Chronic Obstructive Pulmonary Disease (COPD) is a common disease and prevalence is increasing worldwide. It is characterized by persistent airway obstruction that is partially reversible but it is considered preventable and treatable disease now. Airflow limitation is associated with chronic and abnormal inflammatory response in the airways and the lung to noxious stimuli . Airway obstruction is defned by a reduction of expiratory airflow. Generally, forced expiratory volume in 1 s/forced volume capacity (FEV1/FVC) ratio of less than 70% after bronchodilator has been used to identify COPD patient. The use of lower limit of normal (LLN) values has been proposed to defne airflow limitation by spirometry, but current Global initiative for chronic Obstructive Lung Disease (GOLD) and American Thoracic Society/European Respiratory Society guidelines continue to recommend the fxed ratio criteria instead of an LLN for the diagnosis of COPD . Patients with COPD have shown a great deal of heterogeneity and can be classifed according to their clinical and radiologic parameters, biomarkers, lung function impairment and prognosis . Traditionally, COPD has been classifed as chronic bronchitis (CB) and emphysema. CB is defned as the presence of a chronic productive cough for 3 months in each of two consecutive years. Emphysema is defned as the destruction of alveolar walls and permanent enlargement of the airspaces distal to the terminal bronchioles. Current GOLD guidelines do not include the use of these terms in the defnition of COPD.