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Endoscope design for the future
ARTICLE IN PRESS Techniques in Gastrointestinal Endoscopy 000 (2019) 1 7
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Techniques in Gastrointestinal Endoscopy journal homepage: www.techgiendoscopy.com/locate/tgie
Endoscope design for the future Azadeh Khanicheh, PhDa,*, Amandeep K. Shergill, MD, MSb a b
EnVision Endoscopy, 15 Fairfax St, # 2, Somerville, Massachusetts 02144 San Francisco VA Medical Center, University of California, San Francisco, San Francisco, California
A R T I C L E
I N F O
Article history: Received 31 January 2019 Revised 22 April 2019 Accepted 29 May 2019 Keywords: Ergonomics Flexible endoscope Design requirements Scope interaction
A B S T R A C T
A preponderance of evidence, primarily from surveys, has shown that gastroenterologists suffer from overuse injuries and pain of hand/fingers, wrist, forearm, shoulder, and back due to awkward postures, high forces, and repetitive movements during endoscopy. Although flexible endoscopes are brilliantly designed compact instruments that include light and image guides, irrigation channels, suction channel, biopsy channels and are the result of many technological advancements and iterations in the last 5 decades, not much has changed in their basic functions, layout, ergonomic design, and usability. The required hand-tool interaction in order to maneuver the endoscope inside the intestinal lumen, such as stabilizing the control section while manipulating dials with the left hand while simultaneously torqueing, pushing, and/or pulling the insertion tube with the right hand, are still unchanged. It is imperative that the scope manufacturers understand the ergonomic areas of concern in the design of current endoscopes and incorporate ergonomic principles in future designs to optimize the interface between the instrument and the physician. In addition, it is as important for the physicians to be educated on ergonomic principles to minimize the risk for endoscopy-related injuries. This chapter reviews the design of current endoscopes and the ergonomic areas of concern. We review endoscope design changes that are needed to mitigate risk of injury during endoscopy, possible innovations that may improve endoscope ergonomics in the future, and barriers to implementation of any intervention that will address these shortcomings. © 2019 Elsevier Inc. All rights reserved.
1. Introduction Flexible GI endoscopy is a major diagnostic and therapeutic tool in clinical gastroenterology. Although endoscopy is not without risks, patients are not the only ones who experience complications. Gastrointestinal endoscopists are at a substantial risk of work-related musculoskeletal injury, with common reports of pain in the thumb, wrist, neck, and shoulder. Studies have reported the prevalence of musculoskeletal pain or injuries range from 37% up to 89% [1 4]. Women may be at increased risk for certain work-related cumulative trauma disorders [5], and females now make up 25%-35% of first-year gastroenterology fellows [6]. In addition, higher procedure volume is associated with a higher rate of endoscopy-related injury [7], and procedure volume continues to increase. In a 1994 survey of ASGE members assessing prevalence of endoscopist injury, the majority of endoscopists (78%) spent <40% of their work time performing endoscopy [8]. A repeat survey 20 years later found that the majority of endoscopists (61%) are now spending >40% of their work time The authors report no direct financial interests that might pose a conflict of interest in connection with the submitted manuscript. * Corresponding author. A. Khanicheh. E-mail address: [email protected] (A. Khanicheh). https://doi.org/10.1016/j.tgie.2019.05.003 1096-2883/© 2019 Elsevier Inc. All rights reserved.
performing endoscopy [7]. Injury and pain can lead to loss of productivity and can possibly shorten a career. Information regarding physician disability pertaining to gastroenterology is considered proprietary to insurance carriers, and thus there are limited available data regarding short-term and long-term disability from physician injuries related to endoscopy. Maneuvers specific to endoscopy such as adjusting tip angulation controls with the left hand, torqueing with the right hand, and standing for prolonged periods are known to contribute to musculoskeletal pain and injury and are potential causes of thumb/finger/hand pain/ injuries and back/neck pain/injuries [9]. Since the introduction of the endoscope, there have been important advances, particularly in image resolution and video technology. However, the basic features of the endoscope have not changed significantly. Static loading of the left upper extremity occurs when the control section is held for a prolonged time with the left hand. Repetitive, high left thumb forces and pinch/grip forces are required to manipulate the angulation knobs and control valves while stabilizing the control section. The right hand is used to apply force and torque to advance the endoscope through the lumen, at times through sharp angulations of the gastrointestinal tract. Adjusting scope techniques and neutralizing postures, along with adequate breaks, can help to reduce some of the risk of injuries [10], but there remain limited options for reducing forces
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encountered by the hands and wrists during procedures. There is an urgent need for more ergonomically designed endoscopes, and the need is greater for colonoscopy than for upper endoscopy considering the longer procedural times and the higher forces generated during the procedure. 2. Flexible endoscope design and components 2.1. Historical development of flexible endoscopes The first prototype of a flexible endoscope was developed by Hirschowitz, a gastroenterologist in fellowship training at the University of Michigan, and his colleagues in the physics department in early 1957 [11]. Hirschowitz collaborated with American Cystoscope Makers, Inc (ACMI) and the first fiber gastroscope was introduced to the market in early 1960 and quickly gained favor [12,13]. The range of endoscope refinements and improvements in the late 1960s and early 1970s was very extensive and included repositioning of lenses for wider field of vision, addition of channels for biopsy forceps, suction, air, or water, and 4-way controlled tip deflection. The expanding diagnostic capabilities of endoscopy were soon complemented by new therapeutic applications such as colon polypectomy, cannulation of the pancreatic duct, and removal of biliary stone in the 1970s. Conventional fiberoptic endoscope enabled examination of body cavities, but by only 1 person. It only had a single optical axis, meaning that the endoscopist could utilize only 1 eye, which was held close to the controls of the device. This was an uncomfortable position, and one which limited the teaching ability as well as the ability of the assistants to visualize the actual endoscopic procedure (and to subsequently provide actual “assistance” in the procedure) [14]. Different attachments to the eyepiece were developed to overcome this problem. For example, a prism was attached to the scope eyepiece with a fiber bundle to send the same visual information to another eyepiece, allowing 2 people to observe the same image. However, these attachments resulted in insufficient image quality for the operator, caused difficulty in operating the hand-held control unit, and increased the
risk of scope dislodgement during complex maneuvers. Video cameras were attached directly to the eyepiece lens and the images were displayed on a large television monitor. Although popular with endoscopists, it caused strain on the physician’s left hand, because of its size and attachment to the end of the control body and eyepiece. Progress in electronics and the introduction of charge-coupled device technology and digital endoscopy changed the way in which diagnostic and therapeutic endoscopic procedures were performed. The first video colonoscope was introduced in 1983 by Welch Allyn [15]. The endoscopist could now view an enlarged image with both eyes from a convenient distance and simultaneously record it [16]. Furthermore, digital signals permitted image enhancement, noise filtering, and video transmission and recording. Equally as important, the endoscopist could now stand upright and use both hands to operate in a coordinated fashion with assistants and trainees viewing the same image simultaneously [17]. 2.2. Basic components of modern flexible endoscopes A flexible endoscope is a compact device that is consists of 4 major structural components (Figure 1):
Control body Insertion tube Bending section/distal end Light guide connector
These major components are interconnected via 3 major systems that combine to give the endoscope its breadth of functionality: Mechanical system: such as the angulation system that allows the distal tip to be deflected in different directions to visualize the target site Plumbing system: such as water, can be directed to the target site for irrigation, and suction can be activated to remove excess fluid, air, or surgical debruises
Fig. 1. Basic components of flexible endoscopes.
