WO2009003560A1

WO2009003560A1 - Device for preventing a free catheter flow

Info

Publication number: WO2009003560A1
Application number: PCT/EP2008/004281
Authority: WO
Inventors: Hanspeter Niklaus; Roger Haenggi
Original assignee: F.Hoffmann-La Roche Ag; Roche Diagnostics Gmbh
Priority date: 2007-06-29
Filing date: 2008-05-29
Publication date: 2009-01-08
Also published as: US20120179116A1; EP2008681B1; US20100185151A1; DE502007005954D1; ATE491492T1; US8114056B2; EP2008681A1; US8382720B2

Abstract

The invention relates to a catheter, comprising a catheter wall and a flow region limited by the catheter wall, for connecting an administering device to an administering needle, characterised by at least one catheter portion at which at least one partial piece of an inner wall of the catheter abuts at least one other partial piece of an inner wall of the catheter, in order to block or obstruct the flow of a medium through the catheter, wherein the flow is opened when the medium exhibits a pressure above a predetermined blocking pressure.

Description

Attorney's File No.: 56 664 XX Applicant: Roche Diagnostics GmbH

F. Hoffmann-La Roche AG

Device for Preventing a Free Catheter Flow

The present invention relates to a device for preventing a free catheter flow (free-flow prevention) and in particular to a catheter which is formed such that a free flow of a fluid through the catheter due to a hydrostatic pressure of the fluid being channelled in the catheter is prevented. The invention also relates to a system comprising such a catheter and an administering device, in particular an infusion pump.

Known infusion systems store the drug to be administered in a container, usually an ampoule, in which a carrier fluid with the drug dissolved in it - referred to in the following simply as the drug fluid - is situated between a movable stopper and a container outlet. The rear end of a catheter is connected to the container outlet. A needle, which is introduced into the human or animal body in order to administer the drug fluid, is placed on the front end of the catheter and in most cases remains there for an administering period which is often several days, wherein if the container with the drug fluid is situated at a greater height than the front end of the catheter and/or the needle, there exists the danger, if the difference in height between the container and the front end of the catheter is large enough, of the container gradually emptying itself due to the force of the column of fluid.

In insulin therapy using portable infusion apparatus, for example pump apparatus, the catheters used can exhibit lengths of more than 1 m. If the apparatus, including the container, is arranged vertically above the user, for example at night or when showering, a hydrostatic ground pressure of about 0.1 bar is generated, if no other effects - for example friction losses, discharge effects or capillary action - are taken into account in addition to the purely static pressure due to the inherent weight of the drug fluid, and if the density of water is assumed for the drug fluid. In order to prevent any undesirable discharge due to the pressure of the column of fluid, the wall friction between the stopper, which is accommodated in the container such that it can slide freely, and the container wall could be increased; however, this would incur other disadvantages. Another solution would be to fix the stopper to the driven member of an infusion pump, such that the stopper prevents the surface of the fluid from dropping in the container and so prevents it from emptying itself. Known systems screw the stopper to the driven member. This, however, increases the cost of the apparatus. Also, this solution cannot be used with prefabricated ampoules, since the stopper is not prepared for a screw connection.

International application WO 97/02059 relates to an infusion pump comprising a pump casing and a safety valve which is intended to prevent delivery of the drug from being caused by gravity alone. The connecting casing of the pump is detachably fastened to the pump casing. Also, its upstream end is connected to a sack-like drug reservoir via a catheter and an inlet connector.

International application WO 95/16480 discloses an infusion device comprising a drug container, a catheter leading away from it, a clamp arranged on the catheter, a pump connected to the catheter, another catheter leading from the pump to the patient, and a safety valve arranged in said other catheter. By means of the clamp for the first catheter and the safety valve, the intention is to prevent the drug fluid from being undesirably conveyed due to gravity.

