filled with the first liquid. 
     Next, the needle  31  is inserted into a patient&#39;s vein. 
     Next, the first open/close valve  12   a  and the variable valve  17  are opened again. A drip of the first liquid is started. The flow rate of the first liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the first liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). 
     Upon the first liquid in the first container  20   a  running out, air in the first container  20   a  flows out, following the first liquid, from the port  21   a  into the first flow path  10   a . An interface (gas-liquid interface or liquid surface) between the first liquid and the air moves down in the first flow path  10   a . When dripping of the first liquid in the drip chamber  14  ends, the first open/close valve  12   a  and the variable valve  17  are closed. The drip of the first liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the first container  20   a  is filled with the air that has flowed out of the first container  20   a , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the first liquid. 
     Next, the open/close valve  12   g  and the second open/close valve  12   b  are opened. The second liquid in the second container  20   b  flows into the second flow path  10   b . Since the variable valve  17  and the first, third, and fourth open/close valves  12   a ,  12   c , and  12   d  are closed, the second liquid moves air that has been present in the second flow path  10   b  toward the first container  20   a  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , and the bypass flow path  10   g  in this order. The second liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the second liquid has started in the drip chamber  14 , the open/close valve  12   g  is closed, and the variable valve  17  is opened. Thereafter, the second liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. The flow rate of the second liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the second liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the second flow path  10   b  before the second open/close valve  12   b  is opened is confined to the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , and the first container  20   a.    
     Upon the second liquid in the second container  20   b  running out, air in the second container  20   b  flows out, following the second liquid, from the port  21   b  into the second flow path  10   b . An interface (gas-liquid interface or liquid surface) between the second liquid and the air moves down in the second flow path  10   b . When dripping of the second liquid in the drip chamber  14  ends, the second open/close valve  12   b  and the variable valve  17  are closed. The drip of the second liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the second container  20   b  is filled with the air that has flowed out of the second container  20   b , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the second liquid. 
     Next, the open/close valve  12   g  and the third open/close valve  12   c  are opened. The third liquid in the third container  20   c  flows into the third flow path  10   c . Since the variable valve  17  and the first, second, and fourth open/close valves  12   a ,  12   b , and  12   d  are closed, the third liquid moves air that has been present in the third flow path  10   c  toward the first container  20   a  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , and the bypass flow path  10   g  in this order. The third liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the third liquid has started in the drip chamber  14 , the open/close valve  12   g  is closed, and the variable valve  17  is opened. Thereafter, the third liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. The flow rate of the third liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the third liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the third flow path  10   c  before the third open/close valve  12   c  is opened is confined to the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , and the first container  20   a.    
     Then, the fourth flow path  10   d  is primed using the fourth liquid in the fourth container  20   d , and subsequently a drip of the fourth liquid is given, in accordance with the same procedure. After the fourth liquid in the fourth container  20   d  has run out, the fourth open/close valve  12   d  and the variable valve  17  are closed. The drips of the first liquid to the fourth liquid thus end. The needle  31  is pulled out of the patient. The infusion set  2  is discarded with the first container  20   a  to the fourth container  20   d  and the tube  30  connected thereto. 
     Similarly to Embodiment 1, with the infusion set  2  according to Embodiment 2, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed, line-by-line, after a drip of the first liquid has started and immediately before a drip of the liquids (second liquid to fourth liquids) corresponding to the respective side-injection lines starts. Furthermore, the liquids stored in the container connected to the respective side-injection lines are used as priming solutions for the side-injection lines. 
     Air that has been present in the side-injection lines (second and third flow paths  10   b  and  10   c ) before being primed is confined to the infusion set  2  and the first container  20   a  due to priming of these side-injection lines (second and third flow paths  10   b  and  10   c ) and does not leak out to the outside. In addition, air that has flowed out, following the liquids (second and third liquids), from the containers (second and third containers  20   b  and  20   c ) to the side-injection lines (second and third flow paths  10   b  and  10   c ) is also confined to the infusion set  2  and the first container  20   a  due to priming of other side-injection lines (third and fourth flow paths  10   c  and  10   d ) that is to be performed immediately after the outflow of the air, and does not leak out to the outside. Even if a side-injection line is primed using a hazardous medical solution, the hazardous medical solution and vapor thereof do not leak out to the outside. This is advantageous for reducing the likelihood that the operator who performs priming is exposed to the medicine. 
     In the above-described priming method for the infusion set  2 , the first to fourth open/close valves  12   a  to  12   d  and the variable valve  17  are closed when dripping of the first to fourth liquids ends in the drip chamber  14 . However, in the present invention, the time when dripping of the first to fourth liquids ends in the drip chamber  14  need not accurately coincide with the time when the valves  12   a  to  12   d  and  17  are closed. The valves  12   a  to  12   d  and  17  may be closed before dripping in the drip chamber  14  ends. Specifically, the valves  12   a  to  12   d  and  17  may be closed when an interface (gas-liquid interface) between any of the first to fourth liquids and the following air reaches a section (branch section) of the first flow path  10   a  between the first open/close valve  12   a  and the drip chamber  14 . 
     Embodiment 2 is the same as Embodiment 1, except for the above-described configuration. The descriptions of Embodiment 1 also apply to Embodiment 2 as appropriate. 
     Embodiment 3 
     An infusion set  3  and a priming method for the infusion set  3  according to Embodiment 3 of the present invention will be described, mainly regarding differences from Embodiments 1 and 2.  FIG. 3  shows a schematic configuration of the infusion set  3 . The infusion set  3  includes a collection container  20   z  and a collection flow path  10   z.    
     The collection container  20   z  is a sealed container, and it is preferable that the shape thereof changes in accordance with the amount of content (gas) in the collection container  20   z . The collection container  20   z  is not limited, but may be, for example, a bag constituted by two soft sheets that are adhered to each other at their peripheral edge portions, similarly to the first container  20   a  to the fourth container  20   d . The collection container  20   z  includes a port  21   z . An opening of the port  21   z  is sealed by a rubber plug (which is not visible in  FIG. 3 ). 
     The collection flow path  10   z  constitutes a collection line that brings the collection container  20   z  into communication with the first flow path  10   a  (main line). The collection flow path  10   z  is constituted by a hollow, soft tube, similarly to the first to fourth flow paths  10   a  to  10   d . One end of the collection flow path  10   z  is in communication with the first branching portion  18   a , and the other end of the collection flow path  10   z  is provided with a connector (collection container connector)  11   z . The connector  11   z  is connected to the port  21   z  of the collection container  20   z  via an adapter (collection container adapter)  22   z . The connector  11   z  is a lever lock connector that is the same as the second to fourth connectors  11   b  to  11   d  (e.g. see Patent Document 2). The adapter  22   z  is the same as the second to fourth adapters  22   b  to  22   d  (e.g. see Patent Document 3). 
     An open/close valve (collection flow path open/close valve)  12   z  is provided on the collection flow path  10   z . The open/close valve  12   z  switches between a state of allowing a gas in the collection flow path  10   z  to flow and a state of not allowing the gas to flow by opening and closing the collection flow path  10   z , similarly to the first to fourth open/close valves  12   a  to  12   d . Although the open/close valve  12   z  is not limited, but may be a clamp that is known in the medical field, for example. 
