- Email: [email protected]
A Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training: A Trial of Face Validity
Accepted Manuscript A Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training; A Trial of Face Validity Craig Nesbitt, MRCS, MD, Samuel James Tingle, Robin Williams, FRCR, James McCaslin, FRCS, MD., Roger Searle, PhD., Sebastian Mafeld, FRCR, Gerard Stansby, M.A. (Catab), M.B., M.Chir, F.R.C.S PII:
S0890-5096(17)30941-X
DOI:
10.1016/j.avsg.2017.07.030
Reference:
AVSG 3526
To appear in:
Annals of Vascular Surgery
Received Date: 8 May 2017 Accepted Date: 20 July 2017
Please cite this article as: Nesbitt C, Tingle SJ, Williams R, McCaslin J, Searle R, Mafeld S, Stansby G, A Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training; A Trial of Face Validity, Annals of Vascular Surgery (2017), doi: 10.1016/j.avsg.2017.07.030. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Title: A Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training; A Trial of Face Validity First author: Mr Craig Nesbitt
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Order of authors: Craig Nesbitt1, Samuel James Tingle2, Robin Williams3, James McCaslin4, Roger Searle5, Sebastian Mafeld6, Gerard Stansby7
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Author affiliations:
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1. MRCS, MD. Northern Deanery Vascular Surgical Registrar and corresponding author, Middlesbrough James Cook University Hospital, Middlesbrough.
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2. Faculty of Medical Sciences, Newcastle Medical School, Newcastle, Tyne and Wear NE2 4HH, United Kingdom.
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3. FRCR. Consultant Interventional Radiologist. Northern Vascular Centre, Department of Interventional Radiology, Freeman Hospital, Newcastle Upon Tyne.
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4. FRCS, MD. Consultant Vascular and Endovascular Surgery. Department of Vascular Surgery. Northern Vascular Centre, Department of Vascular Surgery, Freeman Hospital, Newcastle Upon Tyne.
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5. PhD. Head of School & Director of Anatomy and Clinical Skills & Director of Excellence in Learning and Teaching, Newcastle University, Newcastle Upon Tyne.
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6. FRCR. Specialty Resgistrar in Interventional Radiology. Northern Vascular Centre, Department of Interventional Radiology, Freeman Hospital, Newcastle Upon Tyne.
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7. M.A. (Catab), M.B., M.Chir, F.R.C.S. Professor of Vascular Surgery. Northern Vascular Centre, Department of Vascular Surgery, Freeman Hospital, Newcastle Upon Tyne
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Submission category: Basic Science Research (new investigations, experimental work)
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Key words: Endovascular Training, Human Cadaver, Pulsatile Model, Simulation
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Corresponding Author: Mr. Craig Nesbitt, MRCS, MD
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Address: Healeyhope Barn, Waskerley, Consett, Co Durham, DH8 9DB, UK.
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Telephone: 07969223061
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Email: [email protected]
ACCEPTED MANUSCRIPT Abstract Objectives: Determine the face validity of a pulsatile fresh frozen human cadaver model (PHCM) for
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training endovascular practitioners.
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Methods: 12 endovascular clinicians performed the same two procedures (catheterisation of the left
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renal artery and left subclavian artery) on PHCM, and Simbionix angiomentor virtual reality simulator
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(SVR). They were randomised to begin on either the PHCM or SVR. A pre-trial questionnaire
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determined participants’ endovascular experience. After training, participants rated statements
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relating to their experience on a numerical scale from 1 to 5, with 1 representing the strongest
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agreement with the statement.
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Results: When participants were asked to compare the realism of training modalities with live
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patients, PHCM scored significantly higher than SVR on statements regarding “realism of vascular
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access” (p=0.002) “guide-wire manipulation” (p=0.001) and “vessel catheterisation” (p=0.004).
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Candidates again favoured PHCM as “a valuable learning exercise” (p=0.016) and strongly favoured
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PHCM as a “useful training model” compared to SVR (p=0.004).
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Conclusions: This is the first published trial in world literature to assess the validity of a PHCM for
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training endovascular practitioners. The PHCM demonstrates good face validity when compared to
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both real patients and the SVR model, and holds exciting potential.
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Introduction
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Endovascular intervention now plays a crucial diagnostic and therapeutic role in almost all branches
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of surgery, none more so than vascular surgery where endovascular techniques have transformed
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the specialty. The key attraction of endovascular surgery is the minimally invasive nature of the
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techniques, which offers reduced morbidity and mortality when compared to their equivalent open
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procedure options.[1] For these reasons there has been a rapid increase in the number of
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endovascular procedures being performed; an American survey found a 422% increase in
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endovascular procedures logged in the casebooks of vascular trainees between 2001 and 2007.[2]
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ACCEPTED MANUSCRIPT The explosion in therapeutic endovascular treatment options has resulted in a great need to tackle
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the issue of training endovascular skills for the practitioners of the future. This need is further
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intensified by the fact that endovascular surgery requires a different set of technical and cognitive
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skills, when compared to open surgery.[3] Indeed, operating in a three dimensional field from a two
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dimensional view, altered haptics and emphasis on hand-fluro-eye co-ordination are all challenging
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skills to master.[4]
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One attempt to fulfil this training need is the use of medical simulators. Simulation is now utilised
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widely in all branches of surgery, especially for the training of minimally invasive techniques. There
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are now a number of high fidelity endovascular simulators available, which use computer-generated
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images of the human vasculature to allow trainers the ability to interact with the model using an
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interface device.[5]
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Virtual reality has promise for both objectively demonstrating procedural competence,[3] and for
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delivering effective training of novices, with a recent face validity trial supporting its use.[6] Whilst
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virtual reality is now becoming integrated into endovascular training across Europe and America, it is
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not without its limitations. Simulators lack the tactile feedback found in real patient vessels, are
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unable to simulate arterial puncture, and units cost in excess of £100,000. In addition, conclusive
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evidence remains poor as to their exact benefit, with a 2006 systematic review failing to
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demonstrate a firm advantage from expensive high-fidelity surgical simulators.[7]
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The last decade has also seen an increasing number of human cadaveric (HC) based workshops in
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higher surgical training.[8] The suitability of HC for training open vascular surgical procedures is
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recognised,[9] and cadaveric perfusion to enhance open vascular surgery is also reported.[10] Garret et
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al described a technique for creating isolated pulsatile segments in a HC model,[11] and the use of
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cadavers for stent graft development has also been reported.[12-14] However, there is a lack of
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literature investigating the use of HC for endovascular training, despite the increased use of HC for
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training in other fields.
