WO2020124100A1

WO2020124100A1 - A flow control system comprising a gravity feed infusion device for intravenous fluids and method of its operation

Info

Publication number: WO2020124100A1
Application number: PCT/AP2018/000002
Authority: WO
Inventors: Mathew Ocheng; Hudson KAGODA; Ivan KALULE
Original assignee: NGAJU MAKOBORE, Philippa
Priority date: 2018-12-17
Filing date: 2018-12-17
Publication date: 2020-06-25
Also published as: WO2020124100A8

Abstract

The invention relates to a flow controlling system for a gravity feed infusion device for intravenous fluids, wherein the system comprises: a sensor configured to be attached to a drip chamber of the infusion device and configured to register any drops generated in the drip chamber. The system also consists of an infusion tube restrictor for controlling the size of a restriction of an infusion tube; a controller configured to control the' infusion tube restrictor, wherein the controller is configured to provide for a series of consecutive timeslots, to set open the tube restrictor in a first timeslot, to calculate the cumulative number of drops registered by the sensor and to close the tube restrictor in this timeslot. Furthermore, the system is configured to set open again the tube restrictor in a second timeslot, wherein the controller is configured to use the number of registered drops in the first timeslot as a parameter for controlling the length of the second timeslot or the number of desired drops in the second time slot.

Description

Background and Summary of the Invention The invention relates to a flow controlling system and device for gravity feed infusion devices for intravenous fluid administration. More specifically the invention relates to a relatively simple and sturdy designed flow regulator for infuses

In the art, these kinds of systems are described in numerous publications. The international patent

application WO2016/160527 for instance describes an

intravenous gravity feed delivery system with a drip unit.

In this document, the number of drops in a time slot is not used as a controlling parameter for further time slots lengths or for a set number of drops in further time slots.

In the American patent publication US4504263 a flow rate monitor with optical sensing chamber is described. The control is steering on a drop to drop basis, wherein the volume of a drop determines the time before a consecutive drop is allowed to form. In this document, the diameter of the drops and the number of the drops is used to regulate the time period between individual consecutive drops. The amount of drops, administered in a certain tiifte slot ..is not used for controlling further time slots lengths or for a set number of drops in further time slots.

However, the above described devices and other devices in the art are generally complex and require well trained staff to operate. In hospitals with less budgets and/or high number of patients per hospital staff members, gravity feed infusion devices are used with a manual

regulator. These gravity feed infusion devices rely on hospital staff members to operate and regulate infusion therapies and do not provide critical feedback during infusion administration. This may lead to relatively high errors in dosing regimes, which can cause life threatening situations to the patients in question.

~ There exists a need for a relatively simple solution that can increase the accuracy of dosing, while keeping the costs relatively low.

Accordingly, it is an object of the invention to mitigate or solve the above described and/or other problems of flow controlling systems for gravity feed infusion in the art, while maintaining and/or improving the advantages thereof.

More specifically the object of the invention can be seen in providing a less complex, relatively low-cost solution for relatively high accuracy controlling of gravity feed infusion flow rates.

These and/or other objects are reached by a flow controlling system for a gravity feed infusion device for intravenous fluids, wherein the system comprises: a sensor configured to be attached to a drip chamber of the infusion device and configured to register any drops generated in the drip chamber; an infusion tube restrictor for controlling the size of a restriction of an infusion tube; a controller configured to control the infusion tube restrictor, wherein the controller is configured to: provide for a series of consecutive timeslots, set open the tube restrictor in a first timeslot, calculate the cumulative number of drops registered by the sensor, close the tube restrictor in this timeslot, set open again the tube restrictor in a second timeslot and, wherein the controller is configured to use the number of registered drops in the first timeslot as a parameter for controlling the length of the second timeslot or the number of desired drops in the second time slot. By controlling the length of the consecutive time slots, based on the numbers of drops registered in the previous time slots, an elegant control can be performed, where the restrictor or regulator needs only an open/close signal. This set up can thus be manufactured and maintained in an efficient way. By this controlling algorithm, the lengths of any further consecutive timeslots can be

determined by the number of registered drops in a previous timeslot. For e.g. storing various data, data storage can be provided in the controller. The data storage herein can provide for storing the number of timeslots, the number of drops in each timeslot, the total number of drops, a

calculated dosage rate, a cumulative calculated dosing volume and/or other relevant administration data.

Since various infusion devices are commercially available, each with its own characteristics, the length of the timeslots can be corrected by a compensation factor.

This compensation factor may compensate for increasing or decreasing drop sizes at e.g. higher flow rates and may be type specific for the various available infusion devices.

The compensation factor may be a staged value, being set at specific drop rate intervals, e.g. an increasing correction for a higher flow rate interval. Alternatively, the compensation factor can be the result of a calculated function of _the drop rate, derived from e.g. experimental . data. By applying compensation factors, the drop size variations at the various flow rates can be sufficiently compensated, such that the actual dosing flow rate and the cumulative dosing volume are within an acceptable error range .

