Unravelling Targets of Therapy in Bronchial Thermoplasty in Severe Asthma

This study has a two-fold purpose: 1. to unravel the targets of BT in severe asthma (how does it work?) which is fundamental for better patient selection (who benefits most?) and further improvement of BT technology and novel asthma therapy development (how to treat better?). These objectives can only be achieved by linking patient-reported outcomes to airway structure/function, which is the principal aim of the study proposed. 2. to investigate clinical outcome analyses