DE3104985A1 - "MEDICAL INFUSION DEVICE AND METHOD FOR OPERATING THE SAME" - Google Patents

Description

Applicant: ANDROS INCORPORATED

Berkeley, California USA

Title: Medical Infusion Device and Method of Operating the Same

Representative: Patent Attorneys Dipl.-Ing. S. Schulze Horn M.Sc. Dr. H. Hoffmeister Goldstrasse 36 4400 Munster

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Medical infusion device and method of operating the same

The invention relates to a medical infusion device and, more particularly, to an improved device of this type and a method of operating this device.

In the US patent application 79 806 a medical infusion device is described, with the help of which liquid or semi-solids from an upstream (upstream) line section to a downstream (downstream) section are eligible for funding. The pump includes upstream and downstream lines and a removable cassette connecting these two lines. The cassette has a window provided, which is spanned by a membrane. Elements provided on the pump press against the membrane to vary the volume of the pump or delivery space formed by the cassette. The cassette also has inlet and outlet openings which communicate with the pumping chamber without the interposition of valves stand. The fluid contained in the line is through (alternating) constriction and opening

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of the line cross-section at upstream and downstream points and thus corresponding displacement of the content of the cassette conveying space.

This previous medical infusion device offers significant advantages over many previous designs Advantages. Since no valves are provided in the cassette, its reliability is improved and so is its Production simplified with a corresponding reduction in costs. It also has increased accuracy in comparison achieved compared to previous cassette designs. By appropriately controlling the disconnection of the lines At the inlet and outlet of the cassette there can be perfectly constant flow rates, even extraordinary low flow or throughput quantities can be achieved.

On the other hand, it has been found that in this previous infusion device, a presence of Air in the cassette conveyor space can interfere with the operation of the device quite considerably. This is on three Phenomena can be attributed to: Firstly, at high back pressures, the liquid level in the device rises feeding drip chamber due to the expansion of the compressed air when the inlet valve is opened

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the filling. As a result of this countercurrent flow of the liquid back to the drip chamber, warning or alarm units, such as an alarm unit for an empty bottle, can be triggered unnecessarily. Second, decreased
the flow outlet when there is back pressure and
Increase the volume of air, which affects the (dosing) accuracy. Thirdly, there is one with low or negative counter-pressures - for
Example with low needle positions of -305 mm
up to -915 mm below the cassette - the supply flow rate is higher due to the expansion of the air when the outlet valve is opened, which also affects the dosing accuracy.

The influences of the air contained in the cassette can essentially be reduced or eliminated by the fact that the outlet of the conveying chamber is in a
such a position is arranged that air bubbles to
Wander outlet and be driven out together with the pumped liquid or semi-solid. A
such working principle is according to the cassette
U.S. Patent 4,140,118 applied. Although this arrangement is generally satisfactory, it may from time to time cause confusion to hospital staff or the like because most of them are conventional and conventional

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Drug infusion systems are arranged so that the liquid flows continuously downwards. In addition, the Cassette according to the said US-PS separate inlet and outlet valves, so that they are as a result for applications is expensive, in which the cassette is discarded after each use or after 24 hours for reasons of sterility.

The invention is therefore based in particular on the object of creating an improved combination of a pump and a cassette for a medicament infusion device and an improved method for operating this device. The influence of the air contained in the cassette on the metering accuracy should be largely eliminated, and the
The cassette itself should be easy to insert into the pump and should not cause any misunderstandings when making the device ready for operation.

With the method according to the invention for operating the medical infusion device, the
Influence of the air contained in the delivery chamber on the metering accuracy can be largely eliminated.

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The solution to this problem results from the features characterized in the accompanying patent claims.

Below is a preferred embodiment of the invention in conjunction with the accompanying drawings explained in detail. Show it:

1 shows a schematic representation of a medical infusion device with features according to the invention,

Fig. 2 is an exploded, enlarged, sectional view of one of the apparatus according to Fig. 1 used cassette,

3 and 4 are schematic sectional views to illustrate the mode of operation of the pump according to FIG. 1 and

FIG. 5 is a graphic representation of the mode of operation of the cam drive device according to FIG. 3.

