DE102021003506A1 - Insufflation tube for laparoscopy with heating element, humidifier and device for determining moisture content - Google Patents

Abstract

The present invention relates to an insufflator with an insufflation tube with an integrated heating element and humidifying means for laparoscopy, it being possible to measure the moisture content.

Description

The present invention relates to an insufflator with an insufflation tube with an integrated heating element and humidifying means for laparoscopy, it being possible to measure the moisture content.

Background and prior art

Laparoscopy is a medical procedure that allows the abdominal cavity and the organs within it to be visually inspected. For this purpose, small skin incisions (0.3 to 2 centimeters) are usually made in the abdominal wall and a trocar is inserted through this, which in turn can hold an optical device. The abdominal cavity can be viewed using a special endoscope (laparoscope). During diagnostic laparoscopy, the abdominal cavity is only visually inspected, while surgical interventions can also be carried out as part of therapeutic laparoscopy.

Usually, at the beginning of the laparoscopy, the abdomen is inflated with gas to create a pneumoperitoneum. Various gases have already been used for this purpose, e.g. As air, nitrogen or carbon dioxide (CO ₂ ). The use of carbon dioxide gas has proved particularly effective. It was found that it makes sense, particularly in the case of longer laparoscopic interventions, to heat the introduced gas on the one hand and to moisten it on the other. The purpose of the gas heating is not to cool the patient down, as well as to avoid a diffuse feeling of pain in the patient, which is probably a consequence of local cooling due to the entry of cold gas. The humidification serves to prevent the inner abdominal surfaces from drying out in order to avoid the resulting cooling.

Suggestions for this have already been made in the prior art. For example, the German patent describes DE19510710 a device that provides a means for adjusting the gas humidity (e.g. a sponge) and which may optionally include an additional heating element.

the DE 10 2013 000492 A1 describes a tube with an integrated heating element for laparoscopy, which also contains a moisturizing agent. According to this publication, the humectant is moistened with water before an operation. Depending on the water absorption of the material described there, the gas volume flow and the duration of the operation, it may be necessary to re-moisten the moistening agent intraoperatively. Since the rate of evaporation of the water depends on a number of parameters, up to now it can only be estimated when refilling is possible. Alternatively, embodiments are described that arrange a humidity sensor for determining the gas humidity in the gas channel. However, this has several disadvantages. On the one hand, the humidity sensor has to be connected electrically, which makes the design of the filter interface more complicated. Furthermore, the moisture sensor generates a not inconsiderable flow resistance in the gas channel. This leads to a lower flow rate, which contradicts the current flow requirements.

Another device for humidifying gases in medical technology is in the DE 3617031A1 (Priorities: NZ 21263, NZ 215123 and NZ 214694). A hose that is always filled with water is provided as part of a hose system that is difficult to produce. Water vapor is released into the gas via a microporous hose wall. A sensor monitors the water temperature.

Another solution known from the prior art is to use a humidity sensor. Such a solution can be a sensor that measures the temperature profile during heating, as in WO 2017/157 365 A1 described.

Another way to determine the residual moisture without a moisture sensor is in U.S. 8,836,521 "Hydration alert" described: The heating work performed (electrical work) is determined and used to trigger an alarm for the user to refill the humidification medium. There is also a description of using the total amount of insufflated expansion medium to trigger a refill alarm. The disadvantage of the solutions described is the high outlay for sensors and devices in the device, combined with an only indirect determination of the moistening medium present in the moistening mesh.

The present invention is intended to overcome the disadvantages of the solutions known from the prior art.

Solution according to the invention

The invention teaches an embodiment of a heating tube with which the permittivity of the moistening material can be measured. The basic principle of the solution according to the invention is a construction of the heating hose analogous to a condenser.

Capacitors are known as passive components from electrical engineering. In principle, capacitors consist of two electrically conductive conductive surfaces (electrodes) that are separated from one another by an insulating material, the dielectric. Common embodiments of such capacitors contain plate-shaped electrodes (capacitor plates). The electrical properties of the capacitors are determined not only by the area, the volume and the distance between the electrodes from one another, but also in particular by the permittivity of the dielectric located between the plates.

It is also known that a capacitor forms a resistance when an alternating current is applied. This AC resistance is also called impedance and can be described as a complex AC resistance. The impedance can be measured by methods described in the prior art, in particular by measuring the resistance of an applied alternating current. It is relevant for the present invention that the impedance of a capacitor changes as a result of the change in the permittivity ε of the dielectric.

In the present case, the dielectric mainly consists of the moistening material and its water content ("moisture"). Due to the electrical conductivity of water, the electrodes must be electrically insulated from one another. For this purpose, at least one of the electrodes is covered with electrical insulation.

