Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
  • A61M1/36—Other treatment of blood in a by-pass of the natural circulatory system, e.g. temperature adaptation, irradiation ; Extra-corporeal blood circuits
  • A61M1/3621—Extra-corporeal blood circuits
  • A61M1/3643—Priming, rinsing before or after use
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M1/00—Suction or pumping devices for medical purposes; Devices for carrying-off, for treatment of, or for carrying-over, body-liquids; Drainage systems
  • A61M1/14—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis
  • A61M1/16—Dialysis systems; Artificial kidneys; Blood oxygenators ; Reciprocating systems for treatment of body fluids, e.g. single needle systems for hemofiltration or pheresis with membranes
  • A61M1/168—Sterilisation or cleaning before or after use
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61M—DEVICES FOR INTRODUCING MEDIA INTO, OR ONTO, THE BODY; DEVICES FOR TRANSDUCING BODY MEDIA OR FOR TAKING MEDIA FROM THE BODY; DEVICES FOR PRODUCING OR ENDING SLEEP OR STUPOR
  • A61M39/00—Tubes, tube connectors, tube couplings, valves, access sites or the like, specially adapted for medical use
  • A61M39/10—Tube connectors; Tube couplings

Definitions

• the invention relates to an access system for a medical device, which has a housing body in which an inner pipe section for transporting a medical liquid is formed, which is enclosed by an outer pipe section to form an empty space for receiving a disinfecting liquid, the housing body having one of a Closing element has closable opening.
• the invention relates to a monitoring system with such an access system and a medical treatment device with such a monitoring system. Furthermore, the invention relates to a method for monitoring an access system for a medical device.
• access systems are used in medical technology that allow a sterile connection of a hose line in order to be able to supply or withdraw a liquid.
• Such access systems are also referred to as a port.
• the patient's blood is diluted by adding substituate.
• the substituate can be provided in containers or obtained from dialysate in the dialysis machine via a sterile filter.
• Hemodialysis machines which have an access system to which a hose line is connected in order to be able to supply the substituate provided by the dialysis machine to the extracorporeal circuit.
• the access system is sealed with a sealing cap to prevent contamination. Before connecting the hose line, the sealing cap is removed. With the access system, care must be taken to ensure that germs or pathogens that can adhere to the access system in daily practice do not get into the patient's blood. Therefore, the access system is generally flushed with a disinfectant solution.
• the disinfecting solution can, for example, a heated and thus germ-killing liquid (dialysate, substitute, RO water), which can be provided by the dialysis machine.
• a chemical disinfectant solution can also be used. It is essential that all parts of the access system that can come into contact with the patient are flushed with the disinfectant solution in order to rule out contamination. After the disinfection, no residues of the disinfectant solution must remain to ensure that the blood does not come into contact with the disinfectant solution.
• residues of any conductive liquid can be recognized with the aid of the invention, for example also from substitution solution, which can also be used, among other things, for flushing and filling the extracorporeal blood circuit.
• the disinfection of the access system can take place during a shift before each dialysis treatment. However, for reasons of cost and time, provision can also be made for disinfection in the dialysis center to only take place before or after each shift (e.g. at night). It is therefore of particular interest to avoid contamination that can result from handling the device during a shift and, if necessary, to carry out further disinfection or to prevent further treatment. In addition, it is of interest to determine during disinfection whether the critical parts of the access system come into contact with disinfectant solution. It is also of interest to check the access system for leaks. In particular, it is of interest to check the access system for leaks while it is being used as intended, ie when the substitution solution is being made available
• the invention is based on the object of creating an access system for a medical device, in particular for a dialysis machine, in particular for removing a medical liquid, for example a substitute, which allows reliable monitoring of its proper condition during and after disinfection.
• an object of the invention is a monitoring system with such an access system and a medical treatment device with such a monitoring system to create, which allows a reliable monitoring of the proper condition during and after the disinfection.