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Illumination system: carry light to illuminate the interior of the target site and bring the image back to the video processor for display on a video monitor
The control body houses the control knobs that deflect the distal tip via wires attached to the bending section, and includes separate buttons for suction, air or water insufflation, and image capture. Within the control body, the plumbing system has outlets to control air/water and provide suction. Also, there is an entry port for the working channel, usually referred to as the biopsy port, for which different instruments can be introduced to allow therapeutic procedures such as biopsy, polypectomy, ablation, etc. The insertion tube contains channels for suction (working channel), air and water irrigation, and depending on the scope type, an additional tube for a forward water jet. Four angulation control wires run the length of the insertion tube. The very fine electrical wires that connect the chargecoupled device or complementary metal-oxide semiconductor image sensor at the distal tip of the endoscope to the video processor also travel through the insertion tube. The mechanical characteristics of insertion tubes are an important specification of the instrument which can determine the speed and ease with which the endoscopist can insert the instrument. For easy insertion, the instrument must be capable of accurately transmitting torque. Endoscope manufacturers have put significant effort into refining the construction of the insertion tube and selecting appropriate materials to optimize torque transmission. The deflectable portion of the insertion tube is referred to as the bending section, and is constructed quite differently from the rest of the insertion tube. It is composed of a series of metal rings with a linkage mechanism that allows the bending section to curl in any direction controlled by 4 angulation wires. A lightguide connector attaches the endoscope to the endoscopy tower, which commonly contains an image processor, a 100-300 W whitelight source with electrical power supply, air or CO2 source, and water. The video-image endoscope is a technologically advanced and complex clinical tool and the complexity of flexible endoscopes is often not appreciated or even realized by healthcare professionals using these tools or manipulating them. Image quality and illumination characteristics have been advanced extensively in the last few decades and the technology of video endoscopy has matured. It is very difficult to identify any single design criterion as the deciding factor in selecting the best videoscope for a particular clinical application. However, there remains a critical need for ergonomic considerations in the design of modern endoscopes. Endoscopic ergonomics requires more attention from scope designers and manufacturers, and more awareness by the endoscopists. 3. Applying ergonomic principle to endoscope design Although there have been substantial advances in endoscopic imaging technology as described earlier, the basic shape and layout of the instrument are relatively unchanged since the endoscope was first introduced. The instrument is designed to be held and operated by the endoscopist’s left hand. Some physicians use their index finger to alternately control the suction and air/water valves, while the rest of the left-hand fingers grip the instrument. Others use the index finger for the suction valve, the middle finger for the air/water valve, and the final 2 fingers to grip the instrument. The up/down angulation knob is manipulated by the left thumb. The left/right angulation knob is controlled either by the left thumb and first 2 fingers of the left hand or, alternatively, by the right hand. The endoscopist’s right hand is primarily used to control the insertion tube, pushing, torqueing, and withdrawing as necessary. When designing medical devices, special considerations are made so that the instrument is designed for use in a neutral posture since the physician is capable of producing his or her highest amount of
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force when a joint is in its neutral posture. As the joint moves away from the neutral posture, the amount of force the muscles can produce decreases because some of the muscle fibers are either contracted or elongated [18 20]. However, in endoscopic procedures, especially colonoscopy procedures, awkward postures are frequent and high forces are required while in these awkward postures. Main ergonomic stressors during colonoscopy can be summarized as: High and sustained forces: High levels of force and sustaining those levels of force overtime are identified sources of muscle strain, fatigue, discomfort, and are contributors to musculoskeletal disorders. For example, high and prolonged force to grip the colonoscope handle with the left hand, moderate force to manipulate the angulation controls with the left thumb, prolonged gripping and torqueing of the insertion tube with the right hand are among these contributors to pain and injury. Extreme postures: Extreme postures exist when the fingers, hand, wrist, arm, back, or neck are forced into extreme angles. These can result in fatigue, discomfort, and can contribute to musculoskeletal disorders. Any deviation from neutral posture reduces the level of force that can be delivered by the physician. Physicians may be forced into extreme postures when hyperextending the left thumb to manipulate the dials or the extreme postures on fingers, hands, and wrists during manipulation of the angulation controls and valves. Simultaneous actions: Simultaneous actions, where the physician uses the same hand to activate several controls at once as well as hold the endoscope body securely, make the interaction with the instrument difficult. To grasp the scope effectively, endoscopists use both the thumb and the opposing fingers in a power grasp. While they are grasping and stabilizing the control section, they must also use the thumb to manipulate the control knob positions, the index finger to activate suction and the middle finger to either cover the air valve or activate it. This results in extreme postures on the body, as well as reduced ability to administer force. Improper tool size: Improper tool size creates difficulties for physicians to reach and activate controls. For example, physicians with small hands (as determined by short hand length) struggle to reach the left/right control knob and have more difficulty rotating either control knob through the needed angular displacement. This results in more extreme postures as the physician strains to reach or complete the action, while still requiring force application at those extreme postures. Figure 2 demonstrates the aforementioned stressors. The physician needs to utilize her second hand to reach the left/right knob, while simultaneously holding the insertion tube between fingers. At the same time, the physician must utilize her body to support the weight of the endoscope, which results in a prolonged leaning posture.
Fig. 2. Simultaneous actions, extreme postures, and sustained forces: the physician utilizes the second hand to reach left/right knob and utilizes body to support the scope weight.
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As mentioned above, hand size is an important factor in being able to easily use the current endoscope devices, which have always been “one-size-fits-all.” The number, type, and placement of controls on the body of the endoscope and the body dimensions itself can be problematic for people with hand sizes that do not “fit” the scope. The critical hand-tool interactions for which hand size, specifically reach, matters includes the following:
Rotation of left/right control knob Rotation of up/down control knob Depressing the suction valve control Depressing, covering, and removing cover from the air/water feed valve Depressing any of the programmable activity buttons Other hand-tool interactions that usually require 2 hands because of difficulty (force too high for 1 hand, unable to reach without 2 hands, very fine manipulation required, etc.): Rotation of left/right locking knob Rotation of up/down locking knob Insertion, activation, removal of any tool (such as forceps or snare) through the instrument channel inlet To optimize the ergonomics of the current endoscopes, especially colonoscopes, we recommend the following considerations for the design of any new instruments: Reduce static grip force required of the left hand by providing scope support and/or reducing the weight of the scope. Reduce pinch force required of the right hand by reducing the torque required to manipulate the insertion tube. Reduce extreme postures of the right hand by providing support for the insertion tube and holing the insertion tube in place. Reduce extreme postures of the left hand by optimizing the tool size and reducing the distance required to reach the left/right knob for small to mid-size single hand users. Reduce extreme postures of the left hand by optimizing the tool size and reducing the distance required to reach the up/down and left/right break knobs. Reduce extreme postures of the left hand by reducing the rotational distance required for up/down and left/right knob for the same tip deflection. Reduce sustained forces of the left hand by reducing the force required to rotate the up/down and left/right knob.
4. Endoscope of the future The modern video colonoscope is a result of more than 3 decades of refinements in solid-state imaging technology and mechanical design. However, the basic components and controls of the endoscope have not changed from its inception. Elimination of the eyepiece found on fiberoptic instruments and using this space for 3-4 switches to control video processor functions (eg, image freeze, image capture, etc.) is the most revolutionary change which has been made over the last 5 decades. Main usability problems are related to advance and control of the proximal end of the flexible endoscope in the digestive tract. A long-term solution is to redesign the control section and create a device that does not resemble the endoscope that we use today and reduce the endoscopist’s injury risk through use of better ergonomic principles. Currently, a variety of devices of varying practicality are under investigation and this section describes a summary of future possibilities.
