An epidural catheter differential compensation fixation device

Abstract

The application discloses an epidural catheter differential compensation fixing device, and belongs to the technical field of medical devices. The device comprises a flexible adhesive base, a first skin reference element, a second skin reference element, a first transmission element, a second transmission element, a dynamic reference element, a differential average component, a catheter marker element and a catheter follower element. In the application, the first skin reference element and the second skin reference element can independently slide and are not constrained by the deformation of the base. The displacement of the two elements is coupled with the rack and the average gear, so that the longitudinal displacement of the dynamic reference element is equal to the average value of the displacement on both sides. When the whole skin translates and the position of the catheter relative to the skin is unchanged, the relative displacement between the dynamic reference element and the catheter follower element is unchanged, so that the common mode displacement is compensated. When the displacement of the skin on both sides is inconsistent, the average gear rotates to adapt to the difference, the dynamic reference element outputs the average component, and the local asymmetric deformation interference is reduced. Only when the catheter has an axial displacement relative to the skin, the relative displacement between the follower element and the dynamic reference element is generated, so that the displacement of the catheter is accurately represented.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to an epidural catheter differential compensation fixation device. Background Technology

[0002] Epidural anesthesia and continuous epidural analgesia typically require inserting a flexible catheter into the epidural space via a puncture needle, with the external segment fixed to the patient's lower back. During labor analgesia, the mother may repeatedly lie on her side, sit up, flex, turn over, or move around the bedside, causing translational, stretching, and shearing deformation of the skin and soft tissues of the lower back. If the fixation device excessively restricts the skin, external traction can easily be transmitted along the catheter to the puncture area; if the fixation device moves with the skin, simply observing the catheter markings or the position of the fixation patch makes it difficult to determine whether the catheter has actually moved outward or inward relative to the puncture site.

[0003] Currently, there are various epidural catheter fixation devices available in clinical practice, mainly including ordinary medical dressing fixation, fixation dressings with reserved buffer structures, and fixation devices with displacement indication or sensing functions.

[0004] However, a common feature of the existing solutions mentioned above is that their displacement reference points are all fixed at a single location on the dressing or substrate. When patient movement causes displacement of the skin on the lower back, this single reference point presents the following problems: First, when the skin shifts as a whole, the reference reference moves synchronously with the skin. When the mother turns over or changes position, the skin on her lower back may shift towards the head or tail. In this case, the reference reference fixed to the dressing moves with the skin, but the relative position between the catheter and the skin does not actually change. However, the displacement readings observed by medical staff show that the catheter has shifted relative to the reference reference, creating a false positive signal that "the catheter's movement with the skin is misinterpreted as catheter slippage."

[0005] Second, when the skin undergoes localized asymmetrical stretching and contraction, the reference reference point shifts uncontrollably. When the mother arches her back or bends to the side, the skin on both sides of the puncture point may experience asymmetrical stretching or contraction (one side of the skin moves towards the head, and the other side moves towards the tail). In this situation, the single reference reference fixed to the dressing is subjected to the combined traction of the deformation of both sides of the skin, and its final position depends on the complex coupling result of the overall deformation of the dressing, rather than the actual displacement of the skin on one side. The displacement reading of the catheter relative to such an uncontrollable reference reference cannot reflect the actual positional change of the catheter, nor can it be attributed to a definite displacement of the skin on one side; its physical meaning is unclear.

[0006] In summary, existing technologies, due to the fixed reference point at a single application location, generate false positive signals when the skin is shifted as a whole and invalid signals with unclear physical meaning when the skin undergoes asymmetrical stretching and contraction locally, resulting in insufficient accuracy and reliability of catheter displacement monitoring. Summary of the Invention

[0007] The purpose of this invention is to provide an epidural catheter differential compensation and fixation device to solve the problems in the prior art where the reference benchmark is fixed at a single dressing position, resulting in false positive signals when the skin is translated as a whole and invalid signals with unclear physical meaning when the skin is stretched and contracted asymmetrically in a local area, thus leading to insufficient accuracy and reliability of catheter displacement monitoring.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention discloses a differential compensation and fixation device for an epidural catheter, comprising a flexible adhesive substrate for attaching to the patient's skin surface. A first skin reference element and a second skin reference element are respectively disposed on both longitudinal sides of the flexible adhesive substrate. The first and second skin reference elements are respectively disposed on both sides of the puncture site along the epidural catheter displacement monitoring direction and are used to fix them to the local skin on both sides of the puncture site to respectively acquire the longitudinal displacement of the local skin on both sides of the puncture site. A first transmission element and a second transmission element are respectively disposed on the first and second skin reference elements. A dynamic reference element is slidably disposed on the flexible adhesive substrate along the longitudinal direction. A differential averaging component is provided on the reference component. The first transmission component and the second transmission component cooperate with the differential averaging component, so that the dynamic reference component forms a dynamic skin reference position based on the average components of the longitudinal displacement of the first skin reference component and the second skin reference component. A catheter marker is detachably provided on the epidural catheter. A catheter follower is slidably provided on the flexible adhesive substrate along the longitudinal direction. The catheter follower is connected to the catheter marker. The epidural catheter drives the catheter follower to move along the longitudinal direction. The longitudinal relative displacement of the catheter follower with respect to the dynamic reference component is used to characterize the axial displacement of the epidural catheter with respect to the local skin reference position.