• Another object of the invention is to specify a method for monitoring an access system for a medical device, with which reliable monitoring of the access is possible.
• the access system according to the invention for a medical device has a housing body in which an inner pipe section for transporting a medical liquid is formed, which is enclosed by an outer pipe section to form an empty space for receiving a disinfecting liquid, the housing body having an opening that can be closed by a closure element having.
• the access system according to the invention is intended in particular for removing a medical liquid.
• the access system can also be used for the supply of a medical liquid. Consequently, the opening of the housing body can be used for removing or supplying a medical liquid.
• the medicinal liquid can be, for example, a substituate.
• the housing body allows the access system to be attached to the medical device, for example a medical treatment device, in particular a hemodialysis machine.
• the medicinal fluid such as substituate
• the inner tubing section flows through the inner tubing section.
• disinfectant fluid flows through the empty space that is closed in a liquid-tight manner by the closure element, so that the relevant parts of the access, in particular the area around the inner pipeline section, are flushed with disinfectant fluid.
• the access system is characterized in that a measuring electrode and at least one counter-electrode are arranged in the housing body in such a way that the measuring electrode interacts with the counter-electrode via the empty space.
• the measuring electrode allows an electrical signal to be coupled in or fed in, so that a current flowing between the measuring electrode and the counter-electrode or a voltage present between the measuring electrode and the counter-electrode can be evaluated.
• the evaluation of a current and a voltage also includes the measurement of a (complex) resistance (impedance or reactance measurement). Based on the evaluation of current or voltage (complex resistance), the presence or absence of liquid or moisture in the void space can be inferred and/or whether a particular liquid is present in the void space is, ie one liquid can be distinguished from another liquid.
• the empty space is at least partially filled with disinfectant.
• Several counter-electrodes can be provided to monitor the complete filling or detection of only partial filling of the empty space (filling level) with disinfecting liquid, with the counter-electrodes each being assigned to a specific area or section of the empty space.
• the access system After the access system has been disinfected, it can be checked whether there is still moisture in the empty space, which forms a conductive connection between the measuring electrode and counter-electrode, ie whether there is still moisture in the port. It is assumed that a dry port is generally germ-free, since practice has shown that most germs are bound to moisture.
• the access system comprises a connector that can be inserted into the opening for removing or supplying the medical liquid, which has a pipe section that extends into the empty space and can be connected to the inner pipe section of the housing body in a liquid-tight manner, with the connection point between the pipe section of the housing body and the tubing portion of the connector is in the void.
• the access system can be checked for leaks during operation. If liquid is found in the empty space, which is dry per se, it can be concluded that there is a leak in the connection point between the pipe sections of the housing body and the connector, which is located in the empty space.
• the measuring electrode is a pin that is electrically insulated from the housing body and extends into the empty space.
• the pin can be provided with an electrical connection on the housing side.
• the counter-electrode is formed by at least part of the inner pipe section.
• This embodiment is advantageous for detecting liquid, in particular substituate, which can escape at the connection point between the pipe sections of the housing body and the connector.
• at least part of the inner pipeline section can consist of a conductive material or at least part of the outer wall of the inner pipeline section can be provided with a coating made of a conductive material.
• the at least one counter-electrode is formed by at least part of the outer pipeline section.
• the empty space is to be recognized as being filled with disinfecting liquid.
• at least part of the outer Pipe section consist of a conductive material or be provided at least a part of the inner wall of the outer pipe section with a coating of a conductive material.
• a different resistance is established between the measuring electrode and the counter-electrode. The more the empty space is filled, the more current paths form, so that the resistance decreases.
• a plurality of counter-electrodes are formed on the outer pipeline section, these can be arranged in such a way that specific conductive paths to the individual counter-electrodes are formed depending on the fill level. Both can be monitored by a corresponding evaluation of the signals, for example by a deviation from a reference value.
