Sie können Operatoren mit Ihrer Suchanfrage kombinieren, um diese noch präziser einzugrenzen. Klicken Sie auf den Suchoperator, um eine Erklärung seiner Funktionsweise anzuzeigen.
Findet Dokumente, in denen beide Begriffe in beliebiger Reihenfolge innerhalb von maximal n Worten zueinander stehen. Empfehlung: Wählen Sie zwischen 15 und 30 als maximale Wortanzahl (z.B. NEAR(hybrid, antrieb, 20)).
Findet Dokumente, in denen der Begriff in Wortvarianten vorkommt, wobei diese VOR, HINTER oder VOR und HINTER dem Suchbegriff anschließen können (z.B., leichtbau*, *leichtbau, *leichtbau*).
Der Artikel befasst sich mit der Konzeption und Implementierung eines neuartigen abnehmbaren Bronchoskops, das speziell auf die endotracheale Intubation zugeschnitten ist. Traditionelle Bronchoskope sind zwar für die Navigation der Atemwege unverzichtbar, erfordern aber oft langwierige Eingriffe, wenn ein ETT-Ersatz erforderlich ist. Das vorgeschlagene abnehmbare Bronchoskop löst dieses Problem, indem es dem Griff ermöglicht, sich vom flexiblen Einführschlauch zu lösen, was einen schnellen ETT-Austausch ermöglicht, ohne das gesamte Bronchoskop zu entfernen. Die Kerninnovation liegt im Mikrotransmissionssystem, bei dem Links- und Rechtshänder-Schrauben das distale Ende des Bronchoskops steuern. Dieses System wird noch durch ein Getriebe verbessert, das die Rotationsbewegung in lineare Bewegung umwandelt, was eine präzise Steuerung der Bronchoskopspitze ermöglicht. Zum Design gehört auch ein ausgeklügeltes Ablösesystem mit einer Taste, die das Einführungsrohr sicher einrastet und entriegelt. Der Artikel untersucht eingehend die Mechanik des Mikroübertragungssystems, einschließlich der Auswirkungen von Schraubenabstand und Führungswinkel auf den Kraftbedarf. Darüber hinaus werden experimentelle Ergebnisse zur Verdrängungs- und Ausfallleistung von 3D-gedruckten Mikroübertragungssystemen präsentiert, was die Bedeutung von Materialauswahl und Fertigungsoptimierung unterstreicht. Die Ergebnisse deuten darauf hin, dass weitere Fortschritte bei der Materialauswahl und der Finite-Elemente-Analyse die Leistung und Haltbarkeit der Mikroübertragung signifikant verbessern könnten. Insgesamt bietet der Artikel einen umfassenden Überblick über das Design, die Implementierung und potenzielle Verbesserungen eines abnehmbaren Bronchoskops, was es zu einer unschätzbaren Ressource für Fachleute macht, die an der Weiterentwicklung der Medizintechnik interessiert sind.
KI-Generiert
Diese Zusammenfassung des Fachinhalts wurde mit Hilfe von KI generiert.
Abstract
A novel detachable bronchoscope with a 3D printed micro-transmission is investigated. The micro-transmission controls the motion of the tip of the bronchoscope and is embedded in one end of the flexible insertion section of the bronchoscope. The micro-transmission allows manipulation of the distal end through the translation of guide nuts that are connected to the tip of the bronchoscope through so-called “angulation” wires. The displacement of the guide nuts on the left and right-handed screw sections and the control of the distal end of the bronchoscope are investigated. The maximum tensile force on the angulation wire before failure is determined experimentally for different screw pitches.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
1 Introduction
A flexible bronchoscope is an essential medical device used to navigate deep into a patient's respiratory tract. The distal tip of the bronchoscope is a multi-body linkage that is manipulated from the handle of the device. Typical flexible bronchoscopes include channels for suction, oxygenation, and procedural biopsies(Kohanfars et al. 2021). The distal end of the bronchoscope is controlled by a lever on the handle and allows the operator to change the angular position of the tip of the bronchoscope. Bronchoscopes often incorporate a light source and camera for visualization of tissue at the distal end of the device. In Fig. 1, a typical commercially available bronchoscope is shown including the handle, the insertion section, the bending section, the display unit connector, the working channel access port, and the endotracheal tube (ETT) retainer.
