RU2575307C2 - Infusion pump with metering mechanism of cylinder and piston and optical detection of piston position - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: group of inventions refers to medical equipment. In a metering mechanism, a piston has a piston head and piston rod having a segment provided with labels in the form of a number of optically detectable strips on the segment. The metering mechanism comprises a valve configured in two working positions, and a window on the cylinder to ensure an optical access to the optically detectable strips. The optical access window is configured so that it ensures the optical access to the optically detectable strips when the valve is found in one of its working positions, and does not ensure the optical access to the optically detectable strips when the valve is found between the two working positions. Disclosed is an infusion pump with this metering mechanism.

EFFECT: group of inventions solves a problem of providing higher metering accuracy.

9 cl, 8 dwg

Description

Technical field

The invention relates to metering devices for infusion pumps, infusion pumps with such metering devices, and methods of operating such infusion pumps, according to the restrictive part of the independent claims.

BACKGROUND OF THE INVENTION

Devices for the automated release of liquid medicines are usually used by patients who have a constant, and changing throughout the day, need for a liquid medicine that can be administered by infusion. Specific applications include, for example, the treatment of certain pains, cancer therapy and diabetes mellitus, which use computer-controlled infusion pumps. Such devices are used primarily for outpatient treatment and, as a rule, they are worn attached to the body or near the body of the patient. A medicine reservoir often contains enough medicine for one or several days. A liquid medication is injected into the patient’s body from a reservoir with a medicine through an infusion cannula or injection needle.

Ambulatory infusion pumps are typically syringe-type pumps, such as, for example, disclosed in WO 01/83008 A1 and schematically described in FIG. 1 (a). The liquid medication to be administered to the patient 32 is stored in the cylinder 14 of the metering device 10, which contains a full reservoir 11 of the liquid medication of the infusion pump. The liquid medication is delivered to the patient’s body 32 by unidirectionally moving the piston 16 inside the cylinder by means of a piston rod 18 or a threaded spindle. The outlet 25 is hydraulically connected to the infusion tube 28, which at its other end is hydraulically connected to the infusion site interface 30 attached to the body. For safety reasons, it is generally preferable to regularly replace any parts that come in contact with a liquid medication, such as an infusion tube, for example. In most cases, the reservoir is a disposable cartridge that may be pre-filled in stock or may be empty and refilled by the user.

A number of disadvantages of such syringe-type pump designs are known in the art. First of all, such pumps have limited accuracy because very small volumes, usually in the nanoliter range, are pumped out of the cartridge having a total volume in the milliliter range. To achieve the exact dosage of the liquid medication, it is necessary to move the piston very accurately. Even small deviations can lead to an overdose or insufficient dosage, and the forces required to actuate the piston are relatively high due to friction between the walls of the glass cartridge and the piston seal, and hysteresis of the seal material. This leads to high demands on the drive system and used mechanical parts, as well as the pump control unit. As a result, such infusion pumps are expensive.

Another problem is the lower length limit of such an infusion pump. The full supply of liquid medication should be stored in a cartridge that acts as a pump cylinder. The piston cross-sectional area must be below a certain limit, for reasons of accuracy and in order to limit the thickness of the device, which is known to be a particularly critical size in terms of convenience and caution during use. Then the minimum total length of the device is essentially determined by the resulting minimum length of the cylinder, which is detrimental to the implementation of compact infusion pumps. First of all, when self-administering medications, such as insulin, patients using the medication in question and administering it on their own with the help of an infusion pump attach greater importance to convenience and care, which limits the acceptable size and weight of such devices so as not to be visible through clothing and carried as convenient as possible.

In alternative approaches, a separate metering device is provided downstream of the liquid medication reservoir. Since the primary tank does not have to perform additional functions, its size can be optimized in terms of compactness of the infusion pump. Such a dispensing device may, for example, comprise a small piston micropump that extracts liquid medication from a larger primary reservoir, such as a compliant reservoir, and delivers the liquid medication to the patient's body. Such pumps, as a rule, are full-flow pumps, where the cavity of the diaphragm pump or the cylinder of the piston pump is always completely empty. Therefore, the internal volume of the pump should correspond to the smallest increase in volume that can be supplied, usually in the nanoliter range. Although several designs of such metering devices are known from the prior art, they are quite complex, expensive and critical for large-scale production, as they include a number of functional components, primarily metering components and valves, and are often made of materials that are expensive and / or are critical in the manufacture and processing, for example silicon. Since it is preferable to sell all the parts that come into contact with the liquid medication, including the pump, as disposable items that are replaced after a certain time, such pump designs are expensive. Thus, it is favorable that all the expensive parts of the metering device are recyclable and the disposable parts are manufactured at a lower cost.

US 2004/0044332 A1 discloses an implantable infusion pump with a primary reservoir in the form of an elastic bellows, a channel hydraulically connecting said channel with a variable volume chamber in the form of an elastic bellows, a valve with which the channel can be opened and closed, and a downstream catheter hydraulically connecting the variable volume chamber to the infusion site. The volume of the chamber of variable volume is much smaller than the volume of the primary tank. Two limiters are arranged so as to limit the change in volume of the chamber of the variable volume between the lower limit of the volume and the upper limit of the volume. In the first stage, the elastic reservoir is filled with a syringe, the valve being closed. Starting from a certain degree of expansion of the elastic reservoir, the restoring force of the latter is such that the fluid can be expelled into the channel. When the valve is open, fluid flows towards the variable volume chamber, driven by the pressure drop in the primary reservoir. As soon as the upper limit of the volume of the chamber of variable volume is reached, the valve closes and the liquid is transported by the restoring force of the chamber of variable volume to the catheter located downstream and to the place to be treated. When the chamber of variable volume reaches the lower limit of the volume, the liquid is no longer displaced from it. At the end of a certain period of time, determined depending on the desired dose rate, the valve opens again and the process described above is continuously repeated. In other words, the device’s primary reservoir acts as a spring-driven syringe pump with a constant dose rate. The intensity of the introduction is controlled by the time intervals between the temporary opening of the valve, each corresponding to the full stroke of the spring-driven secondary piston pump in the form of an elastic chamber of variable volume, and the positions of two stoppers that control the volume per stroke.

Although it is claimed that the metering accuracy in such a device is high, this accuracy is based on a statistically average value. The volume of single introduced portions cannot be adjusted; only the average intensity of administration can be changed. As a result of this, such a device cannot be used for dosage regimens, as they are necessary for the treatment of diabetes mellitus, in which the administered dose of each single portion of insulin must be adapted to the current needs of the patient.

Using such a device is even potentially dangerous, especially when using very strong drugs, such as insulin. Although it is proposed to use controlled valves in both channels to avoid the known problem of temporary bypass between the primary reservoir and the catheter during filling of the variable volume chamber, a malfunction of these valves would lead to an unlimited and uncontrolled flow of liquid medication from the primary reservoir directly to the catheter. However, even the possibility of such an event must be prevented at all costs.

In yet another approach, the piston pump cylinder of the metering device acts as a secondary reservoir and may contain an intermediate amount of liquid medicament. The pump extracts the liquid medication from the primary reservoir and supplies the medication in variable doses. This compromise allows to reduce the overall dimensions of the device, and at the same time, doses in variable quantities can be obtained.

A device in accordance with this approach is shown, for example, in DE 3515624 A1, where a flexible secondary reservoir of variable volume is hydraulically connected by a first channel to a flexible primary reservoir and a second channel with an infusion catheter. The volume of the second tank, for example 100 l, is chosen between the volume of the primary tank, for example 10 ml, and the volume of the smallest dosing portion, for example 1 l. A valve is located in each channel to control the correct flow of fluids during filling of the secondary tank and during dosing. Valves are either non-return valves that allow fluid to flow only in the intended direction, from the primary reservoir to the secondary reservoir during filling and from the secondary reservoir to the catheter during dosing, or electrically controlled valves that open and close as needed to achieve such a function.

The use of such a device is also potentially dangerous, especially when using very strong drugs, such as insulin. If valves are used, any excess pressure in the primary reservoir directly leads to an unrestricted and uncontrolled flow of liquid medication from the primary reservoir through the second chamber to the injection site. The same thing happens if, for some reason, the electrically operated valves fail and both are open at the same time. Since this problem is known, DE 3515624 A1 explicitly states that the pressure inside the primary tank should in no case be higher than the ambient pressure. However, it is obvious that such a precondition for the safe operation of the device cannot be guaranteed. Especially if for some reason a certain amount of air is present in the primary reservoir, any increase in ambient temperature or a decrease in ambient pressure will inevitably lead to overpressure in the primary reservoir.

A favorable embodiment of this type of infusion pump is described in Applicant EP 1970677 A1 and is shown schematically in FIG. 1 (B). A 4/3-way or 3/3-way valve 35 is located on the front end of the cylinder 14 of the metering device 12. The valve is implemented as a rotatable cylinder head acting as a valve element that interacts with a fixed cylindrical tube acting as a valve seat. The piston 16 located in the cylinder of the metering device can be moved in two directions along the axis of the cylinder using the drive system 20. In the refill mode, when the metering device takes the piston back and draws liquid medication from the primary reservoir 11 into the cylinder 14, the inlet channel 24 is hydraulically connected with the primary tank, hydraulically connected to the cylinder, and the outlet channel 25, hydraulically connected to the infusion tube 28, is disconnected from the metering device. In the injection mode, when the liquid medication is supplied from the secondary reservoir 15 in the cylinder of the metering device into the subcutaneous tissue of the patient 32, the cylinder 14 of the metering device is hydraulically connected to the outlet channel 25, thereby establishing a hydraulic connection with the patient’s body, while the inlet valve 24 is disconnected from the dosing device.

Alternatively, the rotating cylinder may act as a valve element mounted in a fixed valve seat. A particularly advantageous embodiment of the latter embodiment is disclosed in the applicant's EP 2163273 A1, where the piston drive means indirectly actuate the valve element due to the rotation of the cylinder, which is frictionally connected to the piston.

For accurate dosing, you must either use a pump motor that can be controlled very accurately, such as a stepper motor, or control the actual position of the piston.

WO 2011/032960 A1 discloses methods for monitoring the position of a movable stopper in an insulin ampoule. In one approach, the movable stopper is provided with marks, such as visual marks, that can be detected by sensors located along the ampoule. To accurately determine the position of the stopper, a large number of sensors are required. The cylinder wall should be at least partially transparent so that the sensors can see visual marks.

EP 2201973 A1 discloses a syringe-like injection canister device, where the piston rod is provided with optical marking, namely, numbers that can be visually detected by the user through an opening in the housing. By reading the number in the hole, the user can control the position of the piston in the syringe to determine the administered or remaining dose. For an automated system, this approach is not accurate enough.

US 2008/0077081 A1 discloses an infusion pump with a cylindrical pump having a longitudinally movable piston with a detachable piston rod that connects the piston head to a threaded nut. The piston cannot rotate. A threaded nut interacts with a rotating threaded drive shaft, thereby converting the rotation of the drive shaft into linear movement of the piston head. One or more detectable elements, such as magnetic or optical marks, can be located on the piston rod, which can be detected by a suitable sensor to determine the linear position of the marks, and thus the piston head.

The accuracy of determining the position is limited by the accuracy of determining the linear position of the mark.

FR 2185790 discloses a cylindrical pump in which a wheel interacts with a piston rod during linear piston movement. Thus, the linear movement is converted to rotation of the wheel, and then to the rotation of the second wheel with many radial lines. This wheel is illuminated through a transparent plate, which is also provided with many radial lines. One sensor detects incident light. In addition to the complex design of such a device, with many moving parts, the achievable accuracy is essentially reduced by frictional slippage between the wheel and the piston rod.

In the worst case scenario with a pump failure, the entire contents of the tank may be inadvertently entered as a result of continuous and unintended operation of the pump, for example, due to a malfunction in the drive control circuit. Although in the favorable infusion pump discussed above, the maximum dispensing volume in the secondary reservoir is significantly less than the full contents of the cartridge of a conventional syringe pump, for example 25 times, the liquid medications that are injected with the liquid infusion pumps are generally highly effective and unintentional the introduction of the entire secondary reservoir is undesirable.

Another problem with infusion pumps is air bubbles in the hydraulic system, especially in the pump system, but also in other components, such as the container. If air bubbles remain in the hydraulic system, they can be introduced instead of the liquid medication, which leads to undesirable dosage errors. In addition, the introduction of air into the patient's body should generally be prevented for medical reasons.

And another problem resulting from the presence of air in the hydraulic system is the reduced rigidity of the hydraulic system due to the high compressibility of gases with respect to liquids such as water. This makes it difficult to detect blockages or blockages in the hydraulic system by controlling fluid pressure.

A syringe-type pumping system for liquid distribution grids for multi-well plates is disclosed in EP 1754505 A1. Said syringe pump comprises a cylinder and a movable plunger, a first inlet channel hydraulically connected to the fluid reservoir and a second outlet channel connected in the direction of the dispensing tip. A three-way distributor alternately connects the first channel and the second channel to the pump cylinder for refilling and for distribution, respectively. Syringes are mounted vertically to allow air bubbles in the pump cylinder to rise up to the outlet port to the second channel, so that they can be removed from the hydraulic system during the filling procedure, by transporting them through the second channel and from the dispensing tip. In order to prevent the accumulation of air bubbles that were involved in the volume of the pump cylinder during the first filling stage of the filling procedure, in the dead volume between the pump cylinder and the valve and returning to the cylinder volume in the next stage of filling the filling sequence, the dead volume is reduced to a minimum. For this, the channel length between the valve and the cylinder is minimized. Thus, fewer air bubbles can accumulate in dead volume. In particular embodiments, special valves are additionally used, with a valve element that provides two different internal channels, one channel connecting the first channel to the cylinder in the first state, and a second channel connecting the second channel to the cylinder. Thus, the air bubbles remaining in the second channel after the first filling cycle of fluid involvement in the cylinder and the displacement of the specified fluid through the dispensing tip are not again drawn into the cylinder during the second filling cycle.

Filling the open syringe pump includes at least two filling cycles of filling the pump cylinder and removing liquid through the outlet channel. Filling the open pump only works if the pump is in a deliberate orientation, since the correct path of the air bubbles during the filling procedure is set by the direction of the buoyancy force in combination with the geometry of the pump elements.

In cases where the atmospheric pressure of the environment changes, especially if it drops, in a short time, for example, as a result of rapid changes in height when moving in elevators or in mountainous areas or as a result of airtight cabin sealing, air present in the metering device or in the infusion tube will expand. As a result, an additional dose of liquid medication is displaced from the hydraulic system into the patient's body. A similar effect can occur in the event of a change in temperature.

Since the health of the patient is of paramount importance and should be protected at all costs, accordingly, there is a need to further improve the safety level of all infusion pumps known in the art.

OBJECTS OF THE INVENTION

The aim of this invention is to provide an improved metering device and an infusion pump having such a metering device that overcomes one or more problems of the prior art and minimizes dosing errors caused by various reasons.

Another objective of the invention is the creation of a favorable metering device and an infusion pump with such a metering device, which minimizes the possible error of the maximum dosage and allows you to accurately meter the liquid medication. Such a metering device must be reliable and must be manufactured in high quality at low cost in large-scale production.

Another objective of the invention is to provide a favorable method for operating the infusion pump, especially for filling the hydraulic system of the infusion pump before the infusion operation, which minimizes the amount of air in the hydraulic system, thereby reducing dispensing errors.

Another objective of the invention is to create a favorable method of operating an infusion pump, especially for dispensing one or more doses of a liquid medicine in an infusion pump, thereby reducing dispensing errors.

According to the present invention, these and other objects are achieved by the features of the independent claims. In addition, additional favorable embodiments follow from the dependent claims and descriptions.

SUMMARY OF THE INVENTION

The present invention may contain one or more of the features indicated in the attached claims, and / or one or more of the following features and their combinations.

The favorable metering device according to the disclosure for an outpatient infusion pump has a cylindrical pump comprising a cylinder and a piston slidably disposed in said cylinder. The piston is operationally connected to the cylinder and can move along the longitudinal axis of the cylinder. The piston comprises a scale, the scale being designed to interact with the sensor and provide a displacement signal, the displacement signal being indicative of displacement of the piston relative to the cylinder. Advantageously, the piston has a rod with a first threaded segment interacting with the threaded portion of the cylinder. The piston of the metering device can advantageously be moved along the longitudinal axis of the cylinder due to the rotation of the piston relative to the cylinder around the specified axis.

In yet another favorable embodiment of such a metering device, the piston comprises tags that can be detected optically, magnetically or electrically.

In yet another advantageous embodiment of such a dispensing device, the piston rod comprises a second segment provided with optically detectable marks that allow the longitudinal and / or rotational movement of the piston relative to the cylinder to be controlled.

In a particularly favorable embodiment of such a dispensing device, optical marks are provided as a plurality of circumferential rings located on the second segment of the stem, said optical marks being optically distinguishable.

Advantageously, the second segment is located between the first threaded portion and the piston head, or, alternatively, the second segment is at least partially overlapped with the first threaded portion.

In yet another embodiment of such a metering device, a window is provided on the cylinder that provides optical access to at least a portion of the second segment of the piston rod.

In yet another embodiment of the metering device according to the disclosure, the piston comprises means that modulate the frictional force between the piston and the cylinder during the movement of the piston.

A particularly favorable embodiment of the metering device considered so far comprises a valve for alternately connecting the internal volume of the cylinder in the first state with the inlet channel and in the second state with the exhaust channel. The valve comprises a valve seat and a valve member, the valve member being implemented as part of the cylinder. The cylinder is mounted to rotate or slide in the support of the valve seat, so that the valve can switch between the two states by rotating the cylinder with the valve element a certain angle along the longitudinal axis, or by moving the cylinder with the valve element relative to the valve seat a certain distance along the longitudinal axis.

Another particularly favorable variant of the metering device considered so far comprises a valve, which can be in two operating states, and a window is provided on the cylinder for providing access to the scale on the piston, the optical access window being configured to provide access to the scale when the valve is in one of two operating states, and does not provide access to the scale when the valve is between two operating states.

A particularly favorable metering device according to the disclosure for an ambulatory infusion pump has a cylindrical pump comprising a cylinder and a piston adapted to move along the longitudinal axis of the cylinder. The piston has a piston head and a piston rod. The piston rod has a segment provided with marks that can be detected optically or magnetically or electrically, the marks being provided in the form of a plurality of strips located on the second stem segment along the stem circumference and parallel to the longitudinal axis.

In another alternative favorable embodiment of such a metering device, the marked segment of the rod is labeled with a plurality of circumferential rings located on the second segment of the rod along the longitudinal axis.

Advantageously, in such metering devices, the tags are optically detectable bands.

A particularly favorable embodiment of such a metering device comprises a valve, which can be in two operating states, and a window provided on the cylinder to provide optical access to optically detectable bands. The optical access window is designed so that it provides optical access to the optically detectable bands when the valve is in one of two operating states, and does not provide optical access to the optically detectable bands when the valve is between the two operational states.

In particularly advantageous embodiments of the metering devices in question, the piston rod comprises a threaded segment that interacts with the threaded portion of the cylinder so that the piston moves along the longitudinal axis when the piston rotates around the axis.

Such a metering device makes it possible to accurately determine the linear movement of the piston without the need for high-precision sensor elements or marks. The relationship between the angle of rotation and linear displacement is determined by the design of the dosing device and is therefore precisely known. Since the relatively large angle of rotation of the piston corresponds to a relatively small linear displacement or, accordingly, the volume of dosing, a relatively rough distribution of marks along the perimeter of the rod corresponds to a fine detection grid along the linear axis.

Advantageously, the second marked segment of the metering device is located between the first threaded segment and the piston head.

Additionally or alternatively, the second marked segment is at least partially superimposed on the first threaded segment.

The dispensing device according to the disclosure may be provided with a valve for alternately connecting the internal volume of the cylinder in the first state with the inlet channel, and in the second state with the exhaust channel. Said valve comprises a valve seat and a valve element, wherein the valve element is implemented as a cylinder part and the cylinder is rotatably or slidably mounted in the support of the valve seat, so that the valve can switch between two states by turning the cylinder with the valve element a certain angle along the longitudinal axis of the cylinder, or by moving the cylinder with the valve element relative to the valve seat a certain distance along the longitudinal axis.

Another particularly advantageous dispensing device according to the disclosure for an ambulatory infusion pump has a cylindrical pump comprising a cylinder and a piston arranged to move along the longitudinal axis of the cylinder, the piston being provided with optically detectable marks that allow determining the absolute position of the piston inside the cylinder and / or relative displacement inside the cylinder. The metering device comprises a valve, which can be in two operating states, and a window provided on the cylinder to provide optical access to optically detectable tags. The optical access window is designed in such a way that it provides optical access to the optically detectable tags when the valve is in one of two operating states, and does not provide optical access to the optically detectable tags when the valve is between two operational states.

Such a metering device gives, for example, the advantage that the detection of the movement of the piston can be turned off in a simple and trouble-free manner while the valve is not in operation. Another advantage is the indirect control of the correct valve position. If the pump is activated and the movement of the piston is not detected, this may be the result of the valve not in working condition. In this case, the insertion process may be interrupted and a malfunction message may be issued by the control system.

In one favorable embodiment of such a metering device, the piston rod has a marked segment on which optical marks are provided in the form of at least two bands located on the second rod segment along the stem perimeter and parallel to the longitudinal axis.

In an alternative favorable embodiment of such a metering device, the piston rod has a marked segment on which the optical marks are provided in the form of a plurality of optically distinguishable circumferential rings located on the second segment of the rod.

In a particularly favorable embodiment of such a metering device, the piston comprises a piston head and a piston rod with a threaded segment cooperating with the threaded portion of the cylinder so that the piston moves along the longitudinal axis when the piston rod rotates about the axis.

Advantageously, the second marked segment of the metering device is located between the first threaded segment and the piston head.

Additionally or alternatively, the second marked segment at least partially overlaps the first threaded segment.

The dosing device described above advantageously comprises a valve for alternately connecting the internal volume of the cylinder in the first state with the inlet channel and in the second state with the exhaust channel. Said valve comprises a valve seat and a valve element, wherein the valve element is implemented as a cylinder part, and wherein the cylinder is rotatably or slidingly mounted in the valve seat bearing so that the valve can switch between two states by rotating the cylinder with the valve element a certain angle along the longitudinal axis of the cylinder or by moving the cylinder with the valve element relative to the valve seat a certain distance along the longitudinal axis.

The favorable infusion pump according to the disclosure comprises a dispensing device according to the disclosure discussed so far, or is designed to receive such a dispensing device.

A favorable embodiment of such an infusion pump comprises one or more sensors that can detect piston marks of a metering device installed in the infusion pump, and an evaluation device that, based on a signal received from one or more sensors, can determine the absolute position of the piston inside the cylinder of the metering device and / or relative displacement of the piston inside the cylinder.

In a particularly favorable embodiment of such an infusion pump, the piston marks of the metering device installed in the infusion pump are optical marks. The metering device comprises a valve, which can be in two operating states, and a window provided on the cylinder, which provides optical access to the optical marks of the piston. The optical access window and one or more sensors of the infusion pump are arranged so that one or more sensors have optical access to the optical tags when the valve is in one of two operating states, and do not have optical access to the optical tags when the valve is between two working conditions.

Another embodiment of such an infusion pump comprises a sensor that can detect the scale of the piston of the metering device installed in the infusion pump, thereby obtaining a signal that is indicative of movement of the piston relative to the cylinder of the metering device.

Another embodiment of the infusion pump according to the disclosure comprises an optical sensor for detecting marks on the piston rod of the metering device.

The kit according to the disclosure comprises an infusion pump according to the disclosure discussed so far and one or more metering devices according to the disclosure discussed so far.

Another favorable embodiment of the infusion pump according to the disclosure has a primary reservoir for a liquid medicament, a pump with a secondary reservoir that can take the fluid medicament from the primary reservoir and then dispense the liquid medication from the secondary reservoir in incremental steps, a first upstream channel hydraulically connecting the primary reservoir to pump, the second channel downstream, hydraulically connected to the pump for transporting the liquid medication to the interface of the injection site, valve, cross Menno connecting the pump with one of the two channels, and a control unit configured to control the operation of the infusion pump. To fill the hydraulic system of the infusion pump with a liquid medicine before the infusion operation, the control unit forces the infusion pump to perform the following steps: (a) bringing the pump to its original state when the internal volume of the secondary tank is minimal; (b) switching the valve to a first state in which a secondary reservoir is connected to the first channel and the primary reservoir; (c) recovering the liquid medicament from the primary reservoir, wherein the volume V _{C of the} recovered liquid is at least equal to the internal volume V _{B of the} first channel upstream; (d) switching the valve to a second state in which the second reservoir is connected to the second channel downstream; (e) displacing the contents in the secondary reservoir into the second channel downstream; (e) switching the valve to a first state; (g) recovering the liquid medicament from the primary reservoir, wherein the volume V _{C of the} recovered liquid is at least equal to the internal volume V _D + V _E + V _{F of the} second channel downstream; (h) switching the valve to a second state; and (i) displacing the contents in the secondary tank into the second channel downstream by moving the piston to its original position.

A particularly advantageous embodiment of such an infusion pump according to the disclosure has a primary reservoir for a liquid medication, a pump with a secondary reservoir that can extract the liquid medication from the primary reservoir and then dispense the liquid medication from the secondary reservoir in incremental steps, a first upstream channel hydraulically connecting the primary reservoir to pump, the second channel downstream, hydraulically connected to the pump for transporting liquid medication to the interface of the injection site, the valve for I alternately connect the pump to one of the two channels and a control unit configured to control the operation of the infusion pump. To fill the hydraulic system of the infusion pump with a liquid medicine before the infusion operation, the control unit forces the infusion pump to perform the following steps: (a) bringing the pump to its original state when the internal volume of the secondary tank is minimal; (b) switching the valve to a first state in which a secondary reservoir is connected to the first channel and the primary reservoir, and extracting a volume of liquid medicament from the primary reservoir; (c) switching the valve to a second state in which the secondary reservoir is connected to the second channel downstream, and displacing the contents in the secondary reservoir to the second channel downstream; and (d) switching the valve to the first state and extracting the volume of liquid medicament from the primary reservoir; and (e) switching the valve to a second state; and displacing the contents in the secondary tank into the second channel downstream. The extracted fluid volume V _Up in step (b) is at least equal to the internal volume V _{B of the} first channel upstream, V _Up ≥ V _B ; and the volume V _{Down of the} recovered fluid in step (g) is at least equal to the internal volume (V _D + V _E + V _F ) of the second channel downstream, V _Down ≥ (V _D + V _E + V _F ).

Advantageously, the volume V _Up recovered liquid in step (b) is _{V Up = V B * SF Up} , where SF _Up - a coefficient 1,0≤SF _Up ≥2,0; and / or the volume V _{Down of the} recovered fluid in step (g) is V _Down = (V _D + V _E + V _F ) * SF _Down , where SF _Down is a coefficient of 1.0 ≤ SF _Down ≥ 2.0. It is more favorable if the SF _Up coefficient and / or the SF _Down coefficient is less than or equal to 1.5.

The resulting reduction in the volume of fluid that is needed to fill the hydraulic system upstream and the hydraulic system downstream gives the advantage that the amount of fluid that should be used for filling and as a result cannot be introduced is minimal. This is especially important for very strong and expensive liquid medicines, such as insulin, for infusion pumps that have only the available tank volume, such as ambulatory infusion pumps, and for infusion pumps that regularly require refilling, for example, after replacement primary reservoir, disposable pump parts or infusion line.

Advantageously, in such an infusion pump, before removing the liquid medicament from the primary reservoir, the control unit verifies that the remaining contents of the primary reservoir is sufficient for the next stage of the filling procedure or, preferably, for all subsequent stages of the filling procedure. In this embodiment, it is especially advantageous if, in the case when the control unit detects that the remaining contents of the primary tank is insufficient, the control unit requires that the user replace or supplement the primary tank.

Advantageously, during the filling procedure, the control unit monitors the pressure in the second channel downstream. This allows blockages to be detected in the channel downstream.

The infusion pump may also include a detector that is configured to detect the presence of air bubbles in the second channel downstream.

Advantageously, the pump is a cylindrical pump with a cylinder as a secondary reservoir and a piston slidably mounted inside the cylinder.

In yet another advantageous embodiment of such an infusion pump, during the filling procedure, the control unit monitors the accumulated amount of air in the second channel downstream. In this embodiment, it is especially advantageous if the control unit repeats the filling procedure when the accumulated amount of air exceeds a certain threshold value.

In a favorable method according to the disclosure of filling an infusion pump with a primary reservoir for a liquid medicament, a pump with a secondary reservoir that can extract liquid medicament from the primary reservoir and then dispense the liquid medicament from the secondary reservoir in incremental steps, the first upstream channel hydraulically connecting the primary reservoir to pump, the second channel downstream, hydraulically connected to the pump for transporting the liquid medication to the interface of the injection site and the valve variable m for the compound pump to one of the two channels, the following steps are performed for filling the hydraulic infusion pump system with liquid medicament before the infusion operation: (a) adjusting the pump to its initial state when the interior volume of the secondary tank is minimal; (b) switching the valve to a first state in which a secondary reservoir is connected to the first channel and the primary reservoir; (c) recovering the liquid medicament from the primary reservoir, wherein the volume V _{C of the} recovered liquid is at least equal to the internal volume V _{B of the} first channel upstream; (d) switching the valve to a second state in which a secondary reservoir is connected to the second channel downstream; (e) displacing the contents in the secondary reservoir into the second channel downstream; (e) switching the valve to a first state; (g) recovering the liquid medicament from the primary reservoir, wherein the volume V _{C of the} recovered liquid is at least equal to the internal volume V _D + V _E + V _{F of the} second channel downstream; (h) switching the valve to a second state; and (i) displacing the contents in the secondary tank into the second channel downstream by moving the piston to its original position.

In a favorable embodiment of such a method of filling an infusion pump with a primary reservoir for a liquid medicament, a pump with a secondary reservoir that can extract liquid medicament from the primary reservoir and then dispense the liquid medicament from the secondary reservoir in incremental steps, the first upstream channel hydraulically connecting the primary reservoir to pump, the second channel downstream, hydraulically connected to a pump for transporting liquid medication to the interface of the injection site, a valve for I alternately connecting the pump to one of the two channels and a control unit configured to control the operation of the infusion pump, the following steps are performed to fill the hydraulic system of the infusion pump with liquid medication before the infusion operation: (a) initializing the pump when the internal volume of the secondary tank is minimal; (b) switching the valve to a first state in which a secondary reservoir is connected to the first channel and the primary reservoir, and extracting a volume of liquid medicament from the primary reservoir; (c) switching the valve to a second state in which the secondary reservoir is connected to the second channel downstream, and displacing the contents in the secondary reservoir to the second channel downstream; and (e) switching the valve to a second state; and displacing the contents in the secondary tank into the second channel downstream. The extracted volume V _{Up of the} liquid in stage (b) is at least equal to the internal volume V _{B of the} first channel upstream, V _Up ≥V _B ; and the volume V _{Down of the} recovered fluid in step (g) is at least equal to the internal volume (V _D + V _E + V _F ) of the second channel downstream, V _Down ≥ (V _D + V _E + V _F ).