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ACCEPTED MANUSCRIPT We recently published a technical note detailing a method for establishing a pulsatile fresh-frozen
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human cadaver model (PHCM), which has potential to be used for endovascular training.[15] While
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this technical note demonstrates the feasibility of the model, further research is needed to validate
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the model as a useful and effective tool for training.
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Face validity is a simple form of validity, where participants judge the degree of resemblance
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between a model and a real-life situation.[16] In the context of the present study this involves
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endovascular experts comparing a training model with a real endovascular procedure. The aim of
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this trial was to establish if the PHCM demonstrated face validity comparing it to both real live
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patients, and to a high fidelity virtual reality simulator.
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Methods
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Vascular surgeons, radiology, cardiology and neurology interventionalists with endovascular
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experience were recruited to take part in the trial, as practitioners who perform endovascular
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procedures (on live patients) on a daily basis were considered to be the best judges of the model’s
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realism and suitability for training.
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Details of the PHCM model evaluated in this trial has been previously published as a technical note
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in this journal.[15] Briefly, this model uses a pulsatile blood pump (1405 Harvard Apparatus™,
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Massachusetts, USA) to perfuse a fresh frozen cadaver, with inflow through the right common
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carotid artery and outflow through the left common femoral and right superficial femoral arteries. In
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order to gain some perspective on the PHCM as a training model, a comparative training experience
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on a high fidelity virtual reality simulator, Simbionix ™ angiomentor (SVR), was included in the trial’s
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design.
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Each participant performed two index procedures on both training models. Procedure 1 involved
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cannulation of the left renal artery and confirmatory angiogram from access in the right femoral
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artery, and procedure 2 involved cannulation of the right subclavian artery and confirmatory
ACCEPTED MANUSCRIPT angiogram from access in the right femoral artery; representing simple and intermediate procedures
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respectively. Candidates were randomised, using a closed envelope system, both to which training
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model to use first, and to which procedure to perform first.
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Formal ethical approval was not required as it was deemed that the proposed trial represented
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‘technical development and training’.
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Questionnaires
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Before candidates began training they completed a pre-trial questionnaire to determine certain
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candidate demographics; level of seniority, endovascular experience, previous exposure to both
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human cadaver and VR simulators, handedness, musical instrument experience, exposure to video
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games, and use of correctional glasses. Those participants who had performed >50 procedures were
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considered expert.
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After completing both procedures on both models, candidates completed a post-trial questionnaire.
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This questionnaire asked candidates to rate their agreement with a series of statements regarding
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their experience training on both the SVR and PHCM. Candidates’ agreement with these statements
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was recorded on a standard Likert scale with ‘1’ representing their greatest agreement and ‘5’ their
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greatest disagreement with the statement. In addition, free-text boxes allowed candidates to
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comment on the strengths and weaknesses of each model.
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Statistical analysis
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Statistical analysis was undertaken using the Statistical Package for the Social sciences version 19
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(SPSS, Chicago). Wilcoxon Matched Pairs Signed ranks test was used to compare questionnaire
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statements from the two simulators. A p-value of <0.05 was considered to be significant. Results are
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displayed as mean (± SD).
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Results
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In total, 12 participants were recruited to the study. Of these, there were; 5 consultant radiologists,
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3 consultant endovascular surgeons and 4 senior trainees (2 vascular surgery, 2 interventional
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radiology). Additional demographic information for the candidates can be found in Table 1.
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All candidates completed both index procedures in the SVR, with no noted procedural or technical
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complications. All participants completed index procedure 1 on the PHCM, however four
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participants failed to complete index procedure 2 (cannulation of the right subclavian artery and
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confirmatory angiogram) on the PHCM. This was partly due to candidates’ level of experience, but
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also due to extensive atheromatous disease in the aorta, making cannulation of the subclavian
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artery challenging even for the most experienced consultant operators.
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Mean Likert scores for the various questions on the post-trial questionnaire can be found in Table 2.
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When comparing the realism PHCM to live patients the mean Likert scores were all less than three;
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this indicates that participants agreed that the PHCM represents a high fidelity model. Participants
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strongly agreed that using the PHCM was a valuable learning experience (1.25 (±0.45)), and that the
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model is useful for training endovascular skills (1.25 (±0.45)).
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Applying the Wilcoxon Matched Pairs Signed ranks test to compare the Likert scores revealed several
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significant differences between PHCM and SVR (Table 2). Comparing the fidelity of the models
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candidates showed a significant preference for PHCM concerning vascular access (p=0.002),
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manipulation of guidewires (p=0.001), and catheterization of vessels (p=0.004). Candidates also felt
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the PHCM was a more useful training model compared to SVR (p=0.004).
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The final section on the post-trial questionnaire provided free-text boxes, for participants to
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comment on the strengths and weaknesses of the two models. Comments relating to perceived
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strengths and weaknesses for PHCM can be found in Table 3, and similar information relating to SVR
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can be found in Table 4. These will be explored in the following discussion.
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Discussion
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In the present trial, PHCM [15] was compared in a controlled environment under standard conditions,
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to both live patients and a SVR, through the opinion of endovascular experts. Overall, candidates
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were impressed with both the fidelity and training potential of the PHCM (mean scores <3; Table 2).
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Compared to a widely used virtual reality simulator, candidates preferred training on the PHCM
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(2.00 (±0.95)), and also found it to be more realistic (1.58 (±0.67)); Table 2.
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PHCM scored significantly higher than SVR on individual statements regarding realism, including
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vascular access (p=0.002), manipulation of the guidewire and catheter (p=0.001), and
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catheterisation of the vessels (p=0.004); Table 2. This was also apparent in candidates’ free-text
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comments about the PHCM: “it felt like a patient that needed treating with respect”,
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“wires/catheters are as in vivo” and “absolutely realistic” (Table 3). In contrast candidates’
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commented that SVR was “a little artificial” with “entirely predictable responses, poor tactile
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feedback”, and “limited haptic feedback” (Table 4).
