title: Clinical and laboratory evaluation of a new thin-walled self-expanding tracheobronchial silicone stent: progress and pitfalls.
abstract: BACKGROUND
  Although widely established in the management of malignant airway lesions, currently available tracheobronchial prostheses made of silicone have their drawbacks resulting from rigidity and wall thickness. Therefore we present clinical follow-up data obtained with a novel thin-walled expandable prototype silicone airway stent (Polyflex stent, Willy Rüsch AG, Kernen, Germany) in 19 patients.
  
  
  METHODS
  Seventeen of 19 patients had tracheobronchial complications of infiltrating cancer: five had respiratory-digestive fistulas, 14 had mixed-type obstructions (mucosal infiltration plus extrinsic compression), and two had diffuse tracheal hemorrhages from the tumor surface (three patients had more than one complication). Two of 19 patients had benign postintubation stricture and malacia. Overall, 33 stents were implanted either simultaneously or in a consecutive manner. Scanning electron microscopy was performed both on prototype stents and on other available silicone stents for comparison.
  
  
  RESULTS
  The treatment improved the patients' clinical condition substantially. The mechanical properties of the new prosthesis were excellent. Important stent-associated side effects were early mucus retention (n = 7), infolding of the inner silicone layer (n = 2), and stent dislodgment (n = 2). As of February 1997, 10 patients have died of causes unrelated to stent placement. Seven patients with malignant airway disease are still alive from 2 weeks up to 7 months after initial treatment. Scanning electron microscopy of explanted and unused prototypes suggested that an extremely ragged luminal microstructure may contribute to the firm adhesion of secretory material and that technical smoothing of the surface avoids such complications.
  
  
  CONCLUSIONS
  The novel self-expandable silicone airway stent may be a promising addition to commonly used stent types. Short-term and medium-term management of fistulas, tumor surface bleeding, and strictures (malignant and benign) is satisfactory. Scanning electron microscopy of stents provides information on peculiar features of microstructure and material that may be of use in clinical research and technical innovation.
authors.affiliation: Third Department of Internal Medicine, University of Cologne, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Wassermann
authors.forename: A
authors.initials: A
authors.lastname: Koch
authors.forename: J
authors.initials: J
authors.lastname: Müller-Ehmsen
authors.forename: M
authors.initials: M
authors.lastname: Reuter
authors.forename: O
authors.initials: O
authors.lastname: Michel
authors.forename: H E
authors.initials: HE
authors.lastname: Eckel
mesh_terms: D000328:Adult; D000368:Aged; D001982:Bronchial Diseases / Q000209:etiology / Q000628:therapy*; D003251:Constriction, Pathologic / Q000209:etiology / Q000628:therapy; D004867:Equipment Design; D004938:Esophageal Neoplasms / Q000150:complications; D005260:Female; D006801:Humans; D007412:Intestinal Fistula / Q000209:etiology / Q000628:therapy*; D008175:Lung Neoplasms / Q000150:complications; D008297:Male; D008855:Microscopy, Electron, Scanning; D008875:Middle Aged; D016156:Respiratory Tract Fistula / Q000628:therapy*; D012828:Silicones; D015607:Stents; D014135:Tracheal Stenosis / Q000209:etiology / Q000628:therapy*
chemical_list: D012828:Silicones