D Chronic obstructive pulmonary disease
Definition
Chronic obstructive pulmonary disease (COPD) is a “disorder characterized by abnormal tests of expiratory flow that does not change markedly over periods of several months of observation.” Asthma, chronic bronchitis, and emphysema are all common obstructive diseases characterized by decreased air flow through the tracheobronchial tree and small airways.
The terms chronic obstructive pulmonary disease and chronic obstructive lung disease are widely used as synonyms for the combination of chronic bronchitis and emphysema. Because of the prevalence of cigarette smoking, the combination of these two entities is encountered much more commonly than either of the two in its “pure” form. As a rule, the combination of chronic bronchitis and emphysema is seen in those who smoke heavily, and the disease process takes 30 years or longer to manifest. Differential diagnosis of COPD compared with other common lung disorders is described in the following table.
Differential Diagnosis of Chronic Obstructive Pulmonary Disease
| Diagnosis | Suggestive Features* |
| COPD | Onset in midlife; symptoms slowly progressive; long-term smoking history; dyspnea during exercise; largely irreversible airflow limitation |
| Asthma | Onset early in life (often childhood); symptoms vary from day to day; symptoms occur at night or in early morning; allergy, rhinitis, or eczema also present; family history of asthma; largely reversible airflow limitation |
| Congestive heart failure | Fine basilar crackles on auscultation; chest radiograph shows dilated heart, pulmonary edema; pulmonary function tests indicate volume restriction, not airflow limitation |
| Bronchiectasis | Large volumes of purulent sputum; commonly associated with bacterial infection; coarse crackles or clubbing on auscultation; chest radiograph or CT scan shows bronchial dilation, bronchial wall thickening |
| Tuberculosis | Onset at all ages; chest radiograph shows lung infiltrate or nodular lesions; microbiologic confirmation; high local prevalence of tuberculosis |
| Obliterative bronchiolitis | Onset at younger age, in nonsmokers; may have history of rheumatoid arthritis or fume exposure; CT scan taken on expiration shows hypodense areas |
| Diffuse panbronchiolitis | Most patients are male and nonsmokers; almost all have chronic sinusitis; chest radiograph and HRCT scan show diffuse small centrilobular nodular opacities and hyperinflation |
COPD, Chronic obstructive pulmonary disease; CT, computed tomography; HRCT, high-resolution computed tomography.
*These features tend to be characteristic of the respective diseases but do not occur in every case. For example, a person who has never smoked can develop COPD (especially in developing countries, where other risk factors may be more important than cigarette smoking); asthma can develop in adult and even elderly patients.
From Rable KF, Hurd S, Anzueto A, et al. Global strategy for the diagnosis, management, and prevention of chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2007;176:532-555.
Incidence and prevalence
COPD affects an estimated 15 to 20 million Americans and is the fifth leading cause of death in the United States, accounting for approximately 60,000 deaths each year. Chronic bronchitis and emphysema are the most common causes of COPD.
Pathophysiology
The dominant feature of the natural history of COPD is progressive air flow obstruction, as reflected by a decrease in FEV1. Three causes of decreases in FEV1 are as follows:
