Cardiopulmonary Exercise Testing in Chronic Obstructive Pulmonary Disease: A Narrative Review

Chronic obstructive pulmonary disease (COPD) is characterized by airflow limitation from the narrowing of small airways and damage to lung parenchyma, resulting in exercise intolerance. Cardiopulmonary exercise testing (CPET) provides a comprehensive assessment of exercise capacity and of the integrated responses of the respiratory, cardiovascular, muscular and metabolic systems. It helps clinicians understand the mechanisms of dyspnea, informs treatment decisions and can evaluate the effectiveness of pulmonary rehabilitation and other treatments. CPET can also detect coexisting conditions, such as heart failure, myopathy or deconditioning, that worsen exercise intolerance in COPD despite treatment. Recognizing these comorbidities allows them to be investigated and treated in their own right. Because CPET is resource-intensive, it is best used selectively, as a phenotyping and problem-solving tool, and it is important that pulmonologists know when to request it and how to interpret it. In this review, the mechanisms of exercise limitation in COPD and the physiological measurements obtained during CPET are described, and the CPET patterns that distinguish ventilatory limitation from cardiac, pulmonary vascular and other causes of exercise intolerance are compared. Testing protocols, the interpretation of results in relation to bronchodilator therapy, and safety and contraindications are summarized. Developments since previous reviews and guidelines on COPD and lung cancer fitness, as well as recent evidence on ventilatory efficiency and prognosis are highlighted, with emphasis on integrative interpretation. Clinical applications are illustrated with an algorithm and a case example, and limitations, cost, barriers to implementation and future research are discussed.