Generally speaking, the medical one according to the invention is used Infusion device according to FIG. 1 for the promotion of

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- 42.

liquid or semi-solids from an upstream or upstream flexible line part to a downstream or downstream flexible line part Line part 13. The line part 11 on the upstream side can be connected to a fluid supply 12 and the downstream flexible conduit part 13 may be so arranged as appropriate be that the substance to be conveyed is supplied to a patient 14. The device comprises a pump 15, 3 elements 16 and 17 for holding the Has line parts 11 and 13, respectively. First constriction or Throttling means 21 serve for selective narrowing or compressing and opening the upstream line part 11. Second constriction or throttle means 22 act on the downstream conduit part 13 in a similar manner. A removable cassette is connected via connection elements 23 and 24 to the two line parts 11 and 13, respectively. The one pump or The cassette 18 defining the conveying space 25 has a flexible membrane 26 which forms part of the conveying space limited. Means 27 are used to removably hold the cassette in a position between upstream and downstream conduit part for connection therewith. An actuator 28 attacks the membrane and is made of a fully back

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pulled position according to FIG. 3 in a fully advanced Position according to FIG. 4 can be moved in order to displace a predetermined volume in the delivery chamber. Another device 29 is used to actuate the actuating device and the first and second Throttle device in such a cycle that the liquid or semi-solid material from the upstream line part be conveyed to the downstream part of the line. For extensive reduction or elimination the unfavorable influence of air contained in the pumping chamber, the following measures are provided:

1. The actuator is driven so that the volume of the conveying chamber before the opening of the downstream section or line part significantly enlarged to fill the conveying chamber;

2. the actuating device is controlled in such a way that they the volume of the pumping chamber after closing the upstream part and opening the downstream part Partly to expel the contents of the conveying space to a residual volume of less than approximately 0.07 ml decreased. As a result, the largest amount of air left in the cassette is can, about 0.17 ml, because in the inlet and outlet also together about 0.10 ml of air can settle. This small amount of air (0.17 ml) only has a

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negligible influence on the flow and metering accuracy.

Figure 1 specifically illustrates the invention in the form of an intravenous infusion device for delivery of a Fluid from an appropriate supply 12 to a patient 14. The fluid becomes intravenous administered via a suitable catheter 30, which is attached to the downstream line part 13 of the conveyor system connected. The catheter is attached to the arm in a manner known per se by means of an adhesive strip 31 of the patient 14 held. The fluid supply 12 can be a standard intravenous dropper bottle, which is suspended from a stand 32. A drip chamber 32 is connected to the lower part of the bottle 12, which can be of conventional construction. A suitable, not shown, can be placed under or on the drip chamber Alarm unit to indicate that the bottle has been emptied, in order to provide a signal when the contents of the bottle 12 have been emptied. The contents of the bottle 12 flows over the upstream Line part 12 of the conveyor system, which in the embodiment shown consists of a flexible hose.

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310A985

Although the bottle 12 according to FIG. 1 on the stand 32 in is located in an elevated position relative to the patient 14, as is the case with many intravenous delivery systems is typical, such an arrangement is not decisive in the device according to the invention, because the fluid is conveyed to the patient by the forced delivery action of the pump 15. The pump 15 can according to FIG. 1 expediently in a housing 34 with control buttons, for. B. a button 35 can be accommodated. The pump 15 can rest on a table 31 or the like located next to the hospital bed, with it between the upstream and downstream parts 11 or 13 of the delivery line is switched on. Feedthroughs 41 form the inlet and outlet to and from from the housing 33 for the two line parts 11 and 13, respectively.

In the device according to the invention, a removable or exchangeable cassette 18 is located in the pump 15 intended. The cassette used in the device according to the invention does not require any valves, so that the structure of the device is considerably simplified and the cost of its replaceable part can be reduced considerably. In addition, the device according to the invention uses a cassette in which a comparatively large displacement with each delivery stroke

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takes place. This delivery stroke displacement is at the device according to the invention preferably at least about 0.25 ml.