[0009] Furthermore, the flexible adhesive substrate has longitudinally extending grooves. The lower parts of the first skin reference member and the second skin reference member are respectively provided with a first connecting part and a second connecting part. The first connecting part and the second connecting part pass through the grooves at corresponding positions. The bottom of the first connecting part and the second connecting part are respectively provided with independent skin adhesion areas. The flexible adhesive substrate is provided with a deformation isolation structure in the area corresponding to the grooves to reduce the restriction of the movement of the connecting parts by the overall deformation of the flexible adhesive substrate, so that the first connecting part and the second connecting part can slide longitudinally relative to the flexible adhesive substrate with the corresponding local skin.

[0010] Furthermore, the differential averaging component is a rotating body, and the first transmission component and the second transmission component are respectively disposed on opposite sides of the rotating body and cooperate with the rotating body; When the first skin reference piece and the second skin reference piece undergo longitudinal displacement, the rotating body is used to decompose the displacement of the first skin reference piece and the second skin reference piece on both sides into an average displacement component and a differential displacement component, wherein the average displacement component drives the dynamic reference piece to move longitudinally, and the differential displacement component drives the rotating body to rotate for compensation.

[0011] Furthermore, the differential averaging component is an averaging gear, and the first transmission component and the second transmission component are respectively a first rack and a second rack disposed on opposite sides of the averaging gear and meshing with the averaging gear; the dynamic reference component is a floating reference frame that can move longitudinally, and the central axis of the averaging gear is rotatably mounted on the floating reference frame, so that the averaging gear rotates under the combined action of the first rack and the second rack, and the longitudinal displacement of the floating reference frame corresponds to the average component of the longitudinal displacement of the first rack and the second rack.

[0012] Furthermore, the catheter marker is connected to the catheter follower via a connector.

[0013] Furthermore, the connector is a fork, a magnetic coupling element, or a flexible connector; the catheter marking element is a two-piece or open-type soft clamping structure, with an elastic pad on its inner side to prevent compression of the epidural catheter.

[0014] Furthermore, the flexible adhesive substrate is also provided with a first longitudinal guide rail and a second longitudinal guide rail. The dynamic reference component is slidably disposed on the first longitudinal guide rail, and the conduit follower is slidably disposed on the second longitudinal guide rail. The longitudinal sliding stroke ranges of the dynamic reference component and the conduit follower overlap at least partially.

[0015] Furthermore, the flexible adhesive substrate is also provided with a puncture observation window and a reserve buffer channel, with the reserve buffer channel located outside the puncture observation window.

[0016] Furthermore, the buffer channel is Ω-shaped or serpentine to accommodate an external catheter of a predetermined length and limit the minimum bending radius of the external catheter.

[0017] Furthermore, it also includes a distal force-relieving clamp, which is disposed at the outlet end of the margin buffer channel and is used to secure the external extension tube in a releasable manner. When the axial tensile force on the external extension tube exceeds a preset threshold, the distal force-releasing clamp releases the constraint on the external extension tube, allowing the external extension tube to slide or separate relative to the flexible adhesive substrate.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The first and second skin reference members of this invention pass through grooves on a flexible adhesive substrate and are directly adhered to the local skin on both sides of the puncture point. They can slide independently longitudinally relative to the grooves to reflect the longitudinal displacement of the local skin on both sides. The two reference members cooperate with a differential averaging member through a first and a second transmission member, respectively, so that the longitudinal displacement of the dynamic reference member corresponds to the average longitudinal displacement of the two skin reference members. When the local skin on both sides of the puncture point undergoes longitudinal displacement in the same direction and amplitude, and the surface segment of the epidural catheter does not undergo axial displacement relative to the local skin, the first skin reference member, the second skin reference member, and the catheter follower move synchronously with their respective coupled objects. The dynamic reference member translates synchronously with the average displacement of the two skin reference members, making the relative displacement between the catheter follower and the dynamic reference member approximately zero. This reduces the risk of overall translational displacement of the lower back skin being misjudged as displacement of the epidural catheter relative to the local skin.