     A description will be given of a priming method for the infusion set  3  according to Embodiment 3 that is configured as described above. 
     The first container  20   a  to the fourth container  20   d , in which the first liquid to the fourth liquid are stored, respectively, are suspended from, for example, an irrigator stand (not shown), with the ports  21   a  to  21   d  facing downward. The adapters  22   b  to  22   d  are attached to the ports  21   b  to  21   d.    
     An infusion set  3  with the first to fourth open/close valves  12   a  to  12   d , the open/close valve  12   z , and the variable valve  17  in a closed state is prepared. Also, an empty collection container  20   z  with the port  21   z  to which the adapter  22   z  is attached is prepared. The first connector  11   a  in the infusion set  3  is connected to the port  21   a  of the first container  20   a , the second to fourth connectors  11   b  to  11   d  in the infusion set  3  are connected to the adapters  22   b  to  22   d , respectively, and the connector  11   z  is connected to the adapter  22   z . The first flow path  10   a  is suspended in a substantially vertical direction due to gravity such that the first connector  11   a , the first open/close valve  12   a , the drip chamber  14 , and the variable valve  17  are arranged in this order from the upper side toward the lower side. The second to fourth containers  20   b  to  20   d  are arranged at positions higher than the first open/close valve  12   a . The downstream connector  19  is connected to the connector  32 . 
     Initially, the first flow path  10   a  is primed using the first liquid (e.g. a premedication) in the first container  20   a . That is to say, the first open/close valve  12   a  and the variable valve  17  are opened. The first liquid in the first container  20   a  flows from the first connector  11   a  into the first flow path  10   a . When the first liquid reaches the tip of the needle  31  that is provided further downstream of the downstream connector  19 , the first open/close valve  12   a  and/or the variable valve  17  are closed once. A flow path that extends from the first container  20   a  to the needle  31  through the first flow path  10   a  and the tube  30  is filled with the first liquid. 
     Next, the needle  31  is inserted into a patient&#39;s vein. 
     Next, the first open/close valve  12   a  and the variable valve  17  are opened again. A drip of the first liquid is started. The flow rate of the first liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the first liquid takes a predetermined value. 
     Upon the first liquid in the first container  20   a  running out, air in the first container  20   a  flows out, following the first liquid, from the port  21   a  into the first flow path  10   a . An interface (gas-liquid interface or liquid surface) between the first liquid and the air moves down in the first flow path  10   a . When the gas-liquid interface reaches the first branching portion  18   a , the first open/close valve  12   a  and the variable valve  17  are closed. The drip of the first liquid is temporarily discontinued. A portion from the first branching portion  18   a  to the first container  20   a  is filled with the air that has flowed out of the first container  20   a , and a portion on the downstream side (on the downstream connector  19  side) of the first branching portion  18   a  is filled with the first liquid. 
     Next, the open/close valve  12   z  and the second open/close valve  12   b  are opened. The second liquid in the second container  20   b  flows into the second flow path  10   b . Since the variable valve  17  and the first, third, and fourth open/close valves  12   a ,  12   c , and  12   d  are closed, the second liquid moves air that has been present in the second flow path  10   b  toward the collection container  20   z  through the first branching portion  18   a , and the collection flow path  10   z  in this order. 
     When an interface (gas-liquid interface or liquid surface) between the air and the second liquid reaches the first branching portion  18   a , the open/close valve  12   z  is closed, and the variable valve  17  is opened. The second liquid moves down the first flow path  10   a  through the first branching portion  18   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. The flow rate of the second liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the second liquid takes a predetermined value. Air that has been present in the second flow path  10   b  before opening the second open/close valve  12   b  is confined to the collection flow path  10   z  and the collection container  20   z.    
     Upon the second liquid in the second container  20   b  running out, air in the second container  20   b  flows out, following the second liquid, from the port  21   b  into the second flow path  10   b . An interface (gas-liquid interface or liquid surface) between the second liquid and the air moves down in the second flow path  10   b . When the gas-liquid interface reaches the first branching portion  18   a , the second open/close valve  12   b  and the variable valve  17  are closed. The drip of the second liquid is temporarily discontinued. A portion from the first branching portion  18   a  to the second container  20   b  is filled with the air that has flowed out of the second container  20   b , and a portion on the downstream side (on the downstream connector  19  side) of the first branching portion  18   a  is filled with the second liquid. 
     Next, the open/close valve  12   z  and the third open/close valve  12   c  are opened. The third liquid in the third container  20   c  flows into the third flow path  10   c . Since the variable valve  17  and the first, second, and fourth open/close valves  12   a ,  12   b , and  12   d  are closed, the third liquid moves air that has been present in the third flow path  10   c  toward the collection container  20   z  through the first branching portion  18   a  and the collection flow path  10   z  in this order. 
     When an interface (gas-liquid interface or liquid surface) between the air and the third liquid reaches the first branching portion  18   a , the open/close valve  12   z  is closed, and the variable valve  17  is opened. The third liquid moves down the first flow path  10   a  through the first branching portion  18   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. The flow rate of the third liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the third liquid takes a predetermined value. Air that has been present in the third flow path  10   c  before opening the third open/close valve  12   c  is confined to the collection flow path  10   z  and the collection container  20   z.    
     Then, the fourth flow path  10   d  is primed using the fourth liquid in the fourth container  20   d , and subsequently a drip of the fourth liquid is given, in accordance with the same procedure. After the fourth liquid in the fourth container  20   d  has run out, the fourth open/close valve  12   d  and the variable valve  17  are closed. The drips of the first liquid to the fourth liquid thus end. The needle  31  is pulled out of the patient. The infusion set  3  is discarded with the first container  20   a  to the fourth container  20   d , the collection container  20   z , and the tube  30  connected thereto. 
     Similarly to Embodiment 1, with the infusion set  2  according to Embodiment 3, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed, line-by-line, after a drip of the first liquid has started and immediately before a drip of the liquids (second liquid to fourth liquids) corresponding to the respective side-injection lines starts. Furthermore, the liquids stored in the container connected to the respective side-injection lines are used as priming solutions for the side-injection lines. 
     Air that has been present in the side-injection lines (second and third flow paths  10   b  and  10   c ) before being primed is confined to the infusion set  3  and the collection container  20   z  due to priming of these side-injection lines (second and third flow paths  10   b  and  10   c ) and does not leak out to the outside. In addition, air that has flowed out, following the liquids (second and third liquids), from the containers (second and third containers  20   b  and  20   c ) to the side-injection lines (second and third flow paths  10   b  and  10   c ) is also confined to the infusion set  3  and the collection container  20   z  due to priming of other side-injection lines (third and fourth flow paths  10   c  and  10   d ) that is to be performed immediately after the outflow of the air, and does not leak out to the outside. Even if a side-injection line is primed using a hazardous medical solution, the hazardous medical solution and vapor thereof do not leak out to the outside. This is advantageous for reducing the likelihood that the operator who performs priming is exposed to the medicine. 
