A laparoscopic air insufflation tube equipped with a heating element, humidifying material, and a device for determining water content.

Abstract

The present invention relates to an air insufflation device for laparoscopy, which comprises an air insufflation tube with integrated heating element and humidifying material, whereby the measurement of the moisture content is possible. To measure the moisture content of the humidifying material, a separate moisture sensor is not required. Components that are already part of the air insufflation tube can be used, in particular the connecting wires of the heating element or the temperature sensor.

Description

Technical Field

[0001] The present invention relates to a gas delivery device for laparoscopy, having an integrated heating element and a humidifying material in the gas delivery tube, thereby enabling measurement of the water content.

Background Art

[0002] Laparoscopy is a medical procedure that enables visual inspection of the abdominal cavity and the inside of organs. Generally, a small skin incision (0.3 - 2 centimeters) is made in the abdominal wall, through which a trocar is introduced, and then it can accommodate an optical device. A special endoscope (laparoscope) is used to observe the abdominal cavity. In diagnostic laparoscopy, the abdominal cavity is only visually inspected, and in therapeutic laparoscopy, surgical procedures can also be performed.

[0003] Generally, laparoscopy starts by filling the abdominal cavity with gas to create pneumoperitoneum. Various gases are used, including air, nitrogen, and carbon dioxide (CO2). The use of carbon dioxide gas has particularly yielded good results. It has been found useful to heat and humidify the introduced gas, especially during particularly long laparoscopic procedures. Gas heating is used to prevent the patient from getting cold and to avoid the perception of diffuse pain in the patient, which is probably a result of local cooling due to the entry of cold gas. Humidification is used to prevent the inner surface of the abdomen from drying and cooling.

[0004] Proposals for this have already been made in the prior art. For example, German Patent Application Publication No. 19510710, a German patent, discloses a device including means for adjusting the humidity of the gas (e.g., a sponge), which may optionally include an additional heating element.

[0005] German Patent Application Publication No. 102013000492 describes a tube with an integrated heating element for laparoscopy, which also includes a humidifying material. According to this document, the humidifying material is humidified with water before surgery. Depending on the water absorption rate of the material described therein, the gas flow rate, and the duration of the surgery, re-humidification of the humidifying material may be required during surgery. Since the rate of water evaporation depends on several parameters, it is only possible to estimate when replenishment is possible. As an alternative, a design is described that uses a humidifying sensor to determine the gas humidity in the gas channel. However, this has several disadvantages. First, the humidity sensor must be electrically connected, which complicates the design of the filter interface. In addition, the humidity sensor creates significant flow resistance in the gas channel. This results in a low flow rate, which goes against the current flow requirements.

[0006] Another device for humidifying gas in medical technology is described in German Patent Application Publication No. 3617031 (priority: New Zealand Patent No. 21263, New Zealand Patent No. 215123, and New Zealand Patent No. 214694). Regarding the tube system, it must be manufactured in a complex manner, and the tubes are always supplied filled with water. Water vapor is released as gas through the microtube walls. A sensor monitors the water temperature.

[0007] Another known solution in the prior art is to use a humidity sensor. One such solution is a sensor that measures the temperature curve during heating, as described in International Publication No. 2017 / 157365.

[0008] Another method for determining residual humidity without using a humidity sensor is described in U.S. Patent No. 8,836,521, entitled "Hydration Alarm." The heat treatment (electrical treatment) to be performed is determined and used to alert the user to replenish the humidifying medium. It also describes how to use the total amount of air-filled expansion medium to trigger a refill alarm. The disadvantages of this described solution are that it only indirectly determines the amount of humidifying medium present in the humidifying string, as well as the high cost of sensors and equipment in the device.

[0009] European Patent Application Publication No. 2388041 describes a device for introducing a drug into the body during air delivery. The described device may include a humidity sensor. It is also based on volume measurement.

