Keywords
cautery - clipping - endoscopic training - injection - PEG - polypectomy
Introduction
The training of endoscopic skills on live patients in endoscopic unit under supervision
of attending physician can cause potential harm to the patient.[1] The direct observational tools can individualize the learning curve of each trainee
to develop competence in particular endoscopic skill.[2] Repetitive practice at their own learning pace is a major advantage of a simulator.
It also provides a risk-free environment as compared with stressful real patient scenario.[2]
[3] Simulation training provides experience in endoscopic skills to manage in real-life
scenarios.[4] The four major types of simulators are mechanical models (made of nontissue-plastic/wire
materials that lack haptic feedback), live animal models (swine commonly used, but
labor intensive), composite animal organ simulators using explanted organs (cannot
mimic real-life scenarios), and virtual reality trainers (expensive) that can limit
their use.[2] But the use of human cadaver for endoscopic training is not well studied.
The role of the teacher is to break down the steps of the procedure with verbal communication
and repetitive instruction to let the trainee master the procedure eventually.[2] The simulator by itself has the feedback to allow repeated practice by trainees
without the continuous presence of a trainer.[5] But predefined learning goals have to be defined and trainer feedback is important
in endoscopic training.[6]
[7] Repetition and feedback as effective learning methods can improve cognitive/technical
skills, lessen the learning curves, with faster skill acquisition especially in a
human cadaver laboratory. It also offers a lifelike platform to learn through hands-on
practice rather than standard bed side learning. The frequency and exposure of the
procedures between one training institution to another may be different.
The aim of the study was to assess the feasibility of human cadaver in enhancing endoscopic
skill in percutaneous endoscopic gastrostomy (PEG), injection, banding, polypectomy,
cautery setting, and clipping.
Materials and Methods
Cadaver Environment and Endoscope
All human cadaveric endoscopic procedures in this feasibility pilot study were performed
at M.S. Ramaiah Advanced learning center (MSR ALC), Bangalore. The fundamental steps
of endoscopic skills- scope handling, checking scope- knobs / air/water/ suction function
before intubation, maintaining luminal view, use of distension/ suction/ lens washing,
retroflexion and passage of scope in to second part of duodenum were trained in supine
position of cadaver.[1]
Biosafety Level
The human cadaver used in the study module was negative for blood-borne virus test
(human immunodeficiency virus, hepatitis B and C) and was stored before the onset
of the coronavirus disease 2019 (COVID-19) times. All the delegates had personal protective
equipment (laboratory gown, two pairs of gloves, face and eye protection, and a N-95
mask covering mouth and nose completely) along with social distancing norms.
Training on Human Cadaver
Training on Human Cadaver
A forward viewing single channel gastroscope (GIF 150, Olympus, Tokyo, Japan) with
an inbuilt light source processor (Olympus; CV-170 LED/HD) was used for the training
module.
The earlier attempts to intubate a supine cadaver were difficult at the postcricoid
area. A modified entry in to the esophagus was made from the left by a neck incision
([Fig. 1])
Fig. 1 (a) Modified neck incision showing thyroid cartilage and thread delineating the esophagus.
(b) The esophageal lumen delineated by forceps and thread after exposure of thyroid
cartilage. (c) Endoscope passed through the neck incision. (d) As earlier feedback was related to cadaver environment, only abdomen and neck of
the cadaver were exposed with the remaining body that was draped (bold white arrow).
Training Module Curriculum
Training Module Curriculum
The training module structure is given in [Fig. 2]. The training module started with an hour of interactive didactic lecture along
with discussion on the preprocedure (indications, contraindications), intraprocedure
(procedural steps), and postprocedure (early and delayed complications). Later the
model was used as a workshop (4 hours) with six teams (2 trainees each) and a mentor
followed by an hour of debriefing session. The teams were divided as performing, assisting,
and commentary teams. The remaining three supporting teams are watching the key steps
of the procedure and correcting whenever necessary. The training approach was based
on directly observed procedural skill training[8] and Pendeltons rules.[9] Trainees underwent supervised hands-on endoscopic session, to acquire the pre-designated
endoscopic skill through focused repetition and feedback.[10]
Fig. 2 Training curriculum flowchart. PEG, percutaneous endoscopic gastrostomy.