EP 0 882 466 A2 discloses a device for administering, in particular infusing, a drug fluid in doses, comprising a container from which the drug fluid is displaced in doses through an outlet when a stopper is advanced, in order to administer it, and comprising a catheter which is connected to the container at the outlet, wherein the front end of said catheter facing away from the outlet is or can be connected to an administering needle, wherein a valve is arranged between the outlet and the administering needle in a flow cross-section of the drug fluid, and the valve only allows a flow towards the front end of the catheter when the fluid pressure acting in this direction is greater than a pressure bearing on the valve as a result of the inherent weight of a column of fluid in the device, in order to prevent the container from emptying itself. It is an object of the invention to provide a catheter and a system consisting of such a catheter and an administering device, which prevent a drug fluid or substance which is dispensed through the catheter from being dispensed or discharged in an uncontrolled manner.

This object is solved by the subjects of the independent claims. Advantageous embodiments are defined in the dependent claims.

A catheter in accordance with the invention for connecting an administering device, such as for example an infusion pump which is known in its own right, to an administering needle which can for example be included in a so-called infusion set, comprises a catheter wall which is preferably provided as a continuous one-part wall of a preferably tubular or flexible tubular catheter made for example from an elastic material. The inner side(s) of the catheter wall limit or define the flow region of the catheter, through which a drug fluid or substance, dispensed for example from an infusion pump, is conveyed to an administering point and in particular to an administering needle. In accordance with the invention, the catheter comprises at least one catheter portion at which at least one partial piece of the inner wall of the catheter abuts at least one other partial piece of the inner wall of the catheter, in order to automatically block or obstruct the flow through the catheter, wherein the flow is re-enabled and the catheter opened when the fluid being guided in the catheter exhibits a pressure above a predetermined minimum pressure of for example more than 0.1 bar or more than 0.2 bar.

Providing a catheter portion comprising an inner wall of the catheter which, in its normal state without the application of a predeterminable minimum pressure of the fluid being guided by the catheter, is automatically deformed - for example by correspondingly shaping the catheter wall and/or using specific, for example elastic, materials or by applying an external force such as for example attaching one or more clamping pieces - such that a flow through the catheter is only possible once a predeterminable minimum pressure of for example more than 0.1 bar is exceeded, has the advantage that additional valves do not have to be provided at the end of the catheter or in the catheter, in order to prevent a free flow. A self-blocking catheter in accordance with the invention can thus be designed very simply and also prevents incorrect use, since additional valves do not have to be connected and therefore also cannot be forgotten when using the catheter. The catheter can advantageously comprise two or more catheter portions which are for example spaced apart from each other in the longitudinal direction or flow direction of the catheter, to form two or more zones in order to prevent a free flow through the catheter when a pressure below the predetermined minimum pressure is applied. For example, two or more zones can be formed in immediate succession, within which the inner walls of the catheter abut each other, wherein preventing a free flow at a pressure below the predeterminable minimum pressure can for example be realised by an individual zone, in particular by the inner walls of the catheter abutting each other, or by automatic sealing within an individual region or zone, or also by a number of for example successively arranged zones co-operating, in which the catheter walls abut each other, spaced apart from each other in the longitudinal direction of the catheter, at a number of portions and thus form a number of blocking or securing elements in the longitudinal direction.

The minimum pressure which has to be applied in order to re-open the self-blocking or self- sealing on the catheter is preferably around at least 0.1 bar and preferably above this, i.e. in the range above 0.15 bar or 0.2 bar or above 0.3 bar or 0.7 bar.

When the ampoule is biased, i.e. a minimum impact force is applied to the stopper, it may be that the fluid pressure at the outlet region of the ampoule is around a higher pressure of for example 0.5 bar. Accordingly, the opening pressure of the catheter should be around this higher pressure, plus a safety pressure of for example 0.1 bar or 0.2 bar.

In order to obstruct administering the drug in doses as little as possible, but still securely prevent discharge, the catheter is preferably configured such that it only allows the flow towards the front end of the catheter when the fluid pressure in this direction exceeds the maximum possible pressure of the column of fluid, preferably multiplied by a safety factor. Since, in the present case, the valve is being used in the medicinal field, said safety factor particularly preferably corresponds to the value 3. For a maximum catheter length of about 1 m and a negligible column of fluid in the container, the maximum fluid pressure at the free end of the catheter measures about 0.1 bar, such that in this case, the catheter is configured such that it only opens when the fluid pressure exceeds 0.3 bar. These are also the dimensions for its preferred use in a portable infusion pump. The catheter is preferably self-closing or self-blocking below the aforementioned blocking pressure or minimum pressure and can thus effectively prevent a substance or drug fluid from unintentionally flowing through it due to the pressure of the column of fluid within the catheter.

