Abstract:
An improved device for simple and reliable control of flow through a medical infusion line, one end of the medical infusion line having a fluid conveying pump provided on it and the other end assigned to a patient, the infusion line forming a main flow path from the fluid conveying pump to the patient-side end. Fluid is conveyed along the main flow path through the infusion line by means of the fluid conveying pump. At least a part of the fluid is introduced, along a measurement flow path branching off from the main flow path at a branching point, from the infusion line into a measurement reservoir connected to the infusion line. The infusion line includes a fluid restrictor between the fluid conveying pump and the branching point, and the main flow path as viewed in direction of the flow is interrupted after the branching point of the measurement flow path for filling the measurement reservoir by the pressure of the fluid conveying pump. The fluid in the measurement reservoir is detected.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. national phase application of PCT International Application No. PCT/EP2015/050899 filed Jan. 19, 2015, which claims priority to German Patent Application No. DE 10 2014 201 258.9 filed Jan. 23, 2014, the contents of each application being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to a method and a device for controlling the flow through a medical infusion line, wherein one end of the medical infusion line has a fluid conveying pump provided on it and the other end thereof is assigned to a patient, the infusion line forming a main flow path from said fluid conveying pump to the patient-side end. 
       BACKGROUND OF THE INVENTION 
       [0003]    Such infusion lines are used for continuous administration of a medicament in fluid form to a patient. For instance, medicaments are administered continuously in small doses. In such cases, the fluid will be conveyed in extremely low flow rates in the range from 0.5 to 500 ml per hour. If the pump should happen to fail or the conveyance of fluid should be impeded for some other reason, this can be detected only at an advanced point in the infusion period. Particularly in case of low flow rates, a weight or volume reduction of the liquid reservoir of the pump has been barely visible and has not been measurable while keeping the resultant expenditure on a practicable level. Thus, the need exists to be able to detect in a fast and simple manner whether fluid is being conveyed through the infusion line. 
         [0004]    Measuring methods known as of yet are based on the principal concept of measuring the throughflow rate within the flow. In view of the low flow rates existing in infusion therapy or in analgesics infusion, those mechanical approaches wherein the flow rate is determined with the aid of component parts being mechanically moved by the flow, are not eligible. Such flow rates are not sufficient for causing a movement of mechanical parts. Instead, the mechanical parts will be bypassed by the fluid flow without effecting a pulse transmission that would generate a mechanical movement. As an alternative, electronic approaches are used wherein the throughflow of the fluid is detected with the aid of electronic sensors. These electronic approaches on the one hand are expensive and, on the other hand, will require an external energy source. An elastomeric infusion pump, however, should be operable independently of external energy sources. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the invention to render possible a technically simple and reliable control of the throughflow in a medical infusion line. 
         [0006]    The device according to aspects of the invention is defined by each of the independent claims. 
         [0007]    Through the infusion catheter, the main flow path leads from the fluid conveying pump to the patient-side end. Arranged on the patient-side end is a connector serving for connection with the patient or with components inserted into the patient. Thus, under the technical aspect, the patent end is to be considered as a connection site of the patient. While the previously known throughflow control methods involved the necessity to perform the flow detection at a site within the flow passing through the main flow path, the invention relates to the idea to redirect the fluid flow into a separate measurement reservoir, wherein the main flow path is provided with a flow restrictor arranged before or after the measurement flow path when viewed in the direction of the patient-side end. In this situation, the fluid conveying pump is continued to be operated in an unchanged manner, and the entire energy of the fluid flow can be used for control of the throughflow. First, in the process, the fluid which during operation of the pump is flowing from the main flow path into the measurement reservoir can be considered as an indicator confirming the general operativeness of the pump. 
         [0008]    For control of the throughflow, the main flow path will be interrupted, wherein two variants can be envisioned: 
         [0009]    As a first variant, the main flow path can be interrupted between the fluid conveying pump and the branching point of the measurement flow path from the main flow path. Thus, in this case, the main flow path will be interrupted in flow direction before the measurement reservoir, and the fluid conveying pump will not convey further fluid into the measurement reservoir and toward the patient-side end. After such an interruption of the main flow path, the fluid in the measurement reservoir will be monitored. If fluid does flow out, the infusion line is open to flow, and the throughflow to the patient is guaranteed. If no fluid flows out from the measurement reservoir, this is an indicator signaling that the infusion line in the direction of the patient-side end and/or the throughflow to the patient is interrupted or impaired. In this first variant, a fluid restrictor is provided in the infusion line along the main flow path between the branching point of the measurement flow path and the patient-side end. This variant is known from the state of the art and does not form a part of the invention. 
         [0010]    In a variant according to aspects of the invention, the main flow path will be interrupted between the branching point of the measurement flow path and the patient-side end, i.e. behind the branching point of the measurement flow path and the measurement reservoir as viewed in the flow direction. In this variant, a flow restrictor is arranged in the infusion line along the main flow path between the fluid conveying pump and the branching point of the measurement flow path. Thus, the flow restrictor is here arranged, as viewed in flow direction, before the branching point of the measurement flow path and the measurement reservoir. Upon interruption of the main flow path behind the branching point of the measurement flow path as viewed in flow direction, the fluid conveyed by the infusion line will flow completely into the measurement reservoir. In this situation, the quantity of the inflowing fluid will be monitored and serves as an indicator of the operativeness of the fluid conveying pump or the openness to flow of the infusion line and respectively of the main flow path between the pump and the measurement reservoir. 
         [0011]    A flow restrictor as mentioned in the present context is generally to be understood as a flow resistor for reducing the flow. The flow resistor can be realized as a separate component or by a suitable cross section of the infusion line. 
         [0012]    After the throughflow and the operativeness of the infusion line assembly have been verified with the fluid in the measurement reservoir, the fluid path to the patient will be opened again. Thereupon, the fluid collected in the measurement reservoir will flow out of the measurement reservoir and will be supplied to the patient via the main flow path. Thus, the throughflow measurement will not cause a loss of fluid. 
         [0013]    In the process, the fluid received in the separate measurement reservoir can be used for wetting a prism so as to change the light refraction of the prism. For instance, a colored layer can be provided under the prism, which layer will be visible only if the surface of the prism has been wetted with fluid, whereas, in a dry environment, the path of the light rays within the prism will prevent the visibility of said colored layer. 
         [0014]    A further principle for detection of fluid within the measurement reservoir can consist in providing a piston in the measurement reservoir which, under the effect of the inflowing fluid, will—against the force of a spring—be displaced in a manner visible from the outside. In this case, the fluid pumped into the measurement reservoir by the fluid conveying pump will displace the piston. The displacement or deflection of the piston can be rendered visible in different manners. For instance, the piston itself can be visible or be designed to shift an indicator element along a scale. 
         [0015]    A further alternative for detection of fluid within the measurement reservoir can reside in a visible change of shape of the measurement reservoir in dependence on the quantity of liquid in the reservoir. For instance, the measurement reservoir can be realized as a balloon adapted to expand depending on the quantity of liquid. There can also be conceived a manometer, a (miniature) bellows or an elastic tube which in the empty state is curved and in the filled state is stretched. Further, for each type of measurement reservoir, it shall be envisioned to provide a pointer which, via a leverage effect, will enhance the display. 
         [0016]    Particularly, the inventive device for flow control can be a part of a PCA (Patient Controlled Analgesia) device and/or be used in connection with a flow selector. 