• • angebracht (z. B. angeklebt) sein. Eine Anordnung innerhalb des Schlauches ist bevorzugt. Die Drähte können dabei weitgehend gerade (parallel zur Orientierung des Schlauches) angeordnet sein. Alternativ können sie auch wendelförmig entlang der Schlauchwand angeordnet sein. Entscheidend für die erfindungsgemäße Funktion ist, dass sich das Befeuchtungsmaterial zwischen den Drähten befindet. Die beiden gegenpoligen Drähte, von denen mindestens einer isoliert sein muss, bilden auf diese Weise einen Kondensator, dessen Impedanz (bei konstanter Frequenz) von den Eigenschaften des Dielektrikums abhängt. Bei Änderung des Feuchtigkeitsgrades des Dielektrikums kommt es zu Änderungen der Impedanz, die messbar sind.

For the purpose of the invention, namely the measurement of moisture within an insufflation tube, which in turn contains a heating element and a moistened moistening material, two wires can be arranged as electrodes in the simplest case, forming the capacitor described above. The wires can be arranged within the tube lumen, the wires can in particular be attached to the inner wall of the tube (e.g. glued or welded). A fixation is recommended because otherwise the impedance can change with the possible movement of the heating tube. In further possibilities, the wires can be worked into the hose wall (eg cast) or on the outer wall of the hose

• • be attached (e.g. glued on). An in-tube arrangement is preferred. The wires can be arranged largely straight (parallel to the orientation of the hose). Alternatively, they can also be arranged helically along the hose wall. It is crucial for the function according to the invention that the moistening material is located between the wires. The two wires of opposite polarity, at least one of which must be insulated, thus form a capacitor whose impedance (at constant frequency) depends on the properties of the dielectric. Changing the degree of moisture in the dielectric results in changes in impedance that can be measured.

1 shows schematically the structure of an insufflation tube according to the invention: an empty tube is shown at the top. Two wires are inserted into the tube and fixed to the tube wall (centre). The wires serve as electrodes. The wires (electrodes) are electrically insulated from each other and form a capacitor with each other and the media in between. The connections to the insufflator are shown. In the figure below you can see the moistening agent, which is wrapped with the heating wire. The electrical heating wire connections can also be seen.

The insufflation tube according to the invention is usually connected to the insufflator in the dry state and the insufflator first measures the impedance in the dry state, ie with a dry moistening agent. The humectant is then moistened with the appropriate amount of humectant (e.g. water). The amount of water required for this depends on the amount of moistening agent in the hose. The hose may include a filler neck for water filling. After humidification, the impedance is measured again. In operation, the humectant releases water into the air. The impedance then approaches the level of the dry hose again.

Studies have shown that simple metal (e.g. copper) wires with a diameter of 0.1-1 mm are sufficient to measure the change in the dielectric properties of the moistening agent (see below). 4 shows the measured change in impedance over the course of the insufflation time.

It has been found that production-related fluctuations in the wires (e.g. wire diameter, length) or their laying can lead to minor changes in the impedances. Since the impedance depends on the frequency, such fluctuations can be compensated for by changing the frequency. In a special embodiment of the invention, the impedances are measured by the insufflator in the dry and/or humidified state and adjusted to a previously determined target impedance by changing the frequency of the applied alternating current.

• - Impedanz (bei trockenem Befeuchtungsmaterial) bei einer oder mehreren bestimmten Messfrequenzen
• - Impedanz (bei feuchtem Befeuchtungsmaterial) feucht bei einer oder mehreren bestimmten Messfrequenzen
• - Messfrequenz zum Erzielen einer bestimmten Impedanz bei feuchtem Befeuchtungsmaterial
• - Messfrequenz zum Erzielen einer bestimmten Impedanz bei trockenem Befeuchtungsmaterial

In an alternative embodiment of the invention, the impedances are measured after production in the dry and/or wet state measured and the measured values stored on a data medium. The stored data may include the following data:

• - Impedance (for dry dampening material) at one or more specific measurement frequencies
• - Impedance (for wet dampening material) wet at one or more specific measurement frequencies
• - Measurement frequency to achieve a certain impedance with moist dampening material
• - Measuring frequency to achieve a certain impedance with dry dampening material

It can be stored, for example, on an RFID chip, a magnetic tape or a barcode, with the insufflator having to have a compatible reading unit. In this case, the insufflator would read out the stored data during or after fixing the insufflation tube and use it to set the device.