     Air that has been discharged from the side-injection lines due to priming is collected into the first container  20   a  in Embodiments 1 and 2, whereas, in Embodiment 3, discharged air is collected into the dedicated collection container  20   z . The collection container  20   z  need not have the same configuration as the first container  20   a  to the fourth container  20   d , and may be modified in any manner to have a configuration appropriate for collecting air, for example. A container that has a capacity corresponding to the flow path volume of the side-injection lines can be selected as the collection container  20   z . The configuration of the collection line that brings the collection container  20   z  into communication with the first branching portion  18   a  is not limited to that shown in  FIG. 3  either. A configuration may alternatively be employed in which the adapter  22   z  and the connector  11   z  are omitted, and the tube that constitutes the collection flow path  10   z  is directly connected to the collection container  20   z . In this case, a terminal of the tube connected to the collection container  20   z  corresponds to the collection container connector. 
     In the above-described priming method for the infusion set  3 , the first to fourth open/close valves  12   a  to  12   d  and the variable valve  17  are closed when an interface (gas-liquid interface) between the first to fourth liquids and air that has been present in the first to fourth containers  20   a  to  20   d  reaches the first branching portion  18   a , respectively. However, in the present invention, the time when the gas-liquid interface reaches the first branching portion  18   a  need not accurately coincide with the time when the valves  12   a  to  12   d  and  17  are closed. Commonly, the valves  12   a  to  12   d  and  17  need only be closed when the gas-liquid interface reaches a section (branch section) between the first open/close valve  12   a  and the drip chamber  14 . 
     In  FIG. 3 , the collection flow path  10   z  is connected to the first branching portion  18   a , but the present invention is not limited thereto. The collection flow path  10   z  need only be connected to a section (branch section) of the first flow path  10   a  between the first open/close valve  12   a  and the drip chamber  14 . 
     Embodiment 3 is the same as Embodiments 1 and 2, except for the above-described configuration. The descriptions of Embodiments 1 and 2 also apply to Embodiment 3. 
     Embodiment 4 
     An infusion set  4  and a priming method for the infusion set  4  according to Embodiment 4 of the present invention will be described, mainly regarding differences from Embodiments 1 to 3.  FIG. 4  shows a schematic configuration of the infusion set  4 . Similarly to the infusion set  3  (see  FIG. 3 ) according to Embodiment 3, the infusion set  4  includes the collection container  20   z  and the collection flow path  10   z . However, unlike Embodiment 3, the collection flow path  10   z  is in communication with the gas storing portion of the drip chamber  14 . The gas storing portion means a portion in which air exists above a liquid surface in the drip chamber  14 . Ordinarily, the drip chamber  14  is constituted by a chamber in which a liquid is stored and that is transparent and has a cylindrical shape, and a cap for closing an opening at the upper end of the chamber. In the example in  FIG. 4 , the lower end of the collection flow path  10   z  is connected to the cap. As long as the collection flow path  10   z  is in communication with the gas storing portion in the drip chamber  14 , the lower end of the collection flow path  10   z  may be connected to the chamber. The infusion set  4  is the same as the infusion set  3  according to Embodiment 3, except for the above-described configuration. 
     A description will be given of a priming method for the infusion set  4  according to Embodiment 4 that is configured as described above. 
     The first container  20   a  to the fourth container  20   d , in which the first liquid to the fourth liquid are stored, respectively, are suspended from, for example, an irrigator stand (not shown), with the ports  21   a  to  21   d  facing downward. The adapters  22   b  to  22   d  are attached to the ports  21   b  to  21   d.    
     An infusion set  4  with the first to fourth open/close valves  12   a  to  12   d , the open/close valve  12   z , and the variable valve  17  in a closed state is prepared. Also, an empty collection container  20   z  with the port  21   z  to which the adapter  22   z  is attached is prepared. The first connector  11   a  in the infusion set  4  is connected to the port  21   a  of the first container  20   a , the second to fourth connectors  11   b  to  11   d  in the infusion set  4  are connected to the adapters  22   b  to  22   d , respectively, and the connector  11   z  is connected to the adapter  22   z . The first flow path  10   a  is suspended in a substantially vertical direction due to gravity such that the first connector  11   a , the first open/close valve  12   a , the drip chamber  14 , and the variable valve  17  are arranged in this order from the upper side toward the lower side. The second to fourth containers  20   b  to  20   d  are arranged at positions higher than the first open/close valve  12   a . The downstream connector  19  is connected to the connector  32 . 
     Initially, the first flow path  10   a  is primed using the first liquid (e.g. a premedication) in the first container  20   a . That is to say, the first open/close valve  12   a  and the variable valve  17  are opened. The first liquid in the first container  20   a  flows from the first connector  11   a  into the first flow path  10   a . When the first liquid reaches the tip of the needle  31  that is provided further downstream of the downstream connector  19 , the first open/close valve  12   a  and/or the variable valve  17  are closed once. A flow path that extends from the first container  20   a  to the needle  31  through the first flow path  10   a  and the tube  30  is filled with the first liquid. 
     Next, the needle  31  is inserted into a patient&#39;s vein. 
     Next, the first open/close valve  12   a  and the variable valve  17  are opened again. A drip of the first liquid is started. The flow rate of the first liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the first liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). 
     Upon the first liquid in the first container  20   a  running out, air in the first container  20   a  flows out, following the first liquid, from the port  21   a  into the first flow path  10   a . An interface (gas-liquid interface or liquid surface) between the first liquid and the air moves down in the first flow path  10   a . When dripping of the first liquid in the drip chamber  14  ends, the first open/close valve  12   a  and the variable valve  17  are closed. The drip of the first liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the first container  20   a  is filled with the air that has flowed out of the first container  20   a , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the first liquid. 
     Next, the open/close valve  12   z  and the second open/close valve  12   b  are opened. The second liquid in the second container  20   b  flows into the second flow path  10   b . Since the variable valve  17  and the first, third, and fourth open/close valves  12   a ,  12   c , and  12   d  are closed, the second liquid moves air that has been present in the second flow path  10   b  toward the collection container  20   z  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , and the collection flow path  10   z  in this order. The second liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the second liquid has started in the drip chamber  14 , the open/close valve  12   z  is closed, and the variable valve  17  is opened. Thereafter, the second liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. The flow rate of the second liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the second liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the second flow path  10   b  before the second open/close valve  12   b  is opened is confined to the gas storing portion in the drip cylinder  14 , the collection flow path  10   z , and the collection container  20   z.    
     Upon the second liquid in the second container  20   b  running out, air in the second container  20   b  flows out, following the second liquid, from the port  21   b  into the second flow path  10   b . An interface (gas-liquid interface or liquid surface) between the second liquid and the air moves down in the second flow path  10   b . When dripping of the second liquid in the drip chamber  14  ends, the second open/close valve  12   b  and the variable valve  17  are closed. The drip of the second liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the second container  20   b  is filled with the air that has flowed out of the second container  20   b , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the second liquid. 
