Chapter 40: Course and Treatment of Chronic Obstructive Pulmonary Disease

INTRODUCTION

In past decades, the treatment of chronic obstructive pulmonary disease (COPD) has been approached by many physicians and patients alike with a nihilistic attitude, assuming that the disease was progressive, incurable, and untreatable. More recently, as our understanding of the clinical epidemiology and value of therapy of COPD has improved, this attitude has changed. Physicians have come to approach COPD in the same way as other chronic diseases with goals of improving quality of life, functional capacity, and prolonged survival. With a comprehensive approach to treatment, COPD is compatible with prolonged survival, good quality of life, and independent functional status for many who have this illness. The purpose of this chapter is to summarize the current understanding of the course of COPD and best approaches to treatment.

OVERVIEW OF COPD

COPD is a disorder that is characterized by slow emptying of the lung during a forced expiration. In practice, this is measured as the forced expiratory volume in 1 second/forced vital capacity (FEV₁/FVC) ratio, and the arbitrary definition of airflow obstruction is generally taken to be an FEV₁/FVC ratio lower than 0.70.¹ Because the rate of emptying of the lung falls with advancing age, many elderly individuals demonstrate airflow obstruction even in the absence of a clinical diagnosis of COPD. For this reason, an alternative criterion to define airflow obstruction incorporates lower limit of normal thresholds instead of the fixed ratio criteria.² Several disorders cause chronic airflow obstruction—long-standing asthma, cystic fibrosis, bronchiectasis, bronchiolitis obliterans, lymphangioleiomyomatosis, panbronchiolitis, silicosis, Sjögren syndrome, and diffuse interstitial processes such as eosinophilic granuloma and sarcoidosis. The diagnosis of COPD is usually limited to individuals who have chronic airflow obstruction associated with tobacco smoke or some other noxious inhalant, and it is usually not difficult to distinguish it from other causes of chronic airflow obstruction. The most common disorders associated with COPD are emphysema and chronic bronchitis. Emphysema is defined anatomically by airspace enlargement due to disappearance of alveolar septae (Chapter 37). This leads to the characteristic loss of elastic recoil, which, in turn, causes slowing of airflow from the lungs, hyperinflation, and air trapping. Chronic bronchitis is characterized by chronic cough and sputum production, which is present in about one out of three people with early COPD. Chronic cough and sputum production in cigarette smokers is often, but not always, associated with chronic airflow obstruction. When chronic mucus hypersecretion is associated with airflow obstruction, it is often called chronic obstructive bronchitis. Although people with nonobstructive mucus hypersecretion (nonobstructive chronic bronchitis) have a greater risk for acute respiratory illness, most such individuals will not progress to airflow limitation, and therefore, the term “pre-COPD” should be avoided.³ It is unknown whether maintenance treatment of nonobstructive chronic bronchitis is beneficial. The anatomic correlates of chronic bronchitis are mucus gland hyperplasia and goblet cell metaplasia in large- and medium-sized airways.⁴ Patients with ...