Favorably, the volume V _{Up of the} recovered fluid in step (b) is V _Up = V _B * SF _Up , where SF _Up is a coefficient of 1.0≤SF _Up ≥2.0; and / or the volume V _{Down of the} recovered fluid in step (g) is V _Down = (V _D + V _E + V _F ) * SF _Down , where SF _Down is a coefficient of 1.0 ≤ SF _Down ≥ 2.0. It is more favorable if the SF _Up coefficient and / or the SF _Down coefficient is less than or equal to 1.5.

In a favorable embodiment of this method, before removing the liquid medication from the primary reservoir, it is verified that the remaining contents of the primary reservoir is sufficient for the next stage of the filling procedure or, preferably, for all subsequent stages of the filling procedure. Advantageously, if it is determined that the remaining contents of the primary tank are insufficient, the primary tank is replaced or supplemented before performing the filling procedure.

In yet another advantageous embodiment of such a method, the pressure in the second channel downstream is controlled during the filling procedure. This allows blockages to be detected in the channel downstream.

In yet another advantageous embodiment of such a method, the presence of air bubbles in the second channel downstream is detected during the filling procedure.

In yet another advantageous embodiment of such a method, the pump is a cylindrical pump with a cylinder as a secondary reservoir and a piston slidably mounted inside the cylinder.

Advantageously, the accumulated amount of air in the second channel downstream is controlled during the filling procedure. In a particularly favorable embodiment, the filling procedure is repeated if the accumulated amount of air exceeds a certain threshold value.

Advantageously, this filling method is carried out with an infusion pump according to the disclosure discussed above.

Another infusion pump according to the disclosure comprises a primary reservoir for a liquid medicament, a pump with a secondary reservoir that can extract the liquid medicament from the primary reservoir and then dispense the liquid medication from the secondary reservoir in one or more portions of an adjustable volume V _{dose, i} into the downstream channel , and a control unit for controlling the operation of the infusion pump. To dispense multiple batches of V _{dose, i,} the control unit forces the infusion pump to perform the following steps: (a) determine the maximum level of V _{C, max} replenishment for the secondary tank, based on data from external parameters, and the maximum level of replenishment does not exceed the maximum capacity of the secondary tank; (b) filling the secondary reservoir with liquid medicine from the primary reservoir to a maximum level of V _{C, max} replenishment; (c) dosing and transporting a plurality of portions of the liquid medicament into the channel downstream; (d) if the secondary reservoir is empty, replenishment of the secondary reservoir as in stage (b) and continued from stage (c).

Another favorable infusion pump according to the disclosure comprises a primary reservoir for a liquid medicament, a pump with a secondary reservoir that can extract the liquid medicament from the primary reservoir and then dispense the liquid medication from the secondary reservoir in one or more portions of an adjustable volume V _{dose, i} to the channel below flow, and a control unit configured to control the operation of the infusion pump. To dispense multiple batches of V _{dose, i,} the control unit forces the infusion pump to perform the following steps: (a) filling the secondary reservoir with liquid medication from the primary reservoir to a certain controlled level of V _refill ; (b) dosing and transportation at certain points in time t _{i of} different portions of V _{dose, i of a} liquid medication into a channel downstream; and (c) if the secondary reservoir is empty, replenishment of the secondary reservoir as in step (a) and continued from step (b). The control unit regularly determines the maximum level V _{C, max} replenishment for the secondary reservoir and extracts such maximum level V _{C, max} replenishment from another source, such as memory, and the volumes V _{dose.i of} one or more portions of the liquid medication to be dosed, and time points t _i , into which they are dosed and transported, do not depend on the indicated maximum level V _{C, max} replenishment. During dispensing a plurality of portions of V _{dose, i,} the control unit limits the filling of the secondary tank in stage (a) to a _refill level V _refill that is less than or equal to the indicated maximum level V _{C, max} refill.

Such a favorable variant of the infusion pump makes it possible to limit the volume of liquid that is available in the secondary tank at any time to a certain value, thereby usually reducing the risk associated with any serious malfunction without affecting the normal operation of the device, namely the introduction of clear doses of liquid medication.

In one favorable embodiment of such an infusion pump, if the secondary reservoir is empty during dosing of a single portion of the liquid medication and needs to be replenished, the maximum replenishment level for this particular replenishment stage is increased to an increased maximum level V _{C, max} = V _{C, max} + V _{dose, rem} , and V _{dose, rem} is the remaining volume of a single portion that has not yet been fully dosed.

In another favorable embodiment of such an infusion pump, if the next unit dose V _{dose.i of the} medicament to be dispensed exceeds a certain threshold, the secondary tank is replenished to the maximum level of replenishment before or after the introduction of the specified unit dose.

In another favorable embodiment, if the secondary reservoir was empty during dosing of the next single portion (V _{dose, i, next} ) of the liquid medication, before dosing the next portion, the secondary reservoir is replenished with the liquid medication from the primary reservoir to an increased maximum level

V _{C, max} = V _{C, max} + V _{dose, i, next} , and V _{dose, i, next} is the volume of a single portion, which should be dosed next.

In another favorable embodiment of such an infusion pump, if the secondary reservoir is emptied during dispensing of a single portion of the liquid medication and needs to be replenished, the replenishment of the secondary reservoir is divided into two stages. In the first stage, the secondary reservoir is filled with liquid medicine from the primary reservoir to the level of V _{dose, rem} volume, and V _{dose, rem} is the remaining volume of a single portion that has not yet been fully dosed, and the indicated remaining volume is dosed and transported. In the second stage, the secondary tank is filled to the maximum level V _{C, max} replenishment.

In such infusion pumps, in a favorable manner, the maximum level of V _{C, max} replenishment of the secondary tank is proportional to the amount of liquid, the dosage of which is expected within a certain period of time.

It is also favorable if in such infusion pumps the control unit or a separate system regularly recalculates the maximum level V _{C, max} replenishment depending on the average volume of liquid that has been dosed within a certain period of time in the past, if the recalculation was performed by a separate system , then provides the specified recalculated maximum level V _{C, max} replenishment to the control unit, for example, storing it in memory. In a particularly favorable embodiment of such a device, the maximum level of V _{C, max} replenishment is calculated based on the average volume of liquid that has been dosed over a period of time that includes at least the last 24 hours. Even more favorably, this period includes at least the last 48 hours or even a week. This gives the advantage that V _{C, max} adapts to changes in the total average daily dose, which may change over time due to changing physical conditions of the patient. In yet another favorable embodiment of such an infusion pump, the maximum level of V _{C, max} replenishment of the secondary tank is controlled if one or more of these external parameters are changed.

In yet another advantageous embodiment of such an infusion pump, one or more sensors are provided that can detect changes in ambient temperature and / or ambient pressure.

In yet another advantageous embodiment of such an infusion pump, according to the disclosure, the control unit or a separate system regularly recalculates the maximum level V _{C, max} depending on changes in the ambient temperature and / or ambient pressure over a certain period of time in the past, and if the recalculation was performed by a separate system, after which it provides the specified recalculated maximum level V _{C, max} to the control unit, for example, storing it in memory.

In a favorable method according to the disclosure of the operation of an infusion pump, which contains a primary reservoir for liquid medication and a pump with a secondary reservoir, which can remove the liquid medication from the primary reservoir and then deliver the liquid medication from the secondary reservoir in one or more portions of an adjustable volume V _{dose, i} in channel downstream, the following steps are performed for a plurality of metering portions V _{dose, i:} (a) determining the maximum level of V _{C, max} refill the secondary reservoir, is given on the basis of s external parameters, wherein the maximum recharge level does not exceed the maximum capacity of the secondary reservoir; (b) filling the secondary reservoir with liquid medicine from the primary reservoir to a maximum level of V _{C, max} replenishment; (c) dosing and transporting a plurality of portions of the liquid medicament into the channel downstream; (d) if the secondary reservoir is emptied, replenishment of the secondary reservoir as in stage (b) and continued from stage (c).

In another favorable method, according to the disclosure, the operation of an infusion pump containing a primary reservoir for liquid medicine and a pump with a secondary reservoir, which can remove the liquid medication from the primary reservoir and then transport the liquid medication from the secondary reservoir in one or more portions of an adjustable volume V _{dose , i} in channel downstream for dispensing a plurality of portions of V _{dose, i,} the following steps are performed: (a) filling the secondary container from the primary liquid medicament reservoir until a certain controlled level V _refill replenishment; (b) dosing and transportation at certain points in time t _{i of} different portions of V _{dose, i of a} liquid medication into a channel downstream; and (c) if the secondary reservoir is empty, replenishment of the secondary reservoir as in step (a) continues from step (b). On a regular basis, the maximum level of V _{C, max} replenishment for the secondary reservoir is determined or obtained from another source, such as memory, the volumes V _{dose, i of} one or more portions of the liquid medication to be dosed, and the times t _i at which they are dosed and transported, do not depend on the specified maximum level V _{C, max} replenishment. During dispensing a plurality of servings of V _{dose, i, the} filling of the secondary tank in step (a) is limited by the _refill level V _refill , which is less than or equal to the indicated maximum _refill level V _{C, max} .

Such a favorable variant of the operation method allows you to limit the amount of liquid that is available in the secondary tank at any time to a certain value, thereby, as a rule, reducing the risk associated with any serious malfunction without affecting the normal operation of the device, namely the introduction of clear doses of liquid medication.

In one favorable embodiment of this method, if the secondary reservoir is emptied during dispensing of a single portion of the liquid medication and needs to be refilled, the maximum refill level for this particular refill stage is increased to an increased maximum level V _{C, max} '= V _{C, max} + V _{dose, rem} , wherein V _{dose, rem} is the residual volume of a single portion that has not yet been fully dosed.

In another favorable embodiment of such a method, if the next portion of a unit V _{dose, i} liquid medicament to be dispensed, exceeds a certain threshold, the secondary reservoir is replenished up to a maximum level to recharge, or after administration of said single portion.

In another favorable embodiment of this method, if the secondary reservoir was empty during dosing of the next single portion (V _{dose, i, next} ) of the liquid medication, before dosing the next portion, the secondary reservoir is replenished with the liquid medication from the primary reservoir to an increased maximum level V _{C, max} '= V _{C, max} + V _{dose, i, next} , and V _{dose, i, next} is the volume of a single portion, which should be dosed next.

In another favorable embodiment of this method, if the secondary reservoir is emptied during dispensing a single portion of the liquid medication and needs to be replenished, the replenishment of the secondary reservoir is divided into two stages. In the first stage, the secondary reservoir is filled with liquid medicine from the primary reservoir to the level of V _{dose, rem} volume, with V _{dose, rem} being the residual volume of a single portion that has not yet been fully dosed, and the indicated residual volume is dosed and transported. In the second stage, the secondary tank is filled to the maximum level V _{C, max} replenishment.