     Next, the open/close valve  12   z  and the third open/close valve  12   c  are opened. The third liquid in the third container  20   c  flows into the third flow path  10   c . Since the variable valve  17  and the first, second, and fourth open/close valves  12   a ,  12   b , and  12   d  are closed, the third liquid moves air that has been present in the third flow path  10   c  toward the collection container  20   z  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , and the collection flow path  10   z  in this order. The third liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the third liquid has started in the drip chamber  14 , the open/close valve  12   z  is closed, and the variable valve  17  is opened. Thereafter, the third liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. The flow rate of the third liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the third liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the third flow path  10   c  before the third open/close valve  12   c  is opened is confined to the gas storing portion in the drip cylinder  14 , the collection flow path  10   z , and the collection container  20   z.    
     Then, the fourth flow path  10   d  is primed using the fourth liquid in the fourth container  20   d , and subsequently a drip of the fourth liquid is given, in accordance with the same procedure. After the fourth liquid in the fourth container  20   d  has run out, the fourth open/close valve  12   d  and the variable valve  17  are closed. The drips of the first liquid to the fourth liquid thus end. The needle  31  is pulled out of the patient. The infusion set  4  is discarded with the first container  20   a  to the fourth container  20   d , the collection container  20   z , and the tube  30  connected thereto. 
     Similarly to Embodiment 1, with the infusion set  4  according to Embodiment 4, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed, line-by-line, after a drip of the first liquid has started and immediately before a drip of the liquids (second liquid to fourth liquids) corresponding to the respective side-injection lines starts. Furthermore, the liquids stored in the container connected to the respective side-injection lines are used as priming solutions for the side-injection lines. 
     Air that has been present in the side-injection lines (second and third flow paths  10   b  and  10   c ) before being primed is confined to the infusion set  4  and the collection container  20   z  due to priming of these side-injection lines (second and third flow paths  10   b  and  10   c ) and does not leak out to the outside. In addition, air that has flowed out, following the liquids (second and third liquids), from the containers (second and third containers  20   b  and  20   c ) to the side-injection lines (second and third flow paths  10   b  and  10   c ) is also confined to the infusion set  4  and the collection container  20   z  due to priming of other side-injection lines (third and fourth flow paths  10   c  and  10   d ) that is to be performed immediately after the outflow of the air, and does not leak out to the outside. Even if a side-injection line is primed using a hazardous medical solution, the hazardous medical solution and vapor thereof do not leak out to the outside. This is advantageous for reducing the likelihood that the operator who performs priming is exposed to the medicine. 
     Air that has been discharged from the side-injection lines due to priming is collected into the dedicated collection container  20   z , similarly to Embodiment 3. As described in Embodiment 3, in Embodiment 4 as well, the configuration of the collection container  20   z  and the collection line is not limited to that in  FIG. 4  and may be modified in any manner. 
     In the above-described priming method for the infusion set  4 , the first to fourth open/close valves  12   a  to  12   d  and the variable valve  17  are closed when dripping of the first to fourth liquids ends in the drip chamber  14 . However, in the present invention, the time when dripping of the first to fourth liquids ends in the drip chamber  14  need not accurately coincide with the time when the valves  12   a  to  12   d  and  17  are closed. The valves  12   a  to  12   d  and  17  may be closed before dripping in the drip chamber  14  ends. Specifically, the valves  12   a  to  12   d  and  17  may be closed when an interface (gas-liquid interface) between the first to fourth liquids and the following air reaches a section (branch section) of the first flow path  10   a  between the first open/close valve  12   a  and the drip chamber  14 , respectively. 
     Embodiment 4 is the same as Embodiments 1 to 3, except for the above-described configuration. The descriptions of Embodiments 1 to 3 also apply to Embodiment 4 as appropriate. 
     Embodiment 5 
     An infusion set  5  and a priming method for the infusion set  5  according to Embodiment 5 of the present invention will be described, mainly regarding differences from Embodiments 1 to 4.  FIG. 5  shows a schematic configuration of the infusion set  5 . 
     Similarly to the infusion set  2  according to Embodiment 2, the infusion set  5  includes the bypass flow path  10   g  that brings the gas storing portion of the drip chamber  14  in communication with a portion of the first flow path  10   a  on the upstream side (on the first connector  11   a  side) of the first open/close valve  12   a  or the first connector  11   a . The open/close valve (bypass flow path open/close valve)  12   g  is provided on the bypass flow path  10   g.    
     Furthermore, the infusion set  5  includes the collection container  20   z  and the collection flow path  10   z , similarly to the infusion set  3  according to Embodiment 3. The collection container  20   z  includes the port  21   z . One end of the collection flow path  10   z  is in communication with the first branching portion  18   a , and the other end is provided with a connector (collection container connector)  11   z . The connector  11   z  is connected to the port  21   z  of the collection container  20   z  via the adapter (collection container adapter)  22   z . The open/close valve (collection flow path open/close valve)  12   z  is provided on the collection flow path  10   z.    
     A description will be given of a priming method for the infusion set  5  according to Embodiment 5 that is configured as described above. 
     The first container  20   a  to the fourth container  20   d , in which the first liquid to the fourth liquid are stored, respectively, are suspended from, for example, an irrigator stand (not shown), with the ports  21   a  to  21   d  facing downward. The adapters  22   b  to  22   d  are attached to the ports  21   b  to  21   d.    
     An infusion set  5  with the first to fourth open/close valves  12   a  to  12   d , the open/close valve  12   g , the open/close valve  12   z , and the variable valve  17  in a closed state is prepared. Also, an empty collection container  20   z  with the port  21   z  to which the adapter  22   z  is attached is prepared. The first connector  11   a  in the infusion set  5  is connected to the port  21   a  of the first container  20   a , the second to fourth connectors  11   b  to  11   d  in the infusion set  5  are connected to the adapters  22   b  to  22   d , respectively, and the connector  11   z  is connected to the adapter  22   z . The first flow path  10   a  is suspended in a substantially vertical direction due to gravity such that the first connector  11   a , the first open/close valve  12   a , the drip chamber  14 , and the variable valve  17  are arranged in this order from the upper side toward the lower side. The second to fourth containers  20   b  to  20   d  are arranged at positions higher than the first open/close valve  12   a . The downstream connector  19  is connected to the connector  32 . 
     Initially, the first flow path  10   a  is primed using the first liquid (e.g. a premedication) in the first container  20   a . That is to say, the first open/close valve  12   a  and the variable valve  17  are opened. The first liquid in the first container  20   a  flows from the first connector  11   a  into the first flow path  10   a . When the first liquid reaches the tip of the needle  31  that is provided further downstream of the downstream connector  19 , the first open/close valve  12   a  and/or the variable valve  17  are closed once. A flow path that extends from the first container  20   a  to the needle  31  through the first flow path  10   a  and the tube  30  is filled with the first liquid. 
     Next, the needle  31  is inserted into a patient&#39;s vein. 
     Next, the first open/close valve  12   a  and the variable valve  17  are opened again. A drip of the first liquid is started. The flow rate of the first liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the first liquid takes a predetermined value. It is checked that the liquid surface in the liquid chamber  14  is at a predetermined height (position). 
