慢性閉塞性肺疾患（COPD）

Emphysema involves permanent enlargement of the alveoli and destruction of their walls, causing loss of lung elasticity and air trapping that creates a barrel chest. Chronic bronchitis is characterized by inflammation of the bronchial tubes leading to excessive mucus production and fibrosis in the lower respiratory passageways. Both conditions often overlap in COPD patients and impair ventilation through different mechanisms.

Air trapping in emphysema causes a flattened diaphragm and increased pressure inside pulmonary capillaries, forcing the right ventricle to overwork and enlarge. Patients experience significant fatigue because breathing consumes excessive energy. The loss of lung elasticity further impairs the ability to exhale completely, worsening respiratory function.

Chronic bronchitis causes excessive mucus production and fibrosis in the lower respiratory passageways, which obstructs airways and impairs gas exchange. Mucus buildup traps bacteria and pathogens, preventing normal clearance mechanisms. This environment increases susceptibility to frequent pulmonary infections and complications.

Smoking tobacco is the primary risk factor, with over 80% of COPD patients having a smoking history. Breathing in harmful particles and gases from air pollution also significantly contributes to disease development. These environmental exposures cause persistent airflow limitations and progressive respiratory symptoms over time.

Inhaled bronchodilators and corticosteroids are the primary medications for COPD management. These drugs help relieve airflow obstruction and reduce inflammation in the airways. Oxygen therapy is recommended for severe dyspnea and hypoxia, though it requires careful administration to avoid complications.

COPD is marked by persistent dyspnea, chronic cough, and sputum production caused by airflow limitations and airway abnormalities. Symptoms are progressive, with patients experiencing labored breathing that worsens over time. Without proper management, patients may eventually develop respiratory failure characterized by insufficient ventilation and hypoxemia.

COPD is defined as a heterogeneous lung condition because it encompasses multiple underlying pathologies, primarily emphysema and chronic bronchitis, which often coexist in patients. Each condition causes airflow obstruction through different mechanisms: emphysema through alveolar destruction and chronic bronchitis through airway inflammation and mucus production. This diversity requires individualized treatment approaches.