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The only feature of PHCM that scored less well when compared SVR was that of the realism of
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performing an angiogram (2.75 (±0.97)), although this was not significant (p=0.096). This was in
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agreement with several comments made by the candidates on their post-trial questionnaires (Table
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3), indicating they did not find performing an angiogram in the HC comparable to live patients. For
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example one candidate felt the washout of contrast was slow, and this mimicked dissection.
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This observation was due to heavy atheromatous disease in the cadaver, which caused resistant
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residual thrombus that subsequently exacerbated the problem of residual contrast post angiogram.
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This remains a disadvantage of the PHCM versus the more predictable training experience of SVR. In
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fact, the severity of disease in the HC resulted in difficulty in cannulating the right subclavian artery;
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not all expert candidates were successful in completing this task in the allotted time.
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ACCEPTED MANUSCRIPT Whilst the use of human cadavers is increasing in other fields of surgical training,[8] this is the first
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study to attempt validation of a human cadaver model in the field of endovascular training. The
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methodology used in this study is similar to that which has been adopted in many trials of both
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laparoscopic and cadaveric training, when trialists wished to gauge a simple measure of their
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models’ validity. [9, 17-19]
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It is important to acknowledge the limited use of both models in the trial, as both were just used to
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simulate angiography. SVR is able to simulate unlimited numbers of angioplasty and stent
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implantation scenarios in a standard format. Angioplasty and stent deployment is possible in the
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PHCM, but not in a repeatable or standardized format. This remains a limitation of PHCM, and its
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effect on candidate’s opinions in the present study is acknowledged.
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A number of candidates criticised the radiology equipment capabilities of the PHCM (Table 3). In
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contrast SVR is capable of subtraction II, 3D reconstruction and road mapping. However, with
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investment more sophisticated radiology equipment could easily be incorporated to enhance the
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PHCM training experience. The limitation of the equipment made available during this trial is
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acknowledged.
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Finally, it is almost impossible to predict the state of a cadaver’s vessels prior to training, unless
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there is a history of PVD or clinical evidence of arterial disease. Despite these apparent limitations,
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candidates overall favoured their training experience on PHCM (2.00 (±0.95)).
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Conclusion
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Overall, it is concluded that PHCM demonstrated face validity. PHCM represents a feasible
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endovascular training model with a high degree of realism, and compares favourably to both live
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patients and high fidelity virtual reality simulation for a simple angiogram procedure. Further trials
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are necessary to establish the model’s construct validity and true efficacy as a successful training
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model for endovascular practitioners.
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ACCEPTED MANUSCRIPT
Acknowledgments The authors would like to thank the staff of the Newcastle Surgical Training Centre for their support throughout the project, Medtronic Ltd for their generous educational grant and the radiology department of the Freeman Hospital for their expertise.
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Conflict of Interest
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Declaration of Funding
The authors declare a £2000 educational grant from Medtronic Ltd. This was donated to part fund the original purchase of the pulsatile pump. We can confirm that Medtronic had no further role in this or any subsequent trials
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References
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1. Van Herzeele I. Virtual Reality Endovascular Simulation: Ready for Training. Nautilus Academic Books. 1st ed. 2009. 2. Schanzer A, Steppacher R, Eslami M, Arous E, Messina L, Belkin M. Vascular Surgery Training Trends From 2001-2007: A Substantial Increase in Total Procedure Volume is Driven By Escalating Endovascular Procedure Volume and Stable Open Procedure Volume. Journal of Vascular Surgery 2009; 49(5) 1339-1344. 3. Neequaye SK, Aggarwal R, Van Herzeele I, Darzi A, Cheshire N. Endovascular Skills Training and Assessment. Journal of Vascular Surgery 2007;46:1055-64. 4. Berger P, Willems MCM, Van Der Vliet JA, Schultze Kool LJ, Bergqvist D, Blankensteijn JD. Validation of the Simulator and Rating Endovascular SkillS (STRESS)-machine in a setting of competence testing. Journal of Cardiovascular Surgery. 2010; 51: 253-256. 5. Satava RM. Virtual reality surgical simulator – the first steps. Surg Endosc Ultrasound Intervent Tech. 1993; 7: 203-205. 6. 72.74. Lonn L, Edmond J, Marco J, Kearney P, Gallagher A. Virtual Reality Simulation Training in a High-Fidelity Procedure Suite: Operator Appraisal. Journal of Vascular and Interventional Radiology 2012; 23 (10): 1361-1366. 7. Sutherland LM, Middleton PF, Anthony A, Hamdorf, J, Cregan P, Scott D, Maddern GJ. Surgical simulation: a systematic review. Annals of Surgery. 2006; 243: 291-300. 8. Gilbody J, Prosthofer AW, Ho K, Costa ML. The use and effectiveness of cadaveric workshops in higher surgical training: a systematic review. Ann R Coll Surg Engl 2011; 93: 347-352. 9. Reed AB, Crafton C, Giglia JS, Hutto JD. Back to basics: Use of fresh cadavers in vascular surgery training. Surgery 2009;146:757-63. 10. Aboud E, Moursi M. Live Cadavers for Laboratory Training in Vascular Surgery. Journal of Vascular Surgery 2010. 51: 46S-S. 11. Garrett HE Jr. A human cadaveric circulation model. Journal of Vascular Surgery 2001;33:1128-30. 12. Linsen MAM, Vos AWF, Diks J, Rauwerda JA, Wisselink W. Modular Branched Endograft System for Aortic Aneurysm Repair: Evaluation in a Human Cadaver Circulation Model. Journal of Vascular and Endovascular Surgery 2007;41(2)126-29. 13. Arbateli H, Cikirikcioglu M, Pektok E, Walpoth BH, Fasel J, et al. Dynamic Human Cadaver Model for Testing the Feasibility of New Endovascular Techniques and Tools. Ann Vasc Surg 2010;24: 419-22.
