Novel air bag tracheal catheter

Abstract

The utility model provides a novel air bag tracheal catheter. The novel air bag tracheal catheter comprises a catheter; the air bag sleeves the area, close to the front end, of the catheter; the inflation tube is connected with the air bag and used for inflating the air bag; the tensile strain sensor assembly is arranged on the outer surface of the air bag; the terminal is electrically connected with the tensile strain sensor assembly, and the terminal is used for acquiring the strain value of the air bag; wherein the change rate of the strain value monitored by the terminal is reduced in response to expansion of the airbag to be attached to the tracheal wall. According to the novel air bag tracheal catheter, interaction force between the air bag and the tracheal wall is measured in real time through the tensile strain sensor, guidance is conducted when the air bag is inflated so that the air bag can be attached to the tracheal wall most ideally, the minimum air leakage amount can be achieved, effective ventilation can be guaranteed, and related complications can be reduced.

Description

Technical Field

[0001] The utility model relates to the field of medical devices, in particular to a novel balloon tracheal catheter. Background Art

[0002] As an artificial airway is a commonly used treatment method clinically, the balloon is one of the important structures of the artificial airway. Injecting an appropriate amount of gas into the balloon can ensure the airtightness of the airway and prevent aspiration. When the balloon pressure is too low, the aggregates accumulated above the balloon will flow into the airway, causing aspiration or VAP. When the balloon pressure is high, it will cause tracheal mucosa ischemia and even tracheoesophageal fistula. Therefore, the monitoring of balloon pressure is very important. The calibrated balloon pressure gauge is the "gold standard" for measuring balloon pressure at present. The pressure recommended by the clinical guidelines is 25 - 30 cmH2O. There are many existing innovations on how to measure and maintain this pressure range. For example, a continuous pressure-measuring tracheal catheter is disclosed in the patent application CN202321744066.2, and a multifunctional tracheal catheter is disclosed in the patent application CN202222486730.X. There are also direct measurements of the pressure directly between the balloon and the airway mucosa. For example, a novel balloon tracheal catheter and its use method are disclosed in the patent application CN202211647015.8. An electrode array is distributed on the balloon, including excitation electrodes and detection electrodes, which are evenly distributed along the axial direction of the balloon. The airtightness between the balloon and the tracheal wall is judged by detecting the resistance between the excitation electrodes and the detection electrodes to guide the inflation pressure of the balloon.

[0003] During the use of the existing tracheal catheters, the following problems exist. When the balloon pressure is 25 - 30 cmH2O, some patients still have air leakage or related complications. That is, simply relying on measuring and maintaining the pressure to ensure the balloon fits the tracheal wall cannot guarantee the airtightness of the airway and is not suitable for all patients. In addition, for the balloon with an electrode array distribution, the process is complex, the parts are delicate, and it is difficult to ensure the fitting degree of the electrode distribution. There is also the problem that the airtightness of the airway cannot be guaranteed. Summary of the Utility Model

[0004] In view of this, the utility model provides a novel balloon tracheal catheter, which can accurately monitor the fitting state between the balloon and the tracheal wall, is simple to operate, can ensure the airtightness of the airway, achieve the minimum air leakage volume, ensure effective ventilation, and reduce related complications.

[0005] According to an inventive concept of one aspect of the utility model, a novel balloon tracheal catheter is provided, including:

[0006] A catheter;

[0007] A balloon, sleeved on the catheter in the area near the front end;

[0008] An inflatable tube, connected to the airbag, for inflating the airbag;

[0009] A tensile strain sensor assembly, disposed on the outer surface of the airbag; and

[0010] A terminal, electrically connected to the tensile strain sensor assembly, the terminal being configured to obtain the strain value of the airbag;

[0011] Wherein, in response to the airbag expanding to fit the tracheal wall, the change rate of the strain value monitored by the terminal decreases.

[0012] According to some embodiments of the present invention, the tensile strain sensor assembly is in a ring-shaped strip form, and the tensile strain sensor assembly is circumferentially attached to the outer surface of the airbag.

[0013] According to some embodiments of the present invention, the tensile strain sensor assembly is disposed in the middle region of the airbag.