     Upon the first liquid in the first container  20   a  running out, air in the first container  20   a  flows out, following the first liquid, from the port  21   a  into the first flow path  10   a . An interface (gas-liquid interface or liquid surface) between the first liquid and the air moves down in the first flow path  10   a . When the dripping of the first liquid in the liquid chamber  14  ends, the first open/close valve  12   a  and the variable valve  17  are closed. The drip of the first liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the first container  20   a  is filled with the air that has flowed out of the first container  20   a , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the first liquid. 
     Next, the open/close valve  12   z  and the second open/close valve  12   b  are opened. The second liquid in the second container  20   b  flows into the second flow path  10   b . Since the variable valve  17 , the first, third and fourth open/close valves  12   a ,  12   c , and  12   d , and the open/close valve  12   g  are closed, the second liquid moves air that has been present in the second flow path  10   b  toward the collection container  20   z  through the first branching portion  18   a  and the collection flow path  10   z  in this order. 
     When an interface (gas-liquid interface or liquid surface) between the air and the second liquid reaches the first branching portion  18   a , the open/close valve  12   z  is closed, and the open/close valve  12   g  is opened. The second liquid moves down the first flow path  10   a  through the first branching portion  18   a . Since the variable valve  17  is closed, the second liquid moves the air that has been present in a portion of the first flow path  10   a  from the first branching portion  18   a  to the drip chamber  14  toward the first container  20   a  through the gas storing portion of the drip chamber  14  and the bypass flow path  10   g  in this order. The second liquid flows into the drip chamber  14 , following the air. After checking that dripping of the second liquid has started in the drip chamber  14 , the open/close valve  12   g  is closed, and the variable valve  17  is opened. Thereafter, the second liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. The flow rate of the second liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the second liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the second flow path  10   b  before the second open/close valve  12   b  is opened is confined to the collection flow path  10   z , the collection container  20   z , the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , and the first container  20   a.    
     Upon the second liquid in the second container  20   b  running out, air in the second container  20   b  flows out, following the second liquid, from the port  21   b  into the second flow path  10   b . An interface (gas-liquid interface or liquid surface) between the second liquid and the air moves down in the second flow path  10   b . When the dripping of the second liquid in the drip chamber  14  ends, the second open/close valve  12   b  and the variable valve  17  are closed. The drip of the second liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the second container  20   b  is filled with the air that has flowed out of the second container  20   b , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the second liquid. 
     Next, the open/close valve  12   z  and the third open/close valve  12   c  are opened. The third liquid in the third container  20   c  flows into the third flow path  10   c . Since the variable valve  17 , the first, second, and fourth open/close valves  12   a ,  12   b , and  12   d , and the open/close valve  12   g  are closed, the third liquid moves air that has been present in the third flow path  10   c  toward the collection container  20   z  through the first branching portion  18   a  and the collection flow path  10   z  in this order. 
     When an interface (gas-liquid interface or liquid surface) between the air and the third liquid reaches the first branching portion  18   a , the open/close valve  12   z  is closed, and the open/close valve  12   g  is opened. The third liquid moves down the first flow path  10   a  through the first branching portion  18   a . Since the variable valve  17  is closed, the third liquid moves the air that has been present in a portion of the first flow path  10   a  from the first branching portion  18   a  to the drip chamber  14  toward the first container  20   a  through the gas storing portion of the drip chamber  14  and the bypass flow path  10   g  in this order. The third liquid flows into the drip chamber  14 , following the air. After checking that dripping of the third liquid has started in the drip chamber  14 , the open/close valve  12   g  is closed, and the variable valve  17  is opened. Thereafter, the third liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. The flow rate of the third liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the third liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the third flow path  10   c  before the third open/close valve  12   c  is opened is confined to the collection flow path  10   z , the collection container  20   z , the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , and the first container  20   a.    
     Then, the fourth flow path  10   d  is primed using the fourth liquid in the fourth container  20   d , and subsequently a drip of the fourth liquid is given, in accordance with the same procedure. After the fourth liquid in the fourth container  20   d  has run out, the fourth open/close valve  12   d  and the variable valve  17  are closed. The drips of the first liquid to the fourth liquid thus end. The needle  31  is pulled out of the patient. The infusion set  5  is discarded with the first container  20   a  to the fourth container  20   d , the collection container  20   z , and the tube  30  connected thereto. 
     Similarly to Embodiment 1, with the infusion set  5  according to Embodiment 5, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed, line-by-line, after a drip of the first liquid has started and immediately before a drip of the liquids (second liquid to fourth liquids) corresponding to the respective side-injection lines starts. Furthermore, the liquids stored in the container connected to the respective side-injection lines are used as priming solutions for the side-injection lines. 
     Air that has been present in the side-injection lines (second and third flow paths  10   b  and  10   c ) before being primed is confined to the infusion set  5 , the collection container  20   z , and the first container  20   a  due to priming of these side-injection lines (second and third flow paths  10   b  and  10   c ) and does not leak out to the outside. In addition, air that has flowed out, following the liquids (second and third liquids), from the containers (second and third containers  20   b  and  20   c ) to the side-injection lines (second and third flow paths  10   b  and  10   c ) is also confined to the infusion set  5 , the collection container  20   z , and the first container  20   a  due to priming of other side-injection lines (third and fourth flow paths  10   c  and  10   d ) that is to be performed immediately after the outflow of the air, and does not leak out to the outside. Even if a side-injection line is primed using a hazardous medical solution, the hazardous medical solution and vapor thereof do not leak out to the outside. This is advantageous for reducing the likelihood that the operator who performs priming is exposed to the medicine. 
     The configuration of the collection line that brings the collection container  20   z  into communication with the first branching portion  18   a  is not limited to that in  FIG. 5 , and may be modified in any manner as described in Embodiment 3. 
     In the above-described priming method for the infusion set  5 , the first to fourth open/close valves  12   a  to  12   d  and the variable valve  17  are closed when dripping of the first to fourth liquids in the drip chamber  14  ends. However, in the present invention, the time when dripping of the first to fourth liquids in the drip chamber  14  ends need not accurately coincide with the time when the valves  12   a  to  12   d  and  17  are closed. The valves  12   a  to  12   d  and  17  may be closed before dripping in the drip chamber  14  ends, specifically when an interface (gas-liquid interface) between the first to fourth liquids and air that has been present in the first to fourth containers  20   a  to  20   d  reaches a section (branch section) between the first open/close valves  12   a  and the drip chamber  14 , respectively. 
     In  FIG. 5 , the collection flow path  10   z  is connected to the first branching portion  18   a , but the present invention is not limited thereto. The collection flow path  10   z  need only be in communication with a section (branch section) of the first flow path  10   a  between the first open/close valve  12   a  and the drip chamber  14 . 
     Embodiment 5 is the same as Embodiments 1 to 4, except for the above-described configuration. The descriptions of Embodiments 1 to 4 also apply to Embodiment 5 as appropriate. 
     Embodiment 6 
     An infusion set  6  and a priming method for the infusion set  6  according to Embodiment 6 of the present invention will be described, mainly regarding differences from Embodiments 1 to 5.  FIG. 6  shows a schematic configuration of the infusion set  6 . 