The system may comprise a data entry and capturing interface for registration of the type of infuse which is used in the device, and a memory comprising a data^’ set of compensation factors, related to the various types of infuses used, wherein, on the basis of the type of infuse, the relevant compensation factor is chosen. The type of infusion device may be demanded by the controller via a user interface on the controller. The type may be presented as a data entry, to be provided by the relevant operator or care giver working with the infusion flow controlling system.

Alternatively, the type of infusion device applied may be registered by shape characteristics of e.g. the drip chamber or by a tag e.g. the drip chamber, such that the sensor can read, which type of infusion device is applied, and provide this information to the controller, such that the appropriate type specific compensation factor lor algorithm is chosen.

The tube restrictor may comprise a housing, wherein the housing can comprise two compartments, one compartment facing to a first side of the housing and one compartment facing to a second side of the housing, opposing and facing away from the first side. By this arrangement, the actuator actuating the restrictor can be accessed from one lateral side Of the restrictor, while the infusion tube can be inserted from a second lateral side of the restrictor. By this arrangement, the actuator and the infusion tube are shielded from each other, such that any risk of

contamination of the infusion liquid is further reduced. Similarly, the risk of infusion liquid accessing the actuator is reduced by this arrangement as well. In this arrangement, the first compartment can comprise a space for an actuator, which actuator comprises a plunger, and the second compartment can comprise an infusion tube engaging space. As indicated herein above, the first and second compartment can thus be separated by a wall, which can comprise an opening for allowing the plunger to move in and reach through, from the first compartment into the second compartment.

The housing of the restrictor can comprise a cover for covering the first compartment. This can further reduce the ingress of material in the actuator and the plunger guiding space, such that proper operation can better be secured.

The plunger can be configured to pinch the tube in a manner that is configured to restrict and/or close off the fluid flow inside the tube, by this pinching action, the actual flow through ^'the infusion tube can be stopped or started. The tube restrictor can comprise a mounting clamp for mounting the restrictor on an infusion bag holder.

The system can comprise a sensor system for a drip chamber, wherein the sensor system may comprise a housing, the housing comprising a first drip chamber engaging part, said drip chamber engaging part having drip chamber

receiving space, extending over the full height of the engaging part from a top face to a bottom face, said drip chamber engaging part comprising an tube entry slot,

similarly extending over the full height of the engaging part from a top face to a bottom face, which entry slot is narrow in relation to the diameter of the drip chamber receiving space and is configured to allow a tube of an gravity feed infusion set to fit though, yet is dimensioned to be too narrow to allow the drip chamber to fit through.

By this specific arrangement the drip chamber of an infusion device can be locked up, such that the drip chamber can be prevented from moving relative to the light sensor within the sensor system. This can enhance the accuracy of the sensing of drops.

In this set up of the sensor system, the housing of the sensor system can comprise a second part, which second part can be attached to the first part, the second part comprising a drip chamber top engaging part at a first side, which first side is configured to close on the top face of the first drip chamber engaging part of the housing in an assembled state, which opening is narrowing towards a top side, which top side is facing away from the first side, the opening being configured to lock-in a drip chamber, said second part further comprising an entry slot, of which entry slot, an opening is facing sideward and is configured to allow a tube of an gravity feed infusion set to fit though, yet is dimensioned to be too harrow to allow a drip chamber and/or the top of a drip chamber to fit through. For the actual sensing, the first housing part may comprise a light source and a sensor, the sensor being configured to register any drops in the drip chamber.

The invention further relates to a method of controlling a flowrate from a gravity feed infusion system, comprising the following steps, to be executed in any suitable order: providing a storage for a liquid, with a tube for allowing gravity feed flow, providing a drip chamber, providing a drop registering sensor on the drip chamber, providing a controller, providing an actuator operating a flow restrictor, having the controller

controlling in a series of consecutive timeslots the position of the actuator of the flow restrictor, having the controller controlling the length of a consecutive or later timeslot or the desired number of drops in a consecutive or later timeslot, on the basis of the number of drops

registered and/or calculated in the or any previous

timeslot .

Herein, the actuator can in a first step be allowed to move from a full open to a full closed position, in order to obtain the boundary positions or set points and/or to register the presence of a tube.

A failsafe mechanism can be provided that shuts off liquid flow when system failure occurs and or failure of the flow restrictor. This as an alternative safety measure to prevent overdosing of a patient in question.

