Abstract

Rationale: Bronchial thermoplasty(BT) is a new non-pharmacological therapy for patients with severe uncontorolled asthma. Improvement of asthma-related QOL and severe exacerbation was reported as effectiveness of BT treatment, however, the change of spirometry and respiratory impedance after BT are not clear. The purpose of this study was to clarify the pulmonary function after BT including use of forced oscillation technique (FOT). Methods: Fourteen severe asthma patients were underwent three BT procedures from February 2015 to February 2017 and pulmonary function was measured before and 1 year after BT treatment. For each subject, we measured respiratory function FVC, %FVC, FEV1, %FEV1, FEV1%, V75, %V50, %V25, V50/V25 by spirometory; we mesured respiratory resistance at 5Hz (R5), at 20Hz (R20),R5-R20, respiratory reactance at 5Hz (X5), frequency of resonance (Fres), and low-frequency reactance area (ALX) by using MostGraph-01. Results: The median age was 58 years. (7 males and 7 females) The average number and time of activation were 65 and 75 minutes for each. The average of annual exacerbation number  decreased from 6.6 to 3.5 (p <0.01). Respiratory function was only a mild improvement. Of all the respiratory and forced oscillatory parameter, R5-R20 was strongly correlated toreduced number of asthma exacerbation after BT. Conclusions: Respiratory resistance of R5-R20 was associated to asthma exacerbation after BT. Further studies are required to confirm and use in clinical practice.