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The authors declare no conflicts of interest.
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14. Jongkind V, Yeung KK, Linsen MAM, Heidsieck D, Coveliers HME, Hoksbergen AWJ, et al. Direct Videoscopic Appraoch to the Thoracic Aorta for Aortic Endograft Deliver: Evaluation in a Human Cadaver Circulation Model. Journal of Endovascular Therapy 2010;12:12-18. 15. C, N., et al., Design of a Pulsatile Fresh Frozen Human Cadaver Circulation Model For Endovascular Training. Annals of Vascular Surgery. 16. Schreuder, H.W., et al., Face and construct validity of virtual reality simulation of laparoscopic gynecologic surgery. Am J Obstet Gynecol, 2009. 200(5): p. 540 e1-8. 17. Supe A, Dalvi A, Prabhu R, Kantharia C, Bhuiyan P. Cadaver as a model for laparoscopic training. Indian Journal of Gastroenterology. 2005; 24: 111-113 18. Wadman MC, Lomneth CS, Hoffman LH, Zeger WG, Lander L, Walker RA. Assessment of a New Model for Femoral Ultrasound-guded Central Venous Access Procedural Training: A Pilot Study. Academic Emergency Medicine 2010;17: 88-92 19. Eisma R, Mahendran S, Majumdar S, Smith D, Soames RW. A comparison of Theil and formalin embalmed cadavers for thyroid surgery training. The Surgeon. 2011; 9(3): 142-146.
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Tables Table 1 - Candidate demographics. † PCLN: Cadaveric Percutaneous Nephrolithotomy Course.
Deomgraphic
Candidate
Seniority
5 consultant radiologists 3 consultant endovascular surgeons
Intermediate n = 4 Yes n = 3 No n = 9
Handedness
Left n = 0 Right n = 12
Play musical instrument
Yes n = 4 No n = 8
Play video games regularly
Yes n = 4 No n = 8
Previous VR training
Yes n = 10 No n = 2
Previous cadaver
Yes n = 0 No n = 12
endovascular training Previous cadaver training
Yes n = 10
(any)
No n = 2
n = 3 piano, n = 1 guitar
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Wear glasses?
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Endovascular Experience
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4 senior trainees (2 vascular surgery, 2 interventional radiology) Expert (performed >50 endovascular procedures) n = 8
n = 7 Undergraduate anatomy n= 1 Cadaver trauma course †
n = 1 PCNL course
n = 1 Advanced vascular skills course
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ACCEPTED MANUSCRIPT Table 2 – Results of the post-trial questionnaire. Candidates indicated their level of agreement with the statements on a Likert scale (1= agree strongly, 5= disagree strongly). Differences between PHCM and SVR were analysed using the Wilcoxon Matched Pairs Signed ranks test.
1.25 (±0.45) 1.50 (±0.52) 2.00 (±1.04) 2.92 (±0.90) 1.25 (±0.45) 2.00 (±0.95)
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The model was a valuable learning exercise I would recommend this model to others I would use this model again Training with this model improved my skills The model is useful for training endovascular skills I preferred training on the PHCM
2.17 (±0.72) 1.33 (±0.49) 1.50 (±0.52) 2.75 (±0.97) 1.58 (±0.67)
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P value for the difference
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Statement Compared to live patients the training model was a realistic representation of… Vascular access Manipulation of guidewire and catheter Catheterisation of vessels Performing an angiogram I found PHCM more realistic than SVR
Level of agreement (1= agree strongly, 5= disagree strongly) PHCM (mean SVR (mean ±SD) ±SD)
4.00 (±1.04) 3.08 (±0.90) 2.92 (±0.90) 2.17 (±0.58)
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1.92 (±0.51) 2.08 (±0.67) 2.83 (±0.94) 3.42 (±1.08) 2.17 (±0.58)
0.002 0.001 0.004 0.096
0.016 0.062 0.053 0.118 0.004
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Table 3 - Candidates perceived strengths and weaknesses of the PHCM model as reported in the free-text sections of the post-trial questionnaire.
Candidate
Strengths of PHCM
Weaknesses of PHCM
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Good tactile feedback
Imaging and image manipulation Very atheromatous
Absolutely realistic
Scarce resource
Scope for implanting stents/grafts
Preparation needed
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‘Discomfort’ some may cadavers for training Realistic – the patient comes with all the flaws and difficulty of real life. Tactile feedback of proper wires/catheters etc
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Life like diseased vessels
Very slow contrast washout mimics dissection Patients disease liable to become disrupted over time making it less realistic later in the day
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using
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feel
Contrast flow out not good enough Need subtraction/more usability of II
Realism
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Realistic, wires/catheters are as in-vivo
No DSA
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Useful for cannulating
Very limited use without disease
Realistic performance
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Inflexible in terms of anatomy/pathology
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Allows for manipulation
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arterial
Difficult to find cadavers with real lesions Friction is not quite natural like in a real patient Longevity Smell Aesthetics
catheter
Difficulty with angiograms (try with the pump off)
Better haptic feedback
Durability
No comment
No comment
No comment
No comment
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Table 4 - Candidates perceived strengths and weaknesses of the PHCM model as reported in the free-text sections of the post-trial questionnaire.
Candidate
Strengths of SVR
Weaknesses SVR
C1
Good imaging
No feedback Catheterisation not realistic
Excellent introductory tool for beginners to learn basic guidewire/catheter skills
A little artificial
C3
Good to establish a sequence of events to complete a task in a beginner
Unrealistic
No ethical consideration
Bit too easy
C5
Flexibility of programme
C6
No comment
C7
Good tool to learn the steps of an intervention and provides good feedback eg wall contact, screening time etc
C8
Ease of set up
Poor feedback from wires/catheters
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Haptic feedback is not very realistic and sire simulation only very limited
Cost Software glitches Less realistic Catheters/wires don’t perform the same
Clean system that does not require any set up time
Doesn’t actually allow real catheters to be used
C10
Good for sequences and steps of procedures
Limited haptic feedback
No comment
No comment
No comment
No comment
C12
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C11
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Non threatening/stress free
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Predictable – although probably a weakness as patients aren’t!
