Chronic obstructive pulmonary disease

1 What is chronic obstructive pulmonary disease (COPD)?

COPD is characterized by airflow limitation that is not fully reversible. Chronic airflow limitation results from a combination of small-airway disease and parenchymal destruction due to inflammatory processes. These inflammatory processes are often caused by exposure to noxious particles or gases.

2 How many people are affected by COPD?

COPD is the fourth leading cause of mortality and morbidity in the United States. The number of people affected by COPD worldwide continues to increase because of exposure to tobacco smoke and aging of the population. Historically the prevalence of disease was higher in men, but, with changing patterns of exposure to tobacco, women are now affected as frequently as men. Worldwide, exposure to indoor pollution from heating and cooking fuels substantially contributes to COPD in women.

3 What processes are involved in the pathogenesis of COPD?

COPD is characterized by chronic inflammation throughout the lung, with increased neutrophils, macrophages, and CD8⁺ T lymphocytes. An imbalance between proteinase-antiproteinase activity and oxidative stress also contributes to the pathogenesis of this disease. Oxidative stress and proteinase-antiproteinase imbalance can be related to a combination of factors, including the inflammation itself, environmental exposures (e.g., oxidative substances in cigarette smoke), and genetics (e.g., α₁-antitrypsin deficiency).

4 What are the major pathologic changes in COPD?

All structures of the lung are subjected to pathologic changes in COPD. In the central airways, inflammatory cells infiltrate the surface epithelium, edema is present, mucus-secreting glands are enlarged, and the number of goblet cells increases with mucus hypersecretion. In the peripheral airways (small bronchi and bronchioles with an internal diameter < 2 mm), chronic inflammation leads to repeated injury and repair of the airway wall. In emphysema, destruction of alveolar septa leads to confluence of adjacent alveoli and enlarged terminal air spaces. Vascular changes include thickening of the vessel wall with increased smooth muscle, proteoglycans, and collagen deposition.

5 How is severity graded in COPD?

The staging system should be regarded as an educational tool and a guide to management (Table 22-1).

^{Table 22-1} Classification of Copd by Severity

FEV₁ < 30% predicted or FEV₁ < 50% predicted plus chronic respiratory failure.

FEV₁, Forced expiratory volume in 1 second; FVC, forced vital capacity.

From the Global Initiative for Chronic Obstructive Lung Disease.

6 What are the benefits of smoking cessation for a patient with COPD?

Smoking cessation is the most important intervention. It is the most effective intervention to decelerate the decline in lung function characteristic of this disease. In addition to the modest improvement in forced expiratory volume in 1 second (FEV₁) seen with smoking cessation, the rate of decline in FEV₁ may be reduced, in some cases even to the rate found in healthy nonsmokers (± 30 mL/yr).

7 Why are bronchodilators used in the treatment of COPD?

Bronchodilators treat airway obstruction in patients with COPD. By reducing bronchomotor tone, they decrease airway resistance, which can improve airflow. This will improve emptying of the lungs and tends to reduce dynamic hyperinflation during rest and exercise and thus improve exercise performance. Spirometric changes after bronchodilator therapy may be minimal, despite significant clinical benefit, as quantified by changes in quality-of-life measures and exercise tolerance (e.g., 6-minute walk).

8 Which bronchodilators should be used in the treatment of COPD?

9 Are inhaled corticosteroids beneficial in COPD?

Although regular use of inhaled corticosteroids does not prevent loss of lung function in patients with COPD, inhaled corticosteroids in combination with long-acting bronchodilators are recommended for patients with severe disease (FEV₁ < 50% predicted) and recurrent exacerbations. Data indicate that inhaled corticosteroids in combination with long-acting bronchodilators decrease the risk of exacerbations in patients with COPD. However, treatment with inhaled corticosteroids alone may increase the risk of pneumonia and does not reduce mortality.

10 What other pharmacologic treatments may benefit patients with COPD?