Theoretical and experimental basis for the development of a dynamic airway stent

Abstract

Three major problems are currently associated with airway stents: mucostasis, formation of granulation tissue, and migration. We wanted to determine whether these problems could be solved by a different stent design. Based on theoretical considerations of an idealized trachea, we developed a dynamic bifurcation stent made of silicone which incorporates horseshoe-shaped steel struts. A flexible posterior membrane enables dynamic compression during cough, whilst the clasps maintain the airway lumen in the face of external compression. The design of the stent cast was based upon computed tomographic (CT)-scan studies of the central airways. Its complex shape provides a smoother distribution of pressure on the mucosa; thereby, lowering the stimulus for granulation formation. The bronchial limbs saddle on the carina, preventing displacement. The mechanical behaviours of the new stent and two commercially available stents were compared in an ex-vivo model, utilizing freshly excised tracheae and new visualization techniques. Dynamic (artificial coughs) and static loads (simulating tumour compression or pleural pressures) were applied on excised human tracheae with different stents. Our dynamic stent preserved effective compression of the posterior membrane in response to cough, and also provided lumen stability against extrinsic compression. In comparison, the two commercially available stents did not provide both functions equally well. In conclusion, our newly designed dynamic bifurcation stent shows characteristics which should prove useful in avoiding problems currently associated with airway stents.

Customization of stent design for treating malignant airway stenosis with the aid of three-dimensional printing

“…The angle of the carina in the airway is not static, and it changes 10° or more with breathing movements and different postures in a normal person (14). In particular, for patients with malignant tumors involving the airway, a 20°-30° change in the angle of the carina should be considered due to the compression on the airway caused by the malignancy (13). In addition, for such patients, stent migration may occur due to tumor shrinkage after tumorspecific therapy (34).…”

“…However, no studies have focused on the treatment of malignant stenosis around the carina or bronchi with metallic stents customized by 3D printing. It should be noted that the angle between the two main bronchi may vary in patients with tumor compression or during respiration (13,14). Therefore, we designed a new segmented airway stent with a changeable angle between these two branches to fit the dynamic changes of the carina angle.…”

Tracheobronchial stents: an expanding prospect

“…28 Freitag developed the Dynamic Y stent (Boston Scientific Corporation, Natick, MA), which was composed of silicone embedded with anterolateral horseshoe-shaped steel struts, attempting to mimic the anatomical properties of the trachea. 29,30 Deployment was complex and performed via laryngoscope or rigid bronchoscope with specially designed introducer forceps. 31 The stent demonstrated considerable promise when first created 32 ; however, it has been discontinued globally, most likely due to difficulty with insertion.…”

Investigation on forced vibration characteristics of Nitinol tracheal stent

“…The results showed that the airway deformation caused by tracheal movement significantly affects the stent's mechanical properties. Freitag et al [ 14 ] conducted dynamic and static load simulation on isolated human trachea with a stent to study the stent's stability in trachea deformation. In the field of studying the nonlinearity and shedding mechanism of Ni–Ti alloy stents, Guo et al [ 15 ] established the nonlinear dynamic response of shape memory alloy tracheal stents by considering the influence of random excitation, such as random radial pressure.…”