The catheter preferably comprises regions or portions in which the walls of the flexible tube are biased against each other. This can for example be achieved by only one partial piece being biased towards another, for example opposing inner wall of the catheter in the circumferential direction of the catheter, or by two regions of the catheter wall which for example oppose each other being biased towards each other, in order to preferably abut each other when there is a lack of pressure in the medium being guided in the catheter, such that the flow is blocked below the mentioned minimum pressure which enables a flow. A partial piece of the catheter or a region of the catheter wall can for example be biased by using an elastic material which is provided on or in the catheter or as a part of the catheter wall, such that one or more catheter walls are biased in a direction which reduce and preferably completely seal the flow region, i.e. an opening within the catheter.

Alternatively or additionally, an external element such as for example a clip or clamping device which is for example formed as a U-shaped spring element can generate an external force which acts on the outer wall or walls of the catheter, in order to press together the catheter between or by the clip element or spring element. When the predeterminable minimum pressure is applied, for example generated by an infusion pump, a fluid passing through the catheter can press the external element apart far enough to enable a flow through the catheter, which is limited in accordance with the pressure being applied or which is unobstructed.

The catheter can also be reshaped by a production process or by an external element, such as a clamping element, such that the catheter is not annular in cross-section like known catheters but rather exhibits a different shape which is advantageous for blocking a flow, such as for example the shape of a flat flexible tube in which the wall halves abut each other and can thus prevent a flow at a low pressure.

Furthermore, it is also possible for the catheter to be embodied so as to be bent or sharply bent and for this bent or sharply bent shape to be realised either by the catheter materials or catheter geometry used and/or by an external element such as for example a clamping piece which holds the catheter in a bent or sharply bent shape.

In accordance with another aspect, the invention relates to a system comprising a catheter such as has been described above and an administering device, in particular an infusion pump, for administering a drug fluid in doses, wherein the drug fluid is contained in a container from which it is displaced, in order to be administered, in doses by advancing a stopper which is movably accommodated in the container towards a container outlet. The rear end of a catheter such as has been described above can be connected directly to the outlet of the container, where an outlet piece and/or outlet support for connecting a catheter is provided. The catheter is usually a flexible tubular catheter. It would, however, be equally possible to use a rigid catheter comprising elastic partial pieces. The front, free end of the catheter is or can be connected to a needle for administering the drug. "Administering" is understood to mean both infusing and injecting and a combination of the two types of administering. The invention is in particular intended to be used in infusion devices and/or infusion apparatus, which are particularly preferably portable pump apparatus for insulin treatment.

The self-blocking element or partial piece of the catheter is preferably arranged between the container outlet and the needle for administering the drug, in a flow cross-section of the drug fluid. The catheter is dimensioned such that, in order to prevent it from emptying itself, it only allows a flow towards the front end of the catheter when the fluid pressure acting in this direction is greater than a pressure bearing on the self-blocking portion as a result of the inherent weight of the column of fluid in the device. If the device is a mass-produced device, for which a whole range of catheters having different lengths are available, then the self-blocking portion is dimensioned for using the longest catheter, i.e. for the maximum possible column of fluid.

Although the self-blocking portion or the self-blocking partial regions of the catheter can in principle be placed at any point between the container outlet and/or infusion pump and the administering needle, said portion or region is preferably arranged as near as possible to the outlet of the container or as near as possible to the infusion pump. In accordance with another aspect, the invention relates to a method for preventing a free flow through a catheter, wherein at least a partial region of the catheter or the catheter wall prevents the flow of a medium below a predetermined minimum pressure, and wherein the catheter is pressed open in order to enable the flow when the medium exceeds the minimum pressure.

