Classification of Pulmonary Disease

Obstructive airway diseases are characterized by abnormal expiratory gas flow rates. The airflow limitation can be structural or functional. The mechanism of hypoxemia in obstructive disease is primarily through regional mismatching of ventilation and perfusion (

1. Chronic obstructive pulmonary disease (COPD) is a slowly progressive obstructive lung disease involving the airways and/or pulmonary parenchyma, resulting in a gradual loss of lung function. COPD doubles the risk of POPCs and is associated with increased postoperative cardiac and renal complications. It is generally classified as being attributable to either emphysema (“pink puffer”) or chronic bronchitis (“blue bloater”). Although these often coexist, below they are considered as separate entities.
   1. Emphysema is due to abnormal permanent enlargement of the airspaces distal to the terminal bronchioles accompanied by destructive changes of the alveolar wall. This leads to loss of the normal elastic recoil of the lung with subsequent premature airway closure at higher than normal lung volumes during exhalation.
   2. Chronic bronchitis is defined as the presence of productive cough for at least 3 months in each of 2 successive years in a person in whom the excessive secretions are not due to other diseases. The most common precipitant is cigarette smoking.
2. Asthma is a complex and heterogeneous syndrome characterized by variable airflow obstruction, airway inflammation, and increased airway responsiveness to a variety of stimuli that include exercise, cooling, drying and/or instrumentation of the airways, infection, medications, and occupational exposure.
3. Cystic fibrosis (CF) involves the secretion of highly viscous mucus. This results in airway obstruction, fibrosis, chronic pulmonary infection, and cachexia. Late changes include pneumothorax and bronchiectasis with hemoptysis, hypoxemia, carbon dioxide retention, and respiratory failure.