Method for preventing dry running of the irrigation system of a medical pump

Abstract

The invention relates to a method and a device for preventing dry running of a medical irrigation pump which is used to distend body cavities. The technical problem is to prevent air from being drawn in and conveyed from a fluid reservoir as it empties, without requiring additional external sensors in the irrigation system. In order to solve this problem, a control and evaluation unit of the pump indirectly monitors the fill level of the reservoir. In a preferred embodiment, the hydrostatic pressure in the supply line to the pump is determined and monitored. An alarm is triggered when the pressure or its rate of change reaches a critical threshold value, indicating that the reservoir is empty. In alternative embodiments, dry running is detected by calculating the remaining volume in the reservoir or by analysing characteristic changes in the frequency spectrum of the pump operating noise. The associated device comprises a peristaltic pump and a correspondingly designed control and evaluation unit for carrying out the method.

Description

[0001] Methods for preventing the flushing system of a medical pump from running dry

[0002] Subject of the invention

[0003] The invention relates to a method and a device for preventing a medical irrigation pump used for dilating body cavities from running dry.

[0004] The technical problem is to prevent the intake and conveyance of air from an emptying liquid reservoir without requiring additional external sensors in the flushing system.

[0005] To solve this problem, it is proposed that a control and evaluation unit of the pump indirectly monitors the reservoir level. In a preferred embodiment, the hydrostatic pressure in the supply line to the pump is determined and monitored. An alarm is triggered when the pressure or its rate of change reaches a critical threshold, indicating an empty reservoir.

[0006] background

[0007] The invention relates to a method and a device for preventing a medical rinsing pump from running dry.

[0008] Numerous medical examinations and treatment methods involve the introduction of medical irrigation solutions into body cavities. The purpose of the pumped irrigation solution is generally not only to flush the cavity, for example, to remove blood and / or tissue, but also to dilate it to some extent, creating space for endoscopes and / or surgical instruments. The pumps used are frequently peristaltic pumps. The irrigation solutions are typically stored in a reservoir, such as a reservoir bag, which is connected to the suction side of the pump via tubing.

[0009] During prolonged medical procedures, there is a risk that the reservoir will run dry, causing the pump to draw in air and pump it into the body cavity. This is known as "pump running dry." While pumping air into body cavities is harmless to patients because the air does not enter the bloodstream, it poses the risk of the body cavity collapsing, as air, unlike liquids, is compressible. In practice, preventing pump running dry is often achieved through monitoring by medical personnel, but this is prone to error. Other known solutions involve the use of additional detection systems. For example, German patent DE 69 030 132 T2 describes a detector using ultrasound or optics to detect air in a tube. US patent 5,800,383 A discloses a system with a removable cartridge accumulator that acts as an air trap and is equipped with its own level sensors.However, such additional, dedicated sensors in the rinsing system increase costs, complexity, and the amount of disposable material required.

[0010] Object of the invention

[0011] The present invention therefore aims to provide a method and a device that reliably detect and prevent a medical rinsing pump from running dry, without requiring additional, external detection systems in the rinsing system.

[0012] The application of medical roller pumps for distending body cavities works as follows: A fluid bag (reservoir) is typically attached to a holder above the pump, with a fluid connection to the body cavity. The attached tubing set transports the fluid from the reservoir to the body cavity in a sterile manner. This is achieved by means of a segment that is clamped into the impeller of a peristaltic pump, which uses peristalsis to propel the fluid (i.e., pushes partial volumes along a circular arc towards the body cavity). The peristaltic pump has a preload to ensure secure occlusion. The occluding impeller allows the fluid to be pumped into the body cavity at a predetermined pressure. This pressure is usually regulated by a pressure sensor located directly at the pump's outlet, i.e., between the pump and the body cavity.The reason for this positioning is that it is not economical to place a single-use pressure sensor directly into the body cavity. Furthermore, a pressure sensor located inside the body cavity would take up space that is not available, especially in narrow body cavities (e.g., the knee joint). A so-called transmission diaphragm can be used for pressure measurement. The part of the tubing that is clamped into the roller wheel is usually made of silicone to ensure better flexibility and thus improved pumping performance. Other parts of the tubing can be made of [material not specified in the original text]. _,It is made of less expensive PVC. The coupling element between the silicone hose and the PVC hose is a hollow body with two connectors and a silicone membrane that, through deformation, allows pressure measurement using a corresponding sensor. The coupling element is typically clamped into a holder that, on the one hand, allows for a secure mounting of the hose and, on the other hand, also houses the pressure sensor.