The invention is illustrated below on the basis of preferred embodiments. There is shown:

Figure 1 a top view onto a partial piece of the catheter in accordance with a first embodiment, comprising a clip;

Figure IA a sectional view along the line A-A in Figure 1 ; Figure IB a sectional view along the line B-B in Figure 1 ; Figure 2 a second embodiment of a self-blocking catheter comprising two blocking regions;

Figure 2A a cross-sectional view along the line A-A in Figure 2;

Figure 3 a schematic representation, to illustrate the working principle of the invention;

Figure 4 a third embodiment comprising a number of successively arranged, sharply bent regions; and Figure 5 a fourth embodiment of a self-blocking catheter comprising a separate pressure element.

Figure 1 shows a first embodiment of a blocking valve 2 which is formed on a catheter 1, directly on or in the flexible catheter tube and preferably in the vicinity of the outlet point of the pump (not shown). The blocking valve 2 is configured such that it blocks when an interior pressure of the flexible tube or a pressure of the medium being guided in the flexible tube 1 is 0.1 bar or less, and opens at higher pressures and allows a flow through the flow region Ib of the catheter 1.

The first embodiment of the catheter 1 shown can for example be obtained by reshaping the catheter or flexible tube in the region of the valve 2 by means of a thermal reshaping method, wherein the annular or tubular cross-section of the catheter 1 is reshaped in the region of the valve 2 into a flat flexible tube, as shown in the sectional view in Figure IA, such that the wall halves Ia of the catheter 1 abut each other and can thus prevent a flow when a low interior pressure is being applied. If the pressure of the medium being guided in the catheter 1 rises above the predetermined minimum pressure of for example 0.1 bar, the inner wall Ic of the catheter is pushed open and the valve 2 is opened, such that a flow through the catheter 1 is possible.

As can be seen in particular from Figures IA and IB, the valve 2 can be fitted with a clip 3 which is formed as a U-shaped spring element and comprises pressing pieces 3a and 3b. The clip 3 is arranged around the catheter 1 and can bias the catheter halves and therefore the inner walls Ic of the catheter against each other via its clamping force. By means of the clip 3, it is possible to set a defined blocking force or blocking pressure. The greater the force with which the clip 3 presses the catheter walls Ic onto each other, the greater the minimum pressure of the medium which has to be applied in order to enable a flow through the catheter 1.

If such a catheter 1 , comprising one or more valves 2 successively arranged in the longitudinal direction of the catheter 1, is connected to an administering device such as for example an infusion pump, the catheter 1 is connected to a reservoir 4 for a substance or medium to be administered. Usually, a stopper 5 is inserted into the reservoir 4 or an ampoule 4 by an infusion pump, such that the interior pressure in the ampoule 4 is increased and a substance contained in the ampoule 4 is dispensed from a dispensing opening 4a of the ampoule 4. This causes a rise in pressure in the connected catheter 1, which ensures that the catheter walls Ia, which are biased against each other, are pushed open and that a desired amount of the substance, such as for example insulin, can thus be dispensed to a patient. As soon as the desired amount of the substance has been administered, and the stopper 5 of the reservoir 4 is for example at rest again, the valve 2 closes due to the force of the clip 3 which presses the catheter 1 together again, automatically. The opening pressure for the valve 2 is thus set or defined by the biasing force of the clip 3.

Figure 2 shows a second embodiment of a catheter 1 in accordance with the invention, comprising two valves 2. The two valves 2 are arranged in two zones spaced apart from each other in the longitudinal direction of the catheter 1, and comprise catheter walls Ia which are respectively biased against each other, wherein one catheter wall 1 a of a first side, shown on the left in Figure 2 A, is biased towards the second side (downwards), such that the inner walls Ia of the catheter abut each other and prevent a flow of a medium when a predetermined minimum pressure is not being applied. In the region of the second valve, shown on the right, the bias relative to the first valve is reversed, i.e. the opposing second side is biased towards the first side, such that the desired valve blocking effect occurs.

Each bias of a catheter wall Ia can thus be regarded as an aperture. If a number of apertures are arranged in series, the overall difference in pressure is divided into stage differences in pressure, such that the drop in pressure per valve zone can be reduced. Reducing the overall difference in pressure is advantageous, since the closing force per valve zone can then be reduced and the functional reliability of the overall valve, formed from a number of valve zones, can thus be increased.

