Airway structural abnormalities were more prominent in patients with greater asthma severity
In Study 1, the Ai/BSA and Aw% from the 3rd to 9th generation of bronchi did not differ significantly from those in the RB8 to RB9 segment (all P >0.05,Table E3 ). In medium-sized airways (the 3rd-6th generation), both patients with moderate and severe asthma had significantly lower Ai/BSA than control subjects and patients with mild asthma (bothP <0.05, Figure 1 ); however, the Ai/BSA in control subjects and patients with mild asthma were comparable (bothP >0.05). Compared with those with moderate asthma, patients with severe asthma yielded markedly smaller caliber from the 5th to 6th generation of bronchi (P =0.018). Furthermore, significantly greater Aw% from the 3rd to 6th generation of bronchi was seen in both patients with moderate and severe asthma than in control subjects and patients with mild asthma (all P <0.05). Severe asthma was associated with greater Aw% from the 5th to 6th generation of bronchi compared with moderate asthma (all P <0.001). Aw% from the 3rd to 6th generation of bronchi was notably greater in patients with mild asthma than in control subjects (P <0.05).
In small airways (the 7th-9thgeneration), both patients with moderate and severe asthma presented with significantly smaller Ai/BSA and greater Aw% compared with patients with mild asthma and control subjects (allP <0.05, Figure 1 ). Severe asthma yielded markedly lower Ai/BSA and greater Aw% from the 7th to 9th generation of bronchi compared with moderate asthma (all P <0.05). Despite comparable Ai/BSA, patients with mild asthma yielded greater Aw% from the 7th to 9th generation compared with control subjects. Collectively, patients with mild asthma had developed airway remodeling (wall thickening) from the 3rd to 9th generation, even in the absence of airway luminal narrowing. More prominent structural abnormalities were associated with greater asthma severity, as evidenced by decreased airway caliber and greater wall thickness (Figure 2 ). The airway inner area of medium-sized airways (Ai/BSA3-6) correlated negatively, and the airway wall area of medium-sized airways (Aw%3-6) correlated positively with the duration of asthmatic symptoms (r=-0.306, P =0.002; r=0.282,P =0.004, respectively). However, the sputum eosinophil count did not correlate with EB-OCT parameters (all P >0.05,Table E4 and Table E5 ).