4.1. Reducing gravitational load The concept of a mechanical device to hold some or all weight of the endoscope was first published in 1974 [21]. Since then, a number of products with different designs have been described [22 24]. The goal of these devices is to eliminate or reduce the static load of the endoscope on the left hand encountered during procedures. For example, the ergonomic evaluation of an endoscope support stand (PENTAX Medical, HOYA Corporation, Japan) has been promising to show reduced muscle activity in both left hand and right hand. The reduced muscle activity on the left is likely due to reduced time spent holding the endoscope control section. The reduced muscle activity on the right side may be due to a decreased need for torque to manipulate the insertion tube during the procedures, since the dials on the endoscope control section are more easily accessible to physicians with smaller hands when it is on the scope stand [24]. However, further studies are required to show the traction of these devices by physicians, primarily because these devices cause limited mobility. Also, as will be discussed in the following section, physician’s technique, disinfection, and cost are important criteria for the acceptance of these instruments. 4.2. Novel control mechanisms and propulsion systems As described earlier, high forces associated with the manipulation of the angulation controls with the left hand and torqueing with the right hand on the conventional endoscopes are 2 key exposures that contribute to the physician’s risk of pain and hand injury during endoscopy. The rotation of the knobs on the control body pulls the angulation wires and causes the distal end deflection via a cable linkage. Therefore, the options for adjusting and altering the force and rotational distance required at the knobs to create the deflection at the distal end through purely mechanical solutions are limited. The length (9 m) of the GI tract and the variable diameter of the lumen presents challenges for delivery of the scope’s flexible shaft through body cavities such as the colon and small intestine. Therefore, some limitations are inherited with manual insertion (torqueing, pushing, pulling). A lot of research has been done in the last 2 decades to utilize different principles like earthworm [25,26], peristaltic locomotion [27,28], shape retention [29], and other nonconventional mechanisms [30 32] in advancing the scope shaft inside the colon. Skill-independent, self-propelling, and self-navigating scopes can result in reducing the need for the torque with the right hand. Also, these unconventional locomotion principles can allow for the redesign of the endoscope handle and for reducing the load on the left hand. A few examples of such nonconventional colonoscopy products are described below. This section is not an endorsement of any particular product. Rather, a hope that it stimulates the design of nonconventional endoscopes with ergonomic principle considerations in the future products. Invendoscope (Invendo Medical GmbH, Kissing, Germany): This system has a fully detachable endoscope handle with joystick style control deck (Figure 3). It aims to be a lightweight, single use colonoscope that addresses the medical risk of cross contamination from improperly sterilized endoscopes. The Invendoscope has a hydraulically articulated tip for navigation and retrograde viewing, using electromechanical assistance to transmit energy to the shaft of the endoscope for tip deflection as opposed to Bowden wires and pure mechanical force transmission. Such assistive technologies and joystick base handheld control plate have the potential to decrease injuries by decreased load on the gastroenterologist’s left hand in comparison to conventional endoscopes. However, further studies are required to understand the effect of a joystick handle endoscope on the carpal tunnel and associated nerves since it is the most common injury among gamers. The earlier version of the product (SC20) was based on inverted sleeve principle for propulsion, different than
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individual segments that can be programmed to change their shape. As the lead segment makes its way deeper into the colon, the remaining segments will automatically change their shape to follow the path that has been defined by the lead segment. Each of the 16 segments has 2° of articulation and is actuated by tendons. The actuators for the tendons lie in a separate external main control unit, not inside the scope. While passing the colon, a 3-dimensional map is created real time. The system reached clinical trials [33]; however, the company halted efforts on the NeoGuide colonoscope in late 2007. 4.3. Controlled capsules
Fig. 3. The Invendoscope colonoscope system (Photo courtesy of Invendo).
conventional endoscopes that require manual manipulation with respect to advancing and retracting the endoscope in the colon. As we will discuss in the next section, although this principle of operation reduced the need for torque and high forces by right hand, it involves changes in colonoscopy technique which is not popular with physicians and was replaced by manual insertion in the newer version of the device. Aer-O-Scope (GI View Ltd, Israel): The Aer-O-Scope is another disposable, miniaturized, and joystick control nonconventional endoscope, incorporating a pneumatic self-propelling mechanism and a unique omni-directional viewing system (Figure 4). The pneumatic self-propulsion mechanism uses balloons and low pressure CO2 gas for self-propelled intubation. The scope is propelled by pressurizing the colon with low pressure CO2 behind the scope. In order to cause the scope to glide gently in the changing colon environment, the information from the sensors is used to control the pressure, balloon size, and shape in real time. In addition to the novel locomotion in the colon, the Aer-O-Scope utilizes a so-called “omnidirectional” camera, which offers 360° field of view around the scope in the horizontal plane of the sensor. According to GI View, it potentially eliminates the need for continuously manipulating the tip, as is currently done in contemporary colonoscopy. The joystick is at the core of the work station, enabling control of navigation, insufflation, irrigation, and suction. Currently, Aer-O-Scope is not available for clinical use in the United States. Similar to the self-propelled version of Invendoscope, the instrument reduces the need for torque with the right hand and high load tip deflection. However, further studies are required to understand the effect of the joystick handle endoscope and physician’s acceptance of this new scoping technique. NeoGuide System (a company based in San Jose, California, that was acquired in 2009 by Intuitive Surgical of Sunnyvale, California): The NeoGuide endoscopy system consists of 16 computer-controlled
Wireless capsules for endoscopy were introduced in 2000 as a result of advances in miniaturization and efficiency of semiconductor technology. Today they are the gold standard for diagnosis of suspected diseases of the small intestine, since the majority of the small intestine is out of reach of the conventional endoscopes. However, capsules have not yet replaced traditional endoscopy because (1) their diagnostic accuracy is not yet equivalent to conventional scopes due to passive locomotion and not being able to visualize the entire surface area; (2) they are currently more costly than traditional endoscopes, which can be reused many times; and (3) they are not yet able to interact with tissue to collect biopsy samples or deliver therapy. Numerous novel designs are currently under development to address these limitations and endow wireless capsule endoscopes with advanced capabilities [34 43]. Magnetically controlled wireless capsules [35,36], tethered colonic capsules [33], biological-inspired actuated capsules [38 40], and on-board actuated capsules [41,42] are among these. Biopsy sampling and therapy delivery remain challenging requirements for capsule technology. If these limitations are addressed, capsules could replace traditional endoscopy and ergonomic shortcomings of endoscopes will no longer be relevant. However, at present these devices only provide diagnostic capabilities. In summary, we can place any new concept and instrument that addresses the ergonomics needs of current endoscopes in 1 of the 4 categories based on technology (current vs new) and physician’s interaction (current vs new):
Current technology/current hand-tool interaction Current technology/new hand-tool interaction New technology/current hand-tool interaction New technology/new hand-tool interaction
For example, any conventional endoscopes with lighter weight or less required force to rotate the angulation knobs will be in the current technology/current hand-tool interaction category. Self-propelling and self-navigating endoscopes will be in the category of new technology/ new hand-tool interaction. As mentioned earlier, current hand-tool interaction has inherited ergonomic shortcomings; therefore, any new solution with the current hand-tool interaction will have incremental ergonomic improvements. To fully address the ergonomic shortcomings of current endoscopes, it will be inevitable that new interaction with the endoscope will be required. However, it is worth mentioning that any device with new interaction (regardless of current or new technology) will require physician’s training and will have an associated learning curve. The easier and more intuitive the interaction with the instrument, the shorter the learning curve, which will result in an increased likelihood of acceptance of a new concept. 5. Barriers in endoscope redesign and modification 5.1. Physician’s technique and muscle memory
Fig. 4. The Aer-O-Scope colonoscope system (Photo courtesy of GI View).