Brief Description of the Drawings

In order to further elucidate the invention, exemplary embodiments will be described with reference to the figures. In the figures:

. Figure 1 depicts a schematic view of a flow controlling system for a gravity feed infusion device for intravenous fluids according to a first embodiment of the invention;

Figure 2 depicts another schematic view of a flow controlling system for a gravity feed infusion device for intravenous fluids according to a further embodiment of the invention;

Figure 3 depicts another schematic view of a flow controlling system for a gravity feed infusion device for intravenous fluids according to yet another embodiment of the invention;

Figure 4 depicts a schematic flowchart diagram of the flow controlling system for a gravity feed infusion device for intravenous fluids according to an embodiment of the invention;

Figure 5 depicts a schematic graph of a dosing regime of the flow controlling system for a gravity feed infusion device for intravenous fluids according to an embodiment of the invention;

Figure 6 depicts a schematic graph of a dosing regime of the flow controlling system for a gravity feed infusion device for intravenous fluids according to a further embodiment of the invention;

Figure 7 depicts a schematic example of a graph representing a compensation factor for the dosing regime of the flow controlling system for a gravity feed infusion device for intravenous fluids according to an embodiment of the invention;

Figures 8A and 8B depict two perspective views of the housing used in the flow controlling system according to an embodiment of the invention;

Figure 8C depicts a perspective view of the closing member of the housing used in the flow controlling system, as depicted in figures 8A and 8B, according to a further embodiment of the invention;

Figures 8D and 8E depict a perspective view of plunger of a pinch valve used in the flow controlling system, as depicted in figures 8A and 8B, according to a further embodiment of the invention;

Figures 8G and 8F depict a perspective view of two main parts of a housing used for air bubble detector in the flow controlling system, as depicted in figures 8A and 8B, according to a further embodiment of the invention;

Figures 9A to 9E depict various parts of a housing suitable for drop detection in the flow controlling system for a gravity feed infusion device for intravenous fluids according to yet another embodiment of the invention. Detailed description of the invention

The figures represent specific exemplary embodiments of the inventions and should not be considered limiting the invention in any way or form. Throughout the description of the figures the same or corresponding

reference numerals are used for the same or corresponding elements .

The expression "the number of desired drops" used herein is to be understood as, though not to be considered limited to the number of drops calculated from the total administration volume per time, such that with a certain number of intermitted timeslot of administration, the administration volume per time is met. This value is

calculated by using the specific drop volume of the relevant infusion in use during the administration.

The expression "gravity feed" used herein is to be

understood as, though not to be considered limited to any infusion system, where the flow of the infusion liquid is obtained by gravity. In these systems a fluid storage is always positioned at a higher elevation than the position of the dosing needle, such that gravity forces acting on the fluid in the storage system urges the fluid downward, through the needle into the body or vein of the patient being treated.

In figure 1 and 2 schematic views are presented of a flow controlling system 1. In the flow controlling system 1 a sensor 2 can provide a signal 3 to a controller 4, which can be a logical computer. The controller 3 can operate the regulator 5, which is equipped with a groove 8 for an infusion tube and a plunger 6. The plunger can squeeze the infusion tube such that no flow through it is possible.

In the detector a recess 9 is arranged in groove passage way 10, in which recess 9 the drop chamber 15 of an infusion tube can be arranged. The sensor 2 can be equipped with a light sensor and a light source, each e.g. on

opposite sides of the drop chamber 15 of the infusion tube 13. By this arrangement, when a drop falls, the light path, from the light source to the light sensor, can be interrupted or changed. By this interruption or change, the sensor can register a drop, which can be sent to the

controller 4 as a signal.

In figure 2 and 3, in the schematic view of the flow controlling system, a schematic representation of an infusion device is presented.

In the controller 4, the number of drops can be counted, based on a signal 11B originating form the sensor 2, which can be compared to a set value, and can be used to control the regulator 5 in a way which is described in more detail with reference to figure 4. The controlling of regulator 5 is depicted by signal 11A originating form the controller 4. The signal 11B, originating from the sensor 5 can be amplified of converted from an analogue to a digital signal before it is provided to controller 4.

An infusion device generally comprises a fluid storage container or infusion bag 12, a connector 14, connecting the infusion bag 12 to the infusion tube 13, a drop chamber 15 and a second connector 16 for connection to a infusion needle 17. The infusion needle may be injected in a body part, such as arm 18 of a patient.

Optionally (not shown), the infusion tube 13 can be provided with an alternative valve for manually closing off the flow in the infusion tube 13.

In figure 4, an example of a regulation flow chart is depicted of the control algorithm of the flow controlling system. The algorithm or the controlling process starts at start block I, after which in block II, a timer is started for timing the lengths of the consecutive time slots, e.g. S1-S4 as depicted in figure 5 or T1-T4 as depicted in figure 6. After the timer is started, the regulator 4 is set open in block III, by opening a restrictor 24, which is described in more detail with reference to the figures 8A-8C. In Block IV, a check is performed to monitor if liquid is actually flowing by waiting on a signal from sensor 2. Sensor 2 is described in more detail with reference to the figures 9A- 9E. Now the passage way through the infusion tube 13 is open and infusion liquid can flow from the infusion bag 12 through the infusion tube 13 and the needle 17 into a vein of e.g. the arm 18 of the patient.