Entirely predictable responses. Poor tactile feedback. Artificial – favours a “probe and hope cos its only a machine” tendency, if not fully settled into the role play
Stays fresh all day
C4
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S0890-5096(17)30941-X
DOI:
10.1016/j.avsg.2017.07.030
Reference:
AVSG 3526
To appear in:
Annals of Vascular Surgery
Received Date: 8 May 2017 Accepted Date: 20 July 2017
Please cite this article as: Nesbitt C, Tingle SJ, Williams R, McCaslin J, Searle R, Mafeld S, Stansby G, A Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training; A Trial of Face Validity, Annals of Vascular Surgery (2017), doi: 10.1016/j.avsg.2017.07.030. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT 1
Title: A Pulsatile Fresh Frozen Human Cadaver Circulation Model for Endovascular Training; A Trial of Face Validity First author: Mr Craig Nesbitt
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Order of authors: Craig Nesbitt1, Samuel James Tingle2, Robin Williams3, James McCaslin4, Roger Searle5, Sebastian Mafeld6, Gerard Stansby7
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Author affiliations:
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1. MRCS, MD. Northern Deanery Vascular Surgical Registrar and corresponding author, Middlesbrough James Cook University Hospital, Middlesbrough.
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2. Faculty of Medical Sciences, Newcastle Medical School, Newcastle, Tyne and Wear NE2 4HH, United Kingdom.
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3. FRCR. Consultant Interventional Radiologist. Northern Vascular Centre, Department of Interventional Radiology, Freeman Hospital, Newcastle Upon Tyne.
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4. FRCS, MD. Consultant Vascular and Endovascular Surgery. Department of Vascular Surgery. Northern Vascular Centre, Department of Vascular Surgery, Freeman Hospital, Newcastle Upon Tyne.
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5. PhD. Head of School & Director of Anatomy and Clinical Skills & Director of Excellence in Learning and Teaching, Newcastle University, Newcastle Upon Tyne.
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6. FRCR. Specialty Resgistrar in Interventional Radiology. Northern Vascular Centre, Department of Interventional Radiology, Freeman Hospital, Newcastle Upon Tyne.
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7. M.A. (Catab), M.B., M.Chir, F.R.C.S. Professor of Vascular Surgery. Northern Vascular Centre, Department of Vascular Surgery, Freeman Hospital, Newcastle Upon Tyne
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Submission category: Basic Science Research (new investigations, experimental work)
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Key words: Endovascular Training, Human Cadaver, Pulsatile Model, Simulation
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Corresponding Author: Mr. Craig Nesbitt, MRCS, MD
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Address: Healeyhope Barn, Waskerley, Consett, Co Durham, DH8 9DB, UK.
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Telephone: 07969223061
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Email: [email protected]
ACCEPTED MANUSCRIPT Abstract Objectives: Determine the face validity of a pulsatile fresh frozen human cadaver model (PHCM) for
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training endovascular practitioners.
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Methods: 12 endovascular clinicians performed the same two procedures (catheterisation of the left
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renal artery and left subclavian artery) on PHCM, and Simbionix angiomentor virtual reality simulator
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(SVR). They were randomised to begin on either the PHCM or SVR. A pre-trial questionnaire
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determined participants’ endovascular experience. After training, participants rated statements
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relating to their experience on a numerical scale from 1 to 5, with 1 representing the strongest
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agreement with the statement.
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Results: When participants were asked to compare the realism of training modalities with live
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patients, PHCM scored significantly higher than SVR on statements regarding “realism of vascular
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access” (p=0.002) “guide-wire manipulation” (p=0.001) and “vessel catheterisation” (p=0.004).
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Candidates again favoured PHCM as “a valuable learning exercise” (p=0.016) and strongly favoured
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PHCM as a “useful training model” compared to SVR (p=0.004).
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Conclusions: This is the first published trial in world literature to assess the validity of a PHCM for
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training endovascular practitioners. The PHCM demonstrates good face validity when compared to
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both real patients and the SVR model, and holds exciting potential.
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Introduction
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Endovascular intervention now plays a crucial diagnostic and therapeutic role in almost all branches
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of surgery, none more so than vascular surgery where endovascular techniques have transformed
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the specialty. The key attraction of endovascular surgery is the minimally invasive nature of the
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techniques, which offers reduced morbidity and mortality when compared to their equivalent open
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procedure options.[1] For these reasons there has been a rapid increase in the number of
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endovascular procedures being performed; an American survey found a 422% increase in
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endovascular procedures logged in the casebooks of vascular trainees between 2001 and 2007.[2]
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ACCEPTED MANUSCRIPT The explosion in therapeutic endovascular treatment options has resulted in a great need to tackle
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the issue of training endovascular skills for the practitioners of the future. This need is further
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intensified by the fact that endovascular surgery requires a different set of technical and cognitive
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skills, when compared to open surgery.[3] Indeed, operating in a three dimensional field from a two
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dimensional view, altered haptics and emphasis on hand-fluro-eye co-ordination are all challenging
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skills to master.[4]
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One attempt to fulfil this training need is the use of medical simulators. Simulation is now utilised
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widely in all branches of surgery, especially for the training of minimally invasive techniques. There
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are now a number of high fidelity endovascular simulators available, which use computer-generated
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images of the human vasculature to allow trainers the ability to interact with the model using an
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interface device.[5]
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Virtual reality has promise for both objectively demonstrating procedural competence,[3] and for
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delivering effective training of novices, with a recent face validity trial supporting its use.[6] Whilst
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virtual reality is now becoming integrated into endovascular training across Europe and America, it is
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not without its limitations. Simulators lack the tactile feedback found in real patient vessels, are
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unable to simulate arterial puncture, and units cost in excess of £100,000. In addition, conclusive
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evidence remains poor as to their exact benefit, with a 2006 systematic review failing to
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demonstrate a firm advantage from expensive high-fidelity surgical simulators.[7]
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The last decade has also seen an increasing number of human cadaveric (HC) based workshops in
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higher surgical training.[8] The suitability of HC for training open vascular surgical procedures is
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recognised,[9] and cadaveric perfusion to enhance open vascular surgery is also reported.[10] Garret et
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al described a technique for creating isolated pulsatile segments in a HC model,[11] and the use of
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cadavers for stent graft development has also been reported.[12-14] However, there is a lack of
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literature investigating the use of HC for endovascular training, despite the increased use of HC for
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training in other fields.