In another embodiment of the invention, the capacitor-forming wires are formed by the connection cables of a temperature sensor. In this embodiment, a standard temperature sensor (e.g. DS18S20) is located in the hose. In any case, it must be a high-impedance, temperature-dependent resistor at the AC frequency used for measurement, so that the capacitor is not short-circuited. A basic circuit diagram is in 2 shown.
In this embodiment of the invention, the temperature and moisture content cannot be measured simultaneously; these properties are measured one after the other, in particular in constant alternation. By applying a direct current to the two connection cables, the resistance of the temperature sensor can be measured, from which the temperature can then be determined. By applying a high-frequency alternating current, the impedance of the capacitor formed can be determined, which is related to the moisture content of the dampening material.

The advantage of this embodiment is that the number of wires in the hose is limited. In this embodiment too, the connection wires for the temperature sensor can be arranged outside or inside the tube or in the tube wall.

In a further alternative embodiment of the invention, one of the capacitor-forming wires can also be formed by a heating wire ( 3 ). Insufflation tubes with heating wires are, for example, in WO 2014/111083 A1 been described. In this embodiment, too, only a temporally alternating heating or measurement is possible: by applying a direct current to the heating wire, this develops heat through the ohmic resistance, which heats the gas passed through and the humidifying agent. By applying a high-frequency AC voltage to the heating wire on the one hand and a wire arranged in parallel on the other hand, the impedance of the capacitor formed thereby can be determined and from this the moisture content of the moistening material can be determined.

In a preferred embodiment of the invention, the inflow of gas into the insufflation tube takes place through a moistening means which is designed as a braided tube and which in turn is positioned inside the insufflation tube. Like in the WO 2014/111083 A1 described, the braided hose can also be sheathed with the moistening material and the heating wire. In any case, the gas flowing through the braided hose exits through the pores of the outer surface and is both heated and moistened in the process. In an embodiment of the invention with a metallic braided hose, the enlargement of the capacitor area can improve the quality of the measurement. influence.

If the filament is a material whose resistance increases with temperature (e.g. a material with a positive or negative temperature coefficient (PTC or NTC) as in WO 2014/111084 A1 described), then the temperature can also be measured by measuring the resistance of the heating wire. The details of such a temperature measurement are given in WO 2014/111084 A1 described so that reference can be made to it. In such an embodiment of the invention, heating periods, measurement periods for moisture measurement of the dampening material and temperature measurement alternate periodically. The use of digital measuring sensors in such a structure is less advisable, since the supply lines for digital temperature sensors as a bus system are susceptible to interference from the radiation of HF signals.

The measurement of the humidity of the moistening agent according to the invention is carried out in a manner which is known in principle, namely by measuring the impedance using an applied alternating current of the highest possible frequency (eg 100 kHz to 100 MHz). Since the impedance depends on the precise design of the device according to the invention (among other things, the distance between the capacitor-forming wires, the type of moistening material, the composition of the moistening agent, the geometric arrangement of the wires, etc.), to carry out an impedance measurement of such a hose. For this purpose, the tube structure shown below is initially realized without a moistening agent (water) and the impedance of the capacitor formed is measured using conventional methods. Then the dampening material is maximally dampened by adding the dampening agent (water). Using a dummy, the tube is then heated and gas is passed through it. Meanwhile, the impedance is measured continuously or periodically and the course of the impedance is recorded. Due to the possible different designs of such insufflation tubes according to the invention, the absolute value of the impedance is comparatively unimportant. The course of the impedance in correlation with the degree of moistening of the moistening material is decisive.

4 shows an example of the measurement cycle and the results: The hose used as an example is first measured in dry form and shows an impedance of 100 ohms. By moistening with 10 ml of water, the impedance drops to 10 ohms. By passing through gas (here: CO ₂ ) with simultaneous heating to 39°C, the water evaporates over time, or in the course of the gas flow (here: constant gas flow of 10 l/min. After passing through 200l, the water almost completely used up, the moistening material is dry again, so that the original impedance of 100 ohms is measured (approximately) again. It turns out that the measured absolute values differ when an isotonic saline solution is used instead of (distilled) water. The course However, the measurement curve is similar, so that a moisture measurement is also possible in this case.

The object of the present invention is primarily to determine the condition of the moistening agent in relation to its water content, i.e. the water content of the moistening agent, without implementing the disadvantages mentioned at the outset. The primary objective is to generate a refill alarm/signal, i. H. a signal that tells the user when a refill of water is needed.

For example, an alarm signal can be triggered if the water content of the dampening material falls below a preset threshold. The alarm signal can be triggered, for example, when a preset threshold value corresponds to 50%, 40%, 30%, 20%, 10% or 5% of the maximum humidity.