     Similarly to the infusion sets  2  and  5  according to Embodiments 2 and 5, the infusion set  6  includes the bypass flow path  10   g  that brings the gas storing portion of the drip chamber  14  in communication with a portion of the first flow path  10   a  on the upstream side (on the first connector  11   a  side) of the first open/close valve  12   a  or the first connector  11   a . The open/close valve (bypass flow path open/close valve)  12   g  is provided on the bypass flow path  10   g.    
     Furthermore, the infusion set  6  includes the collection container  20   z  and the collection flow path  10   z , similarly to the infusion sets  3  to  5  according to Embodiments 3 to 5. However, in Embodiment 6, the collection flow path  10   z  branches from a portion of the bypass flow path  10   g  between the drip chamber  14  and the open/close valve  12   g . A connector  11   z  (collection container connector) is provided at a terminal of the collection flow path  10   z . The collection container  20   z  includes a port  21   z . The connector  11   z  is connected to the port  21   z  of the collection container  20   z  via the adapter (collection container adapter)  22   z . The open/close valve (collection flow path open/close valve)  12   z  is provided on the collection flow path  10   z.    
     A description will be given of a priming method for the infusion set  6  according to Embodiment 6 that is configured as described above. 
     The first container  20   a  to the fourth container  20   d , in which the first liquid to the fourth liquid are stored, respectively, are suspended from, for example, an irrigator stand (not shown), with the ports  21   a  to  21   d  facing downward. The adapters  22   b  to  22   d  are attached to the ports  21   b  to  21   d.    
     An infusion set  6  with the first to fourth open/close valves  12   a  to  12   d , the open/close valve  12   g , the open/close valve  12   z , and the variable valve  17  in a closed state is prepared. Also, an empty collection container  20   z  with the port  21   z  to which the adapter  22   z  is attached is prepared. The first connector  11   a  in the infusion set  6  is connected to the port  21   a  of the first container  20   a , the second to fourth connectors  11   b  to  11   d  in the infusion set  6  are connected to the adapters  22   b  to  22   d , respectively, and the connector  11   z  is connected to the adapter  22   z . The first flow path  10   a  is suspended in a substantially vertical direction due to gravity such that the first connector  11   a , the first open/close valve  12   a , the drip chamber  14 , and the variable valve  17  are arranged in this order from the upper side toward the lower side. The second to fourth containers  20   b  to  20   d  are arranged at positions higher than the first open/close valve  12   a . The downstream connector  19  is connected to the connector  32 . 
     Initially, the first flow path  10   a  is primed using the first liquid (e.g. a premedication) in the first container  20   a . That is to say, the first open/close valve  12   a  and the variable valve  17  are opened. The first liquid in the first container  20   a  flows from the first connector  11   a  into the first flow path  10   a . When the first liquid reaches the tip of the needle  31  that is provided further downstream of the downstream connector  19 , the first open/close valve  12   a  and/or the variable valve  17  are closed once. A flow path that extends from the first container  20   a  to the needle  31  through the first flow path  10   a  and the tube  30  is filled with the first liquid. 
     Next, the needle  31  is inserted into a patient&#39;s vein. 
     Next, the first open/close valve  12   a  and the variable valve  17  are opened again. A drip of the first liquid is started. The flow rate of the first liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the first liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). 
     Upon the first liquid in the first container  20   a  running out, air in the first container  20   a  flows out, following the first liquid, from the port  21   a  into the first flow path  10   a . An interface (gas-liquid interface or liquid surface) between the first liquid and the air moves down in the first flow path  10   a . When dripping of the first liquid in the drip chamber  14  ends, the first open/close valve  12   a  and the variable valve  17  are closed. The drip of the first liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the first container  20   a  is filled with air that has flowed out of the first container  20   a , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the first liquid. 
     Next, the open/close valve  12   z  and the second open/close valve  12   b  are opened. The second liquid in the second container  20   b  flows into the second flow path  10   b . Since the variable valve  17  and the first, third, and fourth open/close valves  12   a ,  12   c , and  12   d  and the open/close valve  12   g  are closed, the second liquid moves air that has been present in the second flow path  10   b  toward the collection container  20   z  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , the bypass flow path  10   g , and the collection flow path  10   z  in this order. The second liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the second liquid has started in the drip chamber  14 , the open/close valve  12   z  is closed, and the variable valve  17  is opened. Thereafter, the second liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. The flow rate of the second liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the second liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been in the second flow path  10   b  before the second open/close valve  12   b  is opened is confined to the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , the collection flow path  10   z , and the collection container  20   z.    
     Upon the second liquid in the second container  20   b  running out, air in the second container  20   b  flows out, following the second liquid, from the port  21   b  into the second flow path  10   b . An interface (gas-liquid interface or liquid surface) between the second liquid and the air moves down in the second flow path  10   b . When dripping of the second liquid in the drip chamber  14  ends, the second open/close valve  12   b  and the variable valve  17  are closed. The drip of the second liquid is temporarily discontinued. A portion from the gas storing portion in the drip chamber  14  to the second container  20   b  is filled with air that has flowed out of the second container  20   b , and a portion on the downstream side (on the downstream connector  19  side) of the liquid surface in the drip chamber  14  is filled with the second liquid. 
     Next, the open/close valve  12   z  and the third open/close valve  12   c  are opened. The third liquid in the third container  20   c  flows into the third flow path  10   c . Since the variable valve  17 , the first, second, and fourth open/close valves  12   a ,  12   b , and  12   d , and the open/close valve  12   g  are closed, the third liquid moves air that has been present in the third flow path  10   c  toward the collection container  20   z  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , the bypass flow path  10   g , and the collection flow path  10   z  in this order. The third liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the third liquid has started in the drip chamber  14 , the open/close valve  12   z  is closed, and the variable valve  17  is opened. Thereafter, the third liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. The flow rate of the third liquid can be checked in the drip chamber  14 . The opening of the variable valve  17  is adjusted such that the flow rate of the third liquid takes a predetermined value. It is checked that the liquid surface in the drip chamber  14  is at a predetermined height (position). Air that has been present in the third flow path  10   c  before the third open/close valve  12   c  is opened is confined to the gas storing portion of the drip chamber  14 , the bypass flow path  10   g , the collection flow path  10   z , and the collection container  20   z.    
     Then, the fourth flow path  10   d  is primed using the fourth liquid in the fourth container  20   d , and subsequently a drip of the fourth liquid is given, in accordance with the same procedure. After the fourth liquid in the fourth container  20   d  has run out, the fourth open/close valve  12   d  and the variable valve  17  are closed. The drips of the first liquid to the fourth liquid thus end. The needle  31  is pulled out of the patient. The infusion set  6  is discarded with the first container  20   a  to the fourth container  20   d , the collection container  20   z , and the tube  30  connected thereto. 
     In the above-described priming method, air that has been present in a side-injection line before priming, and air that has flowed out of a container to the side-injection line following the liquid are collected into the collection container  20   z . In this embodiment, the air can also be collected into the first container  20   a . This will be described below. 
