Keywords
endoscopy - esophagus - metallic stent - simulation - training
Introduction
Simulation-based learning for therapeutic endoscopic skills can accelerate the learning curve with repeated practice without potential harm to the patient.[1] Simulation offers advantages to both trainees and trainers. Trainees can make mistakes and learn from them. Trainers can vary the difficulty of the training task to mimic variation in anatomy, pathology, clinical presentation, and difficulty in real procedures.[2] Provision of feedback with debriefing before and after the procedure are essential components of a simulation-based curricular training program. Intra-procedure feedback may not achieve optimal learning of the skillset as the learner's focus will be on the feedback than on the skillset.[2]
[3] Training in groups can also help in identifying knowledge gaps of trainees and facilitate learning from each other. Group training also facilitates improvement in nontechnical skill development of communication, decision making, leadership, and crisis management.[2] There is variability in clinical and procedural exposures between many educational institutions in a large country like India without any mandatory competency certification.[4] However, limited simulation models are available for training advanced endoscopic techniques with additional challenges of varying backgrounds, skillsets, and limited time away from clinical duties.[5]
Endoscopic placement of esophageal self-expanding metallic stent (SEMS) is an effective palliative treatment of malignant dysphagia and for sealing malignant tracheo/broncho esophageal fistulae.[6] Temporary placement of esophageal SEMS in refractory benign stricture, iatrogenic leaks/perforations, refractory esophageal variceal bleeding, and stent in stent placement to remove an embedded stent are recommended.[7] The aim of the study was to assess the feasibility of the novel stricture model with hands-on modular curriculum to teach endoscopic esophageal SEMS placement.
Materials and Methods
Objectives and Design
The study was a pretest–posttest design without a control group involving a novel simulation device for esophageal SEMS placement. Primary measurements were obtained at baseline (pre-test) and after the hands-on intervention (post-test).[8]
Training Module Curriculum
The training module started with pre-test followed by an hour of interactive didactic lecture along with discussion on the preprocedure (indications, contraindications), intra-procedure (procedural steps), and postprocedure (early and delayed complications) [Table 1]. Later the model was used as a workshop (4 hours) with 10 teams (2 trainees each) and a mentor, followed by an hour of debriefing session and post-test.[3] Three advanced flexible endoscopic courses were conducted from 2022 to 2024. The training sessions involved 20 final-year postgraduate fellows in each session from different centers across India. The intervention was an intensive hands-on exercise held at Mathikere Sampangi Ramaiah Medical College and Hospitals, Bangalore. The study was approved by the institutional ethical review board. Two trainees performed the module alternately between endoscope and stent deployment ends. Five-point Likert scale questions regarding visual appearance, haptic feedback, usefulness in training, an overall opinion, and a section for free-text comments were used for scoring both by trainees and trainers.[8]
Simulation Model
The simulated model used for the esophageal stenting module was a non-tissue model made of silicone, which comprised esophagus, stomach, and duodenum from Cook Medical (CM; [Fig. 1]). The model has two esophageal nonobstructing growths between 15–20 and 23–28 cm from the upper opening. Simulation Z line is at 35 cm and gastroesophageal junction is at 38 cm. There is also a zip provided at the proximal growth for easy accessibility. A 0.035” guidewire (GW) was placed under endoscopic guidance into the stomach and the endoscope is exchanged with either Boston Scientific (BS)/CM SEMS. Fluoroscopy was not used in the study.[9]
Fig. 1 (a) Simulation model showing esophagus, stomach, and duodenum; (b) opened zip showing tumor inside; (c) endoscopic view of proximal tumor; (d) endoscopic view of distal tumor and Z line; (e) retroflexion view of stomach.
