To confirm the long-term efficacy and safety of Bronchial Thermoplasty (BT) at 10 years follow-up or beyond in subjects previously enrolled in any of the following Boston Scientific-sponsored, controlled pre-approval studies: AIR, RISA and AIR2.

Compare rates of severe asthma exacerbations of subjects during the first and fifth year after BT treatment with the proportion of subjects who experience severe asthma exacerbations during the 12 months period prior to enrollment.

Compare baseline HRCT scans from subjects from the AIR2 study that enroll in BT 10+ study to examine if there are any clinically significant post-treatment respiratory changes following BT defined as bronchiectasis or bronchial stenosis.

Inclusion Criteria

• Subjects previously enrolled in AIR, RISA or AIR2
• Subjects who received active BT treatment and had last BT treatment at least 10 years and 6 weeks prior to enrollment
• Control/Sham subjects with at least 10 years of long-term follow-up from index date plus 6 weeks
• Subject is able to read, understand and sign a written Informed Consent to participate in the Study and able to comply with the study requirements

Exclusion Criteria:

• Severe asthma exacerbation or chest infection in the past 4 weeks. Subject entry into this study should be delayed until free from severe asthma exacerbation or chest infection for a minimum of 4 weeks.

Subjects that participated in one one or more of the prior studies (AIR, RISA, or AIR2) will be invited to participate in this study.