When learning to play an instrument or perform a particular pose in yoga class, repetition and practice are important in order to succeed and ultimately to improve. Athletes train their muscles to remember
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particular movements so that when in competition, they can perform at very high levels without even giving a thought to mechanics. In medicine, extensive hands on experience are gained and muscle memory is developed during the years of training in our current system. The goal of achieving unconscious competence [44], practicing a task until it is nearly automatic, allows us to devote more of our brainpower to other more complex tasks. Practicing skills allow physicians to not only improve at a particular movement but more importantly help them respond to a particular situation quickly, calmly, and automatically. Therefore, once a physician has developed muscle memory and the brain is trained to use a particular medical instrument such an endoscope over years of practice, it is very difficult to switch or relearn a new instrument or a technique (Figure 5). The physicians will be acutely aware of their conscious incompetence with this new instrument or technique, and will be less likely to favor the new technique over a technique for which they have already achieved unconscious competence. Especially if an endoscopist does not have any injury due to scoping, the physician may be unwilling to relearn endoscopy with a new technique that, at least initially, prolongs procedure time as he/ she goes through the learning curve. The closer the hand-tool interaction of the new system is to the current system, the easier for the physician to utilize the new platform with a minimum learning curve. As discussed above, it is unlikely that incremental modifications to current endoscopes will result in an endoscope design that can address all ergonomic areas of concerns. Thus, there is a fine balance that must be achieved when introducing new techniques or technologies in order to gain widespread physician acceptance. A promising and potentially effective way for acceptance of a new scope will be to train the gastroenterology fellows on the new systems. However, it is recognized that attending gastroenterologists are the ones who are teaching the fellows. We have found that physicians with hand injuries are more willing to take the time to learn a new ergonomic endoscope even if it is a nonconventional scope since they are more aware of musculoskeletal disorders as a result of scoping. Therefore, it is important for the physicians to be educated and informed of the endoscopy-related injuries. It is also worth mentioning that endoscope manufacturers need to work closely with endoscopists for training of new instruments especially nonconventional scopes. 5.2. Cleaning and disinfection Although high standards for processing and disinfection of endoscopes have been established, there are still issues related to bacterial outbreaks. The working channel and distal end elevators may be especially challenging. In addition, reusable accessories that accommodate the utilization of endoscopes more ergonomically such as reducing gravitational load, devices that were described earlier, will
need to meet the reprocessing and cleaning requirements. This is not an issue for disposable endoscope solutions. Although single use solutions or simple reprocessing solutions for reusable instruments are necessary, keeping the cost low is an inherent technical challenge for the designers and manufacturers. 5.3. Financial considerations For standard endoscopy procedures such as colonoscopy, current procedural terminology codes are used, even if nonconventional endoscopes or specialty instruments are used. Therefore, the new innovative ergonomic endoscopes or supporting devices cannot be much more expensive than conventional scopes to be adapted widely. This puts pressure on the scope designers and manufacturers to follow the approaches and solutions that are cost effective. Any new technique and instrument will require a learning curve and training. This will be a challenge in the current system as typical gastroenterologists perform a high volume of endoscopic procedures and any new technique that requires retraining and creating new muscle memory will also require time and practice, which initially will prolong procedures. From a hospital personnel standpoint, musculoskeletal injuries can lead to work load reduction, missed days of work, reduction of activities outside of work, and long-term disabilities. Therefore, when evaluating cost and financial aspects of time associated with learning and using a new instrument, the physician’s health and loss of productivity must be considered as well. 6. Summary The design of conventional endoscopes inherently suffers from ergonomic principle considerations and instrument design changes are required to improve the interactions of the endoscopists with the instrument and reduce the prevalence of musculoskeletal injuries. Technological innovations such as ergonomically designed endoscope handles, self-propelled endoscopes, and accessories that reduce high and sustained forces, repetitive movements, and awkward postures from endoscopists may reduce the inherent physical stresses of endoscopy and the risk of biomechanical injuries. It is important to realize that training with current scopes, interaction with current instruments over time, and repetition of tasks using the scopes, result in physician’s proficiency in technique and development of a muscle memory to perform endoscopy, or unconscious competence. This creates challenges in encouraging endoscopists without injuries to spend time relearning a new instrument and technique, during which time the physician will be aware of their conscious incompetence. In addition, there will be a financial burden on the system as the physicians retrain and require more time to perform the endoscopy procedure. However, as discussed earlier, physician’s health and loss of productivity due to injuries must be considered when cost and financials are being evaluated. References
Fig. 5. Stages of competence, current scopes, and new technology.
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[7] Ridtitid W, Coté GA, Leung W, Buschbacher R, Lynch S, Fogel EL, et al. Prevalence and risk factors for musculoskeletal injuries related to endoscopy. Gastrointest Endosc 2015;81:294–302. e4. [8] Buschbacher R. Overuse syndromes among endoscopists. Endoscopy 1994; 26:539–44. [9] Hansel SL, Crowell MD, Pardi DS, Bouras EP, DiBaise JK. Prevalence and impact of musculoskeletal injury among endoscopists: a controlled pilot study. J Clin Gastroenterol 2009;43:399–404. [10] Pedrosa MC, Farraye FA, Shergill AK, Banerjee S, Desilets D, Diehl DL, et al. Minimizing occupational hazards in endoscopy: personal protective equipment, radiation safety, and ergonomics. Gastrointest Endosc 2010;72:227–35. [11] Hirschowitz BI, Peters CW, Curtiss LE. Preliminary report on a long fiberscope for examination of stomach and duodenum. Med Bull 1957;23:178–80. [12] Weisinger BB, Cramer AB, Zacharis LC. Comparative accuracy of the fiberscope and standard gastroscope in the diagnosis of gastric lesions; preliminary report. Gastroenterology 1963;44:858A. [13] Cohen NN, Hughes RW, Manfredo HE. Experiences with 1000 fibergastroscopic examinations of the stomach. Am J Dig Dis 1966;11:943–50. [14] Marks JM, Dunkin BJ. Principles of flexible endoscopy for surgeons. Springer; 2013 ISBN 978-1-4614-6329-0. [15] Sivak MV. Colonoscopy with videoendoscopy: preliminary experience. Gastrointest Endosc 1984;30:1–5. [16] Litynski GS. Endoscopic surgery: the history, the pioneers. World J Surg 1999; 23:745–53. [17] Berci G, Paz-Partlow M. Electronic imaging in endoscopy. Surg Endosc 1988; 2:227–33. [18] Clarke HH. Muscular strength and endurance in man. Englewood Cliffs, NJ: Prentice Hall; 1966. [19] Kumar S. Muscle strength. Boca Raton, FL: CRC Press, LLC; 2004. p. 27. [20] Moore SM, Torma-Krajewski J, Steiner LJ. Practical demonstrations of ergonomic principles. Pittsburgh, PA: U. S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health; 2011. p. 1–57. [21] Nivatvongs S, Goldberg SM. Holder for the fiberoptic colonoscope. Dis Colon Rectum 1974;17:273–4. [22] Rattan J, Rozen P. A new colonoscope holder. Dis Colon Rectum 1987;30:639–40. [23] Marks G. A new technique of hand reversal using a harness-type endoscope holder for twin-knob colonoscopy and flexible fiberoptic sigmoidoscopy. Dis Colon Rectum 1981;24:567–8. [24] Shergill AK, Barr A, Harris-Adamson C. Ergonomic evaluation of an endoscope support stand during simulated colonoscopies. Gastrointest Endosc 2018;87:6S. AB506. [25] Kim B, Jeong Y, Lim HY, Kim TS, Park JO, Dario P, et al. Smart colonoscope system. In: Proceedings of the 2002 IEEE/RSJ. International conference on intelligent robots and systems; 2002. [26] Wang K, Wang Z, Zhou Y, Yan G. Squirm robot with full bellow skin for colonoscopy. In: 2010 IEEE International Conference on Robotics and Biomimetics; 2010; 53–7.