• the access system can also have both embodiments, so that one or more current paths between the measuring electrode and the inner pipe section and the outer pipe section can be detected.
• the monitoring system according to the invention which includes the access system according to the invention, has a device for generating an electrical signal, which is electrically connected to the measuring electrode and the at least one counter-electrode, and an evaluation and computing device, which is configured in such a way that a between the measuring electrode and the current flowing at least one counter-electrode or a voltage present between the measuring electrode and the at least one counter-electrode is evaluated.
• the evaluation and computing device can be configured in such a way that a current flowing between the measuring electrode and the at least one counter-electrode or a voltage between the measuring electrode and the at least one counter-electrode is evaluated in such a way that the presence or absence of a liquid or moisture present in the void space is closed or may be configured to detect whether a particular liquid is present in the void space.
• the known evaluation methods can be used.
• the evaluation and computing device can be configured in such a way that a control or alarm signal is generated if liquid or moisture in the empty space is inferred and/or a control or alarm signal is generated if an in liquid or moisture in the void is not closed.
• the control or message signal can be used, for example, to intervene in the machine control of the medical device, for example to prevent further treatment or to issue an alarm.
• the operating personnel can also be prompted to carry out a disinfection on a display.
• the means for generating an electrical signal is therefore preferably configured in such a way that an electrical signal is generated at successive time intervals. Since the measuring signal is only applied for a short time, the average current is smaller than with continuous application.
• a coupling capacitance can also be provided between the evaluation and computing device and the measuring electrode.
• a further preferred embodiment provides that the device for generating an electrical signal has a frequency generator for generating an AC voltage or AC signal.
• the evaluation and computing device can have a device for rectifying an AC voltage signal, the evaluation and computing device being configured in such a way that the rectified AC voltage signal (DC voltage) is compared with a reference value. For the presence of liquid in the void or Moisture in the void can then be inferred if the rectified AC signal is less than the reference value.
• the fill level can be inferred based on the magnitude of the DC voltage, ie based on the electrical resistance.
• FIG. 1 shows a hemodialysis device according to the invention in a greatly simplified schematic representation, the hemodialysis device having the monitoring system according to the invention with the access system according to the invention.
• FIG. 2 shows an exemplary embodiment of the access system according to the invention in a sectional view
• FIG. 3 shows an exemplary embodiment of the monitoring system according to the invention
• 4 shows an electrical equivalent circuit diagram to illustrate the current flow
• 5 shows the time profile of the AC voltage signal
• Fig. 6 shows the attenuation of the AC voltage signal as a function of frequency
• FIG. 7 shows an exemplary embodiment of the evaluation and computing device of the monitoring system.
• FIG. 1 shows, as an example of a medical treatment device 1, an extracorporeal blood treatment device in a highly simplified schematic representation, which has a monitoring system 2 for monitoring access to the medical treatment device.
• the present extracorporeal blood treatment device is a haemo(dia)filtration device which has a dialyzer 3 which is separated by a semipermeable membrane 4 into a blood chamber 5 through which blood flows and a dialysis fluid chamber 6 through which dialysis fluid flows.
• the blood chamber 5 is part of an extracorporeal blood circuit I, while the dialysis fluid chamber 4 is part of a dialysis fluid system II of the hemo(dia)filtration device.
• the extracorporeal blood circuit I comprises an arterial blood line 7, which leads to the inlet 5a of the blood chamber 5, and a venous blood line 8, which branches off from the outlet 5b of the blood chamber 5 of the dialyzer 3.
• the patient's blood is conveyed through the blood chamber 5 of the dialyzer 1 with an arterial blood pump 9 which is arranged on the arterial blood line 7 .
• the blood lines 7, 8 and the dialyzer 3 form a disposable intended for one-time use, which is placed in the dialysis machine for the dialysis treatment.
• the fresh dialysis fluid is made available in a dialysis fluid source 10 .
