published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy

Thesis (M. Phil.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

In the UK, there are up to 3,000 cancer patients who have undergone total laryngectomy and use voice prostheses (VPs), for speech rehabilitation. VPs are inserted between the eosphagus and trachea to provide a 'voice' but, as with other semi-in-dwelling devices, such as nasal and gastric tubes, they invariably fail due to occlusion by microbial biofilms. The requirement for frequent replacement is financially costly to the NHS and impacts patient well-being. Replacement frequency varies by patient, from 7 weeks to 6 months but the reasons for this variation are not clearly understood. By designing and implementing a study of microbial colonisation of VPs and oral rinse samples submitted by 14 Speech and Voice Clinic patients over 13 months, this study explored whether specific microbes or patient factors, including the use of antacids, antibiotics and nystatin, along with denture-use, were potential predictors of device longevity. Focussing on the role of the commonly isolated fungi, we sought to understand the role of diet or the presence of the bacterium, S. aureus, in biomass accumulation. We also asked whether biofilm regulation pathways are shared across the fungi and could constitute a potential target for therapeutics. Microbial isolation from 66 VPs showed the predominant species as described in previous studies, but each participant had a unique profile which persisted over time, with half of the microbes originating from the oral flora. Clinic-based participants experienced fewer problems, primarily due to the device type used, and carried fewer species of Gram negative bacteria than the long term users. Statistical analysis showed that patient medication influences biofilm composition and dietary sugars differentially affect biomass formation. In vitro experiments showed that the ability to treat Candida biofilms with nystatin was improved in the presence of S. aureus. Expression analysis showed that regulation of biofilms in C. parapsilosis was the closest to that of C. albicans but that the extent of protein homology to C. albicans regulators was not a predictor of expression levels. It is therefore unlikely that a single therapeutic could be developed to target biofilm gene regulation. This work provides new insights into the complexity of biofilm formation in voice prosthesis users but reveals associations between microbes, diet, prosthesis type and medications that might be used to advise patients and help to reduce the stress and cost of frequent device failure and replacement.

No description available.

Laryngectomy, as a treatment for malignant laryngeal lesions, requires the patient to seek a substitute method of producing speech. Three types of alaryngeal speech were described: esophageal, Asai, and artificial larynx. One consideration in deciding which mode of speech is best for the patient is how closely each type of alaryngeal speech approximates normal. This investigation was an objective examination of esophageal, Asai, and artificial larynx speech as compared with normal in males and females.

Objectifs : Ce travail a pour but de développer un larynx artificiel composé de 2 structures : 1) une structure inamovible en titane poreux prolongeant la trachée; 2) une double valve remplissant la fonction de sphincter. Matériels et Méthodes : L’intégration de la prothèse en remplacement trachéal a été testée in vitro et in vivo sur les modèles animaux rats, lapins et brebis. Suite à l’ensemble de ces résultats, nous avons réalisé la première application clinique du larynx artificiel. Résultats : 1) L’ajout d’un tube de silicone endoprothétique améliore la survie chez le gros animal; 2) l’intégration tissulaire de la prothèse de trachée associée à un matériel polymérique biodégradable était supérieure à celle des prothèses en titane poreux nu; 3) la vitesse de colonisation des prothèses en titane poreux était accélérée lorsque l’on diminuait la taille des billes. Un premier patient a été implanté avec une prothèse de larynx artificiel avec des résultats satisfaisants à 9 mois. Conclusions : Nos études concernant l’intégration de prothèses de trachées in vitro et in vivo ont permis de contribuer à l’aboutissement de la première application clinique de larynx artificiel. / Background: The aim of this work is the design of an artificial larynx made of 2 elements: 1) a non-removable bio-integrable structure designed to provide a connection with the remaining trachea; 2) a double valve that fulfills the sphincter function. Materials and Methods: In vitro and in vivo tests (rat, rabbit and sheep model) were performed to achieve the tracheal prosthesis integration. Following all these results, we carried out the first clinical application of an artificial larynx. Results: i) The long-term survival of the animals was improved when an endoprosthetic silicon calibration tube was used; ii) tissue integration of the prostheses in porous titanium filled with biodegradable polymer was better than the bare porous titanium; iii) prosthesis integration was improved when pore size was decreased. A first patient was implanted with an artificial functional larynx with satisfactory results after 9 months of implantation. Conclusion: The whole in vivo and in vitro studies concerning the integration of the tracheal prosthesis has contributed to the success of the first clinical application of the artificial larynx.