Fig. 1
Typical commercially available disposable bronchoscope(Marini and Abington 1999)
Bronchoscopes can be utilized for the common procedure of endotracheal intubation with approximately 40 million cases yearly in the US alone. This number has increased in recent years due to the COVID-19 pandemic(Sanovas 2017). In preparation for an intubation, the endotracheal tube (ETT) is loaded over the flexible insertion tube and secured in place with the ETT retainer shown in Fig. 1. After inserting the tip of the bronchoscope in the trachea, the ETT is advanced into the trachea over the bronchoscope. Thereafter, the bronchoscope is removed leaving the ETT in place and the patient is connected to a ventilator. Failure of securing the ETT within the treachea may occur for various reasons, such as altered anatomy or mismatch of ETT diameter relative to the patient’s laryngotracheal aperture (Sofi and El-Gammal 2010). In this case, the entire bronchoscope- ETT assembly must be removed, a new ETT reloaded and the intubation process repeated. This leads to a prolonged duration of time when the patient remains with an unprotected airway and compromised ventilation. One solution to reduce the ETT replacement time during intubation is the use of a detachable bronchoscope. This allows for detachment of the bronchoscope handle leaving the flexible insertion tube securely within the trachea. The first ETT may then be removed and a new ETT inserted over the insertion tube and into the trachea. The bronchoscope may be reattached for further visual confirmation if necessary or the insertion tube may be removed with prompt re-initiation of ventilation.
Anzeige
Previous researchers have developed detachable bronchoscopes(Marini and Abington 1999; Krupa and Leominster 2008). Typical detachable systems have been designed with a pulley mechanism that requires pull wires to manipulate the distal linkage end. For example, Carlson et al. (2015) have developed a detachable bronchoscope using a worm gear drive with two pulleys to lengthen and shorten the wires of the bronchoscope that move the distal end. These pulley systems are similar to conventional mechanisms in current bronchoscopes (Holland and Shoop 2000). Another approach was implemented by Hunter et al. (2015) who developed a DC motor-controlled capstan drive system to control the distal end of the endoscope. Table 1 summarizes these comparisons.
Table 1
Comparison of key features of endoscopes found in the literature
In the present study, the design and implementation of a novel detachable bronchoscope with a micro-transmission system is investigated. The control handle of the bronchoscope is designed to detach from the flexible part carrying the distal end so that the endotracheal tube can be removed and replaced with a different endotracheal tube during a procedure. If decoupled, the transmission is no longer operable from the handle of the bronchoscope. When the system is reattached, two translating nuts on the micro-transmission produce the behavior of a pulley system and enable control of the distal end.
2 Schematics of design of a conventional bronchoscope
The mechanical design of a conventional bronchoscope is shown in Fig. 2 The bronchoscope consists of a handle, a guide wire, and a flexible multi-body linkage at the tip of the flexible section of the bronchoscope. If the lever on the handle of the bronchoscope is turned, the guide wire is pulled, and a tensile force is exerted at the tip of the bronchoscope where the guide wire is connected to the last link of the bronchoscope. The tensile force causes a rotation of the individual links around their respective pin joints as shown in Fig. 2.
In Fig. 3, the prototype of our detachable bronchoscope is shown. The flexible insertion tube of the proposed device is detachable from the handle and includes all features of a typical commercially available bronchoscope. The detachment system secures the insertion tube in place until it is released by the operator through use of the detachment system button on the handle. The bronchoscope has a control knob on the handle that can be rotated to control the motion of the distal end of the device. The rotary motion of the control knob is converted into linear motion of the micro-transmission, causing a change in the length of the wires from the micro-transmission to the distal end. This change in wire length controls the angle of rotation of the distal end. The insertion section of the device accommodates space for a working channel of at least 0.8 mm.
In addition, it must incorporate ports that allow for engaging the visualization and illumination component of the detachable bronchoscope. The device, shown in Fig. 4, has an outer diameter insertion section of 5.25 mm which is similar to commercially available bronchoscopes. In Fig. 4a, shows the control handle and insertion section of the device attached, while Fig. 4b shows the handle detached from the insertion section.
