Ovine model as a surgical simulator for pediatric laryngotracheal reconstruction. S. Hartmann, S. Ranguisa, A.T. Chenga,b. aChildren's Hospital at Westmead ...
Ovine model as a surgical simulator for pediatric laryngotracheal reconstruction S. Hartmann, S. Ranguisa, A.T. Chenga,b Hospital at Westmead Australia, bDiscipline of Child and Adolescent Health, University of Sydney, Australia
Introduction Provision of procedural experience for surgical residents is becoming increasingly important. Subspecializa:on in teaching hospitals results in more complex problems and larger caseloads demanding surgeons to operate at op:mal efficiency without interrup:ons.1 Furthermore, restric:ons to training :mes such as limita:ons on trainee work hours has reduced the :me available to learn difficult opera:ons.1 Laryngotracheal reconstruc:on (LTR) is a procedure not regularly encountered by the otolaryngology resident. At the Children’s Hospital at Westmead the procedure is performed an average of six :mes annually and is performed by the supervising consultant and their fellow.2 Using a surgical simulator to learn LTR may enhance residents’ understanding of the procedure and foster an interest in pediatric airway surgery. Ex vivo anatomic sec:ons from euthanased animals have been used effec:vely to provide procedural training and have been validated for use in otolaryngology training programs.1,3 This paper reports on the design and valida:on of a laryngeal surgical simulator to teach pediatric laryngotracheal reconstruc:on at a ter:ary pediatric center.
Methods The model development and prospec:ve valida:on was conducted at the Children’s Hospital at Westmead, a ter:ary referral pediatric center between September 2016 and May 2017. Permission was obtained from the Kids Research Ins:tute to conduct the study in the research laboratory. Ex vivo knee-high lamb specimens were sourced from an Australian fully accredited abaSoir and stored frozen and sealed in the research unit. The en block specimens included the structures of the neck, cervical spine and cutaneous :ssue extending from above the thyroid car:lage down to the first tracheal division. Prior to use, the specimens were thawed over a period of fiieen minutes and posi:oned using drapes to emulate the surgical exposure. Each candidate was asked to perform two LTRs using the ovine model. The simula:ons were video recorded to enable subsequent assessment and scoring by the senior author (Vid 1). The assessor was blinded to the candidates performing the surgery. To test prospec:ve valida:on, global ra:ng scales, surveys and technical checklists were recorded for residents, registrars, fellows and consultant pediatric ENT surgeons undergoing the simula:on. In order to assess the difficulty of the procedure, candidates were classified as being advanced, those who had assisted in more than three live laryngotracheal reconstruc:ons, and novice, those who had been involved in three or less procedures. Student t-test was performed to determine the difference in performance due to surgical experience. Intraclass correla:on coefficient (ICC) was calculated to determine the consistency in the simula:on model to provide an assessment of surgical ability. The Cronbach alpha coefficient was used to determine the reliability of the global ra:ng scale and procedure checklist ra:ng tools. Further correla:on of the global ra:ng scale with the procedure checklist tools was calculated using the Pearson R coefficient. The percep:on of the model was assessed using anonymous post-simula:on surveys using 5-point Likert scales which ranged from 1 (strongly disagree) to 5 (strongly agree). Sta:s:cs were calculated using Excel for Mac 2011, Version 14.5.4 with the Real Sta:s:cs Resource Pack for Excel 2011 add-in.
Results
Demography of candidates
Fig1. Global Ra:ng Scales
35
25
30
16
No. of par:cipants
8
20
Male, %
75
15
Female, %
25
10
25 20 15 10
5 Mean par:cipant age, y
33.4
Consultants, %
12
Fellows, %
12
Registrars, %
38
Residents, %
38
Fig2. Procedural Checklist Scores
30
No. of procedures
5
0
0 Advanced
Novice
Advanced
Novice
Fig3. Correla:on between assessment criteria (Pearson R = 0.88)
40 Procedural Checklist Score
aChildren’s
35 30
25 20 Performance by advanced candidates was 15 sta:s:cally superior to novice candidates 10 undertaking the simula:on of the procedure 10 15 20 25 30 35 40 (Fig1 and 2). The global ra:ng scale was Global Rating Scale significantly higher in the advanced group Vid 1. Sample video of LTR ovine simulator compared to the novice group (mean of 25.9 [SD 3.6] versus mean of 18.6 [SD 3.7], p= 0.002). Likewise, the procedural checklist score was significantly rated more highly in the advanced group compared to the novice croup (mean of 29.8 [SD 4.6] versus mean of 21.5 [SD 3.3], p= 0.001). These results validate the difficulty of the procedure challenging the operator at different levels of training. It suggests that candidates with more experience with laryngotracheal reconstruc:ons perform beSer on the ex vivo ovine model. The face validity as assessed by the Likert scale ques:onnaires demonstrate the percep:on that the surgical model was realis:c, a posi:ve learning experience and useful in its real surgery applica:on (means ranging from 4-5). The dura:on of the procedure was on average 29 minutes and 22 seconds. Interes:ngly, there was no sta:s:cally significant difference in :me taken comparing advanced and novice candidates and on average advanced candidates took more :me for the procedure (31 minutes and 22 seconds compared to 27 minutes and 4 seconds, p= 0.33). The ICC used to determine the consistency of the assessments was 0.70 sugges:ng a high degree of correla:on between the first and second opera:ons. The reproducibility of the assessment criteria demonstrated a Cronbach alpha coefficient of 0.83 for the procedural checklist assessment and 0.79 for the global ra:ng scales. This iden:fies the criteria as providing a high level of reproducibility. The correla:on of the global ra:ng scale and the procedure checklist demonstrated a Pearson R coefficient of 0.88 indica:ng a high level of correla:on (Fig 3).
Compara(ve anatomy of the airway of ovis aries Similari'es: Cricoid has typical signet ring appearance, with long lamina and narrow arch Different: Indis:nct oblique line of thyroid car:lage, high vaulted vocal cords, large arytenoids
Conclusion Given the complexity of airway surgery, there is a significant benefit of training on a simulator to improve laryngotracheal reconstruc:on technique. The ovine airway provides for a realis:c surgical simulator that mimics the pediatric airway anatomy in both propor:on and size. Our prospec:ve study demonstrated validity of the ra:ng scales used for the procedure allowing them to be applied as an assessment of technical competence for use in our training program.
References 1. Dawe S, Windsor J, Cregan P, HeweS P, Maddern G. Surgical simula:on for training: skills transfer to the opera:ng room (update). ASERNIP-S report no. 80. Adelaide, South Australia: ASERNIP-S, November 2012 2. Chan LS, Daniel M, Boardman SJ, Cheng AT. Laryngotracheal stenosis and airway surgery – An outcomes based approach. Interna:onal Journal of Pediatric Otorhinolaryngology 78 (2014) 1931-1936 3. Dedmon MM, Paddle PM, Phillips J, Kobayashi L, Franco RA, Song PC. Development and valida:on of a high-fidelity porcine laryngeal surgical simulator. Otolaryngology – Head and Neck Surgery 153 (2015)420-426 4. Hast M, Malmgren L, Larson C. Compara:ve Anatomy of the Larynx: Evolu:on and Func:on. Vocal Fold Physiology: Biomechanics, Acous:cs and Phonatory Control. Denver Center for the Performing Arts, Inc 1985 Denver, Colorado 5. Saber, AS. The car:lages of the larynx of the one-humped camel (camelus dromedaries) and sheep (ovis aries) Zbl. Vet. Med. C, Anat. Histol. Embryol. 12, 77-84 (1983)