In figure 5 this is represented by the time slot SI. In the time slot SI, a number of drops N1 is

administered to the patient. Now, in block V, the number of drops will be compared with the number of drops that are calculated from the dosing regime set by a caregiver, this number is the desired number of drops. The caregiver can for instance enter the total dosing volume and the necessary time for this dosing volume to be dosed, and the system can calculate a desired dosing regime, from which the time slot length and the desired number of drops can be calculated. These calculations proceed in the system, yet outside the flowchart as presented in figure 5. If the number of drops reaches the desired number, the restrictor 24 is closed in block VI .

Now, in block VII, a check is performed to see if the time has actually lapsed by comparing the timer, which has been started in block II with a predetermined timeslot length. If the time has not lapsed, the loop LI will be continued until the time in the first timeslot SI or T1 reaches the predetermined set time. In this situation, the Blocks IV, V, VI and VII are repeated in loop LI until the time has lapsed and the flow chart is continued to block VIII.

If in block V the number of registered drops is below the desired number of drops that are calculated from the dosing regime, the flow chart is continued to block VII, leaving the restrictor 24 open such that the infusion remains administrating drops to- the patient. So in this situation the flow chart is looped through loop Ll by repeating blocks IV, V and VII, until the time has lapsed and the flow chart is continued to block VIII.

So when reaching block VIII, some situations could have occurred, one that sufficient drops have been

administered in the first time slot SI or Tl, or two that insufficient drops have been administered in the first time slot SI or Tl .^"Alternatively, if the flowrate is e.g.

relatively high, even if the restrictor 24 is closed in block VI, an overshoot in the number of drops may have occurred. In that case the number of drops actually

administered Ml is too high.

In Block VIII the restrictor 24 is closed, after which in block IX the timer is stopped and consecutively, in block X the number of registered drops, being the actual number of drops administered to the patient is stored. In block XI the time slot number is stepped up by one.

IN Block XII, the number of drops N1 or Ml are compared with the desired number of drops. If more drops are administered in slot SI or Tl than the number of desired drops per slot, the set value of the number of desired drops will be decreased in the consecutive timeslot T2.

This situation is schematically represented by figure 6, in timeslot Tl, the number of drops Ml in this example is 13, which is higher that the set value of the desired number of drops 12. In block XIII the set' value for the number of desired drops for timeslot T2 is now set to 11, i.e. the original set value of the desired drops minus the overshoot in drops in timeslot T1.

After this adaptation of the desired number of drops, loop L2 is entered and the flow chart is re-entered at block II, where the procedure is repeated. This will be performed until the loop L2 has been passed 5 times, because in block XVI, when the slot number reaches 5, the slot count is reset in block XVII, after which, in block XVIII, the drop rates or the total number of drops of the first 5 slots, i.e. slots 0, 1, 2, 3, 4 are stored in a logging data storage and the flowchart is again started at block II. In block XVIII, the newly set desired drop rate can now be adjusted based on e.g. the summation of number of drops or on the average number of drops in the preceding 5 slots, before the flowchart is continued again at block II.

If, after the comparison in block XII of the number of drops N1 or Ml with the desired number of drops, the numbers N1 of Ml are not too high, the flow chart is continued in block XIV. In block XIV, the number of drops Nl or Ml are compared with the desired number of drops.

If less drops are administered in slot SI or T1 than the number of desired drops per slot, the flowchart is continued to block XV. This situation is represented by figure 5. Here in slot SI, the number of administered drops is 13, while the desired number of drops in this case is 15.

In block XV the desired number of drops in time slot S3 is the originally desired number of drops increased with the deficiency of number of drops Nl, in comparison with the originally desired number of drops in slot SI. The desired number of drops was 14, the administered number of drops Nl was 13, so the desired number of drops for slot S2 is set to 15. After this correction of the desired number of drops, the flowchart is, as long as the number of slots is less than 5, looped back through loop L2 to block II, after which the flowchart is repeated, where each cycle from block II to block XVI represents one timeslot.

The last situation that can occur is when the number of drops administered in the first time slot N1 or Ml equals the, originally set, desired number of drops. In this case the desired number of drops in the following time slot is neither decreased in block XIII nor increased in block XV. Instead the flow chart is continued from block XIV directly to block XVI where, as long as the number of passed timeslots is less than 5, the loop L2 is entered and the flowchart is again continued at block II.

In the above described control algorithm, the steering parameter to correct the administration of fluids is the desired number of drops. An alternative way of controlling is by using the length of the dosage time slot as steering parameter. Thus in blocks XIII and XV, not the desired number of drops is controlled, yet the dosing time slot. The dosing time slot can e.g. be a pre-set partition of the set length of the time slots S1-S4 and T1-T4. If e.g. the number of administered drops is higher than the number of desired drops, the portion of the time slot that the restrictor 24 is open is reduced. On the other hand, if e.g. the number of administered drops is lower than the number of desired drops, the portion of the time slot that the restrictor 24 is open is increased.

Since both ways of controlling the administration of fluids in a feed forward control, a dampening on the control correction may be used to prevent instabilities due to overcorrection. Here the correction in number of drops and/or slot times may be proportional, integral or

differential or a combination thereof.

