Abstract
Background Understanding asthmatic airway structural changes
and the bronchodilator responses may help unravel targets for
intervention. However, structural abnormalities of asthmatic airways
with different disease severity and the major anatomical site of
bronchodilator responses have not been well elucidated. We aim to
evaluate the airway remodeling characteristics and the bronchodilator
responses in medium-sized and small airways of asthma.
Methods We recruited 104 asthmatic patients and 31 non-smoking
control subjects to compare the airway inner area (Ai) and airway wall
area percentage (Aw%) with endobronchial optical coherence tomography.
We also enrolled 32 patients with moderate-to-severe asthma to
dynamically assess the airway morphological changes after salbutamol
inhalation.
Results More prominent airway structural abnormalities
correlated with greater asthma severity, evidenced by the decreased Ai
and greater Aw% in medium-sized and small airways. Patients with mild
asthma yielded comparable Ai but greater Aw% than control subjects.
Salbutamol inhalation led to a rapid dilatation of both medium-sized and
small airways, the lung function improvement correlated significantly
with the increase in Ai of the medium-sized, but not small, airways at
15 min.
Conclusion Luminal narrowing and airway wall thickening of the
medium-sized and small airways are present in mild asthma and reflect
asthma severity, lending support to the use of anti-imflammatory
intervention in mild asthma. The medium-sized airways are the crucial
site of the bronchodilator responses, providing the scientific rationale
for future development of more effective delivery of inhaled medications
for asthma.
Keywords: Asthma; airway remodeling; bronchodilation; optical
coherence tomography