[0014] According to some embodiments of the present invention, the tensile strain sensor assembly includes:

[0015] A main tensile strain sensor sleeved on the circumferential side of the middle of the airbag; and

[0016] Two auxiliary tensile strain sensors, centered on the main tensile strain sensor, symmetrically sleeved on the outer surfaces of the two sides of the airbag in the circumferential direction.

[0017] According to some embodiments of the present invention, the tensile strain sensor assembly includes:

[0018] A substrate, supported by a flexible material, the substrate being attached to the outer surface of the airbag;

[0019] A nano-mesh layer, disposed on the substrate, the nano-mesh layer being made of carbon nanotubes or silver nanowires;

[0020] Connection electrodes, disposed on the nano-mesh layer, the connection electrodes being electrically connected to the terminal; and

[0021] An encapsulation layer, disposed on the nano-mesh layer and the connection electrodes, the encapsulation layer being configured to protect the nano-mesh layer and the connection electrodes.

[0022] According to some embodiments of the present invention, the terminal further includes:

[0023] A housing;

[0024] A display screen, disposed on the housing, the display screen being configured to display the strain value of the airbag monitored by the tensile strain sensor assembly.

[0025] According to some embodiments of the present utility model, the terminal further includes:

[0026] An air pump, disposed within the housing, the air pump being connected to the inflation tube.

[0027] According to some embodiments of the present utility model, the terminal further includes:

[0028] An instruction input device, disposed on the housing, the instruction input device being configured to control the opening and closing of the air pump.

[0029] According to some embodiments of the present utility model, the terminal further includes:

[0030] A speaker, disposed on the housing, the speaker being configured to start outputting sound in response to the strain value change rate decreasing to a preset threshold.

[0031] According to some embodiments of the present utility model, the novel balloon tracheal catheter further includes:

[0032] A glottis suction tube, at least partially disposed in contact with the catheter, the front end of the glottis suction tube being close to the root of the side of the balloon away from the front end of the catheter.

[0033] The novel balloon tracheal catheter according to the embodiments of the present utility model utilizes a tensile strain sensor to measure the interaction force between the balloon and the tracheal wall in real time, and provides guidance during balloon inflation to achieve the most ideal fit with the tracheal wall, achieving the minimum air leakage, ensuring effective ventilation, and reducing related complications. Description of the Drawings

[0034] Through the following description of the embodiments of the present utility model with reference to the drawings, the above and other objects, features, and advantages of the present utility model will become clearer. In the drawings:

[0035] Figure 1 A perspective view of the novel balloon tracheal catheter according to the embodiments of the present utility model is schematically shown;

[0036] Figure 2 A cross-sectional view of the catheter part of the novel balloon tracheal catheter according to the embodiments of the present utility model is schematically shown.

[0037] In the above drawings, the meanings of the reference numerals are specifically as follows:

[0038] 1 - Catheter;

[0039] 2 - Balloon;

[0040] 3 - Inflation tube;

[0041] 4 - Tensile strain sensor assembly;

[0042] 41 - Main tensile strain sensor;

[0043] 42 - Auxiliary tensile strain sensor;

[0044] 5 - Terminal;

[0045] 6 - Instruction input device;

[0046] 7 - Speaker;

[0047] 8 - Glottis suction tube;

[0048] 9 - Charging port;

[0049] 10 - First interface;

[0050] 11 - Second interface;

[0051] 12 - Filling strip; and

[0052] 13 - Wire. Detailed implementation mode

[0053] To make the objectives, technical solutions and advantages of the present utility model clearer and more understandable, the following further elaborates on the present utility model in detail with reference to specific embodiments and the attached drawings.

[0054] The terms used herein are only for describing specific embodiments and are not intended to limit the present utility model. The terms "including", "comprising", etc. used herein indicate the presence of the described features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0055] All terms used herein, including technical and scientific terms, have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0056] In the case of using expressions such as "at least one of A, B, and C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, and C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc. In the case of using expressions such as "at least one of A, B, or C, etc.", generally, it should be interpreted according to the meaning commonly understood by those skilled in the art. For example, "a system having at least one of A, B, or C" should include, but not be limited to, a system having only A, only B, only C, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.

