Pulmonary stents

Abstract

SummaryThe term ‘stent’ can be defined as a conduit to establish continuity, or a channel across a narrowed area. Stents have recently been devised for the tracheobronchial (TB) tree. Indications for pulmonary stents include benign or malignant TB obstruction and tracheobronchomalacia (TBM). There are two main types of stents, silicone or tube stents and metallic stents. The latter can be balloon-expandable or self-expandable and self-expandable stents can be either uncovered or covered. Montgomery silicone T-tubes are the model for present-day silicone stents, of which the Dumon stent is the most widely used. Silicone stents are easier to insert and remove than metallic stents. Their disadvantages include granulation tissue formation, migration and impaired mucociliary function, leading to mucoid impaction. Metallic stents are made of alloys of chromium, cobalt, molybdenum, stainless steel or tantalum. Neo-epithelialisation occurs over the stent in 3–6 weeks, with incorporation of the stent into the airway wall. Wallstents are the most commonly-used metallic stents. The elastic and plastic properties of metallic stents allow them to adapt to the contours of tortuous airways. Tumour overgrowth through the wire mesh is a disadvantage of metallic stents. The search for an ideal stent that can be tailored to individual patient needs, which is made of inert material with minimal airway inflammation; easy to insert and remove; self-expandable; sufficiently elastic to withstand airway pressures; pliable to mould to airway contours; free of complications, such as migration, granuloma formation and accumulation of secretions; and cost-effective, remains unfulfilled. Expertise of the person performing the procedure is an important aspect of stent selection. Endobronchial stenting is acquiring a multi-disciplinary approach and these procedures may have the best outcome if performed in tertiary centres, allowing comprehensive care, as well as a scientific approach. This should eventually lead to the emergence of an ideal stent.