What is Chronic Obstructive Pulmonary Disease (COPD)?

Definition of Chronic Obstructive Pulmonary Disease (COPD)

Chronic obstructive pulmonary disease (COPD) is a common, preventable, and treatable disease characterized by persistent respiratory symptoms and airflow limitation due to airway and/or alveolar abnormalities, usually caused by significant exposure to noxious particles or gases. 1

Key Characteristics of COPD

• COPD is characterized by airflow obstruction that is usually progressive, not fully reversible, and does not change markedly over several months 1
• The airflow limitation is defined by a reduced FEV1 (forced expiratory volume in 1 second) and a reduced FEV1/FVC ratio (forced vital capacity), such that FEV1 is less than 80% predicted and FEV1/FVC is less than 0.7 1
• The airflow obstruction results from a combination of airway disease and parenchymal damage (emphysema) 1
• The damage is caused by chronic inflammation that differs from that seen in asthma and is usually the result of tobacco smoke exposure 1
• COPD may be punctuated by acute worsening of respiratory symptoms, called exacerbations 1

Clinical Manifestations

• Dyspnea, cough, and/or sputum production are the most frequent symptoms of COPD 1
• Symptoms are commonly underreported by patients 1
• Significant airflow obstruction may be present before the individual becomes aware of it 1
• COPD produces symptoms, disability, and impaired quality of life which may respond to pharmacological and other therapies that have limited or no impact on the airflow obstruction 1
• Air trapping, a hallmark of COPD, contributes to dyspnea, especially during exertion 2

Risk Factors

• Tobacco smoking is the main risk factor for COPD 1
• Environmental exposures such as biomass fuel exposure and air pollution may contribute to COPD development 1
• Occupational exposures are important risk factors after tobacco smoking 1
• Host factors (genetic abnormalities, abnormal lung development, and accelerated aging) predispose individuals to develop COPD 1
• Alpha-1 antitrypsin deficiency is a rare but important genetic risk factor 3

Pathophysiology

• The airflow limitation in COPD is due to a combination of small airway disease (obstructive bronchiolitis) and parenchymal destruction (emphysema) 1
• Small airway abnormalities contribute to airflow limitation by narrowing and obliterating the lumen, increasing resistance 4
• Parenchymal destruction contributes to airflow limitation by reducing the elastic recoil of the lung and destroying alveolar attachments 4
• Chronic inflammation leads to structural changes, narrowing of small airways, and destruction of lung parenchyma 4

Diagnosis and Assessment

• There is no single diagnostic test for COPD; diagnosis relies on clinical judgment based on history, physical examination, and confirmation of airflow obstruction using spirometry 1
• Spirometry is required to make the diagnosis; a post-bronchodilator FEV1/FVC ratio less than 0.7 confirms the presence of airflow limitation that is not fully reversible 1
• COPD is frequently underdiagnosed and undertreated 3
• Any patient presenting with cough, sputum production, or dyspnea should be assessed by standardized spirometry 3

Comorbidities and Systemic Effects

• In most patients, COPD is associated with significant concomitant chronic diseases, which increase morbidity and mortality 1
• COPD has substantial systemic consequences beyond the lungs, including cardiovascular disease, skeletal muscle dysfunction, and metabolic syndrome 3

Disease Progression and Prognosis

• Continued exposure to noxious agents promotes a more rapid decline in lung function and increases the risk for repeated exacerbations 3
• Without major preventive efforts, there will be an increasing proportion of end-stage patients requiring long-term oxygen therapy and assisted ventilation 3
• Smoking prevention and cessation are the most important measures to counteract the COPD epidemic 3

COPD is now the preferred term for conditions in patients with airflow obstruction who were previously diagnosed as having chronic bronchitis or emphysema 1. The disease represents a significant public health challenge as the third leading cause of death in the United States 5.