- patients diagnosed as AECOPD and stable COPD ( random selection by 1:1 cross over). A diagnosis of COPD was made by a clinical history, examination and spirometer (forced expiratory volume in 1st second/forced vital capacity (FEV1/FVC)ratio of <0.7). The severity of COPD was graded according to the Global Initiative for Chronic Obstructive Lung Disease guidelines.