[0010] U.S. Patent No. 5,483,414 describes an impedance sensor for measuring physical parameters, particularly temperature. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] German Patent Application Publication No. 19510710 [Patent Document 2] German Patent Application Publication No. 102013000492 Specification [Patent Document 3] German Patent Application Publication No. 3617031 [Patent Document 4] International Publication No. 2017 / 157365 [Patent Document 5] U.S. Patent No. 8836521 [Patent Document 6] European Patent Application Publication No. 2388041 [Patent Document 7] U.S. Patent No. 5483414 [Overview of the project] [Problems that the invention aims to solve]

[0012] The present invention aims to overcome the disadvantages of prior art known solutions and to provide an air supply device that can measure the humidity of a humidifying material without additional sensors. [Means for solving the problem]

[0013] This invention teaches embodiments of a heating tube capable of measuring the dielectric constant of a material being humidified. The basic principle of the solution according to the present invention is to construct a heating tube similar to a capacitor.

[0014] In electrical engineering, capacitors are known as passive components. In principle, a capacitor consists of two conductive surfaces (electrodes) separated from each other by a dielectric insulating material. Plate-shaped electrodes (capacitor plates) are a common design for such capacitors. The electrical properties of a capacitor are determined not only by its surface area, volume, and the distance between the electrodes, but also by the dielectric constant of the dielectric material between the plates.

[0015] It is also well known that when alternating current is applied, a capacitor can form a resistance. This AC resistance is also called impedance and can be expressed as composite AC resistance. Impedance can be measured by the methods described in the prior art, in particular by measuring the resistance of the applied alternating current.

[0016] An explanation of the capacitor as a "composite resistor" is necessary because the resistance calculated by formula (I) (I)R=U / I This is because it is time-dependent. The necessary calculation method is described in detail in electrical engineering textbooks.

[0017] The fact that the impedance or composite resistance of a capacitor changes by changing the dielectric constant ε of the dielectric material is relevant to the present invention.

[0018] In this case, the dielectric mainly consists of a humidifying material and its moisture content (the "water content"). Due to the conductivity of water, the electrodes must be electrically insulated from each other. For this purpose, at least one of the electrodes is coated with an electrical insulator.

[0019] For the application purpose according to the present invention, that is, to measure the humidity inside the air supply pipe including the heating element and the moisture humidifying material, in the simplest case, two wires can be arranged as the electrodes forming the capacitor as described above. These wires can be arranged inside the lumen of the pipe, and in particular, the wires can be fixed to the inner wall of the pipe (for example, by adhesion or welding). Fixing is recommended. This is because if not fixed, the impedance can change with the possible movement of the heating pipe. As another possibility, these wires can be integrated into the pipe wall (for example, by molding), or the wires can be attached to the outer wall of the pipe (for example, by adhesion). Arrangement inside the pipe is preferred. The wires can mainly be arranged in a straight line (parallel to the direction of the pipe). Alternatively, the wires can be arranged spirally along the pipe wall. For the function of the present invention, it is important that the humidifying material is located between the wires. Thus, two wires of opposite poles must insulate at least one of them, but form a capacitor, and its impedance (at a certain frequency) depends on the characteristics of the dielectric. When the water content of the dielectric is changed, the impedance changes, which can be measured.

