Chronic obstructive pulmonary disease (COPD) is a common disease , and characterized by
progressive development of airflow limitation. Small airway disease (obstructive bronchitis)
and lung parenchyma damage (emphysema) are the main mechanisms of chronic airflow limitation.
Research shows that small airway resistance increased by 4-40 times in COPD patients, and
become the main part of the airflow obstruction. Impulse oscillation system (IOS) is able to
measure the total airway resistance, the central airway resistance and the peripheral airway
resistance, which is now widely used to assess small airway function in COPD patients. While
High resolution CT (HRCT) is easy to operate and its images are intuitive. Meanwhile it can
measure the proportion of emphysema, the airway diameter and the thickness of airway wall.
Both of these two tests have great significance in small airway evaluation. Chronic
obstructive pulmonary disease with acute exacerbation (AECOPD) is an acute onset process,
which is characterized by the aggravation of respiratory symptoms and deterioration of
pulmonary function. However, the structural and functional changes of small airway in AECOPD
are not clear. Inhalation drugs are the main treatment for stable COPD , and inhaled
corticosteroid（ICS）+long-acting beta2-agonist（LABA） are used to treat patients with severe
and severe airflow limitation. The particles in traditional inhalation drugs are larger and
mainly deposited in large airways, and their effects on small airway function are relatively
small.
The objectives of the investigators study are COPD patients. The study is divided into two
parts, that is the part of AECOPD patients and the part of stable patients . Patients with
AECOPD are arranged to take HRCT and IOS test to assess the small airway changes.Patients
with stable COPD are randomized to take either beclomethasone / formoterol (particle diameter
for 1.4-1.5um) or budesonide / formoterol (3.2um) for three months. The structure and
function changes of small airway in different stage will be evaluated and the efficacy of
these two drugs is to be compared. This study is expected to highlight the investigators
understanding on the role of small airways in COPD, and provide a guideline to clinical
standardized treatment as well as evaluation of patients' conditions.