title: Effect of three interventional bronchoscopic methods on tracheal stenosis and the formation of granulation tissues in dogs.
abstract: BACKGROUND
  Therapeutic approaches for tracheal stenosis caused by the formation of exuberant granulation tissues usually include electrocautery, mechanical dilation, laser therapy, argon plasma coagulation (APC), cryotherapy and stent placement. However, restenosis after stent insertion remains a significant limitation. We examined the efficacy of three different approaches, including induction of mechanical lesions, APC performed with different powers or durations and cryotherapy, to identify the method that limited the formation of granulation tissue.
  
  
  METHODS
  Twelve specially bred research mongrel dogs were divided into three groups. In group 1 (four dogs) mild (procedure 1; two dogs) or moderate (procedure 2; two dogs) damage was induced mechanically. Group 2 (six dogs) received APC at different powers or durations (procedure 3: 30 W, 1 cm/s; procedure 4: 30 W, 2 cm/s; procedure 5: 25 W, 3 cm/s). Group 3 (two dogs) received cryotherapy (procedure 6: two freeze-thaw cycles of 30 seconds). Uncovered self-expandable metallic stents were inserted in all dogs to maintain a continuous stimulus to the trachea mucosa. Dogs were monitored for 4 weeks and the relationship between granulation tissue proliferation and method used was analyzed.
  
  
  RESULTS
  In group 1, granulation tissue growth increased with more severe mechanical damage. The growth of granulation tissue in group 2 was more pronounced than in group 1, and both dogs in procedure 3 died because of severe stenosis. In this group, the formation of granulation tissue decreased with decreasing power and duration. In group 3, no obvious granulation tissue was found at week 4.
  
  
  CONCLUSIONS
  Lesions and stimuli from a foreign body (the stent) are two important factors that lead to overgrowth of granulation tissue. Thermal lesions, such as APC, seem to induce greater granulation tissue growth and cartilage damage compared with mechanical and cryotherapy lesions. Cryotherapy in combination with mechanical dilation may be a safe and effective treatment method for managing tracheal stenosis caused by the formation of granulation tissue.
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Beijing Chao-Yang Hospital, Capital Medical University, Beijing 100020, China. zhangjie6218@163.com
authors.forename: Jie
authors.initials: J
authors.lastname: Zhang
authors.forename: Ting
authors.initials: T
authors.lastname: Wang
authors.forename: Juan
authors.initials: J
authors.lastname: Wang
authors.forename: Ying-hua
authors.initials: YH
authors.lastname: Pei
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Yu-ling
authors.initials: YL
authors.lastname: Wang
authors.forename: Xia
authors.initials: X
authors.lastname: Zhang
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
mesh_terms: D000818:Animals; D001999:Bronchoscopy / Q000379:methods*; D017679:Cryotherapy; D004285:Dogs; D006097:Granulation Tissue / Q000473:pathology*; D017075:Laser Coagulation / Q000379:methods*; D015607:Stents; D014135:Tracheal Stenosis / Q000628:therapy*