• a dialysis fluid supply line 11 leads from the dialysis fluid source 10 to the inlet 6a of the Dialysis fluid chamber 6 of the dialyzer 3.
• a dialysis fluid discharge line 12 leads from the outlet 6b of the dialysis fluid chamber 6 to a drain 13.
• a dialysis fluid discharge line 12 has a dialysis fluid pump 14 connected thereto.
• substitution liquid can be supplied to the extracorporeal blood circuit I via a substituate line 15b.
• the substituate line 15b is connected to a line section of the arterial blood line 7 .
• the substituate can be a liquid provided in a substituate source 16 and pumped with a substituate pump 17 .
• Substituate source 16 can be a container filled with finished substituate.
• the substituate can also be produced by filtering the dialysate through sterile filters from the dialysis liquid source 10 in the extracorporeal blood treatment device (not shown in FIG. 1).
• Substituate line 15b is part of the disposable intended for single use.
• an access system P port
• a fluid connection 15a is provided for connecting the substituate source 16 to the access system P, among other things.
• the access system P can be disinfected before or after a dialysis treatment or at certain time intervals, for example once a day.
• the disinfecting liquid for disinfecting the access system P is provided in a container 18 which can take the place of the substituate source 16 .
• the disinfecting liquid is connected to the access system P via the fluid connection 15a.
• the access system P is flushed with disinfectant liquid by the Disinfecting liquid is conducted from the container 18 to the access system P and removed from there again via a drain or return line 19.
• the blood treatment device 1 has a monitoring system 20, shown only in outline in FIG. 1, for monitoring the status of the access system.
• the access system P has a multi-part housing body 21 which is attached to the housing 1A of the blood treatment device 1 so that it is freely accessible to the operator.
• An inner pipe section 22 for transporting the substitution liquid or disinfecting liquid is formed in the housing body 21 .
• the inner pipe section 22 is surrounded by an outer pipe section 24, which tapers towards the right in FIG. 2, forming an empty space 23 for receiving the disinfecting liquid.
• the housing body 21 has an opening 25 which can be closed with a closure element (not shown in FIG. 2).
• a closure element not shown in FIG. 2
• At the outer end of the inner pipe section 22 there is a connection 26 for the fluid connection 15a leading to the substituate source 16 or to the disinfecting liquid container 18 (FIG. 1).
• a suitable connector 27 can be inserted into the opening 25 in order to remove the substituate.
• the connector 27 has an inner piping portion 28A extending into the void space, which is liquid-tightly connected to the inner piping portion 22 of the case body 21 when the connector 27 is connected.
• the inner pipeline section 28A is surrounded by a protection against accidental contact 28B.
• the opening formed by the inner pipeline section 28A and the opening formed by the contact protection 28B are not in one plane but are spaced apart from one another in such a way that touching the inner pipeline section 28A of the connector 27 is made difficult or impossible.
• the connection point 29 between the tubing section 22 of the housing body and the tubing section 28A of the connector 27 is approximately at the center of the void 23.
• the disinfectant flows into the empty space 23 via the connection 26 which is connected to the disinfectant container 18 .
• the disinfectant is discharged via the channel 38b, which is connected to the discharge or return line 19 (FIG. 1).
• the disinfectant that has flowed out or been displaced from the empty space 23 can be collected in a further container (not shown in FIG. 1) and then disposed of, or it can be discarded via a drain.
• sterile air is fed into the empty space via an opening 38A.
• the sterile air is compressed here, for example by a compressor, and fed into the empty space 23 .
• This compressed air can be used to displace any liquid from the empty space, for example to an opening 38B.
• the access system P has a measuring electrode 30 .
• the measuring electrode 30 is a pin that is electrically insulated from the housing body 21 .
• the pin-shaped measuring electrode 30 sits in a receiving piece 31 made of an insulating material (e.g. PEEK), which is inserted into the housing body 21 .