The training module had five advanced endoscopic techniques: PEG placement, endoscopic
injection (EI), endoscopic band ligation (EVL), snare polypectomy (SP) of simulated
polyps, thermal cautery (TC), and endoscopic clipping (EC) of the mucosal defects.
All the procedures were performed on a single human cadaver by 6 teams.
Percutaneous Endoscopic Gastrostomy Skill
Percutaneous Endoscopic Gastrostomy Skill
The procedure steps were by two-person Ponsky Gauderer pull technique using 24 Fr
gastrostomy tube (Wilson-Cook, Winston-Salem, North Carolina, United States) and are
described in [Figs. 3 ]and [4].[11]
Fig. 3 (a) Maximal gastric distension and transillumination on anterior stomach wall (critical
step) and digital 1:1 pressure (percutaneous endoscopic gastrostomy [PEG] site identification).
(b) Puncture was made with an angiocath (22G x 1 ½”) after skin incision (fourth team
PEG site). (c) A ready opened cold snare at the anticipated entry site on endoscopy side was used
to catch the catheter. (d) A figure of 8 knot attaches the guidewire and PEG tube wire. (E) Snare was reused to tightly hold the internal bumper of the PEG tube that aids in
easy intubation of the scope.
Fig. 4 (a) The inner bumper was fixated at 5 mm from gastric wall with appropriate pull-on
abdominal end. (b) Troubleshoot/wrongly placed third percutaneous endoscopic gastrostomy (PEG) inner
bumper. (c) Endoscopic picture of all six bumpers. (d) Abdominal end showing all six PEG tubes. (e) Six teams at operating room.
EVL skill: Multi-Band Ligator (Wilson-Cook; 6 shooter) was used for the EVL skill development.
The barrel has to be fixed to the tip of the scope properly. Wall suction with white/red
out (significant tissue is suctioned into the barrel) and release of band on the gastric
folds (considered as varices) were performed. One band has to be released by clockwise
rotation of the handle. The applied bands were considered as simulation gastric polyps
are described in [Fig. 5].
Fig. 5 (a) Proper fixation of banding cylinder at the end of the scope. (b) White out of the glove to secure proper suction before intubation. (c) Considering gastric folds as varices. (d) Red out of the mucosa to ensure significant tissue is suctioned before band deployment.
(E) Troubleshoot of two bands deployed by double rotation that simulates a polyp.
EI skill: The injector used was injector force max (NM-400L-0423; 4 mm 23 G needle). The skills
required to perform include checking the needle—in/out and patency with normal saline
of 2 mL (dead space volume), injector has to be passed down the working channel to
the target site, communication with right hand assistant for the deployment of needle
and the critical step of injection to the desired plane. Four-quadrant injection was
chosen around the simulated polyp with submucosal elevation as described in [Fig. 6].
Fig. 6 (a) Proper positioning of the needle at desired site. (b) Correct command of needle out/in after sheath out. (c) If submucosal plane is not achieved, puncturing while injecting was followed to
get the proper plane as in parts (d, e). Troubleshoot of wrong injection method far away from scope without control.
SP skill: Proper application of the snare (snare master SD-210 U-25; Olympus) through the working
channel below the band of the simulated polyp along with good communication with the
assistant. The snare should be able to tent the lesion and should not be overtight
nor to be loose as in [Fig. 7].
Fig. 7 (a) Simulated polyps adjacent to peg tube bumper. (b) Correct positioning of electrocautery snare at the base of polyp. (c) Tenting the polyp away from the base. (d) Resection of polyp and removal of polyp. (e) Postpolypectomy base to watch for target sign.
