P13 Bronchial thermoplasty maintains a long-term reduction in peripheral blood eosinophils in severe asthma

Introduction Severe Asthma, characterised by persistent symptoms despite maximal medical therapy, represents 5% of asthma cases. Bronchial Thermoplasty (BT) is a novel therapy where radiofrequency thermal energy is applied to airways distal to the main-stem bronchi, permanently reducing airway smooth muscle mass. It is unknown whether treatment of smooth muscle hypertrophy impacts persistently upon systemic signs of allergic inflammation. Peripheral blood eosinophils (PBEs) are a marker of inflammation in asthma. We have previously shown that BT modifies signs of Th 2 inflammation as measured by PBEs and therefore wanted to ascertain whether this persisted over time? Method We reviewed the 13 consecutive Severe Asthma cases treated with BT who were included in the initial analysis. Serial PBEs measured up to 3 years post BT were compared to those in the year proceeding BT. Blood eosinophil levels taken peri-procedure were excluded from analysis due to escalated steroid therapy at this time. Results figure 1 demonstrates the absolute values of PBE for each patient during the 3 time periods (year before BT, Year immediately after BT and third year post BT). The group mean in year 3 has remained suppressed compared to baseline (year 3; 0.17 baseline p=0.0035). Conclusion Previous findings showed that Severe Asthma patients undergoing BT had a significant reduction in average peripheral blood eosinophil levels from baseline. The data shows overall the group of 13 patients continue to remain eosinophil supressed supporting the possibility of a long term eosinophil suppressive impact of BT.