In accordance with another embodiment, a valve function using a catheter 1 can be achieved by moving the catheter 1 into a sharply bent region using a defined path-force element (spring). When the pressure rises, for example between 0.5 and 0.8 bar, the catheter 1 is released from the sharply bent region and so releases the flow.

Figure 3 schematically shows an ampoule 4 comprising a stopper 5 which can be shifted within it in the direction of the arrow and using which a substance contained in the ampoule 4 can be dispensed from a dispensing opening 4a to the catheter 1 connected to the ampoule 4. If, for example, the difference in height between the lower and upper end of the catheter 1 measured one metre, then a partial vacuum of 0.1 bar would be applied at the upper end of the catheter 1, which could cause a substance to be unintentionally dispensed from the ampoule 4 in an uncontrolled manner, solely due to the hydrostatic pressure generated by the column of fluid in the catheter 1.

It is therefore advantageous to arrange a valve in the upper region of the catheter, since a partial vacuum of 0.1 bar in relation to a relative exterior pressure of 0 bar causes the catheter walls Ia to be automatically pressed together. If the catheter walls Ia are elastic, the partial vacuum in the upper catheter portion can therefore be utilised such that in the event of a hydrostatic pressure distribution in the catheter, the valve is automatically closed. If the above-described catheter 1 in accordance with the invention is used, then it is possible to prevent a substance from being unintentionally dispensed from the ampoule 4 through the catheter 1.

Advantageously, a number of sharply bent regions Id can also be successively arranged, as shown in Figure 4, wherein a catheter or flexible tube 1 is accommodated in a clamping piece or clip 3 which can consist of an upper part 3c of the clamping piece and a lower part 3d of the clamping piece, which can be connected to each other. The catheter 1 is inserted into the catheter guides, which are for example formed by a number of preferably mutually parallel partition walls 3e, such that the catheter 1 is for example held meandering or snaking or winding in the clamping piece 3, wherein linear regions of the catheter 1 are parallel to each other, separated by the wall pieces 3e, wherein a sharply bent region Id is provided in each region in which the catheter 1 transitions from one guide, formed by two adjacent wall pieces 3e, to the next guide. Figure 4 shows the open-catheter state, in which the sharply bent regions Id are open, due to an applied pressure of for example more than 0.7 bar, and so enable a flow of a medium through the catheter 1. If a pressure below 0.7 bar is being applied, the catheter 1 is deformed in the region of the sharp bends Id, such that a medium is prevented from passing through the catheter 1.

The clamping piece 3 can for example be formed to be rigid, such that when the pressure of the medium being guided in the catheter 1 rises above 0.7 bar, a flow is enabled solely by the deformation of the catheter 1. Alternatively, the clamping piece 3 can also be formed to be elastic or flexible, such that when the pressure of the medium being guided in the catheter 1 rises, the clamping piece 3 is deformed or expanded and so releases the flow for the fluid being guided in the catheter 1.

Although the clamping piece 3 could in principle be formed in one piece, it is preferably formed - in order to more easily insert the catheter 1 - from two partial pieces 3c and 3d which can be placed onto each other or connected to each other, once the catheter 1 has been inserted into the clamping piece 3d in the manner shown in Figure 4, such that the catheter 1 exhibits a number of successive sharply bent regions Id, preferably on two opposing sides of the clamping piece 3. Figure 5 A shows another embodiment of a blocking mechanism for a catheter 1, wherein a catheter blocking valve can be both integrated into the catheter 1 and formed as a separate valve piece which can be inserted between two catheter pieces 1. In the embodiment shown in Figure 5A, a valve base body 4 made from a thermoplastic elastomer (TPE) can be seen which is formed in the shape of a disc or plate and is preferably flat, and has been inserted between two catheter pieces 1 , wherein the valve base body 4 has been placed onto the catheter pieces 1 in the region of a fusing zone 4a and connected or fused to the catheter pieces 1, so as to be an integrated part of the catheter. A sealing or covering element 4b, in the form of a film which is likewise formed from a thermoplastic elastomer, is placed onto the valve base body 4 and can be formed double-layered and from a different material to the valve base body 4. The film 4b is connected to the valve base body 4 in the region of a fusing zone 4c.