• PEEK an insulating material
• One end of the pin-shaped measuring electrode 30 extends into the empty space 23, while the other end is led out of the housing body 21 for connecting an electric line.
• the measuring electrode 30 is arranged in such a way that it interacts with at least one counter-electrode 31 , 32 via the empty space 23 .
• At least part of the inner pipe section 22 functions as the first, inner counter-electrode 31, while at least part of the outer pipe section 24 functions as the second, outer counter-electrode 32.
• at least part of the inner pipe section 22 can consist of a conductive material or at least part of the outer wall of the inner pipeline section 22 can be provided with a coating 22A made of a conductive material.
• at least part of the outer pipe section 24 can consist of a conductive material or at least part of the inner wall of the outer pipe section 24 can be provided with a coating 24A made of a conductive material.
• the outer wall of the inner pipe section 22 is provided with a coating 22A and the inner wall of the outer pipe section 24 is provided with a coating 24A made of a conductive material.
• the monitoring system 2 has a device 33 for generating an electrical signal and an evaluation and computing device 34 which are shown schematically in FIG. 3 together with the access system P and the patient access 35 .
• the inner pipe section 22 and the outer pipe section 24 of the access system P are shown in Fig. 3 only in outline.
• the device 33 for generating an electrical signal comprises a controllable frequency generator 33A which generates an AC voltage signal V ac with a predetermined frequency, for example a sinusoidal signal with a frequency of 20 kHz.
• the frequency generator 33A can be controlled by a control unit (CPU1).
• the AC voltage can be generated, for example, with a VCO (voltage controlled oscillator) or an adjustable signal generator.
• the CPU1 can be implemented as a programmed microcontroller, for example.
• the device 33 for generating an electrical signal and the evaluation and computing device 34 are connected to the measuring electrode 30 via an electrical connecting line 35 .
• a first switch 36 is provided, which can be opened or closed with a control signal en_meas from a second control unit (CPU2).
• a reference resistor RRef is provided, which creates a connection between the connecting line 35 and earth when a second switch 37 closed is.
• the second switch 37 can be opened or closed with a control signal set_ref of the CPII2.
• the reference resistor RRef is used to check the function of the circuit, which is described below.
• a coupling capacitance C is provided in the connecting line 35, which can be designed as a Y-capacitor.
• Y Capacitors offer a high dielectric strength and reliably prevent breakdown of the capacitor and thus dangerous voltages on the measuring electrode.
• an electrical signal is applied to the measuring electrode 30 .
• This can be any voltage with any voltage profile, in particular an AC voltage. If a conductive path between measuring electrode 30 and counter-electrode 31, 32 is produced by a liquid residue, a current flow in the current path between measuring electrode and counter-electrode or a voltage drop across the resulting resistance between measuring electrode and counter-electrode can be measured.
• the pipeline section 22 (or 22A) functioning as the at least one counter-electrode 31 is grounded, which is shown in FIG. 3 . If several counter-electrodes are used, for example as in FIG. 2 (24 or 24A), these are also grounded. In the event of faulty or interrupted grounding, which is indicated in FIG. This must be avoided at all costs.
• the substituate containing conductive ions flowing in the fluid connection 15a and the substituate line 15b establishes a conductive flow connection directly to the patient's vascular system.
• the catheter In patients who have a central venous catheter to access their vascular system, for example in acute dialysis, the catheter is in the immediate vicinity of the heart to ensure sufficiently high blood flows in the extracorporeal blood circuit. In these patients in particular, high leakage currents are caused by capacitive coupling between the dialysis machine and fluid paths in the patient should be avoided at all costs.
• Increased leakage currents can occur in the event of an interruption in the ground connection of counter-electrode 31, as indicated in FIG.
• a conductive liquid connection can occur between the measuring electrode 30 and the vascular system of the patient, which results in a current i p . This current is higher, the worse the ground connection of the counter electrode.