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ACCEPTED MANUSCRIPT We recently published a technical note detailing a method for establishing a pulsatile fresh-frozen
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human cadaver model (PHCM), which has potential to be used for endovascular training.[15] While
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this technical note demonstrates the feasibility of the model, further research is needed to validate
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the model as a useful and effective tool for training.
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Face validity is a simple form of validity, where participants judge the degree of resemblance
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between a model and a real-life situation.[16] In the context of the present study this involves
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endovascular experts comparing a training model with a real endovascular procedure. The aim of
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this trial was to establish if the PHCM demonstrated face validity comparing it to both real live
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patients, and to a high fidelity virtual reality simulator.
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Methods
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Vascular surgeons, radiology, cardiology and neurology interventionalists with endovascular
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experience were recruited to take part in the trial, as practitioners who perform endovascular
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procedures (on live patients) on a daily basis were considered to be the best judges of the model’s
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realism and suitability for training.
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Details of the PHCM model evaluated in this trial has been previously published as a technical note
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in this journal.[15] Briefly, this model uses a pulsatile blood pump (1405 Harvard Apparatus™,
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Massachusetts, USA) to perfuse a fresh frozen cadaver, with inflow through the right common
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carotid artery and outflow through the left common femoral and right superficial femoral arteries. In
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order to gain some perspective on the PHCM as a training model, a comparative training experience
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on a high fidelity virtual reality simulator, Simbionix ™ angiomentor (SVR), was included in the trial’s
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design.
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Each participant performed two index procedures on both training models. Procedure 1 involved
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cannulation of the left renal artery and confirmatory angiogram from access in the right femoral
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artery, and procedure 2 involved cannulation of the right subclavian artery and confirmatory
ACCEPTED MANUSCRIPT angiogram from access in the right femoral artery; representing simple and intermediate procedures
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respectively. Candidates were randomised, using a closed envelope system, both to which training
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model to use first, and to which procedure to perform first.
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Formal ethical approval was not required as it was deemed that the proposed trial represented
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‘technical development and training’.
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Questionnaires
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Before candidates began training they completed a pre-trial questionnaire to determine certain
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candidate demographics; level of seniority, endovascular experience, previous exposure to both
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human cadaver and VR simulators, handedness, musical instrument experience, exposure to video
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games, and use of correctional glasses. Those participants who had performed >50 procedures were
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considered expert.
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After completing both procedures on both models, candidates completed a post-trial questionnaire.
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This questionnaire asked candidates to rate their agreement with a series of statements regarding
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their experience training on both the SVR and PHCM. Candidates’ agreement with these statements
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was recorded on a standard Likert scale with ‘1’ representing their greatest agreement and ‘5’ their
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greatest disagreement with the statement. In addition, free-text boxes allowed candidates to
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comment on the strengths and weaknesses of each model.
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Statistical analysis
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Statistical analysis was undertaken using the Statistical Package for the Social sciences version 19
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(SPSS, Chicago). Wilcoxon Matched Pairs Signed ranks test was used to compare questionnaire
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statements from the two simulators. A p-value of <0.05 was considered to be significant. Results are
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displayed as mean (± SD).
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Results
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In total, 12 participants were recruited to the study. Of these, there were; 5 consultant radiologists,
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3 consultant endovascular surgeons and 4 senior trainees (2 vascular surgery, 2 interventional
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radiology). Additional demographic information for the candidates can be found in Table 1.
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All candidates completed both index procedures in the SVR, with no noted procedural or technical
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complications. All participants completed index procedure 1 on the PHCM, however four
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participants failed to complete index procedure 2 (cannulation of the right subclavian artery and
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confirmatory angiogram) on the PHCM. This was partly due to candidates’ level of experience, but
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also due to extensive atheromatous disease in the aorta, making cannulation of the subclavian
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artery challenging even for the most experienced consultant operators.
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Mean Likert scores for the various questions on the post-trial questionnaire can be found in Table 2.
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When comparing the realism PHCM to live patients the mean Likert scores were all less than three;
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this indicates that participants agreed that the PHCM represents a high fidelity model. Participants
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strongly agreed that using the PHCM was a valuable learning experience (1.25 (±0.45)), and that the
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model is useful for training endovascular skills (1.25 (±0.45)).
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Applying the Wilcoxon Matched Pairs Signed ranks test to compare the Likert scores revealed several
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significant differences between PHCM and SVR (Table 2). Comparing the fidelity of the models
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candidates showed a significant preference for PHCM concerning vascular access (p=0.002),
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manipulation of guidewires (p=0.001), and catheterization of vessels (p=0.004). Candidates also felt
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the PHCM was a more useful training model compared to SVR (p=0.004).
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The final section on the post-trial questionnaire provided free-text boxes, for participants to
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comment on the strengths and weaknesses of the two models. Comments relating to perceived
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strengths and weaknesses for PHCM can be found in Table 3, and similar information relating to SVR
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can be found in Table 4. These will be explored in the following discussion.
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Discussion
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In the present trial, PHCM [15] was compared in a controlled environment under standard conditions,
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to both live patients and a SVR, through the opinion of endovascular experts. Overall, candidates
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were impressed with both the fidelity and training potential of the PHCM (mean scores <3; Table 2).
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Compared to a widely used virtual reality simulator, candidates preferred training on the PHCM
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(2.00 (±0.95)), and also found it to be more realistic (1.58 (±0.67)); Table 2.
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PHCM scored significantly higher than SVR on individual statements regarding realism, including
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vascular access (p=0.002), manipulation of the guidewire and catheter (p=0.001), and
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catheterisation of the vessels (p=0.004); Table 2. This was also apparent in candidates’ free-text
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comments about the PHCM: “it felt like a patient that needed treating with respect”,
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“wires/catheters are as in vivo” and “absolutely realistic” (Table 3). In contrast candidates’
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commented that SVR was “a little artificial” with “entirely predictable responses, poor tactile
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feedback”, and “limited haptic feedback” (Table 4).