TC skill: Cautery machine (Olympus ESG-300 with APU upgradation compatibility) was used for
the polypectomy. The skill required was to connect to the snare with electrocautery
and to deliver proper thermal energy for polypectomy. The cautery settings used were
40 pulse cut fast and forced coagulation with effect 2. The endoscope has to be stabilized
at proper angle and force, with probe tip closer to scope tip to apply firm and steady
pressure on snare for polypectomy.
EC skill: The clip used for training was HX-110LR with applicator HX-610–090L (Olympus). The
skill included proper loading of clip on to the introducer, which has to be then passed
into the working channel. Proper clip application to the post polypectomy mucosal
defect was done by changing the angle of endoscope. The target was positioned perpendicular
and suction was used for definite clip application as in [Fig. 8].
Fig. 8 (a) Proper endoscopic position and clip opening perpendicular to the mucosal defect.
(b) Opposing the edges of the defect with the clip. (c) Multiple clips used to close the polypectomy site.
An anonymous course evaluation survey using a 5-point Likert scale (1 = strongly disagree,
5 = strongly agree) was filled by the participating trainees. The study was approved
by institute ethical board.
Results
Twelve trainees (11 final-year postgraduate students and one fourth year fellow of
medical gastroenterology) received training in this model. All the trainees uniformly
agreed that using real accessories and normal human anatomy for learning endoscopic
skills has more educational value. The educational content delivery was better than
traditional lectures and reading alone. All have agreed that they had exhaustive hands-on
time in the workshop and never had such an experience. Three (25%) of them had first
time performed EC, SP, TC procedures. Eleven of the 12 trainees agreed to come for
second time for another module. The remaining trainee was concerned of the cadaver
environment and COVID-19 times. All the trainees felt that the procedure skills were
similar to real-life environment. All of them agreed that they are better prepared
for performing the procedures on real-life patient setting after having undergone
the structured simulation program.
PEG placement: All the trainees felt that for choosing PEG site selection, transillumination was
not feasible in spite of maximal gastric distension but due to thick abdominal wall
of the chosen cadaver. PEG site was chosen by finger indentation and guiding needle
techniques. The embalming solution was greasy that led to masking of the scope vision,
requiring cleaning of the lens very often. The rest of the procedure steps were similar
to procedure on real patients.
EVL, SP, TC, and EC procedures: The procedures had the real-life feel of the trigger for band release, positioning
of snare for electrocautery, and clip application for the mucosal defect. The only
differences were that it was easier to cut and clip was not opposing significant tissue
as compared with live patients.
Injection: In 48 injections, 10 (20%) did not have the submucosal lift in the practice of 4
quadrant injection. The possible reason was wrong plane of injection due to application
of more pressure on the needle. Once the assistant is injecting the saline, pricking
at the same time, they were able to get the submucosal plane.
Complications: All the trainees were able to cut the simulated polyp below the band and none of
them had a full thickness perforation. Bleeding could not be simulated in the current
module. All of them felt that they were more confident in cadaver environment as there
would be no complications. They also felt that coordinated skill development is easier
in Pendleton model as they can discuss with their colleagues and remembered their
schooling days.
Discussion
Endoscopic skill development in trainees is based on apprenticeship model on patients
rather than on simulation model. Majority of the programs lack structured training
modules for repetitive learning of interventions. Though endoscopic simulators can
be used for training, they are not available in many teaching hospitals. In this study,
the aim was to improve PEG, EI, SP, TC, EVL, and EC skill module involving 12 trainees
with mentor feedback on a human cadaver.
The use of human cadaver in training endoscopic skills can help trainees to understand
therapeutic application of accessories. The endoscopist should understand all the
accessories better than anyone else in the endoscopic room. The ability to effectively
communicate with endoscopic nurses/technicians can also be trained in human cadaver
environment.
The GI mentor II (Simbionix USA. Inc., Cleveland, Ohio, United States) includes training
modules on polypectomy, clipping, and gastrointestinal bleeding. Live porcine and
canine models mitigate usage for training due to cost and ethical concerns. The Erlangen
Active Training Simulator for Interventional Endoscopy and Grund model have either
prepared porcine or artificial tissue models with perfusion pump to simulate bleeding.