Fig. 4
Detachable bronchoscope prototype with handle a attached to flexible section and b detached from flexible section
With the detachment system connected, the control knob attaches to the micro-transmission system by a gearbox housed inside the control handle. The knob acts as the input for the gearbox, and the output of the gearbox will be the input of the micro-transmission. When the micro-transmission system rotates due to the gearbox motion, the nuts translate in the direction of the axis of the transmission if they are constrained against circumferential motion. By connecting actuation wires to the translating nuts, the operator can apply tension to one of the wires through the gearbox and micro-transmission system, thereby actuating the distal end. A close-up photograph of the control handle is shown in Fig. 5.
Fig. 5
Prototype of control handle of the detachable bronchoscope with outside and inside illustrated
The gearbox (Fig. 6) housed inside the handle converts rotation of the control knob from the user to rotation of the micro-transmission and, ultimately, rotation of the flexible tip of the bronchoscope. Rotation of the micro-transmission is accomplished through the compound gear system shown in Fig. 6. The gears have a ratio of 1:5, i.e., one revolution of the control handle knob produces five revolutions of the micro-transmission.
Fig. 6
Schematic of gearbox in handle of bronchoscope. a Gear system illustrated without outer gearbox housing. b Side view of gearbox system with axial rods and bushings
The detachment system (Fig. 7) enables a physician to quickly change the endotracheal tube during an intubation procedure. The detachment system incorporates two springs, a higher stiffness spring pushing downwards against the lower stiffness spring. The button is allowed to slide along the linear guide, shown in Fig. 7. To engage the detachment system, the insertion tube is inserted into the insertion location (Fig. 7) of the system. As shown in Fig. 8, the detachment system incorporates concave divots on the insertion tube, acting as multiple locking points to lock the insertion tube. The detachment system engages the divots by means of three small stainless-steel balls placed at an angular separation of 120°.
Fig. 7
Detachment system showing the button slider and linear guide. The button pushes against the higher stiffness spring to release the system
To engage the detachment system on the concave divots, the detachment button must be pushed upwards, to be placed in an open position (Fig. 8a). The insertion tube can then be inserted, and the detachment button is released. This engages the three stainless balls on the insertion tube. To release, the detachment button is lifted, and the insertion tube can be removed. The detachment system has two separate states, the open (Fig. 8a) and closed (Fig. 8b) state.
2.4 Micro-transmission system
The micro-transmission system (Fig. 9) is located within the insertion tube at the proximal end of the flexible portion of the endoscope. It consists of a screw with a left-handed and a right-handed thread section (Fig. 10a). On each thread section is a guide nut that is prevented from rotation, i.e., the guide nut can only translate during rotation of the screw (Fig. 10b) If the screw is rotated due to motion of the control knob and the gear train, the guide-nuts on the screw will translate in opposite directions. A wire is attached to each guide nut, connecting it to the distal end of the bronchoscope (Fig. 9). With rotary motion of the control knob, a tension force is developed in the micro-transmission system that causes bending of the distal end of the flexible part of the bronchoscope (Fig. 9).
Fig. 9
Conceptual motion diagram of micro-transmission demonstrating the movement of the guide-nuts and linkage system with an input rotation
a Transmission system demonstrated with guide nuts, b cross-section of transmission system demonstrating multi-start threaded design, and c Transparent insertion tube with drivetrain
The guide nuts were manufactured using stereolithography 3D printing. Figure 10 shows the micro-transmission system CAD models developed for the detachable bronchoscope. The location of the micro-transmission inside the proximal portion of the device is shown in Fig. 10c. One of the screw systems is illustrated in Fig. 11, with the top half of the screw and nut assembly shown at 10 × magnification. The current screw system, seen in Fig. 11, utilizes an outer diameter of 1.25 mm.
Fig. 11
Micro-transmission system screw thread with one guide-nut shown for scale under a microscope at 10 × magnification
The key characteristics required to understand the mechanics of the screw are illustrated in Fig. 12. The pitch of the screw is defined as the distance between adjacent threads. This is the distance that the nut moves in the longitudinal direction as the nut is rotated through one full revolution (Ball 2019). The lead of the screw is defined as the distance traveled by the nut per revolution. In a single started thread, the lead equals the pitch of the screw.