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The only feature of PHCM that scored less well when compared SVR was that of the realism of
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performing an angiogram (2.75 (±0.97)), although this was not significant (p=0.096). This was in
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agreement with several comments made by the candidates on their post-trial questionnaires (Table
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3), indicating they did not find performing an angiogram in the HC comparable to live patients. For
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example one candidate felt the washout of contrast was slow, and this mimicked dissection.
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This observation was due to heavy atheromatous disease in the cadaver, which caused resistant
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residual thrombus that subsequently exacerbated the problem of residual contrast post angiogram.
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This remains a disadvantage of the PHCM versus the more predictable training experience of SVR. In
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fact, the severity of disease in the HC resulted in difficulty in cannulating the right subclavian artery;
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not all expert candidates were successful in completing this task in the allotted time.
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ACCEPTED MANUSCRIPT Whilst the use of human cadavers is increasing in other fields of surgical training,[8] this is the first
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study to attempt validation of a human cadaver model in the field of endovascular training. The
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methodology used in this study is similar to that which has been adopted in many trials of both
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laparoscopic and cadaveric training, when trialists wished to gauge a simple measure of their
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models’ validity. [9, 17-19]
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It is important to acknowledge the limited use of both models in the trial, as both were just used to
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simulate angiography. SVR is able to simulate unlimited numbers of angioplasty and stent
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implantation scenarios in a standard format. Angioplasty and stent deployment is possible in the
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PHCM, but not in a repeatable or standardized format. This remains a limitation of PHCM, and its
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effect on candidate’s opinions in the present study is acknowledged.
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A number of candidates criticised the radiology equipment capabilities of the PHCM (Table 3). In
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contrast SVR is capable of subtraction II, 3D reconstruction and road mapping. However, with
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investment more sophisticated radiology equipment could easily be incorporated to enhance the
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PHCM training experience. The limitation of the equipment made available during this trial is
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acknowledged.
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Finally, it is almost impossible to predict the state of a cadaver’s vessels prior to training, unless
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there is a history of PVD or clinical evidence of arterial disease. Despite these apparent limitations,
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candidates overall favoured their training experience on PHCM (2.00 (±0.95)).
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Conclusion
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Overall, it is concluded that PHCM demonstrated face validity. PHCM represents a feasible
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endovascular training model with a high degree of realism, and compares favourably to both live
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patients and high fidelity virtual reality simulation for a simple angiogram procedure. Further trials
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are necessary to establish the model’s construct validity and true efficacy as a successful training
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model for endovascular practitioners.
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Acknowledgments The authors would like to thank the staff of the Newcastle Surgical Training Centre for their support throughout the project, Medtronic Ltd for their generous educational grant and the radiology department of the Freeman Hospital for their expertise.
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Conflict of Interest
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Declaration of Funding
The authors declare a £2000 educational grant from Medtronic Ltd. This was donated to part fund the original purchase of the pulsatile pump. We can confirm that Medtronic had no further role in this or any subsequent trials
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References
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1. Van Herzeele I. Virtual Reality Endovascular Simulation: Ready for Training. Nautilus Academic Books. 1st ed. 2009. 2. Schanzer A, Steppacher R, Eslami M, Arous E, Messina L, Belkin M. Vascular Surgery Training Trends From 2001-2007: A Substantial Increase in Total Procedure Volume is Driven By Escalating Endovascular Procedure Volume and Stable Open Procedure Volume. Journal of Vascular Surgery 2009; 49(5) 1339-1344. 3. Neequaye SK, Aggarwal R, Van Herzeele I, Darzi A, Cheshire N. Endovascular Skills Training and Assessment. Journal of Vascular Surgery 2007;46:1055-64. 4. Berger P, Willems MCM, Van Der Vliet JA, Schultze Kool LJ, Bergqvist D, Blankensteijn JD. Validation of the Simulator and Rating Endovascular SkillS (STRESS)-machine in a setting of competence testing. Journal of Cardiovascular Surgery. 2010; 51: 253-256. 5. Satava RM. Virtual reality surgical simulator – the first steps. Surg Endosc Ultrasound Intervent Tech. 1993; 7: 203-205. 6. 72.74. Lonn L, Edmond J, Marco J, Kearney P, Gallagher A. Virtual Reality Simulation Training in a High-Fidelity Procedure Suite: Operator Appraisal. Journal of Vascular and Interventional Radiology 2012; 23 (10): 1361-1366. 7. Sutherland LM, Middleton PF, Anthony A, Hamdorf, J, Cregan P, Scott D, Maddern GJ. Surgical simulation: a systematic review. Annals of Surgery. 2006; 243: 291-300. 8. Gilbody J, Prosthofer AW, Ho K, Costa ML. The use and effectiveness of cadaveric workshops in higher surgical training: a systematic review. Ann R Coll Surg Engl 2011; 93: 347-352. 9. Reed AB, Crafton C, Giglia JS, Hutto JD. Back to basics: Use of fresh cadavers in vascular surgery training. Surgery 2009;146:757-63. 10. Aboud E, Moursi M. Live Cadavers for Laboratory Training in Vascular Surgery. Journal of Vascular Surgery 2010. 51: 46S-S. 11. Garrett HE Jr. A human cadaveric circulation model. Journal of Vascular Surgery 2001;33:1128-30. 12. Linsen MAM, Vos AWF, Diks J, Rauwerda JA, Wisselink W. Modular Branched Endograft System for Aortic Aneurysm Repair: Evaluation in a Human Cadaver Circulation Model. Journal of Vascular and Endovascular Surgery 2007;41(2)126-29. 13. Arbateli H, Cikirikcioglu M, Pektok E, Walpoth BH, Fasel J, et al. Dynamic Human Cadaver Model for Testing the Feasibility of New Endovascular Techniques and Tools. Ann Vasc Surg 2010;24: 419-22.
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The authors declare no conflicts of interest.