• the total current i is limited by the internal resistance Ri of the source and the parallel connection of the series-connected individual resistances (impedances) Z sci + Z gn d and Z S c2 + Z S ub + Zp.
• Ri results from Rfb (FIG. 7) and the output resistance (not shown) of an operational amplifier OP1 at the input of the evaluation and computing device 34, which will be described in detail below.
• the coupling capacitor C is neglected here or is dimensioned in such a way that it has no relevant influence.
• Z sci is the resulting impedance of a conductive bridge between measuring electrode and counter electrode.
• Z gn d is the resulting impedance, which can be assumed here as a purely ohmic cable connection, the electrical connection of the counter-electrode to the protective conductor PE.
• Z SC 2 is the impedance that results from a conductive bridging between the measuring electrode 30 and the possible point of leakage in the port, for example at the connection point 29 of the inner, housing-side or connector-side pipeline sections.
• Z SU b is the impedance of the conductive liquid connection within the substituate line, which depends on the length and the diameter of the substituate line 15b (hose line) and on the ion content of the substituate.
• Z p is the resulting impedance between the exit point of the substituate in the patient's vascular system and the patient's ground, which depends, for example, on the patient's position and stature or on the patient's clothing. For example, the patient touching a grounded metal body, etc.
• the above quantities can be complex quantities.
• the current i p and in particular its amount is decisive for endangering the patient. If the grounding connection Z gn d is defective, ie the left current path in FIG. 4 is interrupted, the current i no longer branches into two paths, but flows exclusively via the right path and thus via the patient. It must be ensured that the current i p does not exceed an amount of 50pA (effective) in order to rule out health hazards even in the event of a fault, ie an interrupted earth connection of the counter electrode. According to the invention, increased leakage currents can be prevented by the following measures, which can be used individually or in combination.
• the device 33 for generating the excitation voltage V ac can be configured in such a way that the absolute value of the excitation voltage V ac is limited in such a way that a leakage current greater than 50 pA does not flow even in the event of a fault.
• the device 33 for generating the excitation voltage V ac can be configured in such a way that pulse-like measurements are carried out.
• the excitation voltage Vac is applied for only a short period, then it is turned off to be reapplied periodically. On average, a current results that is smaller than when the excitation voltage is applied continuously.
• FIG. 5 shows the waveform of the sinusoidal excitation voltage V ac with a frequency of 20 kHz.
• the excitation voltage V ac is present in the time interval T on .
• the CPU1 To apply the AC voltage, the CPU1 generates a control signal en_meas, so that the first switch 36 is closed.
• the effective leakage current l pe fr is calculated using the following equation.
• the device 33 for generating the excitation voltage V ac can be configured in such a way that a minimum frequency for the excitation voltage Vac is specified.
• Fig. 6 shows that the resulting impedance of the right current path (Fig. 4), which is decisive for the magnitude of the leakage current, increases with increasing frequency. Consequently, the attenuation D of the signal also increases with increasing frequency f.
• the excitation frequency is selected in such a way that the limit value of the leakage current cannot be exceeded, for example 20 kHz, even in the event of a fault.
• the evaluation and computing device 34 has a circuit for measuring and processing the measurement signal.
• FIG. 7 shows an exemplary embodiment of this circuit, which comprises three stages A1, A2, A3, each of which has an operational amplifier OPI, OP2, OP3.
• the first stage A1 works as a buffer with the feedback resistor Rfb.
• the electrical signal V ac (AC voltage) generated by device 33 is present at the + input of OP1.
• the measuring electrode 30 is connected via the coupling capacitor C to the input of OP1.
• the impedance Z sc (short circuit) represents a conductive bridging as a result of liquid or moisture between the measuring electrode 30 and the counter-electrode 31, 32, which in this example is at the reference potential PE, ie protective earth.
• PE ie protective earth
• the current i sc is generally out of phase with the AC voltage V ac .
• this can be used to not only indicate the presence of liquid or moisture in the port detect, but also to draw conclusions about the type of liquid.