[0057] It should also be noted that the directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only references to the directions in the accompanying drawings and are not used to limit the protection scope of the present utility model. Throughout the accompanying drawings, the same elements are represented by the same or similar reference numerals. When it may cause confusion in the understanding of the present utility model, the conventional structures or configurations will be omitted.

[0058] Figure 1 Schematically shows a perspective view of the novel balloon tracheal catheter according to an embodiment of the present utility model; Figure 2 Schematically shows a partial cross-sectional view of the catheter 1 of the novel balloon tracheal catheter according to an embodiment of the present utility model.

[0059] According to the inventive concept of one aspect of the present utility model, a novel balloon tracheal catheter is provided, as Figure 1 and Figure 2 shown, the novel balloon tracheal catheter includes: a catheter 1, a balloon 2, an inflation tube 3, a tensile strain sensor assembly 4, and a terminal 5. The balloon 2 is sleeved on the catheter 1 in the area near the front end. The inflation tube 3 is connected to the balloon 2 and is used to inflate the balloon 2. The tensile strain sensor assembly 4 is disposed on the outer surface of the balloon 2. The terminal 5 is electrically connected to the tensile strain sensor assembly 4, and the terminal 5 is used to obtain the strain value of the balloon 2. Among them, in response to the balloon 2 expanding to fit the tracheal wall, the change rate of the strain value monitored by the terminal 5 decreases.

[0060] In this embodiment, the tensile strain sensor is used to measure the interaction force between the balloon 2 and the tracheal wall in real time, and is used for guidance when inflating the balloon 2 to achieve the most ideal fit with the tracheal wall, achieve the minimum air leakage, ensure effective ventilation, and reduce related complications.

[0061] According to some embodiments of the present utility model, during the use of the tracheal catheter, after the preliminary preparation work (including checking airtightness, lubrication, etc.) is completed, the target laryngoscope is inserted, the glottis is fully exposed, and the catheter 1 is inserted into the epiglottis with the right side of the orifice bevel in cooperation with the guide wire. The catheter 1 is rotated and continued to be inserted into the trachea. After passing through the glottis, the guide wire is withdrawn. The airbag 2 is inflated through the inflatable tube 3 to make the volume of the airbag 2 expand. The values monitored by the tensile strain sensor assembly 4 during this process are monitored through the terminal 5. During this process, the change rate of the strain value generally remains at a relatively high value. When the outer wall of the airbag 2 abuts against the inner wall of the trachea, the change rate of its strain value will have a rapid decrease process. Further, when the airbag 2 just abuts against the inner wall of the trachea, the change rate of the strain value will decrease. When the airbag 2 completely abuts against the inner wall of the trachea to achieve airtightness, the change rate of the strain value will decrease to a preset value. Based on the above principle, it is possible to judge whether the airbag 2 has been fitted by monitoring the change rate of the strain value, so as to accurately disconnect the inflation of the inflatable tube 3, so that a reasonable pressure is maintained between the airbag 2 and the inner wall of the trachea, and the airtightness is ensured to the greatest extent.

[0062] According to some alternative embodiments of the present utility model, the novel balloon tracheal catheter is a tracheostomy cannula 3. During the use of the balloon tracheal catheter, preoperative preparations are first carried out, including patient assessment and notification, item preparation, patient position and anesthesia, marking of anatomical positions, and cleaning and disinfection. The specific surgical operations include the following steps: Incise the skin and puncture, make a transverse incision at the selected puncture point, and the length of the incision should be able to accommodate the size of the tracheostomy cannula (usually 1.5 - 2 cm); Insert the guide wire, pass the guide wire through the puncture needle and send it into a certain depth along the tracheal direction. After confirming that the guide wire can move freely in the trachea, withdraw the puncture needle and the needle cannula, and leave the guide wire in place; Dilate the trachea, insert a dilator or dilating forceps along the guide wire, and gradually dilate the tracheal wall to a size sufficient to accommodate the tracheostomy cannula, taking care to avoid damaging the tracheal wall and the guide wire; Insert the tracheostomy cannula, push the tracheostomy cannula along the guide wire into the trachea until it reaches the predetermined position; Inflate the balloon 2 through the inflation tube 3 so that the volume of the balloon 2 expands, and monitor the value detected by the tensile strain sensor assembly 4 during this process through the terminal 5. During this process, the change rate of the strain value generally remains at a relatively high value. When the outer wall of the balloon 2 abuts against the inner wall of the trachea, the change rate of its strain value will have a rapid decrease process. Further, when the balloon 2 just abuts against the inner wall of the trachea, the change rate of the strain value will decrease. When the balloon 2 completely abuts against the inner wall of the trachea to achieve airtight sealing, the change rate of the strain value will decrease to a preset value. Based on the above principle, it is possible to judge whether the balloon 2 has been fitted by monitoring the change rate of the strain value, so as to accurately disconnect the inflation of the inflation tube 3, so that a reasonable pressure is maintained between the balloon 2 and the inner wall of the trachea, and the airtightness is ensured to the greatest extent; Pull out the stylet and the guide wire to ensure that the tracheostomy cannula is fixed and will not slide or bend; Connect the breathing pipeline, connect the tracheostomy cannula to the breathing pipeline to ensure unobstructed breathing.