Advantageously, in such methods, the maximum level of V _{C, max} replenishment of the secondary tank is proportional to the amount of liquid, the dosage of which is expected over a certain period of time.

In addition, in such a method according to the disclosure, it is advantageous to regularly recalculate the maximum level of V _{C, max} replenishment depending on the average volume of liquid that should have been dosed over a certain period of time in the past. In a particularly favorable embodiment of such a method, the maximum replenishment level V _{C.max is} recalculated based on the average volume of liquid that has been dosed over a period that includes at least the last 24 hours. Even more favorably, this period includes at least the last 48 hours or even a week. This gives the advantage that V _{C, max} adapts to changes in the average total daily dose, which may change over time due to changing physical conditions of the patient.

It is also beneficial for such a method if the maximum level V _{C.max of} replenishment of the secondary tank is controlled when one or more of these external parameters are changed.

In yet another advantageous embodiment of such a method, according to the disclosure, one or more sensors are provided that can detect changes in ambient temperature and / or ambient pressure.

In yet another advantageous embodiment of such a method according to the disclosure, the maximum level of V _{C, max} replenishment is recalculated on a regular basis depending on changes in ambient temperature and / or ambient pressure over a certain period of time in the past.

Advantageously, such a method is performed with an infusion pump according to the disclosure described above.

Brief Description of the Drawings

In order to facilitate a more complete understanding of the present invention, reference will now be made to the accompanying drawings. These references are not to be construed as limiting the present invention, but are intended as examples only. Shown on:

FIG. 1: schematically, a prior art infusion pump with a metering device (a) of a syringe drive type, and (b) of a downstream type pump with a primary reservoir and a secondary reservoir of a pump cylinder,

FIG. 2: schematically, an infusion pump with a metering device such as a downstream pump with a primary reservoir and a secondary reservoir of a pump cylinder to which the filling method according to the disclosure is applied,

FIG. 3: schematically, a metering device according to the disclosure, with a partial sectional view of the valve seat and a view of the pump cylinder and valve element,

FIG. 4: schematically, the metering device according to FIG. 3 in partial sectional view of the cylinder and view of the piston of the pump,

FIG. 5: schematically, a detail of the metering device according to FIG. 3 in the field of detection windows,

FIG. 5A: schematically, a cross section of another embodiment of a metering device according to the invention, (a) when liquid is displaced from the cylinder, and (b) when new liquid is removed,

FIG. 6: (a) a typical dosing profile for insulin using an infusion pump, and (b), (c), (d) the accumulated dose profile of insulin, together with the replenishment stages in accordance with the different pump replenishment strategies used in the dosing method according to the disclosure ,

FIG. 7: a table with the contents of a FIFO-based metering journal that records the amounts of liquid medication administered and air detected, for monitoring air in a downstream hydraulic system in a dosing method according to the disclosure,

FIG. 8: another table with the contents of the FIFO-based metering journal for monitoring air in a downstream hydraulic system in another embodiment of a dispensing method according to the disclosure.

Description of Embodiments

So that there are fewer dosing errors when administering a liquid medication, the exact dosage of the liquid medication is a critical factor. In a metering device that allows small incremental doses to be dispensed from the secondary interval by dividing the total piston stroke by a larger number of partial strokes, the piston pump acting as a secondary reservoir, as is preferred in this invention, requires accurate knowledge of the position of the piston inside the cylinder at any time.

In the infusion pump known in the art, the movement of the piston inside the primary reservoir cartridge is determined only indirectly. The engine of the drive unit is equipped with a sensor that detects the rotation of the axis of the engine. Based on the number of revolutions and the known thread pitch of the threaded piston rod, the displacement of the piston in the cartridge of the primary reservoir is determined. However, if the working connection between the engine and the piston rod for some reason does not work, for example, due to a damaged thread or gear, the pump will determine the movement of the piston, although the piston may not move at all. Therefore, the result of such a failure may be an undetectable metering error. This is especially true for syringe type piston pumps because the drive unit motor is only temporarily engaged with the piston of the disposable cartridge, and each cartridge replacement carries the risk of technical failure. In addition, the large diameter of the cartridge and the elasticity of the kinematic chain can lead to the fact that the rotation of the engine will not be converted to the correct movement of the plunger.

In the metering device for an infusion pump according to the disclosure, accurate and trouble-free metering is achieved by directly detecting the movement of the piston rod of the cylindrical pump. For example, if the threaded piston rod rotates during movement, the relative movement can be determined based on a certain number of revolutions and thread pitch. It is also possible to determine the absolute position of the piston by initiating a zero position in which the piston head touches the end of the cylinder.

One possible embodiment of the metering device according to the disclosure is shown in FIG. 3-5, schematically showing a partial sectional view of a metering device 12 comprising a cylindrical pump 14, 16 and a valve 35. The basic combined pump / valve principle of the metering device shown is similar to that disclosed in EP 1970677 A1 and EP 2163273 A1, discussed above. The front end of the cylinder 14 acts as a rotatable valve element 44 cooperating with the valve seat 40. The valve may switch between a first state in which the inlet channel 24 is completely connected to the internal volume 13 of the pump cylinder and a second state in which the exhaust channel 25 is completely connected to the internal volume 14 of the pump. FIG. 3-5, the valve is in the indicated second position, in which the pump can displace the liquid medication in the pump cylinder into the hydraulic system downstream and to the patient. Downstream of the outlet port 25 shown, an air sensor and an obstruction sensor are located in the metering device. For better readability, these elements are omitted from the figures.

The cylinder 14 is mounted to rotate in the support 42 of the valve 35. By rotating the cylinder along its longitudinal axis 48, the valve switches between a first state and a second state by a certain angle. The cam 46 on the cylinder interacts with two stoppers (of which only one 47 is visible) on the valve support 42, thereby determining two discrete valve positions.

The piston rod 48, which is connected to a drive motor (not shown), comprises a first segment 51, immediately behind the piston head 17, and a second threaded segment 50. The external thread 52 of the rod interacts with the short internal threaded segment 54 on the cylinder. Therefore, the rotation of the piston 16 along the axis 48 counterclockwise leads to a linear movement in the direction I, increasing the internal volume, and the rotation clockwise leads to a linear movement in the direction II, reducing the internal volume.

The static and dynamic friction between the piston thread 52 and the cylinder thread 54, the static and dynamic friction between the piston head 17 and the cylinder wall 14, and the static and dynamic friction between the cylinder support and the cylinder are selected so that the engaged movement between the rotary piston 16 driven by the drive node (not shown), and cylinder 14, occurs until the movement of the cylinder in the support is blocked. This occurs when the static (and therefore dynamic) friction between the cylinder and the support is less than the sum of the static friction between the cylinder and the piston head and between the piston thread and the cylinder thread.

When the cam 46 abuts against one of 47 of the two stops, and therefore the movement of the cylinder in the support is blocked, this is equivalent to a very high static friction between the support of the cylinder and the cylinder. The static friction between the cylinder and the support is now greater than the sum of the static friction between the piston head and the cylinder, and the piston thread and the cylinder thread.

Now the cylinder and piston are disengaged, and the rotating piston 18 begins to move inside the now static cylinder 14.

In FIG. 3, the piston head 17 reaches the end of the cylinder 14, with the internal volume 13 of the cylinder being minimal. Further movement of the piston is not possible, which is recorded by the drive unit. The absolute position of the piston 16 is now clearly defined and reset to zero in the control unit. If now the rotation of the piston is reversed, i.e. counterclockwise, there is no stop in the path of cam 46, and the cylinder and piston again become dynamically engaged, which causes the cylinder to rotate in the support until cam 46 reaches another stop (not visible). The valve has switched to the first state, and the piston is again disconnected from the cylinder. Now the piston moves in direction I and draws the liquid medication into the cylinder from the primary reservoir through the inlet 24. After extracting the necessary amount of fluid, the piston rotates again clockwise and the valve switches to the second state. The dosing device is now ready to deliver the liquid in the required doses.

In a metering device in accordance with the present disclosure, the actual movement of the piston is determined by directly detecting the rotation of the piston rod. For this purpose, the first rod segment 51 is provided with tags that can be optically distinguishable. For example, such marks may be longitudinal black 64 and white 64 marks, as shown in FIG. 3. However, this is not essential. They can be white or gray or in other colors or provided with different reflection values, etc.

The cylinder wall 14 and the valve support 42 are provided with partially matching windows 60, 62 made in the form of holes (as shown in the figures) or transparent parts. These partially matching windows 60, 62 provide optical access to the tags. A light emitting element 56, such as an LED, illuminates the marks, and a photosensor 58 detects the light reflected by the marks, which has, for example, a low amplitude for black marks and a high amplitude for white marks. Thus, the rotation of the piston rod is determined by counting the changes between the marks, respectively, by counting the rising and falling edges in the corresponding oscillating signal generated by the photosensor 58.

In the example shown, the piston rod 18 is provided with four black marks 64 and four white marks 65. As a result, this gives a detectable signal (rising or falling edge) every 45 ° of rotation, which, together with a fairly flat thread pitch, allows the piston to move very precisely in the longitudinal direction and therefore very high metering accuracy.

A favorable feature of such a metering device with a rotary encoder, which is integrated into the piston rod or rigidly connected to the piston rod, is the fact that the measured signal is directly related to the actual rotation of the piston. If the adhesion between the engine and the piston is broken, this event can be immediately recognized, without the risk of a potentially dangerous metering error. Any technical malfunction in the kinematic chain, for example a malfunctioning clutch between the piston and the drive unit or a broken transmission shaft, etc., which in the case of a known device may go unnoticed, will be detected.

The dosing volume can be controlled either by activating the pump drive for a certain time, or by activating the drive unit until a certain movement is achieved. In the first approach, information about the movement of the piston is used to check whether the accuracy remains within certain limits, and to reconfigure the drive unit, if necessary. In the second approach, the required resolution of the movement coding is higher.

Of course, tags 64, 65 can be selected in different colors, depending on the sensor and lighting system. Marks can be obtained, for example, by appropriate coating or printing methods, or by two-component injection molding.

Alternatively, the marks may be provided in the form of circumferential rings, instead of longitudinal stripes. With such a linear encoder, the detected light signal would directly correlate with the longitudinal movement of the piston.

As shown in FIG. In the 3, 4, 5 version, two partially matching windows are provided. Although this option has additional advantages, which will be discussed later, for the basic principle, it is sufficient to provide a window 60 only in the wall of the cylinder 14, if the support 42 is designed so that it cannot close the window 60.