The cassette itself is shown in more detail in FIG. It basically only consists of three parts. The main part is a molded housing 43 made of a medical grade plastic. The outline of the Housing is essentially circular with slightly square but rounded corners. A Connector 23 is used to connect the upstream Line part of the infusion device, while a provided on the opposite side of the housing 43 Connector 24 is used for connection to the downstream line part. In contrast to many previous ones Cassettes of this type do not contain these nozzles. The housing 43 defines a pump or delivery space 25 fixed, which is substantially cylindrical and has an open side. An annular groove 45 runs around the open side of the delivery chamber and serves to accommodate an annular lip 47 of a flexible membrane 26. The membrane 26 consists of a flexible or elastic material suitable for medical purposes, the is impermeable to the liquid or semi-solid substances to be conveyed and the one to be described

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- η *

Way can be bent or deflected to a sufficient extent to achieve the desired one, which is also still to be described To bring about repression. To hold the flexible membrane, a retaining ring 49 is in one of the housing 43 protruding annular lip 51 fitted and perfect, for example by ultrasonic welding sealed against the housing, so that this retaining ring produces a seal and at the same time the membrane 26 holds in a position in which it spans the open side of the conveying space 25.

As mentioned, constriction or throttle elements 21 and 22 are provided to the upstream and the to narrow and open the downstream line part 11 and 13 alternately in such a cycle sequence, that some kind of valve action is brought about by means of which the fluid from the upstream Line part 11 to the downstream line part 13 can be promoted. Although any suitable elements can be used for this purpose, consist in the device shown in Figures 3 and 4, the throttle elements 21 and 22 from each other tapered or conical ends of displaceable rods 63 and 65. The rods are not shown Way inside the housing 34 of the pump

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movably guided. The rounded tips of the conical ends 21 and 22 of the rods 63 and 65 are standing with the upstream or downstream line part 11 or 13 in contact. The line parts are in assigned grooves or recesses a chassis 16 guided inside the housing 34 of the pump 15, above the chassis 16 is a sleeve arranged that a seal between the concerned Manufactures part of the cassette 18 and the drive device to be described.

The actuator 28 comprises the rounded end of an elongated rod or an elongated one Rod 67, which is guided movably in a suitable carrier, not shown, on the chassis 16. The rounded tip of the actuating device 28 or the rod 67 presses over the. open side of the Conveying space 25 of the cassette 18 against the membrane 26. If the cassette is properly inserted, steers the actuating device 28 moves the membrane 26 slightly inwards, even in the fully retracted state, so that it is in constant contact with the membrane during the entire delivery stroke. The volume of the conveying space in this fully retracted state, the rod 67 represents its maximum working volume

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Inward displacement of the rod 67 becomes the membrane according to FIG. 4 while reducing the volume of the conveying space 25 shifted inwards or deflected.

The pump 15 has a hinged flap 27 which can be opened for insertion and removal the cassette 18 and the sections of the two line parts to be arranged within the pump housing 34 11 and 13 to enable. When the flap 27 according to Fig. 3 and 4 is closed, pushes a helical spring 55 in a recess 57 of the flap, which in turn is covered with a plate 59, a preload cup 61 against the cassette housing 43 to to hold this in its installed position against the chassis 16. On the flap 27 are with the help of adjusting screws 66 and 68 pressure blocks 62 and 64, respectively. The pressure block 62 is located on that of the rod 21 opposite side of the upstream line part 11. Similarly, the pressure block is on the opposite side of the rod 22 downstream line part 13 is arranged. With the appropriate setting of the position of the pressure blocks 62 and 64 by means of the adjusting screws 66 and 68, the throttle elements can be used in the operation to be described below 21 and 22 exerted pressure in the manufacturer's works like this

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be set so that a complete disconnection of the hose and thus a complete closure the same is ensured.

To move the throttle elements 21 and 22 and the actuating device 28 in the intended sequence carry the ends of the displaceable rods 63, 65 and facing away from the cassette and the line parts 67 suitable curve sensor 71, which by springs (not shown) against the circumferential surfaces of cams 91, 93 and 95 are preloaded. The latter are mounted on a camshaft 97 driven by a drive motor 103 can be set in rotation. The drive motor is a so-called stepper motor that drives the camshaft Gradually rotated and thus a gradual movement and control over the sliding Poles exercising.