But there is no reported scientific data about use of human cadaver model in endoscopic
skill development.[12]
Virtual reality simulators can simulate SP and EC skills, but the assessment and feel
of the tissue are only possible in human tissue. However, there are no simulation
models for PEG placement. Human cadaver model can fill in the lack of PEG training
model as simulators lack the haptics of normal tissue.
In terms of feel of the tissue, trainees felt that learning in simulated environment
was helpful for EVL, EI, EC, and SP. The only observation was that the polypectomy
cut was faster than live human tissue. Another important factor in training was task
variability that is common in live endoscopic procedures. The presence of mentor with
changing modules for each team increased the exposure for troubleshoot/complications
at each critical step that can enhance skill acquisition.
Earlier studies showed significantly higher procedural success rate and a nonsignificant
reduction in occurrence of complications in clinical practice on simulator training.[13] Multiple single-day intensive hands-on training in endoscopic therapeutic courses
leads to significant improvement in trainee skills and is beneficial to integrate
simulation models to actual supervised endoscopic skill training. But the minimum
number of procedures needed to acquire and maintain the skill set is not known.[4]
[5]
[14]
[15]
Supplementation of teaching with prerecorded videos as part of ASGE learning center
(http://www.asge.org) and online in DAVE project (Digital Atlas of Video Education, http://www.daveproject.org) can also be done.
The study has several strengths. It is the first innovative human cadaver endoscopic
training model without any prior reported literature. Single model was used for training
PEG, EVL, SP, EI, TC, and EC skill development, feedback, and increased fellow’s basic
knowledge. The use of the regular accessories, improvement in endoscopic skills, and
feel of normal tissue were uniformly accepted by all the trainees. The module had
low frequency high-risk procedures and trainees were better prepared for emergency
endoscopic interventions.
The study has several limitations. It is a single-center study with limited study
group of 12 trainees. The study was not powered to detect the difference in DOPS scores
before and after the training module. All the trainees did not have uniform procedural
skills. The absence of esophageal intubation, the supine positioning of the cadaver,
and the endoscope had to be cleaned repeatedly for better vision as the preservative
was greasy. Bleeding as a complication could not be emulated. Though after the experiential
learning of the skills and receipt of the feedback in the simulated environment, how
it will translate to real-life environment was not studied.
Further work needs to be done to improve the utility of this model within the teaching
curriculum. The endoscopic visibility has to be improved probably by precleaning the
stomach by a detergent. There should be better access for esophageal intubation. There
is scope of development of other training modules like technique of endoloop, placement
of different foreign bodies (FB) in stomach and train in FB retrieval methods; creation
of neo-pylorus to simulate stricture for dilation. A comparative study between cadaver,
simulator, and training on live patients to evaluate speed of learning, frequency
of complications to determine skills, and safety of performing endoscopic procedures
can identify the advantages of various study models.
Conclusion
The use of human cadaver to train therapeutic endoscopic skills with predefined learning
objectives can be performed on a teaching module.
Table 1
Potential advantages of using human cadaver in training advanced endoscopic skills
|
Sl. no.
|
Skill set
|
Potential advantages on the human cadaver
|
|
Abbreviation: PEG, percutaneous endoscopic gastrostomy.
|
|
1
|
PEG placement
|
Real experience; multiple trainees were involved at the same time, training as an
assistant to endoscopist; instant performance feedback by mentor
|
|
2
|
Band ligation
|
Facilitate cooperation between trainees; exposes unforeseen band application—double
band placement/slippage of bands
|
|
3
|
Injection
|
Allows trainee to get the haptic feel of the amount of pressure required to get the
desired submucosal plane and how to correct it
|
|
4
|
Snare polypectomy
|
Quick feedback, less risks, allows snaring of polyp at difficult and every possible
location
|
|
5
|
Electrocautery
|
Actual patient is safe; programmed cautery settings can be presented
|
|
6
|
Endoscopic clipping
|
Proper clip application to mucosal defect; reproducible; aids in decision making;
trainees only loaded and applied the clip
|