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[27] Glozman D, Hassidov N, Senesh M, Shoham M. A self-propelled inflatable earthworm-like endoscope actuated by single supply line. IEEE Trans Biomed Eng 2010;57:1264–72. [28] Mangan EV, Kingsley DA, Quinn RD, Chiel HJ. Development of a peristaltic endoscope. In: International Conference on Robotics and Automation; 2002. [29] Loeve A, Breedveld P. Dankelman, scopes too flexible...and too stiff. IEEE Pulse 2010;1:26–41. [30] Tumino E, Sacco R, Bertini M, Bertoni M, Parisi G, Capria A. Endotics system vs. colonoscopy for the detection of polyps. World J Gastroenterol 2010;16:5452–6. [31] Rosch T, Adler A, Pohl H, Wettschureck E, Koch M, Wiedenmann B, et al. A motordriven single-use colonoscope controlled with a hand-held device: a feasibility study in volunteers. Gastrointest Endosc 2010;67:1139–46. [32] Shike M, Fireman Z, Eliakim R, Segol O, Sloyer A, Cohen LB, et al. Sightline ColonoSight system for a disposable, power-assisted, non-fiber-optic colonoscopy (with video). Gastrointest Endosc 2008;68:701–10. [33] Eickhoff A, van Dam J, Jakobs R, Kudis V, Hartmann D, Damian U, et al. Computerassisted colonoscopy (the NeoGuide Endoscopy System): results of the first human clinical trial (“PACE study”). Am J Gastroenterol 2007;102:261–6. [34] Valdastri P, Simi M, Webster 3rd RJ. Advanced technologies for gastrointestinal endoscopy. Annu Rev Biomed Eng 2012;14:397–429. [35] Keller J, Fibbe C, Volke F, Gerber J, Mosse AC, Reimann-Zawadzki M, et al. Inspection of the human stomach using remote-controlled capsule endoscopy: a feasibility study in healthy volunteers (with videos). Gastrointest Endosc 2011;73:22–8. [36] Morita E, Ohtsuka N, Shindo Y, Nouda S, Kuramoto T, Inoue T, et al. In vivo trial of a driving system for a self-propelling capsule endoscope using a magnetic field (with video). Gastrointest Endosc 2010;72:836–40. [37] Sliker LJ, Kern MD, Schoen JA, Rentschler ME. Surgical evaluation of a novel tethered robotic capsule endoscope using micro-patterned treads. Surg Endosc 2012;26:2862–9. [38] Kwon J, Park S, Park J, Kim B. Evaluation of the critical stroke of an earthworm-like robot for capsule endoscopes. Proc Inst Mech Eng 2007;221:397–405. [39] Feng Y, Li W, Li M, Sun L. Structure optimization of the endoscopic robot ciliary leg based on dimensional analysis. In: IEEE International Conference on Robotics and Biomimmetics, Piscataway, NJ. IEEE; 2007:109–14. [40] Kim HM, Yang S, Kim J, Park S, Cho JH, Park JY, et al. Active locomotion of a paddling-based capsule endoscope in an in vitro and in vivo experiment (with videos). Gastrointest Endosc 2010;72:381–7. [41] Tortora G, Valdastri P, Susilo E, Menciassi A, Dario P, Rieber F, et al. Propellerbased wireless device for active capsular endoscopy in the gastric district. Minim Invasive Ther Allied Technol 2009;18:280–90. [42] Valdastri P, Ciuti G, Verbeni A, Menciassi A, Dario P, Arezzo A, et al. Magnetic air capsule robotic system: proof of concept of a novel approach for painless colonoscopy. Surg Endosc 2012;26:1238–46. [43] Park S, Koo K, Bang SM, Park JY, Song SY, Cho DD. A novel microactuator for microbiopsy in capsular endoscopes. J Micromech Microeng 2008;18:025032. [44] Burch N. Four stages of learning. Gordon Training International 1970 Available from: URL: http://www.gordontraining.com/free-workplace-articles/learning-anew-skill-is-easier-said-than-done/.
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Techniques in Gastrointestinal Endoscopy journal homepage: www.techgiendoscopy.com/locate/tgie
Endoscope design for the future Azadeh Khanicheh, PhDa,*, Amandeep K. Shergill, MD, MSb a b
EnVision Endoscopy, 15 Fairfax St, # 2, Somerville, Massachusetts 02144 San Francisco VA Medical Center, University of California, San Francisco, San Francisco, California
A R T I C L E
I N F O
Article history: Received 31 January 2019 Revised 22 April 2019 Accepted 29 May 2019 Keywords: Ergonomics Flexible endoscope Design requirements Scope interaction
A B S T R A C T
A preponderance of evidence, primarily from surveys, has shown that gastroenterologists suffer from overuse injuries and pain of hand/fingers, wrist, forearm, shoulder, and back due to awkward postures, high forces, and repetitive movements during endoscopy. Although flexible endoscopes are brilliantly designed compact instruments that include light and image guides, irrigation channels, suction channel, biopsy channels and are the result of many technological advancements and iterations in the last 5 decades, not much has changed in their basic functions, layout, ergonomic design, and usability. The required hand-tool interaction in order to maneuver the endoscope inside the intestinal lumen, such as stabilizing the control section while manipulating dials with the left hand while simultaneously torqueing, pushing, and/or pulling the insertion tube with the right hand, are still unchanged. It is imperative that the scope manufacturers understand the ergonomic areas of concern in the design of current endoscopes and incorporate ergonomic principles in future designs to optimize the interface between the instrument and the physician. In addition, it is as important for the physicians to be educated on ergonomic principles to minimize the risk for endoscopy-related injuries. This chapter reviews the design of current endoscopes and the ergonomic areas of concern. We review endoscope design changes that are needed to mitigate risk of injury during endoscopy, possible innovations that may improve endoscope ergonomics in the future, and barriers to implementation of any intervention that will address these shortcomings. © 2019 Elsevier Inc. All rights reserved.
1. Introduction Flexible GI endoscopy is a major diagnostic and therapeutic tool in clinical gastroenterology. Although endoscopy is not without risks, patients are not the only ones who experience complications. Gastrointestinal endoscopists are at a substantial risk of work-related musculoskeletal injury, with common reports of pain in the thumb, wrist, neck, and shoulder. Studies have reported the prevalence of musculoskeletal pain or injuries range from 37% up to 89% [1 4]. Women may be at increased risk for certain work-related cumulative trauma disorders [5], and females now make up 25%-35% of first-year gastroenterology fellows [6]. In addition, higher procedure volume is associated with a higher rate of endoscopy-related injury [7], and procedure volume continues to increase. In a 1994 survey of ASGE members assessing prevalence of endoscopist injury, the majority of endoscopists (78%) spent <40% of their work time performing endoscopy [8]. A repeat survey 20 years later found that the majority of endoscopists (61%) are now spending >40% of their work time The authors report no direct financial interests that might pose a conflict of interest in connection with the submitted manuscript. * Corresponding author. A. Khanicheh. E-mail address: [email protected] (A. Khanicheh). https://doi.org/10.1016/j.tgie.2019.05.003 1096-2883/© 2019 Elsevier Inc. All rights reserved.