[0063] According to some alternative embodiments of the present utility model, a pressure sensor is further included, which is arranged inside the balloon 2. During the inflation process of the balloon 2, the gas pressure inside the balloon is monitored in real time and displayed on the terminal 5.

[0064] According to some embodiments of the present utility model, the tensile strain sensor assembly 4 is in a ring-shaped band shape, and the tensile strain sensor assembly 4 is circumferentially attached to the outer surface of the balloon 2.

[0065] According to some embodiments of the present utility model, the tensile strain sensor assembly 4 is arranged in the middle region of the balloon 2.

[0066] In this embodiment, the balloon 2 is optionally ellipsoidal, and the ring-shaped band-shaped tensile strain sensor is sleeved at the maximum diameter of the ellipsoid, that is, the region where the balloon 2 has the largest deformation, which can more accurately reflect the tensile strain of the balloon 2.

[0067] According to some embodiments of the present utility model, the tensile strain sensor assembly 4 includes a main tensile strain sensor 41 and auxiliary tensile strain sensors 42. The main tensile strain sensor 41 is sleeved on the circumferential side of the middle part of the airbag 2. Two auxiliary tensile strain sensors 42 are symmetrically sleeved on the outer surface 9 of the two side parts of the airbag 2 in the circumferential direction with the main tensile strain sensor 41 as the center.

[0068] In this embodiment, the two auxiliary tensile strain sensors 42 are respectively sleeved at the non-maximum diameter of the ellipsoidal airbag 2, which can ensure that when the body position is not very correct, through multiple parts on the airbag 2, it is still possible to accurately judge whether the airbag 2 has adhered to the inner wall of the trachea. Optionally, it is possible to comprehensively judge whether the airbag 2 has adhered to the inner wall of the trachea and whether airtightness has been achieved by the change rate of the strain values respectively monitored by the two tensile strain sensors.

[0069] According to some embodiments of the present utility model, the tensile strain sensor assembly 4 includes: a substrate, a nano-network layer, connecting electrodes, and a packaging layer. The substrate is supported by a flexible material and is attached to the outer surface of the airbag 2. The nano-network layer is disposed on the substrate and is made of carbon nanotubes or silver nanowires. The connecting electrodes are disposed on the nano-network layer and are electrically connected to the terminal 5. The packaging layer is disposed on the nano-network layer and the connecting electrodes, and the packaging layer is used to protect the nano-network layer and the connecting electrodes.

[0070] According to some embodiments of the present utility model, the substrate is made of a flexible material. For example, it can be polydimethylsiloxane (PDMS) or other elastic materials. The substrate material provides the basic shape and stretchability of the sensor, and also protects the active material layer from the influence of the external environment.

[0071] According to some embodiments of the present utility model, the nano-network layer is an active material layer, which is the core part of the nano tensile strain sensor and is composed of nano materials with excellent mechanical and electrical properties, such as carbon nanotubes, nano metal particle films, carbon nano coils, etc.

[0072] According to some alternative embodiments of the present utility model, the carbon nano coil has a helical structure, and the helical structure enables the nano material to generate a more uniform strain distribution when being stretched, thereby improving the sensitivity and stability of the sensor.