Brief Description of the Drawings

[0020] [Figure 1] It is a schematic diagram showing the structure of the air supply pipe according to the present invention. An empty pipe is shown in the upper figure. Two wires are inserted into the pipe and attached to the pipe wall (the middle figure). The wires electrically insulated from each other act as a capacitor, and its impedance depends on the medium between them. The connection to the air supply device is shown. A humidifying material with a heating wire wound around it is shown in the lower figure. The electrical connection for heating is also shown. [Figure 2]FIG. 0 is a diagram showing an embodiment of the present invention in which a wire forming a capacitor is formed by a connection cable of a temperature sensor. [Figure 3] FIG. 3 is a diagram showing an alternative embodiment of the present invention in which one of the wires forming the capacitor is formed by a heating wire. In an optional variation, the temperature can also be measured by the heating wire (similar to WO 2014 / 111083). [Figure 4] FIG. 6 is a graph showing an example and results of a measurement cycle. The sample tube was first measured in a dry state and showed an impedance of 100 ohms. At t = 0, it was humidified with 10 milliliters of distilled water and the impedance dropped to 10 ohms. By passing a gas (here CO) through the sample and heating the sample to 39° C, the water evaporates over time or with a gas flow (here a constant gas flow of 10 liters / min). After 200 liters had flowed out, the water was almost completely used up, the humidifying material dried out again, and the initial impedance of 100 ohms was (approximately) measured again. It can be confirmed that when isotonic saline (dashed line) was used instead of (distilled) water, the absolute values measured were different. However, the shape of the measurement curve was similar, so humidity measurement is also possible in this case.

BEST MODE FOR CARRYING OUT THE INVENTION

[0021] FIG. 1 schematically shows the structure of an air supply pipe according to the present invention. An empty pipe is shown in the upper figure. Two wires are inserted into the pipe and attached to the pipe wall (middle figure). The wires act as electrodes. The wires (electrodes) are electrically insulated from each other and together with the medium between them form a capacitor. The connection to the air supply device is shown. A humidifying material with a heating wire wound around it is shown in the lower figure. The electrical connection for the heating wire is also shown.

[0022] The air supply tube according to the present invention is generally connected to an air supply device in a dry state, and the air supply device first measures the impedance in a dry state, i.e., using a dry humidifying material. The humidifying material is then humidified with an appropriate amount of humidifying material (e.g., water). The amount of water required depends on the amount of humidifying material in the tube. This tube may have a water filling port. After humidification, the impedance is measured again. During surgery, the humidifying material releases water into the air. The impedance then returns to the level of the dry tube.

[0023] The study shows that simple metal (e.g., copper) wires with a diameter of 0.1–1 mm are sufficient to measure changes in the dielectric properties of the humidified material (see below). Figure 4 schematically shows the measured change in impedance as a function of air supply time.

[0024] It has been found that variations associated with wire production (e.g., wire diameter, length) or their routing can result in small changes in impedance. Since impedance is frequency-dependent, such variations may be offset by frequency changes. In certain embodiments of the present invention, impedance is measured by an air supply device in dry and / or wet conditions and adjusted to a predetermined nominal impedance by varying the frequency of the applied AC current.

[0025] In an alternative embodiment of the present invention, impedance is measured in a dry and / or wet state after manufacturing, and the measured values ​​are stored in a data carrier. The stored data may include: - Impedance (using dry, humidified material) at one or more measurement frequencies; - Impedance (using a moist, humidified material) at one or more measurement frequencies; -Measurement frequency for achieving a given impedance using a moist humidifying material; - The measurement frequency for achieving a given impedance using a dry, humidified material.

[0026] The data can be stored, for example, on an RFID chip, magnetic tape, or barcode, and the insulator must have a compatible reader. In this case, the insulator reads the stored data during or after the insulator is fitted and uses it to adjust the device.

[0027] In another embodiment of the present invention, the wires forming the capacitor are formed by the connecting cable of a temperature sensor. In this embodiment, a common temperature sensor (e.g., DS18S20) is installed inside the tube. In either case, the capacitor must be a temperature-dependent resistor with high impedance at the AC frequency used for measurement, so as not to short-circuit. A basic circuit diagram is shown in Figure 2. In this embodiment of the present invention, temperature and moisture content cannot be measured simultaneously. These characteristics are measured sequentially, and in particular, alternately and consecutively. By applying DC to the two connecting cables, the resistance of the temperature sensor can be measured, from which the temperature can be determined. By providing a high-frequency AC current, it is possible to measure the impedance of the formed capacitor, which is related to the humidity of the humidifying material.