A bent clip 3 formed from spring steel is slid or placed onto the valve base body 4 connected to the film 4b, in a similar way to the embodiment described with respect to Figure 1, and comprises two mutually opposing pressure surfaces 3f and 3g, such that for example the upper pressure surface 3f can press onto the film 4b and the lower surface 3g can press onto the lower side of the valve base body 4. Figure 5C is a top view onto the clip 3 which is shown in a lateral view in Figure 5B.

If a pressure of for example less than 0.7 bar is being applied to the medium being transported in the catheter 1 , then the film 4b is pressed into the valve base body 4 or the valve base body 4 is pressed together with the film 4b, such that a flow of a medium cannot occur. If the pressure of the medium rises above 0.7 bar, then the clip 3 is pressed apart by the pressure of the medium, i.e. the pressure surfaces 3f and 3g are pressed away from each other, in order to enable a flow of the medium.

The blocking pressure of the valve shown in Figure 5 can be altered by the configuration of the clip 3, and in particular by its manufacture, deformation and material constants or processing, such that the valve can also open at a lower pressure of for example 0.1 bar or 0.2 bar or at a higher pressure of for example 1 bar or above.

Claims

Attorney's File No.: 56 664 XX Applicant: Roche Diagnostics GmbH F. Hoffmann-La Roche AGDevice for Preventing a Free Catheter FlowPatent claims

1. A catheter, comprising a catheter wall (Ia) and a flow region (Ib) limited by the catheter wall (Ia), for connecting an administering device to an administering needle, characterised by at least one catheter portion at which at least one partial piece of an inner wall (Ic) of the catheter abuts at least one other partial piece of an inner wall (Ic) of the catheter, in order to block or obstruct the flow of a medium through the catheter (1), wherein the flow is opened when the medium exhibits a pressure above a predetermined blocking pressure.

2. The catheter according to claim 1, comprising at least two catheter portions which are preferably arranged in succession in the longitudinal direction of the catheter (1), within which the inner walls (Ib) of the catheter abut each other, in order to block a flow of a medium below a minimum pressure.

3. The catheter according to any one of the preceding claims, wherein at least one partial region of the catheter is formed to be self-closing or is formed as a flat catheter.

4. The catheter according to any one of the preceding claims, wherein the blocking pressure is around 0.1 bar or 0.2 bar or 0.3 bar or 0.7 bar or above.

5. The catheter according to any one of the preceding claims, comprising at least one partial region including catheter walls (Ia) which are biased against each other.

6. The catheter according to any one of the preceding claims, comprising at least one partial region in which a catheter wall (Ia) exhibits a different elasticity and/or material and/or thickness to another partial region, in order to achieve a self-blocking valve effect.

7. The catheter according to any one of the preceding claims, comprising a clamping device or clip (3), in order to deform at least a partial region of the catheter (1) such that the inner walls (Ia) of the catheter abut each other in said partial region.

8. The catheter according to any one of the preceding claims, comprising at least one sharply bent region from which the catheter (1) can be automatically detached when a medium is flowing through it at a minimum pressure, in order to achieve detachable self-blocking of the catheter (1).

9. A system comprising a catheter (1) according to any one of the preceding claims, and an administering device or infusion pump.

10. The system according to the preceding claim, comprising a needle and/or an infusion set which is connected to the end of the catheter opposite the end of the catheter which is connected to the administering device.

11. The system according to any one of the preceding two claims, wherein the at least one catheter portion for generating a blocking effect or valve effect is arranged in the region of or near to the administering device.

12. A method for preventing a free flow through a catheter (1), wherein at least a partial region of the catheter (1) or the catheter wall (Ia) prevents the flow of a medium below a predetermined minimum pressure, and wherein the catheter (1) or the catheter wall (Ia) is pressed open in order to enable the flow when the medium exceeds the minimum pressure.