<p>Bronchial thermoplasty has recently been FDA approved as a novel therapy for use on adults suffering from severe asthma. The procedure uses radiofrequency energy to heat the airways to 65°C for 10 s. This has been shown in dogs to lead to a reduction of airway smooth muscle mass and in humans to improve quality of life and asthma control. Early cellular reactions to this treatment are unclear; as well, there is limited information regarding thermal sensitivity of airway smooth muscle when exposed to extreme temperatures (50-65°C). We examined the cellular impact of bronchial thermoplasty by investigating the response of airway smooth muscle to heat by immersing bovine tracheal strips and bronchial segments in heated Krebs. We confirmed dramatically decreased functionality over the temperature range 50-60°C at 1 h and 24 h in all tissues. TUNEL analysis noted significant cell death in all tissues heated to 65°C and limited cell death in bronchial tissues treated with <55°C. Immunohistochemical analysis showed an effect of temperature on caspase 3 activation in bronchi; tracheal strips demonstrated co-localization of caspase 3 and TUNEL at 55°C but not 65°C. These data suggests that cell death of airway smooth muscle contributes to the cellular effects observed following heating to 65°C; at lower temperatures, cell death may be limited. We conclude that bronchial thermoplasty (heat treatment to 65°C for ~30 seconds) leads to a number of structural and functional changes in the airway smooth muscle, which culminate in marked loss of function and cell death.</p> / Master of Health Sciences (MSc)

Introduction: Bronchial thermoplasty (B.T.) is a therapeutic bronchoscopic procedure in which controlled thermal energy is applied to the airway wall to decrease smooth muscle mass. Immediate complications of B.T. include acute exacerbation of bronchial asthma, upper and lower respiratory tract infection, hemoptysis, among others. Our study assessed these immediate adverse events and the changes in forced expiratory volume in one second (FEV1%) measured four hours after each procedure from baseline. The study also aimed to examine the number of activations during each cycle of treatment and its correlation to the corresponding change in FEV1% from baseline. Methods: A case-series analysis of 17 patients who underwent B.T. between 2014 and 2019 was done. Demographic, clinical characteristics, including pre and post-BT FEV1% measures, and the number of activations were obtained. Results: Acute exacerbation of asthma was the commonest complication accounting for 33%, 57%, and 75% after BT1, BT2, and BT3, respectively. There was deterioration in FEV1% after each treatment phase, the most significant being in BT3. There was no correlation between the number of heat activations with the change in FEV1% from baseline. Conclusion: The number of activations in B.T. does not correlate with the immediate deterioration in FEV1%, although exacerbation of asthma is the commonest complication post-B.T.