Many silicone stents are commercially available, although the Dumon stent (Tracheobronxane®, Novatech, La Ciotat, France) remains the reference standard as it is the most commonly placed stent worldwide. There are two specific designs: straight and Y (for disease involving the carina, to be treated in another chapter of this book). Stents are available in various lengths and diameters to accommodate both paediatric and adult indications (Fig. 29.2). The largest available external diameter is 20 mm. For irregularly shaped stenoses, i.e. those with marked reduced central airway calibre as compared to the extremities, specialised hourglass-shaped stents are available (Fig. 29.2). These hourglass-shaped stents are particularly useful in cases of short benign tracheal disease. The currently available stents are either made of transparent silicone (non-radio-opaque) or made of silicone melted with barium sulphate (white colour) (radio-opaque) (Fig. 29.2). Soon, the new generation of transparent Dumon silicone stents (Tracheobronxane®, Novatech, La Ciotat, France) will have gold markers included in their studs to provide radio-opacity. The transparent Dumon stent offers the possibility to visualise the mucosa behind its wall.

Dumon stents can be inserted in many different ways. Ideally, it is inserted through a dedicated rigid bronchoscope even if it is feasible using a flexible scope.

The commercialised introducer set includes a loading tool and a pusher (Fig. 29.3). A Dumon stent can be repositioned, removed and replaced at any time with ease using standard grabbing forceps. On-site modification of these stents is technically possible (Fig. 29.4).

The Polyflex stent (Boston Scientific, Natick, MA, USA) (Fig. 29.5) is made from polyethylene threads embedded in silicone. The walls of these stents are thinner than the walls of Dumon stents resulting in a better ratio of inner to outer diameter. The edges of these stents are sharper and the length of the stent changes depending on its compression state. Due to its design, a Polyflex stent can adapt slightly better to hourglass-type stenoses. The outer surface is slightly smoother, and the migration rate seems to be higher in comparison to the Dumon stent. Modified Polyflex stents with outer struts have been used successfully in recent studies. Little tungsten spots in the stent wall make them visible on chest radiographs. Polyflex stents are deployed out of a semi-rigid tube (Fig. 29.4). The skill and the training that is required to place them are comparable to the competence that is needed to insert Dumon stents.

Other CE-marked polymeric straight stents (Fig. 29.6) such as the Noppen stent (Reynders Medical Supply, Lennik, Belgium), which is made from Tygon, or Hood stents (Hood Laboratories, Pembroke, MA, USA), which are made from silicone, may be still available, but they are no longer advertised and have probably been replaced by the newly developed self-expanding metal stents.

As stated above, each stent has specific characteristics differing from those of the Dumon stent and therefore may provide a viable alternative depending on the indication.

Dumon silicone stents (Tracheobronxane®, Novatech, La Ciotat, France) are used nearly exclusively in our institution and are the most widely placed silicone stent, as such the remainder of the article will focus on this type of stent.

The most common indication is malignant airway obstruction from a bronchogenic malignancy. Malignant airway obstruction is often classified based on the airway involvement:

Other malignant indications for endobronchial stenting include endobronchial metastases from sites (e.g. oesophageal, thyroid, renal cell carcinoma, colon and melanoma) or alternatively low grade tumours (e.g. cylindromas, carcinoids).

Silicone stents are also useful as treatment for benign conditions resulting in central airway obstruction. The most common benign conditions leading to airway obstruction are post-intubation or post-tracheostomy stenosis, post-anastomosis stenoses following sleeve resection, bronchial re-implantation, lung transplantation and tracheobronchomalacia.