Supplementary Material for: Vibration Response Imaging as a New Tool for Interventional-Bronchoscopy Outcome Assessment: A Prospective Pilot Study

Background: In many patients, the benefit of interventional bronchoscopy cannot be appropriately objectified. Objectives: We investigated a new technique, vibration response imaging (VRI), for breathing sound mapping to determine whether it could provide additional, valuable objective qualitative and quantitative information in central airway obstruction (CAO) and patient outcome following interventional bronchoscopy. Methods: VRI images from 83 patients with suspected central airway stenosis and 25 healthy volunteers were evaluated by two raters blinded to the subjects’ status. Qualitative and quantitative dynamic and static features were documented for the final assessment of images as normal or abnormal and changes after the intervention. As a secondary goal, stenosis location was also evaluated and compared to bronchoscopic findings. Treatment outcome analysis (improved vs. not improved) was performed by comparing baseline and follow-up images in 64 evaluations of interventional bronchoscopy. VRI measurements of treatment outcome were compared to standard tests, i.e. dyspnea score, pulmonary function testing (PFT, i.e. FEV₁, FVC and FEV₁/FVC), chest X-ray/computed tomography and bronchoscopy, the latter being considered the gold standard). Results: There was 95% (115/121) agreement between raters and clinical assessment in distinguishing between normal and abnormal images. The sensitivity and specificity of VRI were 97 and 88%, respectively. The accuracy of VRI in locating the pathology compared to bronchoscopy was 85% (17/20) for tracheal and 88% (51/58) for bronchial obstruction; overall accuracy was 83%. Correct detection of the affected side in bronchial obstructions was 88%. The overall accuracy of VRI in defining the outcome of interventional bronchoscopy was 84%. Conclusions: Obstruction location and procedure outcome were reliably identified according to specific patterns of lung images. VRI proved at least as good as standard tests in locating CAO and has the potential for becoming a valuable complementary tool in evaluating treatment outcome in patients with CAO. If our results are confirmed by further studies, VRI may replace PFT or imaging procedures in cases in which such tests cannot be performed or are not readily available at the time of the intervention.