97: Overview of Chronic Obstructive Pulmonary Disease

Introduction

Chronic obstructive pulmonary disease (COPD) is defined by the Global Initiative for Chronic Obstructive Lung Disease (GOLD)¹ as persistent, usually progressive airflow limitation associated with an enhanced inflammatory response, generally in response to noxious stimuli, such as cigarette smoking. COPD is one of the few major diseases with a rising burden; it is now the third leading cause of death in the United States.² Worldwide, an increasing prevalence of cigarette smoking, other exposures such as to biomass fuel, a reduction in other causes of early mortality, and an aging population are expected to lead to an increase in the global burden of COPD, and its rise from the fifth to the fourth most common cause of mortality (Fig. 97-1).³

COPD is a common comorbid condition in patients presenting for thoracic surgical evaluation, in large part due to shared risk factors of age and cigarette smoking. In addition, increasing evidence suggests that COPD itself may be an independent risk factor for lung cancer⁴ and cardiovascular disease.^5,6 COPD is commonly underdiagnosed.⁷ The presence of COPD has substantial impact on thoracic surgical outcomes.^8,9

This chapter reviews some of the diagnostic and management considerations of COPD related to thoracic surgery, specifically:

1. Diagnosis and severity of COPD.

2. Management of stable COPD, with the goal of identifying comorbidities and optimizing pulmonary function prior to surgery.

3. Management of exacerbations.

Assessment of preoperative pulmonary risk is covered in Chapter 4. Surgical management of COPD is discussed in the ensuing Chapters 97 to 100.

Diagnosis and Severity of COPD

The diagnosis of COPD should be considered in any patient who has persistent dyspnea, chronic cough or sputum, and/or a history of exposure to risk factors for disease (generally at least 10–20 pack-years of cigarette smoking).^1,10 The GOLD definition of COPD is deliberately simple: airflow obstruction is identified by a reduced forced expiratory volume in 1 second (FEV₁) together with a reduced FEV₁ to forced vital capacity (FEV₁/FVC) ratio <0.7, and thus can be diagnosed in the appropriate setting by spirometry and bronchodilator testing. The use of the fixed ratio of FEV₁/FVC is chosen for simplicity but may lead to underdiagnosis in young patients and more conspicuously, potential overdiagnosis in elderly patients,¹¹ because of the normal decline in FEV₁/FVC with age, as demonstrated in population-based studies of healthy normal controls. Of interest, older subjects potentially misclassified as having obstruction have been shown to have worse outcomes, suggesting that using a fixed ratio is acceptable.^...