     When dripping of the first liquid in the drip chamber  14  ends, the first open/close valve  12   a  and the variable valve  17  are closed. Next, the open/close valve  12   g  and the second open/close valve  12   b  are opened (in the above priming method, the open/close valve  12   z , rather than the open/close valve  12   g , is opened). The second liquid in the second container  20   b  flows into the second flow path  10   b . The second liquid moves air that has been present in the second flow path  10   b  toward the first container  20   a  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , and the bypass flow path  10   g  in this order. The second liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the second liquid has started in the drip chamber  14 , the open/close valve  12   g  is closed, and the variable valve  17  is opened. Thereafter, the second liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the first liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the second liquid is started. Air that has been present in the second flow path  10   b  before the second open/close valve  12   b  is opened is confined to the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , and the first container  20   a . Thereafter, when dripping of the second liquid in the drip chamber  14  ends, the second open/close valve  12   b  and the variable valve  17  are closed. 
     Next, the open/close valve  12   g  and the third open/close valve  12   c  are opened (in the above priming method, the open/close valve  12   z , rather than the open/close valve  12   g , is opened). The third liquid in the third container  20   c  flows into the third flow path  10   c . The third liquid moves air that has been present in the third flow path  10   c  toward the first container  20   a  through the first branching portion  18   a , the first flow path  10   a , the drip chamber  14 , and the bypass flow path  10   g  in this order. The third liquid flows into the drip chamber  14  through the first branching portion  18   a  and the first flow path  10   a  in this order. After checking that dripping of the third liquid has started in the drip chamber  14 , the open/close valve  12   g  is closed, and the variable valve  17  is opened. Thereafter, the third liquid moves down the first flow path  10   a , and flows toward the downstream connector  19 . Thus, the drip of the second liquid remaining in the first flow path  10   a  is resumed, and subsequently, a drip of the third liquid is started. Air that has been present in the third flow path  10   c  before the third open/close valve  12   c  is opened is confined to the gas storing portion in the drip chamber  14 , the bypass flow path  10   g , and the first container  20   a . Thereafter, when dripping of the third liquid in the drip chamber  14  ends, the third open/close valve  12   c  and the variable valve  17  are closed. 
     Next, the open/close valve  12   g  and the fourth open/close valve  12   d  may be opened to prime the fourth flow path  10   d  using the fourth liquid, in accordance with the same procedure. 
     As described above, in Embodiment 6, which one of the open/close valve  12   g  and the open/close valve  12   z  to open can be optionally selected to prime a side-injection line. Air that has been present in the side-injection line before priming and air that has flowed out of a container following the liquid, to the side-injection line is pushed out toward either the collection container  20   z  or the first container  20   a , in accordance with that selection. Which one of the collection container  20   z  and the first container  20   a  to use to collect the air can be selected for each of the side-injection lines. 
     Similarly to Embodiment 1, with the infusion set  6  according to Embodiment 6, the side-injection lines (second to fourth flow paths  10   b  to  10   d ) are primed, line-by-line, after a drip of the first liquid has started and immediately before a drip of the liquids (second liquid to fourth liquids) corresponding to the respective side-injection lines starts. Furthermore, the liquids stored in the container connected to the respective side-injection lines are used as priming solutions for the side-injection lines. 
     Air that has been present in the side-injection lines (second and third flow paths  10   b  and  10   c ) before being primed is confined to the infusion set  6  and the container  20   z  or  20   a  due to priming of these side-injection lines (second and third flow paths  10   b  and  10   c ) and does not leak out to the outside. In addition, air that has flowed out, following the liquids (second and third liquids), from the containers (second and third containers  20   b  and  20   c ) to the side-injection lines (second and third flow paths  10   b  and  10   c ) is also confined to the infusion set  6  and the container  20   z  or  20   a  due to priming of other side-injection lines (third and fourth flow paths  10   c  and  10   d ) that is to be performed immediately after the outflow of the air, and does not leak out to the outside. Even if a side-injection line is primed using a hazardous medical solution, the hazardous medical solution and vapor thereof do not leak out to the outside. This is advantageous for reducing the likelihood that the operator who performs priming is exposed to the medicine. 
     The configuration of the collection line that brings the collection container  20   z  into communication with the first branching portion  18   a  is not limited to that in  FIG. 6 , and may be modified in any manner as described in Embodiment 3. 
     In the above-described priming method for the infusion set  6 , the first to fourth open/close valves  12   a  to  12   d  and the variable valve  17  are closed when dripping of the first to fourth liquids in the drip chamber  14  ends. However, in the present invention, the time when dripping of the first to fourth liquids in the drip chamber  14  ends need not accurately coincide with the time when the valves  12   a  to  12   d  and  17  are closed. The valves  12   a  to  12   d  and  17  may be closed before dripping in the drip chamber  14  ends, specifically when an interface (gas-liquid interface) between the first to fourth liquids and air that has been present in the first to fourth containers  20   a  to  20   d  reaches a section (branch section) between the first open/close valves  12   a  and the drip chamber  14 . 
     Embodiment 6 is the same as Embodiments 1 to 5, except for the above-described configuration. The descriptions of Embodiments 1 to 5 also apply to Embodiment 6 as appropriate. 
     Embodiments 1 to 6 above are merely examples. The present invention is not limited to Embodiments 1 to 6 above, and can be modified as appropriate. 
     In Embodiments 1 to 6 above, the second flow path  10   b  is primed after all of the first liquid has flowed out of the first container  20   a , but the present invention is not limited thereto. After the entire first flow path (main line)  10   a  (preferably including the tube  30 ) from the first connector  11   a  to the downstream connector  19  has been primed with the first liquid, the second flow  10   b  can be primed even if the first liquid still remains in the first container  20   a . This can be readily done particularly in Embodiments 3 to 6 in which air that has been present in the second flow path  10   b  is collected into the dedicated collection container  20   z . In this case, if necessary, movement of the second liquid in the second flow path  10   b  may be supported by, for example, lifting the second container  20   b  to a position higher than the first container  20   a , or slightly squashing the second container  20   b.    
     In Embodiments 1 to 6 above, the second to fourth flow paths (side-injection lines)  10   b  to  10   d  are in communication with the first flow path (main line)  10   a  at the shared first branching portion  18   a . This configuration is advantageous for simplifying discharge of air when priming the second to fourth flow paths  10   b  to  10   d , and for reducing mixture of different liquids. However, the present invention is not limited thereto. For example, a configuration may alternatively be employed in which the second to fourth flow paths  10   b  to  10   d  do not have a shared flow path portion, and are in communication with the first flow path  10   a  at different branching portions. 
     The number of side-injection lines included in each infusion set does not need to be three (namely, the second to fourth flow paths  10   b  to  10   d ) as in Embodiments 1 to 6 described above, and need only be at least one. The infusion set can exhibit the above-described effects of the present invention if the infusion set includes at least one side-injection line that branches from the main line (the first flow path  10   a ). Preferably, the number of side-injection lines is two or more. 