[0019] When non-uniform longitudinal displacement occurs in the local skin on both sides of the puncture point, the first and second transmission components generate differential motion relative to the differential averaging component, causing the differential averaging component to rotate. The dynamic reference component then moves longitudinally according to the average longitudinal displacement of the first and second skin reference components. The average component of the skin displacement on both sides is characterized by the longitudinal displacement of the dynamic reference component, while the differential component is characterized by the rotation of the differential averaging component. When the surface segment of the epidural catheter does not undergo axial displacement relative to the average reference position of the local skin, the longitudinal relative displacement between the catheter follower and the dynamic reference component is approximately zero. When the surface segment of the epidural catheter undergoes axial displacement relative to the average reference position of the local skin, a corresponding longitudinal relative displacement occurs between the catheter follower and the dynamic reference component. This reduces the interference of dressing warping, local skin shearing, and asymmetric deformation on the determination of the relative displacement of the epidural catheter. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 This is a top view of the epidural catheter differential compensation and fixation device of the present invention; Figure 2 This is a partial structural cross-sectional view of the epidural catheter differential compensation and fixation device of the present invention; Figure 3 This is a schematic diagram of the structure of the first transmission component, the second transmission component, and the differential averaging component of the present invention; Figure 4 for Figure 2 Enlarged view of point A in the middle; Figure 5 for Figure 2 Enlarged view of point B in the middle.

[0022] Explanation of reference numerals in the attached drawings: 1. Flexible adhesive substrate; 101. Puncture observation window; 102. Slide groove; 2. First skin reference component; 201. First connecting part; 3. Second skin reference component; 301. Second connecting part; 4. First transmission component; 5. Second transmission component; 6. Differential averaging component; 7. Dynamic reference component; 8. First longitudinal guide rail; 9. Catheter marker component; 10. Catheter follower component; 11. Connector; 12. Second longitudinal guide rail; 13. Residual buffer channel; 14. Distal force release clamp; 15. Epidural catheter. Detailed Implementation

[0023] like Figure 1-5 As shown, an epidural catheter differential compensation fixation device includes a flexible adhesive substrate 1 for attaching to the patient's skin surface. A first skin reference element 2 and a second skin reference element 3 are respectively disposed on both sides of the flexible adhesive substrate 1 along its longitudinal direction (i.e., along the spinal direction). The first skin reference element 2 and the second skin reference element 3 are respectively disposed on both sides of the puncture site along the epidural catheter displacement monitoring direction and are used to fix them to the local skin on both sides of the puncture site to respectively acquire the longitudinal displacement of the local skin on both sides of the puncture site. A first transmission element 4 and a second transmission element 5 are respectively disposed on the first skin reference element 2 and the second skin reference element 3. A dynamic reference element 7 is slidably disposed on the flexible adhesive substrate 1 along its longitudinal direction. A differential averaging component 6 is provided on the upper part of the device. The first transmission component 4 and the second transmission component 5 cooperate with the differential averaging component 6, so that the dynamic reference component 7 forms a dynamic skin reference position based on the average components of the longitudinal displacement of the first skin reference component 2 and the second skin reference component 3. A catheter marker 9 is detachably provided on the epidural catheter 15. A catheter follower 10 is slidably provided on the flexible adhesive substrate 1 along the longitudinal direction. The catheter follower 10 is connected to the catheter marker 9. The epidural catheter 15 drives the catheter follower 10 to move along the longitudinal direction. The longitudinal relative displacement of the catheter follower 10 with respect to the dynamic reference component 7 is used to characterize the axial displacement of the epidural catheter 15 with respect to the local skin reference position.

[0024] The flexible adhesive substrate 1 is made of medical-grade polyurethane (PU) film or non-woven fabric, which has good breathability and flexibility and can conform to the deformation of the skin on the lower back. Its bottom surface is coated with medical-grade acrylic pressure-sensitive adhesive and covered with release paper (such as silicone oil release paper). Before use, the release paper can be peeled off and it can be adhered to the skin.

[0025] like Figure 2As shown, the flexible adhesive substrate 1 has a longitudinally extending groove 102. The lower parts of the first skin reference member 2 and the second skin reference member 3 are respectively connected to a first connecting part 201 and a second connecting part 301. The first connecting part 201 and the second connecting part 301 pass through the groove 102 at corresponding positions. The bottom of the first connecting part 201 and the second connecting part 301 are respectively provided with independent skin adhesion areas. The flexible adhesive substrate 1 is provided with a deformation isolation structure in the area corresponding to the groove 102 to reduce the restriction of the movement of the connecting parts by the overall deformation of the flexible adhesive substrate, so that the first connecting part 201 and the second connecting part 301 can slide longitudinally relative to the flexible adhesive substrate 1 with the corresponding local skin. Specifically, the lateral width of each of the grooves 102 is greater than the lateral width of the corresponding first connecting portion 201 and second connecting portion 301, to ensure that the first connecting portion 201 and the second connecting portion 301 have longitudinal sliding freedom within the groove 102, while allowing for a small lateral swing margin, preventing the first connecting portion 201 and the second connecting portion 301 from being jammed by the groove wall due to the overall deformation of the flexible adhesive substrate 1. A longitudinal movement gap is left between the first connecting portion 201, the second connecting portion 301 and the lower surface of the flexible adhesive substrate 1, ensuring that the reference piece can accurately reflect local skin displacement without being constrained by the overall translation of the substrate.

