Chronic obstructive pulmonary disease (COPD) is a heterogeneous disease characterized by persistent respiratory symptoms and airflow limitation due to airway and alveolar abnormalities. The causative agent is usually significant exposure to noxious particles or gases and influenced by host factors, including abnormal lung development.1 COPD includes a spectrum of pathology that involves damage to the lung parenchyma (emphysema) and abnormalities of the tracheobronchial tree (bronchitis). The manifestation of the disease varies greatly, and despite the knowledge acquired in the past 300 years, our understanding of factors that influence disease phenotypes remains incomplete. In the 16th and 17th centuries, we had the earliest descriptions of COPD, with the description of emphysematous lungs as “voluminous lungs.”2 Later, chronic bronchitis and other features were identified. While different clinical and biologic phenotypes exist, airflow obstruction characterized using spirometry is the hallmark.
Spirometry is essential in the diagnosis and is beneficial for prognostication and monitoring treatment outcomes. The most accepted criteria for airflow obstruction by spirometry is a reduction of the post-bronchodilator FEV1/FVC ratio below 0.7. While the 0.7 cutoff value for the FEV1/FVC ratio may underrecognize patients in the early stages and may overdiagnose disease in healthy middle-aged and older individuals, it has been the most accepted because it balances disease detection sensitivity and specificity.3–6 Historically, further classification of severity was based strictly on airflow limitation. Over the past decade, guidelines have evolved to incorporate a multimodality assessment of symptom burden and exacerbation risk (Fig. 38-1). Additionally, there has been an interest in going beyond symptom burden (dyspnea and history of exacerbations) to incorporate the different chest imaging patterns.7 Chapter 40 comments further about risk stratification. There is increasing evidence that current and former smokers can have parenchymal and airway abnormalities and can have respiratory symptoms and exacerbation-like events, even in the absence of airflow limitation. At present, these patients are not included in COPD management guidelines.1,8,9
COPD Assessment tool from GOLD guidelines highlights the importance of consideration of symptoms and exacerbation frequency in assessing COPD severity. (Reproduced with permission from Pocket Guide to COPD Diagnosis, Management, and Prevention. A Guide for Health Care Professionals. 2020 Global Initiative for Chronic Obstructive Lung Disease.)
COPD is a significant health problem affecting more than 400 million people worldwide. In 1990, COPD was the sixth most common cause of disease worldwide but now ranks as the third leading cause of death, according to the Global Burden of Disease Study, after cardiovascular disease and stroke.10 The impact of respiratory diseases, and specifically COPD, is wide-reaching as it affects countries at all levels of development (Fig. 38-2). The World Economic Forum estimates that the global costs of COPD will reach U.S. $50 trillion annually by ...