         [0017]    The fluid pump can be an elastomeric pump, a spring pump, a vacuum pump or a syringe pump. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    The invention is best understood from the following detailed description when read in connection with the accompanying drawings. Included in the drawings are the following figures: 
           [0019]      FIG. 1  is a view of an embodiment in a first operating state in accordance with the prior art, 
           [0020]      FIG. 2  is a view of the embodiment of  FIG. 1  in a second operating state in accordance with the prior art, 
           [0021]      FIG. 3  is a view of an exemplary embodiment of the invention in a first operating state, 
           [0022]      FIG. 4  is a view of the exemplary embodiment of  FIG. 3  in a second operating state, 
           [0023]      FIG. 5  is a view of a further exemplary embodiment which is not part of the invention, in a first operating state in accordance with the prior art, 
           [0024]      FIG. 6  is a view of the embodiment of  FIG. 5  in a second operating state in accordance with the prior art, 
           [0025]      FIG. 7  is a view of another exemplary embodiment of the invention in a first operating state, 
           [0026]      FIG. 8  is a view of the exemplary embodiment of  FIG. 7  in a second operating state, 
           [0027]      FIG. 9  is a view of a detail of a further exemplary embodiment, 
           [0028]      FIG. 10  is a view of the exemplary embodiment according to  FIG. 9  in a different operating state, 
           [0029]      FIG. 11  is a view of a detail of a further exemplary embodiment, 
           [0030]      FIG. 12  is a view of a detail of a further exemplary embodiment, 
           [0031]      FIG. 13  is a view of a detail of a further exemplary embodiment, 
           [0032]      FIG. 14  is a view of a detail of a further exemplary embodiment, 
           [0033]      FIG. 15  is a view of the exemplary embodiment according to  FIG. 14  in a different operating state, 
           [0034]      FIG. 16  is a view of a detail of a further exemplary embodiment, 
           [0035]      FIG. 17  is a view of the exemplary embodiment according to  FIG. 16  in a different operating state, 
           [0036]      FIG. 18  is a view of a detail of a further exemplary embodiment, and 
           [0037]      FIG. 19  is a view of the exemplary embodiment according to  FIG. 18  in a different operating state. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    All exemplary embodiments are related to the principle of an infusion line assembly consisting of an infusion line  12 , a fluid conveying pump  14  and a device  16  for controlling the throughflow through said infusion line  12 . The infusion line  12  has two ends  18 ,  20 , the first end  18  among them being connected to said fluid conveying pump  14  and the second end  20  being assigned to a patient. The second end  20  is assigned to a patient in the sense that it comprises a connector  22  which is connectible to the patient or to a catheter inserted into the patient. 
         [0039]    Infusion line  12  comprises a main flow path  24  extending through the infusion line from said one end  18  thereof to said other end  20  so that fluid can be conveyed along said path from pump  14  to connector  22 . 
         [0040]    Infusion line  12  is provided with a branching point  26  connected to a measurement reservoir  28 . Said branching point  26  and said measurement reservoir  28  form said device  16  for throughflow control. In this arrangement, the branching point  26  can be realized as an integral part of infusion line  12  or be provided as a component connectible to infusion line  12  at a later time. 
         [0041]    Branching point  26  forms a measurement flow path  30  branching off from said main flow path  24  and entering into the measurement reservoir  28 . 
         [0042]    In the embodiment according to  FIG. 1 , the measurement reservoir  28  includes, in its interior, a piston  34  which is displaceable against the force of a spring  32  in such a manner that the fluid flowing along said measurement flow path  30  will displace the piston  34  within the measurement reservoir  28  against the spring force. The displacement of piston  34  is indicated on a scale  36 . Between the fluid pump  14  and branching point  26 , infusion line  12  can be clamped shut with a clamp  41  so as to interrupt the main flow path  24 . Between branching point  26  and patient connector  22 , infusion line  12  comprises a flow restrictor  40 . 
         [0043]    In the operating state according to  FIG. 1 , the clamp  41  is opened and the main flow path  24  is not interrupted. The fluid pump  14  will convey the fluid, represented by dots, along the main flow path  24  via infusion line  12  to the patient-side end  20  of the latter and via branching point  26  along the measurement flow path  30  into the measurement reservoir  28 . In the process, the fluid pump  14  will build up, in measurement reservoir  28 , a pressure acting on piston  34 , which pressure will act against the spring force of spring  32  and will displace the piston  34 . The displacement of piston  34  as visible on scale  36  can serve as an indicator of the operation or the functional operability of the fluid pump  14 . 