Another correction that is of significance is the derivation of the drop size at various flow rates. It appears that the volume of drops generated in the drip chamber 15 is dependent on the type and model of the infuse, the manufacturer and the speed in which the drops are generated. In figure 7, some deviation of the volume of drops is measured. In this case at a rate of about 100 drops per minute, the deviation was approximating a 10 percent decrement in drop volume. As a first correction, the drop volume is corrected by a parameter which represents the number of percent in which the drop volume is deviating. So in the example of 100 drops per minute, as indicated herein above, the compensation factor would be 10, relating in a volume compensation of minus 10%.

The compensation factor can be given as a set of fixed correction factors for a set flow ranges. As an example, for drop rates varying in the ranges 5-19; 20-39; 40-79 and 80-10, the compensation factors may be 1.00; 0.95;

0.92 and 0.90 respectively. In Figure 7, a series of drop size deviations is presented in the data points P1-P5.

Alternatively, the compensation factor can also be entered as a function, where in the example given a

logarithmic function may be applied. In figure 7, the line 24 is a proposed best fit logarithmic function that may be applied. Here the parameters in the logarithmic function for compensation of the drop size of infusion devices are again manufacturer, model and type specific.

In the system, if any of the controlling parts may fail, an additional solenoid operated pinch valve on the infusion tube may be activated that shuts down the flow, even if the restrictor 24 is for some reason open. Alternatively, the restrictor 24 may be a spring operated fail-close actuated plunger. Thus if the system give a malfunction for whatever reason, the restrictor 24 may be disconnected from power, such that its spring automatically closes the pinch valve.

In figure 8A-8C, the housing of restrictor 24 is presented. The restrictor 24 is a pinch valve, where a plunger 41 or 46, as depicted in figures 8D and 8E> is actuated by a motor, e.g. a stepper motor, which can be positioned in extending recess 26 of the housing 25 and extending recess 40 of the cover 38. In the recesses 26 and 40, opening slits are provided for cooling the motor, when in operation.

The housing 25 comprises a first lateral wall 27, being part of the housing and a second lateral wall 39, being a part of the cover 38. The cover 38 fits on the face 35 and can be attached by e.g. a click connection, by bolts in the ports 27A and 27B or by other means of attachment. In the housing a groove 28 is provided for engaging with the tube of an infusion device. The groove 28, visible in figure 8A is facing in lateral sense opposite to the open side of the housing as shown in figure 8B. This may aid in

separating the mechanical and electrical parts of the plunger and the motor from the infusion as much as possible, such that any ingress of fluids to the motor and plunger may be prevented. The groove 28 is provided with chute entries 29, to provide an easy access of the infusion tube in the restrictor 24. In the groove 28, knobs 31, 32, 33, 33A, 33B and 33C are provided, providing a local size restriction that is slightly less than the diameter of the infusion tube, such that the infusion tube will experience a little resistance when it is entered in the groove, such that it clicks in and remains at a fixed position. The gropve 28 further has a recess 34, which is accessible from the cover side of the restrictor 24, in which an air bubble detector 51 can be placed, as is shown in more detail in figures 8F and 8G. Such air bubble detector 51 may have a master shut downs authority over the entire controlling algorithm, since at all costs, the entry of air in the blood stream of a patient should be prevented.

Groove 28 is provided with a seat 30, against which the plunger 41 or 46 may restrict the infusion tube 13, as a pinch valve. The plunger 41 or 46 is kept in place by the guide 36 and can be operated by a motor, which can be arranged in the housing in bracket 37. Here a proximity sensor or limit switch may be incorporated to calibrate the motion of the plunger 41 or 46. This switch can be used to calibrate the actual plunger-tube conditions, by registering at exactly which position, first drops are flowing, and alternatively at which position, an alteration in the plunger position does not result in any change in the drop rate, because the tube 13 is for instance already at its maximum opening position in the restrictor 24.

The plunger 41 or 46 can in a first step be allowed to move from a full open to a full closed position, in order to obtain the boundary positions or set points and/or to register the presence of a tube. These positions can be monitored by the limit switch or the proximity sensor and sent to the controller 4.

In order to close the restrictor 24, the cover 38 can be placed against the face 35 such that it is the second lateral wall of the restrictor 24. Thus the parts vulnerable for external influences can be closed off properly.

In figures 8D and 8E, two plungers 41 and 46 are depicted. The plunger 41 comprises two sliding walls 42 and 43, which are dimensioned to fit into the slide 36 of the restrictor 24. In the plunger 41, there is a connector 45 to attach the plunger to a motor or linear actuator, in order for it to be operably and controllably arranged in the housing 25 of the restrictor 24.

Similarly the plunger 46 comprises two sliding walls 47 and 48, which are dimensioned to fit into the slide 36 of the restrictor 24. In the plunger 46, there is, as in the plunger 41, a connector 50 to attach_, the plunger to a motor or linear actuator, in order for it to be operably and controllably arranged in the housing 25 of the restrictor 24.