[0013] Many pumps have a coupling element like the one described above on the pump outlet side (Type A). Some pumps also have a corresponding coupling device with pressure measurement capability on the pump inlet side (Type B). Another possibility is that coupling elements are provided on both the inlet and outlet sides (Type C). Pumps without any coupling elements with pressure measurement capability (Type D) are rarely used anymore.

[0014] It should be noted that the measured pressure at the outlet side of the pump (inlet pressure) does not correspond to the pressure in the body cavity, as the flow resistance in the hose reduces the pressure in the body cavity.

[0015] The object of the invention is to detect when the reservoir is empty before air is transported into the hose section behind the roller wheel. Any air pumped in there is flushed through the body cavity, since the roller pump must ensure flushing during the medical procedure to remove detached tissue particles or escaping blood and thus maintain visibility. Smaller bubbles can be flushed through without difficulty, while larger quantities of air can cause the body cavity to dry out and, because air is compressible, collapse. Solution to the problem according to the invention.

[0016] The above-mentioned problem is solved by a method for preventing dry running with the features of claim 1 and by a medical device with the features of claim 10.

[0017] The invention provides that a control and evaluation unit of the pump determines the hydrostatic pressure in the suction-side supply line and monitors its temporal profile. If this pressure or its rate of change reaches a predefined threshold, indicating an emptying liquid reservoir, the control unit triggers an alarm. The pressure can be determined either by direct measurement using a suction-side pressure sensor or indirectly by analyzing the motor current during a brief reverse pumping action.

[0018] The invention therefore relates to a method for preventing a rinsing pump in a medical device from running dry, wherein a fluid reservoir is connected to the suction side of a peristaltic pump via a supply line, and wherein the peristaltic pump has a control and evaluation unit, characterized by the steps of: determining the hydrostatic pressure (Pwat) in the supply line; monitoring the determined hydrostatic pressure (Pwat) over time by the control and evaluation unit; and triggering an alarm by the control and evaluation unit when the hydrostatic pressure (Pwat) falls below a predetermined threshold or when the rate of change of the hydrostatic pressure (Pwat) exceeds a predetermined threshold.

[0019] The invention relates in particular to a method wherein the medical device has a pressure sensor on the suction side of the peristaltic pump, and wherein the hydrostatic pressure (Pwat) is determined by direct measurement using this pressure sensor. Alternatively, the invention also relates to a method wherein the peristaltic pump has current sensors for measuring the current consumption of its motor, and wherein determining the hydrostatic pressure (Pwat) comprises the following steps: a) stopping the delivery movement of the peristaltic pump; b) initiating reverse delivery for a predetermined, short duration; c) measuring the current consumption of the motor during reverse delivery using the current sensors; and d) calculating the hydrostatic pressure (Pwat) from the measured current consumption by the control and evaluation unit.

[0020] Further advantageous embodiments of the invention are the subject of the dependent claims.

[0021] Description of the character

[0022] Figure 1 schematically shows a medical device for dilating body cavities, which is suitable for carrying out the method according to the invention.

[0023] Detailed description of the invention

[0024] The present invention is explained in more detail below with reference to the accompanying figure.

[0025] The device shown in Figure 1 comprises a fluid reservoir (1), typically in the form of a fluid bag, containing a rinsing solution such as sodium chloride or sugar solution. The fluid reservoir (1) is connected via a fluidic port (2) and a supply line (3) to the suction side of a peristaltic pump (5). The peristaltic pump (5) has an impeller (4) which, by its peristaltic action, pumps partial volumes of the rinsing solution through the fluid line (7) into the body cavity of a patient (10). For this purpose, the fluid line (7) is connected via a port (8) to a medical instrument (9), for example, an endoscope, which is inserted into the body cavity (10).

[0026] The device further comprises a control and evaluation unit (not shown) which is connected to the various components of the pump (5) and controls and monitors their operation. In the described arrangement, the liquid column in the liquid reservoir (1) and in the supply line (3) generates a hydrostatic pressure (Pwat) that acts on the suction side of the peristaltic pump (5). A cavity pressure (Pcav) prevails within the body cavity (10). The delivery pressure generated by the pump (5) and measured on the pressure side is referred to as Pdrv.

