COPD is defined as a heterogeneous lung condition marked by persistent respiratory symptoms such as dyspnea, cough, and sputum production, caused by abnormalities in the airways that cause airflow obstruction.

Smoking is a primary risk factor for COPD, with over 80% of patients having a history of it. Patients typically experience progressive dyspnea or labored breathing, frequent coughing, and recurrent pulmonary infections. Many eventually succumb to respiratory failure, characterized by insufficient ventilation, respiratory acidosis, and hypoxemia.

Emphysema, a common underlying cause of COPD, involves permanent enlargement of the alveoli coupled with the destruction of their walls, leading to a loss of lung elasticity. This condition requires significant energy for breathing, often resulting in easy fatigability in affected patients. Additionally, trapped air in the alveoli causes a "barrel chest" and flattened diaphragm. Emphysema can also increase the pressure inside pulmonary capillaries, causing the right ventricle to overwork and enlarge.

On the other hand, chronic bronchitis is characterized by the regular production of sputum for three or more months for two consecutive years. This obstructs airways, impairs lung ventilation and gas exchange, and increases the risk of pulmonary infections. Smoking and environmental pollution are key risk factors.

Treatment for COPD typically involves inhaled bronchodilators and corticosteroids. Severe dyspnea and hypoxia may necessitate oxygen use but should be administered with care. Despite these challenges, understanding and managing COPD can significantly improve patients' quality of life.