Wallflex Partially Covered Stent (BS)
The BS stent used in the training module was 12 cm partially covered Wallflex esophageal SEMS which has 9 cm polyurethane covering and flared uncovered segments at both ends (1.5 cm at both ends are uncovered) for fixation. Over the already placed GW, the stent introducer is loaded and positioned about 2 cm proximal to the tumor. The position was confirmed by the simultaneous introduction of the endoscope adjacent to the stent introducer. The endoscope was placed at the anticipated upper end of the SEMS. Stent is deployed by pulling back the catheter with careful monitoring of the upper end of the stent/yellow visual marker under endoscopic guidance. The position of the braided stent was adjusted for the foreshortening with gentle push or pull and by measurements on the endoscope. After complete SEMS deployment, the catheter was removed and accurate positioning of stent was confirmed ([Fig. 2]).
Fig. 2 (a and b) Endoscopic view of GW across the gastroesophageal junction and into the stomach; (c) endoscopic view of stent introducer placed over the GW; (d) completely deployed BS SEMS. BS, Boston Scientific; GW, guidewire; SEMS, self-expanding metallic stent.
For reloading SEMS, the stent is re-constrained back on to the catheter by pushing it inside the sheath. Once the flare of the stent is loaded on the catheter, the catheter hub was pushed ahead to get the stent completely inside and reused for the next trainee ([Fig. 3]). Re-constraining the stent post 75% of its original capacity (point of no return) is not possible in the real world as there can be compromise on the luminal patency of the stent.
Fig. 3 (a) BS complete stent introducer assembly; (b) distal end of the SEMS; (c and d) coaxial deployment of SEMS; (e and f) SEMS re-constrained into the catheter by pushing the tip inside the sheath. BS, Boston Scientific; SEMS, self-expanding metallic stent.
Evolution 12 cm Fully Covered Esophageal Metallic Stent (CM)
The stent used in the training module was 12 cm fully covered Evolution esophageal SEMS which has full silicone covering with flared segments at both ends (1.5 cm at both ends) for fixation. The deployment of the SEMS is by using a piston grip catheter which has a stent deployment indicator, a deployment trigger, a directional button, a point of no return, and a safety wire. After removing the protective sheath, over prepositioned GW the stent introducer was passed in small increments. An endoscope was placed adjacent to the stent introducer for confirming the proximal end of the SEMS by a blue indicator. After removing the red safety guard from the handle, stent is deployed by squeezing the trigger. If repositioning is required, the directional button is pushed to the opposite end. For initial recapture or redeployment, the button has to be pressed when squeezing the trigger. Once the point of no return is reached, remove the safety wire out of the delivery handle. The stent is completely deployed by squeezing the handle. Once complete expansion of the stent was confirmed, then remove the introducer handle along with the GW. For reloading SEMS, the stent is re-constrained back on to the catheter by pushing it inside the sheath and careful movements of the trigger handle ([Fig. 4]).
Fig. 4 (a) Piston grip catheter with red safety guard from handle; (b–d) distal end of the stent introducer and later deployment of SEMS by pushing the trigger; (e) re-constrained back on to the catheter by pushing it inside the sheath and handle movement. SEMS, self-expanding metallic stent.
Repositioning of SEMS
For removal or repositioning, a rat tooth forceps was used to grasp the lasso at the proximal or distal end and gentle pull or push force is applied for the desired location.
Pre-test and Post-test Questionnaire and Scoring
The 10 questions and the procedure checklist were standardized by face and content validity with the trainers and an external expert. The pretest questionnaire contained 10 items, covering the key points pertaining to the SEMS deployment. The procedure check list used for the hands-on simulation was used for six times, following which a post-test comprising a similar set of questions was administered. Each correct answer was scored as 1 and mean (%) scores were calculated.
Statistical Analysis
Data were analyzed using SPSS software “SPSS Inc. Released 2009, PASW Statistics for Windows, Version 18.0. Chicago: SPSS Inc.” The overall score was presented in terms of the mean after converting to percentage. Paired t-test was used to compare the mean score between pre- and post-test scores. A p-value of <0.05 was considered as statistically significant.[8]
Results
Trainee and Instructor Validity
Sixty final-year postgraduate fellows with varying endoscopic experiences participated in the training programs. All the participants had completed more than 100 therapeutic procedures. Three fellows had deployed one esophageal SEMS each earlier. All the trainees and the instructor had rated the model as excellent or good with stiffer haptics than real tissue. Fifty men and 10 women comprised the study group. Ten trainees wrote in free-text comments that the training program was interesting and wanted repeated sessions on different procedures for endoscopic skill training.