Fig. 12
Illustration of a screw with annotated terminology
If a torque is applied to a screw, the associated forces can be calculated through geometric analysis. To do this, we consider the wedge illustrated in Fig. 13. In this figure, the lead or helical angle (\(\lambda \)) of the thread is the angle that represents the constant rotation (or helical path) of a thread. This angle is given by the relationship between the lead distance and the major diameter of the screw, i.e.,
Fig. 13
Geometrical representation of a section of a screw thread shown as a wedge with associated forces in question noted
In Fig. 13, this angle (\(\lambda \)) is shown with reference to the screw thread profile. The hypotenuse of the triangle forms the path that the length of the nut takes along the helical thread. Increasing the helix angle will increase the incline of the thread, which indicates a larger lead distance for the screw. When the diameter of the screw shrinks, the lead angle must be increased to maintain a constant lead distance. Depending on the helix angle, the force \({F}_{L}\) can be determined. From Fig. 13 the following static equilibrium equations can be obtained from the free body diagram:
where \({\mu }_{s}\) is the coefficient of static friction, \(\alpha \) the thread angle, N the normal force applied at an angle \(\lambda \), and F the force of the nut being translated. From Eqs. 2 and 3, we obtain \({F}_{L}\) as
Equation 6 shows the effect of the lead distance \(l\) and its effect on the force required to move the nut. A larger lead distance with respect to a fixed force \(F\) would require a higher force \({F}_{L}\). The force \(F\) is the tensile force in the angulation wire of the bronchoscopes linkage system. Assuming that the perpendicular distance from the center of the shaft to the nut on a screw is the radial distance, \(\frac{{d}_{m}}{2}\), the torque, \({T}_{L}\), is determined by
$${T}_{L}={F}_{L}\frac{{d}_{m}}{2}$$
(7)
The above equation can be used to estimate the torque or twisting force required to translate a nut along a screw shaft. The tip of the bronchoscope is composed of hollow links that are joined by revolute joints. The wires that are attached to the links, the so-called angulation wires, are symmetrically attached so the travel of the nut causes one of the wires to pull which initiates rotation of the distal end of the bronchoscope.
2.6 Displacement study and failure investigation of 3D printed micro-transmission systems
The displacement of the guide nuts in the 3D printed micro-transmission system is critical to the operation and accuracy of the detachable bronchoscope. The performance and failure of the 3D printed micro-transmission was tested using 3D printed component in a specially designed test stand. Insertion tube components including drivetrain screw, one guide-nut, transmission driver, endcap, and outer tube were 3D printed (Formlabs Black Resin) and assembled similar to the prototype. Three different screw and nut designs with varying pitch (3, 4, 5 mm) were printed and assembled. The front half of the insertion tube casing was removed to allow observation of the motion of the guide nuts. All 3D printed parts were cleaned with isopropyl alcohol (IPA) and UV-cured for 60 min at 60 °C to enhance photopolymer material strength. A 1.8° two-phase stepper motor was used to rotate the transmission driver of the drivetrain using a microcontroller (Arduino Uno). The experimental set-up for this investigation is shown in Fig. 14a, b.
Fig. 14
a Test set-up for the guide nut displacement measurements, b Experimental test set-up with webcam
The stepper motor rotated the transmission at 90° increments for each printed drivetrain model. The set-up was placed in front of a webcam which took snapshots of the guide nut position after every incremental turn of the motor. An image-processing application designed in MATLAB was used to evaluate the pixel distance between nut positions across all snapshot frames.
Several models of the micro-transmission system were also tested to evaluate the force at which failure of the system due to breakage occurred (Fig. 15). Like the distance experiment, all components of the insertion tube were 3D printed with Formlabs Black resin, IPA-cleaned and UV-cured for 60 min at 60 °C. The angulation wire was attached to the guide nut hole with super glue. Nine total models were prepared; three each for 3, 4, and 5 mm screw pitches to compare the effects of pitch length on force to failure.
