Chronic obstructive pulmonary disease (COPD) is one of the most common non-communicable disease, the leading causes of death and disability in poor & middle income nations like Bangladesh. It is a common lung disease caused by abnormalities in the airways (bronchitis, bronchiolitis) and/or alveoli (emphysema) that produce persistent, often progressive, airflow obstruction1. COPD is a common cause of global morbidity and mortality. The global prevalence of COPD about 12.0% of the general population and currently ranks as the 3rd cause of mortality in the world (responsible for 3 million deaths). The incidence of COPD is expected to rise and by 2060, it is estimated that there may be over 5.4 million deaths annually from COPD3. In males and females prevalence and mortality of COPD are similar4. According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria the prevalence of COPD in Bangladesh was estimated around 12.5%5. Across the world, cigarette smoking is the most commonly encountered risk factor for COPD. Cigarette smokers have a higher prevalence of respiratory symptoms and lung function abnormalities and a greater COPD mortality rate than non-smokers6. Outdoor air pollutions, indoor air pollutions from biomass fuel burning are some of the known factors that contribute to the high prevalence of COPD in Bangladesh5,7. About 15.0-20.0% of COPD cases are due to occupational exposures to pollutants at the workplace8. Another types of tobacco e.g., pipe, cigar, water pipe and marijuana are also risk factors for COPD. Passive exposure to cigarette smoke may also contribute to COPD9. Other risk factors such as respiratory infections, poor nutritional status, chronic asthma, impaired lung growth, poor socio-economic status and genetic factors are also important for disease development10,11,12. Airflow limitation is a major physiologic change in COPD, can result from small airway disease and/or emphysema. An increased number of goblet cells and an enlargement of mucus secreting glands in the larger airways contribute to enhanced secretion of airway mucus that manifests as chronic bronchitis. Loss of elastic tissue surrounding the smaller airways, accompanied by inflammation and fibrosis in the airway wall and mucus accumulation within the airway lumen, results in airflow limitation, further increased by enhanced cholinergic tone.