The profiles of the plunger may vary in order to compensate for the material properties of the infusion tube 13 and for different dosing regimes. For the more soft materials used as infusion tubes 13, the profile 49 of the plunger 46 may be preferred, while for the more rigid materials of the infusion tube 13, the profile 44 of plunger 41 may be preferred.

In figure 8F and 8G, an air bubble detector 51 is depicted. This air bubble detector 51 comprises a housing 52, which is equipped with a recess 53 on a first side, facing away from a second side, where the open side of the housing 52 is directed to. The housing is dimensioned and designed to fit into the groove 34 of the restrictor 24. The recess 53 in the housing 52 of the air bubble detector 51 is designed and dimensioned to fit around an infusion tube 13, when the sensor is positioned in the groove 34 of the restrictor 24.

In the housing 52 there is a sensor engaging space 54. This sensor can be a light sensor, which in normal operation is only faced with an infusion fluid, either standing still or flowing through the infusion tube 13, which infusion tube 13 is positioned in the groove 29 of the restrictor 24.

The air bubble detector can be closed with the cover 56, which is provided with two protruding rims 58 and 59, extending from the plate 57 in the direction of the interior of the housing 52, when arranged against the distal edge of wall 55. Here, the cover may engage with the housing 52 by means of a snap on connection, may be glued or welded or connected by any other suitable means.

In figures 9A to 9E various components of a sensor

2, as it is schematically depicted in figures 1 to 3, are shown. In figure 9A, a cap is presented, which is the top of the sensor 2. The cap comprises a plate 61, provided with slots 62 and 63. These slots 62 and 63 face with their open side in direction D, towards side A. The cap 60 is provided with a centrally arranged slot 67, which forms a shoulder 68 that borders on a first side a grove 65. On a second side the groove 65 is bordered by a second shoulder 66, which is an inwardly extending rim of the plate 61, enclosing slot 64. The shoulders 68 and 66 can engage and lock up an upper ridge of a drip chamber 15 of an infusion device. The .slot 67 and the groove 65 have an open accessing side in

direction D towards side A.

In figure 9B a stacking plate 69 is depicted. A series of these stacking plates 69 form, once neatly

stacked, the wall and engaging housing of the drip chamber 15 -of an infusion device as is elucidated in detail herein below. The stacking plate 69 comprises a plate 70, provided with two bores 73 and 74, which neatly align with the slots 62 and 63 of the cap 60 respectively. The plate 70 is provided with a central opening space 72, which on¹ its turn neatly aligns with the slot 64, yet the slot 74 comprises a narrow entry diameter towards the space 72, when compared with the entry diameter of the slot 64 of the cap 60.

In figure 9C, a sensor element 75 is depicted. The sensor element 75- has a similar contour as the stacking plate 69 and the cap 60. The sensor element 75 comprises two bores 80 and 81, which bores 80 and 81 align with the bores 73 and 74 of stacking plate 69 respectively and with the slots 62 and 63 of the cap 60 respectively. The sensor element 75 comprises a central space 79, which on its turn neatly aligns with the space 72 of the stacking plate 69 and with the slot 64 of the cap 60. The sensor element is equipped with a series of walls 84, which are designed and dimensioned to engage with on a first side a light source and on a second side a light detecting sensor. The sensor element comprises two protrusions form the face 77, which can be used to stack another sensor element on top, with the corresponding protrusions engaging recesses.

In figure 9D, an alternative sensor element is presented. Here the two protrusions on the face 77, as shown in figure 9C are omitted.

In figure 9E another alternative sensor element is shown, this element is provided with the protrusions 102 and 103, and the recesses 100 and 101 for the light source and the light sensor are smaller than the recesses shaped by the walls 82, 83, 84 and 85 in figure 9C.

The sensor 2 is arranged as follows: A stack of the stacking elements is taken and in the stack one or more of the sensor elements are integrated. The stacks are aligned such that the bores 74, 81 88 and or 96 are aligned and similarly that the bores 73, 80, 87 and 95 are aligned as well. Through these aligned bores, two bolts can be arranged, to fixate the individual elements 69, 75, 86 and 94, in any suitable combination, of more or less from the same and the other elements as listed. The so obtained stack of elements comprises a slit facing in direction D towards side A. This slit can in a direction D be arranged around the tube 13 of an infusion device. Once the tube 13 is positioned in the inner space of the stack formed by the spaces 72, 79, 90 and or 98, the stack can be moved in a direction along the tube 13 to engage and surround the drip chamber 15. Since the width of the slots 71, 78, 91 and 99 is larger that the diameter of the infusion tube 13, yet smaller than the diameter of the drip chamber 15 of the infusion device, the drip chamber gets locked in the inner space of the stack formed by the spaces 72, 79, 90 and or 98. Now that the stack is shifted in direction E to lock in the drip chamber 15, the cap 60 can be used to be positioned such that the surface of the plate 61 facing in direction F is in the same plane as the upper surface of the stack facing in a direction E. the slot 64 with the groove 65 can now be shifted in direction D over the upper edge of the drip chamber, while the slots 62 and 63 can slide around and engage the free ends of the bolts that hold the stack together. Since the upper opening in the slot 67 is of a smaller diameter that the diameter of the drip chamber 15, the drip chamber now is locked in and fixed in the sensor 2. Now the two bolts can be further tightened such that the entire stack including cap are united and have securely locked in and fixed the drip chamber.