[0027] To carry out the method according to the invention, the device can have different sensor configurations depending on the embodiment.

[0028] In a first embodiment, corresponding to a pump of type B or C as described, a pressure sensor (11) is arranged on the suction side of the pump (5). This pressure sensor (11) is directly connected fluidically to the supply line (3) and is capable of directly measuring the hydrostatic pressure (Pwat). The control and evaluation unit is configured to continuously or at regular intervals monitor the measured values ​​of the pressure sensor (11). If the measured absolute pressure (Pwat) falls below a predefined threshold, for example, 45 mbar, 40 mbar, or 30 mbar, or if the rate of pressure decrease (the rate of change) exceeds a predefined value, for example, 15 mbar / minute or 20 mbar / minute, the control and evaluation unit interprets this as a sign of an empty fluid reservoir (1) and triggers an alarm.

[0029] In a second embodiment, corresponding to a pump of type A described above, only one pressure sensor (6) is present on the pressure side of the pump (5). Since the occlusive effect of the impeller (4) mechanically separates the pressure sensor (6) from the supply line (3), the hydrostatic pressure (Pwat) cannot be measured directly. In this configuration, the control and evaluation unit is set up to determine the pressure (Pwat) indirectly. For this purpose, the conveying movement of the impeller (4) is first stopped. Subsequently, a brief reverse conveying action is initiated, during which the impeller (4) rotates in the opposite direction. During this reverse conveying action, the current consumption of the pump motor is measured via current sensors (12) not shown. The control and evaluation unit calculates the hydrostatic back pressure (Pwat) from the measured current consumption, which is proportional to the required torque.The torque consists of a constant component (rolling resistance of the pump) and a variable component (the hydrostatic pressure P). wa t) together. By regularly repeating this measurement cycle, for example every one to five minutes, the control and evaluation unit can monitor the pressure (Pwat) trend and trigger an alarm when the above-mentioned threshold values ​​are reached.

[0030] In a third embodiment, corresponding to a type C pump without pressure sensors, the initial fill volume of the liquid reservoir (1) is entered into the control and evaluation unit. This can be done manually by the user or automatically by technical means such as reading a barcode or an RFID label on the hose set. The control and evaluation unit knows the delivery volume per revolution of the roller impeller (4) and calculates the remaining residual volume by continuously subtracting the delivered volume. An alarm is triggered if the residual volume falls below a percentage threshold, for example, 10%, of the initial fill volume.

[0031] In a fourth embodiment, the device includes a microphone (not shown) connected to the control and evaluation unit. Evaluation software in the control unit analyzes the frequency spectrum of the operating noise of the roller wheel (4). The software is trained to detect a characteristic change in the spectrum that occurs when the pump (5) begins to draw in a mixture of air and liquid instead of pure liquid. An alarm is triggered when this change is detected.

[0032] For further optimization, the control and evaluation unit can be configured to apply a combination of at least two of the described methods. When an alarm is triggered, the pumping operation (5) is preferably interrupted and can only be reactivated after a user confirms the change of the reservoir (1) to ensure the safety of the process. Reference list

[0033] (1) Fluid reservoir for the rinsing solution (fluid bag) (2) Fluidic connection

[0034] (3) Supply line

[0035] (4) Roller wheel of the peristaltic pump

[0036] (5) Peristaltic pump

[0037] (6) Pressure sensor on the pressure side of the pump

[0038] (7) Fluid conduit to the patient's body cavity (8) Connection to medical instrument

[0039] (9) medical instrument (e.g. endoscope)

[0040] (10) Patient with body cavity

[0041] (11) Pressure sensor on the suction side of the pump

[0042] (12) Pump current sensors (not shown)