[0028] An advantage of this embodiment is that it does not require an additional humidity sensor. At the same time, the number of wires inside the tube is limited. Furthermore, in this embodiment, lead wires for the temperature sensor can be installed on the outside or inside of the tube, or inside the tube wall.

[0029] In another alternative embodiment of the present invention, one of the wires forming the capacitor may also be a heating wire (Figure 3). A supply tube with a heating wire is described, for example, in International Publication No. 2014 / 111083. In this embodiment, again, only temporary alternating heating or measurement is possible. By applying a DC current to the heating wire, heat is generated through the ohm resistance, which heats the passing gas and humidifying material. Furthermore, the advantages already described above are realized without the need to introduce additional components into the tube, and thus measurements can be performed using the components already present. By applying a high-frequency AC voltage to the heating wire on one side and to the parallel wire on the other side, the impedance of the resulting capacitor can be determined, and from this, the humidity of the humidifying material can be determined.

[0030] In a preferred embodiment of the present invention, the gas flow into the supply tube is formed as a braided tube and then passes through a humidifying material positioned within the supply tube. As described in International Publication No. 2014 / 111083, the braided tube may also be wound with a humidifying material and a heating wire. In either case, the gas flowing through the braided tube exits through holes in the sheath surface and is heated and humidified. In one embodiment of the present invention, the use of a metal braided tube may advantageously affect the quality of the measurement by increasing the capacitor area.

[0031] If the heating wire is made of a material whose resistance increases with temperature (a material with a positive or negative temperature coefficient (PTC or NTC), as described in International Publication No. 2014 / 111084), the temperature can also be measured by measuring the resistance of the heating wire. Details of such temperature measurement are described in International Publication No. 2014 / 111084, which can be referenced. In such embodiments of the present invention, the heating period and the measurement period for humidity and temperature measurement of the humidified material are performed periodically and alternately. The use of digital measuring sensors in such arrangements is not highly recommended because the supply lines of digital temperature sensors, as part of a bus system, are susceptible to interference due to RF signal radiation.

[0032] The humidity of the humidifying material according to the present invention is measured by a known method, i.e., by measuring the impedance with an alternating current at the maximum possible applicable frequency (e.g., 100 kHz to 100 MHz). Since the impedance depends on the precise structure of the device according to the present invention (in particular the distance between wires forming the capacitor, the type of humidifying material, the composition of the humidifying material, the geometric arrangement of wires, etc.), the impedance measurement must be performed for each structure of such a tube. For this purpose, the tube structure shown below is first realized without the humidifying material (water), and the impedance of the formed capacitor is measured by the usual method. Next, the humidifying material (water) is added, and the humidifying material is humidified to its maximum extent. Next, a dummy is used to heat the tube, allowing the gas to flow through. During this process, the impedance is measured continuously or periodically, and the impedance curve is recorded. Due to the various possible designs of such air supply tubes according to the present invention, the absolute value of the impedance is not particularly important. What is important is the course of the impedance related to the degree of humidification of the humidifying material.

[0033] Figure 4 shows an example of a measurement cycle and results. The sample tube is initially measured dry and shows an impedance of 100 ohms. By humidifying with 10 ml of water, the impedance drops to 10 ohms. By passing a gas (here, CO2) through the sample and heating the sample to 39°C, the water evaporates over time or with a gas flow (here, a constant gas flow of 10 liters / minute). After 200 liters have flowed through, virtually all the water is used up, the humidifying material dries again, and the initial impedance of 100 ohms is (approximately) measured again. It can be seen that the measured absolute value is different when isotonic saline is used instead of (distilled) water. However, the shape of the measurement curve is similar, and therefore humidity measurement is possible in this case as well.

[0034] The main objective of this invention is to determine the state of the humidifying material in relation to its moisture content, i.e., the state of the moisture content of the humidifying material, without suffering the disadvantages mentioned earlier. The main objective is to generate a replenishment alarm / signal, i.e., a signal that informs the user when water replenishment is needed.

[0035] For example, an alarm signal can be triggered when the moisture content of the humidifying material falls below a preset threshold. For example, an alarm signal can be triggered when the preset threshold is 50%, 40%, 30%, 20%, 10%, or 5% of the maximum humidity.

[0036] In relation to the present invention, the terms "moisture content of the humidifying material" and "humidity of the humidifying material" shall be considered synonymous.

Claims

1. An air supply device for use in medical technology, comprising an air supply device and an air supply tube for gas supply, wherein the air supply tube contains a humidifying material inside, the humidifying material is in contact with a heating element, and the heating element is composed of a wire that can be activated by applying an electric current. The air supply device is characterized in that the air supply tube further includes two wires insulated from each other inside, which come into contact with the humidifying material to form a capacitor, the impedance of which depends on the humidity of the humidifying material, the impedance is determined by measuring the alternating current flowing through the wires, and the humidity of the humidifying material is determined from the determined impedance based on the impedance obtained in the dry state and the humidified state of the humidifying material, respectively.

2. The device according to claim 1, wherein at least one of the electrically insulated wires is disposed on the outer wall of the air supply tube, inside the wall of the air supply tube, on the inner wall of the air supply tube, or inside the air supply tube.

3. The device according to claim 1, wherein the air supply tube further comprises a temperature sensor.

4. The device according to claim 3, wherein the end of the air supply tube is positioned on the patient side.

5. The device according to claim 3 or 4, wherein at least one of the wires forming the capacitor is formed by the connection cable of the temperature sensor.

6. The device according to claim 1, wherein at least one of the wires forming the capacitor is formed by a heated wire.

7. The device according to claim 1, wherein at least one of the wires forming the capacitor is formed by a metal braided tube.

8. A method for operating a device for measuring the moisture content of a humidifying material, located in the air supply pipe of an air supply device through which gas flows, wherein the air supply device is a) A step of applying a high-frequency voltage to two electrically insulated wires that are incorporated inside the air supply tube and come into contact with the humidifying material to form a capacitor, b) A step of determining the impedance of the capacitor by measuring the alternating current flowing through the wire, c) An operating method characterized by including the step of determining the humidity of the humidifying material from the impedance determined in step b) based on the impedance obtained in the dry state and the humidified state of the humidifying material, respectively.

9. The air supply device is d) During the operation of step b), the step of continuously or periodically measuring the impedance of the capacitor, e) During the operation of step c), a step of detecting the humidity of the humidifying material based on the temporal change of the impedance measured in step d), f) A step of controlling or displaying the humidity of the humidifying material based on the detected change in impedance, The operating method according to claim 8, characterized by including the following:

10. The operating method according to claim 8 or 9, characterized in that an alarm signal is issued when the humidity of the humidifying material falls below a preset threshold.

11. The operating method according to claim 10, characterized in that the preset threshold corresponds to 50%, 40%, 30%, 20%, 10%, or 5% of the maximum humidity of the humidifying material.

12. The operating method according to claim 8 or 9, characterized in that the impedance of the capacitor is measured by applying a high-frequency voltage to dry and / or wet humidifying material using the air supply device before use, and a predetermined nominal impedance of the dry and / or wet humidifying material is set by changing the frequency, and the frequency at which the nominal impedance is reached is used for intended air supply accompanied by gas humidification.

13. The operating method according to claim 8 or 9, characterized in that the impedance of the manufactured capacitor, with dry and / or wet humidifying material, is measured by applying a high-frequency voltage, and a predetermined nominal impedance is set using the dry and / or wet humidifying material by varying the frequency, the frequency at which the nominal impedance is reached is stored in a data carrier, the data carrier is read by the air supply device, and the stored frequency at which the nominal impedance is reached is used for intended air supply with gas humidification.

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