[0073] According to some alternative embodiments of the present utility model, the carbon nanotube network has a network structure, which increases the surface area and stretchability of the active material, enabling the sensor to maintain stable performance within a larger strain range.

[0074] According to some alternative embodiments of the present utility model, the nano-mesh layer is a composite structure. By combining nano-materials with different properties, a composite sensor with more excellent performance can be formed, such as a sensor combining carbon nanotubes and metal nanoparticles.

[0075] According to some embodiments of the present utility model, the encapsulation layer is used to protect the sensor from the external environment. Optionally, it is made of a flexible material to ensure the stretchability and flexibility of the sensor.

[0076] According to some embodiments of the present utility model, the working principle of the nano-strain sensor is mainly based on the characteristics of nano-scale substances, such as quantum effects, surface plasmon resonance, and size effects, etc. When the sensor is stretched or compressed, the internal nano-structure will change, and these changes will cause changes in the electrical, optical, or other physical properties of the sensor. By monitoring these changes, the measurement of tensile or compressive strain can be achieved.

[0077] According to some embodiments of the present utility model, the connection electrodes are arranged on both sides of the active material layer and are used to measure changes in resistance or other physical properties. The electrodes are connected to an external circuit through connection wires to transmit and record data. Optionally, the external circuit is arranged inside the terminal 5.

[0078] According to some embodiments of the present utility model, the terminal 5 further includes a housing and a display screen. The housing is the support carrier of the terminal 5, providing an installation space and protection for the functional components. The display screen is arranged on the housing and is configured to display the strain value of the airbag 2 monitored by the tensile strain sensor assembly 4. Through the display screen, the user can see information such as the current strain value of the airbag 2 and the strain value change rate.

[0079] According to some alternative embodiments of the present utility model, the display screen is a touch screen display.

[0080] According to some embodiments of the present utility model, the terminal 5 further includes an air pump, which is arranged inside the housing and is connected to the inflation tube 3. Optionally, the air pump is a micro electric air pump.

[0081] According to some embodiments of the present utility model, the terminal 5 further includes an instruction input device 6, which is arranged on the housing and is configured to control the opening and closing of the air pump. Optionally, the instruction input device 6 includes function keys.

[0082] According to some embodiments of the present utility model, the terminal 5 further includes a speaker 7, which is arranged on the housing and is configured to start outputting sound in response to the strain value change rate dropping to a preset threshold.

[0083] In this embodiment, when the terminal 5 monitors that the strain value change rate of the airbag 2 reaches the preset threshold, the speaker 7 is triggered to output a warning sound to remind the staff to manually turn off the air pump.

[0084] According to some embodiments of the present invention, the novel airbag tracheal catheter further includes a glottis suction tube 8. The glottis suction tube 8 is at least partially arranged in contact with the catheter 1, and the front end of the glottis suction tube 8 is close to the root of the airbag 2 on the side away from the front end of the catheter 1.

[0085] In this embodiment, the operator can perform sputum suction operations on the target through the glottis suction tube 8 at regular intervals.

[0086] According to some alternative embodiments of the present invention, the terminal 5 further includes a secondary battery. The secondary battery is arranged inside the housing and is electrically connected to the display screen, the command input device 6, the air pump, etc.

[0087] Further alternatively, the terminal 5 further includes a charging port 9. The charging port 9 is arranged on the housing and is electrically connected to the secondary battery.

[0088] According to some embodiments of the present invention, as Figure 2 shown, a strip-shaped groove extending along the axial direction of the catheter 1 is formed by inward depression on the outer side wall of the catheter 1. Filling strips 12 are arranged on two side edges of the groove, and the two strip-shaped grooves are used to clamp the inflation tube 3 in the groove.

[0089] According to some alternative embodiments of the present invention, the inner side surface of the groove is an arc surface, and the groove and the outer side surface of the catheter 1 are arc-transition connected. Three side edges of the filling strip 12 are all arc surfaces, and the radian of the three arc surfaces are respectively arc-transition connected with the catheter 1, the groove, and the inflation tube 3 to reduce the influence of bending on the catheter 1 and the inflation tube 3 during use.

