THEORETICAL AND EXPERIMENTAL BASIS FOR THE DEVELOPMENT OF A DYNAMIC AIRWAY STENT

Three major problems are currently associated with airway stents: muco stasis, formation of granulation tissue, and migration. We wanted to d etermine whether these problems could be solved by a different stent d esign. Based on theoretical considerations of an idealized trachea, we developed a dynamic bifurcation stent made of silicone which incorpor ates horseshoe-shaped steel struts. A flexible posterior membrane enab les dynamic compression during cough, whilst the clasps maintain the a irway lumen in the face of external compression. The design of the ste nt cast was based upon computed tomographic (CT)-scan studies of the c entral airways. Its complex shape provides a smoother distribution of pressure on the mucose; thereby, lowering the stimulus for granulation formation. The bronchial limbs saddle on the carina, preventing displ acement. The mechanical behaviours of the new stent and two commercial ly available stents were compared in an ex-vivo model, utilizing fresh ly excised tracheae and new visualization techniques. Dynamic (artific ial coughs) and static loads (simulating tumour compression or pleural pressures) were applied on excised human tracheae with different sten ts. Our dynamic stent preserved effective compression of the posterior membrane in response to cough, and also provided lumen stability agai nst extrinsic compression. In comparison, the two commercially availab le stents did not provide both functions equally well. In conclusion, our newly designed dynamic bifurcation stent shows characteristics whi ch should prove useful in avoiding problems currently associated with airway stents.