Bronchial wall thickness assessed by optical coherence tomography (OCT) before and after bronchial thermoplasty (BT)

Abstract

Background: BT is a novel bronchoscopic treatment for severe asthma that is based on radiofrequent energy delivery to ∼3-10mm airways that aims to reduce airway smooth muscle. Specific (imaging) parameters assessing the effect of BT are lacking. High-resolution imaging by real-time OCT is a promising tool to detect changes in airway wall dimensions pre- and post-BT. Aim: To assess pre- and post-BT bronchial wall characteristics and thickness in severe asthma patients. Methods: 3 severe asthma patients of the TASMA study underwent BT. Pre and post BT, OCT imaging was performed with a St. Jude Dragonfly catheter in the right lower lobe bronchi and untreated right middle bronchus (RML). At 3-5 mm lumen diameter 3 OCT images per airway were analysed. The airway wall thickness in percentage of total airway area (WA%) was measured. OCT findings 3 weeks before, directly and 6-10 weeks after BT treatment were compared. Results: Separate airway wall layers could be identified and measured. Directly after BT the airway wall showed specific changes in airway wall structure including disruption of (sub)epithelial layer(s). 6-10 weeks after BT wall thickness percentage measured by OCT significantly decreased (WA % 60.35 ± 3.8 vs 42.4 ± 5.0 for pre and post BT respectively; p<0.001 (n=4). In the non-BT treated RML no significant differences in WA% could be detected pre- and post-BT. Conclusions: OCT imaging is capable of identifying and quantifying airway wall layers and dimensions and shows a significant decrease in airway wall thickness after BT. More data are needed. Implications: Airway imaging by OCT might qualify as an effect/ screening tool for Bronchial Thermoplasty.