Evaluation of Training
The mean (%) pre-test score of 17 (29%) improved significantly to 57 (95%) in mean post-test (%) questionnaire (p < 0.05). There was significant improvement in test questionnaire after the training modules as given in [Table 2].
Table 1
Stenting module for esophageal SEMS placement
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Steps of esophageal SEMS placement
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Pre-procedure
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Patient characteristics for indication, contraindications, consent, risk stratification for sedation, fluoroscopy
Stent characteristics ([Table 2], points 1, 6)
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Intra-procedure
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Stricture characteristics: simple/complex; traversable or not; length of the stricture (proximal and distal ends) to be stented, the relation of the stricture with upper and lower esophageal sphincters and the presence and location of the fistula if present
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Endoscope was passed till the stricture and a 0.035”/0.038” stiff guidewire (GW) was passed across the stricture
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GW left in place and endoscope was exchanged with stent introducer of either BS or CM
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Endoscope was introduced adjacent to the stent introducer to confirm the exact position of the transition zone of stent, reposition if necessary
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Critical step: stent deployed slowly using either coaxial 1:1 (BS) or pistol grip mechanism (CM) for placement accuracy of the proximal end of stent to the desired location
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Stent can be re-constrained up to 75% post-deployment for repositioning distally or proximally. Stent is released after confirming placement accuracy by endoscopy
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Post-procedure
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Plan for early and delayed complications: recurrent obstruction due to tumor ingrowth (stent in stent/argon plasma coagulation), perforation or fistula (re-stenting in esophagus/trachea), stent migration ([Table 2]: point 7), and retrosternal pain (analgesics)
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Abbreviations: BS, Boston Scientific; CM, Cook Medical.
Table 2
Ten test questions used for knowledge assessment of esophageal SEMS
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Sl. No.
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Question: correct answer/total number of students (%), n = 60
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Pre-test
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Post-test
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1
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What are stent characters to be noted before placement? Answer: Length of the stent; covering; diameters: introducer, SEMS flange, and body; through the scope/over the wire; Delivery mechanisms: coaxial/suture/pistol grip; proximal or distal release mechanism; point of no return (75%) for reconstrainability.[6]
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30
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90
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2
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What is Nitinol-SEMS material?
Answer: Nitinol (nickel, titanium naval ordnance laboratory) developed by U.S. Navy: Ultraflex (BS) has poor fluoroscopic visibility, which is compensated by gold or silver radiopaque markers; shape memory, super-elasticity, optimal radial and axial force makes them most flexible stents, best for angulated regions; nonferromagnetic causes less artifacts on MRI.[13]
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20
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90
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3
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What are the types of SEMS based on covering materials? Answer: Polyurethane, or silicone, or polytetrafluoroethylene; Fully covered (FC) SEMSs have a cover over the wires to prevent tissue ingrowth, seal fistulas, but have less anchoring power with increased risk of migration; partly covered (PC) SEMSs are with flared uncovered segments at both ends (1.5 cm at both ends) for fixation.[6]
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15
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90
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4
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What are the indications for esophageal SEMS placement?
Answer: Palliation of malignant dysphagia and sealing of the malignant tracheoesophageal/bronchoesophageal fistula; temporary (maximum of 3 months) placement of FC SEMS can be considered in refractory benign strictures, esophageal leaks, fistulas, or perforation; treatment of esophageal variceal bleeding refractory to medical, endoscopic, and radiological therapy.[7]
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40
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100
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5
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What are the contraindications for esophageal SEMS placement?
Answer: Life expectancy <4 weeks, uncorrectable coagulopathy or tumor invasion of the aorta or airways, clinically unstable patient.[7]
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50
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100
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6
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How do you choose the length of the stent?
Answer: 4–6 cm longer than that of the obstructive lesion with each side of the stent 2–3 cm longer from the edge of the lesion.[6]
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40
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100
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7
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How do you prevent migration of SEMS?
