Background Tissue swelling in simulation models is usually achieved by inflating a balloon with air or water. Obviously this method would not work where swelling associated by injection of fluid is desired. Animal tissue has been used to create this effect, with all the associated problems attached to its use. We sought to avoid this by exploring the possibility of creating a construct than can simulate swelling successfully.
Methodology We firstly determined the properties we required: immediate total fluid absorption of up to 5× its volume with no leakage, swelling to spread visually and geometrically like in human tissue, emulating the same fluid dynamics, appearance and consistency to touch. Various materials were tested and the most suitable was identified as well as the most effective way of incorporating it in a simulation phantom. It was then evaluated.
Results Hydrocolloid impregnated in microfibers used in disposable nappies (HIMN) was found to be eminently suitable. A subcutaneous tissue analogue (thick layer specimen) was constructed by wrapping partially hydrated HIMN in ADAMgel (Aqueous Dietary fibre Antifreeze Mix gel) film and incorporated in a caudal epidural simulation phantom. During this procedure a hand is placed over the injection site to evaluate incorrect placement of local anaesthetic by detecting subcutaneous extrasacral swelling. Universally positive evaluations were presented and published.1 Vocal cords analogues (thin layer specimen) were made using the same method, using HIMN that had the air removed either by compression or aspiration. This was evaluated by the Simulation Lead of the Otolaryngology Royal College (who has been unsuccessfully searching for a swelling vocal cord model for some years), and found to meet all his expectations.
Conclusion Encasing HIMN in ADAMgel satisfied all the criteria we required for successful swelling simulation.
Fraser K, Willers J, Jenkins C, Wanigasinghe N, Uncles D. Developing a phantom model for caudal anaesthesia. Anaesthesia 2014;69:17
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