• Blood for example, has a characteristic complex resistance that differs from, for example, water.
• This voltage or the transient properties of the voltage are characteristic of moisture occurring in the port, which creates a conductive connection between the measuring electrode and counter-electrode.
• this voltage is rectified and averaged or smoothed, and in stage A3 the measurement voltage is amplified. Rectifier and amplifier circuits belong to the state of the art. The result is a voltage V a dc that can be digitized with an analog-to-digital converter (analog digital converter) that is not shown.
• the evaluation and computing device 34 which can include a controller CPU1 (Fig. 3), for example, is configured in such a way that the measurement signal is evaluated using the computing operations described below in order to detect whether there is liquid or moisture in the empty space and /or what liquid is in the void. For this they can algorithms known to those skilled in the art can be used. If it is concluded that there is liquid or moisture in the empty space 23, the evaluation and computing device generates a control or alarm signal.
• FIGS. 8A to 8D show the time course of the signals.
• the CPU1 generates the signal en_meas so that the first switch 36 (Fig. 3) is closed (Fig. 8A).
• the excitation voltage V ac for example, an AC voltage with a frequency of 20 kHz is generated (Fig. 8B).
• the signals in FIGS. 8C and 8D are each characteristic of the resulting voltage Ana_in, which is evaluated with the CPU2.
• FIG. 8C shows the case in which the port is dry (NO CD detect) and FIG. 8D the case in which moisture has formed a conductive connection between the measuring electrode and the counter-electrode (CD detect).
• the resulting voltage Ana_in is higher, which can be correspondingly detected by a comparison with a reference value VRef.
• the measured voltage is AD-converted and the voltage Ana_in is compared with the reference value VRefin of CPU1 (controller).
• the first switch 36 which is controlled by the en_meas signal, is preferably open in the time intervals in which no excitation voltage V ac should be present at the measuring electrode. This isolates the measuring electrode 30 from the circuit, so that unwanted leakage currents are prevented.
• a Expected value for the voltage Ana_in can be checked. If the measured value deviates from the expected value, there is an error.
• an upper and lower reference value VRen, VRef2 is shown. For example, it can be checked whether the voltage is between the upper and the lower reference value VRen, VRef2Üegt.
• the inner pipe section 22 or the outer pipe section 24 can function as counter-electrode 31 , 32 .
• at least part of the outer pipe section 24 can be designed as a counter electrode 32 for checking the filling level, for example certain areas of the inner wall of the outer pipe section 24 can be provided with a conductive coating 24A, with the measuring electrode separating from the individual areas can form several current paths. Then, depending on the fill level of the empty space with disinfecting liquid, a different resistance sets in, with further current paths forming as the fill level of the empty space increases, so that the resistance decreases, which can be detected by the evaluation and computing device 34 .
• the evaluation and computing device 34 can also be configured in such a way that several measurement signals can be evaluated. Depending on the fill level, voltage or current values result for the individual counter-electrodes, which can be compared with reference values that are characteristic of the respective fill level.
• an essentially rectified signal Ana_in is evaluated, as a result of which the information on the phase shift between the measurement signal and the excitation signal is lost.
• a non-rectified AC voltage/AC signal So not just with one If the excitation frequency is measured but varies (frequency sweep), characteristic curves result, which can be converted into impedance curves (amount of impedance as a function of frequency), for example.
• impedance curves amount of impedance as a function of frequency
• dialysate or substitutes have different characteristic impedance curves and can also differ from one another, for example, in terms of the ion density, ie the density of the free charge carriers.

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• Health & Medical Sciences (AREA)
• Heart & Thoracic Surgery (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• Engineering & Computer Science (AREA)
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• Infusion, Injection, And Reservoir Apparatuses (AREA)

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• 2020
  • 2020-10-07 DE DE102020126224.8A patent/DE102020126224A1/de active Pending
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