Study participants
We recruited 167 study participants, aged 18 years or greater, from out-patient clinics of The First Affiliated Hospital of Guangzhou Medical University between April 2014 and December 2019. First, we studied 104 asthmatic patients and 31 control subjects to compare the airway structural characteristics by using EB-OCT (Study 1). Thereafter, 32 patients with moderate-to-severe asthma participated in Study 2 to assess the bronchodilator responses with EB-OCT. The diagnosis of asthma was made by respiratory physician based on the history of respiratory symptoms and variable expiratory airflow limitation. Asthma severity was graded according to Global Initiative for Asthma 12. Overall, 30.8% (32/104) patients in Study 1 and 31.2% (10/32) in Study 2 were well controlled, while 69.2% in Study 1 and 68.8% in Study 2 remained partly controlled. All asthmatic patients were non-smokers or had smoked for less than 5 pack-years. We excluded patients with asthma attacks or acute respiratory tract infection within 4 weeks and cardiopulmonary diseases. Control subjects, who underwent bronchoscopy for upper lobe peripheral nodules, were otherwise never-smokers with normal lung function and free from respiratory diseases with symptoms.
This study was approved by the Ethics Committee of The First Affiliated Hospital of Guangzhou Medical University (Medical Ethics [Year 2014] No. 51 and [Year 2019] No. K09). All subjects gave written informed consent.