[0026] The differential averaging component 6 is a rotating body. The first transmission component 4 and the second transmission component 5 are respectively disposed on opposite sides of the rotating body and cooperate with the rotating body. Specifically, the differential averaging component 6 is an averaging gear. The first transmission component 4 and the second transmission component 5 are respectively disposed on opposite sides of the averaging gear and mesh with the averaging gear as a first rack and a second rack. The dynamic reference component 7 is a floating reference frame that can move longitudinally. The central axis of the averaging gear is rotatably mounted on the floating reference frame, so that the averaging gear rotates under the combined action of the first rack and the second rack, and the longitudinal displacement of the floating reference frame corresponds to the average component of the longitudinal displacement of the first rack and the second rack.

[0027] When the first skin reference 2 and the second skin reference 3 undergo longitudinal displacement, the rotating body is used to decompose the displacement of the first skin reference 2 and the second skin reference 3 on both sides into an average displacement component and a differential displacement component, wherein the average displacement component drives the dynamic reference 7 to move longitudinally, and the differential displacement component drives the rotating body to rotate for compensation.

[0028] like Figure 4As shown, a first longitudinal guide rail 8 is fixedly connected to the flexible adhesive substrate 1, and a slider structure adapted to the first longitudinal guide rail 8 is connected to the bottom of the dynamic reference component 7. The dynamic reference component 7 can be slidably mounted on the first longitudinal guide rail 8 through the slider structure.

[0029] Let the longitudinal displacement of the first skin reference component 2 be X1, the longitudinal displacement of the second skin reference component 3 be X2, and the longitudinal displacement of the dynamic reference component 7 be X... C Given an average gear with a pitch circle radius of r, under ideal no-slip conditions, the following kinematic relationship exists: X C =(X1+X2) / 2 When the first skin reference piece 2 and the second skin reference piece 3 undergo longitudinal displacement in the same direction and amplitude (i.e., when X1=X2), the two racks simultaneously push the average gear in the same direction. The average gear remains stationary and moves together with the two racks, thereby driving the dynamic reference piece 7 to move, and the amount of movement is equal to the displacement of the two skin reference pieces. When the first skin reference element 2 and the second skin reference element 3 undergo non-uniform longitudinal displacement, the two racks generate relative motion, and the average gear rotates to absorb the differential displacement component between the first skin reference element 2 and the second skin reference element 3. The rotation angle of the average gear is... =(X2-X1) / (2r). Meanwhile, the dynamic reference element 7 still generates longitudinal displacement based on the average component of the displacement of the skin reference elements on both sides, and its displacement satisfies X... C =(X1+X2) / 2. The average displacement component of the dynamic reference element 7 approaches zero only when the two skin reference elements on both sides produce approximately equal amplitude reverse displacement.

[0030] Therefore, the dynamic reference element 7 can approximately represent the dynamic average value of local skin displacement on both sides of the puncture point, eliminating the interference of local skin stretching or deformation of the main film on the reference reference.

[0031] The catheter marker 9 is connected to the catheter follower 10 via a connector 11. The connector 11 can be a fork, a magnetic coupling element, or a flexible connector. When the connector 11 is a fork, one end is fixedly connected to the outer wall of the catheter marker 9, and the other end has a U-shaped fork or annular collar that fits onto the drive pin of the catheter follower 10, allowing the catheter to swing slightly in the vertical and lateral directions while transmitting the axial movement of the catheter to the catheter follower 10. Alternatively, when the connector 11 is a magnetic coupling element, it includes a first magnet and a second magnet respectively disposed on the catheter marker 9 and the catheter follower 10. The two magnets are magnetically coupled non-contactly, transmitting the axial movement of the catheter to the catheter follower 10. The catheter marker 9 is a two-piece or open-type soft clamping structure, with an elastic pad on its inner side to prevent compression of the epidural catheter 15. Specifically, the elastic liner is made of medical-grade silicone rubber or thermoplastic elastomer (TPE), and its inner diameter is interference-fitted with the outer diameter of the epidural catheter 15. This provides sufficient clamping force to ensure that the catheter does not slip when moving axially, and also prevents the catheter lumen from being compressed due to excessive clamping force.