Fig. 15
Test set-up for micro-transmission force experiment
In Fig. 16, the experimental measurements for the displacement of the nuts on the micro-transmission are shown as a function of the number of rotations of the micro-transmission. Samples were pre-tensioned, and the load cell was zeroed prior to experimentation. We observe that the displacement is nearly linear, as to be expected because of burrs and imperfections in the manufacturing of the 3D printed parts. Imperfections observed in the parts are more common in smaller pitch drivetrains due to the limited resolution of available 3D printers. These unwanted burrs can be eliminated by further polishing the internal surface of the insertion tubes.
Fig. 16
Guide nut displacement versus the number of total screw rotations. Theoretical predictions are shown with dashed lines and compared with experimental data (solid lines)
In Fig. 17 the force at failure is shown versus the number of rotations of the micro-transmission. Failure was commonly observed due to breakage at the guide-nuts and wire attachment points and sometimes due to guide-nuts slipping out of the insertion tube cavity. Figure 17a shows the experimental results for failure of the 3 mm pitch transmission, indicating an average force at failure of 12.2N (standard deviation, σstd = 0.6N) with a maximum force of 12.8N and minimum force of 11.8N. Higher forces for failure to occur can be achieved by the proper choice of materials. In particular, by using stainless steel or nylon for the micro-transmission system, friction and drive train reliability will be improved. By utilizing dissimilar materials, we can reduce friction and wear of the micro-transmission.
Fig. 17
Force at failure versus the number of rotations for (a) 3 mm micro-transmission system, (b) 4 mm micro-transmission system (c) 5 mm micro-transmission system
Increasing the pitch of the micro-transmission system resulted in a decrease of the failure force. In the 4 mm pitch case shown in Fig. 17b, the force at which breakage occurred was 10.2N (σstd = 0.6N). For the 5 mm pitch experiment the breakage force was 7.8N (σstd = 0.9N) (Fig. 17 c). The breakage force results of Fig. 17 are summarized in Fig. 18. Clearly, the pitch of the micro-transmission system is an important design parameter in the detachable bronchoscope design.
Fig. 18
Failure force versus pitch of micro-transmission system
A detachable bronchoscope with a micro-transmission system utilizing a left and right-handed screw system has been designed and implemented for use in the insertion section of a detachable bronchoscope. The effects of the screws design parameters, such as the helix angle and screw pitch, were examined. 3D printed micro-transmission systems of 3 mm, 4 mm, and 5 mm pitch were investigated to study their linearity and failure performance. Photopolymer 3D printed material was successfully used for prototypes. Further improvements in the manufacturing process are needed to optimize the performance and reliability of the 3D printed system. Moreover, to further enhance the reliability and performance of the micro-transmission, it is crucial to conduct finite element analysis that specifically addresses material selection and optimization, focusing on the ability to withstand higher tensile forces such as stainless steel or nylon. This analysis will aid in improving the overall performance and durability of the micro-transmission design.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Ball RS (2019) Theory of screws: a study in the dynamics of a rigid body. Creative Media Partners, LLC
Carlson TP, Moen CW, Soli TD, Greminger MA, Martinelli JJ (2015) Detachable bronchoscope with a disposable insertion tube. ASME. J Med Devices 9(2):020933CrossRef
Holland P, Shoop N (2000) Flexible endoscopes: structure and function–the air and water system. Gastroenterol Nurs 23(6):264–268CrossRef
Hunter IW, Chen Y, Oliverira JM (2015) U.S. Patent No. US 2015/0011830 A1. Washington, DC: U.S. Patent and Trademark Office
Kohanfars M, Li Y, Morris K, Ahadian F, Talke F (2021) Design of a 3D printed micro-transmission system for a detachable bronchoscope. Inform Storage Process Syst 1(1):3. https://doi.org/10.1115/ISPS2021-65367CrossRef
Krupa JR, Leominster M (2008) Endoscope with Detachable Elongation Portion, Provisional application No. 60/879,718
Marini JL Abington M (1999) Endoscopic Instrument with Removable Front End, 6,077,290j
Die im Laufe eines Jahres in der „adhäsion“ veröffentlichten Marktübersichten helfen Anwendern verschiedenster Branchen, sich einen gezielten Überblick über Lieferantenangebote zu verschaffen.
