Definitions

This chapter examines the definitions, similarities and differences between asthma and chronic obstructive pulmonary disease (COPD), drawing heavily on the latest information on asthma and COPD that is included in the guidelines on the diagnosis and management of these diseases from two widely respected global initiatives, the Global Initiative for Asthma (GINA) and the Global Initiative for Chronic Obstructive Lung Disease (GOLD), as updated in 2006. Most of the definitions for asthma have emphasized the characteristics of fluctuations over time in bronchoconstriction and the reversible nature of the disease. As the pathophysiological basis of asthma became clearer, definitions began to include a statement about the pathological characteristics. Until quite recently, definitions of COPD used to include the terms "chronic bronchitis" and "emphysema." Over the past 30 years, the thinking about asthma and COPD has swung between the concept of asthma and COPD belonging to a spectrum of diseases that all cause airflow obstruction, to the concept of them as very different diseases, and most recently to them both being inflammatory diseases with important similarities and differences. Although the similarities between the diseases are striking, it is the differences in the inflammatory processes between the two diseases that define their natural histories, clinical presentations, and approaches to management.