[0032] In the two-piece structure of the catheter marker 9, the two pieces are connected by a hinge or elastic deformable arm and closed by a snap or magnetic attraction. In use, medical personnel open the two pieces, insert the catheter into the middle, and then close and clamp them. The open-type structure is a C-shaped clamp with an opening on one side, which can be directly inserted into the outer wall of the catheter from the side.

[0033] The flexible adhesive substrate 1 is further provided with a second longitudinal guide rail 12. The catheter follower 10 is slidably disposed on the second longitudinal guide rail 12. The longitudinal sliding stroke range of the dynamic reference member 7 and the longitudinal sliding stroke range of the catheter follower 10 at least partially overlap (i.e., they are flush or substantially flush in the longitudinal direction) to facilitate the detection of the subsequent threshold trigger. Specifically, the second longitudinal guide rail 12 is disposed on one side (e.g., the left side) of the first longitudinal guide rail 8, and the two are arranged parallel to each other.

[0034] The flexible adhesive substrate 1 is also provided with a puncture observation window 101 and a residual buffer channel 13, the residual buffer channel 13 being located on the outside of the puncture observation window 101. The puncture observation window 101 is a window penetrating the flexible adhesive substrate 1, used to expose the puncture site and local skin, facilitating medical personnel to observe whether there is bleeding, redness, swelling, or exudation at the puncture site, and to read the scale markings on the surface of the epidural catheter 15.

[0035] The buffer channel 13 is Ω-shaped or serpentine, designed to accommodate an external catheter of a predetermined length and limit its minimum bending radius. Specifically, the buffer channel 13 is a groove formed on the upper surface of the flexible adhesive substrate 1. The groove has a semi-circular or U-shaped cross-section, with an inner diameter larger than the outer diameter of the epidural catheter 15, allowing the epidural catheter 15 to slide freely within the groove. The bending radius of the groove is not less than the minimum permissible bending radius of the epidural catheter 15 to avoid occlusion of the catheter lumen or flow restriction due to excessive bending. A certain length of epidural catheter 15 is pre-positioned within the buffer channel 13. When the external tubing is subjected to slight traction, this pre-positioned length is straightened to absorb the traction stroke, thereby preventing the traction force from being directly transmitted to the catheter marker 9 near the puncture point.

[0036] The device of the present invention further includes a distal force-relieving clamp 14, which is disposed at the outlet end of the margin buffer channel 13 and is used to fix the external extension tube in a releasable manner. When the axial tensile force on the external extension tube exceeds a preset threshold, the distal force-releasing fixing clip 14 releases the constraint on the external extension tube, allowing the external extension tube to slide or separate relative to the flexible adhesive substrate 1.

[0037] Specifically, the distal force-releasing fixing clip 14 achieves overload release by at least one of magnetic coupling, hook and loop fastening, or elastic pressing friction.

[0038] When using magnetic coupling: the distal force-releasing fixing clip 14 includes a magnetic female base fixed to the flexible adhesive substrate 1 and a magnetic male clip sleeved on the outer wall of the external extension tube. The magnetic female base and the magnetic male clip are attracted by a permanent magnet (e.g., a neodymium iron boron magnet). The magnitude of the attraction force is calibrated by selecting magnets with different magnetic energy products or adjusting the magnet spacing, with a preset release force threshold F0. When the axial tensile force on the external extension tube is less than F0, the male clip is attracted to the female base, and the extension tube is fixed; when the tensile force exceeds F0, the male clip detaches from the female base, the extension tube separates from the substrate, and the internal flow path of the epidural catheter 15 remains unobstructed. In this solution, the magnetic female base and magnetic male clip can be directly selected from commercially available medical-grade magnetic clip assemblies.

[0039] When using a hook-and-loop fastener: the distal force-releasing clamp 14 includes a looped hook-and-loop strap fixed to the flexible adhesive substrate 1 and a hooked strap wrapped around the outer wall of the external extension tube. The two provide fixing force through hook-and-loop overlap. The preset release force threshold is controlled by adjusting the overlap area.

[0040] When using the elastic clamping type: the distal force-relieving fixing clip 14 includes a C-shaped elastic groove fixed to the flexible adhesive substrate 1, and the external extension tube is clamped within the groove. The inner wall of the groove is provided with flexible clamping protrusions, which provide positive pressure through a spring or elastic arm, thereby generating friction to fix the extension tube. When the tensile force exceeds the maximum static friction, the extension tube slips out of the groove.

