Definition of Chronic Obstructive Pulmonary Disease (COPD)

Park, Sung Soo

Abstract

COPD(chronic obstructive pulmonary disease) is a disease state characterized by airflow limitation that is not fully reversible. The airflow limitation is usually both progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases, the most common of which worldwide is tobacco smoke. The characteristic symptoms of COPD are cough, sputum production, and dyspnea upon exertion. COPD is not only a disease of the lungs but is also a systemic inflammatory disorder. Muscular weakness, increased risk for artherosclerotic vascular disease, depression, osteoporosis, and abnormalities in fluids and electrolyte balance may all be consequences of COPD. The staging of COPD is based on airway limitation as measured by spirometry, which is essential for diagnosis and provides a useful description of the severity of patholoical changes in COPD. Specific FEV(1) cut-points (e.g., FEV(1) < 80% predicted) are used for purposes of simplicity: these cut points have not been clinically validated. The current GOLD and ATS/ERS definition for airflow limitation is an FEV(1):FVC ratio of < 70%. The GOLD and ATS/ERS criteria classify COPD into four stages: stage 1 (FEV(1) > or = 80% predicted), stage 2 (FEV(1) 50 to < 80% predicted), stage 3 (FEV(1) 30 to < 50% predicted), and stage 4 (FEV(1) < 30% predicted). In addition, an "at risk" stage consists of patients with chronic respiratory symptoms(cough, sputum, or dyspnea) and normal lung function. COPD can coexist with asthma, the other major chronic obstuctive airway disease characterized by an underlying airway inflammation. However, the inflammation characteristic of COPD is distinct from that of asthma. Pulmonary tuberculosis may affect lung function and symptomatology and, in areas where tuberculosis is prevalent, can lead to confusion in the diagnosis of COPD. Some of these factors including fat-free body mass, functional status, exercise capability, respiratory symptoms other than cough or sputum, depression, and heart failure are clearly important both clinically and epidemiologically and need to be considered in the evaluation of patients.