According to FIG. 3, the lower or second throttle element 22 is in a position in which it is the downstream able to pinch flexible line part 13. Due to the way to be described in the The suction effect (negative pressure) exerted in the reverse movement of the actuating device 28 becomes the conveying space 25 the cassette 18 is filled. In the one shown in FIG

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Delivery stroke, the second throttle element 22 is withdrawn with the line part 13 fully open, while the first throttle element 21 is advanced to close or clamp off the upper line part 11 is. During the inward or outward movement of the actuating device 28, the volume of the conveying chamber becomes 25 reduced so that a predetermined amount of the content to the downstream line part of the conveyor system is expelled. The distance of the extension movement of the actuating device 28 determines this Displacement volume with each delivery stroke. The filling and Conveying strokes take place in cycles in succession Depending on the rotation of the camshaft 27 and the configuration of the cams 91, 93 and 95.

Fig. 5 graphically illustrates the relationship between movement or displacement Camshaft rotation for the three sliding rods 63, 65 and 67. At the left end or in the 0 ° position In the diagram, the upper rod 63 is extended (to close) while the rods 65 and 67 (to open) are withdrawn. When the rod 67 moves from the open position to the closed or An exactly predetermined volume of the contents of the conveying chamber 25 is displaced. Thereupon

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31QA985

The rod 65 pushes itself into the closed position in order to clamp off the line part 13 on the downstream side. At the same time the rod 67 moves into the open position. Due to the elasticity of the membrane, this takes place an expansion of the conveying space volume. The rod 63 begins to move to the open position after the rod 67 has withdrawn over about 20% of its total stroke, so that the conveying space is again can fill. At about 270 ° the rod 63 on the upstream side moves from the open position to the closed position, and following this, the downstream rod 65 moves to the open position. Here the device returns to its initial state for the next displacement stroke at 0 °. Since the rod is the actuator, i.e. H. the plunger 28, before the open the upstream part of the line for practical purposes retracts a complete increase in the volume of the conveying chamber, backfilling of the drip chamber is avoided. The term "practically complete" means a sufficiently large movement in which the largest expected expansion of the air in the pumping chamber can take place. It turns out that a roughly 20% increase in the volume of the pump chamber before opening the upstream line part in general is satisfactory.

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In typical applications, the device according to the invention works with maximum pressures of about 1.75 bar. The "stiffness" of the cassette 18 is therefore chosen accordingly. The actuating device preferably engages (Plunger) over the entire stroke on the membrane, so that there is always a slight inward load on the Membrane is present. To ensure satisfactory delivery or metering accuracy, it is preferred that the non-impacted or non-contact surface section of the membrane not more than 75% of the total Membrane or window area.

Instead of the illustrated cam drive, other devices for actuating the throttle elements can also be used can be used, for example a worm or screw drive. A step by step or clockwise However, control of the diaphragm movement is essential to achieve the desired accuracy and control. A desired displacement volume can be set for each work cycle by means of a suitable design will. This is a digital control by means of commercially available and comparatively cheap microcomputer chips easily possible. Functions such as flow rate, total delivery volume and flow error monitoring, can easily be known per se

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-η

Digital technology can be provided.

In general, the device is preferably designed so that the retraction and retraction strokes of the rods 63, 65 and 67 take place for the same duration, regardless of the delivery rate and volume. The current can therefore be made uniform when the operation smitte1 at a comparatively high, fixed speed be withdrawn, which is in contrast to a change in the supply amount. Such The way of working can easily be realized by means of digital technology.

The size of the outlet and inlet openings in relation to the diaphragm size is also important. if
The inlet and outlet openings are too large, the back displacement (regurgitation) reaches such a size that the delivery or metering accuracy is adversely affected. For this reason, the ratio of the cross-sectional area of the inlet and outlet openings to the membrane or window area is preferably no more than about 0.3.

As in the case of any cassette pump unit, it can
Presence of air in the cassette reduces the accuracy

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affect the delivery rate. To avoid such Problems are combined with one another in the device according to the invention, two features that have in common Significantly improve the delivery and metering accuracy. On the one hand, namely, the rod 67 is in a partially (about 20%) retracted position moved before the upstream line portion by retracting the rod 63 is opened. This prevents the air expanding in the pumping space from lowering the liquid level increased in the drip chamber. On the other hand, the remaining volume of the delivery chamber is fully extended Rod 67 (by selecting the stroke length and the geometry of the conveying chamber accordingly) to less than about 0.07 ml and preferably adjusted to 0.05 ml. Contains the tubing between the cassette and the pinch-off points preferably an additional volume of air of (only) 0.1 ml, so that the total amount of trapped Air is 0.17 ml. With these proportions the enclosed air has only a tolerable influence on the flow accuracy. One in the The amount of air present in the cassette, which exceeds the remaining volume plus the tube volume, is removed from the Cassette driven out and can, if this amount of air is too large, be determined in an appropriate manner.