[0041] The present invention also includes an outer displacement threshold and an inner displacement threshold disposed on the dynamic reference component 7, as well as a maximum displacement memory. The outer displacement threshold and the inner displacement threshold are respectively disposed on both sides (i.e., the upper and lower sides) of the dynamic reference component 7, and are used to detect whether the longitudinal displacement of the conduit follower 10 relative to the dynamic reference component 7 exceeds the preset outer displacement threshold and the inner displacement threshold, respectively. As one possible implementation, the outer displacement threshold and the inner displacement threshold are respectively miniature limit switches or Hall effect proximity switches. When a miniature limit switch is used (e.g., the SS-5GL series manufactured by Omron or the AM516 series miniature tactile switches of Panasonic), the housing of the limit switch is fixed on the dynamic reference component 7, and its contact faces the conduit follower 10. When the conduit follower 10 moves longitudinally to the preset limit position, the conduit follower 10 directly presses against the contact of the limit switch, causing the normally open contact of the limit switch to close, thereby outputting an electrical trigger signal to an external alarm circuit. When a Hall effect proximity switch is used (e.g., Allegro A3144 or STMicroelectronics' Matching Hall series), a permanent magnet (e.g., a neodymium iron boron magnet) is embedded in the conduit follower 10, and a Hall effect switch chip is fixed at a corresponding position on the dynamic reference component 7. When the conduit follower 10 moves to its limit position, the permanent magnet approaches the Hall effect switch chip, and the Hall effect switch chip outputs a flip-level signal, triggering an external alarm. The maximum displacement memory includes a linear displacement sensor and a microcontroller module electrically connected to the linear displacement sensor. The housing of the linear displacement sensor (e.g., Novotechnik's TR series miniature resistive linear displacement sensor or the domestic Miron KTR series) is fixed to the flexible adhesive substrate 1, and its tap link is fixedly connected to the conduit follower 10, moving synchronously with the conduit follower 10 and converting the real-time longitudinal position of the conduit follower 10 into a resistance or voltage signal. The microcontroller module has a built-in analog-to-digital converter (ADC) and an EEPROM. The microcontroller (e.g., an STM8L series low-power microcontroller from STMicroelectronics, or a domestically produced CH32V003 series) reads the real-time position signal of the linear displacement sensor at a preset sampling frequency (e.g., 10Hz), and stores the maximum longitudinal displacement value of the catheter follower 10 relative to the initial zero position in the EEPROM in real time through an internal comparison algorithm. Since the EEPROM is a non-volatile memory, the maximum displacement value is retained even if the device is completely powered off. When medical personnel need to verify the value, they can directly read the maximum displacement value through an external display module (e.g., a miniature LCD display) connected to the microcontroller, or retrieve the maximum value stored in the EEPROM via a handheld reading device through a wired or wireless interface. The wireless interface is preferably Bluetooth Low Energy (BLE) or Near Field Communication (NFC).

[0042] The present invention also includes a threshold adjustment component connected to the outer and inner threshold adjustment components for adjusting the size of the preset threshold. The threshold adjustment is achieved via a digital potentiometer or a software-adjustable threshold parameter located in the microcontroller. Medical personnel input the desired threshold value (e.g., 2mm, 5mm, 10mm) via an external button or communication interface. The microcontroller updates the comparator reference voltage or software comparison threshold based on the set value. Preferably, the threshold adjustment range is 2–10mm, with 5mm being a commonly used clinical setting.

[0043] In addition, a transparent, openable top cover is provided on the flexible adhesive substrate 1. This transparent, openable top cover covers the differential averaging component 6, the dynamic reference component 7, the catheter follower component 10, the outward displacement threshold component, the inward displacement threshold component, the maximum displacement memory component, and the margin buffer channel 13. One side of the transparent, openable top cover is connected to the flexible adhesive substrate 1 via a hinge or flexible membrane, while the opposite side has a snap-fit ​​or magnetic snap for closing and locking the top cover. The transparent, openable top cover is injection molded from a medical-grade transparent polymer material (e.g., polycarbonate PC or polymethyl methacrylate PMMA) with a light transmittance of not less than 90%, allowing medical personnel to directly observe the position and status of the internal components, the catheter routing, and the puncture point condition without opening the top cover. When it is necessary to manually reset the maximum displacement memory component or adjust the threshold, the transparent, openable top cover can be opened for operation.

[0044] The working process of this invention is as follows: (a) Installation and initial setup of the device After completing the epidural puncture and placing the catheter 15, peel off the release paper from the bottom of the flexible adhesive substrate 1, align the puncture observation window 101 with the puncture point, and attach the substrate 1 to the skin of the lower back. Press the first skin reference piece 2 and the second skin reference piece 3 respectively, so that the connecting parts 201 and 301 at their bottoms pass through the groove 102 and adhere to the local skin on both sides of the puncture point, ensuring that each reference piece can slide independently longitudinally within the groove 102.

[0045] Manually push the dynamic reference element 7 until it aligns with the zero mark, so that the average gear shaft is in the initial position. Clamp the catheter marker 9 to the outer wall of the epidural catheter 15 and couple it to the catheter follower 10 via the connector 11. Push the catheter follower 10 until its zero mark coincides with the dynamic reference element 7. Set the outward and inward movement thresholds using the threshold adjustment element.