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14. Jongkind V, Yeung KK, Linsen MAM, Heidsieck D, Coveliers HME, Hoksbergen AWJ, et al. Direct Videoscopic Appraoch to the Thoracic Aorta for Aortic Endograft Deliver: Evaluation in a Human Cadaver Circulation Model. Journal of Endovascular Therapy 2010;12:12-18. 15. C, N., et al., Design of a Pulsatile Fresh Frozen Human Cadaver Circulation Model For Endovascular Training. Annals of Vascular Surgery. 16. Schreuder, H.W., et al., Face and construct validity of virtual reality simulation of laparoscopic gynecologic surgery. Am J Obstet Gynecol, 2009. 200(5): p. 540 e1-8. 17. Supe A, Dalvi A, Prabhu R, Kantharia C, Bhuiyan P. Cadaver as a model for laparoscopic training. Indian Journal of Gastroenterology. 2005; 24: 111-113 18. Wadman MC, Lomneth CS, Hoffman LH, Zeger WG, Lander L, Walker RA. Assessment of a New Model for Femoral Ultrasound-guded Central Venous Access Procedural Training: A Pilot Study. Academic Emergency Medicine 2010;17: 88-92 19. Eisma R, Mahendran S, Majumdar S, Smith D, Soames RW. A comparison of Theil and formalin embalmed cadavers for thyroid surgery training. The Surgeon. 2011; 9(3): 142-146.
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Tables Table 1 - Candidate demographics. † PCLN: Cadaveric Percutaneous Nephrolithotomy Course.
Deomgraphic
Candidate
Seniority
5 consultant radiologists 3 consultant endovascular surgeons
Intermediate n = 4 Yes n = 3 No n = 9
Handedness
Left n = 0 Right n = 12
Play musical instrument
Yes n = 4 No n = 8
Play video games regularly
Yes n = 4 No n = 8
Previous VR training
Yes n = 10 No n = 2
Previous cadaver
Yes n = 0 No n = 12
endovascular training Previous cadaver training
Yes n = 10
(any)
No n = 2
n = 3 piano, n = 1 guitar
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Wear glasses?
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Endovascular Experience
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4 senior trainees (2 vascular surgery, 2 interventional radiology) Expert (performed >50 endovascular procedures) n = 8
n = 7 Undergraduate anatomy n= 1 Cadaver trauma course †
n = 1 PCNL course
n = 1 Advanced vascular skills course
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ACCEPTED MANUSCRIPT Table 2 – Results of the post-trial questionnaire. Candidates indicated their level of agreement with the statements on a Likert scale (1= agree strongly, 5= disagree strongly). Differences between PHCM and SVR were analysed using the Wilcoxon Matched Pairs Signed ranks test.
1.25 (±0.45) 1.50 (±0.52) 2.00 (±1.04) 2.92 (±0.90) 1.25 (±0.45) 2.00 (±0.95)
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The model was a valuable learning exercise I would recommend this model to others I would use this model again Training with this model improved my skills The model is useful for training endovascular skills I preferred training on the PHCM
2.17 (±0.72) 1.33 (±0.49) 1.50 (±0.52) 2.75 (±0.97) 1.58 (±0.67)
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P value for the difference
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Statement Compared to live patients the training model was a realistic representation of… Vascular access Manipulation of guidewire and catheter Catheterisation of vessels Performing an angiogram I found PHCM more realistic than SVR
Level of agreement (1= agree strongly, 5= disagree strongly) PHCM (mean SVR (mean ±SD) ±SD)
4.00 (±1.04) 3.08 (±0.90) 2.92 (±0.90) 2.17 (±0.58)
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1.92 (±0.51) 2.08 (±0.67) 2.83 (±0.94) 3.42 (±1.08) 2.17 (±0.58)
0.002 0.001 0.004 0.096
0.016 0.062 0.053 0.118 0.004
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Table 3 - Candidates perceived strengths and weaknesses of the PHCM model as reported in the free-text sections of the post-trial questionnaire.
Candidate
Strengths of PHCM
Weaknesses of PHCM
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Good tactile feedback
Imaging and image manipulation Very atheromatous
Absolutely realistic
Scarce resource
Scope for implanting stents/grafts
Preparation needed
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‘Discomfort’ some may cadavers for training Realistic – the patient comes with all the flaws and difficulty of real life. Tactile feedback of proper wires/catheters etc
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Life like diseased vessels
Very slow contrast washout mimics dissection Patients disease liable to become disrupted over time making it less realistic later in the day
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using
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feel
Contrast flow out not good enough Need subtraction/more usability of II
Realism
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Realistic, wires/catheters are as in-vivo
No DSA
C7
Useful for cannulating
Very limited use without disease
Realistic performance
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Inflexible in terms of anatomy/pathology
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Allows for manipulation
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arterial
Difficult to find cadavers with real lesions Friction is not quite natural like in a real patient Longevity Smell Aesthetics
catheter
Difficulty with angiograms (try with the pump off)
Better haptic feedback
Durability
No comment
No comment
No comment
No comment
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Table 4 - Candidates perceived strengths and weaknesses of the PHCM model as reported in the free-text sections of the post-trial questionnaire.
Candidate
Strengths of SVR
Weaknesses SVR
C1
Good imaging
No feedback Catheterisation not realistic
Excellent introductory tool for beginners to learn basic guidewire/catheter skills
A little artificial
C3
Good to establish a sequence of events to complete a task in a beginner
Unrealistic
No ethical consideration
Bit too easy
C5
Flexibility of programme
C6
No comment
C7
Good tool to learn the steps of an intervention and provides good feedback eg wall contact, screening time etc
C8
Ease of set up
Poor feedback from wires/catheters
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Haptic feedback is not very realistic and sire simulation only very limited
Cost Software glitches Less realistic Catheters/wires don’t perform the same
Clean system that does not require any set up time
Doesn’t actually allow real catheters to be used
C10
Good for sequences and steps of procedures
Limited haptic feedback
No comment
No comment
No comment
No comment
C12
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C11
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Non threatening/stress free
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Predictable – although probably a weakness as patients aren’t!
Entirely predictable responses. Poor tactile feedback. Artificial – favours a “probe and hope cos its only a machine” tendency, if not fully settled into the role play
Stays fresh all day
C4
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C2