performing endoscopy [7]. Injury and pain can lead to loss of productivity and can possibly shorten a career. Information regarding physician disability pertaining to gastroenterology is considered proprietary to insurance carriers, and thus there are limited available data regarding short-term and long-term disability from physician injuries related to endoscopy. Maneuvers specific to endoscopy such as adjusting tip angulation controls with the left hand, torqueing with the right hand, and standing for prolonged periods are known to contribute to musculoskeletal pain and injury and are potential causes of thumb/finger/hand pain/ injuries and back/neck pain/injuries [9]. Since the introduction of the endoscope, there have been important advances, particularly in image resolution and video technology. However, the basic features of the endoscope have not changed significantly. Static loading of the left upper extremity occurs when the control section is held for a prolonged time with the left hand. Repetitive, high left thumb forces and pinch/grip forces are required to manipulate the angulation knobs and control valves while stabilizing the control section. The right hand is used to apply force and torque to advance the endoscope through the lumen, at times through sharp angulations of the gastrointestinal tract. Adjusting scope techniques and neutralizing postures, along with adequate breaks, can help to reduce some of the risk of injuries [10], but there remain limited options for reducing forces
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encountered by the hands and wrists during procedures. There is an urgent need for more ergonomically designed endoscopes, and the need is greater for colonoscopy than for upper endoscopy considering the longer procedural times and the higher forces generated during the procedure. 2. Flexible endoscope design and components 2.1. Historical development of flexible endoscopes The first prototype of a flexible endoscope was developed by Hirschowitz, a gastroenterologist in fellowship training at the University of Michigan, and his colleagues in the physics department in early 1957 [11]. Hirschowitz collaborated with American Cystoscope Makers, Inc (ACMI) and the first fiber gastroscope was introduced to the market in early 1960 and quickly gained favor [12,13]. The range of endoscope refinements and improvements in the late 1960s and early 1970s was very extensive and included repositioning of lenses for wider field of vision, addition of channels for biopsy forceps, suction, air, or water, and 4-way controlled tip deflection. The expanding diagnostic capabilities of endoscopy were soon complemented by new therapeutic applications such as colon polypectomy, cannulation of the pancreatic duct, and removal of biliary stone in the 1970s. Conventional fiberoptic endoscope enabled examination of body cavities, but by only 1 person. It only had a single optical axis, meaning that the endoscopist could utilize only 1 eye, which was held close to the controls of the device. This was an uncomfortable position, and one which limited the teaching ability as well as the ability of the assistants to visualize the actual endoscopic procedure (and to subsequently provide actual “assistance” in the procedure) [14]. Different attachments to the eyepiece were developed to overcome this problem. For example, a prism was attached to the scope eyepiece with a fiber bundle to send the same visual information to another eyepiece, allowing 2 people to observe the same image. However, these attachments resulted in insufficient image quality for the operator, caused difficulty in operating the hand-held control unit, and increased the
risk of scope dislodgement during complex maneuvers. Video cameras were attached directly to the eyepiece lens and the images were displayed on a large television monitor. Although popular with endoscopists, it caused strain on the physician’s left hand, because of its size and attachment to the end of the control body and eyepiece. Progress in electronics and the introduction of charge-coupled device technology and digital endoscopy changed the way in which diagnostic and therapeutic endoscopic procedures were performed. The first video colonoscope was introduced in 1983 by Welch Allyn [15]. The endoscopist could now view an enlarged image with both eyes from a convenient distance and simultaneously record it [16]. Furthermore, digital signals permitted image enhancement, noise filtering, and video transmission and recording. Equally as important, the endoscopist could now stand upright and use both hands to operate in a coordinated fashion with assistants and trainees viewing the same image simultaneously [17]. 2.2. Basic components of modern flexible endoscopes A flexible endoscope is a compact device that is consists of 4 major structural components (Figure 1):
Control body Insertion tube Bending section/distal end Light guide connector
These major components are interconnected via 3 major systems that combine to give the endoscope its breadth of functionality: Mechanical system: such as the angulation system that allows the distal tip to be deflected in different directions to visualize the target site Plumbing system: such as water, can be directed to the target site for irrigation, and suction can be activated to remove excess fluid, air, or surgical debruises
Fig. 1. Basic components of flexible endoscopes.
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Illumination system: carry light to illuminate the interior of the target site and bring the image back to the video processor for display on a video monitor
The control body houses the control knobs that deflect the distal tip via wires attached to the bending section, and includes separate buttons for suction, air or water insufflation, and image capture. Within the control body, the plumbing system has outlets to control air/water and provide suction. Also, there is an entry port for the working channel, usually referred to as the biopsy port, for which different instruments can be introduced to allow therapeutic procedures such as biopsy, polypectomy, ablation, etc. The insertion tube contains channels for suction (working channel), air and water irrigation, and depending on the scope type, an additional tube for a forward water jet. Four angulation control wires run the length of the insertion tube. The very fine electrical wires that connect the chargecoupled device or complementary metal-oxide semiconductor image sensor at the distal tip of the endoscope to the video processor also travel through the insertion tube. The mechanical characteristics of insertion tubes are an important specification of the instrument which can determine the speed and ease with which the endoscopist can insert the instrument. For easy insertion, the instrument must be capable of accurately transmitting torque. Endoscope manufacturers have put significant effort into refining the construction of the insertion tube and selecting appropriate materials to optimize torque transmission. The deflectable portion of the insertion tube is referred to as the bending section, and is constructed quite differently from the rest of the insertion tube. It is composed of a series of metal rings with a linkage mechanism that allows the bending section to curl in any direction controlled by 4 angulation wires. A lightguide connector attaches the endoscope to the endoscopy tower, which commonly contains an image processor, a 100-300 W whitelight source with electrical power supply, air or CO2 source, and water. The video-image endoscope is a technologically advanced and complex clinical tool and the complexity of flexible endoscopes is often not appreciated or even realized by healthcare professionals using these tools or manipulating them. Image quality and illumination characteristics have been advanced extensively in the last few decades and the technology of video endoscopy has matured. It is very difficult to identify any single design criterion as the deciding factor in selecting the best videoscope for a particular clinical application. However, there remains a critical need for ergonomic considerations in the design of modern endoscopes. Endoscopic ergonomics requires more attention from scope designers and manufacturers, and more awareness by the endoscopists. 3. Applying ergonomic principle to endoscope design Although there have been substantial advances in endoscopic imaging technology as described earlier, the basic shape and layout of the instrument are relatively unchanged since the endoscope was first introduced. The instrument is designed to be held and operated by the endoscopist’s left hand. Some physicians use their index finger to alternately control the suction and air/water valves, while the rest of the left-hand fingers grip the instrument. Others use the index finger for the suction valve, the middle finger for the air/water valve, and the final 2 fingers to grip the instrument. The up/down angulation knob is manipulated by the left thumb. The left/right angulation knob is controlled either by the left thumb and first 2 fingers of the left hand or, alternatively, by the right hand. The endoscopist’s right hand is primarily used to control the insertion tube, pushing, torqueing, and withdrawing as necessary. When designing medical devices, special considerations are made so that the instrument is designed for use in a neutral posture since the physician is capable of producing his or her highest amount of
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force when a joint is in its neutral posture. As the joint moves away from the neutral posture, the amount of force the muscles can produce decreases because some of the muscle fibers are either contracted or elongated [18 20]. However, in endoscopic procedures, especially colonoscopy procedures, awkward postures are frequent and high forces are required while in these awkward postures. Main ergonomic stressors during colonoscopy can be summarized as: High and sustained forces: High levels of force and sustaining those levels of force overtime are identified sources of muscle strain, fatigue, discomfort, and are contributors to musculoskeletal disorders. For example, high and prolonged force to grip the colonoscope handle with the left hand, moderate force to manipulate the angulation controls with the left thumb, prolonged gripping and torqueing of the insertion tube with the right hand are among these contributors to pain and injury. Extreme postures: Extreme postures exist when the fingers, hand, wrist, arm, back, or neck are forced into extreme angles. These can result in fatigue, discomfort, and can contribute to musculoskeletal disorders. Any deviation from neutral posture reduces the level of force that can be delivered by the physician. Physicians may be forced into extreme postures when hyperextending the left thumb to manipulate the dials or the extreme postures on fingers, hands, and wrists during manipulation of the angulation controls and valves. Simultaneous actions: Simultaneous actions, where the physician uses the same hand to activate several controls at once as well as hold the endoscope body securely, make the interaction with the instrument difficult. To grasp the scope effectively, endoscopists use both the thumb and the opposing fingers in a power grasp. While they are grasping and stabilizing the control section, they must also use the thumb to manipulate the control knob positions, the index finger to activate suction and the middle finger to either cover the air valve or activate it. This results in extreme postures on the body, as well as reduced ability to administer force. Improper tool size: Improper tool size creates difficulties for physicians to reach and activate controls. For example, physicians with small hands (as determined by short hand length) struggle to reach the left/right control knob and have more difficulty rotating either control knob through the needed angular displacement. This results in more extreme postures as the physician strains to reach or complete the action, while still requiring force application at those extreme postures. Figure 2 demonstrates the aforementioned stressors. The physician needs to utilize her second hand to reach the left/right knob, while simultaneously holding the insertion tube between fingers. At the same time, the physician must utilize her body to support the weight of the endoscope, which results in a prolonged leaning posture.
