title: Lung volume reduction by bronchoscopic administration of steam.
abstract: BACKGROUND
  At present, bronchoscopic approaches to lung volume reduction (LVR) create airway obstruction to achieve parenchyma collapse, avoiding many risks of surgical LVR. However, LVR by these methods is limited by temporary or incomplete collapse and/or residual atelectatic and scarred tissue volumes. Heat-induced ablation of lung tissue is currently under investigation as an alternative LVR methodology.
  
  
  OBJECTIVE
  We hypothesized that bronchoscopic steam injection can produce safe and effective LVR, and explored potential mechanisms for the effects.
  
  
  METHODS
  Steam treatments were applied bilaterally to six cranial lobe segments of large dogs. For series 1, 14 dogs received one of three target heat dose levels (1, 4, or 8 cal · ml⁻¹ segment volume), and then 3 months of follow-up including pulmonary function testing and monitoring for complications. For series 2, 12 dogs received a single target dose (4 cal · ml⁻¹) or sham, similar follow-up, and then assessment of lobar mass, volume, and blood flow. Vapor content of series 2 steam was 40% greater than for series 1 (similar heat dose) to attempt more peripheral heat delivery.
  
  
  RESULTS
  Nineteen of 20 treatment animals survived with minimal evidence of serious risks or reduced pulmonary function testing volumes, but 1 died from pneumothorax 5 days post-treatment. Postmortem processing of animals that survived as planned revealed obvious dose-dependent lobe reductions, additional evidence of risks, and blood flow reduction that occurred immediately post-treatment.
  
  
  CONCLUSIONS
  Bronchoscopic administration of steam is a potentially safe means to achieve LVR, but substantial risks are present and further research is recommended.
authors.affiliation: Veterans Affairs Puget Sound Health Care System and Seattle Institute for Biomedical and Clinical Research, Seattle, Washington, USA. mjemery@u.washington.edu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Emery
authors.forename: Randy L
authors.initials: RL
authors.lastname: Eveland
authors.forename: Kelly
authors.initials: K
authors.lastname: Eveland
authors.forename: Laurent L
authors.initials: LL
authors.lastname: Couetil
authors.forename: Jacob
authors.initials: J
authors.lastname: Hildebrandt
authors.forename: Erik R
authors.initials: ER
authors.lastname: Swenson
mesh_terms: D000818:Animals; D001921:Brain / Q000473:pathology; D001999:Bronchoscopy; D004285:Dogs; D004562:Electrocardiography; D006358:Hot Temperature / Q000627:therapeutic use; D008168:Lung / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D008279:Magnetic Resonance Imaging; D011013:Pneumonectomy / Q000009:adverse effects / Q000379:methods*; D011030:Pneumothorax / Q000209:etiology; D012129:Respiratory Function Tests; D013227:Steam / Q000009:adverse effects
chemical_list: D013227:Steam