[0090] According to some alternative embodiments of the present invention, the filling strip 12 is provided with a long through hole along the axial direction. Among them, the wire 13 connecting the terminal 5 and the tensile strain sensor assembly 4 is embedded in the long through hole. That is to say, while the filling strip 12 plays a role in limiting and fixing the inflation tube 3, it also plays a role in fixing and protecting the wire 13. Further, the filling strip 12 is made of a flexible magnetic shielding material. Optionally, the filling strip 12 is a nanocomposite material composed of nanoscale conductive fillers (such as carbon nanotubes, graphene, etc.) and a flexible polymer matrix.

[0091] According to some alternative embodiments of the present invention, a first interface 10 is arranged at the end of the catheter 1. The first interface 10 is suitable for being connected to medical devices such as a ventilator, an oxygen source, and a monitoring device.

[0092] According to some alternative embodiments of the present utility model, a second interface 11 is provided at the end of the glottis suction tube 8, and the second interface 11 is adapted to be connected to a suction device (e.g., a sputum aspirator).

[0093] The embodiments of the present utility model have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present utility model. Although the embodiments have been described separately above, this does not mean that the measures in each embodiment cannot be used advantageously in combination. The scope of the present utility model is defined by the appended claims and their equivalents. Without departing from the scope of the present utility model, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should fall within the scope of the present utility model.

Claims

1. A novel balloon tracheal catheter, characterized in that, Comprising: A catheter; An airbag, sleeved on the region near the front end of the catheter; An inflation tube, connected to the airbag and used to inflate the airbag; A tensile strain sensor assembly, arranged on the outer surface of the airbag; And A terminal, electrically connected to the tensile strain sensor assembly, and the terminal is used to obtain the strain value of the airbag; Wherein, in response to the airbag expanding to fit the tracheal wall, the change rate of the strain value monitored by the terminal decreases.

2. The novel balloon tracheal catheter according to claim 1, wherein, The tensile strain sensor assembly is in a circular strip shape and is circumferentially attached to the outer surface of the airbag.

3. The novel balloon tracheal catheter according to claim 2, wherein, The tensile strain sensor assembly is arranged in the middle region of the airbag.

4. The novel balloon tracheal catheter according to claim 2, wherein, The tensile strain sensor assembly includes: A main tensile strain sensor, sleeved on the circumferential side of the middle part of the airbag; and Two auxiliary tensile strain sensors, centered on the main tensile strain sensor, symmetrically sleeved on the outer surfaces of the two sides of the airbag along the circumference.

5. The novel balloon tracheal catheter according to claim 1, characterized in that, The tensile strain sensor assembly includes: A substrate, supported by a flexible material, and the substrate is attached to the outer surface of the airbag; A nano network layer, arranged on the substrate, and the nano network layer is made of carbon nanotubes or silver nanowires; Connection electrodes, arranged on the nano network layer, and the connection electrodes are electrically connected to the terminal; and An encapsulation layer, arranged on the nano network layer and the connection electrodes, and the encapsulation layer is used to protect the nano network layer and the connection electrodes.

6. The novel airbag tracheal catheter according to claim 1, characterized in that, The terminal further includes: A housing; A display screen, arranged on the housing, and the display screen is configured to display the strain value of the airbag monitored by the tensile strain sensor assembly.

7. The novel airbag endotracheal catheter according to claim 6, wherein, The terminal further includes: An air pump, arranged inside the housing, and the air pump is connected to the inflation tube.

8. The novel balloon tracheal catheter according to claim 7, characterized in that, The terminal further includes: An instruction input device, arranged on the housing, and the instruction input device is configured to control the opening and closing of the air pump.

9. The novel balloon tracheal catheter according to claim 6, characterized in that, The terminal further includes: A speaker, arranged on the housing, and the speaker is configured to start outputting sound in response to the change rate of the strain value decreasing to a preset threshold.

10. The novel balloon tracheal catheter according to claim 1, wherein, Further comprising: A glottis suction tube, at least partially arranged in fit with the catheter, and the front end of the glottis suction tube is close to the root of the side of the airbag far from the front end of the catheter.

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