Fig. 2. Simultaneous actions, extreme postures, and sustained forces: the physician utilizes the second hand to reach left/right knob and utilizes body to support the scope weight.
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As mentioned above, hand size is an important factor in being able to easily use the current endoscope devices, which have always been “one-size-fits-all.” The number, type, and placement of controls on the body of the endoscope and the body dimensions itself can be problematic for people with hand sizes that do not “fit” the scope. The critical hand-tool interactions for which hand size, specifically reach, matters includes the following:
Rotation of left/right control knob Rotation of up/down control knob Depressing the suction valve control Depressing, covering, and removing cover from the air/water feed valve Depressing any of the programmable activity buttons Other hand-tool interactions that usually require 2 hands because of difficulty (force too high for 1 hand, unable to reach without 2 hands, very fine manipulation required, etc.): Rotation of left/right locking knob Rotation of up/down locking knob Insertion, activation, removal of any tool (such as forceps or snare) through the instrument channel inlet To optimize the ergonomics of the current endoscopes, especially colonoscopes, we recommend the following considerations for the design of any new instruments: Reduce static grip force required of the left hand by providing scope support and/or reducing the weight of the scope. Reduce pinch force required of the right hand by reducing the torque required to manipulate the insertion tube. Reduce extreme postures of the right hand by providing support for the insertion tube and holing the insertion tube in place. Reduce extreme postures of the left hand by optimizing the tool size and reducing the distance required to reach the left/right knob for small to mid-size single hand users. Reduce extreme postures of the left hand by optimizing the tool size and reducing the distance required to reach the up/down and left/right break knobs. Reduce extreme postures of the left hand by reducing the rotational distance required for up/down and left/right knob for the same tip deflection. Reduce sustained forces of the left hand by reducing the force required to rotate the up/down and left/right knob.
4. Endoscope of the future The modern video colonoscope is a result of more than 3 decades of refinements in solid-state imaging technology and mechanical design. However, the basic components and controls of the endoscope have not changed from its inception. Elimination of the eyepiece found on fiberoptic instruments and using this space for 3-4 switches to control video processor functions (eg, image freeze, image capture, etc.) is the most revolutionary change which has been made over the last 5 decades. Main usability problems are related to advance and control of the proximal end of the flexible endoscope in the digestive tract. A long-term solution is to redesign the control section and create a device that does not resemble the endoscope that we use today and reduce the endoscopist’s injury risk through use of better ergonomic principles. Currently, a variety of devices of varying practicality are under investigation and this section describes a summary of future possibilities.
4.1. Reducing gravitational load The concept of a mechanical device to hold some or all weight of the endoscope was first published in 1974 [21]. Since then, a number of products with different designs have been described [22 24]. The goal of these devices is to eliminate or reduce the static load of the endoscope on the left hand encountered during procedures. For example, the ergonomic evaluation of an endoscope support stand (PENTAX Medical, HOYA Corporation, Japan) has been promising to show reduced muscle activity in both left hand and right hand. The reduced muscle activity on the left is likely due to reduced time spent holding the endoscope control section. The reduced muscle activity on the right side may be due to a decreased need for torque to manipulate the insertion tube during the procedures, since the dials on the endoscope control section are more easily accessible to physicians with smaller hands when it is on the scope stand [24]. However, further studies are required to show the traction of these devices by physicians, primarily because these devices cause limited mobility. Also, as will be discussed in the following section, physician’s technique, disinfection, and cost are important criteria for the acceptance of these instruments. 4.2. Novel control mechanisms and propulsion systems As described earlier, high forces associated with the manipulation of the angulation controls with the left hand and torqueing with the right hand on the conventional endoscopes are 2 key exposures that contribute to the physician’s risk of pain and hand injury during endoscopy. The rotation of the knobs on the control body pulls the angulation wires and causes the distal end deflection via a cable linkage. Therefore, the options for adjusting and altering the force and rotational distance required at the knobs to create the deflection at the distal end through purely mechanical solutions are limited. The length (9 m) of the GI tract and the variable diameter of the lumen presents challenges for delivery of the scope’s flexible shaft through body cavities such as the colon and small intestine. Therefore, some limitations are inherited with manual insertion (torqueing, pushing, pulling). A lot of research has been done in the last 2 decades to utilize different principles like earthworm [25,26], peristaltic locomotion [27,28], shape retention [29], and other nonconventional mechanisms [30 32] in advancing the scope shaft inside the colon. Skill-independent, self-propelling, and self-navigating scopes can result in reducing the need for the torque with the right hand. Also, these unconventional locomotion principles can allow for the redesign of the endoscope handle and for reducing the load on the left hand. A few examples of such nonconventional colonoscopy products are described below. This section is not an endorsement of any particular product. Rather, a hope that it stimulates the design of nonconventional endoscopes with ergonomic principle considerations in the future products. Invendoscope (Invendo Medical GmbH, Kissing, Germany): This system has a fully detachable endoscope handle with joystick style control deck (Figure 3). It aims to be a lightweight, single use colonoscope that addresses the medical risk of cross contamination from improperly sterilized endoscopes. The Invendoscope has a hydraulically articulated tip for navigation and retrograde viewing, using electromechanical assistance to transmit energy to the shaft of the endoscope for tip deflection as opposed to Bowden wires and pure mechanical force transmission. Such assistive technologies and joystick base handheld control plate have the potential to decrease injuries by decreased load on the gastroenterologist’s left hand in comparison to conventional endoscopes. However, further studies are required to understand the effect of a joystick handle endoscope on the carpal tunnel and associated nerves since it is the most common injury among gamers. The earlier version of the product (SC20) was based on inverted sleeve principle for propulsion, different than
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individual segments that can be programmed to change their shape. As the lead segment makes its way deeper into the colon, the remaining segments will automatically change their shape to follow the path that has been defined by the lead segment. Each of the 16 segments has 2° of articulation and is actuated by tendons. The actuators for the tendons lie in a separate external main control unit, not inside the scope. While passing the colon, a 3-dimensional map is created real time. The system reached clinical trials [33]; however, the company halted efforts on the NeoGuide colonoscope in late 2007. 4.3. Controlled capsules
Fig. 3. The Invendoscope colonoscope system (Photo courtesy of Invendo).