In FIG. 5A is a schematic cross-sectional view of another embodiment of a favorable metering device according to the disclosure, with a piston 16 that slides inwardly inside the cylinder 14. The cylinder is slidably mounted in the support 42. The front of the cylinder and the front of the support are configured to form a valve 40, 44.

In the second operating state of the valve, the pumping state, the valve member 44 abuts against the valve seat 40, determining the stop position. The hole in the cylinder wall coincides with the outlet channel 25, while the inlet channel 24 is hermetically sealed by the cylinder wall. When the piston head 17 is pushed into the cylinder, as shown in FIG. 5A (a), the fluid is displaced through the outlet channel 25 and further in the direction of the hydraulic system downstream (not shown).

In the first operating state of the valve, the replenishment state, as shown in FIG. 5A (b), the cylinder 14 is displaced in the support 42. The end of the cylinder acts as a stopper 47, resting against the cams 46 of the support. In this first state, the outlet channel is hermetically sealed by the cylinder wall, and the inlet channel 24 is connected to the cylinder through an opening in the cylinder wall. When the piston head 17 is drawn back, fluid flows from a primary reservoir (not shown) to a secondary cylinder reservoir.

The piston rod 18 is provided with a scale 63 of optically distinguishable marks 64, 65, for example, black and white fields or reflective and non-reflective fields. Both the cylinder and the bearing are provided with windows 60, 62, which are arranged so that they coincide when the valve is in the pump state. The light-emitting device 56 can emit a light beam through the windows on the scale 63, and the corresponding detector device 58 can detect a returning light signal. When the piston is pushed toward the end of the cylinder, marks 64, 65 pass through the detector and generate a series of signal profiles that directly correspond to the relative movement of the piston.

When the valve is in the replenishment state, the two windows 60, 62 do not match and the sensor 56 does not have access to the scale.

Regarding the embodiment of FIG. 3, 4, 5, valve switching is also initiated by the piston without the need for a separate valve actuator.

However, in this embodiment, there is no rotational movement of the piston or cylinder. The friction between the piston and the cylinder is higher than between the cylinder and the support. Thus, if the valve is not in one of the two stop positions that define the two operating states, the piston is frictionally engaged with the cylinder and the movement of the piston also moves the cylinder in the support. When the valve reaches one of the two stop positions, the movement of the cylinder is blocked and the piston is frictionally detached from the cylinder and can move inside the cylinder.

In one embodiment of the metering device according to the disclosure, the marks on the piston rod are replaced with through holes, for example, drilled holes that radially cross the rod and allow the light beam emitted by the light emitting device to pass through the rod to the photosensor on the opposite side. In yet another embodiment, the light emitter and the photosensor may be located on the same side, and only reflective elements are provided on the opposite side that reflect light passing through the through hole.

In another advantageous embodiment of the metering device according to the disclosure, an absolute rotary or linear encoder is used instead of the relative rotational or linear encoders discussed previously. This makes it possible to omit the initiation of the position of the piston.

In another embodiment of the disclosure, other appropriately detectable labels, for example, conductive and non-conductive regions or magnetic and non-magnetic regions, may be used instead of optical marks.

In an alternative embodiment, mechanical means are provided for coding the rotation of the piston. For example, a piston may be provided with a plurality of teeth that interact with a corresponding resilient member, for example, on a cylinder, such as a spring-loaded dog. An additional modulated friction is added to the constant friction between the piston and the cylinder. As a result of this, the force to be overcome during the rotation of the piston and the necessary driving moment of the engine are also modulated, and the moment modulation is reflected by the current modulation. The latter can be detected to determine the rotational position.

An additional feature of the detection system used to determine the rotation of the piston is that it can also be used to check whether the valve 35 is in the correct state during pump operation. In the second state of the valve, as shown in the figures, window 60 allows the oscillating signal to be detected as a result of piston rotation. However, when the valve switches, the window 60 rotates with the rest of the cylinder, thereby closing the marks 64, 65 from detection. Thus, only if the valve is in the second state, the detection system 56, 58 can detect the signal when the piston rotates. If the signal is not detected when it is assumed that the valve is in the second state and the drive unit is active, the device control unit will recognize the error.

Thus, the dosing device described above, with windows that provide access to the encoder marks only in discrete positions of the valve state, but not in the transitional positions between them, allows to determine the malfunction or clogging of the valve.

In yet another embodiment of such a metering device, a second window is provided in the cylinder wall that provides optical access to the marks 64, 65 when the valve 35 is in the first state. This option has the additional advantage that in the replenishment mode the movement of the piston can be precisely controlled.

In yet another embodiment, the rotational position of the cylinder relative to the static valve seat can be controlled by an independent detection system. For example, relative or absolute rotation encoder marks may be provided on the outer wall of the cylinder.

Before an infusion pump can become operational, it must be properly prepared. Among the preparatory steps, the control system and pump system must be initialized, and the hydraulic system must be filled with liquid medication. This so-called priming should be carried out if the pump unit is used for the first time, or if the infusion tubes or disposable pump unit have been replaced.

The accuracy of infusion pumps with respect to metering and air bubble errors can be significantly improved by filling the hydraulic system of infusion pumps without air bubbles. This means that when a hydraulic system containing an inlet between the primary reservoir and the pump cylinder, the reservoir cylinder, exhaust valve, and connected infusion tubes is filled with fluid for the first time before use, air should not be introduced into the hydraulic system and air bubbles should be removed .

To fill the system in known metering devices, a pump is activated and pumps the liquid medicament until the liquid reaches the end of the infusion tube and the cannula attached to the tube. The user then stops the fill, or the fill may stop automatically. The absence of air bubbles is checked by visual inspection of the tube by the user. The filling procedure is uneconomical, since expensive liquid medication can be spent without any benefit. In addition, it requires a certain skill and understanding on the part of the user, which as a result makes the filling procedure error-prone.

In the operating method according to the disclosure for filling the hydraulic system of an infusion pump, filling of the metering device with the primary reservoir and the secondary reservoir of the pump cylinder can be significantly improved. The method will be explained with reference to the schematically shown infusion pump 10 in FIG. 2.

The infusion pump 10 shown includes a primary reservoir 11 and a metering device 12 with a cylindrical pump with a secondary reservoir 15 having a cylinder 14, a bi-directional piston 16 driven by a drive unit 20, and a ¾-way valve for alternately connecting the pump cylinder to the inlet 24 and the primary reservoir 11, and with the outlet channel 25 and the infusion tube 28. Parts of the infusion pump, advantageously parts having direct contact with the liquid medication, can be implemented as disposable eleme nt, while other parts are implemented as reusable parts. Alternatively, the entire pump may be fully reusable or a disposable device.

An air sensor 36 is provided in the outlet channel 25 downstream of the secondary reservoir 15 and is able to detect the presence of air in the channel. Such an air sensor can be implemented, for example, in the form of an optical sensor, by measuring the transmission or reflection of light. In one possible embodiment, a light emitting element, such as an LED, emits light through a corresponding window in the channel wall into the channel. The angle of illumination is chosen so that if the channel in the position of the sensor is filled with liquid, light enters the liquid and crosses the channel. If the channel is empty (vacuum) or filled with air (air bubble), the light beam is reflected on the boundary surface and cannot cross the channel. Either the light crossing the channel, or the light reflected on the window / boundary surface, or both, is detected by the corresponding light detection element, for example, a photodiode or phototransistor.

Further, downstream of the sensor 36, an obstruction sensor 38 is provided, which may be implemented, for example, as a pressure sensor. Such a pressure sensor can be implemented, for example, with a micro-hydraulic chamber disclosed in the applicant's European patent application EP 2295096 A1, where the pressure in the micro-hydraulic chamber is determined by measuring the deflection of the light beam by the surface of the flexible chamber cover.

In the filling method according to the disclosure, the particular advantages of the metering device with a cylindrical pump with a secondary reservoir are used, and the filling of the hydraulic system is based on the known volume of the hydraulic system and the signals of the air sensor and the clogging sensor. The user is freed from most of the control and manipulation tasks during the pouring operation.

The hydraulic system of the infusion pump 10 in FIG. 2 essentially consists of the volume V _{A of the} primary reservoir, the volume V _{B of the} hydraulic system between the primary 11 and secondary 15 reservoir, namely the volume of the inlet channel 24 and any existing connectors, partitions, etc .; variable volume V _C secondary reservoir; the volume V _{D of the} hydraulic system between the secondary reservoir 15 and the air sensor 36; the volume V _{E of the} hydraulic system between the air sensor 36 and the connector 26; and volume V _{F of the} infusion tube 28.

Stage A)

In order to effectively and reliably fill the dosing device system, it is necessary to know the volumes of the various parts of the hydraulic system. While the pump monitors the current values of the volume V _{A of the} residual liquid in the primary tank, as well as the current volume V _C in the secondary tank, the volumes V _B , V _F , V _{E are} set by the design of the dosing device and can be stored predefined in the controller memory 22. Any dead volume of the secondary reservoir, i.e. the volume of the pump cylinder, which can not be emptied, is considered part of the hydraulic volume V _D downstream.

The only volume that cannot be determined by the system itself is the volume V _{F of the} infusion tube. Therefore, at the first stage, the user must indicate the volume V _{F of the} infusion tube. For this purpose, it suffices to indicate the length L _{F of the} tube of a given standard type, which has a known cross-sectional area A _F. Then the volume is determined by the formula V _F = L _F * A. The user can, for example, select from a menu from a pre-set of standard-length infusion tubes for a particular pumping system.

The current volume V _{A of the} primary reservoir of the system is known, since during the infusion and pouring operations, the quantities of liquid volume obtained from the reservoir are constantly subtracted from the reservoir volume. When a new complete primary tank is inserted into the infusion pump, the current volume V _{A is} reset to a predetermined initial level V _A = V _{A, start} filling this tank. This initial volume can, for example, be recognized automatically, or can be entered by the user, or can be determined using an additional level sensor.

The pump system also monitors the amount of _air V _air that the air sensor has passed in the hydraulic system and therefore is present in the hydraulic system downstream. This aspect of the disclosure will be discussed in more detail below. Before filling, V _{air is} reset to 0.

Stage B)

The required volume of fluid for the pouring operation is calculated. The volume for filling the hydraulic system upstream is V _Up = V _B * SF _Up , where SF _Up is the reliability coefficient, for example, SF _Up = 1.0-1.5. The volume for filling the hydraulic system downstream is V _Down = (V _D + V _E + V _F ) * SF _Down , where SF _Down is the reliability factor, for example, SF _Down = 1.0-1.5. If the required fill volumes exceed the residual volume of the primary tank, V _Up + V _Down > V _A , an error message is generated requiring the user to replace the primary tank before initiating the filling.