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In addition to the described advantages guaranteed the medical infusion device according to the invention in comparison to various previous designs this kind of other significant advantages. With appropriate design of the cams and the size of the Slidable throttle elements can perfectly constant flow rates down to extraordinarily small flow rates can be achieved. For example, the infusion device according to the invention is shown in FIG Location, a flow rate of 1 ml per hour with a partial or clock delivery in each 26 seconds and a filling time of only 1 second.

Various changes and modifications to those presented above will of course be apparent to those skilled in the art and described embodiment of the invention obviously, hence the invention includes all changes and modifications within the expanded scope should include.

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Claims (6)

Patent claims: 1 .J Medical infusion device for conveying liquid or semi-solid substances from an upstream or upstream flexible line part of the infusion system to a downstream or downstream flexible line part of the same, characterized by a pump (15) with means for holding the line parts (11, 13 ), by a first constriction or throttle element (21) for selective clamping and opening of the upstream line part (11), by a second constriction or. Throttle element (22) for the selective disconnection and opening of the downstream line part (13), through a cassette (8) with means (23, 24) for connecting the two line parts (11 or 13), the cassette defining a conveying space (25) and a flexible membrane (26) delimiting part of the pumping chamber, through means provided on the pump (15) for releasably or removably holding the cassette (18) in a position between the upstream and downstream line parts (11 or 13) an actuating device (28) which acts on the membrane and which at a 130052/0562 Displacement from a fully retracted position to a fully advanced position is a predetermined one Able to displace fluid volume in the delivery chamber (25), this predetermined volume being selected is that in the conveying space (25) a residual volume of less than about 0.07 ml remains, and by a Device (29) for actuating the two throttle elements (21, 22) and the actuating device (28) in one for the conveyance of the liquid or semi-solid substances from the upstream line part to the downstream line part provided clock sequence, which is determined so that the actuating device (28) for practically complete expansion of the volume of the conveying chamber (25) into the full retracted position shifted before the upstream line part (11) through the first throttle element (21) is opened. 2. Infusion device according to claim 1, characterized in that the predetermined volume is at least is about 0.25 ml. 3. Infusion device according to claim 1, characterized in that that the connection means (23, 24) and the lines (11, 13) between the conveying chamber (25) and 1300S2 / OS62 Throttle elements (21, 22) define a volume adjoining the delivery space, and that this volume and the remaining volume of the delivery space (together) is less than about 0.17 ml. 4. Method of operating a medical infusion device for conveying liquid or semi-solids from an upstream flexible Line part of the infusion system to a downstream flexible line part thereof, the Infusion device means for holding the line parts, a first throttle element for selective Narrowing and opening of the upstream line part, a second throttle element for selective Narrowing of the downstream line part, a cassette with means for connecting the two line parts and with a delivery space, one part of which is delimited by a flexible membrane the pump provided means for releasably or removably holding the cassette in one position between the upstream and downstream line part, an actuating device (tappet), which is able to act on the diaphragm and when moving from a fully retracted position in a fully advanced position a pre- 1300S2 / 0562 correct volume displaced in the delivery chamber, and devices for actuating the two throttle elements and the actuating device, characterized in that the two throttle elements and the actuating device can be controlled in such a cycle that the liquid or semi-liquid Fluid is conveyed from the upstream line part to the downstream line part, wherein the predetermined volume is dimensioned so that a residual volume of less than about 0.07 ml in the delivery chamber remains behind, and wherein the clock sequence is chosen so that the actuator is in the fully retracted Moves position to practically complete enlargement of the volume of the pump chamber, before the upstream line part is opened by moving the first throttle element. 5. The method according to claim 4, characterized in that the predetermined volume is at least about 0.25 ml amounts to. 6. The method according to claim 4, characterized in that the connection means and the line parts between the delivery space and the throttle elements define a volume adjoining the delivery space, which 130062 / QS62 together with the remaining volume of the conveying chamber is less than about 0.17 ml. 130052/0562