In use, the neatly aligned slots 71, 78, 91 and 99 can be used as a viewing window, to visually inspect whether liquid is actually flowing. This may be aided by the light detection part, because each light detector can be provided with a light source.

It is possible that various manufacturers of infusion devices use drip chambers of varying dimensions. For that reason the number of plates can be varied to compensate for the differences in axial dimensions of the drip chamber. In an alternative, also the diameter and the heights of the stacking plates 69 may be varied.

The invention is to be understood not to be limited to the exemplary embodiments shown in the figures and described in the specification. For instance the

administration of fluids may be used in veterinary

applications, at e.g. animals. The dosage regime is now pre- set, but may also be adjusted to measured parameters of the patient under treatment. Here for instance, if a patient is receiving blood pressure regulating medicine, the measured blood pressure may be a parameter to adjust the dosing regime. Also glucose levels, insulin levels, temperature levels and or other measurable parameters of the patient may be used to amend the dosing regime.

The system may alternatively be applied to other gravity feed dosing systems, such as in aquaria, for

controlling the water quality of fish.

These and other modifications are considered to be variations that are part of the framework, the spirit and the scope of the invention outlined in the claims.

List of reference signs

1. Flow controlling system

2. Sensor

3. Signal

4. Controller

5. Regulator

6. Plunger

7. Signal

8 . Groove

9. Recess

10. Passage way

11A. Signal

1 IB . Signal

12. Infusion bag

13. Infusion conduit

14. Connector

15. Drip chamber

16. Connector

17. Needle

18. Arm of a patient

19. User interface

20. Signal

21. Signal

22. Curve

23. Curve

24. Tube restrictor

25. Housing

26. Extending recess

27. First lateral wall

27A. Port

27B . Port

28. Groove 29. Chute entry

30. Seat

31. Knob

32. Knob

33. Knob

33A-C Knob

34. Recess

35. Face

36. Guide

37. Bracket

38. Cover

39. Second lateral wall

40. Extending recess

41. Plunger

42. Sliding wall

43. Sliding wall

44. Pinch profile

45. Connector

46. Plunger

47. Sliding wall

48. Sliding wall

49. Pinch profile

50. Connector

51. Air bubble detector 52. Housing

53. Recess

54. Sensor engaging space

55. Wall

56. Cover

57. Plate

58. Protruding rim

59. Protruding rim

60. Cap 61. Plate

62. Slot

63. Slot

64. Slot

65. Groove

66. Shoulder

67. Slot

68. Shoulder

69. Stacking element 70. Plate

71. Slot

72. Space

73. Bore

74. Bore

75. Sensor element

76. Wall

77. Surface

78. Slot

79. Space

80. Bore

81. Bore

82. Wall

83. Wall

84. Wall

85. Wall

86. Sensor element

87. Bore

88. Bore

89. Surface

90. Space

91. Slot

92. Wall

93. Wall 94. Sensor element

95. Bore

96. Bore

97. Surface

5 98. Space

99. Slot

100. Recess

101. Recess

102. Tab

0 103. Tab

A. Side

B . Side

C . Direction

D. Direction

5 E. Direction

F. Direction

T. Time

Vcl . Cumulative volume

Vc2. Cumulative volume

0 LI. Loop

L2. Loop

N1-N4 Number of drops

M1-M4 Number of drops

P1-P4 Data point

5 S1-S4 Timeslot

T1-T4 Timeslot

I . Start block

II . Block: Timer start

III . Block: Open restrictor

0 IV. Block: Check if there is flow

V. Block: Is number of drops the desired number?

VI . Block: Close restrictor

VII . Block: Has the timeslot lapsed VIII . Block: Close restrictor

IX. Block: Timer stop

X. Block: Store number of drops

XI . Block: Next timeslot (Increase timeslot counter by one)

XII . Block: Is the number of drops larger than the desired number of drops per slot?

XIII . Block: Decrease the desired number of drops in next timeslot with the deviation in drops in last timeslot

XIV. Block: Is the number of drops smaller than the desired number of drops per timeslot?

XV. Block: Increase the desired number of drops in next timeslot with the deviation in drops in last timeslot

XVI . Block: Is the slot number larger than the

predetermined maximum?