conventional endoscopes that require manual manipulation with respect to advancing and retracting the endoscope in the colon. As we will discuss in the next section, although this principle of operation reduced the need for torque and high forces by right hand, it involves changes in colonoscopy technique which is not popular with physicians and was replaced by manual insertion in the newer version of the device. Aer-O-Scope (GI View Ltd, Israel): The Aer-O-Scope is another disposable, miniaturized, and joystick control nonconventional endoscope, incorporating a pneumatic self-propelling mechanism and a unique omni-directional viewing system (Figure 4). The pneumatic self-propulsion mechanism uses balloons and low pressure CO2 gas for self-propelled intubation. The scope is propelled by pressurizing the colon with low pressure CO2 behind the scope. In order to cause the scope to glide gently in the changing colon environment, the information from the sensors is used to control the pressure, balloon size, and shape in real time. In addition to the novel locomotion in the colon, the Aer-O-Scope utilizes a so-called “omnidirectional” camera, which offers 360° field of view around the scope in the horizontal plane of the sensor. According to GI View, it potentially eliminates the need for continuously manipulating the tip, as is currently done in contemporary colonoscopy. The joystick is at the core of the work station, enabling control of navigation, insufflation, irrigation, and suction. Currently, Aer-O-Scope is not available for clinical use in the United States. Similar to the self-propelled version of Invendoscope, the instrument reduces the need for torque with the right hand and high load tip deflection. However, further studies are required to understand the effect of the joystick handle endoscope and physician’s acceptance of this new scoping technique. NeoGuide System (a company based in San Jose, California, that was acquired in 2009 by Intuitive Surgical of Sunnyvale, California): The NeoGuide endoscopy system consists of 16 computer-controlled
Wireless capsules for endoscopy were introduced in 2000 as a result of advances in miniaturization and efficiency of semiconductor technology. Today they are the gold standard for diagnosis of suspected diseases of the small intestine, since the majority of the small intestine is out of reach of the conventional endoscopes. However, capsules have not yet replaced traditional endoscopy because (1) their diagnostic accuracy is not yet equivalent to conventional scopes due to passive locomotion and not being able to visualize the entire surface area; (2) they are currently more costly than traditional endoscopes, which can be reused many times; and (3) they are not yet able to interact with tissue to collect biopsy samples or deliver therapy. Numerous novel designs are currently under development to address these limitations and endow wireless capsule endoscopes with advanced capabilities [34 43]. Magnetically controlled wireless capsules [35,36], tethered colonic capsules [33], biological-inspired actuated capsules [38 40], and on-board actuated capsules [41,42] are among these. Biopsy sampling and therapy delivery remain challenging requirements for capsule technology. If these limitations are addressed, capsules could replace traditional endoscopy and ergonomic shortcomings of endoscopes will no longer be relevant. However, at present these devices only provide diagnostic capabilities. In summary, we can place any new concept and instrument that addresses the ergonomics needs of current endoscopes in 1 of the 4 categories based on technology (current vs new) and physician’s interaction (current vs new):
Current technology/current hand-tool interaction Current technology/new hand-tool interaction New technology/current hand-tool interaction New technology/new hand-tool interaction
For example, any conventional endoscopes with lighter weight or less required force to rotate the angulation knobs will be in the current technology/current hand-tool interaction category. Self-propelling and self-navigating endoscopes will be in the category of new technology/ new hand-tool interaction. As mentioned earlier, current hand-tool interaction has inherited ergonomic shortcomings; therefore, any new solution with the current hand-tool interaction will have incremental ergonomic improvements. To fully address the ergonomic shortcomings of current endoscopes, it will be inevitable that new interaction with the endoscope will be required. However, it is worth mentioning that any device with new interaction (regardless of current or new technology) will require physician’s training and will have an associated learning curve. The easier and more intuitive the interaction with the instrument, the shorter the learning curve, which will result in an increased likelihood of acceptance of a new concept. 5. Barriers in endoscope redesign and modification 5.1. Physician’s technique and muscle memory
Fig. 4. The Aer-O-Scope colonoscope system (Photo courtesy of GI View).
When learning to play an instrument or perform a particular pose in yoga class, repetition and practice are important in order to succeed and ultimately to improve. Athletes train their muscles to remember
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particular movements so that when in competition, they can perform at very high levels without even giving a thought to mechanics. In medicine, extensive hands on experience are gained and muscle memory is developed during the years of training in our current system. The goal of achieving unconscious competence [44], practicing a task until it is nearly automatic, allows us to devote more of our brainpower to other more complex tasks. Practicing skills allow physicians to not only improve at a particular movement but more importantly help them respond to a particular situation quickly, calmly, and automatically. Therefore, once a physician has developed muscle memory and the brain is trained to use a particular medical instrument such an endoscope over years of practice, it is very difficult to switch or relearn a new instrument or a technique (Figure 5). The physicians will be acutely aware of their conscious incompetence with this new instrument or technique, and will be less likely to favor the new technique over a technique for which they have already achieved unconscious competence. Especially if an endoscopist does not have any injury due to scoping, the physician may be unwilling to relearn endoscopy with a new technique that, at least initially, prolongs procedure time as he/ she goes through the learning curve. The closer the hand-tool interaction of the new system is to the current system, the easier for the physician to utilize the new platform with a minimum learning curve. As discussed above, it is unlikely that incremental modifications to current endoscopes will result in an endoscope design that can address all ergonomic areas of concerns. Thus, there is a fine balance that must be achieved when introducing new techniques or technologies in order to gain widespread physician acceptance. A promising and potentially effective way for acceptance of a new scope will be to train the gastroenterology fellows on the new systems. However, it is recognized that attending gastroenterologists are the ones who are teaching the fellows. We have found that physicians with hand injuries are more willing to take the time to learn a new ergonomic endoscope even if it is a nonconventional scope since they are more aware of musculoskeletal disorders as a result of scoping. Therefore, it is important for the physicians to be educated and informed of the endoscopy-related injuries. It is also worth mentioning that endoscope manufacturers need to work closely with endoscopists for training of new instruments especially nonconventional scopes. 5.2. Cleaning and disinfection Although high standards for processing and disinfection of endoscopes have been established, there are still issues related to bacterial outbreaks. The working channel and distal end elevators may be especially challenging. In addition, reusable accessories that accommodate the utilization of endoscopes more ergonomically such as reducing gravitational load, devices that were described earlier, will
need to meet the reprocessing and cleaning requirements. This is not an issue for disposable endoscope solutions. Although single use solutions or simple reprocessing solutions for reusable instruments are necessary, keeping the cost low is an inherent technical challenge for the designers and manufacturers. 5.3. Financial considerations For standard endoscopy procedures such as colonoscopy, current procedural terminology codes are used, even if nonconventional endoscopes or specialty instruments are used. Therefore, the new innovative ergonomic endoscopes or supporting devices cannot be much more expensive than conventional scopes to be adapted widely. This puts pressure on the scope designers and manufacturers to follow the approaches and solutions that are cost effective. Any new technique and instrument will require a learning curve and training. This will be a challenge in the current system as typical gastroenterologists perform a high volume of endoscopic procedures and any new technique that requires retraining and creating new muscle memory will also require time and practice, which initially will prolong procedures. From a hospital personnel standpoint, musculoskeletal injuries can lead to work load reduction, missed days of work, reduction of activities outside of work, and long-term disabilities. Therefore, when evaluating cost and financial aspects of time associated with learning and using a new instrument, the physician’s health and loss of productivity must be considered as well. 6. Summary The design of conventional endoscopes inherently suffers from ergonomic principle considerations and instrument design changes are required to improve the interactions of the endoscopists with the instrument and reduce the prevalence of musculoskeletal injuries. Technological innovations such as ergonomically designed endoscope handles, self-propelled endoscopes, and accessories that reduce high and sustained forces, repetitive movements, and awkward postures from endoscopists may reduce the inherent physical stresses of endoscopy and the risk of biomechanical injuries. It is important to realize that training with current scopes, interaction with current instruments over time, and repetition of tasks using the scopes, result in physician’s proficiency in technique and development of a muscle memory to perform endoscopy, or unconscious competence. This creates challenges in encouraging endoscopists without injuries to spend time relearning a new instrument and technique, during which time the physician will be aware of their conscious incompetence. In addition, there will be a financial burden on the system as the physicians retrain and require more time to perform the endoscopy procedure. However, as discussed earlier, physician’s health and loss of productivity due to injuries must be considered when cost and financials are being evaluated. References
Fig. 5. Stages of competence, current scopes, and new technology.
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