Several problems are encountered when defining COPD. The first relates to the term chronic obstructive pulmonary disease because this is not truly a disease but a constellation of diseases. According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) program, COPD is defined as a disease characterized by airflow limitation that is not fully reversible (Pauwels et al 2001). The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases. Traditionally, COPD has been divided into several pathophysiologic entities, each sharing the common physiologic features of airflow obstruction and abnormal inflammatory response. These groups include chronic bronchitis, emphysema, asthma, and bronchiectasis (McCrory et al 2001). The GOLD program standardizes the term COPD by incorporating each entity into the diagnosis of COPD. Additionally, clinicians may experience difficulty in differentiating COPD from asthma, particularly the syndrome of poorly reversible airway obstruction in older patients with chronic asthma (D’Alonzo 2004).