Answer: Proximally placed hemoclips/suture/stentfix by over the scope clip/shims technique and large flange (25 mm) might reduce the chance of early migration.[14]
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40
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100
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8
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How do you reposition the misplaced SEMS?
Answer: By using foreign body hood protector and a rat tooth forceps, pulling the lasso collapses the proximal end of the stent, which can reposition/remove the entire stent. Distal displacement of the stent is done by grasping the distal portion of the stent with a forceps or inflating a dilating balloon within the stent and applying gentle push pressure.[14]
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30
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100
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9
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What SEMS would you choose for cervical esophageal cancer <2 cm from UES?
Answer: Problems to foresee: increased risk of perforation, airway compression, migration, aspiration pneumonia, and globus sensation mitigated by smaller proximal flange of 14 mm in Niti-S Conio Stent (Taewoong Medical, Seoul, South Korea.)[15]
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15
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90
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10
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How do you remove a PC-SEMS embedded in esophagus? Answer: Stent-in-stent technique to remove embedded PC SEMS.[16]
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10
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90
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Abbreviations: BS, Boston Scientific; MRI, magnetic resonance imaging; SEMS, self-expanding metallic stent.
Feedback and Correct Repositioning
The deployment of SEMS was observed carefully with minimal feedback during the session. If wrongly deployed, stent is repositioned with rat tooth forceps ([Figs. 5] and [6]).
Fig. 5 (a and b) Misplacement of BS SEMS; (c–e) misplacement of CM SEMS. BS, Boston Scientific; CM, Cook Medical; SEMS, self-expanding metallic stent.
Fig. 6 (a) Proximal repositioning of SEMS by grabbing proximal lasso using rat tooth forceps; (b–d); distal repositioning of SEMS by distal lasso and rat tooth forceps. SEMS, self-expanding metallic stent.
Discussion
The current simulation study involving pre-test, lecture, hands-on training, and post-test significantly enhanced the technical skills and knowledge of gastroenterology fellows in placement of esophageal SEMS. Except for three, all the trainees had not deployed an esophageal SEMS earlier. The use of small-group simulation training helped them in acquiring the knowledge and instructor feedback improved their confidence of the SEMS skill set. There are only few reports of SEMS simulation training in the literature.[5]
Simulation-based mastery learning with competency-based training is a next emerging proposed method for procedural task training. Current reliance on number of procedures performed with lack of objective standards results in variable skills among trainees associated with patient safety risk in current bedside endoscopic training. Simulation with predefined learning objectives allows trainees to repeatedly practice essential skills receiving expert feedback repeatedly and gradually develop mastery in the skill set.[10]
Although the simulation-based models are available for basic endoscope navigation with clear mucosal visibility, distension, and few therapeutic procedures,[11] there is no model for training esophageal SEMS deployment. The simulation study was first of its kind on the model. All the trainees had rated excellent in hands-on training on deployment of SEMS on simulation devices. The simulation device also has esophageal tumors mimicking malignancy at two levels in proximal and distal esophagus and does not involve animal tissue. The model can also be used to train repositioning of misplaced SEMS. The instructor can also provide tailored feedback based on trainee skill levels and deficiencies.[5] Near-peer endoscopy teaching by senior fellows to junior trainees provides fewer barriers in endoscopic training.[12] Small group simulation-based training of predefined endoscopic skill set might become a new normal in endoscopic training. Both BS and CM SEMS can be completely reloaded 8 to 12 times carefully and can be utilized for repeat procedures without additional cost.
Limitations
The study is limited with the use of 10 pre-test and post-test questionnaires for validity. The objective evidence of improvement in clinical practice was not studied. But all the trainees uniformly had found the exhaustive exercise useful and wanted similar single-day skill training modules. The study used two different types of stents (BS and WC) but comparison between them was not done. Proximal release stents were not used in the study. Fluoroscopy was not used in the study as it is useful in real-world scenario for accurate deployment of SEMS.
Conclusion
The simulation model using the novel esophageal model for SEMS deployment is effective with good performance evaluation and can be used to train SEMS deployment procedure.
Contribution Details (to Be Tick Marked as Applicable)
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