     The infusion set according to the present invention may be configured such that side-injection lines can be additionally provided as necessary. For example, in the infusion set  1  according to Embodiment 1, a branching portion similar to the branching portions  18   b  and  18   c  is provided on the fourth flow path  10   d , and a female connector is provided at a terminal of a branch flow path that branches from this branching portion. A three-way stopcock is provided at this branching portion, or an open/close valve similar to the open/close valves  12   b  and  12   c  is provided on the branch flow path. An additional side-injection line may be configured to be similar to the second to fourth flow paths  10   b  to  10   d . A connector capable of being connected to an additional container in which a liquid is stored is provided at an upstream end of the additional side-injection line. A male connector that can be attached to and detached from the aforementioned female connector is provided at a downstream end of the additional side-injection line. By connecting the additional side-injection line to the female connector, a drip of the liquid in the additional container can be given via the additional side-injection line. The additional side-injection line can be primed similarly to priming of the second to fourth flow paths  10   b  to  10   d . The female connector for connecting the additional side-injection line is preferably a female connector that includes a self-closing valve (which may be called a septum) (e.g. see Patent Document 4). The male connector provided at the downstream end of the additional side-injection line is preferably a self-closing male connector that includes a compressible and deformable cover for covering a male member (e.g. see a later-described connector  11  in  FIG. 7  and Patent Document 5). The infusion sets  2  to  6  according to Embodiments 2 to 6 may also be configured such that side-injection lines can be additionally provided. 
     In the infusion sets  1  to  6  according to Embodiments 1 to 6, a three-way stopcock may be provided at the branching portion  18   c . For example, when the fourth container  20   d  is not used, the three-way stopcock at the branching portion  18   c  is operated to disconnect the fourth flow path  10   d  from the branching portion  10   x . Thus, the first to third containers  20   a  to  20   c  can be sequentially primed and a drip of the liquids therein can be given with the fourth connector  11   d  not connected to the fourth container  20   d . A three-way stopcock may also be similarly provided at the branching portion  18   b.    
     The infusion set may further be provided with any other members. For example, a filter for filtering a liquid, a mixture injection port for mixing a medical solution or the like with a liquid, or the like may be provided in the main line and/or the side-injection lines. 
     A liquid may be moved in the infusion set by using a pump (e.g. an infusion pump that is commonly used in infusion), rather than using gravity. There are cases where a pump has the functionality of the variable valve  17 . In such cases, the variable valve  17  can be omitted and replaced with the pump. 
     The configuration of the connectors connected to the containers for storing liquids or air is not limited to a puncture needle (first connector  11   a ) and a lever lock connector (second to fourth connectors  11   b  to  11   d , collection container connector  11   z ), and may be any configuration. All of the connectors may have the same configuration, or some of the connectors may have a configuration different from the other connectors. The connector provided on the main line may be the same as connectors provided on the side-injection lines. For example, the first connector  11   a  may be the same lever lock connector as the second to fourth connectors  11   b  to  11   d , and may be connected to the port  21   a  of the first container  20   a  via an adapter that is configured similarly to the adapters  22   b  to  22   d.    
     Each of the lever lock connectors may be a self-closing connector  11  such as one shown in  FIG. 7 . This connector  11  includes a cover  70  for covering a hole  52  provided near a leading end of a bar-shaped male member  50 . The male member  50  has a flow path  51  through which a liquid flows that is formed in the longitudinal direction of the male member  50 . The hole  52  is in communication with the flow path  51 . A cylindrical hood  55  is disposed coaxially with the male member  50  so as to surround the male member  50 . The cover  70  is made of a soft material (so-called elastomer) that has rubber elasticity (or plasticity). The material of the cover  70  is not limited, but may be, for example, isoprene rubber, silicone rubber, butyl rubber, thermoplastic elastomer, or the like. The cover  70  has, as a whole, a hollow cylindrical shape that is closed at the leading end side. A linear slit  72  with a “− (minus)” shape as viewed from above is formed at the leading end of the cover  70 . Upon the connector  11  being connected to a mixture injection port of the adapter, the cover  70  is compressed and deformed in the longitudinal direction of the male member  50 , and the male member  50  penetrates the slit  72  and is inserted into the mixture injection port. Upon the connector  11  being separated from the mixture injection port, the cover  70  is immediately restored to its initial shape, and the hole  52  in the male member  50  is accommodated in the cover  70 . When the connector  11  is connected to the mixture injection port, the mixture injection port is inserted into the hood  55 , and a claw  62 , which is provided at a leading end of the lock lever  60 , engages with the mixture injection port. An operation lever  65  extends from the lock lever  60 . If a force that acts radially inward is applied to the operation lever  65 , the claw  62  is displaced in a direction moving away from the male member  50 . If a force that acts radially inward is unintentionally applied to the operation lever  65  with the connector  11  connected to the mixture injection port, there may be cases where the claw  62  is disengaged from the mixture injection port, and the connector  11  is separated from the mixture injection port. In such cases, the cover  70  immediately extends and closes the hole  52 . Therefore, the liquid is less likely to leak out from the hole  52 . If a connector (second and third connector  11   b  and  11   c  in Embodiments 1 to 6 above) connected to a container (second and third containers  20   b  and  20   c  in Embodiment 1 to 6 above) in which a hazardous medical solution that contains an anti-cancer agent is stored is the self-closing connector  11  shown in  FIG. 7 , even if the mixture injection port is unintentionally separated from the connector, the likelihood that the hazardous medical solution leaks out to the outside can be reduced. This is advantageous for preventing the operator from being exposed to the medicine during priming. In Embodiments 3 to 6, the connector  11   z  (see  FIGS. 3 to 6 ) may be the self-closing connector  11  shown in  FIG. 7 . In this case, when the connector  11   z  is unintentionally separated from the mixture injection port of the adapter  22   z , the likelihood that the gas in the collection flow path  10   z  leaks out to the outside can be reduced. This is also advantageous for preventing the operator from being exposed to the medicine during priming. 
     The containers for storing liquids may have any configuration. The containers may be infusion bags formed by adhering soft sheets, or may be bottles that are made of a hard material and are not substantially deformed. The ports of the containers are not limited to those sealed with rubber plugs. The configuration of the adapters that are interposed between the ports and the connectors in the infusion set is not limited to those described in the above-described embodiments either, and may also be any other configuration. The connectors may be directly connected to the ports without using the adapters. 
     Any type of liquid may be administered using the infusion apparatus according to the present invention. A hazardous medical solution that contains a hazardous medicine, such as an anti-cancer agent, may be administered, or a liquid that contains a nutrient, an electrolyte, or the like and poses no risk if a person is exposed thereto may be administered. 
     INDUSTRIAL APPLICABILITY 
     The method for priming an infusion set according to the present invention can be favorably used in the medical field in the case of administering a plurality of types of liquids to a patient. In particular, the infusion apparatus according to the present invention is preferable in the case of administering a hazardous medical solution, such as an anti-cancer agent, to which an operator may be exposed. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
         
           
               1  to  6  Infusion set 
               10   a  to  10   d  Flow path 
               10   g  Bypass flow path 
               10   z  Collection flow path 
               11 ,  11   a  to  11   e  Connector 
               11   z  Collection container connector 
               12   a  to  12   d  Open/close valve 
               12   g  Bypass flow path open/close valve 
               12   z  Collection flow path open/close valve 
               14  Drip chamber 
               17  Variable valve 
               19  Downstream connector 
               20   a  to  20   d  Container 
               20   z  Collection container 
               50  Male member 
               51  Flow path in male member 
               52  Lateral hole in male member 
               60  Lock lever 
               70  Cover