Stage B)

The fill operation is initiated automatically by the system or manually by the user. The piston 16 of the pump is brought to the initial stop position in the cylinder. The filling level of the secondary tank is reset to V _C = 0. For the steps explained above, valve 35 is in a second state.

Stage D)

The valve 35 is set to a first state in which the cylinder 14 is connected to the primary reservoir 11. The controller 22 causes the drive assembly 20 to remove the piston 16 until the volume of the secondary reservoir is V _C = V _Up. Part of the hydraulic system is upstream now filled with liquid medicine while the secondary reservoir is filled with liquid and an undetermined amount of air from the system upstream. The volume of the primary tank is updated to V _A = V _A -V _Up .

If priming is performed for the first time after replacing a disposable pump assembly, the operation of the air sensor 36 can be checked: if the air sensor detects air, the filling procedure continues. If the air sensor detects a liquid, an error message is generated and filling stops.

Stage D)

In the next stage, the valve 35 is transferred to the second state, in which the cylinder 14 is connected to the outlet channel 25. The piston is brought to its original position, and any air and liquid medication previously present in the pump cylinder is displaced into the hydraulic system downstream.

Stage E)

The valve is again brought into the first state, in which the cylinder 14 is connected to the primary reservoir 11, and the piston is retracted until the volume of the secondary reservoir is V _C = V _Down . The volume of the primary tank is updated to V _A = V _A -V _Down . The valve 35 is transferred to the second state, in which the cylinder 14 is connected to the outlet channel 25, and the liquid medicine in the secondary reservoir 15 is displaced into the hydraulic system downstream, which is now also filled with the liquid medicine. The volume of the secondary tank is now reset to V _C = 0.

During the entire filling sequence, the plug sensor 38 continuously monitors the pressure in the hydraulic system and turns on the plug signal if the pressure exceeds a certain threshold value. Then the user may be required to check the infusion device.

During filling the system downstream, the air sensor 36 continuously monitors the air entering the hydraulic system downstream by determining the volume V _air accumulated in the hydraulic system downstream

where S _prime is the pump flow during priming, for example, defined in nl / min or IE / min, d _air is the detector function, with d _air = 1 when the air detector detects air, and otherwise d _air = 0, t _start - start of the downstream fill sequence; t _active = t _start + V _D / S _prime is the point in time when the air sensor 36 becomes fully operational, namely when the cross section of the channel upstream of the air sensor with volume V _{D is} filled; t _end is the time at the end of the fill sequence of stage E).

Stage G)

If the volume V _{air, prime of the} accumulated air remains below a certain predetermined threshold value after filling downstream, filling has been successfully completed. The user is accordingly informed. If the volume V _{air, prime} exceeds the threshold value, the filling is not completed. The piston 16 is retracted back to its original position, and stages D), D), E) are repeated.

Stage 3)

If, after several attempts, the filling could not be successfully completed, or if the residual volume of liquid in the primary tank is insufficient, the filling sequence is terminated and the user is accordingly informed by an error message. For example, it may be required to replace a disposable assembly.

If the filling of the dosing device is successfully completed, the user is accordingly informed. The user can connect the infusion tube to the installed interface of the injection site, and the infusion pump is operational.

Filling can also be repeated at a later time, for example, when the entire system is reinitialized for some reason. In a favorable way, the user can interrupt the automatic manual filling procedure.

A possible malfunctioning condition that may occur during the normal operation of the infusion pump discussed in this application is the presence of an unknown amount of air in the metering cylinder. Such an event may be the result of unexpected emptying of the primary reservoir or blockage, or leakage in the hydraulic system upstream. In the event of a leak, air is drawn in from the environment into the pump cylinder. In case of blockage or emptying of the tank, a vacuum is created in the pump cylinder. If the pump valve switches from replenishment to dosing mode, the cylinder may be aerated during the switching process.

During dosing, the pump would eventually supply air that is present in the cylinder to the downstream system. There he would be detected by an air sensor that would generate a warning message and, if necessary, could interrupt dosing. However, while the pump is inactive, air does not pass through the air sensor and therefore may remain undetectable for a considerable time.

After unwanted aeration of the pump cylinder, the interior of the cylinder has an ambient pressure. As a result of a subsequent change in ambient temperature or pressure, a pressure differential may develop between the air trapped in the pump cylinder and the environment. As a result, the fluid could be sucked out of the infusion tube in the event of a negative pressure drop. If the pressure drop is positive, an unknown amount of the liquid medication will be delivered in an uncontrolled manner into the infusion tube, driven by the pressure drop, and as a result will be inadvertently administered to the patient.

The possible dangerous effect of such a dosage error depends on the circumstances, especially on the type of medication and physiological condition of the patient. If the metering error exceeds a certain level, the effects can be very dangerous. The indicated value may vary significantly from patient to patient. For example, the same amount of insulin, which can be still harmless for an adult weighing 80 kg and with low sensitivity to insulin, can be fatal for a child weighing 30 kg and with high sensitivity to insulin. Therefore, a critical requirement for a trouble-free infusion pump is to prevent the inadvertent administration of a potentially fatal dose of medication, even under the most unlikely circumstances.

In the method of operation, according to the disclosure, for dispensing a liquid medicament, this goal is achieved by limiting the maximum level of replenishment of the secondary reservoir during normal operation to a certain value. Although this can lead to more replenishment of the pump during continuous operation of the infusion pump than is theoretically necessary when the pump is always replenished to its maximum level, a change in pressure / temperature within certain predetermined limits leads to a reduced and improved dosing.

An unintended injection effect, which leads to the dosing errors considered, occurs when the pressure difference between the pump cylinder and the environment is p = (p _c -p _env ). The pressure drop can be either the result of a change in temperature T, or the result of a change in the pressure p _{env of} the environment. To maximize safety, it is necessary to take into account changes in parameters that can occur in real life even in unlikely circumstances. The ambient pressure can vary, for example, within 10 minutes by 200 mbar or even 500 mbar in both directions. Temperatures can vary within 10 minutes at 10 ° C or even 30 ° C in both directions.

If the pressure drop is positive, the enclosed air volume V _{air, C.0} will expand to a larger volume V _{air, C.1} to equalize the pressure, which leads to a metering _error V _error = (V _{air, C.1} -V _{air, C .0} ) liquid that is being displaced. According to the gas state equation pV = nRT dosing error directly proportional to the volume V _{air, C.0} air into the secondary reservoir, and _{V error = V air, C.0 (} T / T0), respectively V _error = V _{air, C.0} ( p / p1). Since the amount of air in the cylinder is unknown, for safety reasons, it is preferable to use a hypothetical volume V _{air, C, max} = V _{C of} air corresponding to a hypothetical event when the entire cylinder is filled with air. The above ratio is based on absolute values.

For the operation of the metering device, the worst-case dosing error for insulin can be defined - just as an example - as 5-20% of the total daily dose of V _TDD for a particular individual patient. In this case, the maximum level of V _{C. max} replenishment can be set, for example, as 20% of the total daily dose of V _TDD . With this value, the maximum possible dosing error, which could result from short-term fluctuations, is likely to be below 5% of the total daily dose V _TDD . If - just as an example - during a flight in an airplane, the pressure drops from approx. 1000 mbar to 860 mbar, this would correspond to the maximum possible metering _error V _{error, max} = V _{air, C} * 16% V _C.max * 16% = V _TDD * 3.25%. If, simply as an example, the patient leaves the air-conditioned room at 20 ° C and goes outside at 40 ° C, this would lead to the maximum possible dosing error due to the temperature increase V _error.max = V _C.max * 1.4 % Even for very unlikely events, for example, a sudden depressurization of the cabin on an airplane, the maximum possible error can in no case be greater than V _error = V _C.

Thus, by limiting the filling level of the secondary reservoir to a patient-specific maximum level, it is possible to adapt the operation of the infusion pump to a particular patient, ensuring the most safe operation for all users.

In one favorable embodiment of the dispensing method according to the disclosure, the method is adapted to additional circumstances. For example, the maximum replenishment level V _C.max may be temporarily lowered while flying in an airplane, thereby taking into account the possibility of a sudden drop in pressure. For this purpose, the user may require that the infusion pump enter “airplane mode”. Alternatively, the device can detect a slow drop in ambient pressure, assuming that the drop is caused by a normal decrease in pressure in the cabin, and can automatically switch to “airplane mode”.

Another advantage of the dispensing method according to the disclosure is the fact that in the event of a pump drive failure, when the pump drive does not stop pumping, as described above, the maximum amount of an accidentally infused drug is limited.

Replenishment of the secondary reservoir may be required both during bolus administration and at any time during basal administration. Switching the valve when the pump cylinder is replenished can cause a certain small metering error due to the movement of small amounts of volume. Although this error is very small, less than, for example, 0.1 insulin units, it can nevertheless be important, for example, during the basal period of insulin administration. In one particularly favorable embodiment of the dispensing method according to the disclosure, said dispensing error is minimized by applying a favorable pump replenishment strategy. This type of metering error is critical in that it accumulates over time depending on the number of valve switching operations.

In one possible approach, the accumulated error is minimized by minimizing the number of replenishment stages over a given period. This is achieved by replenishing the pump always to the maximum permissible value. This approach is explained with reference to FIG. 6, in which (a) shows a simplified typical profile of insulin administration using an infusion pump over a normal day. In addition to administering a basal dose of insulin (dark gray areas) that covers the patient's constant need, bolus doses (light gray) are administered that take into account the increased need for insulin after three meals. It should be noted that for bolus administration, the total bolus dose is usually administered in a short time in the range of several seconds to several minutes. In FIG. 6 (B) shows the corresponding accumulated administered dose of insulin, as a percentage of the total daily dose of TDD.

To minimize the number of replenishment stages, the secondary tank is always completely empty before replenishment, and it is also always completely replenished to the maximum level V _{C, max} = V _TDD replenishment. The maximum replenishment level is set, for example, at V _{C, max} = V _TDD * 20% or, generally speaking, a certain percentage of the total daily dose of V _TDD . Thus, on average, over a 24 hour period, five replenishment steps are required to cover the total daily dose in this example. The resulting replenishment stages are marked with letters A to E. For patients for whom the maximum level of V _{C, the max} replenishment exceeds the structural maximum set level of the secondary tank replenishment, the latter can be used as the replenishment level.

