Definition, differentiation, and classification of COPD.

The term "COPD" covers a spectrum of diseases with a common denominator, obstruction to airflow on expiration. Chronic asthma, chronic bronchitis, and pulmonary emphysema are the most prevalent conditions. The signs and symptoms of COPD are similar in all entities. Differential diagnosis may be difficult. Early detection of COPD is important, and tests are available for this purpose. For therapeutic and prognostic reasons it is also important to differentiate, wherever possible, which disease entity is predominant in a particular person. This can be done to a high degree by correlating clinical, radiologic, and physiologic findings. The radiologic manifestations of COPD are multiple, varied, and in many instances nonspecific. The primary radiologic feature in COPD is lung hyperinflation. In advanced disease, radiologic changes are diagnostic and correlate well with physiologic and clinical findings. Frequently, however, the chest film is normal even when clinical and physiologic manifestations indicate advanced disease.