[0043] (Pwat) Hydrostatic pressure of the water column

[0044] (P cav ) Pressure in the body cavity

Claims

Patent claims: 1.) Method for preventing a flushing pump (5) in a medical device from running dry, wherein a liquid reservoir (1) is connected to the suction side of a peristaltic pump (5) via a supply line (3), and wherein the peristaltic pump (5) has a control and evaluation unit, characterized by the steps: Determining the hydrostatic pressure (Pwat) in the supply line (3); Monitoring of the specific hydrostatic pressure (Pwat) over time by the control and evaluation unit; and Triggering an alarm by the control and evaluation unit when the hydrostatic pressure (Pwat) falls below a predetermined threshold or when the rate of change of the hydrostatic pressure (Pwat) exceeds a predetermined threshold. 2.) Method according to claim 1, characterized in that the medical device has a pressure sensor (11 ) on the suction side of the peristaltic pump (5), and that the determination of the hydrostatic pressure (Pwat) is carried out by a direct measurement using this pressure sensor (11). 3.) Method according to claim 1 , characterized in that the peristaltic pump (5) has current sensors (12) for measuring the current consumption of its motor, and that determining the hydrostatic pressure (Pwat) comprises the following steps: a) Stopping the conveying motion of the peristaltic pump (5); b) Initiating reverse conveying for a predetermined, short duration; c) Measuring the current consumption of the motor during reverse conveying using the current sensors (12); and d) Calculating the hydrostatic pressure (Pwat) from the measured current consumption by the control and evaluation unit. 4.) Method according to claim 2, characterized in that the threshold value for the hydrostatic pressure (Pwat) is 30 mbar. 5.) Method according to one of claims 1, 2 or 4, characterized in that the threshold value for the rate of change of the hydrostatic pressure (Pwat) is 15 mbar / minute. 6.) Method according to claim 3, characterized in that the reverse conveyance is only carried out to a small extent, so that no suction from the patient's body cavity takes place. 7.) Method according to one of the preceding claims, characterized in that the monitoring of the hydrostatic pressure (Pwat) is carried out at regular intervals of one to five minutes. 8.) Method according to one of the preceding claims, characterized in that after the alarm is triggered, the delivery of the peristaltic pump (5) is interrupted. 9.) Method according to claim 8, characterized in that the pumping is only reactivated after a user has confirmed the change of the liquid reservoir (1). 10.) Medical device for preventing a rinsing pump (5) from running dry, comprising: a peristaltic pump (5) with a suction side provided for connection to a supply line (3) from a fluid reservoir (1); and a control and evaluation unit connected to the peristaltic pump (5), characterized in that the control and evaluation unit is configured to: determine the hydrostatic pressure (Pwat) in the supply line (3); monitor the determined hydrostatic pressure (Pwat) over time; and trigger an alarm when the hydrostatic pressure (Pwat) falls below a predetermined threshold or when the rate of change of the hydrostatic pressure (Pwat) exceeds a predetermined threshold.Device according to claim 10, characterized in that it further comprises a pressure sensor (11) on the suction side of the peristaltic pump (5), and that the control and evaluation unit is configured to determine the hydrostatic pressure (Pwat) by direct measurement using this pressure sensor (11). Device according to claim 10, characterized in that the peristaltic pump (5) has current sensors (12) for measuring the current consumption of its motor, and that the control and evaluation unit is configured to perform steps a) to d) of claim 3 for determining the hydrostatic pressure (Pwat). A method for preventing a rinsing pump (5) in a medical device from running dry, wherein a liquid reservoir (1) is connected to a peristaltic pump (5) via a supply line (3), and wherein the peristaltic pump (5) has a control and evaluation unit, characterized by the steps of: inputting the initial fill volume of the liquid reservoir (1) into the control and evaluation unit; monitoring the revolutions of the roller wheel (4) of the peristaltic pump (5) by the control and evaluation unit; calculating a residual volume in the liquid reservoir (1) by subtracting a predetermined delivery volume from the initial fill volume for each revolution of the roller wheel (4); and triggering an alarm by the control and evaluation unit when the calculated residual volume falls below a predetermined percentage threshold of the initial fill volume.Method for preventing a rinsing pump (5) in a medical device from running dry, wherein a fluid reservoir (1) is connected to a peristaltic pump (5) via a supply line (3), and wherein the peristaltic pump (5) has a control and evaluation unit, characterized by the steps of: detecting the operating noise of the peristaltic pump (5) by means of a microphone connected to the control and evaluation unit; analyzing the detected operating noise by evaluation software installed in the control and evaluation unit to detect a change in its frequency spectrum; and triggering an alarm by the control and evaluation unit when the evaluation software detects a predetermined change in the frequency spectrum characteristic of dry running.

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