In another advantageous embodiment of the dispensing method according to the disclosure, the number of replenishment steps can be further reduced. The method is explained with reference to FIG. 6 (B). The strategy here is that in cases where a bolus injection requires replenishment of the pump cylinder, the replenishment volume is set to V _C.max ; but it is calculated that after a complete bolus injection, the residual liquid medication in the secondary reservoir is equal to the permissible maximum replenishment level V _C.max . Thus, the pump cylinder is updated to _{V C, fill = V rem,} bolus + V C, max = V rem, bolus + V TDD * 20%. Moreover, V _{rem, bolus} is the residual volume of the bolus, which should still be introduced when there is a need for replenishment.

Obviously, after replenishing the pump, the filling level is higher than the maximum replenishment level. However, immediately after this, the volume again decreases to the maximum replenishment level due to the displacement of the residual volume V _{rem, bolus} bolus. Thus, the replenishment volume can be increased without increasing the possible dispensing error, since the excess filling volume would be introduced immediately in any case. In addition, in the event of a malfunction condition causing unwanted aeration of the secondary reservoir, this would be immediately detected by an air sensor. As a result, the number of replenishment stages is reduced even more, although the level of safety remains the same. In the example shown, approximately four replenishment stages A, B, C, D per day are required.

In yet another embodiment of the dispensing method according to the disclosure, it is not the absolute number of replenishment stages that is minimized, but the number of replenishment stages during periods of basal administration, i.e. between bolus administrations usually associated with food intake, as shown in FIG. 6 (D). If the secondary reservoir is to be replenished during a bolus injection, the cylinder is replenished only with the remaining volume of the V _{rem, bolus} bolus. At the end of the bolus injection, the pump cylinder is empty and replenished to the maximum level V _{C, max} replenishment. Thus, effectively, each replenishment stage during a bolus is divided into two replenishment stages. This strategy takes advantage of the fact that during a bolus, a small dosage error due to replenishment is masked by the physiological effects of a much larger bolus dose. Thus, the increased number of replenishment stages is less critical. However, during basal periods with significantly lower doses, when a dosing error would have a greater effect, the number of replenishment stages is minimized.

In some embodiments, the secondary reservoir is filled to a maximum level of V _{C, max} replenishment after each bolus injection or each bolus administration is greater than a given bolus volume threshold, even if the total bolus volume could be injected without replenishing the secondary reservoir, and the secondary reservoir is still partially filled after bolus administration. This ensures that the volume corresponding to the maximum replenishment level is always available for subsequent basal administration.

In the above methods, the secondary tank is usually completely empty before replenishment. It would also be possible to replenish the secondary reservoir still containing the liquid medication, for example, in front of the bolus, so that the secondary reservoir is filled to the maximum level V _{C, max} replenishment after bolus administration. However, completely emptying the pump has the advantage that errors in the volume or position of the piston do not accumulate. In addition, air can accumulate in the cylinder and, if air is present, it will be forced into the system downstream, where it can be detected by an air sensor.

Prior art air sensors can only distinguish between “air” and “no air” states at the detection point. In an infusion pump according to the disclosure, an air sensor is not only used to detect the presence of air. In addition, the amount of air in the entire hydraulic system downstream is continuously monitored favorably.

For this purpose, the device records all single administration events (which are identified by the subsequent number “i”) when the pump is active and liquid medication is administered within a certain period of time, for example 24 hours, including the time t _{i of} administration (the start of activation of the pump), nominally entered volume V _{dose, i} liquid medicament and the detected amount of V _{air, i} air. The indicated quantity is determined by accumulating time t _{air, i} during injection, when the air detector detects air in the hydraulic system: V _{air, i} = t _{air, i} S _dose , where S _dose is the pump flow during injection.

The system constantly calculates the scanning integral over the detected air volumes. If the amount of air that the sensor has passed in a certain period of time exceeds a certain threshold value, an error message may be generated that requires the user to take appropriate measures. In one favorable embodiment, different threshold values may be applied for different periods of accumulation.

Data recording can be implemented, for example, in the form of a FIFO registry of sufficient length in the memory of controller 22, as shown in FIG. 7 into which the data sets are entered. In the indicated figure, t _{admin, i} means the period of time from the start t _i of pump activation to the start t _{i + 1 of the} next pump activation. V _{dose, i} is the volume of the liquid medication usually administered during the indicated period by the metering device. It is indicated in millimeters of the length of the infusion tube used, but can also be indicated in nanoliters, cubic millimeters, insulin units, etc. The detected volume V _{air, i of} air is indicated in insulin units, but can also be expressed in other volume units, for example microliters. Other convenient units can also be applied here. In this example, two different basal doses are used during the day and the administration of one bolus is indicated.

A new data set is entered at the top of the registry, and the oldest data set appears at the bottom of the registry. The length of the registry is chosen so that it is enough to store at least data for the longest integration period.

In this example, two volumes of V _{air, 24h} , V _{air.Down of} accumulated air are continuously calculated and monitored. For a volume of V _{air, 24h of} air, data entries for the last 24 hours are estimated:

при этом n выбрано так, что

while n is chosen so that

Instead of a time period of 24 hours, any other suitable time period, for example 12 hours or 48 hours, can be applied. The value of n may change if varying administration periods are used. Each time a new dataset is entered into the FIFO, the accumulated air volume is recalculated.

V _{air, 24h} corresponds to the volume of air that the air sensor passed in a period of 24 hours. If this value exceeds a certain threshold value, V _{air, 24h} > V _{air, max, 24h} , the corresponding signal can be triggered so that the necessary measures can be taken. By controlling V _{air, 24h} , the infusion pump can control the amount of air that is introduced to the patient. At the same time, this value also represents the accumulated dosing error due to air, since the actually administered liquid medication is less than the nominal dose administered: V _{dose, real, 24h} = V _{dose, 24h} -V _{air, 24h} . In addition, the correct long-term functioning of the hydraulic system can be monitored, since a leak can be detected, which only appears after the filling procedure.

The second controlled volume V _{air, down} contains data entries that correspond to the dosing volume, which is equal to the volume of the hydraulic system downstream of the air sensor, V _Down = V _E + V _F , thereby representing the amount of air currently present in the system below downstream, but not yet administered to the patient.

при этом m выбрано так, что

while m is chosen so that

Again, each time a new dataset is entered into the FIFO, the accumulated air volume is recalculated. If the value exceeds a certain threshold value, V _air.Down > V _{air, max, Down} , an alarm can be triggered so that the necessary measures can be taken. By controlling V _air.Down , the infusion pump can control the amount of air that will be introduced to the patient if work continues. In addition, this value is also associated with a potential metering error in the event of a change in pressure or temperature, since in this case the air in the system would expand downstream and the liquid would be introduced unintentionally. V _air.Down can also be used to monitor the proper operation of the pump and to detect leaks.

Alternatively or additionally, the amount of air detected can also be controlled in relation to the volume of liquid medication administered. For example, an infusion pump can monitor if the ratio V _{air, 24h} / V _{dose, 24h} between air and liquid medication does not exceed a certain threshold value.

In one embodiment of the dispensing method discussed above, the amount of air introduced to the patient can be determined very accurately by the approach shown in FIG. 8. The accumulation range for 24 hours and for the system downstream does not overlap, as discussed above, but is located in the sequence

при этом m выбрано так, что

а

while m is chosen so that

but

при этом k выбрано так, что

while k is chosen so that

Again, V _{air, Down} describes the air in the system downstream, and V ' _{air, 24h} describes the amount of air that actually left the infusion tube and was introduced to the patient over a period of 24 hours.

The present invention is not limited in the scope of the specific embodiments described herein. In fact, various modifications of the present invention, in addition to those described herein, will be apparent to those skilled in the art from the foregoing description and the accompanying drawings. Thus, such modifications are intended to be included in the scope of the attached claims. Additionally, throughout the description reference is made to various sources, the disclosures of which, each of which are included in the present application as a reference in its entirety.

Claims (9)

1. A metering device (12) for an outpatient infusion pump (10) with a cylindrical pump containing a cylinder (14) and a piston (16), configured to move along the longitudinal axis (48) of the cylinder, the piston having a piston head (17) and the piston rod (18), the piston rod having a segment (51) provided with tags that are provided in the form of a plurality of optically detectable bands (64, 65) located on the segment (51),
characterized in that the metering device (12) comprises a valve which is configured to be in two operating states and a window (60) provided on the cylinder (14) to provide optical access to the optically detectable bands (64, 65), wherein the window optical access (60) is designed in such a way that it provides optical access to optically detectable bands (64, 65) when the valve is in one of two operating states, and does not provide optical access to optically detectable bands (64, 65) when valve on oditsya between two operating states. 2. A dosing device according to claim 1, characterized in that the optically detectable strips (64, 65) are located on the segment (51) along the circumference of the rod and parallel to the longitudinal axis. 3. Dosing device according to claim 1, characterized in that the optically detectable strips are made in the form of a plurality of circumferential rings located on a segment (52) along the longitudinal axis. 4. Dosing device according to one of paragraphs. 1-3, characterized in that the piston rod (18) contains a threaded segment (50), interacting with the threaded portion (54) of the cylinder so that the piston moves along the longitudinal axis when the piston rod rotates around the specified axis. 5. Dosing device according to claim 4, characterized in that the segment (51) is located between the threaded segment (50) and the piston head (17). 6. Dosing device according to claim 4, characterized in that the segment (51) at least partially overlaps the threaded segment (50). 7. Dosing device according to one of paragraphs. 1-3, characterized in that the valve (35) is designed to alternately connect the internal volume (13) of the cylinder (14) in the first state with the inlet channel (24), and in the second state with the exhaust channel (25), the valve (35) comprises a valve seat (40) and a valve element (44), the valve element (44) being implemented as part of the cylinder (14), and the cylinder (14) being mounted for rotation or sliding in the support (42) of the valve seat (40) so that the valve can switch between two states by turning the cylinder (14) with the valve element on enny angle along the longitudinal axis (48) of the cylinder (14) or by moving the cylinder with the valve member (44) relative to the seat (40) of the valve for a certain distance along the longitudinal axis. 8. Infusion pump (10) with a metering device (12) according to one of paragraphs. 1-7, containing:
- primary reservoir (11) and
- a drive unit (20) for moving the piston (16) in two directions. 9. The infusion pump according to claim 8, characterized in one or more blocks (56, 58) of sensors that are configured to detect marks (64, 65) of the piston (16) of the metering device (12) mounted in the infusion pump, and an evaluation device which, based on a signal received from one or more sensor blocks (56, 58), is able to determine the absolute position of the piston inside the cylinder of the metering device and / or the relative movement of the piston inside the cylinder.

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