         [0044]    For examining whether the infusion line  12 , the fluid restrictor  40 , the patient connector  22  and possible additional components farther downstream, such as e.g. filters, catheters etc. are unobstructed and functional, said clamp  41  will be briefly closed. For this purpose, clamp  41  should not be a locking clamp but should automatically open when released. Alternatively, the infusion line  12  can also be briefly pressed together or kinked by hand for interrupting the fluid flow. During the clamped state of infusion line  12 , operation of fluid pump  14  will be continued. However, no further fluid will be conveyed into the measurement reservoir  28 , and the fluid pressure generated by fluid pump  14  will not act on the piston  34  anymore. The spring force will displace the piston, and the fluid will be conveyed from the measurement reservoir  28  and into the infusion line  12  in the direction of patient-side end  20  when the infusion line  12  and all following components are open to flow. The term “open to flow” is meant in the sense that the fluid is being conveyed and that the fluid flow is not blocked or reduced by damage, kinking or obstruction. In this regard, the displacement of piston  34  serves as a measure of the openness to flow of infusion line  12  along main flow path  24  in the direction of the patient. If the infusion line  12  or one of the components connected to it is damaged and blocks the fluid flow, the piston  34  will press out less or no fluid from measurement reservoir  28 . The displacement of piston  34  will then be different from the one in case of an infusion line  12  that is open to flow. 
         [0045]    The embodiment according to  FIGS. 3 and 4  is different from the embodiment according to  FIGS. 1 and 2  only by the arrangement of clamp  41  and flow restrictor  40 . In the second exemplary embodiment, flow restrictor  40  is arranged between fluid pump  14  and branching point  26 . Clamp  41  serves for interrupting the main flow path  24  in the area between branching point  26  and patient end  20 . In the non-clamped state according to  FIG. 3 , the operating state will then correspond to that according to  FIG. 1 . The clamp serves, and can be considered as, a control unit on the one hand and as a simulation of a blockade on the other hand. 
         [0046]    The second operating state according to  FIG. 4 , however, is different from the second operating state of the first embodiment according to  FIG. 2 . In  FIG. 4 , when infusion line  12  is in its clamped-shut condition, fluid pump  14  will continue to be operated, and fluid will continue to be conveyed into measurement reservoir  28 . Since no fluid can flow anymore in the direction of patient-side end  20 , fluid pump  14  will build up an ever more increasing fluid pressure within measurement reservoir  28 . The resulting displacement of piston  34  will then serve as an indicator of the operability of fluid pump  14  and the openness to flow of infusion line  12  in the area between fluid pump  14  and measurement reservoir  28 . Also in  FIG. 4 , clamp  41  (as a control unit) will be closed only briefly so that the interruption of the infusion will be short and the overall quantity of the fluid administered to the patient will not decrease. In case of a blockade (on the patient), this unit will function “automatically” (the liquid column would rise). 
         [0047]    The third embodiment according to  FIGS. 5 and 6  corresponds to the first exemplary embodiment according to  FIGS. 1 and 2  except for the device  16  for control of the throughflow. Correspondingly, the fourth exemplary embodiment according to  FIGS. 7 and 8  is different from the second exemplary embodiment according to  FIGS. 3 and 4  only by the device  16 . In the exemplary embodiment according to  FIGS. 3 and 4 , the devices  16  for controlling the throughflow are identical. The difference from the exemplary embodiment according to  FIGS. 1 and 2  resides in that the measurement reservoir does not comprise a piston  34  displaceable against the force of a spring  32  but instead comprises a prism  50  on whose bottom a colored layer  52  e.g. in red color is provided. Said prism is light-transmissive and is designed to the effect that, in the state illustrated in  FIG. 6 , it will reflect light completely when in a dry environment so that the colored layer  52  will not be visible. In the states shown in  FIGS. 5 and 8 , the prism  52  is wetted by the fluid while no total reflection will occur anymore and the colored layer  52  will be visible. This has the consequence that, in case of a functioning, sufficient throughflow, the device  16 —due to the special refraction conditions of prism  50 —will present the colored layer  52  as an indicator confirming a correct throughflow. If, however, the measurement reservoir  28 , as e.g. in  FIG. 6  or in case of a defect fluid conveying pump, does not contain fluid and the prism  50  is surrounded by a dry environment, the colored layer  52  will not be presented. 
