ABSTRACT
The term chronic obstructive pulmonary disease (COPD) is used to describe a collection of chronic disabling lung diseases. The American Thoracic Society defines COPD as
a disease state characterized by the presence of air flow obstruction due to chronic bronchitis or emphysema. The air flow obstruction is generally progressive, may be accompanied by airway hyperreactivity and may be partially reversible
(American Thoracic Society, 1995)
Chronic bronchitis, emphysema, and chronic asthma are the three diseases that contribute to the diagnosis of COPD. These diseases are similar because they all are disorders of expiration associated with obstruction of air flow out of inflated lungs. Chronic bronchitis, emphysema, and asthma differ in the nature of the airway obstruction. However, it is most common for patients to have components of more than one of these diseases.