In the context of the present invention, the terms "water content of the humectant" and "moisture of the humectant" are considered synonymous.

character list

• 1 shows schematically the structure of an insufflation tube according to the invention: an empty tube is shown at the top. Two wires are inserted into the tube and fixed to the tube wall (centre). The wires, which are electrically isolated from one another, act as a capacitor whose impedance depends on the media in between. The connections to the insufflator are shown. In the figure below you can see the moistening agent, which is wrapped with the heating wire. The electrical heating wire connections can also be seen.
• 2 Figure 1 shows an embodiment of the invention in which the capacitor-forming wires are formed by the lead wires of a temperature sensor.
• 3 Figure 12 shows an alternative embodiment of the invention in which one of the capacitor-forming wires is formed by a heating wire. In an optional variant, the temperature can also be measured through the heating wire (analogous to WO 2014/111083 A1 ).
• 4 shows an example of the measurement cycle and the results: The hose used as an example is first measured in dry form and shows an impedance of 100 ohms. At time t=0 s it is moistened with 10 ml water (distilled), the impedance falls to 10 ohms. By passing through gas (here: CO ₂ ) with simultaneous heating to 39°C, the water evaporates over time or in the course of the gas flow (here: constant gas flow of 10 l/min). After passing through 200l, the water is almost completely used up, the moistening material is dry again, so that the original impedance of 100 ohms is measured again (approximately). It turns out that the absolute values measured differ when an isotonic saline solution is used instead of (distilled) water (dashed line). However, the course of the measurement curve is similar, so that a moisture measurement is also possible in this case.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 19510710 [0004]
• DE 102013000492 A1 [0005]
• DE 3617031 A1 [0006]
• WO 2017157365 A1 [0007]
• US8836521 [0008]
• WO 2014111083 A1 [0023, 0024, 0030]
• WO 2014111084 A1 [0025]

Claims (13)

Insufflation device for use in medical technology, containing an insufflator for gas supply and an insufflation tube, the interior of the insufflation tube containing a moistening material, the moistening material being in contact with a heating element, the heating element consisting of a wire which can be activated by applying a current, characterized in that the insufflation tube further comprises two mutually insulated wires which together form a capacitor whose impedance depends on the humidity of the wetting material. Device according to claim 1 wherein at least one of the wires electrically insulated from one another is arranged on the outer wall of the insufflation tube, inside the wall of the insufflation tube, on the inner wall of the insufflation tube or inside the insufflation tube. Device according to claim 1 , wherein the insufflation tube further includes a temperature sensor. Device according to claim 2 , wherein the temperature sensor is arranged at the patient-side end of the insufflation tube. Device according to claim 3 and 4 , wherein at least one of the capacitor-forming wires is formed by a connection cable of the temperature sensor. Device according to claim 1 , wherein at least one of the capacitor-forming wires is formed by a heating wire. Device according to claim 1 , wherein at least one of the capacitor-forming wires is formed by a metallic braided hose. Method for measuring the water content of a humidifying agent which is located in an insufflation tube of an insufflator through which a gas flows, characterized in that a) a high-frequency voltage is applied to the two wires which form a capacitor b) the impedance of the capacitor is determined, c) the humidity of the moistening material is determined from the impedance. Method for measuring the water content of a humidifying agent which is located in an insufflation tube of an insufflator through which a gas flows according to claim 8 , characterized in that a) a high-frequency voltage is applied to the two wires forming a capacitor b) the impedance of the capacitor is determined with dry humectant, c) the humectant is moistened, d) the impedance of the capacitor with wet humectant is determined, e) the insufflation tube is used as intended by passing a gas through it, f) the moisture content of the humidifying material is determined from the change in impedance during insufflation. procedure according to claim 8 or 9 , characterized in that an alarm signal is triggered when the moisture content of the dampening material falls below a preset threshold value. procedure according to claim 10 , characterized in that the preset threshold corresponds to 50%, 40%, 30%, 20%, 10% or 5% of the maximum humidity. procedure according to claim 8 or 9 , characterized in that the impedance of the capacitor is measured before the intended use with dry and/or moistening agent by the insufflator by applying a high-frequency voltage and by changing the frequency a predetermined target impedance with dry and/or moistening agent is set, the frequency at which the target impedance is reached is used for the intended insufflation under gas humidification. procedure according to claim 8 or 9 , characterized in that the impedance of the capacitor is measured after production with dry and/or moistening agent by applying a high-frequency voltage and by changing the frequency a predetermined target impedance is set with dry and/or moistening agent, the frequency at which the target impedance is achieved is stored on a data medium, the data medium being read out by the insufflator and the stored data being used for the intended insufflation with gas humidification.

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