[0046] Insert the conduit 15 into the Ω-shaped buffer channel 13, fix the external extension tube to the distal force-releasing clamp 14, and close the transparent top cover.

[0047] (II) Dynamic monitoring and differential compensation mechanism Common-mode displacement (overall skin translation): When the entire back skin moves longitudinally, and the surface segment of the epidural catheter 15 does not undergo axial displacement relative to the local skin, the first skin reference element 2 and the second skin reference element 3 produce displacements in the same direction and amplitude or approximately in the same direction and amplitude, satisfying X1≈X2. The two racks act together on the average gear, causing the dynamic reference element 7 to produce a longitudinal movement corresponding to the average displacement of the two skin reference elements, i.e., Xc=(X1+X2) / 2. At the same time, the surface segment of the epidural catheter 15 moves synchronously with the local skin, and through the catheter marker element 9, it drives the catheter follower element 10 to produce a corresponding displacement X. k , making X k ≈X c Therefore, the relative displacement Δ = X of the follower 10 of the conduit relative to the dynamic reference 7 is... k -X c ≈0, thereby reducing the interference of overall skin translation on the judgment of relative catheter displacement.

[0048] Differential displacement (non-uniform local skin expansion and contraction): When non-uniform longitudinal displacement occurs in the local skin on both sides of the puncture point, differential motion occurs between the first transmission component 4 and the second transmission component 5, and the average gear rotates by an angle of _____. =(X2-X1) / (2r), and at the same time, the dynamic reference component 7 moves longitudinally according to the average component of the displacement of the skin reference components on both sides, satisfying X c =(X1+X2) / 2. Therefore, the average component of the skin displacement on both sides is characterized by the longitudinal displacement of the dynamic reference element 7, while the differential component is characterized by the rotation of the average gear. When the surface segment of the epidural catheter 15 does not undergo axial displacement relative to the dynamic skin reference position, the relative displacement between the catheter follower 10 and the dynamic reference element 7 remains small; when the surface segment of the epidural catheter 15 undergoes axial displacement relative to the dynamic skin reference position, a corresponding longitudinal relative displacement occurs between them.

[0049] Catheter relative displacement detection: When the surface segment of the epidural catheter 15 undergoes axial displacement relative to the local skin reference position near the puncture point, the catheter marker 9 drives the catheter follower 10 to generate a longitudinal displacement X through the connector 11. k The longitudinal relative displacement Δ=X of the guide tube follower 10 relative to the dynamic reference element 7. k -X c Used to characterize the axial displacement of the epidural catheter 15 surface segment relative to the dynamic skin reference position; when the relative displacement exceeds a preset threshold, a corresponding displacement prompt or alarm can be triggered.

[0050] (III) Tiered management Mild traction: When the tension is less than the release clamp threshold and less than the buffer channel resistance, the pre-installed conduit in the Ω buffer channel 13 is straightened to absorb the stroke, and the tension is not transmitted to the marker 9 and follower 10, and no alarm is triggered.

[0051] Moderate traction: After the preset length of the buffer channel 13 is fully straightened, the traction force is transmitted to the marker 9. If the amount of catheter withdrawal exceeds the threshold, an alarm is triggered.

[0052] Severe traction: When the pulling force exceeds the release threshold of the distal force release clamp 14, the force release clamp 14 releases the constraint on the external extension tube, and the extension tube separates from the base 1, avoiding damage to the catheter due to violent traction.

[0053] (iv) Alarm recording and reset When an alarm is triggered, the microcontroller drives the LED indicator and buzzer, and stores the maximum displacement value of the catheter follower 10 in the EEPROM. Medical staff can read the real-time displacement and historical maximum value through the LCD screen or a handheld reader. After verification, they can send a reset command through the button or communication interface, and the microcontroller will clear the EEPROM record and return it to zero.

[0054] (v) Removal Open the transparent top cover, loosen the marker 9 to remove the tube 15, tear off the base 1, and dispose of it in one go.