         [0048]      FIGS. 9-15  illustrate various exemplary embodiments of such a prism  50 .  FIGS. 9-13  herein show two-part prisms  50  comprising an upper part  50   a  and a lower part  50   b.  In  FIGS. 9, 11 and 12  the bottom of the lower part  50   b  of the prism is provided with a colored layer  52 . In  FIG. 13 , there does not exist a separate colored layer but, instead, the lower part  50   b  of the prism is colored.  FIGS. 9, 11, 12 and 13  illustrate the path of rays of the light through the prism  50  when the prism has been wetted with fluid, i.e. in the operating states shown to  FIGS. 5 to 8 .  FIG. 10  illustrates the upper part  50   a  of the prism according to the exemplary embodiments shown in  FIG. 9  in a dry environment in which the light is reflected totally and the colored layer  52  is not visible. This is the case in the operating state according to  FIG. 6 . 
         [0049]      FIGS. 14 and 15  show an exemplary embodiment of a two-part prism  50  whose two parts together with the colored bottom  52  together enclose a throughflow channel  51  for the fluid. Herein, the prism is arranged in the measurement reservoir  28  in a manner causing the fluid contained in measurement reservoir  28  to flow into the channel  51 .  FIG. 14  shows the path of rays in the operating state according to  FIGS. 6 and 7 , i.e. in a dry environment. In this situation, prism  50  will reflect the incident light onto a lateral colored layer  53  e.g. in red color. Thus, in a dry environment according to  FIG. 6 , the red color is visible.  FIG. 15  shows the path of rays in the operating states according to  FIGS. 5 and 8  in which the channel  51  has fluid streaming through it. This will result in the path of rays shown in  FIG. 15  wherein light is reflected on the colored bottom  52 . In this situation, the colored layer  52  is kept in green color so that the prism in  FIG. 15  will present the green color. 
         [0050]      FIGS. 16 and 17  show an exemplary embodiment of a two-part prism  50  comprising two part-prisms  50   a  and  50   b.  All part-prisms  50   a,    50   b  are rectangular, i.e. they are provided with a rectangular tip  54 . Between the two prisms  50   a,    50   b,  a channel  51  is provided for throughflow of the fluid. At the lateral edges, a colored layer  53  in a first color (e.g. red) is provided which, in the dry state shown in  FIG. 16 , will reflect the light. Thus, in a dry environment, the red colored layer is visible.  FIG. 17  shows the path of rays when fluid is present in channel  51 . In this case, the incident light is reflected onto a lower colored layer  52  having a second color differing from the first color (green). Thus, when fluid is present in channel  51 , the green colored layer is visible. 
         [0051]    The exemplary embodiment according to  FIGS. 18 and 19  is different from the exemplary embodiment according to  FIGS. 16 and 17  only in that no lower colored layer  52  is provided under the second part-prism  50   b  but, instead, the second prism  50   b  is colored in said second color differing from the first color (green). In the dry state without fluid in channel  51  as depicted in  FIG. 18 , the light will be reflected by the red colored layer  53  as shown in  FIG. 16 . In the state shown in  FIG. 19 , with channel  51  having a flow passing through it, the light will be reflected by the green part-prism  50 , and the green coloring of prism  50   b  will be visible.