XVII. Block: Reset timeslot counter

XVIII . Block: Total number of drops per unit time (drop rate)

Claims

1. A flow controlling system for a gravity feed infusion device for intravenous fluids, wherein the system comprises:

- a sensor configured to be attached to a drip chamber of the infusion device and configured to register any drops generated in the drip chamber;

- an infusion tube restrictor for controlling the size of a restriction of an infusion tube;

- a controller configured to control the infusion tube restrictor, wherein the controller is configured to:

- provide for a series of consecutive timeslots,

- set open the tube restrictor in a first timeslot, - calculate the cumulative number of drops registered by the sensor,

- close the tube restrictor in this timeslot,

- set open the tube restrictor again in a second timeslot and,

-wherein the controller is configured to use the number of registered drops in the first timeslot as a parameter for controlling the length of the second timeslot or the number of desired drops in the second time slot.

2. The flow controlling system according to claim 1, wherein the lengths of further consecutive timeslots are determined by the number of registered drops in a previous timeslot.

3. The flow controlling system according to any previous claim, wherein data storage is provided for storing data. ;

4. The flow controlling system according to claim 3, wherein the data storage provides for storing the number of timeslots, the number of drops in each timeslot, the total number of drops, a calculated dosage rate, a cumulative calculated dosing volume and/or other relevant

administration data.

5. The flow controlling system according to any previous claim, wherein the length of the timeslots is corrected by a compensation factor in order to compensate for increasing or decreasing drop sizes.

6. The flow controlling system according to claim 5, wherein the compensation factor is a staged value, being set at specific drop rate intervals, or wherein the compensation factor is the result of a calculated function of the drop rate, derived from e.g. experimental data.

7. The flow controlling system according to claim 6, wherein the system comprises a data entry and capturing interface for registration of the type of infuse which is used in the device, and memory comprising· a data set of compensation factors, related to the various types of infuses used, wherein on the basis of the type of infuse, the relevant compensation factor is chosen.

8. The flow controlling system according to any previous claims, wherein the tube restrictor comprises a housing, wherein the housing comprises two compartments, one compartment facing to a first side of the housing and one compartment facing to a second side of the housing, opposing and facing away from the first side.

9. The flow controlling system according¹ to claim 5, wherein the first compartment comprises a space; for an actuator, which actuator comprises a plunger.

10. The flow controlling system according to claim

5 or 6, wherein the second compartment comprises ah infusion tube engaging space.

11. The flow controlling system according to claim 10, wherein the first and second compartment are separated by a wall, which comprises an opening for allowing the plunger to move in and reach through, from the first compartment into the second compartment.

12. The flow controlling system according. to any of the claims 8-11, wherein the housing comprises a cover for covering the first compartment.

13. The flow controlling system according to any of claims 8-12, wherein the plunger is configured to pinch the tube in a manner that is configured to restrict and/or close off the fluid flow inside the tube.

14. The flow controlling system according to any previous claim, wherein the tube restrictor comprises a mounting clamp for mounting the restrictor on an infusion bag holder.

15. The flow controlling system according to any previous claim, wherein the system comprises a sensor system for a drip chamber, wherein the sensor system comprises a housing, the housing comprising a first drip chamber engaging part, said drip chamber engaging part having drip

chamber receiving space, extending over the full height of the engaging part from a top face to a bottom face, said drip chamber engaging part comprising an tube entry slot, similarly extending over the full height of the engaging part from a top face to a bottom face, which entry slot is narrow in relation to the diameter of the drip chamber receiving space and is configured to allow a tube of an gravity feed infusion set to fit though, yet is dimensioned to be too narrow to allow the drip chamber to fit through.

16. The flow controlling system according to claim 15, wherein the housing of the sensor system comprises a second part, which second part can be attached to the first part, the second part comprising a drip chamber top engaging part at a first side, which first side_. is configured to close on the top face of the first drip chamber engaging part of the housing in an assembled state, which opening is narrowing towards a top side, which top side is facing away from the first side, the opening being configured to lock-in a drip chamber, said second part further comprising an entry slot, of which entry slot, an opening is facing sideward and is configured to allow a tube of an gravity feed infusion set to fit though, yet is dimensioned to be too narrow to allow a drip chamber and/or the top of a drip chamber to fit through.

17. The flow controlling system according to claim 15 or 16, wherein the first housing part comprises a light source and a sensor, the sensor being configured to register any drops in the drip chamber.

18. A method of controlling a flowrate from a gravity feed infusion system, comprising the following steps, to be executed in any suitable order:

a) providing a storage for a liquid, with ;a tube for allowing gravity feed flow,

b) providing a drip chamber,

c) providing a drop registering sensor on the drip chamber,

d) providing a controller,

e) providing an actuator operating a flow restrictor for the tube,

f) having the controller controlling in a series of consecutive timeslots the position of the actuator of the flow restrictor,

g) having the controller controlling the length of a consecutive or later timeslot or the desired number of drops in a consecutive or later timeslot, on the basis of the number of drops registered and/or calculated in the or any previous timeslot.

19. The method according to claim 18, wherein the actuator is in a first step allowed to move from a full open to a full closed position, in order to obtain the boundary positions or set points and/or to register the presence of a tube .

20. The flow controlling system wherein a failsafe mechanism shuts off liquid flow when system failure occurs and or failure of the flow restrictor.