[0055] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A differential compensation and fixation device for epidural catheters, characterized in that: The device includes a flexible adhesive substrate (1) for attaching to the surface of a patient's skin. A first skin reference element (2) and a second skin reference element (3) are respectively disposed on both longitudinal sides of the flexible adhesive substrate (1). The first skin reference element (2) and the second skin reference element (3) are respectively disposed on both sides of the puncture site along the epidural catheter displacement monitoring direction and are used to fix them to the local skin on both sides of the puncture site to obtain the longitudinal displacement of the local skin on both sides of the puncture site. A first transmission element (4) and a second transmission element (5) are respectively disposed on the first skin reference element (2) and the second skin reference element (3). A dynamic reference element (7) is slidably disposed on the flexible adhesive substrate (1) along the longitudinal direction. A differential averaging component (6) is disposed on the dynamic reference element (7). The transmission component (4) and the second transmission component (5) cooperate with the differential averaging component (6) respectively, so that the dynamic reference component (7) forms a dynamic skin reference position based on the average longitudinal displacement components of the first skin reference component (2) and the second skin reference component (3); a catheter marker (9) is detachably provided on the epidural catheter (15), and a catheter follower (10) is slidably provided on the flexible adhesive substrate (1) along the longitudinal direction. The catheter follower (10) is connected to the catheter marker (9), and the epidural catheter (15) drives the catheter follower (10) to move along the longitudinal direction; the longitudinal relative displacement of the catheter follower (10) relative to the dynamic reference component (7) is used to characterize the axial displacement of the epidural catheter (15) relative to the local skin reference position.

2. The epidural catheter differential compensation and fixation device according to claim 1, characterized in that: The flexible adhesive substrate (1) has a longitudinally extending groove (102). The lower parts of the first skin reference (2) and the second skin reference (3) are respectively provided with a first connecting part (201) and a second connecting part (301). The first connecting part (201) and the second connecting part (301) pass through the groove (102) at the corresponding positions. The bottom of the first connecting part (201) and the second connecting part (301) are respectively provided with independent skin adhesion areas. The flexible adhesive substrate (1) is provided with a deformation isolation structure in the area corresponding to the groove (102) to reduce the restriction of the movement of the connecting part by the overall deformation of the flexible adhesive substrate, so that the first connecting part (201) and the second connecting part (301) can slide longitudinally relative to the flexible adhesive substrate (1) with the corresponding local skin.

3. The epidural catheter differential compensation and fixation device according to claim 1, characterized in that: The differential averaging component (6) is a rotating body, and the first transmission component (4) and the second transmission component (5) are respectively disposed on opposite sides of the rotating body and cooperate with the rotating body; When the first skin reference (2) and the second skin reference (3) undergo longitudinal displacement, the rotating body is used to decompose the displacement of the first skin reference (2) and the second skin reference (3) on both sides into an average displacement component and a differential displacement component, wherein the average displacement component drives the dynamic reference (7) to move longitudinally, and the differential displacement component drives the rotating body to rotate for compensation.

4. The epidural catheter differential compensation and fixation device according to claim 3, characterized in that: The differential averaging component (6) is an averaging gear. The first transmission component (4) and the second transmission component (5) are respectively a first rack and a second rack disposed on opposite sides of the averaging gear and meshing with the averaging gear. The dynamic reference component (7) is a floating reference frame that can move longitudinally. The central axis of the averaging gear is rotatably mounted on the floating reference frame, so that the averaging gear rotates under the combined action of the first rack and the second rack, and the longitudinal displacement of the floating reference frame corresponds to the average component of the longitudinal displacement of the first rack and the second rack.

5. The epidural catheter differential compensation and fixation device according to claim 1, characterized in that: The catheter marker (9) is connected to the catheter follower (10) via a connector (11).

6. The epidural catheter differential compensation and fixation device according to claim 5, characterized in that: The connector (11) is a fork, a magnetic coupling element or a flexible connector; the catheter marker (9) is a two-piece or open-type soft clamping structure, with an elastic pad on its inner side to prevent compression of the epidural catheter (15).

7. The epidural catheter differential compensation and fixation device according to claim 1, characterized in that: The flexible adhesive substrate (1) is also provided with a first longitudinal guide rail (8) and a second longitudinal guide rail (12). The dynamic reference component (7) is slidably disposed on the first longitudinal guide rail (8), and the catheter follower component (10) is slidably disposed on the second longitudinal guide rail (12). The longitudinal sliding stroke ranges of the dynamic reference component (7) and the catheter follower component (10) at least partially overlap.

8. The epidural catheter differential compensation and fixation device according to claim 1, characterized in that: The flexible adhesive substrate (1) is also provided with a puncture observation window (101) and a reserve buffer channel (13), and the reserve buffer channel (13) is located outside the puncture observation window (101).

9. The epidural catheter differential compensation and fixation device according to claim 8, characterized in that: The buffer channel (13) is Ω-shaped or serpentine and is used to accommodate an external catheter of a predetermined length and limit the minimum bending radius of the external catheter.

10. The epidural catheter differential compensation and fixation device according to claim 8, characterized in that: It also includes a distal force-releasing fixing clip (14), which is disposed at the outlet end of the margin buffer channel (13) and is used to fix the external extension tube in a releasable manner; When the axial tensile force on the external extension tube exceeds a preset threshold, the distal force-releasing fixing clip (14) releases the constraint on the external extension tube, so as to allow the external extension tube to slide or separate relative to the flexible adhesive substrate (1).

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